Prionodactylus argulus, : Boulenger, 1885

Doan, Tiffany M., 2003, A new phylogenetic classification for the gymnophthalmid genera Cercosaura, Pantodactylus and Prionodactylus (Reptilia: Squamata), Zoological Journal of the Linnean Society 137 (1), pp. 101-115 : 105-106

PRIONODACTYLUS ARGULUS (PETERS)

Cercosaura (Pantodactylus) argulus Peters, 1862: 184 . Prionodactylus argulus: Boulenger, 1885: 391 . Prionodactylus oshaughnessyi Boulenger, 1885: 392 . Prionodactylus holmgreni Andersson, 1914: 9 . Prionodactylus columbiensis Werner, 1916: 306 .

When Uzzell (1973) synonymized P. oshaughnessyi with P. argulus , he did so because he did not find sufficient differences between the two species based on the four specimens of P. oshaughnessyi that he examined. Avila-Pires (1995) examined 90 individuals that she considered to be P. oshaughnessyi and presented evidence for its recognition as a distinct species. She provided a table of seven characters that differed between the species and also used two other characters as supporting evidence (numbers of transverse rows of ventral scales and transverse rows of dorsal scales). In many cases the meristic characters had overlapping ranges that made interpretation difficult. I examined 39 individuals for seven of her nine characters and 50 other external morphological characters to determine if a significant difference was in fact apparent.

Upon examination of specimens for this study I could not distinguish between the species using the characters designated by Avila-Pires (1995) because the defining characters did not appear to be correlated with each other. Therefore, I chose one of those characters, lateral scale size, to name individuals. Avila- Pires (1995) states that P. argulus has lateral scales that are moderately smaller than the dorsals, whereas P. oshaughnessyi has lateral scales that are distinctly smaller than the dorsals. Although this character could appear to be subjective, it was actually obvious as to which lateral scale condition the specimen possessed. Therefore, in all subsequent analyses I grouped the specimens based on this character.

Of the nine characters of Avila-Pires (1995), seven were examined in this study: lateral scale size, number of femoral pores in males and females, presence of preanal pores, number of scales in a transverse ventral row between pores, transverse rows of ventrals, and transverse rows of dorsals. Of the other two characters, scales around midbody is too variable to be reliable (because an exact scale position for counting was not stated) and tail/snout-vent length ratio was not possible due to the fact that most specimens did not have complete, original tails. To determine if Avila- Pires’s (1995) characters in fact may be used to differentiate between species, I constructed a correlation matrix of five of the Avila-Pires characters for which I had data for 23 individuals ( Table 3). If these characters serve to diagnose the two species, each of the characters should correlate strongly with one another. This was not the case - only number of ventral scale rows and presence of preanal pores were moderately negatively correlated with each other (R = - 0.65235). None of the other characters displayed high correlation with any other.

To simultaneously examine multiple characters, a principal components analysis (PCA) was performed. The analysis utilized 49 characters, including seven of those used by Avila-Pires (1995), to determine if distinct groups were obvious from the data. As can be seen in Fig. 1 , no real structure is apparent and there appears to be intergradation between the two putative species. A cluster analysis of 55 characters showed the same pattern of no separation of species based on morphology ( Fig. 2 ). Specimens did not convincingly cluster by species or by geographical location. Thus, each analysis suggests that P. argulus represents only one species, with P. oshaughnessyi being a junior synonym (in agreement with Uzzell, 1973).

Although specimens did not cluster by species, the cluster analysis suggested a possible geographical trend ( Fig. 2 ), potentially representing clinal variation within the species. In order to examine this, I conducted a multiple regression of the five Avila-Pires (1995) characters on latitude. This type of analysis is possible because the specimens represented here occur almost in a linear distribution, following the eastern Andean foothills in a north–south direction. The regression was significant (R = 0.87616; F = 9.2511; P = 0.00046). This implies significant clinal variation in the five characters, which further refutes the recognition of two separate taxa ( Endler, 1977). Even though specimens from the entire geographical range of the species were not examined, the specimens examined for this study did cover the entire range of character variation as those examined by Avila-Pires (1995). Thus, the variation found by Avila-Pires (1995) appears to have been clinal in nature and not due to distinct species.

Figures

Figure 1. Principal components analyses of Prionodactylus argulus based on 49 variables. Diamonds represent ‘Prionodactylus oshaughnessyi’ individuals; circles represent P. argulus (sensu stricto) individuals.

Figure 2. Cluster analysis of 23 specimens of Prionodactylus argulus for 55 characters. Specimens are listed by the department or province in which their locality lies and the country. (A) indicates that the specimen was classed as P. argulus (sensu stricto) and (O) indicates that the specimen was classed as P. oshaughnessyi. Species classifications were based on lateral scale size (see text).