Resolving distribution and population fragmentation in two leaf-tailed gecko species of north-east Australia: key steps in the conservation of microendemic species

Abstract

North Queensland harbours many microendemic species. These species are of conservation concern due to their small and fragmented populations, coupled with threats such as fire and climate change. We aimed to resolve the distribution and population genetic structure in two localised Phyllurus leaf-tailed geckos: P. gulbaru and P. amnicola. We conducted field surveys to better resolve distributions, used Species Distribution Models (SDMs) to assess the potential distribution, and then used the SDMs to target further surveys. We also sequenced all populations for a mitochondrial gene to assess population genetic structure. Our surveys found additional small, isolated populations of both species, including significant range extensions. SDMs revealed the climatic and non-climatic variables that best predict the distribution of these species. Targeted surveys based on the SDMs found P. gulbaru at an additional two sites but failed to find either species at other sites, suggesting that we have broadly resolved their distributions. Genetic analysis revealed population genetic structuring in both species, including deeply divergent mitochondrial lineages. Current and potential threats are overlain on these results to determine conservation listings and identify management actions. More broadly, this study highlights how targeted surveys, SDMs, and genetic data can rapidly increase our knowledge of microendemic species, and direct management.

A new species of Phyllurus leaf-tailed gecko (Lacertilia: Carphodactylidae) from Scawfell Island, mid-east Queensland, Australia

“…Rocky, rainforest gullies on nearby St Bees and Keswick Islands require surveying. None of these islands appear to have sufficient deeply-piled rocky habitat to support populations of Phyllurus but the ability of species to survive in very small areas (e.g., P. gulbaru and P. pinnacelensis; Bertola et al 2018, Hoskin et al 2019 suggests surveys are warranted. Additional surveys are required across the gullies of Scawfell Island to map out the distribution of P. fimbriatus sp.…”

“…Scawfell Island is completely protected within South Cumberland National Park; however, all these potential threats could still operate. Fire deserves particular attention because an increase in heatwaves and/or droughts with climate change could result in a change in fire frequency or intensity on Scawfell Island, which could reduce the area and connectivity of rainforest patches (Bertola et al 2018;Hoskin et al 2019). Fire and other potential threats need to be assessed and managed accordingly.…”

“…1). These discoveries have not only increased knowledge on the distribution and biogeographic history of the genus, but have highlighted threats to biota of the isolated remnants of 'dry rainforest' along the Queensland coast (e.g., Hoskin et al, 2003Hoskin et al, , 2019Bertola et al 2018).…”

A demographic framework for understanding fire‐driven reptile declines in the ‘land of the lizards'

“…Second, these regions also have the highest total numbers of squamate species of conservation concern, which have also been declining due to other threatening processes, such as habitat loss and impacts of invasive species (Tingley et al, 2019). Squamates with small distributions and population sizes are more vulnerable to impacts of stochastic events, including large fires (Bertola et al, 2018). For example, the Arnhem phasmid gecko ( Strophurus horneri ) and the Oenpelli rock python ( Simalia oenpelliensis ) are restricted to the northern tropics of Australia (Chapple et al, 2019), where hot, late dry season fires are becoming more frequent (Andersen, 2021).…”

“…Squamates with small distributions and population sizes are more vulnerable to impacts of stochastic events, including large fires (Bertola et al, 2018). For example, the Arnhem phasmid gecko (Strophurus horneri) and the Oenpelli rock python (Simalia oenpelliensis) are restricted to the northern tropics of Australia (Chapple et al, 2019), where hot, late dry season fires are becoming more frequent (Andersen, 2021).…”