This dissertation has been 64-6927 microfilmed exactly as received

LENGEL., Patricia Ann, 1930- A BIOSYSTEMATIC STUDY OF SILPHIUM INTEGRIFOLIUM MICHX., S. SPECIOSUM NUTT., AND S. ASPERRIMUM HOOK.

The Ohio State University, Ph.D., 1963 Botany

University Microfilms, Inc., Ann Arbor, Michigan A BIOSYSTEMATIC STUDY OP SILPHIUM INTEGRIFOLIUM MICHX.,

S. SPECIOSUM NUTT., AND S. ASPERRIMUM HOOK.

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

Patricia Ann Lengel, B. A., M. Sc

******

The Ohio State University 1963

Approved by

Adviser Department of Botany and Plant Pathology ACKNOWLEDGMENT

I would like to acknowledge gratefully the help of

Dr. T. Richard Fisher, my adviser, whose ideas and criticisms have brought this investigation to its present state. I would also like to thank Drs. Clara

Weishaupt, Elton P. Paddock, and Adolph E. Waller for their critical analyses of this manuscript.

ii TABLE OP CONTENTS

Page

ACKNOWLEDGMENT...... 11

LIST OF TABLES...... Iv

LIST OP ILLUSTRATIONS...... T ...... v

GENERAL GEOGRAPHIC DISTRIBUTION ...... 1

TAXONOMY...... 5

GENERAL MORPHOLOGY ...... 6

ARTIFICIAL HYBRIDIZATION AND CYTDLOQICALMETHODS . . . 8

CYTOLOGICAL OBSERVATIONS...... 20

Species ...... 20 Interspecific crosses Involving Sllphlum Integrlfollum...... 20 Other Interspecific crosses of Sllphlum ...... 30 Intraspeclflc crosses InvoIvlng Sllphimi Integrifollum ...... -...... 36 Backcrosses Involving the Interspecific hybrids of Sllphlum ...... 37 Pi sibling crosses of Sllphlum...... 38

VARIATION STUDIES IN SILPHIUM INTEGRIFOLIUM, S. SPECIOSUM, AND S7 ASPERRlHDH ...... 39

MORPHOLOGY OP THE ARTIFICIAL INTERSPECIFIC HYBRIDS INVOLVING SILPHIUM INTEGRIFOLIUM...... 6l

DISCUSSION AND CONCLUSIONS ...... 64

TAXONOMIC CONSIDERATIONS...... 72 SUMMARY ...... 76

LITERATURE CITED ...... 79

AUTOBIOGRAPHY...... 82

111 LIST OP TABLES Table Page

1. Voucher material sources and chromosome numbers of Sllphlum used In this study .... 11

2. Percentage of seed-set and germination of Inter- and Intraspeclflc crosses In S l l p h l u m ...... 13

3. Percentage of seed-set on Pn or Pi and germination after backcroSslng In Slllphlum...... 15

4. Percentage of seed-set on Ft plants which have been pollinated by sister Pi plants and germination of resulting seeds In S l l p h l u m ...... Id

5. Percentage of pollen stalnablllty and melotlc behavior In Pi Interspecific hybrids of Sllphlum ...... 18

6. Means and standard deviations of the measure­ ments of herbarium specimens from Individual quadrats ...... 42

7. Means and standard deviations from Table 6 rearranged Into arcs emanating southwest and northeast of the Ozark P l a t e a u ...... 46

8. Means and standard deviations from Table 6 rearranged Into arcs emanating southeast and northwest of the Ozark P l a t e a u ...... 49

9. Morphological analysis of reciprocal Pi Interspecific hybrids Involving Sllphlum Integrifollum and other species ...... 62

Iv LIST OP ILLUSTRATIONS Figure Page 1. Distribution of Silphium integrlfolium...... 2 2. Distributions of Silphium speclosum and S. asperrimum...... 3 3. Diakinesis in Silphium integrifolium...... 21 4. Diakinesis in Silphium asperrimum...... 21 5« Diakinesis in Silphium sp e c l o s u m ...... 21 6. Diakinesis in Silphium simpsonii var. w r i g h t i i ...... 21 7. Diakinesis in Sllphlum reverchoni ...... 23 8. Diakinesis in Silphium integrifolium x S. speclosum...... ; . . . 23 9. Diakinesis in Silphium speclosum x S. integrifolium...... 23 10. Diakinesis in Silphium integrifolium x S. asperrimum...... 24 11. Interpretation of Figure 1 0 ...... 24 12. Diakinesis in Silphium asperrimum x S. integrifolium ...... 24 1 3. Interpretation of Figure 1 2 ...... 24 14. Diakinesis in Silphium reverchoni x S. integrifolium...... 23 1 5 . Interpretation of Figure 1 4 ...... 25 1 6. Diakinesis in Silphium integrifolium x £. simpsonii var. wrigKtii ...... 25 1 7. Interpretation of Figure I6 ...... 25

V LIST OF ILLUSTRATIONS— continued

Figure Page 18. Diakinesis in Silphium simpsonii var. wrightii X S. Integrifollum ...... 26

19. Interpretation of Figure 1 8 ...... 20. Diakinesis in Silphium integrifolium x S. simpsonii var. wrifàitii......

21. Interpretation of Figure 20 ......

22. Bridge in Silphium speciosum x S. integrifollum ......

23. Bridge in Silphium asperrimum x^S. integrifolium......

24. Bridges in Silphium integrifolium x S. simpsonii var. wrightii ......

25. Bridge in Silphium simpsonii var. wrightii x S. integrifolium ...... 28

26. Bridge in Silphium simpsonii var. wrightii x S. integrifolium ......

27. Bridge in Silphium reverchoni x S. integrifolium......

28. Interpretation of a lagging chromosome in Silphium integrifolium x S. simpsonii var. wrightii ......

29. Lagging chromosomes in Silphium reverchoni x S. integrifolium......

30. Diakinesis in Silphium speciosum x S. reverchoni ......

31. Interpretation of Figure 30 ...... 32. Diakinesis in Silphium asperrimum x S. speciosum......

Vi LIST OP ILLUSTRATIONS— continued

Figure Page

33. Interpretation of Figure 32 ...... 31

34. Diakinesis in Silphium speciosum x S. a s pe r r i m u m ...... 32

35. Interpretation of Figure 34 ...... 32 36. Diakinesis in Silphium trifoliatum x S. speciosum...... 32

37. Interpretation of Figure 3 6 ...... 32 38. Diakinesis in Silphium trifoliatum x a s perri mum...... 33

39. Interpretation of Figure 3 8 ...... 33

40. Diakinesis in Silphium trifoliatum x S. asp er r i m u m ...... 33

41. Interpretation of Figure 40 ...... 33

42. Diakinesis in Silphium asperrimum x S. trifoliatum...... 34

43. Interpretation of Figure 4 2 ...... 34

44. Diakinesis in Silphium asperrimum x S. reverchoni "...... 34

45. Interpretation of Figure 4 4 ...... 34

46. Diakinesis in Silphium speciosum x S. perfoliatum...... 35

47. Diakinesis in Silphium simpsonii var. wrightii X S. speciosum...... 35

48. Diakinesis in Silphium speciosum x S. simpsonii var. wrigHtil ...... 35

49. Interpretation of Figure 4 8 ...... 35 vii LIST OP ILLUSTRATIONS— continued

Figure Page

50. Method in studying regional variation northeast to southwest ...... 45

51. Method in studying regional variation northwest to southeast ...... 48

52. Regional variation from northeast to southwest of head s i z e ...... 50

53» Regional variation from northwest to southeast of head s i z e ...... 50 54. Regional variation from northeast to southwest of length/width ratio of achene . . . 53

55. Regional variation from northwest to southeast of length/width ratio of achene . . . 53

56. Regional variation from northeast to southwest of achene length ...... 55

57. Regional variation from northwest to southeast of achene length ...... 55

58. Regional variation from northeast to southwest of length/width ratio of achene notch ...... 57

59» Regional variation from northwest to southeast of length/width ratio of achene notch ...... 57

60. Regional variation from northeast to southwest of depth of achene notch ...... 58

61. Regional variation from northwest to southeast of depth of achene notch...... 58

62. Regional variation from northeast to southwest of width of achene wing ...... 60

viii LIST OF ILLUSTRATIONS— continued

Figure Page

63. Regional variation from northwest to southeast of width of achene w i n g ...... 60

64. Cytogenetic relationships between all species of Silphium included in this study...... 65

65. Cytotaxonomic relationships of the "integri­ folium" complex...... 75

ix GENERAL GEOGRAPHIC DISTRIBUTION

The range of Sllphlum Integrifollum Mlchx. (Figure 1) extends Into Indiana, west Into Kansas, southwest Into

Texas, southeast Into Georgia, and n'orth Into Wisconsin— an area which closely coincides with the Tall-grass prairie region of the United States, Unlike this very broad distri­ bution, S. speclosum Nutt, and S. asperrimum Hook, have very limited ranges which nevertheless overlap the western and southwestern edges of the range of S. Integrifollum. The range of S. speclosum (Figure 2) extends from Nebraska, south

Into Texas, and northwestern Arkansas. Sllphlum asperrimum

(Figure 2) ranges from eastern Oklahoma Into Texas and south­ western Arkansas. Sllphlum speclosum and S. Integrifollum are sympatrlc In Kansas and Oklahoma, while S. asperrimum and S. Integrifollum are sympatrlc In Oklahoma, Texas, and

Arkansas. Sllphlum speclosum and S. asperrimum both grow

In southern Oklahoma, Texas, and western Arkansas.

Since there Is considerable variation In S. Integrifollum and since the ranges of S. speclosum and S. asperrimum over­ lap the western and southwestern extensions of 8_. Integrifo­ llum, the possibility of natural hybridization and Inter- gradatlon between S_. Integrifollum and S. speclosum In one area and between Integrifollum and S. asperrimum In 1 • #1 o o o#

• •

p ♦

Figure 1.— Distribution of Silphium integrifolium; each symbol represents a single county record. Solid circle, . hirsute taxon (var. Integrifolium]; open circle, glandular taxon (var. deamii) X, glamorous taxon (var. gattingeri); glyph on circle, pilose taxon (var. shelbii). o o #o

Figure 2.— Distributions of Silphium asperrimum and speciosum; each symbol represents a single county record. Open circle, S. asperrimum; solid circle, S. speciosum. 4 another area Is great. The representatives of S. integrifo­ llum in Arkansas and Tennessee are entirely unlike those in other parts of the range in regard to pilosity of the leaves, stems and phyllaries. In order to study the possibility that the pilosity is an environmentally induced character­ istic, representative plants with pilose phyllaries were planted together with representatives of other phyllary types in a common environment at The Ohio State University research garden.

Two other species, S. simpsonii Bush and S. reverchoni

Bush, grow within the southern range limits of S. integrifo­ lium. Silphium simpsonii is found in the area ranging from

Florida to Texas, while S. reverchoni is confined to a small area in eastern Texas and western Louisiana. To the east of the range of integrifolium is S. trifoliatum L., while to the east and almost completely sympatrlc with S. integrifo­ lium is S^. perfoliatum L. (Cruden, i960). Representatives of all these— 8. simpsonii, S. reverchoni, and S. perfoliatum

— were planted in The Ohio State University research garden. TAXONOMY

Flora Boreall"Americana (1803), which had been prepared by Andre Michaux, was published during the year following his death and edited by L. C. M. Richard. In this work,

Michaux described Silphium integrifolium. Torrey and Gray

(1843) described as S. integrifolium var.y£ laeve what is now regarded as S. speciosum. In 1932, after a trip to his hometown of Claflin, Kansas, H. C. Benke described as a new

variety a group of plants which may well be the putative hybrids of S^. integrifolium and S. speciosum. Benke named

this group, S. integrifolium var. mesochorum.

Lily M. Perry (1937) designated as varieties of S. in­

tegrifolium (Figure 1) two morphological races; var. gattingeri, which is particularly characterized by glabrous

phyllaries, and var. deamii, which has glandular-pubescent

phyllaries. Perry, however, neglected to delineate as a

variety the taxon which resembles the typical S. integrifo­

lium. Cronquist then in 1945 designated this group as S.

integrifolium var. integrifolium (Figure 1). In the present

study, a taxon which is characterized by pilose-pubescent

phyllaries will be named var. shelbii.

Silphium asperrimum was described by Hooker in I835,

and in 1841 S. speciosum was described by Thomas Nuttall.

5 GENERAL MORPHOLOGY

Sllphlum Integrifollum Is characterized as perennial herbs growing In dense clumps about 1 1/2 to 2 meters In height. Sessile leaf blades are alternately or oppositely arranged growing high on angular usually hispid stems.

Sometimes this hispid quality Is observable only on the peduncles. Margins of thé leaf blades are variously toothed or entire, even on the same Individual. The 15-18 mm. wide heads of much branched peduncles are subtended by Involucres of follaceous phyllaries. Phyllaries have outer surfaces varying from glabrous to glandular-pubescent to hairy- pubescent (hirsute or pilose). In the majority of the plants, phyllaries are either glandular-pubescent or hairy pubescent; plants with glabrous phyllaries are relatively rare (Figure 1). Achenes vary from 7 to 9 ram. In length and have teeth about 2 to 2.5 mm. long.

C. C. Deam (1940) described S. Integrifollum In Flora of Indiana as follows :

TSie plants are variable In width and margins of the leaves and In the pubescence of the stem, leaves and Involucre. Some plants have stems with a few temate or alternate leaves. The Inner face of the achenes Is either glabrous or pubescent, mostly more or less pubescent. 7 Much more striking in its individuality is speciosum.

Clones of plants are not as dense as those of S. integri­ folium. Stems and peduncles are glaucous and straw- colored while the phyllaries are glabrous except for the ciliate margins. Heads and achenes are larger than those of

S. integrifolium. Peduncles are relatively unbranched and give a spike-like appearance to the plants in flower.

Silphium asperrimum is a much coarser herb in aspect than either S. speciosum or S. integrifolium. Although having much the same growth form as S. speciosum, its stems, peduncles, leaves, and phyllaries are covered with coarse hairs. Its heads are fewer and larger than those of

S. integrifolium or S.' speciosum. ARTIFICIAL HYBRIDIZATION AND CYTOLOGICAL METHODS

A hybridization program involving S. integrifolium,

8. speciosum, S. asperrimum, S. simpsonii, S. reverchoni,

S. trifoliatum, and S. perfoliatum, all diploid species,

is being undertaken. Some results of this program are to be discussed in this paper.

Inter- and intraspecific crossing in Silphium is

relatively easy because all species investigated to date

are self-sterile. The plants used as parents were collected

from natural habitats and transplanted to the research

garden at The Ohio State University (Table 1).

Each inflorescence is composed of monosporangiate ray

flowers producing only ovules and monosporangiate disc

flowers producing only pollen. Each head was covered with

a glassine bag before the flowers of the head open. At the

time that the anthers were mature, i.e., emergent from the

disc flowers, some of the staminate flowers were removed as

a source of pollen. By means of tweezers, the anthers were

brushed across the stigmas of the ovulate flowers of a head

of the plant chosen as the ovulate parent. After pollination,

glassine bags were replaced until the ray flowers in the

head faded— about ten to fourteen days following pollination.

VIhen the flowers had faded, glassine bags were replaced with 8 9 cheesecloth bags which remained over each head until the head was harvested following the first frost.

Each fruit in an inflorescence was checked for plumpness which is used as an indication of seed-set (viability).

Percentage of seed-set was calculated after dividing the average number of plump achenes by the average total number of achenes. This was used as a measure of the degree of fertility of the cross (Tables 2, 3 and 4). Most crosses attempted were successful in that they set seed. In Tables

2, 3, 4 and 5, the pollen parent is always mentioned first in listing a cross. The fruits were stored for eight weeks at 38°P. after which they were potted in moist soil and placed out-of-doors for six weeks of freezing and thawing temperatures. After this period of cold treatment, the pots of achenes were brought into the greenhouse; the seeds within the achenes germinated in less than one week.

Germination percentage was calculated by dividing the average number of seeds which germinated by the average number of plump achenes (Tables 2, 3 and 4). Three-month-old seedlings were transplanted to the research garden where most of them flowered during the first summer in the research garden.

Inflorescence buds were placed in a 3:1 mixture of 95^ ethyl alcohol and glacial acetic acid for twenty-four hours after which they were transferred to 70^ ethyl alcohol and refrigerated. Chromosome activity during microspo.rogenesis was subsequently studied in all the hybrids. Temporary 10 mounts were made by squashing anthers in iron acetocarmine,

Photographs and camera lucida drawings of noteworthy cells were made at 1125 X.

Permanent mounts which were made with Hoyer's Medium

(Seeks, 1955) were not satisfactory in this investigation, because anther cells of Silphium could not be squashed flat enough for photographic purposes.

Pollen stainability as studied by the cotton blue- lactophenol method was used in this study as an indication of pollen viability. Counts were based on 100-200 pollen grains from each head. Pollen stainability data and details of meiotic behavior are listed in Table 5 . 11 TABLE 1.— Voucher material sources and chromosome numbers of Silphium used in this hybridization study. Numbers in parentheses are Hie Ohio State University research garden numbers

Meiotic Source of living Species chromosome material number* 8. integrifolium White Co., Ind. (73)» Fisher MichxT 624; Coles Co., 111. (147-148, 160), Fisher s.n.; Lawrence Co., 111. (2084), Fisher s.n.; Iroquois Co., 111. (162), L. R. Heckard 1021; Shelby Co., Tenn. (219), J. Beatley 25998; White Co., Ark. (276), Fisher 2038. S. asperrimum Hook. Rogers Co., Okla. (52), C. B. Reiser 4106; Lincoln Co., Okla. (275), Fisher 2041; Dallas Co., Tex. (2111), R. Cruden 685; Dal­ las Co., Tex. (8 9), L. Shin- ners s.n.; Kenefic Co., Tex. (2 1 1 2), R. Cruden 6 6 7. S. speciosum Nutt, Lyon Co., Kan. (I6I), R. L. McGregor 14170; White Co., Ark. (2 0 3), D. Demaree 39664. simpsonii Bush Evangeline Parish, La. (19-2 0), C. B. Reiser 4010; Calcasieu Parish, La. (8 5), L. Shinners 21215. S. simpsonii var. Jefferson Davis . Parish, wrightii Gr<. me La. (84), L. Shinners 21444.

S. reverchoni Bush Harrison Co., Tex. (9 0), L. Shinners 24159» 12

TABLE 1.— continued

Meiotic Source of living Species chromosome material number*

S. trifoliatum L. 7 Madison Co., Ohio (105), Fisher s.n.; Rutherford Co., N.C. (134), A. E. Radford s.n.

S. perfoliatum L. 7 Rutherford Co., N.C. (72), A. £. Radford s.n.

The meiotic chromosome number was established for every plant used in this study. 13 TABLE 2.— Percentage of seed-set and germination of inter- and intraspectific crosses of Silphium» The number following each species is The Ohio State ünlveracity research garden- number.

Percentage Cross Seed- Qermi- set nation (integrifolium-148 x speciosum-l6l) 38 9

(integrifolium-73 x speciosum-l6l) «*

(speciosum-161 x integrifolium-148) 73 20 (integrifolium-148 x asperriraum-89) 63 32

(asperrimum-89 x integrifolium-148) 53 10 (integrifolium-148 x simpsonii var. wrightii-d4 i 57 23 (sintt)sonii var. wrightii x integri­ folium-148) ■ 80 39 (integrifolium-148 x reverchoni-90) 21 5 (reverchoni-90 X integrifolium-148) 52 8

(integrifolium-148 x trifoliatum-134) 77 very low

(trifoliatum-134 x integrifolium-148) 79 very low (simgsonii var. wrightii-84 x speciosum- * *

(speciosum-161 x simpsonii var. wr£gTim-84) ' ' "" * *

(asperrimum-89 X reverchoni-90) * *

(speciosum-161 X asperrimum-89) **

(asperrimum-89 X speciosum-161) * *

(asperrimum-89 X trifoliatum-105) « * (speciosum-161 x trifoliatum-105) * * 14

TABLE 2.— continued

Percentage Seed- Germi- Cross Set nation (trifoliatum-105 x speciosum-l6l) ■' * * (speciosum-161 X perfoliatum-7 2 ) « *

(integrifolium-148 x integrifolium-219) 69 27 (integrifolium-219 x integrifolium-148) 88 43

(integrifolium-148 x integrifolium-276) 50 7+

.. , ------' ------_ - ■ _ not available. 15 TABLE 3»— Percentage of seed-set on P]_ or and germination after backcrossing in Silphium. The number following is The Ohio State University research garden number

Percentage Backcross Seed- Germi- set nation (asperrimum-89 X sp3ciosum-l6l) X speciosum-Ibl 72 78 speciosum-161 X (asperrimum-89 X speciosum-151) 35 99 (asperrimum-89 X speciosum-161) X asperrimum-b9 87 100 asperrimum-89 X (asperrimum-89 X speciosum-161) 31 73 (speciosuia-161 X asperrimum-89) x speciosum-161 46 62

(specio8um-l6l x asperrimum-89) x asperrimum-69 71 94 asperrimum-89 X (speciosum-161 X asperrimum-69) 53 72 (asperrimum-89 X reverchoni-90 ) X asperrimum-69 63 89 asperrimum-89 X (asperrimum-89 X reverchoni-90) 36 88 .

(integrifolium-73 x speciosum-I6I) x integrifollum-73 70 26 integrifolium-73 x (integrifolium-73 x speciosum-lbl) 2 100 speciosum-161 X (integrifolium-73 x speciosum-161) 66 93 speciosum-161 x (speclosum-I6I x integrlfolium-73) 79 74 asperrimum-89 X (asperrimum-89 X Integrifolium-73) 19 100 16

TABLE 3»— continued

Percentage Backcross Seed- Germl- set nation (sln®sonii var. wripht11-84 x specloaum-lSl) X sirapsonll var. wrlghtll-ü4 39 63 slmpsonll var. wrl^çhtll-84 x (sirapsonll var. wrlKhtll-84 X specioBura-lbl) 11 40

(sirapsonll var. wrlghtll-84 x speclosum-l6l) X speclosum-lbl 58 65 speclosura-l6l x (sirapsonll var. wrlghtll-84 X speclosura-lbl) 12 66 lntegrlfollura-148 x (asperrlraum-89 x integrifolium-i4b) 19 40 (asperrlraum-89 X lntegrlfollura-148) x asperrlmura-b9 0 0 asperrlmum-89 X ( asperrlmum-89 X integrlfollum-148) 32 66 (lntegrlfollura-148 x asperrlraum-89) x asperrlraura-ü9 40 86 asperrlmura-89 X (lntegrlfollura-148 x asperrlraum-89 ) 58 71 (lntegrlfollura-148 x asperrlraum-89) x Integrlfoilum-14b 38 0

lntegrlfollura-148 x (lntegrlfollura-148 x asperrlraura-bg) 37 0 (lntegrlfollura-148 x reverchonl-90) x Integrlfoliura-14b 58 14

lntegrlfollura-148 x (lntegrlfollura-148 x reverchoni-90) 0 0

(sirapsonll var. wrlghtll-84 x Integrlfollura- 140) X integrlfoliura-l40 ,4 33 17 TABLE 3»— -continued

Percentage Backcross Seed- Germl- set nation lntegrlfollum-148 x (slmpsonll var. wrightll-ü4 X lntegrlf*olium-l48) 7 0 slmpsonll var. wrlphtll-84 x (slmpsonll var. wrlghtll-84 x iritegrirolium-14di 11 100

(slmpsonll var. wrlghtll-84 x Integrlfo- llum-14ü) X slmpsonll var. wrlghtll-84 0 0

(Integrlfollum-148 x slmpsonll var. wrlphtll-84) X Integrlfollum-148 46 75 slmpsonll var. wrlghtll-84 x (Integrlfo- llum-l4d X slmpsonll var. wrlghtll-84) 0 0

(Integrlfollum-148 x slmpsonll var. wrlghtll-ü4) X slmpsonll var. wrlghtll-84 8 0

Integrlfollum-148 x (Integrlfollum-148 X slmpsonll var. wrlghtll-ü4) 0 0 18 TABLE 4.— Percentage of seed-set on plants which have been pollinated by sister Pn plants and germination of the resulting seeds in Sllphium. The number following each species is The Ohio State' Üniversity research garden number

Percentage Pi Sibling Crosses Seed- Germi- set nation (asperrimum-89 x speciosura-l6l) 60 92 (speciosum-l6l x asperrimum-89) 37 46 (speciosum-l6l x integrlfolium-73) 91 70 (simpsonii var. wrightii-84 x integ- rirolium-14b) 1 0 (integrlfolium-148 x simpsonii var. " wfîghtn-8'4 ) ' .. . 13 0 (asperrimum-89 x integrlfolium-73) 0 0 ■ (asperrimum-89 X integrlfolium-148) 0 0 ( integrlf olium-148 x asperrimum-89) 38 0

TABLE 5«— Percentage of pollen stainability and raeiotic behavior in P% interspecific hybrids of Silphium. The number following each species is The Ohio State University research garden number

Percent- age Pollen Meiotic P^ Interspecific Hybrid Staina­ Behavior bility ( integrlf olium-73 x speciosum- 96-100 7 II;melotic sequence normal C speciosum-l6l x integrlfolium- 100 7 II;meiotic sequence normal ( integrlfolium-148 x asperrimum- 68-70 5 II, chain of 4 19 TABLE 5»— continued

Percent­ age Pollen Meiotic F-|L Interspecific Hybrid Staina­ Behavior bility (as^errimum-89 x integrlfolium- 61-68 5 II, chain of 4

(integrlfolium-148 x simpsonii 72-80 5 II, chain of 4; var. wrightii»d4) 5 II, ring of 4; laggards, anaphase II (simpsonii var. wrightii-84 x integrifolium-14Üj 56-67 5 II, chain of 4 (integrlfolium-148 x reverchoni- 9'ôr ■ ...... 73-76 5 II, chain of 4 (reverchoni-90 x integrifolium- 47 5 II, chain of 4; laggards, ana­ phase I (simpsonii var. wrightii-84 x 100 7 II, meiotic speciosum-lbl) sequence normal (speciosum-l6l x simpsonii var. wrightii-ü4) 67-68 5 II, chain of 4 (asperrimum-89 X reverchoni-90) 100 7 II; meiotic sequence normal (speciosum-161 X.reverchoni-90) 75 5 II; chain of 4 (speciosum-161 X asperrimum-89) 44-81 5 II, chain of 4 (asperrimum-89 X speciosum-161) 80-100 5 II, chain of 4 (asperrimum-89 X trifoliatum-105) * 5 II, chain of 4

(trifoliatum-105 X speciosum-161) * 7 II; meiotic sequence normal (speciosum-161 X perfoliatura-7 2 ) * 7 II; meiotic sequence normal Data unavailable. CYTOLOOICAL OBSERVATIONS

Species

The cytology of Sllphium Integrlfollum has been

Investigated by several workers— Merrell (I900), Land (1900), Taylor (I926), and Fisher and Cruden (I962). The two early workers ascertained n = 8 , but In the two later reports, the number was well documented to be n = 7 and 2n = 14. All the species which were used In the cytotaxonomlc studies In the present Investigation have good dlaklnetlc pairing of fourteen chromosomes (Table 1, Figures 3, 4, 5 , 6 , and 7 ).

Also the meiotic behavior subsequent to dlaklnesls Is normal.

Interspecific crosses Involving Sllphium Integrlfollum

Five species— Sllphium speclosum, 8 . asperrlmum, S. slmpsonll var. wrlghtll, S. reverchonl, and S. trlfollatum— whose ranges overlap that of S. Integrlfollum were crossed reciprocally with S. Integrlfollum and all ten possible combinations were achieved. These hybrids with the excep­ tion of the two Involving 8^. trlfollatum which have not yet flowered are fertile as Indicated by pollen stainability

(Table 5 ). The details of meiotic behavior described here

2 0 2 1

i '-, V .•.r-o,, . ' '-' •.. r - ,., -à

Figure 3»— Seven pairs of Figure 4.— Seven pairs of chromosomes during diakinesis chromosomes during diakinesis in Silphium integrlfollum in Silphium asperrlmum Hook. 10[cH x TOTT

f

Figure 5.— Seven pairs of Figure 6.— Seven pairs of chromosomes during diakinesis chromosomes during diakinesis in Silphium speclosum Nutt. in Silphium simpsonii var. — — T ® r — wriihîïïwrigi ISFeene"— (84). 22 were based upon the examination of many cells from many anthers of several heads of each hybrid (Table 5).

The meiotic variability ranges from good pairing of

chromosomes in the hybrids between S. integrifolium and S.

speciosum (Figures 8 and 9) to five pairs of chromosomes and one chain of four in the hybrids between S. integrifolium and S. asperrimum (Figures 10, 11, 12, and 13) and between

S. integrifolium and S. reverchoni (Figures 14 and 15). Ohe chain of four chromosomes apparently involves the two largest pairs of the seven pairs of chromosomes. Between the two middle chromosomes, there is a persistent loop, very much resembling an inversion loop. It is presumed that this loop is created by one terminalizing chiasma and one non-terminalizing chiasma. There are also late-terminaliz- ing chiasmata associated with the two end chromosomes of the chain. There is more variability in the hybrids between

S. integrifolium and S. simpsonii var. wrightii than in any of the others. Five pairs of chromosomes and one chain of four is the regular configuration in both 8. integrifolium

X S. simpsonii var. wrightii (Figures l6 and 17) and S. simpsonii var. wrightii x S^. integrifolium (Figures l8 and

19). However, an exception of a ring of four chromosomes rather than a chain was observed twice in S. integrifolium

X S. simpsonii var. wrightii (Figures 20 and 21).

When bridges are observed, they may be due to "sticky" chromosomes which are slow in disjoining during anaphase. 23

Figure 7 .— Seven pairs of Figure 8.— Seven pairs of chromosomes during diakinesis chromosomes during diakinesis in Silphium reverchoni Bush in Silphium integrifolium x (90). S. speciosum.

Figure 9 .— Seven pairs of chromosomes during diakinesis in Silphium speciosum x S . integrlfollum. 24

Figure 10.— Five pairs of Figure 11.— Interpreta­ chromosomes and a chain of tion of Figure 10. four during diakinesis In Sll­ phium Integrlfollum x 8. as- perrlmumT"

»

Figure 12.— Five pairs of Figure 13.— Interpreta­ chromosomes and a chain of tion of Figure 12. four during dlaklnesls In Sil­ phium asperrljnum x 8. integrl- folium. 25

li % w 0 Mgii

'#

Figure 14.— Five pairs of Figure 15.— Interpreta­ chromosomes and a chain of tion of Figure 14. four in Silphium reverchoni X S. integrlfollum.

)#

Figure l6.— Five pairs of Figure 17.— Interpreta­ chromosomes and a chain of tion of Figure 16. four during diakinesis in Sil­ phium integrifolium x S. simpsonii var. wrightiT. 2 6

%

Figure 18.— Five pairs of Figure 19.— Interpreta­ chromosomes and a chain of tion of Figure 18. four during diakinesis in Sil­ phium simpsonii var. wrightii X S. integrifolium.

#

Figure 20.— Five pairs of Figure 21.— Interprets- chromosomes and a ring of four tion of Figure 20. during diakinesis in Silphium integrifolium % S. simpsonii var. wrightii. 27 81 is reported by Cruden (i960), rather than to inversions.

Another obvious possibility is that the middle non-termina­ lizing chiasma of the chain of four holds the two chromosomes together until at least anaphase I. It is very difficult to distinguish bridges resulting from chromosomes slow in dis­ joining from those due to inversion bridges except that the latter are accompanied by fragments of chromosomes. Such inversion fragments are expected to have a length at least equivalent to the circumference of the loop and so should , have been easy to see in the present instances. However, no fragments were seen. Bridges can be observed in anaphase I

(Figures 22, 25, and 27), anaphase II (Figures 24 and 26), and at times the bridge formed during anaphase I persists through anaphase II (Figure 23). The bridge in Figure 22 could not be due to a non-terminalizing chiasma, because in that F]_ hybrid, good pairing of chromosomes occurred during diakinesis. At times, entire chromosomes are left at the metaphase plane long after the others have moved to the poles. This phenomenon was observed during telophase II in the hybrids,

S. integrifolium x S. simpsonii var. wrightii (Figure 28) and S. reverchoni x S. integrifolium (Figure 29). 2 8

a

Figure 22.--Bridge in Figure 2 3 .— Bridge in Sil- Silphium speciosum x 8. phlim asperrimum x 8. integri- integrlfollim during rolium during anaphase Ï per­ anapnase 1 of meiosis. sisting through anaphase II of meiosis. Configuration at bottom is in mitotic metaphase.

Figure 2^.— Bridges in Figure 2 5 .— Bridge in Silphium integrifolium x 8. Silphium simpsonii var. simpsonii varT wrightii wlghtii' X s. integrifolium during anaphase ïi of during anapïïase I of meïosis meiosis. 29

IS

Figure 2 6 .— Bridge in Sil- Pigure 2 7 .— Bridge in 8il- reverchoni x integri- anaphase”! or

/

4 • 9 4 #

Figure. 2&.--Interpretation Figure 2 9 .— Lagging chromo­ of a lagging chromosome in somes in ^ilphlum reverchoni Silphium integrifolium x 8 . X 8. integrifolium. simpsonii varT wrightii. 30 Other Interspecific crosses of Silphium*

Silphium speciosum, S. asperrimum, S. simpsonii var. wrightii. and 8. reverchoni have geographically distinct

ranges except in northeastern Texas and northwestern

Louisiana where they are sympatric. Silphium trifoliatum and S. perfoliatum, even though they do not grow in the ranges of the species mentioned above, were used in addition to the other species to aid in the understanding of interspecific relationships. The interspecific hybrids involving these six species were fertile (Table 5).

Most of these interspecific hybrids have a meiotic configuration of five pairs of chromosomes and a chain of four (Figures 30 through 35 and 38 through 43). Silphium trifoliatum x S. speciosum (Figures 36 and 37), S. asper­ rimum X 8. reverchoni (Figures 44 and 45), and S. specio­ sum X S. perfoliatum (Figure 46) have regular pairing of all chromosomes. Silphium simpsonii var. wrightii x speciosum has regular pairing of all chromosomes (Figure 47) while its reciprocal has five pairs and a chain of four

(Figures 48 and 49). These two reciprocal crosses are not necessarily from the same two parent individuals.

■»------Crosses made by R. W. Cruden and T. R. Fisher. 31

Figure 3 0 .— Five pairs of Figure 3 1 . — Interpretation chromosomes and a chain of of Figure 30 . four during diakinesis in Sil­ phium speciosum x S^. rever- cHoni.

Figure 3 2 .— Five pairs of Figure 33»— Interpretation chromosomes and a chain of of Figure 32. four during diakinesis in Sil­ phium asperrimum x S. speclo- sum. “ 32

Figure 3 4.— Five pairs of Figure 35.— Interpretation chromosomes and a chain of of Figure 34. four during diakinesis in Sil- phium speclosum x a. asperri- mum.

Figure 3 6.— Seven pairs of Figure _ 37. — Interpretation chromosomes during diakinesis of Figure 3o. in Sllphium trifoliatum x speclosum. 33

Figure 3 8 .— Five pairs of Figure 39*— Interpretation chromosomes and a chain of of Figure 3 8 , four during diakinesis in Sil­ phium trifoliatum x 8. asper- rimum.

Figure 40.— Five pairs of Figure 41.— Interpretation chromosomes and a chain of of Figure 40. four during diakinesis in Sil- phium trifoliatum x S. asper- rimum. ■ 34

A 9

Figure 42*— Five pairs of Figure 43.— interpretation chromosomes and a chain of of Figure 42. four during diakinesis in Sil­ phium asperrimum x ^ trifo- liatum.

»

Figure 4 4— , Seven pairs of Figure 4 5 .— interpretation chromosomes during diakinesis of Figure 4 4 . in Silphium asperrimum x S. reverchoni. "" 35

|-:S

Figure 46.— Seven pairs of Figure 47.— Seven pairs of chromosomes during diakinesis chromosomes during diakinesis in Silphium speclosum x S. per- in Silphium simpsonii var. ToTIâïûmT wrightii~x S T ~speclosum.

# # >%

Figure 48.— Five pairs of Figure 49.— Interpretation chromosomes and a chain of four of Figure 48. during diakinesis in Silphium speciosum x S. simpsonii 3ar. wrightii. 36 Intraspecific crosses involving Silphium integrifolium There are at least four different taxa comprising integrifolium— the glabrous (var. gattingeri), the glandular (var. deamii), the hirsute-pubescent (var. integrifolium) and the pilose-pubescent (var. shelbii). For a better understanding of S. integrifolium, it is of utmost importance to know the cytogenetic relationships between these taxa; consequently representatives of the four taxa should be crossed with one another. Thus far, only two different intraspecific crosses have been made (Table 4). One of these crosses is between S. integrifolium of Coles Co., Illinois (148), which has hirsute phyllaries, and S. integrifolium of Shelby Co., Tennessee (219), which has pilose phyllaries; the other cross is between S. integrifolium of Coles Co., Illinois (148) and S. integrifolium of White Co., Arkansas (276), which also has pilose phyllaries. These crosses were made one year later than the interspecific crosses and the hybrids have not yet flowered; consequently, their meitoic behavior has not been investigated. Only recently have the glandular and the glabrous taxa of S. integrifolium been planted in the research garden, so intraspecific crosses involving these plants are yet to be made. 37 Backcrosses involving the Pi interspecific hybrids of Silphium

The importance of fertile hybrids in the understanding of taxonomic relationships among species depends on the degree of fertility or sterility which is found when they are crossed back to their original parents (Stebblns, 1950).

Backcrosses were made in which as many of the hybrids as possible were used (Table 4). These backcrosses were made during the same season as the intraspecific crosses and the backcross progeny have not yet flowered.

Since the progeny from the backcrosses have not flowered, descriptions of the meiotic behavior in them can only be speculative, If alternate disjunction occurs in the chain of four in the P^ hybrid, then seven pairs of chromosomes or five pairs and a chain of four will result in any given backcross individual. However, if there is non-disjunction in any given arm of the chain, five pairs of chromosomes and a trivalent or seven pairs of chromosomes and one univalent are the expected results. Adjacent dis­ junction will result in gamete abortion.

The meiotic configuration in backcrosses to the reci­ procal P^'s from S. integrifolium and S. speciosum, to the reciprocal P^'s from S. reverchoni, and to the one P^ from

S. speciosum x S. simpsonii var. wrightii should be seven pairs of chromosomes. All the other backcross progeny 38 should be variable as was Just mentioned, because those interspecific hybrids had five pairs of chromosomes and a chain of four.

Ft sibling crosses or Silphium

As a result of most available flowers having been used for backcrosses, only eight sibling crosses could be attempted (Table 4). Sibling crosses were employed because plants of Silphium are self-sterile. Like the plants resulting from the backcrosses and the intraspecific crosses, the P^ sibling crosses have not yet flowered. VARIATION STUDIES IN SILPHIUM INTEGRIFOLIUM, 8. SPECIOSUM, A # S. ASPËRRDtoM

Blosystematlsts (Huxley, 1938 and Gregor, 1939) have reported that there are great disadvantages In the narrow­ ness of the species concept as defined by the alpha taxonomists. In order to broaden the concept of the species, populations should be recognized by means of Gregor*s

"variational type" as well as by a taxonomic type. For greater understanding of S. integrifolium, a study of morphological variation within the "integrifolium" complex—

S. integrifolium, S. speciosum,and S. asperrimum— was under­ taken. Morphological characters which are regarded as being influenced more by genotype than by environment were measured eind the data were treated statistically.

The approximately 650 herbarium specimens used in this study were borrowed from herbaria in the United States (New

York Botanical Garden, Chicago Museum of Natural History,

Missouri Botanical Garden, University of Arkansas, University of Tennessee, University of Kansas, and Southern Methodist

University).1 After the ranges of the distribution of

S. integrifolium, 8. speciosum, and S. asperrimum were documented, a map of the area was divided into quadrats

llhe writer wishes to express her gratitude to the curators of these herbaria. 39 40 approximately 100 miles square. The herbarium specimens were measured for diameter of head, vesture ofjhyllaries, achene length and width, achene notch length and width, and width of achene wing. Ratios of achene length/width and achene notch length/width were then calculated. These data were sorted and assembled according to quadrat regardless of species; all three species were treated as one sample.

Each head that was measured was flowering at the time of preservation, i.e., the ray flowers were completely expanded, but were not faded. The measurement was made Just below the widest expansion of the phyllaries. Small (1933) used this measurement as one of the distinguishing features of S. integrifolium.

Silphium integrifolium has been subdivided into vari­ eties on the basis of phyllary vesture by Perry (1937) and by Cronquist (1945). Silphium speciosum is glabrous and £. asperrimum is coarsely hairy-pubescent. Phyllary vesture was scored in this study on a scale of 0 to 4; 0 represents the glabrous condition; 1, 2, and 3 represent increasing degrees of hairy-pubescence, and 4 represents glandular pubescence. During the scoring of this character, pilose- pubescence was not given a separate number in this scoring method, consequently this quality was included in the one category of hairy-pubescence. Density of pubescence was not scored in this study. When the phyllary is glandular- 41 pubescent, there are some of the other type of hairs inter­ mixed; however, there is no satisfactory method for scoring the proportion of hairs to glands.

Many investigators (Small, 1933; Perry, 1937; Deam,

1940; and Pernald, 1951) differentiate the various species of Silphium by means of achene characters. For this reason, various dimensions of the achene were measured. Achene length was measured from the base of the notch to the base of the achene.

The statistical tools employed in this study were limited to the calculation of means and their standard deviations. Standard deviations were not calculated on any less than five specimens. Means and standard deviations of the measurements of herbarium specimens in individual quadrats are listed in Table 6.

Methods for the analysis of regional variation in

Silphium were adapted from those used by Woodson (1947) in his study of Ascelpias tuberosa. An analysis of the vari­ ation of standard deviations in the study area for every character revealed that the lowest standard deviation for many of the characters occurs in the Ozark Plateau (Quadrats

E-5 and E-6 in Figures 50 and 51). Since cllnal variation both in the northeast and southwest directions from the

Ozarks seemed plausible, a series of equidistant concentric circles emanating from the Ozarks were projected on a map TABLE 6.— Means and standard deviations of the measurements of her) r/ixm specimens from Individual quadrats

Quadrat Number of Head Size Phyllary Achene Achene Achene Achene Achene Number Specimens Vesture wing . 1/w length notch notch 1/w depth Y S Y S Y S Y S Y S Y S X s A-1 15 13.4 3.3 3 1.05 1.05 .2 1.09 .02 6.5 1.27 .37 .39 1.94 .771 A-2 33 18.6 2.9 3.8 .3 1.09 .16 1.09 .12 3.1 3.1 .35 .272 2.19 .6 A-3 7 13.3 2.3 4 0 1.08 .14 1.05 .03 3.9 3.3 .89 .24 2.20 .53 A-4 1 13.7 — ^ — 4 -- - 1.3 -- 1.07 ——— 7.6 ——— .43 ——— 1.6 ——— A-5 2 21.9 — — - . 9 ——— 1.19 --- 8.6 -- . 87 -- 2.3 B-1 43 16.9 2.6 2.6 1.06 1.15 .3 1.19 .19 7.9 2.6 .91 .36 2.2 .67 B-2 23 17.6 2.8 3.4 .8 .94 .28 1.13 .17 7.3 .8 .87 .26 2.5 B-3 13 17.5 3.19 3.07 •7 , 1.16 .4 1.02 .04 7.13 1.35 1.12 .54 2.0 B-H 20 18.3 4.09 3.3 1.06 1.12 .3 1.03 .06 7.73 .87 .9 .29 2.31 .46 B-5 6 15.3 1.46 4 0 .93 .34 1.19 .23 6.8 .33 .7 .117 1.34 .57 B-6 2 25.3 — — — 0 1.7 .95 6.8 .9 — — — 2.6 1 32.2 tl 3 25.1 1 1.1 1 « 62 — - — 11.2 .73 — 2.4

C-0 3 19.3 0.67 •9^ 1.29 7.2 1.97 C-1 13 17.4 2.7 1.69 1.4 1.06 .17 1.41 .73 9.09 4.2 .23 2.2Ô .86 C-2 29 17.9 2.7 1.9 1.06 1.01 .25 1.11 .34 3.1 2.3 .43 2.33 .39 C-3 3 19.2 3.3 2.9 .7 1.2 .13 1.16 3.5 is? 2.4 C-4 13 16.9 2.4 1.9 .27 1.03 .37 1.09 .25 7.4 1.46 1.01 .53 2.4 .76 c-5 14 20.9 5.04 3.21 1.46 1.16 .37 1.29 .55 7.5 1.25 .22 1.69 C-6 16 25.7 5.1 .87 1. 59 .24 1.18 ,004 3.96 1.3 .3 2.4 :ll 5 29.4 4.5 0 0 l:i 11.1 — .3 2.7 tl 4 30.5 0 1.6 7.5 -- .97 4.2 D-1 14.3 .44 .73 1.06 .272 1.23 .241 7.4 1.3 .63 .23 1.45 .43 D-2 13 17.3 2.46 1.05 1.06 .233 1.11 .23 7.03 1.15 .32 2.13 .346 D-3 21 17.1 il1.71 .95 1.15 .302 1.22 .19 3.23 .39 ■ M ,116 2.13 .702 D-4 12 17.5 3.2 2.67 1.15 1.00 .139 1.17 .19 7.49 1.06 .293 1.96 .493 D-5 5 15.4 ——— 2.4 — 1.00 1.13 7.2 'M 1.65 d-6 18 24.3 5.1 1.1 1.5 1.12 .35 1.03 .009 3.0 1.31 .72 .24 1.97 .56 D-7 3 27.2 1.7 1-13 9.6 .52 1.7 D-3 2 20.95 ro TABLE 6.— continued

Quadrat Number of Head Size Phyllary Achene Achene Achene Achene Achene Number Specimens Vesture wing 1/w length notch notch - 1/w depth X s X S X S X s X S X s X S

——— E-1 U 18.9 .75 1.1 BMW 1.16 BBB 7.8 BBB .70 — 1.58 E-2 3' 13.7 -- 3.3 -- 1.55 -- 1.16 -- 8.35 BBB 1.36 — 2.65 -- E-3 1 27.0 --- 3 -- 1.4 -- 1.39 -- 10.6 -- .46 -- 1.5 —- E-4 3 18.56 3 — “ — 1.0 --- .90 -- 6.7 -- .72 -- 2.1 -- E-5 13 22.8 6.3 1.23 1.24 1.21 .24 1.00 .12 7.4 .6 .78 .005 2.2 .28 E-6 8 21.5 4.2 1.25 1.26 2.1 -- 1.15 -- 10.07 .94 -- 2.6 -- S-7 2 22.1 -- 0 1.7 —- 1.43 ——— 10.5 BBB .41 -- 1.7 --

F-0 4 27.2 2.0 1.35 1.32 BBB 10.8 .56 -—— 1.97 F-1 1 18.1 ------1 ——— 1.0 ------1.19 BBB 9.1 BBB .47 -- 1.16 ------F-2 6 17.7 2.6 1 1.65 .92 .192 1.39 .24 8.5 1.05 .74 .31 2.1 .82 F-3 13 16.8 2.7 2.62 .96 .9 .28 1.20 .2 7.4 .87 .59 .14 1.6 .23 P-4 29 18.6 3.8 2.36 .78 1.07 .37 1.24 9.1 3.4 .97 .44 2.3 .34 F-5 10 18.7 2.4 3.1 .47 .94 .3 1.23 6.9 1.06 .608.33 1.36 .6 F-6 5 23.9 5.8 1.4 1.54 1.5 ------1.1 ------9.9 ------. 8 7 -- 2.9 ------F-7 5 29.5 3.7 2 .71 2.1 ——— 1.1 BBB 10.3 ------1.08 — 3.6 ------

G-3 6 18.2 1.5 2.5 .83 1.3 .36 1.19 .19 8.2 .24 1.03 .65 2.2 .72 G-4 22 13.5 4.5 3 .3 1.12 .37 1.15 .01 8.5 1.4 .74 .26 1.75 .51 0-5 18 21.6 6.3 2.27 .75 1.34 .41 1.19 .15 9.1 .98 .554.28 1.43 .69 G-6 7 25.1 4.2 1.85 .69 1.9 ------1.23 ------10.0 ------.63 -— 2.16 0-7 10 26.1 5.18 2.2 .41 2.07 .49 1.14 .12 10.23 1.14 .82 .27 2.3 .7 G—3 1 24.8 — —— 0 ------1.6 ------1.51 BBB 10.3 ------. 7 5 -- 1.5 H-1 1 12.7 4 1.00 1.13 6.7 . 5 3 -- 1.4 - H-3 1 19.4 — — — 2 — “ " 1.6 B.B .98 ------8.1 ------. 4 2-- 1.1 - H-5 1 30.3 — — — 3 — — — 1.1 BMW 1.45 — B 9.6 ------.92 — — 2.6 -BB H-7 30 27.03 5.22 1.9 .64 1.9 .28 1.13 .4 10.34 1.47 .85 .38 2.2 .57

1-6 1 23.5 1 2.2 B B B 1.05 BBB 11.0 ______. 7 3 -- 2.3 - 1-7 7 28.7 2.7 1.57 .78 2.3 ------1.01 ------9.6 BBB 1 . 0 8 -- 2.9 - 1-3 1 23.3 ------1 ------1.1 BBB 1.08 BBB 8.6 ------. 5 5 -- 2.0 - J-4 1 26.0 ^ 0 J—6 1 26.4 M M 2 M 2.3 BBB .96 BBB 8.8 -- . 8 2 -- 2.8 - J-7 24.9 5.56 2.1 1.15 2.0 BBB .89 BBB 8.9 -- . 7 7 -- 2.5 - j-8 11 25.3 5.3 2.6 .65 1.4 .06 1.0 .13 3.4 1.09 .77 .14 1.75 .97 6- K-7 1 26.4 —- — 2 2.8 ------.92 BBB 9.2 ------.62 ——— 2.7 - w 44

(Figure 50). This procedure is made to agree as far as possible with the system of 100 mile quadrats; consequently the first circle, labelled 1, is arbitrarily inscribed with a radius of 50 miles within quadrat E-5. Upon increasing the radius of the compass by 100 miles,a second circle is drawn outside of circle 1, and enclosing circular area NB2 and SW2. Succeeding circles are drawn until all the study area is enclosed, A line intersecting all arcs is drawn diagonally northwest to southeast through quadrat E-5

(circle 1) separating the northeast samples from those of the southwest. Circles 1, NE2-SW2, and NE3-SW3 fall entirely within the study area. In the case of those circles which extend beyond the study area, only the arc portion within the study area was used.

In assigning statistics from the quadrats listed in

Table 6 to the concentric samples of Figure 50, the pro­ cedure was adopted of transferring to a given circle or arc, the data of only those quadrats whose exact centers lay within the boundary of the circle or arc. These newly organized data (Table 7) were then plotted graphically for each morphological character in Figures 52, 54, 56, 58,

60 , and 62 ,

If variation in the northeast-southwest direction is clinal, then variation in the northwest-southeast direction should not be. The same method of concentric arcs emanating from the Ozarks was used, except a line intersecting 45

6 5 4 3

Figure 50.— Method used in studying regional variation in Silphium from northeast to southwest by means of equidistant arcs and circles. (Further explanation in text). TABLE 7.— Means and standard deviations from Table 6 rearranged into arcs emanating southwest and northeast of the Ozark Plateau

Head Size Achene Achene Achene Achene Achene wing 1/w length notch 1/w notch depth Arc No. Y 3E %s No. X X % No. Y x %8 No. Y X Ys No. % X 3s No. Y X Ys 1 13 22.8 6.3 13 1.21 .24 13 1.00 .12 13 7.4 .60 13 .78 .005 13 2.20 .28 NE 2 30 20.9 4.1 30 1.06 .20 30 1.12 .10 17 7.7 1.18 30 .84 .27 30 1.96 .51 NE 3 77 19.4 3.7 77 1.12 .31 77 1.19 .24 61 8.0 1.07 77 .80 .26 77 2.05 .70 NE ,4 64 19.4 3.0 53 1.13 .27 51 1.21 .23 53 7.6 .85 51 .82 .34 51 2.02 .68 NE 5 81 17.1 2.6 81 1.05 .27 81 1.12 .17 81 7.8 1.91 81 .88 .34 81 2.10 .79 NE 6 93 17.9 3.1 93 1.09 .22 93 1.12 .11 93 7.5 2.32 93 .87 .34 93 2.11 .68

SW 2 44 20.2 4.0 39 1.00 .33 39 1.23 .40 39 8.0 2.23 39 .79 .38 39 1.82 .27 SW 3 47 27.1 4.9 40 1.23 .39 47 1.51 .30 40 8.8 1.19 40 .65 .27 40 1.59 .60 SW 4 mmmm •m ## 10 2.07 .49 MM mmmm MM 10 10.2 1.14 10 .82 .27 10 2.3 .70 SW 5 30 27.0 5.2 30 1.9 .28 30 1.9 .28 30 10.3 1.47 30 .85 .38 30 2,2 .57 SW 6 7 28.7 2.7 47 all arcs Is drawn diagonally northeast to southwest through circle 1 separating the northwest samples from those of the southeast (Figure 51). Statistics from the quadrats listed In Table 6 were transferred to the concentric samples of Figure 51 (Table 8). These data were then plotted graphically for each morphological character In

Figures 53, 55, 57, 59, 61, and 63.

Head size

Head size In the "integrlfollum" complex varies from one extreme of 12 mm. In diameter to the other extreme of

40 mm. With respect to members of the complex, the In­ florescences of typical S. Integrlfollum vary from 15 mm. to 18 mm., those of S. speclosum vary between 20 mm. and

25 mm., and those of S. asperrlmum are larger yet, charac­ terized with extremes of 30 mm. and 40 mm.

When all three species are considered together as one sample, a character cllne of smaller to larger heads exists from northeast to southwest (Figure 52). The low standard deviation In the Ozarks Is In SW2 rather than In circle 1; however, this Is not the lowest standard deviation. Opposite to expectation, the standard deviation trends to lower values In each direction from circle 1.

Since there Is a gradient In the northeast-southwest direction, there should not be one In the southeast-north- west direction. In Figure 53, there Is no geographical 48

/

Figure 51.— Method used in studying regional variation in Silphium from northwest to southeast by means of equidistant arcs and circles. (Further explanation in text.) TABLE 8.— Means and standard deviations from Table 6 rearranged Into arcs emanating southeast and northwest of the Ozark Plateau

Head Size Achene Achene Achene Achene Achene wing 1/W length notch notch 1/w depth Arc No. Y X No. X X %s No. % X %8 No. % X Xs No. X X Xs No. X X Xs 1 13 22.8 6.3 13 1.21 ,24 13 1.00 .12 13 7.4 .60 13 .78 .005 13 2.2 ;28 NW 2 30 20.9 4.0 30 2.06 .26 30 1.12 .09 30 7.7 1.18 30 .84 .27 30 1.96 .53 NW 3 48 27.0 4.1 43 1.18 .32 43 1.18 .27 27 8.2 1.27 43 .86 .35 43 2.16 .83 NW 4 39 20.6 3.3 34 1.10 .25 26 1.13 .14 34 7.3 1.08 26 .80 .20 26 1.82 .51 NW 5 36 17.5 2.9 36 1.05 .32 36 1.10 .10 36 7.2 1,07 36 .99 .40 36 2.2 1.04 NW 6 52 18.4 3.0 52 1.07 .16 52 1.07 .07 52 7.8 2.72 52 .87 .30 52 2.11 .65

SE 2 44 20.4 4.0 39 1.00 .33 39 1.23 .40 39 8.0 2.23 39 .79 .38 39 1.83 .47 SE 3 81 19.8 4.5 74 1.12 .34 81 1.39 .26 74 8.3 1.08 74 .68 .20 74 1.74 .55 SE 4 25 17.7 2 i6 23 2.56 .36 25 1.26 .29 50 8.5 .89 50 .83 .38 50 2.19 .77 SE 5 68 19.7 3.3 68 1.32 .27 68 1.43 .28 68 8.6 1.69 68 .80 .34 68 2.01 .63 SE 6 68 21.0 2.6 61 1.10 .23 61 1.30 .46 61 8.5 3.4 61 .87 .29 61 2.23 c76

VO 50 I»

3 0 - 28 -■ 7 26 --6 -.5 X* - .4

20 ■ -- 3 IS-- Xs --2

SW6 SW5 SW4 SW3 SW2 NE2 NE3 NE4 NE5 NE 6 L—

Figure 52.— Regional variation from northeast to southwest of head size.

30 HEAD SIZE 28 .. 7 26- 6 _ 24 14

20 -

Xs - 2

SE6 SE5 SE4 SE3 SE2 NWY NW3 NW4~KW? NW6

Figure 53-— Regional variation from northwest to southeast of head size. 51 gradient. Just as in Figure 52, the deviation in circle 1 again is high, and trends to lower values in each direction away from circle 1.

Phyllary vesture

The means and standard deviations of phyllary vesture are recorded in Table 7> even though they were not used in evaluating this character regionally. Figure 1 is much more valuable in considering this character rather than a graph of the means.

The typical integrifolium var. integrifolium (Cron- quist, 1945) which is characterized by hirsute-pubescence has a considerably narrower distribution than was thought at the onset of this study (Figure 1). Since Michaux (I813) based his description of S. integrifolium on this type of plant; presumably this taxon would be the most widespread.

Actually, the glandular-pubescent S. integrifolium var. deamii (Perry, 1937) Is as commonly distributed as the taxon with hirsute phyllaries. Silphium integrifolium var. gattin- geri (Perry, 1937)» delineated by glabrous phyllaries has a very spotty distribution. Plants with pilose-pubescent phyllaries are limited to Tennessee and Arkansas; these will be named 3. integrifolium var. shelbii. As has been mentioned, glandular hairs are always intermixed with hairy- pubescence, and in all regions except Arkansas, these hairs are hirsute. In Arkansas, the pilose-pubescence occurs on 52 the glandular phyllaries as well (Figure 1). Perhaps these plants are hybrids between var. shelbii and var. deamii.

Length/width ratio of achene

Achenes vary in shape, from long and narrow (above 1) through squarrose (near 1) to short and wide (under 1). In

Figure 54, there is a striking character dine of nearly squarrose achenes in circle 1 to elongate achenes in the southwest and no indication of a dine from circle 1 to the northeast. The lowest standard deviation of all is in NE2, the northeastern part of the Ozarks. There are crests of variability both southwest and northeast of the Ozarks, as expected.

In Figure 55, there is a very slight, probably insig­ nificant, . gradient of elongate achenes in the southeast to squarrose achenes in the northwest. Again, the lowest A standard deviation is in the northern part of the Ozarks, but this time to the northwest. There are crests of vari­

ability northwest and southeast of the Ozarks; and oddly,

there seems to be a definite southeast-northwest clinal

decrease in variability.

Achene length

Achene length in 8. integrifolium varies from 6 mm. to

7.5 ram., in S. speciosum, from 8 mm. to 9.5 mm., and in 53

ACHENE LENGTH/WÜTH

-•AO -.35 -.30 Xs Xs -.25 -.20 -.15 -.10

SW5 SW4 SW3 SW2 I NE2 NE3 NE4 NE5 e N6

Figure 54.— Regional variation from northeast to southwest of length/width ratio of achene.

ACH ENE -4 5 LENGTH/WIDTH - 40

- 35 1.5 - 3 0 1.4 Xs X3 1.3 i- 2 0 1,2 1.1 \ I 1.0 .05

SE6 SE5 SE4 SE3 SE2 I NW2 NW3 NW4 NW5 NW6

Figure 55 «— Regional variation from northwest to southeast of length/width ratio of achene. 54 S. asperrlmum, from 8.5 mm. to 11 mm. In Figure 56, there

Is a character cllne from smaller achenes typical of 8.

Integrlfollum In circle 1 to long achenes typical of 8^.

speclosum and S. asperrlmum In the southwest. Again, as In the length/width ratio of the achene, there Is apparently

no cllne from northeast to the Ozarks. The lowest standard

deviation occurs in the mid-part (circle 1) of the Ozark

plateau. There Is one crest of variability southwest of

the Ozarks, and also one leg of a possible crest In NE6.

There Is no observable cllne In Figure 57* The low standard deviation again occurs In circle 1. One crest

of variability occurs In 8E2 and one leg of each of two possible crests occurs In 8E6 and lnîW6. In any case, the

trend of the standard deviation In both Figures 56 and 57 is upward to both northwest and southeast from circle 1.

Length/width ratio of achene notch

Perry (1937) and 8mall (1933) characterize S. Integrl­ follum by Its narrow notch which Is In contrast to S. spec­

losum with a very broad notch. Silphium speclosum and S.

asperrlmum have notch ratios much lower than those of S. In­

tegrlfollum. However, In graphing the values from one part of the range to the other, there is no clinal gradient In

this character from northeast to southwest (Figure 58) 55

105"

ACHENE LENGTH

mm

SW5 SW4 SW3 SW2 ! NE2 NE 3 NE4 NE5 NEC

Figure 56.— Regional variation from northeast to southwest of achene length.

ACHENE LENGTH

SE6 SE5 SE4 SE3 SE2 I NW2 NW3 NW4 NW5 NW6

Figure 57.— Regional variation from northwest to southeast of achene length. 56 or from northwest to southeast (Figure 59)» Apparently this is not as decisive a character as was once believed.

In Figures 58 and 59, there is a very low standard deviation in circle 1. In the northeast-southwest direction, there are obvious increases in variability in both directions away from the Ozarks; however, in the northwest-southeast direction, in neither direction is there any noteworthy trend toward increasing variability away from the Ozarks.

Notch depth

Small (1933) used the depth of the notch as a key

character. In both Figures 60 and 61, the notch depth

is extremely variable. The two lowest standard deviations of the northeast-southwest direction are in circle 1 and

SW2, and the trend is toward greater variability in both directions away from the Ozarks. In the northwest-south­

east direction, the lowest standard deviation is in circle 1,

and the trend is toward greater variability in both direc­ tions away from the Ozarks.

Width of achene wing

It is evident that the achene wing as well as the

ratio of length/width of achene are more reliable char­

acters upon which to base species differences. In Figure

62, there is a definite gradient of the narrow wing of

integrifolium in the Ozarks to the wider wings of S. 57

ACHENE NOTCH LENGTH/WIDTH .90

-- .30

- 25 X) .2 0

.005 SW5 SW4 SW3 SW2

Figure 53.--Regional variation from northeast to southwest of length/width ratio of achene notch.

i.ocj. 351 ACHENE NOTCH 90-Xx LENOTH/WIOTh / l . q / / \ — el A " \ \ / ^ y -.30^» .75 -.2 5 \/ \ \ / $ V -.20 .61 - .1 5 V.O 0 5 SE6 SE5 SE4 SE3 SE2 I NW2 NW3 NW4 NW5 NW6

Figure 59*— Regional variation from northwest to southeast of length/width ratio of achene notch. 53

2 3 ACHENE NOTCH 2 2 X i DEPTH 2 1 2.0 H. i ' 9 8 X, mm. ' ® .6 . 1.7 A 1.6 2

SW5 SW4 SW3 SW2 | NE2 NE3 NE4 NE5 NES

Figure 60.— Regional variation from northeast to southwest of depth of achene notch.

ACH ENE NOTCH DEPTH 1.2 1.0 8 ,6 Xs

4 2

SE6 SES SE4 SE3 SE2 I NW2 NW3 NW4 NWS NW6

Figure 6l.— Regional variation from northwest to southeast of depth of achene notch. 59 speclosum and S. asperrlmum In the southwest, although there was no apparent gradient from the Ozarks to northeast.

The standard deviations of achene wing width In Figure 62 follow those of the other characters with a high crest of variability southwest of the Ozarks and with a lower crest

In the northeast. Ihe low value of the standard deviation Is In the northeast portion of the Ozarks.

There Is no cllne In the northwest-southeast direction (Figure 63). There Is also no gradient In the standard deviations. 60

ACHENE WING WIDTH

7i

SW9 SW4 SW3 SW2 NE2 NE3 NE4 NE 5 NE6

Figure 62.— Regional variation from northeast to southwest of width of achene wing.

2.6 . I ACHENE WING 24- ; WIDTH 22 _ 40

2.0i- - 3 5 . .30 isl Xs / 'x kzs mm 0 / \ .41 ; \ + 15 1.2 À Id. • j .10 SE6 5E5 SE4 SE3 3E2 I NW2 NW3 NW4 NW5 NW6

Figure 63.— Regional variation from northwest to southeast of width of achene wing. MORPHOLOGY OP THE ARTIFICIAL Pi INTERSPECIFIC HYBRIDS OP SILPHIUM INTEGRIFOLIUM

For differentiating the various characters of the arti­ ficial F^ hybrids of S. Integrlfollum, the same methods of scoring as were used In the herbarium studies were used. Sig­ nificant Information about the morphological relationships between the hybrids and their parents Is shown In Table 9»

Most characters of the hybrids were Intermediate between those of the parents with the exception of the notch characters— the ratio of length/width and the depth— and the phyllary vesture. In the hybrids of S. asperrlmum, of S. slmpsonll var. wrlghtll, and of 8^. reverchonl, there Is definite evidence of the dominance of the "integrlfollum" wing width. In six of eight Instances, the length/width ratio of the notch was lower than either parent; and In the hybrids of S. asperrlmum, reciprocals differed, one value being higher than the value of the ovulate parent. As has been pointed out previously, the character of phyllary vesture Is very difficult to analyze statistically. Morphologically

It Is Impossible to determine any dominance In the "asper­ rlmum" or "integrlfollum" phyllary vestures. However, the

"slmpsonll," and "reverchonl," and the "speclosum" phyllary vestures all seem to be dominant to the "integrlfollum" type.

61 62 t a b l e 9.--Morphological analysis of reciprocal inter­ specific hybrids involving Silphium j^tegrifolium and other species. All measurements are in millimeters. ’The number in parenthesis is The Ohio State University research garden number

Head Phyll- Achene No. Size ary Wing 1/w length notch notch Vesture Width 1/w depth X %%%Y% Y integrifolium ... .. 5 15.1 2 1.3 0.88 6.5 1.14 2.5 asperriraum x intègflfôiium 4 20.9 1.6 1.5 0.89 8.0 1.22 2.6 integrifolium X asperrimum 13 19.7 1.75 1.54 1.07 9.47 0.91 2.45 asperrimum ,(% ... 4 26.9 2 2.4 1.13 12.1 0.93 2.8

integrifolium ~(M8) ' 5 15.1 2 1.3 0.88 6.4 1.14 2.5 slmpsonii var. wrlghtii X in­ tegrifolium 18 18.5 0.2 1.33 0.97 7.72 0.87 2.2 integrifolium X simpsonii var. wrightii 12 17.8 0.75 1.43 1.11 7.2 0.99 2.49 simpsonii var. wrlghtti (84) 4 22.3 0 2.1 0.97 8.8 1.01 2.87 integrifolium " ( 1 # ...... 5 15.1 2 1.3 0.88 6.5 1.14 2.5 reverchoni x integrifolium 1 20.8 0 1.2 0.97 8.6 0.51 2.2 integrifolium X reverchonl 1 21.4 0 1.4 0.96 7.4 1.0 2.4 reverchoni (90) 5 24.1 • 0 3.0 0.80 10.1 0.7 2.8 63 TABLE 9»— continued

Head Phyll- Achene No. Size ary Wing l/w length notch notch Vesture Width 1/w depth X X X X X X X integrifolium CÏ4B) ■ -■ 5 15.1 2 1.3 0.88 6.5 1.14 2.5 speciosum x integrifolium 2 21.2 0 1.0 1.25 7.8 0.76 2.0 speciosum -TI61) '- 2 27.8 0 1.6 1.14 10.6 1.19 2.6

integrifolium (737 " - 5 17.6 4 1.1 1.15 7.46 0.74 1.86 integrifolium xspecioBum* 5 26.8 1 1.3 1.03 8.16 0.66 2.36 speciosum (ÎBÏ) 2 27.8 0 1.6 1.14 10.6 1.19 2.6

Cross made by R. W. Cruden and T. R. Fisher. DISCUSSION AND CONCLUSIONS

Within the "integrifolium” complex, there are several distinct chromosomal differences which result in observable cytological phenomena. Silphium integrifolium and S. speciosum apparently have the same homozygous translocation within their respective genomes judging from the fact that they differ from S. asperrimum, S. reverchoni, and S. simp­ sonii var. wrightii by at least single translocation dif­ ferences (Figure 64).. Silphium asperrimum and S. reverchoni either have one translocation in common within their respec­ tive genomes, while S. integrifolium and S. speciosum do not have a translocation within their respective genomes or vice versa. Silphium simpsonii var. wrightii, S. trifoliatum,and

S. perfoliatum have not been tested extensively enough to establish with certainty their cytogenetic relationships.

Silphium simpsonii var. wrightii introduced more cytological variability into the hybrids of which it was a part than any of the other species. There were rings as well as chains of four chromosomes, and reciprocal differences in the hybrids involving S. simpsonii var. wrightii. Perhaps this genome is of hybrid origin and is not yet genetically stable; however, there were no irregularities in the meiotic behavior of this species. As has been mentioned previously, the reciprocal

64 trifoliotum 7 n simpsonii pgrfoltfltym 7H 7 H 711

inteorifclium speciosum 7H 7n

Figure 64.— Cytogenetic relationships between all species of Silphium included in this study. ------o\ U1 6 6 crosses involving S. simpsonii var. wrightii may not have involved the same individuals as parents.

All of the artificial interspecific hybrids in this study were fertile (Table 5) and, as Kruckeberg (1961) pointed out in his study of Silene, such results as these can justifiably be used as evidence for taxonomic relation­ ships. If Clausen's biosystematic scheme (1951) is followed, then S. integrifolium and S. speciosum are subspecies of one species as also could be said of S. asperrimum and S. rever- choni of another species. However, the evidence at present is not conclusive; according to Stebbins (1950), the true test of genetic relationships is in the fertility or sterility of the backcrosses. The backcrosses on the P^ interspecific hybrids had lower percentages of seed-set than did the P^ interspecific hybrids (Tables 2 and 3). The sibling crosses (Table 4) had either lower seed-set percent­ ages than the P^ interspecific hybrids or no seed-set at all except the one sibling cross of the hybrid (S. speciosum x

S. integrifolium), which had a very high seed-set.

The artificial Interspecific hybrids of S. integrifolium were intermediate between the two parents in most characters probably because most morphological differences are influ­ enced by many genes with individually small effects and relatively little dominance; this was postulated by Towner

(1961) in his work with Tagetes patula. The genetic dominance of one character over another such as was noted in 67 the phyllary vesture or wing width may mask the infiltration

of genes from the plants having the more nearly recessive

character into populations having the dominant character, as

was also realized by Baker in 1951. Consequently the "net"

gene flow in natural populations would not be conspicuous.

Natural hybrids of higher plants are not easily identi­

fied when they are neither sterile nor polyploid. In S.

integrifolium, 8. speciosum, and S. asperrimum, polyploidy

is unknown at the present time and the interspecific hybrids

are fertile, hence intergradation from one taxon into

another is subtle and natural hybrids are seldom distin­

guishable, then only with difficulty.

In the artificial backcrosses (Table 3), there was

consistently a higher seed-set if the hybrid was crossed

. back to the parent, i.e., when the hybrid and not the parent

was the pollen source. Evidently there is considerable ovule

abortion in the hybrids. If this is the case, theoretically

the direction of "net" gene flow should be back toward the

plants of the parental species in natural populations. This

phenomenon would add to the variability of species popula­

tions through introgression.

In propounding the dine theory, Huxley (1938) reported

that the taxonomic entity of species conveys a false impres­

sion of uniformity within a group and subsequently tends to

inhibit the study of intra-group regularities of variation.

Stebbins (1950), objected, not so much to the concept of 68 dines, but to the method used in determining them, of placing the emphasis on those phenotypic characters which may or may not be the most important ones in the evolution of the species as a whole. If a phenotypic character is not useful in distin­ guishing between taxa, then it can be used very well to show variation within one taxon. Of the characters utilized in this study, the achene length and shape, the width of the achene wing, and the diameter of the head were useful in illtatrating clinal variation. The characteristics of the achene notch varied abruptly from one limit of distribution to the other, hence these particular characters are not dependable in distinguishing between taxa. The clinal variation discovered in the present study corresponds closely to the topocline of Gregor (1939)» Variation in four direction from the Ozarks, northeast, southwest, northwest, and southeast, was analyzed and illus­ trated; however, dines were evident only in the northeast and southwest directions. For several of the characters, the dines were very gradual, but in others— achene length, achene notch shape, achene notch depth and the wing— there were abrupt changes. In the distribution of the standard deviations in the northeast-southwest arcs and the northwest-southeast arcs, it was observed that the lowest was usually in the Ozark plateau for most of the characters. To the southwest, . 69 southeast, northwest and northeast of this area, there was either a crest or a gradual increase of variability for some characters. Hybridization and intergradation between

S. integrifolium, S. speciosum, and S. asperrimum may account in part for this high variability. However, in the case of head size, there is great variability within some quadrats. Aside from hybridization and intergradation, time of flowering and location of the inflorescence on the plant may contribute to variation in head size. Later flowering heads are somewhat smaller than early flowering heads as are the heads on axillary branches; actually later flowering heads are axillary in origin. It is possible that the explanation for the great variability to the northeast and northwest of the Ozarks might involve the geological history of that area.

The present-day distribution of the "integrifolium" com­ plex has been in existence for only a few, thousand years. Dur­ ing the Cretaceous flooding, Ozark plateau seems to have been the only possible refugium for these taxa. During the subse­ quent glaciation (Geological Society of America, 1959), the present-day S. asperrimum could have been living in the south­ west, while the rest of the complex will still be in the Ozarks.

If this is assumed, then S. asperrimum must be older in its present-day distribution than either S. integrifolium or S. speciosum, a possibility which would account for the period of 70

Isolation during which the chromosomal interchange became established. As the plants moved out of the Ozarks follow­ ing glaciation, increased variation accompanied this migra­ tion. As Baker (1955) explained, only self-compatible species migrate and establish them elves at a fast rate, consequently Silphium, whose taxa are self-sterile, must have moved at a slow rate.

In taxonomy, some characters are considered primitive and some are considered advanced; the morphological feature of a few large inflorescences is considered advanced over the feature of many small inflorescences. Silphium specio­ sum has fewer and larger inflorescences than S. integrifolium as a result of being older in its present-day distribution; as the glaciers receded, plants were able to migrate in the westerly direction from the Ozarks sooner than to the north­ east. Silphium integrifolium is characterized by small inflorescences on many branched peduncles; hence, it is considered primitive when compared with S. speciosum and

S. asperrimum. Plants with primitive morphological features have a more recent occupancy of their present-day range. '

With regard to the standard deviations, the present-day

S^. integrifolium in the Ozarks is less variable than it is elsewhere, üïiis would stand to reason, if the Ozarkian is the oldest population, and if it is assumed that this land mass has been the least disturbed in the south central portion of the United States. Present-day spéciation is 71 going on at a fast rate in all directions from the Ozarks, but predominately toward the northeast. Standard deviations are much higher at the eastern and northern limits of the range, because the species is comparatively young in that area.

The crests or trends toward higher variability to the northeast and southeast could be result of mutation and hybridization; and the survival value of the variants is high in the area which has been disturbed by glaciation.

The climate is conducive to lush vegetative growth, sub­ sequently population expansion will occur at a fast rate. TAXONOMIC CONSIDERATIONS

Stebbins (1950) found that dines which are continuous over long distances do not form a good basis of classifica­ tion. The dines of the "integrifolium” complex are more like continuous ones, with the exception being those of the achene notch dimensions. So these dines are useless as a basis for a taxonomic change in Silphium. Natural hybrids of S. integrifolium and S. speciosum are practically impos- . Bible to identify, because they are fully fertile. The only factual evidence of a dose relationship between S. integrifolium and S. speciosum is complete pairing between homologous chromosomes and their similar cytogenetic rela­ tionships to S. asperrimum, S. reverchoni and S. simpsonii var. wrightii (Figure 64). Silphium trifoliatum and S. per- foliatum have been tested genetically only with S. speciosum, so their exact relationship to S. integrifolium can only be surmized. Included in this "integrifolium" complex is S. asperrimum which is less closely related to £. integrifolium than is S. speciosum as a result of at least one chromosomal translocation. The four varieties of S. integrifolium will be studied as to their genetic relationships to each other, to S.

72 73 speciosum, and to S. asperrimum, Silphium integrifolium var. gattingeri has a very limited discontinuous distribution; hence it is doubtful that it is an ecotype of S. integri­ folium. Silphium integrifolium var. deamii is definitely a good epithet. Silphium integrifolium var. integrifolium should be divided into the hirsute taxon and the pilose taxon. Since Michaux described S. integrifolium as being characterized by hirsute hairs, S. integrifolium var. integ­ rifolium should typify this kind of plant. The taxon with pilose hairs which occurs in Tennessee and Arkansas should be S. integrifolium var. shelbii, because pilosity is genetic. As Oamp and Gilly pointed out in 1943,

it is needful for the systematist to accept as principles that species do not possess the same amount of genetic variability and that all indi­ viduals of a species, therefore, may not exactly match a particular specimen, which, because of an accident of exploration, is to be considered the nomenclatural type.

If through backcrossing and other interspecific crosses,

S. integrifolium and S. speciosum are found to harbor the same two genomes, a new taxon should be established. This new taxon would be what Stebbins (1950) referred to as a polytypic species or Rassenkreis. Camp and Gilly referred to this type of species as a rheogameon which they define as having been made of "segments of reasonably marked morphological divergence whose distributions are such that gene interchange may take place in sequence between them."

The use of the quality of "fertility between populations" of 74

Silphium In delimiting taxa Is dangerous, because real genetic barriers to crossing between most species of

Silphium (Fisher et 1963) are absent. However, with the substantiation of cytologlcal observations, such evidence of genetic relationship Is conclusive.

It is suggested that If all genetic tests Indicate with reasonable assurance that close genetic relationships exist, then the following nomenclatural pattern should be accepted (Figure 65).

Silphium Integrifolium ssp. Integrifolium comb, nov.

var. Integrifolium

var. deamll

var. gattingeri

var. shelbll Lengel var. nov.

S. Integrifolium ssp. speciosum comb, nov. 75

Silphium Lnteo ri folium

ssp, speciosum

's

V 0 r.

Silphium asperrimum

Figure 65,.— Cytotaxonomic relationships of the "integrifolium" complex. Broad dark bands, good pairing of homologues observed; dash bands, good pairing of homo­ logues expected; narrow line, one translocation difference observed; narrow dash line, one translocation difference expected. SUMMARY

The three taxa studied In this paper have been Investi­ gated in the research garden, in the herbarium, and

cytologically.

Silphium integrifolium, S. speciosum, and S. asperrigtm have distinct ranges which overlap at the western edge of

the range of S. integrifolium in Kansas, Oklahoma, Arkansas,

and Texas. Silphium integrifolium is composed of four taxa

which are distinguishable by different phyllary vestures which were shown to be but little influenced by environmental

variation.

Reciprocal interspecific hybrids were made between

S. integrifolium and S, speciosum, S. asperrimum, S. rever­

choni, S. simpsonii var. wrightii, and S. trifoliatum.

Reciprocal backcrosses were made using as many of the

"integrifolium" hybrids as possible and also other arti­

ficial hybrids which had been made previous to the present study involving S. speciosum, S. asperrimum, S. reverchoni,

S. simpsonii var. wrightii, and S. perfoliaturn. Reciprocal

intraspecific crosses were made between two of the four

taxa of S_. integrifolium.

76 77 Cytologlcal investigations of S. integrifolium, S. spec­ iosum, S. asperrimum. S. reverchoni,and S. simpsonii var. wrightii verified the already documented n = 7 chromosomes.

Cytologlcal investigations of the artificial inter­ specific hybrids revealed that S. integrifolium and S. speciosum have at least one translocation in common, as do also S. asperrimum and S. reverchoni. as well as S. speciosum and S. perfoliatum, and S. speciosum and S, trifoliatum.

Silphium integrifolium and S. speciosum when crossed with

S. asperrimum, S. reverchoni or S. simpsonii var. wrightii produce hybrids which have meiotic behavior at diakinesis of five pairs of chromosomes and a chain of four. In all instances, the chain of four had the same unique configur­ ation which included a loop.

Herbarium studies revealed that there are character

Clines northeast-southwest extending through the ranges of

S. integrifolium, S. speciosum, and S. asperrimum based on means and standard deviations of measurements of herbarium specimens. Variation of these herbarium specimens in the northwest-southeast direction is not clinal.

The probable origin of the "integrifolium" complex is in the Ozark Plateau based on standard deviation distribu­ tion in the variation studies and geological history of that area. 78

A new variety was named, Silphium Integrifolium var. shelbll Lengel var. nov. If forthcoming cytotaxonomic studies confirm the close genetic relationships of S.

Integrifolium and S. speciosum, a proposed new taxonomic pattern for these taxa will be Justified. LITERATURE CITED

Baker, H. C. 1951 Hybridization and natural gene flow between higher plants. Cambridge Philosophical Society. Biological Reviews. 26:302-337.

Baker, H. C. 1955 Self compatibility and establishment after "long-distance" dispersal. Evolution 9:347-349' Beeks, R. M. 1955 Improvements In the squash technique for plant chromosomes. Allso 3:131-133.

Benke, H. C. 1932 Some field notes; a new variety and some forms of plants from the middle west; also two forms from Massachusetts. Rhodora 34:10.

Camp, W. H. and C. L. Gilly. 1943 The structure and origin of species. Brlttonla 4:323-385»

Clausen, J. 1951 Stages In the Evolution of Plant Species. Hafner Publishing Co., New Ÿork. p. 155»

Cronqulst, A. 1945 Notes on the Composltae of northeastern United States. I. Inulae. Rhodora 47:182-184.

Cronqulst, A. 1945 Notes on the Composltae of northeastern United States. II. Hellantheae and Helenlae. Rhodora 47:401.

Cruden, R. W. i960 Biosystematic studies In the genus Sil­ phium (Composltae); the perfoliate taxa. Unpublished Aster's thesis. The Ohio State University.

Deam, C. C. 1940 Flora of Indiana. Dept, of Conservation, Dlv. of Forestry, incHCanapolls.

Fernald, M. L. 1950 Gray's Manual of Botany. American Book Co., New York.

Fisher, T. R. and R. W. Cruden. I962 Chromosome numbers and observations In the genus Silphium. Ohio Jour. Scl. 62:258-259. Fisher, T. R. et al. 1963 Unpublished manuscript. The ■ Ohio State lETverslty. 79 8 o

Geological Society of Araerica. 1959 Glacial Map of the United States east of the Rocky Moimtains. 419 W. 117 St., liew York. Edition 1.

Gregor, J. W. 1939 Exfisriniental taxonomy IV. Population differentiation in North American and European sea plantains allied to Plantago maritima L. New Phytologist 38:293-3^^.

Hooker, J. D. 1835 Mr. Drummond's collections. Hooker's Companion to the Botanical Magazine 1:99.

Huxley, J. 1938 Clines: an auxiliary taxonomic principle. Nature 142:219-220.

Kruckeberg, A. R. 1961 Artificial crosses of western Silenes. Brittonia 13:305-333*

Land, W. J. G. I9OO Double fertilization in Compositae. Bot. Gaz. 30:252-261.

Merrell, W. D. 1900 A contribution to the life history of Silphium. Bot. Gaz. 29:99-133.

Michaux, A. I803 Flora Boreall-Americana. Parisiis et Argentorati, Apud fratres Levrault. 2:l^b.

Nuttall, T. 1841 Descriptions of new species and genera of plants. Trans. American Philosophical Society. 2 new series:34l.

Perry, L. M. 1937 Notes on Silphium. , Rhodora. 39:287. Small, J. K. 1933 Flora of the Southeastern United States. Univ. of North Carolina Press, Chapel HilH

Stebbins, G. L. 1950 Variation and Evolution in Plants. Columbia Univ. Press, lîew York. pp. 2ü7-2ü8.

Stebbins, G. L. 1958 The inviability, weakness and steril­ ity of interspecific hybrids. Advances in Genetics 9:147-215* Torrey, J. and A. Gray. 1843 Flora of North America. Wiley and Putnam, New York. 2:275^ 81 Towner, J. W. 196I Cytogenetic studies on the origin of Tagetes patula. I. Meiosis and morphology of diploid ana alltetraploid T. erecta x T. tenuifolla. Am. Jour. Bot. 48:743-751% “

Woodson, R. E. 1947 Some dynamics of leaf variation in Ascelepias tuberosa. Ann. Missouri Bot. Gard. AUTOBIOGRAPHY

I, Patricia Ann Lengel, was born In Elyria, Ohio,

August 6, 1930. I received my secondary-school education In the public schools of North Rldgevllle, Ohio and Parma, Ohio,

The College of Wooster granted me the Bachelor of Arts degree In 1952. In 1954, I received a Master of Science degree from The Ohio State University. During the ensuing six years, I held teaching positions at the following schools: Hanover College at Hanover, Indiana; Muskingum

College, New Concord, Ohio; and the College of Wooster at

Wooster, Ohio. Throughout this Interim, I attended the summer sessions of the following biological field stations:

Stone Laboratory of The Ohio State University at Put-ln-Bay,

Ohio (1954-1955); Rocky Mountain Biological Laboratory at

Crested Butte, Colorado (1956); University of Oregon Marine

Laboratory at Charleston, Oregon (1957); University of

Michigan Biological Station at Pellston, Michigan (1958); and the University of Wyoming Science Camp at Centennial,

Wyoming (1959). The studies at Oregon and at Wyoming were supported by the National Science Foundation, while the sum­ mer at Michigan was supported by the Ell Lilly Foundation.

8 2 83 Since the fall of i960, while specializing in the

Department of Botany and Plant Pathology at The Ohio State

University, I have completed the requirements for the

Doctor of Philosophy degree.