The application of population genetic metrics to evaluate the health of a population after undergoing anthropogenic management and experiencing environmental stochasticity remains underexplored in amphibians. Several metrics can be used to measure loss of genetic diversity and decreased gene flow to determine population health, including heterozygosity, inbreeding, and structure. This study assessed the genetic health of the endangered frog, Litoria littlejohni using genetic metrics in a population exposed to human modifications (dam creation) and extreme climatic events (droughts followed by heavy rainfall). We found strong population structuring, with two distinct subpopulations, one in the northern and another in the southern area of occupancy. Despite being only 2.5 kilometres apart, there was limited gene flow between the sub-populations. Genetic differentiation between these sub-populations, determined by PCA analysis, decreased after high rainfall in 2021. However, strong genetic structuring returned in 2023 during drought conditions. In the northern sub-population, where breeding habitats included both constructed ponds and natural creek pools, heterozygosity was significantly higher and mean kinship significantly lower compared to the southern sub-population where there are fewer natural creek lines nearby. Furthermore, in the southern sub-population, inbreeding metrics increased significantly from 0.003 in 2020 to 0.162 in 2023. As the southern sub-population predominantly relies on constructed ponds for breeding, the absence of natural creek pools may be limiting dispersal and affecting the genetic health of this sub-population. To improve heterozygosity and connectivity, additional ponds could be constructed between the two sub-populations, acting as stepping-stones to enhance gene flow and reduce inbreeding.

Amphibians are among the most threatened vertebrate taxa globally. Their global decline necessitates effective conservation actions to bolster populations across both the larval and adult life stages. Constructing man-made ponds is one such action proven to enhance reproduction in pond-breeding amphibians. However, to achieve successful conservation outcomes, extensive prior knowledge about the ecology and behaviour of the target species is required. In this study, we investigated how different hydroperiod regimes impact the growth and development of Litoria littlejohni tadpoles. Over a 28-week period, tadpoles were exposed to three hydroperiod treatments: Constant High, Declining, and Constant Low water levels. Weekly measurements of snout-to-vent length, body mass, and Gosner stage were taken to assess any treatment-related changes. To determine whether different treatments affected locomotor performance, a jump test was conducted three weeks post metamorphosis. Individuals did not exhibit developmental plasticity in response to declining water, with a mean time to metamorphosis of 93.3 days. Comparatively, when L. littlejohni tadpoles were exposed to low water volumes, they were able to speed up development and reduce time to metamorphosis, with a mean time of 56.5 days. The speeding up of development had an apparent consequence for L. littlejohni. We found support for trade-offs between rapid development and reduced morphometric measurements post-metamorphosis which resulted in reduced locomotive ability. Individuals from Constant Low water treatments exhibited an average total jumping distance of 170.5 cm over 10 consecutive jumps, compared to 235.8 cm in Constant High and 209.5 cm in Declining treatments. Rapid larval development aids tadpoles in escaping suboptimal aquatic conditions, but its effects on locomotion may impact foraging efficiency and predator escape ability. Understanding developmental plasticity in threatened amphibians, especially in response to hydroperiod variations, is crucial for conservation programs, particularly under future climate change scenarios predicting increased drought and reduced hydroperiods in aquatic environments.