Tooth microwear pattern variation in karst and non-karst peninsular Southeast Asian murine rodents

The dietary preferences of most rodents, especially in tropical countries, are poorly known. In the tropics, rodent diversity can be high and several species can coexist in the same habitats. In order to better document the dietary habits of Southeast Asian murid and diatomyid rodents, we examined microwear patterns in 21 species, with a particular focus on those living in karst habitats. Five variables of microwear scars (scratches and pits) were counted and measured on the dental facet of the first molar hypocone. We observed large variation and overlap in microwear patterns between and within genera, suggesting that feeding ecology is diverse (mostly generalist omnivorous species) within species and genus. For species living in agro-ecosystems, few differences were observed when we compared sympatric species within a genus, suggesting that niche partitioning is not achieved by feeding, neither in terms of diet composition nor in the way food is processed, or that food items are more homogeneous in terms of physical properties that affect microwear patterns. Differences between sympatric species were more pronounced in forest or karst contexts, suggesting that specialisation and niche differentiation have persisted in more preserved environments. Finally, differences were also observed in urban ecosystems suggesting that the communities of rodents evolved niche partitioning in these human-modified habitats. Our results also revealed differences in microwear patterns between karst and non-karst rodents, with all karst species showing a trend towards increasing numbers of small scratches and small pits. This suggested that the karst environment may influence the dietary habits of rodents, either in terms of the composition of the diet or by altering the general characteristics of the food.