Species delimitation in the Gehyra nana (Squamata: Gekkonidae) complex: cryptic and divergent morphological evolution in the Australian Monsoonal Tropics, with the description of four new species

Abstract

Recent advances in molecular genetic techniques and increased fine scale sampling in the Australian Monsoonal Tropics (AMT) have provided new impetus to reassess species boundaries in the Gehyra nana species complex, a clade of small-bodied, saxicolous geckos which are widely distributed across northern Australia. A recent phylogenomic analysis revealed eight deeply divergent lineages that occur as a series of overlapping distributions across the AMT and which, as a whole, are paraphyletic with four previously described species. Several of these lineages currently included in G. nana are phenotypically distinct, while others are highly conservative morphologically. Here we use an integrated approach to explore species delimitation in this complex. We redefine G. nana as a widespread taxon with complex genetic structure across the Kimberley of Western Australia and Top End of the Northern Territory, including a lineage with mtDNA introgressed from the larger-bodied G. multiporosa. We describe four new species with more restricted distributions within the G. nana complex. The new species are phylogenetically divergent and morphologically diagnosable, and include the relatively cryptic G. paranana sp. nov. from the western Northern Territory, the large-bodied G. pseudopunctata sp. nov. from the southern Kimberley ranges, G. granulum sp. nov., a small-bodied form with granules on the proximal lamellae from the north-west and southern Kimberley ranges and the small-bodied G. pluraporosa sp. nov. restricted to the northern Kimberley. Our revision largely stabilises the taxonomy of the G. nana complex, although further analyses of species limits among the remaining mostly parapatric lineages of G. nana sensu stricto are warranted.

Spots before the eyes: revision of the saxicoline geckos of the Gehyra punctata (Squamata: Gekkonidae) species complex in the Pilbara region of Western Australia

“…For morphology, phenotypic expression of colouration can be highly variable and convergent, with patterns fading in preservation leading to the loss of characters. Moreover, the body plan of Gehyra is highly conserved across this old and widespread group, with only subtle changes in shape across widely divergent lineages (Heinicke et al 2011;Ashman et al 2018;Doughty et al 2018;Kealley et al 2018). However, the benefit of working with morphology is that many potentially informative characters can be inexpensively assessed.…”

“…Gehyra can also be very variable in appearance within species (e.g. Sistrom et al 2012;Hutchinson et al 2014;Doughty et al 2018). The presence of so many similar-looking species in one area resulted in Storr taking a conservative stance, viewing G. 'punctata' as a variable species, ultimately deciding to collapse them in to a single taxon.…”

“…-F.J. Mitchell on Gehyra (1965, p. 302) Gehyra is a 'taxonomist's nightmare'… -M. King (1979, p. 376) Geckos of the genus Gehyra are among the most taxonomically confusing within the Australian herpetofauna owing to their conservative body form, widely varying characters within taxa, remote locations for many species complexes and poor preservation of colour patterns in museum specimens Sistrom et al 2009Sistrom et al , 2014Doughty et al 2012Doughty et al , 2018Kealley et al 2018). Recently, progress has been made resolving the affinities of Gehyra to other gekkonine geckos (Heineke et al 2011;Gamble et al 2012;Sistrom et al 2014) and delimiting species boundaries (Horner 2005;Sistrom et al 2009Sistrom et al , 2013Oliver et al 2010Oliver et al , 2016Doughty et al 2012Doughty et al , 2018Hutchinson et al 2014).…”

“…Recently, progress has been made resolving the affinities of Gehyra to other gekkonine geckos (Heineke et al 2011;Gamble et al 2012;Sistrom et al 2014) and delimiting species boundaries (Horner 2005;Sistrom et al 2009Sistrom et al , 2013Oliver et al 2010Oliver et al , 2016Doughty et al 2012Doughty et al , 2018Hutchinson et al 2014). As pointed out 35 years ago, taxonomic progress on Gehyra has been particularly hindered by the loss of colour patterns in preservative and that 'too few specimens from too few localities have been examined ' (p. 739).…”

“…One of the most recalcitrant groups within Gehyra is the G. punctata (Fry, 1914) species complex from the Pilbara, Gascoyne and eastern Murchison regions of Western Australia (WA), and sometimes reported from the southern Kimberley (Storr et al 1990;Wilson & Swan 2008; but see King 1981;Doughty et al 2018). In his assessment in the 1910s of collections from the Western Australian Museum (WAM), Fry originally described this taxon as a 'variety' of G. variegata based on a small female from the 'Strelley River, Pilbara' that corresponded with Central Ranges specimens from the Horn Expedition (see Ellis et al 2018) stating that: 'In all structural characters it agrees with the variable P.…”