Morphological evolution and niche conservatism across a continental radiation of Australian blindsnakes.

Understanding how continental radiations are assembled across space and time is a major question in macroevolutionary biology. Here, we use a phylogenomic-scale phylogeny, a comprehensive morphological dataset, and environmental niche models to evaluate the relationship between trait and environment and assess the role of geography and niche conservatism in the continental radiation of Australian blindsnakes. The Australo-Papuan blindsnake genus, Anilios, comprises 47 described species of which 46 are endemic to and distributed across various biomes on continental Australia. Although we expected blindsnakes to be morphologically conserved, we found considerable interspecific variation in all morphological traits we measured. Absolute body length is negatively correlated with mean annual temperature, and body shape ratios are negatively correlated with soil compactness. We found that morphologically similar species are likely not a result of ecological convergence. Age-overlap correlation tests revealed niche similarity decreased with the relative age of speciation events. We also found low geographical overlap across the phylogeny, suggesting that speciation is largely allopatric with low rates of secondary range overlap. Our study offers insights into the eco-morphological evolution of blindsnakes and the potential for phylogenetic niche conservatism to influence continental scale radiations.