Lineage diversity within a widespread endemic Australian skink to better inform conservation in response to regional‐scale disturbance

Abstract

Much attention is paid in conservation planning to the concept of a species, to ensure comparability across studies and regions when classifying taxa against criteria of endangerment and setting priorities for action. However, various jurisdictions now allow taxonomic ranks below the level of species and nontaxonomic intraspecific divisions to be factored into conservation planning—subspecies, key populations, evolutionarily significant units, or designatable units. Understanding patterns of genetic diversity and its distribution across the landscape is a key component in the identification of species boundaries and determination of substantial geographic structure within species. A total of 12,532 reliable polymorphic SNP loci were generated from 63 populations (286 individuals) covering the distribution of the Australian eastern three‐lined skink, Bassiana duperreyi, to assess genetic population structure in the form of diagnosable lineages and their distribution across the landscape, with particular reference to the recent catastrophic bushfires of eastern Australia. Five well‐supported diagnosable operational taxonomic units (OTUs) existed within B. duperreyi. Low levels of divergence of B. duperreyi between mainland Australia and Tasmania (no fixed allelic differences) support the notion of episodic exchange of alleles across Bass Strait (ca 60 m, 25 Kya) during periods of low sea level during the Upper Pleistocene rather than the much longer period of isolation (1.7 My) indicated by earlier studies using mitochondrial sequence variation. Our study provides foundational work for the detailed taxonomic re‐evaluation of this species complex and the need for biodiversity assessment to include an examination of cryptic species and/or cryptic diversity below the level of species. Such information on lineage diversity within species and its distribution in the context of disturbance at a regional scale can be factored into conservation planning regardless of whether a decision is made to formally diagnose new species taxonomically and nomenclaturally.

Determining the generation length and level of morphological and genetic differentiation in the Data Deficient glossy grass skink (Pseudemoia rawlinsoni)

“…Although some degree of morphological variation was evident within the glossy grass skink, there were no consistent morphological differences among the seven genetic lineages in the species. Interestingly, the location of the seven genetic lineages within the glossy grass skink were largely concordant with the recognised biogeographic boundaries in southeastern Australia (Chapple et al 2005(Chapple et al , 2011a(Chapple et al , 2011bBryant and Krosch 2016;Dissanayake et al 2022). Assuming 2% sequence divergence per million years, as used in other Australian skinks (Chapple et al 2005;Haines et al 2014), this would indicate a divergence time of between 0.5 million years ago and 2.6 million years, ago during the Pliocene-Pleistocene boundary (Chapple et al 2005;Dissanayake et al 2022;Senior et al 2022).…”

“…Interestingly, the location of the seven genetic lineages within the glossy grass skink were largely concordant with the recognised biogeographic boundaries in southeastern Australia (Chapple et al 2005(Chapple et al , 2011a(Chapple et al , 2011bBryant and Krosch 2016;Dissanayake et al 2022). Assuming 2% sequence divergence per million years, as used in other Australian skinks (Chapple et al 2005;Haines et al 2014), this would indicate a divergence time of between 0.5 million years ago and 2.6 million years, ago during the Pliocene-Pleistocene boundary (Chapple et al 2005;Dissanayake et al 2022;Senior et al 2022). This period was characterised by climatic fluctuations, and associated fluctuations in sea level (Byrne et al 2011;Chapple et al 2011a;Haines et al 2014).…”

Systematic assessment of the brown tree frog (Anura: Pelodryadidae: Litoria ewingii) reveals two endemic species in South Australia

“…The level of genetic divergence observed between Litoria sibilus and its mainland counterparts suggests a vicariance event that pre-dates the last terrestrial interconnections between Kangaroo Island and mainland Australia, which are estimated to have occurred at least twice in the past 500 Kya (Dissanayake et al 2022;Dubey & Shine 2010;Symula et al 2008). Similar diversification patterns have been observed for other Kangaroo Island vertebrates, including the frog, Crinia signifera (Symula et al 2008), and skink, Acritoscincus duperreyi (Dissanayake et al 2022;Dubey & Shine 2010), with divergence estimates for populations of both taxa predicted to have occurred in the Plio-Pleistocene, far pre-dating the most recent land bridges. This suggests the presence of an additional barrier to dispersal that prevented some organisms from traversing the Backstairs Passage land bridge during more recent periods of lowered sea-level.…”

“…This is due largely to their morphological and acoustically conserved nature, as highlighted by the recent description of the morphologically cryptic Litoria watsoni (Mahony et al 2020). The identification and classification of cryptic diversity is of high research priority given it has significant implications for effective conservation, both in providing a metric for biodiversity and allowing for scientific and legal recognition of taxonomic units for conservation management (Coates et al 2018, Dissanayake et al 2022.…”

Strong Population Genetic Structure for the Endangered Micro-Trapdoor Spider Moggridgea rainbowi (Mygalomorphae, Migidae) in Unburnt Habitat after Catastrophic Bushfires

“…We also consider the additional Moritz criterion [23], which proposes that ESUs should show reciprocal monophyly in phylogenetic analyses of mitochondrial DNA sequence data. Whilst species remain the standard unit used in conservation assessments, the use of other measures of biodiversity, such as phylogenetic diversity [24] or ESUs [23], may provide alternative approaches that escape the limitations of a reliance on taxonomic species delineation [25]. By doing so, they may provide important information for protecting biodiversity and enhancing genetic diversity at or below the species level, to inform subsequent conservation planning [26][27][28][29].…”