Elevational partitioning in species distribution, abundance and body size of Australian alpine grasshoppers (Kosciuscola)

Changes in the physical environment with elevation can influence species distributions and their morphological traits. In mountainous regions, steep temperature gradients can result in patterns of ecological partitioning among species that potentially increases their vulnerability to climate change. We collected data on species distributions, relative abundance and body size for three grasshopper species of the genus Kosciuscola (K. usitatus, K. tristis and K. cognatus) at three locations within the mountainous Kosciuszko National Park in Australia (Thredbo, Guthega and Jagungal). All three species showed differences in their distributions according to elevation, with K. usitatus ranging from 1400 to 2000 m asl, K. tristis from 1600 to 2000 m asl and K. cognatus from 1550 to 1900 m asl. Decreasing relative abundance with increasing elevation was found for K. usitatus, but the opposite pattern was found for K. tristis. The relative abundance of K. cognatus did not change with elevation but was negatively correlated with foliage cover. Body size decreased with elevation in both male and female K. usitatus, which was similarly observed in female K. tristis and male K. cognatus. Our results demonstrate spatial partitioning of species distributions and clines in body size in relation to elevational gradients. Species-specific sensitivities to climatic gradients may help to predict the persistence of this grasshopper assemblage under climate change.