Bull. mil. Hist. Mus. Loud. (Zool.) 68(2): 83-90 



Issued 28 November 2002 



Morphological variation and the definition of 

 species in the snake genus Tropidophis 

 (Serpentes, Tropidophiidae) 



S. BLAIR HEDGES 



Department of Biology, 208 Mueller Laboratory, The Pennsylvania State University, University Park. 

 Pennsylvania 16802, USA. e-mail sbhl@psu.edu 



SYNOPSIS. Historically, the definition of species in the Neotropical snake genus Tropidophis has been difficult because of 

 intraspecific variation in scalation and a paucity of specimens of most taxa. There were 13 species recognized at the time of the 

 last review in 1960. but additional species have since been discovered and a taxonomic review and update is needed. Data on 

 morphological variation are presented here and used to clarify the status of the described taxa. Because many taxa are allopatric 

 with their closest relatives, it is necessary to make decisions as to their status as species or subspecies. As a gauge of species status 

 in the genus, character divergence in ten pairs of closely related sympatric species was examined. Typically, such species are 

 differentiated by two non-overlapping colour pattern differences, often in combination with a diagnostic (non-overlapping) or 

 overlapping difference in scalation. Using this criterion, seven taxa previously considered as subspecies are here elevated to 

 species status, whereas seven other taxa are retained as subspecies, although in some cases they are allocated to different species. 

 As a result, the genus Tropidophis is considered here to comprise 29 species, 26 of which are West Indian and 15 of those are 

 restricted to Cuba. 



INTRODUCTION 



Tropidophis are typically small, stout-bodied snakes of the family 

 Tropidophiidae that occur in South America and the West Indies. 

 This family is a member of the primitive snake Infraorder Henophidia 

 (Underwood, 1967). As recognized here, there are 29 valid species 

 oi'Tropidophis and all but three occur in the West Indies, where Cuba 

 (15 species) is the centre of diversity (Table 1). They are nocturnal 

 and feed mostly on sleeping lizards (especially Anolis), but also on 

 frogs (especially Eleutherodactylus); other nocturnal snakes may 

 impinge on Tropidophis ecologically. All are viviparous and most 

 are terrestrial, although several Cuban species are arboreal and 

 gracile in habitus. They exhibit a diversity of colour patterns that 

 include spots (mostly), bands (saddles), and stripes. They have the 

 unusual ability of being able to change their colouration, physiologi- 

 cally (Hedges. Hass & Maugel, 1 989). Typically they are paler when 

 active (at night) and dark while inactive. Species distributions tend 

 to be greatly restricted, with species endemic to single islands or 

 island banks, and often to small areas on an island. However, species 

 density can be high, and as many as six species are sympatric in 

 some areas of Cuba. 



Historically, the taxonomy of Tropidophis has been difficult to 

 study because of small numbers of specimens and a paucity of 

 diagnostic characters. For example, two of the earliest described 

 species, T maculatus and T pardalis, have been confused repeat- 

 edly. Boulenger ( 1 893) and Stull ( 1 928) commented on the confusion 

 of these species by Cope (1868), whereas Schwartz and Marsh 

 ( 1 960) later commented on their confusion by Stull ! Most of these 

 early problems in Tropidophis taxonomy stemmed from the use of 

 characters later found to be unreliable, such as the keeling of scales 

 or hemipene morphology. It was not until Schwartz and Marsh 

 ( 1 960) assembled a large number of specimens and collected exten- 

 sive data on proportions, scalation and pattern that the systematics of 

 this genus became reasonably well known. Although it was a large 

 study, it was not comprehensive because it omitted species related to 



T melanurus and those placed by Schwartz (1957) in the semicinctis 

 group. However, their success was in recognizing the utility of 

 colouration and pattern characters, and that species diagnosis in this 

 genus often requires consideration of multiple characters, some of 

 which may not be individually diagnostic. 



This is not a comprehensive revision of the genus but rather a 

 taxonomic update, motivated by the many changes that have occurred 

 since that last major review (Schwartz & Marsh, 1960) and the need 

 to summarize what is known of morphological variation in the 

 genus. Another motivation is to address a recurring problem in the 

 systematics of this group: determining the species status of allopatric 

 populations and taxa. In the process, taxa previously considered as 

 subspecies are here elevated to species status, some are assigned to 

 different species, and others are left unchanged. 



MATERIALS AND METHODS 



The data presented herein are almost entirely from the literature, or 

 were used in published studies (but not necessarily published in the 

 form here). Most derive from the raw data sheets of the late Albert 

 Schwartz, used primarily in several publications (Schwartz, 1975; 

 Schwartz & Garrido, 1975; Schwartz & Henderson, 1991; Schwartz 

 & Marsh, 1960; Schwartz & Thomas, 1960; Thomas, 1963). 

 Schwartz's Cuban specimens are in the American Museum of 

 Natural History and his other material is almost entirely in the 

 collection of the Museum of Natural History, University of Kansas. 

 In addition to those data, I have included data from specimens I and 

 colleagues have collected during the last two decades of field work, 

 and which, for the most part, formed the basis of several published 

 studies: (Hedges, Estrada & Diaz, 1999; Hedges & Garrido, 1992; 

 Hedges & Garrido, 1999; Hedges & Garrido, 2002; Hedges, Garrido 

 & Diaz, 2001). This material is in the National Museum of Natural 

 History (Smithsonian) and in Cuban collections (National Museum 

 of Natural History, Havana; Institute of Ecology and Systematics, 



© The Natural History Museum. 2002 



