The Genera Rhoptropus and Phelsuma (Reptilia: Gekkonidae) in Southern Africa: a Case of Convergence and a Reconsideration of the Biogeography of Phelsuma
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THE GENERA RHOPTROPUS AND PHELSUMA (REPTILIA: GEKKONIDAE) IN SOUTHERN AFRICA: A CASE OF CONVERGENCE AND A RECONSIDERATION OF THE BIOGEOGRAPHY OF PHELSUMA. ANTHONY P RUSSELL Department of Biology. The University of Calgary. Calgary. Alberta. Canada T2N J N4 Accepted: March 1977 ABSTRACT The genus Rnoptropella Hewitt, 1937 is shown to be a junior synonym of Phelsuma Gray, 1825 and the genera Pheuuma and Rhoptropus Peters, 1869 are compared. It is pointed out that Phelsuma ocellata shows a great deal of convergence with Rnoptropus but that both of these forms exhibit their own distinctive derived character combinations. The distribution pattern of Phelsuma on the main land of Africa and on Madagascar is reviewed in the light of current theories of biogeography and past continental relationships. It is suggested that the distribution of Pheuuma may represent a track which is also occupied by other reptilian genera. ) 0 1 0 2 DEDICATION d e t a d ( I would like to dedicate this paper to the memory of Karl Patterson Schmidt who first r e h erected the combination Phelsuma ocellata and in so doing pointed out the true relation s i l ships this southern African species. His conclusions were denied acceptance due to the b of u P lack of supporting biogeographic evidence and the absence of an acc:eptable system for the e h construction of phylogenies. t y b d e t n INTRODUCTION a r g e c It has recently been pointed out (Russell 1976) that although a great deal of work has been n e c i carried out over a number of years on various aspects of the biology of geckos, little is l r e known of the interrelationships between many of the genera. It is the object of this paper to d n point out how such interrelationships may be investigated and how true interrelationships u y have been obscured in the past by a reliance on geographic rather than phylogenetic a w evidence. e t a The geldconid genus Rhoptropella Hewitt, 1937 has, since its inception, been regarded as G t e monotypic and represented by the sole species Rhoptropella ocellata (80ulenger, 1885). n i The relationships of this form, however, have proved to be problematical. Although this b a S y Zoologica A/ricana 12(2): 393-408 (1977) b d e c u d o r p e R 394 ZOOLOGICA AFRICANA VOL 12 matter provoked a good deal of discussion during the first half of this century the problem has not been reappraised since recent advances in phylogenetic systematics, biogeography' and plate tectonics have become widely known. There is now a greater body of information available to enable us to firstly construct phylogenies and then to attempt to assess where these theories leave us with respect to ideas about past earth history. I have chosen here to discuss the genus .. Rhoptropella" as its true interrelationships appear to be of particular interest from the point of view of biogeography and because it shows an extreme degree of convergence with those forms with which it was previously supposed to be related. The structure and relationships of many of the genera of Southern African geckos have recently been reviewed by Haacke (1976), but as this work dealt only with burrowing forms the genus"Rhoptropella" was not included in the main body of the discussion. It appears that "Rhoptropella" has its affinities outside of the area in which it is found and mainly for this reason have its true relationships been obscured. MATERIALS AND METHODS Specimens of the genera Rhoptropus, Rhoptropella and Phelsuma were examined and, in some cases, dissected in order to obtain sufficient data for a correct phylogenetic analysis. Drawings were made using a Wild MS dissecting microscope with camera lucida attach . ) 0 ment. 1 0 The specimens were not examined in isolation but instead with the benefit of a complete 2 d analysis of foot structure in the family Gekkonidae (Russell 1972). It has thus been possible e t a to place the phylogenetic conclusions reached in this study in perspective with respect to the d ( r entire family, and to distinguish significant consistencies in structure from superficial e h similarities due to convergence. In excess of 230 specimens were examined and these are s i l b listed in the appendix to this paper. u P e h t y DISCUSSION b d e t n Past ideas concerning the interrelationships of Rhoptropella Hewitt, 1937 a r When originally described, Rhoptropella acellota was placed within the genus g e c Rhoptropus (Peters 1869), a genus with which most authors have assumed it to be closely n e c related. Hewitt (1937) stated that its affinities lay with Rhoptropus but erected the genus i l r Rhoptropella because of certain consistent differences between the two. Because, however, e d n Hewitt compared Rhoptropella chiefly with other southern African genera he had already u y made a subjective decision that it must be related most closely to southern African forms, a w and Rhoptropus came closest. Thus, by inferring that geographic position must determine e t a relationships the true affinities of Rhoptropella have been obscured for the past 40 years. G t The classic work on African geckos (Loveridge 1947) sealed the fate of obscuring the e n i relationships of Rhoptropella as it reaffirmed the conclusions reached by Hewitt (1937). b a S y b d e c u d o r p e R 1977 PHELSUMA IN SOUTHERN AFRICA 395 Again other possible relationships were denied chiefly on the grounds of distribution and habits. This decision by Loveridge (1947) seems all the more strange when it is considered that he revised the genus Phelsuma only five years earlier (Loveridge 1942). Before the work of Hewitt (1937) or Loveridge (1942, 1947), however, the status of Rhoptrope/la oce/lata had already been questioned. Mter examining this species (at the time known as Rhoptropus ocellatus) and comparing it with Phe/suma, Roux (1907) was forced to ask, "Is Rhoptropus a synonym of Phelsuma r' Only a tentative suggestion of the placement of Rhoptropus into synonymy with Phelsuma was made, however, and it was left to Schmidt (1934) to fQtmaUy change the status of Rhoptropello ocellata. He proposed the new combination of Phelsuma ocellota (BoUlenger, 1885). In so doing he was careful to clearly distinguish oce/lata from all other species of the genus Rhoptropus, and stated that although the abov~mentioned taxonomic change was necessary it did not affect the validity of the latter genus. It appears, therefore, that Schmidt's (1934) contribution was largely overlooked due to the insistence of Hewitt (1937) and Loveridge (1947). The possibility of relationship with Phelsuma was dismissed by Hewitt (1937) because he did not believe that forms separated by such great distances could be congeneric, and because his comparison with members of the genus Phelsuma was based upon an unfortunate examination of the segment of that genus least like Rhoptrope/la in both habits and morphology (see below). It is now evident that Phelsuma is not as uniform a genus as has previously been assumed. Hewitt thus . ) concluded, after a brief discussion of largely superficial and primitive features, that 0 1 0 "Rhoptrope/la may perhaps be regarded as representing the earliest Rhoptropuscondition 2 d more or less unchanged" (Hewitt 1937: 203). e t a Loveridge reiterated Hewitt's (1937) conclusions and presented a table of comparisons d ( illustrating why relationship with Phelsuma untenable (Loveridge 1947:203). This table r was e h was based upon differences and no attempt was made to compile similarities between s i l b Rhoptrope/la and Phelsuma. Again the species of Phelsuma compared with Rhoptropella u P to were from that part of the fonner genus which bears least resemblance the latter (see e h t below). Although concurring in his general opinions with those of Hewitt (1937) concerning y b the relationships of Rhoptropella, Loveridge reversed the apparent phylogeny, without d e giving any reasons for doing so, by stating that" Rhoptropella appears to be immediately t n a descended from Rhoptropus" (Loveridge 1947:294). Fitzsimons (1943) does not contribute r g anything of substance to help settle this argument. e c n It is my contention that, after a thorough re-examination of the genera Rhoptropus. e c i l Rhoptropella and Phelsuma, Schmidt (1934) was correct in placing Rhoptropella r e (Rhoptropus oce/latus at the time) into synonymy with Phelsuma and I am therefore d n resurrecting the combination Phelsuma ocellata (Boulenger, 1885). Rhoptropella Hewitt, u y a 1937 thus becomes ajunior synonym of Phelsuma Gray, 1825. This, obviously, extends the w e range of Phelsuma considerably and I would thus also like to put forward some views about t a why such a distribution is now tenable and acceptable; information which Schmidt did not G t e have available to him. n i b a S y b d e c u d o r p e R 396 ZOOLOGICA AFRICANA VOL 12 A reassessment of the interrelationships of Rhoptropel/a Hewill, 1937 In Loveridge's (1947) summary of the information then available concerning the relation ships of Rhoptropel/a he stated that the generic diagnosis of this genus was almost identical to that of Phelsuma, but that it differed in a number of minor characters. Repeated reference was made, however, to Phelsuma mutabilis and Phelsuma breviceps which did not fit the "usual" characters of Phelsuma. It was apparent, then, that Rhoptropel/a did not differ markedly from all members of the genus Phelsuma, but only from some of them.