Morphological variation in skull shape and size across extinct and extant populations of the greater stick-nest rat (

Abstract

Within-species morphological variation is often observed across spatial and climatic gradients. Understanding this variation is important to conservation planning, as specialised adaptations may influence a population’s persistence following translocation. However, knowing whether local adaptations are prevalent within a species can be challenging when the species has undergone range contractions. Here, we used museum specimens to study size and shape variation of the greater stick-nest rat (Leporillus conditor). We aimed to determine whether intraspecific size and shape variation previously existed within the species across its historical range, and inform on possible implications for translocations of the remaining extant population. We found significantly larger skull size in the Franklin Islands and arid populations, possibly indicating a historically continuous population experiencing similar selection pressures such as high predation pressure, competition with other large arid zone rodents or climatic extremes. Conversely, skull shape variation within the species adheres to an allometric trajectory, indicating no specific local adaptations of skull shape. This absence of local skull shape adaptation suggests that the Franklin Islands population is likely suitable for mainland translocations. However, further research into the historical phylogeography of the species is recommended to identify whether large size resulted from shared ancestry or convergent evolution.

Hiding in plain sight: two new species of diminutive marsupial (Dasyuridae: Planigale) from the Pilbara, Australia

“…In morphological datasets, a high proportion of the variance explained by PC1 is usually due to size (Jolicoeur 1963;Berner 2011) and accounting for the effect of size has been shown to help distinguish between morphologically cryptic dasyurid species as it allows for a comparison on skull shape (viacava et al 2023). to account for size effects (specifically caused by isometric scaling) between species, we used log-shape ratios by calculating the geometric mean of all variables, per individual, as a proxy for skull size, dividing each variable by the geometric mean then log-transforming this ratio (Mosimann 1970;onley et al 2022;Pavónvázquez et al 2022;viacava et al 2023). we then re-ran the PCA on the 'size-corrected' dataset.…”