Plestiodon

Brandley, Matthew C., Fls, Hidetoshi Ota, Hikida, Tsutomu, Oca, Adrián Nieto Montes De, Fería-Ortíz, Manuel, Guo, Xianguang & Wang, Yuezhao, 2012, The phylogenetic systematics of blue-tailed skinks (Plestiodon) and the family Scincidae, Zoological Journal of the Linnean Society 165 (1), pp. 163-189 : 181-182

A NEW PLESTIODON TAXONOMY

Our results demonstrate that the existing supraspecific taxonomy of Plestiodon ( Taylor, 1935; Lieb, 1985; Hikida, 1993) does not accurately reflect monophyletic species groups, and therefore requires substantial revision. Although our study infers the close phylogenetic relationships of the Eumeces s.l. genera ( Eumeces s.s., Eurylepis , Mesoscincus , and Plestiodon ), sinking these genera into Eumeces for convenience is not justified, as this clade would also contain Scincus and Scincopus . As Scincus Laurenti, 1768 has a priority, any attempt to lump these lineages into a single genus would instead require that the name Scincus be applied to this larger assemblage. As there is absolutely nothing to be gained by this action, we therefore retain the present generic taxonomy.

If one purpose of taxonomy is to promote the efficient dissemination of phylogenetic information, then clearly the current superspecific taxonomy of Plestiodon requires reorganization. There has been extensive and continuing debate on the relative merits of Linnean ranks (e.g. Dominguez & Wheeler, 1997; Cantino et al., 1999; Cantino, 2000; de Queiroz & Cantino, 2001; Nixon, Carpenter & Stevenson, 2003; de Queiroz, 2006), as well as the criteria for applying names to a phylogenetic tree (e.g. node based versus stem based; de Queiroz & Gauthier, 1990, 1992, 1994). All of these arguments may have merits to a varying degree. In the case of Plestiodon , we have chosen to preserve the use of the species ‘groups’ and ‘series’ informal names rather than develop new names for each node. First, there is a long history of use of ‘ Eumeces ’ species groups beginning with Taylor (1935) and continuing through the present day. Thus, provided they are revised to reflect the most recent phylogenetic information, these groupings may continue to be useful. Secondly, the taxonomic history of Plestiodon has changed little over time, and there exist few junior generic synonyms (other than Neoseps Stejneger, 1910 and Pariocela Fitzinger, 1843 ) that may be resurrected as familiar clade uninominal names. Therefore, in this case, adopting a uninominal clade naming system, in which new names are created, would defeat taxonomy’s goal of efficient transfer of information in this case. Third, maintaining these ranks does not preclude incorporating some criteria of phylogenetic taxonomy, and we adopt some of these principles in naming clades below.

Our phylogeny demonstrates that those morphological characters once thought to diagnose supraspecific groups of Plestiodon species ( Taylor, 1935; Lieb, 1985) are instead cases of convergent evolution or retention of plesiomorphies. Indeed this explains why the results of our phylogenetic analysis differ so markedly to the phylogenetic/taxonomic analyses of Taylor (1935) and Lieb (1985), which relied on morphological characters. Therefore, in the context of our phylogeny, there exist very few characters that diagnose interspecific relationships in Plestiodon , and we must instead rely on several admittedly subjective criteria to determine which clades to name. First, we attempt to preserve much of the historical taxonomy that was not radically changed by our phylogenetic analysis (e.g. the latiscutatus group and capito group). Secondly, when possible, we name clades with some biogeographic cohesion (e.g. the brevirostris group that inhabits Middle America; see also Fería- Ortíz et al., 2011). Finally, in some cases, we name clades based on their unique morphology when compared with close relatives (e.g. P. reynoldsi and P. quadrilineatus ).

All names are considered node-based names and are defined as the least inclusive clade containing all of the listed taxa (i.e. ‘specifier taxa’; Sereno, 2005; PhyloCode, 2007), except where noted. Note that the subspecies of P. brevirostris are elevated to species, bringing the total number of species to 43. However, we emphasize that this is likely to underestimate species diversity, especially within the brevirostris group (clade C 1 in Fig. 3 ).

Species that are not monophyletic are indicated to note that this revised taxonomy does not necessarily capture the species diversity, and is in need of additional phylogenetic and taxonomic study. We emphasize that these taxonomic ranks by themselves are not comparable in terms of either genetic diversity or evolutionary time (however, estimates of their ages can be found in Brandley et al. (2011).

Plestiodon Duméril & Bibron, 1849

fasciatus species series (clade C in Fig. 3 )

anthracinus species group

P. anthracinus Baird, 1849

brevirostris species group

P. bilineatus Cope, 1880

P. brevirostris (Günther, 1860)

P. colimensis 1 ( Taylor 1935)

P. copei (Taylor, 1933)

P. dicei (Ruthven & Gaige, 1933)

P. dugesii (Thominot, 1883)

P. indubitus 2 (Taylor, 1933)

P. lynxe (Wiegmann, 1834)

P. ochoteranae (Taylor, 1933)

P. parviauriculatus (Taylor, 1933)

P. parvulus (Taylor, 1933)

P. sumichrasti (Cope, 1867)

egregius species group

P. egregius (Baird, 1859)

fasciatus species group

P. callicephalus (Bocourt, 1879)

P. fasciatus (Linnaeus, 1758)

1 Not sampled in this study and thus not included as specifier taxa of the clade name. Inclusion of these species is based solely on previous taxonomic studies based on morphological data.

2 Molecular evidence indicates that this species is not monophyletic.

P. inexpectatus ( Taylor, 1932)

P. laticeps (Schneider, 1801)

P. multilineatus 1 (Tanner, 1957) P. multivirgatus Hallowell, 1857

P. obsoletus Baird & Girard, 1852 P. septentrionalis Baird, 1859 P. tetragrammus Baird, 1859

longirostris species group

P. longirostris Cope, 1861

reynoldsi species group

P. reynoldsi (Stejneger, 1910)

skiltonianus species group

P. gilberti 2 (Van Denburgh, 1896) P. lagunensis (Van Denburgh, 1895) P. skiltonianus 2 Baird & Girard, 1852 latiscutatus species series (clade B in Fig. 3 ) capito species group

P. capito (Bocourt, 1879)

P. liui 1 ( Hikida & Zhao 1989)

P. popei 1 (Hikida 1989)

P. tunganus (Stejneger, 1924)

latiscutatus species group (defined by the presence of a fan-shaped upper secondary temporal scale with emarginated posterior margin and keeled postanal scales ( Hikida, 1993) P. barbouri (Van Denburgh, 1912)

P. elegans (Boulenger, 1887)

P. japonicus (Peters, 1864)

P. latiscutatus Hallowell, 1861

P. marginatus Hallowell, 1861

P. stimpsonii (Thompson, 1912)

chinensis species series (clade A in Fig. 3 ) chinensis species group

P. chinensis (Gray, 1838)

P. coreensis 1 (Doi & Kamita, 1937) P. kishinouyei (Stejneger, 1901) P. tamdaoensis (Bouret, 1937)

quadrilineatus species group

P. quadrilineatus Blyth, 1853

Figures

Figure 3. A continuation of Figure 2 showing the inter-relationships of Plestiodon species. Nodes with open circles are supported with a posterior probability of 1.0. Nodes with a posterior probability <1.0 are indicated with numbers above or below the node. Nodes with a posterior probability of <0.50 are collapsed. Branch lengths represent means of the posterior distribution. Clades A, B1, B2, and C1–C5 refer to the clades discussed in the text.