Leiolopisma (Sadlier, 1987)

Sadlier, Ross A., Bauer, Aaron M., Shea, Glenn M. & Smith, Sarah A., 2015, Taxonomic Resolution to the Problem of Polyphyly in the New Caledonian Scincid Lizard Genus Lioscincus (Squamata: Scincidae), Records of the Australian Museum 67 (7), pp. 207-224 : 208-210

Leiolopisma and its role in

New Caledonian skink systematics

Greer’s early work on lygosomine skinks identified the “greatest single taxonomic problem with the Lygosominae ” as the “delimitation and relationships of genera” ( Greer, 1970, p. 171), and in particular the relationships within “ Leiolopisma ” “as a major unresolved problem in skink systematics” ( Greer, 1970, p. 179). Generic concepts were refined by Greer (1974), who diagnosed a number of monophyletic genera from Malcolm Smith’s (1937) Section Leiolopisma , and allocated these and related genera to three major groups based on a suite of osteological and scalation characters. Within this scheme of relationships, the New Caledonian skink species known at the time all resided in genera placed in a large group of taxa, later formally referred to as the “ Eugongylus Group” ( Greer, 1979). The majority of the New Caledonian species were retained within a redefined Leiolopisma , which also included species from New Zealand, Australia (including Lord Howe Island), and Mauritius in the Indian Ocean. Greer (1974, p. 17) seems to have regarded Leiolopisma as a (monophyletic) lineage. However, the genus was weakly diagnosed, with exceptions amongst the included species for almost every diagnostic character presented. The significance of Greer’s early contributions to the systematics of the New Caledonian skinks lies with being the first worker to assess relationships and diagnose natural groups among related lygosomine skinks in a contemporary phylogenetic context, and in doing so provided a considerably more robust framework within which to investigate interspecific and intergeneric relationships of the New Caledonian taxa. The major groups of genera identified by Greer within the Lygosominae have proven remarkably robust, and subsequent studies (Austin & Arnold, 2006; Brandley et al., 2005; Honda et al., 2000, 2003; Pyron et al., 2013; Rabosky et al., 2007; Skinner et al., 2011; Whiting et al., 2003) have largely supported these groupings.

Field studies initiated in 1978 were the basis of a monograph of the scincid lizards by Sadlier (1987), the first review in over 70 years, which recognized a doubling in the number of endemic species to 24 and a similar increase in the number of genera from 4 to 10, of which 7 were strictly endemic. Sadlier (1987) proposed several putatively monophyletic genera ( Caledoniscincus , Marmorosphax and Sigaloseps , and a resurrected Tropidoscincus Bocage, 1873 ) to accommodate most of the New Caledonian species formerly assigned to Leiolopisma . All were defined by suites of apomorphic morphological character states, the polarity of which was determined within the context of Greer’s (1979) Eugongylus group of skinks. However, four species with relatively plesiomorphic morphology ( nigrofasciolatus Peters , greeri Böhme , steindachneri Bocage and novaecaledoniae Parker ) were retained within the “cosmopolitan” Leiolopisma , though two of these ( nigrofasciolatus and greeri ) were recognized at the time as probable sister taxa in a putative sublineage. Subsequently three more New Caledonian species were added to the genus, Leiolopisma tillieri Ineich & Sadlier in 1990, maruia Sadlier, Whitaker & Bauer in 1998 (by which time the New Caledonian Leiolopisma had been moved to Lioscincus , see below), and vivae Sadlier, Bauer, Whitaker & Smith (as Lioscincus ) in 2004.

The members of “ Leiolopisma ” at the time of Sadlier’s monograph (1987) also included all New Zealand skinks (20 species), a group of Australian skinks (13 species that now represent Bassiana , Pseudemoia in part, and Niveoscincus in part), the Lord Howe/ Norfolk Island species lichenigera , a single Fijian species ( alazon Zug), and the type species for the genus, Leiolopisma telfairii from Mauritius. The diagnosis for “ Leiolopisma ” given by Greer (1970) contained both “primitive” and “derived” character traits with both states present for some characters (frontoparietal scales), but was later modified by Sadlier (1987) to include only the single most unifying apomorphy to define the genus, lack of supranasal scales in most species. Further, limited knowledge of morphological variation for some characters and the simplistic assumption that some states, such as the presence of supranasal scales and presence of a scaled lower eyelid (both considered plesiomorphic) were homologous across genera, would ultimately prove to be misleading, and clouded interpretations of relationships within this group of species well into the future. In effect “ Leiolopisma ” at this time remained (as before) a genus of convenience rather than one reflecting defined evolutionary relationships, and the New Caledonian taxa retained within it ( Sadlier, 1987) were the residual species lacking a distinct supranasal scale that could not be otherwise accommodated within any of the existing putatively monophyletic genera within the Eugongylus group.

A decade after Greer defined the Eugongylus group, two not entirely concordant works were published which were to influence generic concepts of this group of skinks in the years following, and in particular the dynamics of taxa formerly included in the all-encompassing “ Leiolopisma ” of earlier studies. In one Greer (1989) diagnosed a Pseudemoia subgroup within the Eugongylus group on the basis of a single apomorphy not observed in other major groups of skinks, fusion of the elements of the atlantal vertebra, for a group of Australian taxa (covering 12 genera), but also stated as including taxa from New Guinea and New Caledonia (though these were not specifically listed). The Pseudemoia group as conceived by Greer comprised an extensive suite of taxa centred on the Coral and western Tasman Seas, but explicitly excluded part of the New Caledonian skink fauna, and in doing so argued for nonmonophyly of the group of endemic New Caledonian skink lineages. Concurrently Hutchinson et al. (1990) reviewed the Australian species previously assigned to Leiolopisma using primarily genetic criteria. This study further promoted the dismembering of the large, still polyphyletic “ Leiolopisma ” as it existed at the time, by transferring the Australian species formerly in the genus to five (four newly erected) putatively monophyletic (endemic) genera, and suggesting Leiolopisma be restricted to the type species telfairii . The genera proposed by Hutchinson et al. (1990) were identified by microcomplement fixation comparisons, and supported by a suite of putative morphological apomorphies consistent with these genetic groupings. In the process, genetic comparisons were made with a very limited suite of extralimital taxa that included two species from New Caledonia, two from New Zealand, and the type species for Leiolopisma , Scincus telfairii Desjardin 1831 , from Mauritius.

The results of the genetic study by Hutchinson et al. (1990) had two implications for New Caledonian skink systematics. Firstly the New Caledonian and New Zealand species of Leiolopisma were identified as not being congeneric with, or particularly close to, the Australian taxa, and neither was the type species telfairii . Secondly, while the condition of the elements of the atlantal arch was invariant for the taxa in most of the genera proposed by Hutchinson et al., it was variable between the species in one of the genera proposed. Niveoscincus , with eight species from Tasmania and adjacent south-east Australia, included one species with the apomorphic condition of having the atlantal arches of the first cervical vertebrae fused to the intercentrum (palfreymani), while the remaining species in the genus had the plesiomorphic condition in which all elements are separate, in effect suggesting the possibility of multiple evolutionary events for this character state, which had been the sole evidence for monophyly of Greer’s Pseudemoia group.

The actions of Hutchinson et al. (1990) in restricting Leiolopisma to the type species telfairii prompted the transfer of the residual New Caledonian “ Leiolopisma ” to Lioscincus (type species Lioscincus steindachneri Bocage, 1873 ) by Bauer & Sadlier (1993), the only available generic name among the constituent species. The lack of apomorphies defining Lioscincus and its probable polyphyly were explicitly acknowledged at that time, the action being a nomenclatural necessity rather than an inference of intrageneric cohesiveness. For the same reason the New Zealand “ Leiolopisma ” were transferred to Oligosoma by Patterson and Daugherty (1995). These actions have resulted in the concept of a significantly redefined Leiolopisma restricted to a single extant taxon, the type species telfairii , and the fossil species mauritianus from the Mascarene Islands ( Arnold, 1980), and the fossil species ceciliae from Réunion (Arnold & Bour, 2008). However, one species, described as Leiolopisma alazon Zug in 1985, has not been considered in these recent studies. The species occurs on the outer islands of Fiji, and until recently was only known from the type series, and no tissue samples have been available for genetic studies. It currently resides within the Lygosominae ( Zug, 2013) , but otherwise its affinities remain obscure.