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University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Mammalogy Papers: University of Nebraska State Museum Museum, University of Nebraska State January 1979 Rabbits (Genus Sylvilagus) of Nicaragua Terry L. Yates Texas Tech University, Lubbock, Texas Hugh H. Genoways University of Nebraska-Lincoln, [email protected] J. Knox Jones Jr. Texas Tech University, Lubbock, Texas Follow this and additional works at: https://digitalcommons.unl.edu/museummammalogy Part of the Zoology Commons Yates, Terry L.; Genoways, Hugh H.; and Knox Jones, J. Jr., "Rabbits (Genus Sylvilagus) of Nicaragua" (1979). Mammalogy Papers: University of Nebraska State Museum. 77. https://digitalcommons.unl.edu/museummammalogy/77 This Article is brought to you for free and open access by the Museum, University of Nebraska State at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Mammalogy Papers: University of Nebraska State Museum by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Rabbits (Genus Sylvilagus) of Nicaragua Terry L. YATES, Hugh H. GENOWAYS, and J. Knox JONES, Jr. Ce travail constitue une revision systbmatique des lapins (Syluilagus) du Nicaragua. On a pu apprkcier I'importance de la variation geographique d'aprks l'examen de 124 speci- mens de hluske constituant 28 Bchantillons de S. floridanus du Honduras, du Nicaragua et de Costa-Rica, et 15 Bchantillons de S. brasiliensis du Nicaragua et de Costa-Rica. Les particularitbs morphologiques de la peau et du crlne ont kt6 soumises a des analyses statistiques. La variabilite geographique de S. floridanus permet de mettre en Bvidence que les representants de I'espitce au Nicaragua sont plutBt rkferables a la forme S. f. costa- ricensis qu'a S. f. hondurensis comme on le croyait jusqu'alors. D'aprits ce que l'on sait de la variabilite gbographique de S. brasiliensis, il ne parait pas exister d'autre sous-espkce au Nicaragua que S. b. gabbi. The genus Sylvilagus is represented in Nicaragua by two species, Sylvilagus brasiliensis and Sylvilagus floridanus. Nelson (1909) revised the genus and subsequent authors (Goldman, 1932 ; Harris, 1933 ; Hershkovitz, 1950) have treated certain Latin American populations taxonomically. Nevertheless, little has been published on Nicaraguan material because few specimens here- tofore have been available for study from that country. Acquisition in recent years of a comparatively large series of rabbits from Nicaragua, together with extant specimens from Honduras and Costa Rica, has made possible a rrieaning- ful review of the genus Sylvilagus in this important Middle American region. Our study was based on examination of 124 museum specimens, constitu- ting 28 samples of Sylvilagus floridanus from Honduras, Nicaragua, and Costa Rica, and 15 samples of S. brasiliensis from Nicaragua and Costa Rica. The following 12 external and cranial measurements were recorded for each speci- men used in analyses : total length ; length of tail ; length of hind foot ; length of ear (from notch) ; greatest length of skull ; zygomatic breadth ; interorbital breadth ; breadth of braincase ; length of palatal bridge ; length of maxillary toothrow ; breadth of mesopterygoid fossa (least transverse diameter of the mesopterygoid fossa, measured on the ventral rim of the fossa on the outside of palatine bones posterior to the molar toothrow) ; length of nasals. All cranial measurements were taken to the nearest 0.1 millimeter with the aid of dial calipers. External measurements were taken directly from museum specimen labels as were measurements of testes and embryo lengths, and all are recorded in millimeters. Individual, age, and secondary sexual variation were analysed with the aid of the univariate statistical system (UNIVAR) described by Power (1970). All specimens were assigned to one of three age classes. Means were calculated for each character and a single classification analysis of variance was used to 114 MAMMALIA test for differences between age classes and sexes. Coefficients of variation (CV) were calculated to determine the extent of variability for each character. Geographic variation was analyzed using both univariate (mean, standard deviation, and standard error) and multivariate statistics. To assess the degree of divergence among samples, a multivariate analysis of variance (MANOVA) and canonical analysis program from the statistical analysis system (SAS) designed and implemented by Barr and Goodnight (Service, 1972) were used. Canonical analysis of data aimed at providing weighted combinations of measu- rements that maximize the distinction between groups. This program extracts characteristic roots and vectors and computes mean canonical variates for each sample. The relative importance of each original variable to a particular TABLE 1. - Results of analyses of variances among age classes of Sylvilagus brasiliensis from Rio Mico, El Rec~eo,Zelaya, Nicaragua. Age - Measurement class N F X SD SE CV Range Total length 16 305.8 15.0 6.1 4.9 285.0-325.0 24.0 2 4 350.0 12.1 6.0 3.5 340.0-367.0 0.1 3 6 346.0 30.7 12.5 8.9 309.0-385.0 Length of tail 16 21.0 6.4 2.6 30.7 12.0- 28.0 0.5 2 4 18.5 2.6 1.3 14.8 15.0- 21.0 0.1 3 6 19.5 4.9 2.0 25.3 15.0- 27.0 Lengthof hidfoot 1 6 69.5 4.4 1.8 6.3 63.0- 75.0 5.1 2 4 76.2 4.9 2.5 6.5 69.0- 80.0 0.1 3 6 75.7 1.9 0.8 2.5 73.0- 78.0 Length of ear 16 43.5 2.8 1.1 6.5 38.0- 45.0 10.8 2 4 48.2 0.5 0.3 1.0 48.0- 49.0 3.1 3 6 46.3 2.1 0.8 45 43.0- 49.0 Greatest length of 1 6 59.6 3.5 2.0 5.9 55.6- 62.3 skull 14.6 2 4 66.7 1.3 0.6 1.9 65.4- 68.0 0.1 3 6 67.6 4.6 1.9 6.8 62.2- 74.0 Zygomatic breadth 1 6 29.6 1.0 0.4 3.4 28.2- 30.8 15.5 2 4 31.8 0.6 0.3 1.9 31.3- 32.5 0.0 3 6 31.8 1.3 0.5 4.1 30.2- 33.2 Interorbital breadth 1 6 12.9 0.7 0.3 3.6 11.9- 14.0 8.3 2 4 14.0 0.4 0.2 2.5 13.7- 14.4 0.3 3 6 14.5 1.4 0.6 9.9 12.8- 16.1 Breadth of braincase 1 6 22.0 0.7 0.3 3.1 21.1- 22.8 4.0 2 4 22.8 0.5 0.2 2.1 22.3- 23.3 0.2 3 6 22.6 0.7 0.3 3.3 21.9- 23.8 Length of palatal 1 6 6.6 0.3 0.1 4.9 6.1- 6.9 bridge 4.2 2 4 -. 7.0 0.3 0.2 4.6 6.8- 7.5 2.1 3 6 6.7 0.4 0.2 5.5 6.4- 7.3 Length of maxillary 1 6 11.8 0.5 0.2 4.1 11.1- 12.4 toothrow 15.2 2 4 .. 12.8 0.2 0.1 1.6 12.5- 12.9 0.0 3 6 12.8 1.1 0.5 8.9 11.4- 13.9 Breadthof meso- 1 6 8.3 0.6 0.2 6.9 7.7- 9.3 pterygoid fossa 4.9 2 4 9.0 0.4 0.2 4.1 8.6- 9.5 0.0 3 6 9.0 0.5 0.2 5.8 8.4- 9.6 Length of nasal 16 25.1 1.6 0.7 6.5 22.3- 26.3 10.5 2 4 28.0 0.8 0.4 2.7 26.9- 28.6 0.2 3 6 28.6 2.5 1.0 8.9 25.8- 32.6 RABBITS OF NICARAGUA 115 canonical variate was computed by multiplying the vector variable coefficient by the median value of the dependent variable, summing all variable values for a particular vector, and then computing the percent of relative importance of each variable per vector. Field work in Nicaragua was supported by a contract (DA-49-193-MD-2215) from the U. S. Army Research and Development Command. Some of the laboratory work was supported by a grant (GB-28957) from the National Science Foundation. We are grateful to officials of the following institutions for loan of speci- mens : American Museum of Natural History (AMNH) ; Museum of Natural History, University of Kansas (KU) ; Museum of Zoology University of Michigan (UMMZ) ; National Museum of Natural History (USNM). S YL VILAGUS BRASILIENSIS Three types of nongeographic variation - variation with age, secondary sexual variation, and individual variation - have been treated. An under- standing of these kinds of variation is necessary in order to properly interpret geographic variation in both species of Nicaraguan Sylvilagus. Variation with age. - All specimens were originally assigned to one of three age classes, which were defined as follows : class I, suture between basisphenoid and basioccipital bones not closed; class 11, suture between basisphenoid and basioccipital bones closed but clearly visible to the naked eye as a thin line ; class 111, suture between basisphenoid and basioccipital bones completely ossified and not visible to the naked eye. Analysis of variance was used to test each of 12 external and cranial measurements for significant differences between age classes in a sample from the south side of the Rio Mico, El Recreo, Zelaya, Nicaragua (Table I).