Ablepharus, Fitzinger, 1824

Vergilov, Vladislav & Zlatkov, Boyan, 2024, Morphology of hemipenes and its taxonomic implication in the fused eyelids species of the genus Ablepharus (Squamata: Scincidae), Zoologischer Anzeiger 312, pp. 79-91 : 83

4.1. On Ablepharus taxonomic issues, phylogeny and hemipenial morphology

Akin to Mabuya (S´anchez-Martínez et al., 2020), Ablepharus suffers from nomenclatural and taxonomical issues rooted in taxonomic descriptions based on external morphological characters (colouration, size, pholidosis, etc.; see Mertens, 1952; Fuhn, 1969a,b, 1970; G¨oçmen et al., 1996; Schmidtler, 1997) and related to the small number of examined specimens (usually from only a few localities). The scarcity of diagnostic characters and the lack of sufficient data on morphological variation results in difficulties regarding the interpretation of some taxa. Nevertheless, based on the published literature Karamiani et al. (2021b) synthesised a few of the external morphological characters and created an identification key to the Iranian species of the genus. However, the key contains some generalizations, which cause practical difficulties in species determination using the respective characters (e.g., “prefrontals usually forming a median suture”). Based on our observations of numerous (over 400) A. kitaibelii specimens (unpublished data), many of the traditionally used diagnostic characters either partially overlap or are highly variable even within a single population (e.g., number of supralabials, scales around the midbody, nuchals, etc.). As a result, the number of taxa within Ablepharus is still disputed. For example, Uetz et al. (2023) and Karamiani et al. (2021b) treat A. budaki anatolicus as a species – A. anatolicus . This assumption is probably rooted in a few molecular studies ( Poulakakis et al., 2005; Skourtanioti et al., 2016; Bozkurt and Olgun, 2020) which have revealed a basal taxon from the Island of Kastellorizo, Greece and the area around the Turkish Town of Kaş. It is likely that the specimens from the region have been assigned to this taxon by presumption. Understandably, none of these works provides a nomenclatural act of raising the subspecies to species. The authors of these publications consider the data inconclusive and claim that additional specimens are needed. Nevertheless, the " A. anatolicus " combination continues to persist in both the published literature and in internet sources. By assigning A. bivittatus to the genus Asymblepharus, Bozkurt and Olgun (2020) provided a new combination and generated even further confusion. Additional complications stem from the assignment of some species to different subfamilies. These issues demonstrate the need for a thorough revision not only of Ablepharus but all allied lineages as well ( Shea, 2021). The boundaries of the genus Ablepharus were recently expanded by the synonymisation with Himalblepharus and Asymblepharus ( Mirza et al., 2022) . The current taxon Ablepharus remains poorly defined from a morphological point of view as it was never formally re-described and a diagnosis was never formulated. The present definition of Ablepharus is based mainly on molecular phylogeny ( Mirza et al., 2022). That said, it should be emphasised that the ablepharine skinks with completely fused eyelids form a well-supported monophyletic clade nested within Ablepharus ( Mirza et al., 2022) . Further taxonomic studies may recover its subgeneric or even generic status.

The phylogenetic position of the fused eyelids representatives of the genus Ablepharus was much more controversial in the past, particularly considering the pioneering study of Pyron et al. (2013), in which A. budaki and A. kitaibelii plus A. chernovi formed a well-supported clade with a set of lygosomine species, while A. pannonicus was grouped with Asymblepharus alaicus Elpatjevsky, 1901 into a relatively distant clade sister to a large “ Sphenomorphus group” radiation. This phylogeny clearly makes the genus Ablepharus paraphyletic. In a similar manner, Datta-Roy et al. (2013) recovered the clade Ablepharus grayanus plus Asymblepharus himalayanus (Günther, 1864) as sister to the “ Sphenomorphus group”. Macey et al. (2006) demonstrated the close relationship between A. pannonicus and the members of the genus Asymblepharus [represented by A. alaicus and A. sikimmensis (Blyth, 1854) ], which formed a well-supported clade. In addition to molecular data, the representatives of the genus Asymblepharus were grouped by a set of morphological traits ( Jeriomtshenko, 1987; 2002), although the existence of this genus was neglected in some studies (see Shea and Greer, 2002) and the species were commonly attributed to the genus Scincella . Based on external morphology, Jeriomtshenko and Szczerbak (1986) regarded A. grayanus and A. pannonicus as closely related. The phylogeny of Mirza et al. (2022) (generally repeated by Liang et al., 2024), resolved many issues with the “ablepharine” genera and recovered the monophyly of the clade. According to their phylogeny, Ablepharus alaicus and Ablepharus eremchenkoi (Panfilov, 1999) (both formerly in Asymblepharus ) are basal to the fused eyelids ablepharine skinks. Sister to their clade is the clade of the former (now assigned to Ablepharus ) Asymblepharus species: A. nepalensis , A. mahabharatus , A. sikimmensis , A. cf. ladacensis , A. himalayanus . However, the available phylogenies of the group are based on various genetic markers from different taxa, e.g., ND 2, 12S, 16S, etc. ( Shea, 2021) and on very different taxon sampling (some taxa are represented by a single sample), and therefore cannot be accepted unequivocally. According to Jeriomtshenko and Szczerbak (1980), A. lindbergi is morphologically related to Asymblepharus . No molecular data is available for A. lindbergi and A. darvazi . To date, there have been no molecular studies based on type material.

The animal genitalia are rapidly diverging structures ( Eberhard, 1985). Traditionally, in certain animal groups, including reptiles, the morphology of genitalia has been used for creation of taxonomic and sometimes phylogenetic hypotheses (e.g., Keogh, 1999; Zaher, 1999; Nunes et al., 2014). An alignment of a cluster based on hemipenial morphology with a phylogeny based on other characters (e.g., molecular) is an intriguing approach, and may reveal discrepancy between divergence of a certain structure and divergence of the species.

The grouping ( Fig. 4A ), based on slender and robust lobes, does not overlap in general to the molecular phylogeny of Mirza et al. (2022) ( Fig. 4B ); phylogenetically, A. pannonicus is closer to A. deserti and A. kitaibelii is a sister taxon to A. chernovi (contrary to the morphological cluster). The relationship between A. budaki and A. rueppellii , is supported by both molecular phylogeny and morphology of the hemipenes.

Figures

Fig. 4. Morphological cluster analysis UPGMA (Unweighted Pair Group Method with Arithmetic Mean) (A; black lines) of hemipenes of species of the fused eyelids Ablepharus species (outgroup: Trachylepis capensis) aligned with phylogenetic cladograms. B (orange lines) adapted from Fig. 1 in Mirza et al. (2022); C (green lines) adapted from Fig. 2 in Karamiani et al. (2021a). Original trees rescaled with distances preserved. * – taxon not included in the morphological cluster. Inset photo of A. kitaibelii: courtesy by A. Dyugmedzhiev.