Cytotaxonomy of the pocket mice, genus Peroganthus (Rodenta: Heteromyidae)
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Authors Patton, James L.
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Link to Item http://hdl.handle.net/10150/318410 CYTOTAXONOMY OF THE POCKET MICE, GENUS PEROGNATHUS (RODENTIAs HETEROMYIDAE)
by James Lloyd Patton
A Thesis Submitted to the Faculty of the DEPARTMENT OF ZOOLOGY x In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE In the Graduate College THE UNIVERSITY OF ARIZONA
1 9 6 5 STATEMENT BY AUTHOR
This thesis has been submitted in partial ful fillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library, • Brief quotations from this thesis are allowable without special permission^ provided that.accurate acknowledgment of source is made. Requests for per mission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship0 In all other instances» however, permission must be obtained from the author.
SIGNED; o X t d W
APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below;
;W, Bo HEED ueffle Associate Professor of Zoology ACKNOWLEDGMENTS I would like to extend my deepest gratitude to Dr. William B. Heed under whose direction this manuscript was initiated and completed. To Dr. E. Lendell Cookrum for graciously supplying equipment and space and for offering valuable suggestions, and to Dr, Wayne R. Ferris for the use of photomicrographic equipment and for help ful criticism, I give grateful appreciation. My thanks go also to Dean Willis R, Brewer, College of Pharmacy, University of Arizona, and to the American Cancer Society for making available funds used in this study. To Mr, Donald B. Sayner is given my appreciation for assistance in the preparation of this manuscript. To my fellow graduate students special acknowledgment is due, particularly to Mr. Alfred L. Gardner and Mr. Edward P. Lincoln for help in the collection and identi fication of specimens and for offering the use of their extensive knowledge of the animals under study. I am also indebted to Mr, G. Clay Mitchell for his help and companionship on collecting trips, and to Mr. John W. Wright for his editorial assistance.
ill TABLE OF CONTENTS
Page
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DISCUSSION* a obpoodeooooooooobooooooooeoobooooeoooo 32 Evolution of the Karyotype, ■ 32 Changes Affecting Individual Chromosomes.., 33 POlyS Olliy »*eeoooe6eoo909&*o»@e@@*o»0ooeo 33 Structural Changes, „e, o.»».»»»« Fusions and Exslons,-® o@Qo»o*oo*»o,o60@o4 34 Changes Affecting Sets of Chromosomes § Polyploidy eoo^cooooseooeoosooooeottooeooooed 36 Trends In Numerical Analysis of Chromosome Complements In Mammals6ee.«.e. 37 Karyologlcal Taxonomy of the Genus
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iv V TABLE OP CONTENTS— Continued
Page Chromosome Races in P. goldmani and P e ^)e^^nl^C oOOeoOOeoeQOOODOnoooyeoofrttOOSeoeoooeoe The Status of P. goldmani and P. artus.. 0. o « 52 Evolutionary Trends within the Genus JTv3X y i l L j O o o o o o o Co o e o o o o ©ccoeeoeeoooeeeoo^eooo
SUMMARY A N 3 D COHCX;USIONS o oooe ee® 0O ooeooeoooooocooooo e 5 9
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APjPlil'JO S 0 IDEOGRAMS oodoooeoooooeoooooooeaooeooeoo *^3
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A J? iP END XX Deoeeooooeocooo®e®oeoed»otiicoc*occ>o»o6 oeeooe .9^ DXXSRAXURE OX TED oeoo coo-ooceeoOdeoeeoeoc^ooooeoe ooodo. 93 LIST OP PLATES
Plate Page ■I. Representative male karyotype of Perognathus o e o e s e o » » 6 e P e e o e e e o »
pe^nii^“^3 e o 0, 0 6. 6 600 0op 6 0 0 0 60 0 00000 . 6 6 0 0 0 6 6 0. 63 IV, Representative male karyotype of Perognathus intOTmedius..op,,..,,,o«,,«,...p»©poo ©.o © © o. 64 V. Representative male karyotype of Perognathus f alla% . ©60 0. 0. 0060 06 0 Oo 000060 . O©-0O 60 ©OoO.OOO © 65 VI. Representative male karyotype of Perognathus
artUS ooo©00000.000©60060600000©06000000000. . 66 VII. Representative male karyotype of Perognathus “* 0< © © 0 0 O 0 ® 0 0 0 9 0 O © O O Q O O © 0 O 0 0® o 6 & O © © © o © 67 VIII. Representative male karyotype of
'^..©OO 006 0 0. 0 006 000600.0 0-060606. ©00 68
IX. Representative male karyotype of Perognathus ^O X.^3.13l3*y3l j© o e o e b e e e> © ® © o © o » © © © 6 9 © e 6 q e © » & e t> & e© 69. X. Representative male karyotype of Perognathus ^ e o q © © 0 © * d o ® e d © © o d p q o © d e d e s © o q q e ® e, 0 . 70
XI. Representative male karyotype of Perognathus , Paile^i,. © . O 6 O o © O © 0 6 0 ® 0 0 0 0 . 0 O' © © © © © © © © © ®. © $ © 6 71 XII. Representative male karyotype of Perognathus Ijj S P l d U S . 0 0 0 op 6 . 0 0 6 6 0 6 6 . 66. 00. 0 0*0. 0 0 0 6 0606, © 72 XIII. Representative female karyotype of Perog- nathus parvus.oe©.©©©©.©©©©.©©©.©©©©6000006,© 73 XIV. Representative male karyotype of Perognathus Bdeoodeo ooeed od eo® oeedoooedeeeqtidde 74
VI LIST OP PLATES— Continued Plate XV. Representative male karyotype of Qeoo«o.oo«oo 00.900 XVI. Representative female karyotype of i^atkus^ fnrmosuso ...o.ooooo.o.o* XVII. Representative male karyotype of LIST OP FIGURES
Figure Page
1 . Composite ideogram of the male penicillatus karyotype...... vde&eoeeooo . 79 2. Composite ideogram of the male Perognathus pjsrniri^ct karyotype...... 79 3. Composite ideogram of the male Perognathus p^erni^c^yS ■ kary o type . 80 #. Composite ideogram of the male Perognathus intermedlus karyotype.. « .. 80 5. Composite ideogram of the male Perognathus fall^^E karyotype...... ee.o e.®...« . 81 6. Composite ideogram of the male Perognathus artus karyotype . 81 7 . Composite ideogram of the male Perognathus ^ojLiBianx^^oc karyotype...... #.....«.«..» 82 8. Composite ideogram of the male Perognathus goldjmru-iS karyotype...... 82. 9. Composite ideogram of the male Perognathus goldmamikaryotype.. . 83 10. Composite ideogram of the male Perognathus goldmani-y karyotype...... 83 11. Composite ideogram of the male Perognathus ’1 karyotype...... 84 12. Composite ideogram of the male Perognathus karyotype...o*.®..*...... 84 13. Composite ideogram of the female Perognathus jjajnrus karyotype. .<1...... © • 85 14. Composite ideogram of the male Perognathus ^^npl^us^ karyotype..... a. o®...... ®. © ®.. 85
vill ix LIST OF FIGURES— Continued
Figures Page 15. Composite ideogram of the male Perognathus longimembrus karyotype. ,6. . 86
1 6 0 Composite ideogram of the female,Perognathus jc^Drmosjusi^ karyotype....o....6.0.000.9.0 oo... o 86 17. Composite ideogram of the male Llomys pu^o^tu^ karyotype.D.ooooo...... @.009.00*0*0., 8? 18. Phylogenetic chart of the genus Perognathus... * 39 19. Phylogenetic relationships between the four chromosome races of Perognathus goldmani
and Perognathus artus.00 oeeeo eeee@-. 48 20. Map showing the present range of the species Perognathus goldmani» and the localities of the four chromosome races described for this specxes....».*»....»*».< . 50 21. Map showing the present range of members of the intermedius species group9 subgenus ,9 of the genus . 57 LIST OF TABLES
Table Somatic chromosome numbers and types of . species of the genera Perognathus and. LXOmTTJS oeBQ'»eee#&ee»*e».
II. Chromosome counts of pmiclllatus. III. Chromosome counts of Perognathus Ot . e e e , 6 e ■ • **,,* o e - * e b e , , , o . b . •IV. Chromosome counts of Perognathus o 9 eoaeooeoeceeoe © e V, Chromosome counts o f 'Perognathus
. VI. Chromosome counts of Perognathus fallax. . o, , e., be,, bee e.o , e VII, Chromosome counts of Perognathus a X t U S , .oeebbbebeebe.frebbbbebeo.edbeeb
VIII. Chromosome counts of Perognathus ' oO t>©C©6Oo©e6ootoCrO©e’©O0eO6
IX. Chromosome counts of Perognathus '5 .eeeeeb.bbobebeeee.eebebbfr X. Chromosome counts of goMmanP-yd 0 o a 6 ©Q©OQOe©e© XI, Chromosome counts of Perognathus O oO « O 6© e ©0906# dO9O®0©e • x ii. Chromosome counts of Perognathus b ^ l e ^ l . ebb.bbebsbe.boebeee 9 © © a & » o e XIII, Chromosome counts of rerognaum >0 6 O <» 0 e 9 Co6©e00©0090e0»00o©030 XIV, Chromosome counts of Perognathus 0 oooe©©e©0 9©e©©©e©©W©e®©>©oee©® LIST OF TABLES— Continued
Table XV. Chromosome counts of Perognathus
^eodreodeoeotios^o^doooieoyco XVI. Chromosome counts of Perognathus
•oOOOO © S O t£» 0 Q 0 6 0 0 6 0 00 XVII„ Chromosome counts of Pero^nathus f ormosus..0..@ .6.»#ooooo&otto& XVIII0 Chromosome counts of ABSTRACT • CytOlogica! investigations demonstrate that the species9 karyotype can be used as a valid taxonomic char acter in constructing phylogenetic relationships,. It is shorn that in the 12 species of Berognathus and one species of Llomys examined that the karyotype is a population constant. In all but two species of Perog- nathus the karyotype is species specific. The occurrence of chromosome races in both P. goldmanl and P. pernlx indicates that speclation is not a static process within the genus9 but is dynamic. These races are. thought to represent an intermediate stage in the evolution of each speciesp since no evidence indicates the presence of a chromosomal polymorphism, A systematic analysis of museum specimens may necessitate the elevation of these races to ! - full species rank. Comparative analysis of karyotypes demonstrates phylogenetic relationships between members of recognized species groups and subgenera within the genus Perognathus. A phylogenetic chart and hypothesized route of dispersal from the proposed center of origin for the Imtermedius species group can be made on karyological evidence. Further information is needed from members of this.genus not examined before a phylogeny of the entire genus can be constructed, -
xii INTRODUCTION A1though the evolution of mammalian groups is a subject which has long been of interest9 it has only been comparatively recent that an attempt has been made to determine phylogenetic affinities through a study of their chromosomes. In the pasts the lack of suitable techniques for the study of mammalian material has made it virtually impossible to obtain detailed karyotypes for cytological studies. However9 with the recent development of a com paratively simple and highly successful technique for the quantitative analysis of chromosome morphology9 a new avenue has been opened to the study of the phylogenies of all vertebrate groups9 including mammals (Ford and Hamer- ton 1956), The technique has made possible the deter mination of not only the diploid numbers but also the chromosome morphology of a great variety of animals here tofore unstudied. The importance of such analyses in elucidating phylogenetic relationships has been stressed by several authors9 including Cain (1958)9 Christensen ' and Nielsen (19555s Tobias (1953)9 and Ohno9 et a^. (1964). The pocket mice of the genus Perognathus (family Heteromyidae) present an intriguing cytotaxonomic problem. Most studies of these mice have been primarily concerned with descriptive morphology9 and thus the taxonomy of the genus is well known (Osgood 19001 Hall and Kelson 1959)• However, many inconsistencies remain in the present tax onomy 9 and little or no published information is available on phylogenetic -relationships within the genus. The inconsistencies, particularly at the specific level, are due mainly to the inadequate collection of material and to the fact that many new verities of pocket mice have been described since the genus was last revised in 1900 (Osgood) Because of this, great inter- and intra-population vari ations have become apparent, causing an over-lapping of many of the key characters used by Osgood in his morpho logical approach to the taxonomy of the genus, Resultantly identification of a given specimen is often impossible with the'available taxonomic keys. This has led to many false identifications and further confusions as to the actual characteristics of the species groups within the genus. Due to availability of specimens for study and to a concentrated effort to examine the lesser known members of this genus, most of the work presented here pertains to the subgenus Chaetodlpus (see Appendix C for present accepted taxonomy of the genus)„ For comparative purposes, members of the subgenus Perognathus and of the genus Llomys the spiny pocket mice, were also examined. Through an analysis of the chromosome complements of these species, definite taxonomic relations can be shown. The findings 3 generally substantiate the classical taxonomic arrangement $ but in some cases they reveal the need for minor revisions. Since not all members of the genus have been studied, only general trends regarding evolution and phylogeny can be shown by the comparisons of the karyotypes of various species. These trends do indicate that the genus probably had a polyphyletio origin* and that modern members of the genus have a center of. origin in the central* northwest coast region of Mexico. Not only are species6 identifications possible through karyologio studies* but also the origin* center of distribution,' and.dispersal pa.tterns of this genus can be determined. The use of karyotypes as valid taxonomic characters for mammals has been well established: in Murld rodents (Matthey 1952)? in gerbils (Tobias 1956)§ in primates (Bender and Ghu 1963? Klinger, et al. 1963)8 and in Sciurid rodents (Nadler 1963$ 1964a), It is believed that through the use of.karyology* the true nature of the mammalian genetic species can be ascertained for the genus Perognatus. Members of the genus can be correctly identified* and phy- logenies can be constructed by defining the limits of these genetic species and by determining the amount of variation within each. - METHODS AND MATERIALS
Beginning in 1956, several good methods, all generally based on the colchicine-*hypotonic citrate method of Ford and Hamerton (1956)9 have been available for the study of mammalian chromosomes, both in vitro and in vivo. These techniques are generally acceptable for the study of all mammal groups, but small revisions are often needed to fit the particular physiology of a given group. This fact, coupled with the availability of equipment, has led me to prefect a very simple technique invilving the in vivo culturing of leucocytes from bone marrow. The method gives excellent results in a short time span and with the use of minimal and inexpensive equipment.' The technique is as followss 1. Inject (IP) live animals with colchicine (0.05 grams percent), 0.01 ml per gram body weight. The purpose of the colchicine is two folds it breaks down the spindle fibers preventing dividing cells from proceeding past metaphase, and it contracts and swells the chromosomes for an increased resolution of morphological detail. Col chicine is toxic so care should be made not to give an overdose. 2. After seven hours sacrifice the animal, excise out the femur and tibia, out off the epiphyses, and flush
4 . the shafts with 3 ml of 1.0 percent sodium citrate. Pipette vigorously to break up any cell clumps. 3. Incubate the resultant cell suspension at 37° C for 30 minutes. 4. After incubation, filter the suspension through two layers of cheesecloth and centrifuge at 500 RPM for 5 minutes. 5. Discard the supernatant fluid being careful to leave the button of cells undisturbed. Add 3 ml of freshly prepared Garnoy6 s fixative (3 parts absolute methanol to 1 part glacial acetic acid) and allow cells to fix in a cold box at 4° C for 30 minutes. 6. Centrifuge again at 500 RPM for 5 minutes. Wash cell button several times being careful to leave button undisturbed, 7. After final washing, pour off supernate and add about 0.7 ml of fixative. Resuspend cells through vigorous pipetting. 8. Pipette droplets of cell suspension onto chemically clean slides and Ignite the suspension immediately, follow ing the blaze-dry method of Scherz (1962), • Shake off excess water and allow slides to dry thoroughly, 9. Stain in aceto-oroein for one and a half hours. Dehydrate in three, 30 second changes of absolute methanol and mount. For each animal more than 25 good figures were scored in order to ascertain the correct diploid number. Free hand drawings were made and photographs were taken of most cells to facilitate counting. Generally„ the diploid number of each animal would vary in either direction by one or two from the modal class9 due primarily to over lapping or to extreme spreading causing a loss or gain of a chromosome. In these instances, the median figure where the majority of counts fell was chosen as the correct diploid number. In allv. qps-es, the chosen figure had a highly significant number of counts. The diploid number . of each species was then determined from analysis of such number, from each representative individual. Except for two cases, this number did not vary between individuals at the specific or subspecific levels. The exceptions will be discussed below. The sex chromosomes were identified on the basis of their lack of a homomorphic nature. In other words, all but two chromosomes in the complement could be arranged in homologous pairs. The two unpalrable chromosomes are then designated the sex chromosomes. Which of the two is the X-chromosome can be determined by observing which element occurs twice in the diploid complement of females of the same species. A number of photomicrographs were taken of individual cells of each animal analysed. . From these, enlargements were made and karyotypes were eonstrueted by cutting out the individual chromosomes and pairing them. Where possible the chromosomes were paired according to centromere position and size, but in many instances groups of four or more similar chromosomes had to be paired in an arbitrary fashion Due to the colchicine treatments the morphology-of each chromosome was easily discernible as the chromotids would be well spread showing the exact position of the centromere. Measurements were taken on chromosomes of ten representative karyotypes of each species analysed. Since these measure ments would vary for each chromosome due to differences in the stage of metaphase in which the cells were in- at the time of fixation or to differences in the amount of con traction due to colchicine treatment* a mean value was calculated for each chromosome and a representative ideogram of each species was constructed. A morphological breakdown of each species8 karyotype was accompolished by determining the arm-ratio for each chromosome. Since no standard terminology has been estab lished and used for mammalian chromosome descriptions, I have devised one that is both logical and easily determin able. In this description, there are four types of chromo somes, all based on arm-ratiosg the median, or metacentric chromosome'possesses a median centromere and has an arm- ratio of between lsl.0 and 1:1.09, the sub-median chromosome has a sub-^median centromere and an arm-ratio of between Is1.10 and lsl»99l the sub-terminal chromosome has a sub- terminal centromere and an arm-ratio of Is2 or greater; and the terminal chromosome possesses no visible second arm. This classification, although rather arbitrary, is necessary since distinction should be made between chromo somes with centromeres located between the median and terminal positions. Such chromosomes, here called sub median and sub-terminal, are generally collectively termed acrocentric. An attempt has been made in most oases to group the chromosomes according to size in the final karyotype of the species. However, this is not always possible as in many instances there is no distinct break in size for any morphological type, but merely a continual gradation from large to very small. In such a way, the karyotype of a species represents more than the simple diploid number or chromosomal comple ment of that species. It is also represented by a class ification of the complement into morphological types, and a further grouping of each type by size differences. Thus, slight differences between closely related species can be seen. All specimens examined in this study were collected by myself from their natural habitats, with the use of Sherman live traps (see Appendix D for locality data). luseum study specimens (skin and skull) were prepared from all animals analysed, These specimens are included in the Mammal Collection, Department of Zoology, University of Arizona, Tucson, Arizona. Species identification was made •on the basis of morphological analysis, and subspecific identification was based on locality. RESULTS A total of 95 individuals representing 8 species of the subgenus (13 subspecies) and 4 species of the subgenus were-analysed for their diploid number and chromosomal morphology. In addition, members of three subspecies of Liomys spiny pocket mouse. were analysed for comparative data. The results of these studies are listed in Table I. The species6 karyotypes are described individually below, and a representative karyotype•and composite ideogram is given for each..
Two. specimens (1 male and 1 female) of the subspecies the subspecies P. eremicus were examined. The diploid number was found to be 44 for both subspecies (see Table II). No difference in morphology of.the■chromosomes was observed between the subspecies. The karyotype (Plate I) could be separated into two autosomal morphogroups.g Group I is represented by 2 pairs of large chromosomes with median or sub-median centromeres, and Group II contains 19 pairs of terminal chromosomes that range in size from large to very small. Any attempt to further divide Group II into size classes failed due to the general gradation in size within the group. This can be seen in the composite
10 trumbullensIs ~ « formosus P« longlmembrus; .F. . mls ouds ; rotundus amplus P. parvus P. P. P. Table Xo^"Somatic ohromosome numbers and types of species species of types and numbers ohromosome Xo^"Somatic Table » baiieyl balle.yl » baiieyl • higpldus" |hj|hj|hddomensls • baileyl .^hueyl baileyl • Pcrnlx-c^ ■ * Koldmani-# fhd N Ihj .eremlcus penicillatus penicillatus penicillatus fallax Intermedius. intermedius intermedius melanocaudatus bombycinus plnacate ■plnacate Intermedlus Intermedlus Species of the genera Pero^nathus and Llomys0 and Pero^nathus genera the of 35 13 2 1 1 1 1 1 2 2 M 'F 6 2 2 2 3 8 2 7 44 2 2 3 Sex 12 1 2 00 1 68 56 1 52 <530 1 4 = GKO 2 2 44 2 2 68 46 36 56 6 46 44 46 666 6 46 46 62 56 52 52 38 50 2N 46 26 54 6 34 36 flsoeao 8222 2 28 2 18 4 S S T ST SM M 6 8 8 6 6 16 4 2 2 2 2 2 4 2 2 2 Autosomes# Chromosomes 08 10 =» = » = 22 8 6 2 4MT M 24 8 6 8S T SM SM 48 28 2 6 • «S0<3» ’ csa a « <=» = « « — » « . = « "=" ■ 8 ■ 46 16 46 42 2SM 12 16 38 52 4S I SM 24 M: 24 24 38 30 38 30 = SM SM SM SM SM SM SM SM MT SM M I X T T ? ? ? T T T T T T T T T T 56 T T 56 T T 52 ? 86 46 64 84 54 46 56 64 64 54 54 64 FN* 58 64 58 52 56 11 12
Table I. -— Continued
Sex Chromosomes Species 2N Autosomee# M F M SM ST T X
" 2 tyS 4 12 30 M' — 62 plctus 1 1 48 4 12 30 M T 62 1 ==> 48 4 12 30 M T 62
* M « median centromere? SM = sub-median centromere? ST = subterminal centromere? T = terminal centromere? FN = fundamental number. 13 ideograms, Fig. 1. The X-chromosome was determined to he a sub-median of Group I8 although it is smaller then other members of this group. The Y is one of the larger terminal chromosomes of Group II.
A total of 8 specimens of the subspecies P. g. pern representing two distinct population karyotypes $ were examined. These two types will be considered separately below. .— This population is represented by 5 specimens (3 male and 2 female)9 and the diploid number was determined to be 38 (Table III). The karyotype (Plate II) and the composite ideogram (Fig. 2) show that the autosomal complement can be divided into three distinct morphogroups. Group I contains 9 pairs of large to medium chromosomes possessing either median or sub-median centro meres. Group II contains 1 pair of small sub-median chromosomes. And Group III contains 8 pairs of small to very small terminal chromosomes„ The X-chromosome is a fairly large sub-median belonging to Group I? whereas, the Y is the largest terminal member of Group III. :-/3 . — This population is represented by only 3 individuals (1 male and 2 females). The diploid number was found to be (Table IV). The karyotype (Plate 14 Table IT,— Chromosome counts of
Catalog . Total Cells Number of Chromosomes Sex Number Counted 42 43 44 45 46 47 ^44
4e3-4*. H 28 1 24 2 1 «=» ee 85.7 UA10545* P .25 1 1 22 1 =» «=• <= 88.0 26e4«=4 M 39 •1 37 "" <=a 1 94.9 17j4-2 P 83 . , 1 2 79 1 03 = oooss 95.2 17J4-3 F 113 1 2 106 3 11 1 93.8 287 267 93.0
Ta.ble III. —-Chromosome counts of Perognathus pe OZ G
Catalog Total Cells Number of Chromosomes Sex Number Counted 35 36 37 38 39 40 %3Q.
26a5-22 M 63 ee»eso . 3 1 58 «K» 1 92.O 26a5~20 M 71 1 1 69 97.2 26a5-l? M 103 2 —— 98 1 2 95.1 26a5-18 P 97 ““ 1 96 98.9 26a5-21 P 31 1 — 2 27 1 87.1 365 348 95.3
Table IV. ^■“Chromosome countsi of Perognathus pernix-^s =
Catalog Total Cells Number of Chromosomes Sex Number Counted 34 35 36 37 38 39 %36
27a5»3 F 85 cj=> ■” 84 oamto 1 cmo a m 98.8 27a5~4 M 76 1 70 — 4 1 92.1 27a5»5 P . 78 1 73 1 3 oea^ 93.6 239 22? 95.0
#■ Numbers prefixed by UA are specimens cataloged in the Mammal Collections University of Arizona, Other numbers refer to my personal field catalog. ■' . '■ ■ ■■ ■ ' 1 5 III) and the composite ideogram (Pig, 3) show that this complement can also be divided into three distinct auto somal morphogroups5 Which closely resemble those of P, perniz-ot , Group I contains 10 pairs of large to medium chromosomes with median or sub-median centromeres. Group II contains the 1 pair of small sub-median chromosomes, And Group III contains 6 pairs of small to very small terminal chromosomes. The X-chromosome is also a large sub-median of Group 19 and the 1 the largest terminal member of Group III. The difference; therefore, between the two population karyotypes is that P. pemlx->a contains one more pair of sub-median chromosomes in Group I and four less terminals ih Group III than is.found for P. B e r n # - * .
This species is represented by nine individuals of two subspecies $ 2 males and 2 females of P. 1.- inter medins and 3 males and 2 females of P. pinacate. As can be seen from Table V the diploid number for each subspecies is *4-69 and no morphological differences can be seen between the chromosomal complements of them. The karyotype (Plate.IV) consists of three autosomal groups based on morphology and sizes Group I contains 5 pairs of large median and sub-median chromosomes? Group II contains two small pairs of sub-median chromosomes? and 16 Group III consists of 15 pairs of terminal chromosomes that grade in size from large to small» On the basis of the composite ideogram (Fig. 4)g Group 111 could be sub divided into 3 pairs of large$ 10 pairs of medium9 and 2 pairs of small terminalsThe X~chromosome is a sub-median belonging to Group I9 but is the smallest of that group. In contrast$ the Y-chromosome is terminal and the largest of Group III.
Perognathus fallax Two. specimensj both male, of the subspecies P. f\ pallldus were examined. Table VI shows that the diploid " number was determined to be 44 in both specimens. There are two groups of autosomal morphotypes present in the karyotype (Plate V )s Group I consists of 7 large to medium pairs of median and sub-median chromosomess and Group II consists of 14 pairs of terminal chromosomes that grade in size from medium - to small. The composite ideogram9 Fig. 5s shows that any further subdivision of Group II would be difficult, but that Group I could probably be divided into two classes represented by 6 pairs of large and 1 pair of medium chromosomes. The X-ohromosome is a small sub-median, and has arbitrarily been placed into Group I on the basis of morphology. However, due to size differences, it may warrant a separate group of its own. 17 The Y-chromosome is one of the smallest terminals of Group II. Generally $ the results obtained from the specimens examined were.poor9 but the karyotype obtained agreed exactly with Gross9s (1?31) analysis of the species, and thus probably represents a valid karyotype*
Six animals (2 male and 4 female) were examined. In each case the diploid number'was found to be 52 (Table ¥11). The karyotype, depicted in Plate ¥1, is made up of three morphogroups of autosomess Group I consists of 1 pair of large sub-median chromosomes, Group IX consists of 1 pair of fairly large chromosomes which I consider to be special types of the terminal form. This form, termed "rabbit-ear" chromosomes by Levan, et al. (1962) and Grippa (1964) in their descriptions of Mus museulus albinus karyotypes, displays a distinct terminal bulb which is probably due to a combination of a secondary constriction and a hetero- pycnotic area. Although not clearly demonstrated, it is thought that the centromere is in a terminal position. This type of chromosome is observed in 97.2 per cent of all cells recorded for the species? in some cell spreads only one of this type is seen, but in no case is more than two recorded. Group III consists of 22 pairs of terminal chromosomes which grade in size from large to small. The composite ideogram (Fig. 6) shows that no 18 Table V.— Chromosome' counts of PeroKnathus Intermedins, .
Catalog Total Cells Humber of Chromosomes Humber Sex Counted 44 45 46 4? 48 49 2?b4«2 p 32 2 21 1 . 8 65* 6 24b4-l M 27
Table VI. — Chromosome counts of fallax.
Catalog Total Cells Humber of Chromosomes. Humber Sex Counted 41 42 43 .44 45 46 UA10544 ¥ 48“ 1 45 93.8 UA10548 M 53 2 49 92.5 101 94 93. X
Table VII.— Chromosome counts of Perognathus artus,
.Catalog Total Cells Number of’ Chromosomes Humber Sex Counted 50 51 52 53 54 55 ^52
UA12951 M .47 2 43 1 sia vsd 1 91.5 UA12964 P 76. 2 1 70 w o w a 3 ow>csp 92,1 UA12965 F 31 1 Perognathus goldmani A total of 42 specimens of this species were analysed for their chromosome, complement. It was found that this species is represented by at least four different popu- . lationSj each with a distinct karyotype. These types will be considered individually below. Perognathus goldmani - ot . — Thi s population is repre sented by 18 specimens (13 male and 5 female), and the diploid number was determined to be 52 (Table VIII). The karyotype (Plate VII) can be divided into three distinct groups 2 Group I contains 2 pairs of median and sub-median chromosomes of medium size? Group II consists of 1 pair of fairly large ^rabbit-ear66 chromosomes$ similar to those described for P. artus% and Group III contains 23 pairs of terminal chromosomes grading in size from large to small. The ideogram seen in Pig. 7 shows that there is no distinct subdivisions in Group III. The X-chromosome possesses a terminal centromere and is the largest member of Group III. The Y-chromosome is also a terminal chromosome of Group 111$ but it is the smallest member present. 20 Perognathus Koldmanl- 6 ,®-=Thls population is represen ted by only two individuals, both male. The diploid number was determined to be 50 (Table IX)» Basicly, the karyotype (Plate VIII) is similar to that of P. goldmani- os. , except that Group I contains one more pair of sub-median chromo somes and, as a consequence. Group III contains four less terminal chromosomes. Thus, Group I has 3 pairs of median and sub-median chromosomes of large to medium length; Group II contains the characteristic 1 pair of "rabbit-ear" ter minal chromosomes; and Group III contains 21 pairs of terminal chromosomes grading in size from large to small, As with P. goldmanl-cx , the X-chromosome is a terminal and the largest member of Group III, and the Y is also of Group III but is the smallest member. PeroOTiathus goldmani-^ .— This population is represen ted by 19 specimens (7 male and 12 female). The diploid number was determined to be 5& (Table X), and the karyo type (Plate IX) also displays three distinct morphogroups of autosomes. Group I contains 1 small pair of median chromosomes; Group II contains the 1 characteristic pair of "rabbit-ear" terminals; and Group III contains 25 pairs of terminal chromosomes which grade in size from large to small. The composite ideogram (Pig. 9) shows that Group III cannot be subdivided into size units. The X-chromosome 21 Table VIIIo-“Chromosome counts of Perognathus goldmanl-oc „ Catalog Total Cells Number of Chromosomes Number S6x Counted 49 .50 51 52 53 54 • >52 UA10846 M 53 1 tea tea 51 1 CBS vea 96.2 CCB «as. UA10546 E . 61 1 1 58 1 95,1 UA10547 F 35 ” »*=» 34 1 97.1 UA11553 F 43 »a«a> 43 ao 100.0 UA11552 E 79 amatsra 1 78 ceaoRb oa e=o ■ 98.7 UA11554 M 95 «** «=» ' ■ 2 90 3 ««»«=» 94.7 «s> era UA11604 F 96 1 ■ 2 «=» «ao 93 96.9 UA11605 M ; 88 2 1 84 1 95.5 24h4“? F 136 1 1 133 1 «*«=» 97.8 UAII607 n 89 1 2 85 1 95.5 m a m a m a m a l6d4“4 m 31 . I 30. 96.8 I6d4=l5 F 23 ” » «=® «e» 23 «»«=» «c»«s 100.0 I6d4“2 M 28 oaatsa . 1 27 oa as, wen KB 96.4 25h4“3 M 34 . oaa®** 2 30 1 1 88.2 2?h4“2 M 102 1 2 98 1 «so«=s. 96.1 UA12962 M 14? 1 4 139 2 1 94.6 UAI2963 E 116 1 " = C6° 113 2 97,4 26c5“l M 76 3 1 70 2 92.1 1332 1279 96,0 Table IX,— Chromosome counts of Perognathus goldmani-6 „ Catalog q Total Cells Number of Chromosomes Number Counted 48 49 50 51 52 53 ^50 25c5“l M 37 1 ““ 33 3 89 • 2 25c5”2 M 93 1 8 b ““ 4 1 92 o 5 130 119 91.5 i is a large sub^median and clearly does not belong to the same group as the small pair of autosomal median chromo somes , However*' to avoid confusion'upon comparative analysis of the population karyotypes 9 the X-chromosome has been arbitrarily placed in Group I. The X-chromosome possesses a terminal centromere and is the smallest member of Group III, ■ ■ Perognathus groldmanl-y , — This population is represen ted by only 3 specimens (2 male and 1 female), The diploid number was found to be $2 (Table XI). The karyotype (Plate, X) is identical to that of the P* &oldmanl-»o< population except in the morphology of the X-chromosome. This karyo type also contains three autosomal morphogroupss Group I contains 2 pairs of median and sub-median chromosomes of medium size; Group II contains the characteristic 1 pair of 85rabbit-ear'8 chromosomes; and Group III contains 23 pairs of terminal chromosomes grading in size from large to small. The X-chromosome of this population is a large sub-median like that for P. goldmanl-jg 9 not the large terminal of P. goldmanl-ot or P. goldmani-5 . The X * as with the other populations of j>. goldmanl s has a terminal centromere and is the smallest member of Group III. Six males of the subspecies P. b » baileyl« one male of P. b. hueyi« and. one female of P. b. domensjs were ' ■ 23 Table X. --Chromosome counts of Peroprnathus goldmanl, Catalog 0 . . Total Cells Number of Chromosomes Number uex Counted 53. 5^ 55 56 57 58 ^56 UA11442 H 6l «a»«Q 2 3 55 1 CS9C3S 90.2 UA11555 M ' 43 1 4l autiBD 1 95.3 UA11602 ■ P 48 1 1 2 42 2 (soca 87.5: UAII603 M 73 1 3 68 1 osaee 93 = 2 UAI2952 M 96 1 1 93 1 nseso 96.9 OA12971 P 94 2 89 2 1 94.7 UA12970 M 81 1 eTOma 80 98,8 UA12950 P 87 2 1 83 1 ”eeea 95 = 4 UA12959 F 102 — 1 1 99 1 97 = 1 UAI2958 M 133 1 1 129 2 97 = 0 UA12957 P 128 2 126 a® era 98.4 UA12953 F 165 1 1 3 159 1 96,4 UA12954 F 98 00 •K0 3 2 91 1 1 92 = 9 UA12955 P 92 =»*= ca.«s> , 90 2 «»«» 97 = 8 UA12956 F 148 1 5 2 139 1 93 = 9 UA12969 P .67 1 2 1 61 1 1 91.0 UA12966 M 97 . !»»<=» 1 . «»»=» 95 1 <=>«=» 97 = 9 UAI2967 F 162 1 2 «= «*» 157 2 «» = 96.9 UAI2968 F 111 1 2 2. 106 95 = 5 1886 1803 95 = 6 Table XI,-"Chromosome counts of Peroghathus goldmani-x , Catalog Total Cells Number of Chromosomes Number Counted 50 51 52 53 5^ ^52 25a5-l M 56 -- 2 2 51 — 1 91.1 25a5-2 p. 113 l 5 — 103 1 3 91=5 25a5-3 M 77 1 1 74 — 1 96 = 1 246 228 92.7 examined for their chromosome complements„ In all cases the diploid number was shown to be 46 (Table XII)» The karyotype (Plate XI) shows that the autosomal complement can be conveniently divided into four morphogroups0 Group I contains 5 pairs of large median and sub-median chromo somes , Group II contains 1 pair of small median ehromo- ' someso Group III contains 4 pairs of sub-terminals of large size. And Group IV contains 12 pairs of terminal chromosomes that grade in size from medium to small„ The ideogram (Pig* 11) shows that no distinct subdivisions can be made in Group IV. The X-chromosome is a median and is. one of the larger members of Group I. The Y is a medium-sized terminal belonging to Group IV, Perognathus Two male specimens, both representing the subspecies P. h„ paradoxus, were examined„ Table XIII shows that the diploid number is 34. The karyotype (Plate XII) shows that there is only one morphogroup of autosomes, This group contains 16 pairs of median and sub-median chromo somes which vary in size from large to small. The composite ideogram (Fig. 12) shows that this group could possibly be subdivided into 3 pairs of large, 8 pairs of medium, and 5 pairs of small chromosomes. However, since there is no sharp delineation between these sub-divisions, it is 25 not believed that such arbitrary grouping Should be made. The X*“Chroffiosome is a large sub-median $ and the Y is a small terminal which has been placed into a group of its own$ Group II. Only one individual9 a female, representing the sub species P. £* trumbul 1 ensis,;- was examined. In this specimen the diploid number was determined to be 5^ (Table XIV). The karyotype (Plate XIII) shows that there are six morpho- groups of autosomes. Group I contains 1 pair of large sub-median chromosomes? Group II contains 3 pairs of sub median chromosomes of medium size? Group III contains 4 pairs of small median and sub-median chromosomes? Group IV contains 1 pair of large terminal chromosomes? Group V contains 3 pairs of medium terminals? and Group VI contains 15 pairs of small to very small terminal chromosomes. Since only a female specimen was examined, the sex chromo-, semes can not be determined. Upon the determination of the sex chromosomes, the morphological arrangement of the autosomes will need some revision. Three specimens (2 male and 1 female) of the subspecies P. a. rotundus were examined. The diploid number was determined to be 56 (Table XV)V The karyotype (Plate XIV) Table XI!e--Chromosome counts of Perognathus Catalog Total Cells Number of Chromosomes Sex Number Counted 44 4-5 46 4-7 48 4 9 713-1 M 33 1 93.9 713-2 M 48 vsa'axst 2 1 93.8 UA10329 M 43 ' 100.0 UA10328 M ■ 51 1 2 92.2 21c4“3 M • 36 1 35 97.2 UA12882 M 31 c = o <*s» 1 29 1 93.5 UA12881 M 45 oro.oes. 1 41 1 2 91.1 20g4 F 59 1 57 1 96+6 346 328 94.8 Table XIII.-“Chromosome counts of Perognathus Catalog Total Cells Number of Chromosomes Sex Number Counted 31 32 33 34 35 36 #34 UA11441 M 47 2 2 40 2 85.1 UA12561 M 69 4 — 64 1 92.9 116 103 88.8 Table XIV, — Chromosome counts of Catalog Total Cells Number of Chromosomes Number Sex Counted 52 53 54 55 56 57 $54 UA11598 F 67 1 1 63 94.0 and the composite ideogram (Pig. lA) show that the auto- sdmes of this species can be separated into five morpho- . groups. Group I contains k pairs of large sub-median chromosomes| Group XI contains 9 pairs of median and sub- median chromosomes of medium sizes Group III contains 1 pair of small median chromosomes; Group IV contains 6 pairs of medium terminal chromosomes; and Group V contains 7 pairs of small terminals. The first member of Group II is strongly satellitedg and constitutes the only record for such a chromosome for any member of the genus yet studied. The X-chromosome is a sub-median and the largest member of Group I, The Y is a terminal and the smallest of Group V. Perognathus longimembrus Only 2 male specimens of the subspecies P. 1, bomby- oinus were examined. The diploid number was determined to be 56 (Table XVI), The karyotype (Plate XV) and the composite ideogram (Fig, 15) show that the autosomal complement can be divided into five morphogroups, Group I contains 3 pairs of large sub-median chromosomes. Group II contains 10 pairs of medium-sized median and sub-median chromosomes and 1 pair of sub-terminal chromosomes. Group III contains 2 pairs of small sub-median chromosomes. Group IV contains 5 pairs of medium terminal chromosomes. 28 And Group V contains 6 pairs of small terminal chromosomes b The X-chromosome is a medium-sized sub-median of Group IIs and the T is a terminal and the smallest member of Group Vo . " V Perognathus formosus ' Two specimens, both female, of the subspecies Pe f. melanocaudatus were examined. The diploid number was determined to be J6 (Table XVII). The karyotype (Plate XVI) and the composite ideogram (Pig, 16) show that the autosomal complement can be divided into four morphogroups. Group I contains 8 pairs of large sub-median and sub- terminal chromosomes| Group II contains 1 pair of medium- sized sub-median chromosomes; Group III contains 1 pair of small sub-median chromosomes; and Group IV contains 8 pairs of small terminal chromosomes. The nature of the sex chromosomes remains unknown since no male was examined. Therefore, changes will be needed in the arrangement of the autosomes when the sex chromosomes are determined. Five specimens representing three subspecies were examined# I,, p. rictus* 2 females; L. p,. escuinapae* 1 male and 1 female; and L» %)° sonoranus* 1 male. The diploid number was determined to be 48 (Table XVIII), The karyo type (Plate XVII) and the composite ideogram (Fig, 1?) show Catalog Total Cells Number of Chromosomes Sex Number Counted 53- 54 55 56. 57 58 • $56 l4d3-2 M ' ' 53 «=,«» % 2 50 94.2 I4d3-1 M 48 1 -0- 2 43 2 90.0 l4d3-3 F 27 = » « » ' 1 25 1 = ^ 93 = 0 128 118 92,2 Table XVI. — Chromosome counts of Catalog . Total Cells Number of Chromosomes Number S®x Counted 53 54 55 56 57 58 7d3-l M 42 1 1 — 39 1 92»9 4e3-2 M 38 — - 1 1 33 — 3 86*8 80 72 90,0 Table XVII, Chromosome counts of Peromathus formosus. Catalog Total Cells Number of Chromosomes Number Sez Counted 34 35 36 37 38 39 %36 UA12471 P 118 5 1 109 3 — 92,0 UA12510 P 76 1 2 71 — 1 1 93 = 0 30 Table XVIII.— Chromosome counts of Catalog Total Cells Number of Chromosomes sex Number Counted 45 46 47 48 49 50 ^48 UA12561 F - 76 1 1 CCO <80 71 3 93.4 214-2 F 31 taaae. 1 28 1 1 90.3 27a5-6 M 47 co-ew — 46 1 97.9 26a5~7 F 25 1 — 23 1 q» 92.0 26k4-l4 . H 28 — 3 — 24 ; 1 85.7 197 184 93,4 that the autosomes can generally be divided into two morpho- groups. Group I contains 8 pairs of large to medium-sized median and sub-median chromosomes, and Group II contains 15 pairs of medium to small terminal chromosomes which grade in size,* The X-chromosome is a medium-sized median chromosome of Group I, and the 1 is one of the smaller terminal chromosomes of Group II, DISCUSSION Evolution of the Karyotype The methodology in oytotaxonomy is based on the concept that the chromosomal complement is a specific constant. This has generally been demonstrated to be true, but some cases are on record where the karyotype varies between pop ulations (e.g.9 in subspecies of Citellus richardsoni. Nadler 1964b, 1964cs in gerbils, Wahrman and Zahavi 1955? and in lemurs, Chu and Swomley 1961) or within a single population (e.g., Sores araneus, Ford, Hamerton, and Shar- man 1957)• Changes in the karyotype can either involve change in the morphology of individual chromosomes or a change in the number of chromosomes present in a given karyotype. The latter concept has been further refined to include not only changes in the diploid number, but more signifi- ,• cantly$ changes in what Matthey (1951) terms the wfunda mental number.M This represents the total number of autosomal arms in a chromosome complement, and as such provides a basis for analysis of the amount of genetic material available to a given animal. The concept of the fundamental number also provides a base-line from which population or species differences in karyotypes can be evaluated. 32 In the following sections$, the various methods for . chromosomal change will he presented, and a discussion of the role of each as an evolutionary mechanism will be made. Changes Affecting Individual Chromosomes Polysomy.---This type of change involves the dupli cation or loss of one or more chromosomes from the comple- ment due to non-disjunction during division. Although examples of polysomia races are found commonly in natural populations of plants (i.e.* Datura, Zea9 and Crespis), little Information is available to demonstrate that such changes are normal in animals. Aside from a few cases, of polysomic sex chromosomes in mammals (e.g.g the X^X^-Y or X-Y^Y2 of the marsupial Macropus ualabatus, Agar 1923I the X-Y^Yg Of the male shrew Sorex araneus, Sharman 1956), the evidence to date in humans shows that most cases of polysomy are associated with deleterious effects. It there fore seems unlikely that polysomy has had much influence on the evolution of the mammalian karyotype. Structural changes.--This is an all-inclusive group of changes that includes the various.types of translocations, inversionsg and deletion-duplleation factors. Of these-, only symmetrical translocations and inversions would be of evolutionary significance. Of the inversion types$, only the pericentric Inversion would be detectable. Until . ' 34 linkage data are available for mammals $ it would be impos sible to describe chromosomal races on the basis of para centric inversions $ as has been done in Drosophila. Fusions and fisions.— Probably the most important mechanism for chromosomal evolution in mammals is the phenomenon known as centric fusion, or 16who 1 e-arm” trans- location. It was Robertson (1916) who first noted, in his work on insects, that V- or J- shaped chromosomes might have arisen by the apical or centric fusion of two rod-shaped chromosomese Using fusion as a basic principle, the differences often observed between the chromosome complements of closely related species can often be accoun ted for. In such cases, where diploid numbers vary, the fundamental number remains the same. It could be concluded, therefore, that a V- or J- in one species was equivalent to two rod-shaped chromosomes in a related species. The phenomenon of centric fusion has been described in many cases in insects (White 1954) and lizards (Matthey 1951). It has been demonstrated to be a dominant means for chromosomal evolution in Drosophila (Patterson and Stone 1952), and has only recently become realized as having great influence in the evolution of mammals (Tobias 1956? Makino 1948? Matthey 1963? Nadler 1964a? and Benirschke, et al. 1965). Although Stone (1962) lists fusions as the least probable mechanism for chromosomal change on the basis of the probability of occurrences fusions are found to be second highest in frequency in the evolution of Drosophila karyotypes. It is obvious that natural seise™ tlon8 not probability$ is at work here. Since'aneuploidy has been shown to result from translocations and inversions$ but not from fusions (for example, see Stone 1949)$ it is probable that the latter possess a greater selective advan tage then, the former mechanisms. Also, centric fusions are more possible, at least in Drosophila, than other kinds of translocations because of the large blocks of hetero- chromatin surrounding the centromere, . Doss of a centro mere plus adjacent heterochromatin produces no marked effect on viability $ and consequently can be better with stood then the loss of euchromatin (Swanson 1957)» The possibility of fision, instead of fusion, is also present, but from data obtained mostly from plants, fision seems unlikely. In order for fision to take place, either a new centromere must be formed, or the original centromere would necessarily be split vertically. In the former, no plausible explanation can be given for the formation of a new centromere (Swanson 1957)$ and in the latter, isochromo somes would form (Darlington 1939)« These isochromosomes have been shown to be unstable (Rhodes 1940) in those organisms studied. Moreover, it has been demonstrated in organisms which were formerly thought to have truly 36 telocentric chromosomes (in certain orthopteran chromosomes, White 1935? and in Drosophila melanomas ter <, Griff en and Stone 1940) that a very short arm is invariably present in such cases. It seems, therefore, that truly terminal chromosomes do not occur naturally, and as a result fision. can be ruled out as an evolutionary mechanism. It must be stressed that fusions are not the answer to all problems dealing with variability in chromosome number. Clearly, other structural rearrangements can in fluence the number of chromosome arms; but, whereas fusions can be easily detected, the part these other changes have played In the chromosomal evolution of mammals can only be inferred on indirect evidence and by the elimination of other types of variation. Changes Affecting Sets of Chromosomes: Polyploidy There appears to be little likelihood that polyploidy has played much of a role in mammalian evolution, although it is one of the most common forms of variation in plants (Stebbins 1950)« In animals with sex chromosome mechanisms considerable disturbances in bi-sexual reproduction may be caused by polyploidy (Melander 1963)# Also, dioecious polyploids are rare in both plants and animals (White 1946). In general, polyploidy seems to have been the motif of evolution in plants, fusion that in animals, with additional 3? structural variations occurring with less frequency and of less importance. . ■ Trends in Numerical Changes of Chromosome Complements of Mammals There are a few general trends that can be fairly well established on the basis of present knowledge of mammalian karyotypes. Of most importance5 there seems to be a trend toward a reduced number of chromosomes coupled with an increase in the number of V- and J-shaped chromo somes and a subsequent loss of rod-shaped chromosomes in the evolution of any one group. Here the influence of centric fusion can be seen. This principle has been amply demonstrated in many animals9 particularly in Drosophila (Patterson and Stone 1952). Less authenticated, but similar results.have been obtained for several mammal groupsi in primates (Bender and Chu 1963)9 in microtine rodents (Matthey 1957)$ and in bats and insectivores (Bovey 1949). There seems to be little doubt but that centric fusion is the prime evolutionary mechanism in mammals$ and as such has brought about a general trend towards a decreased diploid number with the maintenance of a fairly constant fundamental number within any one mammalian group. It should be pointed out here that such karyotyplc changes as outlined above originally only occur in and . affect the individual. In order for a karyotype change to become fixed in a population there must be some selec tive advantage for the alteration. Then the change will represent a newly evolved karyotype for a population and eventually could lead to species formation. If the change is disadvantageous„ it will not become fixed and will be lost. Consequently$ as with other morphological features$ karyotype evolution is merely the visible evidence of the selection of advantageous genotypes. ' ' Karyologi oal Taxonomy of the Genus Perognathus Wood (1935)9 In his monograph on the evolution of Heteromyid rodents 9 traces the genus Perognathus back to the Miocene (see Pig, 18). He concludes that the separation of the two present subgenera was complete by late Miocene or early Pliocene (the common ancestor supposedly being represented by the fossil P. furlongi). Since that time the evolution of each subgenus has been1 on slightly diver gent paths. Although the fossil evidence is by no means complete9 the fact that the two subgenera have been sepa rated for a long time is evident from only superficial observation. There is little overlap of distinctive char acters between members of the two groups? although some species do approach each other in gross morphology. Members of the subgenus Perognathus (silky pocket mice) differ from the spiny pocket mice* subgenus Chaetodlpus snjqaiButiduoi snfdwo ii V)3 CQ) X)O' CZ)3 dnojB snAjod snpidsm & tM/toq d Late Miocene snsowjoj d R fur/ongi R snjDi/ioiudd d sn/joudjo d xtujod d f snjjo d fuovupioB d V) 3 C snipauujoiui snofujojuoo d sntouids d Figure 18.— Phylogenetic chart of the genus Perognathus. Fossil phylogeny after Wood (1935); recent phylogeny based on morphology (Hall and Kelson 1959) and karyology (this study). 40 in five diagnostic characterss (1) general softness of pelage9 (2) soles of hind feet hairy$ (3) tail not crested9 (4) mastolds greatly inflated; and (5) breadth of inter■» parietal less than breadth of interorbital region* This dichotomy between the two subgenera is also evident in a chromosomal analysis of members of these groups» Although the average diploid number for each subgenus is quite Close (46 for Ohaetodious and 48 for Perognathus)* the average fundamental numbers are widely different (56 to ?2 respec tively), An obvious wide separation between the two exists chromosomally as well as morphologically; since the funda mental number has more significance in the evolution of the karyotype than the. diploid number. This separation is more apparent if the figures for P. formosus are not included in the average for the subgenus Perognathus (the reason for this will be discussed below). The range in diploid number is then from an average of.46 for Chaeto- dipus to 56 for Perognathus« with an accompanying greater difference in fundamental number from 56 to 79$ respec tively, These figures are based on inadequate sampling; especially for the subgenus Perognathus * but I contend that with further investigation the marked morphological differences will continue to be feflected in the karyotype of each group. 41 Within the subgenus Perop;nathus there are four recog nized species groups (Hall and Kelson 1959)9 of which three were sampled in this study. The chromosomal analysis of each species group indicates that each group is. distinct. While the members of the parvus and longimembrus groups that were examined have similar diploid numbers9 their fundamental numbers (66 and 85 respectively) differ rad ically* Perognathus formosus, the single representative of the formosus species group9 also is in a separate class. But, as mentioned above, this species does not conform with the pattern of high diploid number and high fundamental number displayed by other members of the subgenus. In respect to its long, crested tail, hairless soles of the hind feet, and supra-orbital constriction by the mastoids, P, formosus closely resembles the spiny pocket mice. This phenotypic resemblence is also reflected in the karyotype, which parallels that of the intermedlus species group of the subgenus Chaetodjpus* Perognathus formosus should, then, be considered either a close link between the two subgenera in terms of phylogeny, or an example of conver gent evolution which is displayed in both gross morphology and karyotype, A more complete systematic study of this species may necessitate the placement of P. formosus in a subgenus of its own, representing a link between the two recognized subgenera. 42 The subgenus Ghaetodl'pus consists of six recognized species groups (Hall and Kelson 1959)= Pour of these groups have been adequately sampled, and only two, which are monospecifics have not been examined. As with members of the other subgenuss each group has its own chromosomal characteristics. These is generally no overlap in the fundamental number between members of different groups (Table I), Two of the three, species of the penicillatus group have been sampled. It is found that these two species9 P. penicillatus and P. pernix, differ greatly, however, particularly in their fundamental numbers (46 and 56 respectively). Because P, pernix has a fundamental number within the range of the intermedius group leads me to in clude it within this group. This arrangement is based on some morphological evidence, also, for the specimens of P. pernix examined have, at least weakly developed rump spines. The presence of this character is a major feature distinguishing members of the two Species groups. Some authorities have considered P. penicillatus and P. intermedius to be sibling species. An analysis of their karyotypes, however, indicates that the two are not genetic sibling species, but that their phenotypic similarity is probably a result of parallel evolution. The intermedlus species group has diploid numbers ranging from 36 (if P. pernix is included) to 56$ but the fundamental number for.each species remains fairly constant (52-58). Differences in the fundamental number of this small magnitude could be the result.of chromosomal evolu tionary mechanisms other than the common, centric fusion. Perognathus hispidus and P„ baileyi, each representing monotypic species groups$ have widely,divergent diploid numbers 9 but the same fundamental number of 6b, Both of these species more closely resemble members of the sub-, genus Perognathus, particularly the species P. parvus, than do other species of Chaetodlpus, especially in a lack of rump spines and a more general softness to the pelage. This closeness is reflected in the chromosomal complement with regards to the fundamental number$ which is at the lower end of the range for the silky pocket mice (excluding P, formosus). A close relationship between P. hispidus and. P. parvus is also reflected in.the similarity of their distributions $ habitat, general pelage, and cranial compo sition, Perognathus hispidus is the only member of the subgenus Qhaetodipus which has a non-crested tail, a trait generally diagnostic for members of the subgenuS Perogna- thus. Similarities In fundamental number are probably the result of convergence, but could mean a close phyletie relationship between P. - hispidus and P, parvus, The same • ' # fundamental number of P, bailey1 and F. hlsptdus indicates a close relationship* but the evolution of suoh distinct karyotypes probably required'large amount of time. Chromosome Races in J?„ goldmanl and P» pernix The generally accepted concept that the chromosomal complement in mammals is a species constant has been shorn not to be an iron-clad rule. Many cases of chromosomal races within a given species have been reportedI Citellus richardsonl (Na&ler 1964b); Gerbillus pyramidum (Wahrman and Zahavi 1955)I Acomys oahirlnus (Zahavi and Wahrman 1956)! and Acomys alnous (Matthey 1963). Generally$ how ever $ these races are represented by distinct* geograph ically isolated populations* and only in cases of true polymorphisms (Ford* et al» 1957? Wahrman and Zahavi 1955? Matthey 1963) is there found chromosomal variations within a single population. In P, goldmanl and P. pernix, chromosomal races are found* but these races are in no way geographically iso lated. Only one chromosome pattern is found to be present witnin a.single populations and since no recombinants have as yet been found* it Is assumed that each population is monomorphic. If any Isolation is present between the populations* it must be of a genetic or ecologic nature. Wo direct evidence is. available at present to demonstrate either type of mechanism conclusively. 45 The occurrence of four distinct karyotypes within P. goldmani and two within P. pernix requires an explanations since most mammalian species possess rather uniform chromo somal complements. One explanation might be that each chromosomal pattern represents a distinct species, but casual observation of diagnostic characters does not sup port the hypothesis that more than one species exists, A second explanation could be the presence of a chromo somal polymorphism within each species. This, however, is doubtful since individual populations are represented by only one chromosome pattern, and as yet, no recombinants have been found. A third and perhaps more plausible explanation for the occurrence of intraspecific chromosomal populations is that the populations represent intermediate evolutionary stages between a single population with one karyotype and the stage of speciation characterized by reproductively isolated populations with different karyotypes. Support for the validity of this hypothesis, in the case of both jP. pemix and P. goldmanl 9 may be derived by an establish ment of the cytologioal mechanisms converting one karyotype into another. The mechanism of centric fusion is suggested because each karyotype of P. goldmanl contains a fundamen tal number of 54 (except for P. goldmanl-n )» The funda- . mental number of P. pemix remains constant at 56 = 46 In Pe p e m i x o the karyotype of P„ permix-/? displays one less pair of sub-median chromosomes in Group I and two more pairs of terminal chromosomes in Group II than is • found in the P, pernix-ot karyotype. On the basis of the hypothesis for centric fusion, the difference between the two populations could be that the four extra terminals in P. pemlx- /P goldmani-b 2N=50 ; FN=54 / 3 Fusions % X=large T INTERMEDIATE 2N=54 FN=54 I Fusion X = large SM PRIMITIVE 2N = 56 FN = 54 No Fusions X = large SM Figure 19.— Phylogenetic relationships between the four chromosome races of Perognathus goldmanl and Perognathus artus. Arrows Indicate proposed direction of evolution. FN =* fundamental number; 2N = diploid number; SM = sub-median; and T = terminal. . ; ' ^ instead of the sub=>median X^ehromosome. This population is represented by P;. goldmani-01 , The change In centro mere position in the X^ohromosome can be explained- by a perioentrie inversion, Perognathus goldmani-6 was then derived from P° goldmani-w by a third fusion^ The terminal . X-ehromosome of P0 goldmani-6 indicates that it was derived from P. goidmani-K and not P. goldmani-y. Perognathus goldmani°/g, on the other hand 9 appears, to " have less relation with the other three populations than it has with the hypothetical primitive. It was derived from the primitive by means of a pericentric inversion in one of its autosomal pairs, accounting for the observed fundamental number of 5.6, as opposed to 5^9 and one small, unique pair of median chromosomes. This is supported, by P, goldmanl-a possessing the hypothetical sub-median X- chromosom© of the primitive. Correlation can be made between karyotype evolution and race dispersal, despite the fact that the exact geo graphic range (Fig. 20$ map) of each chromosomal race has not yet been determined.' It 18 possible that the primitive P, goldmani occupied the whole of the known present range of the species at one time, and then was split up Into the different populations through time. It seems more plausible, however, on the basis of ecological data of the area (see Leopold I950)s that the primitive was confined to the thorn 50 pd. Obregon R goldmoni-c* El Fuerte Son Bias CHROMOSOME RACES B P goldmani-c* ■ P goldmani-/a Los Mochis D P goldmani- y G# /P goldmani-6 PRESENT‘ RANGE OF Perognathus goidmoni Figure 20.— Map showing the present range of the species Perognathus goldmani, and the localities of the four chromosome races described for this species. 51 forest of northern Sinaloa and southern Sonora, and that a peripheral population bordering on the Sonoran desert in southern Sonora evolved to give rise to P. goldmani-# , which today is found in desert habitats. Prom this form arose P. goldmani°ct and P. goldmani™6 which despersed to occupy the thorn forest foot-hills of southeastern Sonora and northeastern Sinaloa, It whould be noted that P, goldmani-f is found only south of the Bio Puerte in northern Sinaloa, and that it is the only race found in this southern-most part of the geographic range of P. goldmanl, It is possible that the river may have formed, at one-time, a natural barrier splitting the primitive P, goldmanl into two populations. The northern population evolved into P, goldmanl-# (and from it P. goldmanl-oi. and -6) $ and the southern population evolved into P, goldmanl-/g , The river may still be a formidable barrier, since on the north bank is found J?. goldmanl-5 and on the southern bank P. goldmanl. It is doubtful, however, that a difference of four fusions and a rearrangement of the X-chromosome would;allow for sue- cessful hybridization, in spite of the fact that minimal chromosomal material would have been lost in the karyotype conversion. If this is true, then a genetic isolating mechanism and not a physiographic one is present, and species rather than races are involved. Until a thorough 52 systematic morphological analysis has been made9 however, • I hesitate to made final statements here, and will con tinue with the terminology of chromosome races„ The data presented above supports present evolutionary concepts; iee,$ speciation usually results from the geo graphic isolation of a peripheral population with subse quent development of reproductive isolating mechanisms (Mayr 1963)0 Greater opportunity is available for per ipheral populations to utilize favorable mutations, gen© sequences, or chromosomal rearrangements by invasion into new habitats. As examples, P, pernlx-yg has moved out of the thorn forest habitat typical for that species into the tropical savannas along the coast of northern Hayarit, and Po goldmani-Xrhas moved out of the thorn forest of-the primitive P. goldmami into the Sonoran desert. Although the role of chromosomal rearrangements is not clear in speciation, the chromosomal data appear to identify, at least, an intermediate stage in the evolution of both P, pernix and £» goldmani 0 which could not be detected using standard taxonomic characters, ■ • The Status of P. goldmani and p 6 artus Since Osgood°s original description of J\ goldmani and P, artus (1900), considerable confusion has arisen as to the systematic status. Hall and Ogilvie (i960) synonomized the two species, but Anderson (1964) concluded that they repre sented separate, although very closely related species. The data obtained from chromosomal analysis supports Ander son es hypothesis, Perognathus artus probably was derived from the primitive P. goldmani (Fig, 19) through.the loss of a pair of chromosomes plus one fusion, accounting for ■the observed fundamental number of 52. This derivation is supported by the presence of the same sub-median X- chromosome in £. artus as is found in the primitive P„ goldmani. Also, one pair of so-called 19rabbit-ear” chromo somes is present in all karyotypes of both P. goldmani and P. artus, but not in any other member of the genus studied. If Levan, et, al. (1962) are correct in the assumption that the special type of chromosome represents a karyological marker, then its presence in both of these species indicates a close relationship between them. The loss of the pair of autosomes in P. artus may be the factor enabling these two to be sympatric species rather than just chromosomal race, as indicated by the similarity in chromosomal com plements. Evolutionary Trends within the Genus Perognathus The genus P e r o g n a t h u s as in other Heteromyids, has the tendency to inhabit the more arid grasslands and deserts 54 supported by karyologlcal evidence, Perognathus hispidus has the most advanced form of karyotype for any member of the genus yet examined $ with its low. diploid number of 34 and its karyotype of all median and sub-median chromosomes. The advancement in karyotype parallels an advancement in morphological features characteristic of the species, in dicating an adaptation to a more varied environment and an increased geographical range, A better example of distribution coupled with karyo- logical evolution can be seen in members of the intermedius species group. Although all members of the group have not been examined, their level of chromosome evolution can be inferred from what is known of the other species of the group. The primitive P. goldmani represents also the primitive member of the intermedius group, as reflected in its more generalized morphology as well as karyology. Due to isolation on the northern west coast of Mexico, and to inability to cross the high Sierra Madras, dispersal out of this region could only occur in two directions: north into the Sonoran and Chlhuahuan deserts, or south into the thorn forest-deciduous forests inhabited by Liomys, The geographical distribution of P, intermedius, with its lower diploid number but nearly the same fundamental number, represents a step in the northern evolution and dispersal of this group. Since there is a wide difference 55 in the western United States and northern, lexieo. There has been a steady evolutionary trend toward increased adap tation to such environments by members of this genus since late Miocene, when the habitat of western North America was essentially the same as today (Mood 1935)» The fossil record indicates that the ancestors and early members of the genus arose in the western United States9 perhaps in the Great Plains area (Mood 1935)« However, with the advent of the ice advances and associated climatic and environmental changes during the Pleistocene, the genus Perognathus retreated to the south in Mexico, following the displacement of the arid habitats. Since the end of the Wisconsin there has been a tendency by the genus to reoccupy the now arid lands of the west-central United States (Kennerly 1956), Considering centric fusion as the major phenomenon for karyotypic change in this genus, the results of such changes reflect dispersal trends within its members. For instance, P. hisnldus Is the most wide-spread member of the subgenus Chaetodipus a ranging from North Dakota south through the Great Plains into the central plateau of Mexico, Since the distributional patterns represent the most varied types of habitat for any member of the subgenus$ It could be assumed that P, hlspldus represents the least specialized and prob ably most recent of the spiny pocket mice. This is , in karyotypes between Pe ^oldmani and P. intermedins, it oan be assumed that this step took a long time9 and that the intermediate forms have since disappeared*. On the other hand$ P. fallax* whose distribution runs from the western most range of P. intefmedius down into Baja Calif ornia (see Fig* 2 1 9 map)3 is very closely related to this • species, However9 since it has lost a pair of chromosomes in its evolution form P» intermedius or an intermedins- like ancestor* P* fallax represents a slightly more special ized species. It follows that the suggested route of dispersal began in the Sonoran-Si rial ban border area occu pied by P, goldmani* moved up into southern Arizona (P. intermedius)„ and then down into Baja (P, fallax), A similar occurrence probably happened in the dispersal of • the group from the eastern range of P. intermedius down the east side of the Sierra Madres into the central plateau of Mexico. Although the karyotypes of the present forms in this area (P. nelson! and P. llneatus) have as yet not been analysed $ the morphological similarities of these species to P. intermedius suggests that such a probability existse The distribution pattern of P. pernlx represents a different direction of dispersal from the center of origin3 since it moved south instead of north. In doing so many modifications were necessary to derive this karyotype from 57 P fall ax P intermedius P go/dmani P nelson! P artus Present known range P Uneatus P permx-djTj Hypothesized route of dispersal Figure 21.--Map showing the present range of members of the Intermedius speoles group, subgenus Chaetodlpus, Of the genus Perognathus. Arrows Indicate the hypothesized route of dispersal from the center of origin at the Sonora-Slnaloa border area, as Indicated by oytologlcal evidence. that of the primitive P» goldmanl .• If the amount of time necessary for the development of these modifications and for dispersal south is roughly equivalent to that for the northern movement, then the much less amount of geographic area occupied by the southern derivatives may have been due to competition with Llomys» If true9 then P. perniX”^ represents a population that has become sufficiently specialized to allow it to Invade territory once wholly held by Llomys0 and to successfully compete with this species. SUMMARY AND CONCLUSIONS A total of 95 individuals representing eight species of the subgenus Chaetodlpus (13 subspecies) and four species of the subgenus Perognathus were analysed for their diploid number and chromosomal morphology. In addition, members of three subspecies of Llomys plctus, spiny pocket mice, were analysed for comparative data. The following points are concluded from the collected data, 1, Each species of the genus Perognathus is karyo- typically distinct, and no apparent difference within any species at the subspecific level was observed, 2, Cytotaxonomic analyses generally substantiate the classical taxonomic arrangement of the genus Perognathus, a. There is no over-lap in fundamental numbers between species of both subgenera, except In. P, formosus. The karyology as well as anatomical morphology suggest a close relationship of this species to members of the subgenus Chaetodlpus, Perognathus formosus probably represents either a relict line that is intermediate between the two subgenera or an example of convergent evolution, b. The more specialized members, of both sub~ genera represent the extremes in karyology while those 59 that tend to bridge the morphological gap between the two subgenera indicate a close karyotypic relation. c. : Members of each species group (for both sub genera) display distinct and characteristic-karyotypes. This indicates a polyphyletic origin for the genus* at least at the subgenerie level. d. The high fundamental number for P. pernix indicates a closer relation to the intermedius species group than to the penicillatus species group * in which it is presently placed. It is concluded that P. pernix belongs in the former group. e. Karyotypic evidence suggests that P. penicillatus and P. intermedius are not genetic sibling species* but that their morphological similarities are the result of parallelism. f. Perognathus hlspldus * on the basis of ■ morphological* karyologieal* and distributional data* represents the most advanced member of the subgenus Chaetodipus yet examined. g. The maintenance of P, goldmani and P. artus as distinct* but closely related species is suggested on the basis of karyological evidence. 3. The present accepted species * P. goldmani* is represented by at least four chromosomal races which differ only in the number of fusions and morphology of the X-chromesome. Each population examined contained only one chromosomal type. The lack of recombinant types indicates that a true polymorphism does not exist in this species. Thus, the karyologieal evidence appears to necessitate the elevation of P. goldmani”x and the com- blned P. Koldmani- o< and P. goldmanl~5 races to full . ’ Species rank. 4. P..pernix is represented by two chromosome races which differ on the basis of one fusion. The more ad vanced form is found on the periphery of the geographical range of the species where it has Invaded a habitat atypical for members of the genus. . 5. Karyologieal comparison of present members of the Intermedins group Indicates that the group had a probable origin in the Sonoran-Sinaloan west coast of Mexico, and has since dispersed Into the southwestern United States, moving both west in Baja California and east and south into the central Mexican plateau. The dispersal of P.. pernix south from the area of origin has proceeded much more slowly, probably due to the necessary invasion of habitats once solely occupied by the Heteromyid genus 6. Further information is needed from members of this genus not examined before a phylogeny based on karyology of the entire genus can be constructed. 62 APPENDIX A: PLATES I KX HK n on on 6 (Ifl 00 Y ZVA AA n a A A A* A A A A A A A m * » Plate I.— Representative male karyo penicillatus. X5200 63 XX XX XX XX XX X X xx xx xx xx H x x JJJ A/ * + + + • A A #N A A a Plate II.— Representative male karyotype of Perognathus pemlx-cx . X5200 iXt xx xx xx xx X XX XX XX XX XX H x x ]]J A A A A Y Plate III.— Representative male karyotype of Perognathus pernlx-jg . X5200 64 ■ M xx n n n x n x k xx m 11(1 AA A/i a a ^ AO AA ftft Afl A A y ^ y w /i y% /| a •* ** ^ a Plate IV.— Representative male karyotype of Perognathus Intermedlus. X5200 65 XX KX XX XX XX XX XX XX n a a A/* AA A A A A A A * * €i Y Plate V.— Representative male karyotype of Perognathus fallax. X5200 i n n f i A rn00 fin 00 00 00 00 00 00 00 00 04 00 00 n o on no m on ft A (\ A A tl AA An Plate VI.— Representative male karyotype of Perognathus artus. X5200 6? I XX KX n ft « m nn ft/l Aft ftft nn AA on no on on OA nn no no nn OA AA n n AA A h A A Plate VII.— Representative male karyotype of Perognathus goldmanl - cx . X5200 68 % n NX KX : ('III il/l Art M l AA AA II Oft (IA M a a nn AA A/I Afl n» AA AA A A A A A A A Y Plate VIII.--Representative male karyotype of Perognathus goldmanl-S . X5200 69 I XX x n AO m AA no on no Oil on 0/) on on no OA 00 on n o 00 on no no An on no AA A A A Y Plate IX.— Representative male karyotype of Perognathus goldmanl-jg . X5200 70 i HA XX % n (111 ™rtd nn on ao aa no A A AA AA AO AH Aft AII AA A^~ AA A A AA AA n A A A A A -c> Plate X.— Representative male karyotype of Perognathus goldmanl-ff . X5200 i n n xxxx u n k x ra AH AA ft* A« EZ ZSA ^A -AA A * + * + A A A A A A A A A*» XI.— Representative male karyotype of Perognathus balle.vl. X5200 72 KX XX X* XX X XX XX XX XX XX XX XX XX X X Plate XII.— Representative male karyotype of Perognathus hlspldus. X5200 73 I XB E X K KK XX X X X H KK XX X R u Y on nn no H 0 A nix A A A A Plate XIII.— Representative female karyotype of Perognathus parvus. X5200 74 i HK XX XX XX 8 n xii xx xx xx xk u x x M X XX EI * K X X E? (I /V (VA /IA A A A A AA Y ^^ ^A AA A^ Plate XIV'-'Representative male karyotype of Perognathue 75 UK XK n XM XX XX XX XX MK *x XX XX XX m x x XX h no nn flA <\A A A Y a a AA Plate XV.— Representative male karyotype of Perognathus longlmembrus. X5200 76 I n h nx xx xx XX XX x» O X X in x k ]2 y ^ A ^ y* /% A #% a v*x» Plate XVI.— Representative female karyotype of Perognathus formosus. X5200 I XX XX NX MX X X XX MH X X n flfl A A A A A A A A A A A A A A A A A A A A * * Plate XVII.— Representative male karyotype of Llomys Plctue. X5200 ---- APPENDIX Bs IDEOGRAMS 78 79 I0-, Perognathus penici Uatus 2 N = 4 4 5 - 10 15 20 25 30 35 40 Chromosome Number Figure 1.— Composite ideogram of the male Perognathus penicillatus karyotype, based on measurements of 10 somatic metaphases. X5200 10— i Perognathus pernix-o* 2N=38 5 - o» c e 10 15 20 25 30 35 Chromosome Number Figure 2.— Composite ideogram of the male Perognathus pemlx-ot karyotype, based on measurements of l6 somatic meatphases. X5200 Figure 3 Figure Figure4 Length (in mm.) lO-i 0 5— —CmoieIega f thePerognathusIdeogrammaleof Composite .— .— Composite ideogram of the male Perognathus male the of ideogram Composite .— 5 0 5 0 5 0 5 0 45 40 35 30 25 20 15 10 5 I 0) c o f1 oai eahss X5200 somaticmetaphases.10of pernix-^ karyotype, based on measurements based pernix-^ karyotype, f1 smtcmtpae. X5200 metaphases. somatic 10 of intermedius karyotype, based on measurements on based karyotype, intermedius IO-i 0 - 5 eontu intermedius Perognathus hoo oe Number Chromosome 0 5 0 25 20 15 10 hoooe Number Chromosome eontu pernix-^ Perognathus 2N=46 2 N=36 0 35 30 80 81 I On Perognathus foil ax 2N = 44 5 - 5 10 15 20 25 30 35 40 Chromosome Number Figure 5.— Composite Ideogram of the male Perognathus fallax karyotype, based on measurements of 10 somatic metaphases. X5200 10— i Perognathus art us 2 N=5 2 —X E E c - 54 £ o» % -Y 10 15 20 25 30 35 40 45 50 Chromosome Number Figure 6.— Composite Ideogram of the male Perognathus artus karyotype, based on measurements of 10 somatic metaphases. X5200 82 IO-i Perognathus go Idmoni - Q> —Y 10 15 20 25 30 35 40 45 50 Chromosome Number Figure 7.— Composite Ideogram of the male Perognathus goldmanl-oc karyotype, based on measurements of 10 somatic metaphases. X5200 IO-i Perognathus goldmani -6 2N = 50 -X 5 - —Y 10 15 20 25 30 35 40 45 50 Chromosome Number Figure 8.— Composite Ideogram of the male Perognathus goldmani-5 karyotype, based on measurements 10 somfctic metaphases. X5200 c 0) o* Figure 10.— Composite ideogram of the male Perognathus male the of ideogram Composite 10.— Figure Figure 9.— Composite ideogram of thePerognathusideogramofmale Composite 9.— Figure - 5 Length (in mm.) IO- - 5 i -X -X 1 1 2 2 3 3 4 45 40 35 30 25 20 15 10 5 goldmanl-a karyotype, based on basedmeasurements karyotype,goldmanl-a f1 oai eahss X5200 somaticmetaphases.of10 goldmanl-y karyotype, based on measurements on based karyotype, goldmanl-y f1 smtcmtpae. X5200 metaphases. somatic 10 of 0 5 0 5 0 35 30 25 20 15 10 eontu goldmoni Perognathus eontu go/dmani- g Perognathus hooo e Number Chromosome hooo e Number Chromosome 3 / - 2 2 N=52 2N=56 045 40 055 50 50 83 -Y — Y Figure 12.— Composite Ideogram of the male Perognathus male the of Ideogram Composite 12.— Figure Figure 11Figure Length (in mm.) I0-. o-J— 5- I • — Composite ideogram of the male Perognathusthe•ideogramof male Composite — _J € c © lO-i - 5 0 oai eahss X5200 metaphases. of somatic 10 measurements on based karyotype, hlspldus balleyl karyotype, based onmeasurements based karyotype,balleyl oi 1 1 2 2 3 3 4 45 40 35 30 25 20 15 10 5 zx 6smtcmtpae, X5200 somaticmetaphases,16 eontu hisp idus Perognathus h oo oe NumberChromosome eontu b aiteyi Perognathus 0 5 0 25 20 15 10 hoooe Number Chromosome 2 2 N = 34 XY 2 N=4 6 30 84 85 10-1 Perognathus parvus 2N = 54 5 - jC o» Ce 10 20 25 30 35 40 45 50 Chromosome Number Figure 13.— Composite Ideogram of the female Perognathus parvus karyotype, based on measurements of 10 somatic metaphases. X5200 IO-i jrX Perognathus amptus 2N=56 5 - 0) _J 10 15 20 25 30 35 40 45 50 55 Chromosome Number Figure 14.— Composite Ideogram of the male Perognathus amplus karyotype, based on measurements of 10 somatic metaphases. X5200 Length (in mm.) Figure 0 5— Figure 16.--Composite ideogram of the female Perognathusthe16.--Compositefemaleideogramof . opst dormo thePerognathusofideogrammale Composite 5.— 1 - 5 • l5-i * 0 ' f1 smtcmtpae. X5200 somaticmetaphases.10of onmeasurements based karyotype, longimembrus 0smtcmtpae. X5200 somaticmetaphases.10 0 5 0 5 0 35 30 25 20 15 10 formosus karyotype, based on measurements of1onmeasurements based formosuskaryotype, eontu longimembrus Perognathus 0 5 0 25 20 15 10 h ooo e NumberChromosome hoooe Number Chromosome eontu formosus Perognathus 2N=56 2N=36 40 30 45 35 055 50 86 Figure 17.— Composite Ideogram of the male Liomys plotustheLiomysofIdeogrammale Composite 17.— Figure Length (in mm.) 10-1 - 5 eahss X5200 metaphases. somatic10ofon measurements based karyotype, 0 5 0 5 30 25 20 15 10 hoo oe Number Chromosome ims pictus Liomys 2N=48 35 045 40 87 APPENDIX C The taxonomy of the g e m s Perognathus (after Hall and Kelson 1959) Orders Rodentla Suborders Sciuromorpha Family g He teromyIdae Subfamilyg Perognathinae Genusg Perognathus Subgenus fasciabus species group Perognathus flavus species group species group parvus altleola formosus species group Subgenus t Chaetodlpus species group hispidus species group hispldus species group iPerognathus arenarlus Perognathus oermix intermedius species group Perognathus Intermedius nelson! artus llneatus Perognathus fallax ^ californious species group californlcus eplnatus species group Perognathus spinatus APPENDIX D ______J. A. Allen Specimens examined8 total, 20 Sonorag Pinacate Lava Flows (4e3”^). Arizonas Tucson, Pima Co. (UA 105^5)= Specimens examinedg total, 3 Arizonag Floyd's Pocket, Lazy j Ranch, Cochise Co (26e4~49 I?j4"^2, l?j^>3)» J. A. Allen Specimens examinedg total, 5» Sinaloag 10 km. E. Pericos (26a5»17, 18, 20, 21, 22). P. 2 ° pernix-/g g Specimens examinedg total, 3= Nayaritg Playa de Novi He r o s (27a5"3$ 5)« intermedins intermedins Merriam Specimens examinedg total, 4. Arizonag Silverbell Mts Tucson, Pima Co. (27b4=l, 2, 2414"1)g Tucson Mts 0 9 Tucson, Pima Co. (1914=2). Perognathus Intermedins pinacate Blossom Specimens examinedg total, 5® Sonorag Pinacate Lava Flows (UA 10543, 13d3-l, 214=2, 9c4=l, 19g4). Perognathus fallax pallldus Mearns Specimens examinedg total, 2. Californiag 13 mi. E. Glamis, Imperial Go. (UA 10544, UA 10548). 90 Perognathus artus Osgood Specimens examinedg totalg 6 C Sinaloag 10 km, E. Peri do s (0A 12951# 1 2 9 6 W , 26a5-8, 11, 12). P. Koldmani- Specimens examinedg total, 2, Sonorag Plnaoate Lava Flows (4e3-2, 7d3~l), Perognathus formosus melano caudatus Cockrum Specimens examinedg total, 2, Arizonag Vulcan’s Throne, Toroweap Valley, Mohave Co., 4300 ft, (UA 12471, UA 12510). Liomys piotus £ic^us (Thomas) Specimens examinedg total, 2. Colimag 2 mi. SE Cihuatlan (Jalisco), (214-1, 2), Liomys pictus esoujnapae (J, A. Allen) Specimens examineds total, 2, Sinaloas 10 km. E Perioos (27a5-6, 7)» Liomys pjctus sonoranus Merriam Specimens examinedg total, 1, Sinaloag 5 A mi, ME El Fuerte (26k4»l4). LITERATURE CITED Agar9 W„ E. 1923. The male melotlc p h a s e in two genera of marsupials (Macropus and Petauroldes)0 Quart, Jour. Mldr. Sol. 6?il83”202. Anderson, S. 1964. The systematic status of Perognathus artus and Perognathus goldmanl (Rodent la )T™™™Sier, Mus, Nov, no^"2lW5. Bender, M. A., and E, H. Y. Chu. 1963. The chromosomes of . Primates. Ini Evolutionary and Genetic Biology of Primates, Vol. I, Ed. byi J. Buettner-Janusch. Academic Press, New York. pp. 261-310, Benlrschke, K.$ N. Malouf, R. J. Low, and H. Heck, 1965, Chromosome complementg differences between Equus oaballus and Equus przewalskll, Poliakoff. Science, Bovey, R, 1949, Les chromosomes des Ghlropteres et des Inseotlvores, Rev. Suisse Eool. 56s37l^^60. Cain, A, J. 1958, Chromosomes and their taxonomic impor tance, Pros. Linnean Soo, London, 169 session. pp. 125-128. Christensen, B., and C. 0. Neilsen. 1955. Studies on . Enchytraeldae, 4i Preliminary report on chromosome numbers of seven Danish genera. Chromosoma, 7:460-468. Chu, E. H, Y., and B. A, Swomley. 1961. Chromosomes of lemurlne lemurs. Science. 133s1925-1926, Crlppa, M. 1964, The mouse karyotype in somatic cells cultured in vitro. Chromosoma. 15*301-311. Cross, J. C. 1931. A comparative study of the chromosomes of rodents. Jour, Morph, 52s373-402. Darlington, G. D. 1939. Mlsdivision and genetics of the centromere. Jour, Genetics. 37*341-364. 93 94 Fords .0. 'B., and J. L. Hamerton. 1956. A eolchielne$ hypotbnio-dltrate, squash sequence for mammalian chromosomes. Stain Technology. 31s247-251. 8 J. L» Hamerton; and G. B. Sharman. 1957« Chromosome polymorphisms In the common shrew. Nature. 180(1)s392-393. Grlffen, A. B .9 and ¥„ S. Stone. 1940. The second arm of Chromosome IV In Drosophila melanogaster. Univ. Texas Publ. 4032s201-20?. Hall9 E. R., and K. R. Kelson. 1959. The Mammals of North America. Vol. I. Ronald Press Co., New York. PP. 473-507. " ■ I 0 and M. B. OgllTle. i960. ConspeolfIclty of two pocket mice, Perognathus goldmanl and P. artus. Univ. Kansas PublT*^9TT8'rTF^3-5l6. Kennerly, T. S., Jr. 1956^ Comparisons between fossil and fossil species of the genus Perognathus. Texas Jour. Sol. viiKDs 74-86. Klinger, H. P., J.L. Hamerton, D. Mutton, and B> M„ Long. 1963. The chromosomes of the Homlnoldea. Ins Classification and Human Evolution, Ed. by: S. Washburn. Wenner-Gren Found., Chicago, pp. 235-242. Leopold, A. S. 1950, Vegetation zones of Mexico. Ecology. 31(4)1507-518. Levan, A., T. G. Hsu, and H. P. Stich. 1962. The Ideogram of the mouse (Mus muscuius). Hereditas. 48(4)s 677-688. Makino, S. 1943. The chromosome complexes In goat (Capra hireus) and sheep (Ovls arles) and their relationship. Cytologia. 13$39^54. Matthey, R. 1951. The chromosomes of the vertebrates. Advances in Genetics. IVs159-180. . 1952. Chromosomes de Muridae (Mlcrotinae et Crieetinae). Chromosoma* 5»113-138. ' 1957. Cytologie comparee, systematique et phylogenle des Mlcrotinae (Rodentia-Muridae). Rev, Suisse Zool. 64g39-71. . 1963. Polymorphism© ohromosomlque intra- spoelflque et Intralndlvlduel chez Aqoiays ml no us Bate (Mammalla~Hodentia-Muridae), Etude cytologlque des hybrid©s Aoomys mlnous X Aeomys cahlrlnus 9 , Be mecanlsme des fusions oentrlques. Chromosoma, 1^ 1^68-^97 , May 1*9 E. 1963. Animal Species and Evolution. Harvard Unlv/ Press, Cambridge, Mass. Melander, t. 1963. A presumed obstacle to mammalian poly- ploidization. Nature. 1971152-153. Nadler, C. F. 1963. The application of chromosomal analysis to taxonomy of some North American Sciuridae. Proc. XVI Inter. Cong. Zool. 4:111-115. - 1964a. Contributions of chromosomal analysis to the systematlcs of North American chipmunks. Amer. Midland Natur. 72(2)1298-312. - 1964b. Chromosomes and evolution of the ground squirrel, Spermophllus rlchardsonli. Chromosoma. 15s289-299. ' " . 1964c. Chromosomes of the Nevada Ground Squirrel. Spermophllus rlchardsonli nevadensls. Proc. Soc. Exp. Bib;"an! Med“ Ohnos S., C. Stenius, L. C, Christian, ¥. Beoak, and M. L. Beoak. 1964. Chromosomal uniformity In the avian subclass Carinatae. Chromosoma. 15?280-288. Osgood, ¥. H„ 1900, Revision of the pocket mice of the genus Perognathus. North Amer. Fauna, 18(4)sl-65. Patterson, J. T., and ¥,S. Stone., 1952. Evolution in the Genus Drosophila. Macmillan, New York. Rhodes9 M. M, 1940, Studies on a telocentric chromosome in maize with reference to the stability of its centro mere. Genetics. 24:62-63. Robertson, ¥. R. B, 1916. Chromosome studies. I. Taxonomic relationships shown in the chromosomes of Tettigidae. and Acrididae. V-shaped chromosomes and their sig nificance in Acrididae, Leeustidae, and Gryllldae: chromosomes and variation. Jour. Morph, 27:179-331. 96 Sch6rz9 H. Go 1962. Blaze^drylngi toy igniting the flz-» stive, for improved spreads of ehromosomes in leuco cytes. Stain feohtoelogy* 3?8366. Shaman, G. B. 1956. Chromosomes of the common shrew. Nature„ 19729^1-9^2.. Stetotoins, G. L.s Jr. 1950. Variation and Evolution in Plants. Columbia Univ. Press, New York* Stone, W. S. 1949.. The survival of chromosomal variation in evolution. Univ. Texas Putol. 4920s18^21. 1962. The dominance of natural selection and the reality of super species (species group) in the evolution of Drosophila. In? Studies in Genetics. Univ. Texas„ pp. 507-538» Swanson, C, P. 1957. Cytology and Cytogenetics, Prentioe-Hall Inc., New Jersey. :Totoias, P. V. 1953. Trends in the evolution of mammalian chromosomes. S. African Jour. Sci. 501134-140, 1956. Chromosomes, Sex-Cells, and Evolution in a Mammal. Percy Lund, Sumphrles and Co., Ltd., London. Wahrman, J., and A. Zahavi,'. 1955. Cytologieal contri butions to the phylogeny and classification of the rodent genus Gertolllus. Nature. 175(2)?600-602. . White, M. J. D. 1935. The effect of X-rays on the spermato,- gonial divisions in Locasta mlgratorla. Proc, Boy, Soc. B*.. 119s6l-84. . 1946. The evidence against polyploidy.in sexually-*reproducing animals. Amer, Nat. 80g6l0*-6l9. 1954. Animal Cytology and Evolution Univ. Press, Cambridge. Wood, A. E. 1935, Evolution and relationship of the Hetero- myid rodents. Ann. Cam. Bus, XXIVi73-262. Zahavi, A., and J, Wahrman, 1956. Chromosome races in the genus Acomys (Rodentlas Eurinae). Bull, Res, Couno, Israel7~lfBT3~4) 016.