A new species of frog in the Litoria ewingii species group (Anura: Pelodryadidae) from south-eastern Australia

Abstract

Population declines and range contractions among Australian frogs that commenced in the early 1980s continue in some species that were once widespread. The generality of this pattern has been difficult to discern, especially for those species that are encountered rarely because they have restricted periods of calling activity with poorly defined habitat preferences, and are not common. Several lines of evidence indicate that Litoria littlejohni is such a species. This frog was once known from mid-eastern New South Wales to eastern Victoria, and evidence from wildlife atlas databases and targeted searches indicate that it has declined in large portions of its former range, leaving several populations that are isolated, in some cases restricted in distribution, and of small size. We investigated the relationships among populations using mitochondrial ND4 nucleotide sequences and single nucleotide polymorphisms (SNPs) from the nuclear genome. We found that northern and southern populations form two highly divergent genetic groups whose distributions abut at the southern margin of the Sydney Basin Bioregion and these genetic groups also show divergence in morphology and male advertisement calls. Here we describe the populations to the south of the Sydney Basin Bioregion as a new species and provide information on its distribution and ecology. In light of the apparent isolation and small size of known populations of the new species and the consequent restriction of the range of L. littlejohni, we assessed the conservation status of both species.

Two new frog species from the Litoria rubella species group from eastern Australia

“…DArTseq™ represents a combination of DArT genome complexity reduction methods and next generation sequencing platforms (Kilian et al 2012). DNA samples were processed in restriction enzyme digestion/ligation reactions using a combination of the PstI/SphI restriction enzymes and ligated fragments were PCR amplified as described by Kilian et al (2012) and Mahony et al (2020) for single end sequencing for 77 cycles on an Illumina Hiseq2500.…”

Genome-wide SNPs reveals inbreeding, small populations, and strong genetic isolation in a threatened frog (Litoria littlejohni)

“…This moderate sized (adult body length 42 mm) brown tree frog occurs in the temperate climatic region of south-east Australia. Recently, L. littlejohni was rede ned and taxonomically split into two species, and subsequently its conservation status was assessed as Endangered (EN) (International Union for the Conservation of Nature Red List criteria, IUCN 2019) by Mahony et al (2020). What is now considered L. littlejohni is found in three isolated regions in the state of New South Wales (NSW) (Mahony et al 2020).…”

“…Recently, L. littlejohni was rede ned and taxonomically split into two species, and subsequently its conservation status was assessed as Endangered (EN) (International Union for the Conservation of Nature Red List criteria, IUCN 2019) by Mahony et al (2020). What is now considered L. littlejohni is found in three isolated regions in the state of New South Wales (NSW) (Mahony et al 2020). The geographic range is restricted to the Sydney Basin bioregion (Thackway & Cresswell 1995) with apparently isolated populations on the Woronora Plateau in the southeast, to the Blue Mountains in the west, and to the Central Coast Range (Watagan Mountains) in the northeast (Fig.…”

“…This poor understanding of habitat preferences and calling behaviours is thought to have led to mis-matched survey efforts and false absences in historical surveys conducted across the range (Gill et al 2021). Populations of L. littlejohni also do not appear to be large and densities at breeding ponds are relatively low compared to other Australian tree frogs, resulting in low capture rates at occupied sites (Mahony et al 2020;Klop-Toker et al 2021;Gillespie et al 2015). Whether this low density is due to inherent low population density or due to declines is unknown (Lemckert 2004;Mahony et al 2020).…”

“…Populations of L. littlejohni also do not appear to be large and densities at breeding ponds are relatively low compared to other Australian tree frogs, resulting in low capture rates at occupied sites (Mahony et al 2020;Klop-Toker et al 2021;Gillespie et al 2015). Whether this low density is due to inherent low population density or due to declines is unknown (Lemckert 2004;Mahony et al 2020). Litoria littlejohni is susceptible to chytrid with prevalence levels approximately 30% across all L. littlejohni populations (Klop-Toker et al 2021), but there is no pre-chytrid population data for this species.…”