Tuesday, May 31, 2016

[Herpetology • 2016] Resolving the Higher-Order Phylogenetic Relationships of the Circumtropical Mabuya group (Squamata: Scincidae): An Out-of-Asia Diversification

• Concatenated and species tree approaches resolve intergeneric relationships of Mabuya group.
• Southeast Asian lineages are found to be non-monophyletic, supporting Southeast Asian origin of the group.
• Middle-Eastern Trachylepis form a distinct clade and are transferred to a resurrected genus.
Eutropis is rendered polyphyletic by placement of E. novemcarinata sister to Dasia, and a new genus name is provided.

Despite an abundance of phylogenetic studies focused on intrageneric relationships of members of the Mabuya group, the intergeneric relationships between the genera within the circumtropical Mabuya group have remained difficult to resolve. The most-persistent unresolved regions of the phylogeny of the group include: (1.) the placement of the Middle-Eastern Trachylepis with respect to the Afro-Malagasy Trachylepis and its taxonomic status; (2.) the phylogenetic position of the Cape Verdean Chioninia within the larger Mabuya group; (3.) support for the placement of Dasia with respect to the entire group; and (4.) the phylogenetic placement of Eutropis novemcarinata with respect to other Eutropis and Dasia. In this study, we include representatives of all these taxa as well as African Eumecia and Neotropical Mabuya. We seek to address these phylogenetic and systematic issues by generating a well-resolved and supported phylogeny for the Mabuya group as a whole that can be used to develop a stable taxonomy and reconstruct the geographic patterns of diversification within the group. To meet these goals, we built a large multi-locus dataset of 11 markers (nine nuclear and two mitochondrial), and performed concatenated and species tree analyses to generate a well-supported phylogeny for the group. Statistical topology tests reject the monophyly of Middle-Eastern Trachylepis with Afro-Malagasy Trachylepis, and to reflect monophyly we place the Middle-Eastern species into a previously described genus, Heremites. Cape-Verdean Chioninia are resolved as the strongly supported sister-group to Afro-Malagasy Trachylepis. Monophyly of the Southeast-Asian genera, Eutropis and Dasia, is not supported, with a clade composed of Dasia + Eutropis novemcarinata more closely related to the rest of the Mabuya group than to the remaining Eutropis. The phylogenetic position of E. novemcarinata renders Eutropis polyphyletic, and we therefore describe and place E. novemcarinata into a new monotypic genus, Toenayar, to preserve monophyly among the genera. In light of these novel findings, we review and discuss the historical biogeography of the entire Mabuya group.

Keywords: species tree; Toenayar gen. nov; novemcarinata; Heremites; Mabuyidae; Mabuyinae


Toenayar gen nov.

  Background: As the most significant line of evidence towards the naming of this genus is genetic, it is possible that other species within Southeast Asia that do not yet have genetic data may also be included within this new genus. Within Eutropis, the species that currently lack genetic data are E. chapaensis, E. darevskii, E. englei, E. floweri, E. gansi, E. innotata, E. quadratilobus, and E. tytleri. Eutropis innotata, in particular, possesses a transparent disc in the eyelid ( Smith 1935) and has been interpreted to be morphologically similar to E. novemcarinata ( Horton 1973), and is, therefore, a potential candidate species for the new genus. Within Dasia, D. griffini, D. nicobarensis, and D. semicincta do not have any genetic data, however D. griffini and D. semicincta were formerly synonymized with Dasia olivacea ( Greer 1970) suggesting that they are closely related, if not conspecific, with D. olivacea. Vietnascincus rugosus, with only the two type specimens known to date ( Darevsky and Orlov 1994), is expected to be part of the Mabuya group, and it is possible that future studies may find it to be a member of the new genus as well. Lamprolepis vyneri, which has been shown to be part of the Mabuya group ( Linkem et al. 2013), is nested within Dasia based on the available ND2 data (results not shown) and is likely to be transferred to Dasia upon further investigation. Thus, although there are some taxa that may ultimately be referable to the new genus, in the absence of any positive evidence of this, we regard it as monotypic.

 Composition: Toenayar gen. nov. includes only its type species Toenayar novemcarinata (Anderson) [จิ้งเหลนเกล็ดสัน].

 Etymology: The generic name comes from the mythology of Myanmar, in which the Toenayar (Pronunciation: “Toh-Ay-Nah-Yar), from the Burmese language, is a mythical dragon or serpent with four legs. The Burmese language has no grammatical gender, but we treat the scientific name, Toenayar, as feminine.

 Description: A medium-sized (SVL to 90 mm), robust skink with well-developed limbs, 32–34 scale rows around the midbody, 7–11 keels on the dorsal scales, adpressed hindlimbs reaching the wrist of the forelimb, 17–21 subdigital lamellae under toe IV, supranasals in contact or slight separation, prefrontals separated or in slight contact, parietals almost always separated by interparietal, frontal in contact with first and second supraocular, one pair of nuchals present, equal in width to two or three adjacent rows of cycloid scales; ear opening with two anterior lobules; 26 presacral vertebrae; palatal rami separated (i.e. open palate); males possess three enlarged, opaque-white heel scales, whereas females do not (Horton, 1973, Smith, 1935 and Taylor, 1963; this study). Color of dorsum light brown, with irregular black spotting; color of thick lateral stripes dark black-brown beginning at the nostril and diminishing posterior to the base of the tail; color of venter cream.

Diagnostic Comparison: Toenayar differs from Mabuya in the number of presacral vertebrae (26 vs. > 27, respectively) and from most species by having keeled (versus smooth) dorsal scales ( Greer et al., 2000 and Mausfeld et al., 2002); from Eumecia in having pentadactyl limbs (versus limb and digital reduction) and Eumecia and Eutropis by having an undivided transparent disk in the lower eyelid and 7–11 keels on the dorsal scales (versus lower eyelid scaly or having greater or less than three keels on dorsal scales); from Dasia by the separation of the palatine bones (open palate) and further by the possession of an undivided transparent disk in the lower eyelid; from Heremites and Trachylepis by the presence of enlarged, differentiated heel scales in males (and enlarged, undifferentiated heel scales in females), and additionally from the vast majority of Trachylepis by possessing 7–11 keels on the dorsal scales; and from Chioninia and Vietnascincus by having 32–34 midbody scale rows and no postnasal scale. Toenayar shares with it’s closest relative, Dasia, male possession of enlarged, differentiated heel scales, however in Toenayar there are three enlarged scales and in Dasia there are two ( Greer 1970).

The relative degree of external morphological conservatism among members of the Mabuya group has led to a lag in the full understanding and appreciation of the immense diversification that has occurred in the complex. Species within the group have spread across the world making unprecedented dispersals across huge oceanic barriers on several occasions. They have adapted to a diverse array of environments, such as arboreal (e.g., Dasia), semi-aquatic (e.g., Trachylepis ivensii), rupicolous (e.g., Trachylepis sulcata and Trachylepis makolowodei), limb-reduced (Eumecia), and also human-commensalism (e.g., Eutropis multifasciata). Furthermore, species within the group have also evolved an extremely wide range of reproductive strategies from oviparity (assumed as the ancestral condition) to several independent derivations of viviparity, and even to some of the most extreme specializations of fetal membranes observed in all Squamates (Mabuya heathi, Eumecia, Trachylepis ivensii; Blackburn and Flemming, 2009). Finally, with the well-supported intergeneric phylogeny presented in this publication, it is now possible to investigate the incredible diversification that has occurred in the Mabuya group in an evolutionary framework.

Benjamin R. Karin, Margarita Metallinou, Jeffrey L. Weinell, Todd R. Jackman and Aaron M. Bauer. 2016.  Resolving the Higher-Order Phylogenetic Relationships of the Circumtropical Mabuya group (Squamata: Scincidae): An Out-of-Asia Diversification. Molecular Phylogenetics and Evolution