Predicted distributions could suggest regional sympatry in spite of local allopatry: The case of the dung beetle Canthon rutilans Castelnau, 1840 (Coleoptera: Scarabaeidae)

Studying the environmental characteristics of the localities in which different taxa have been observed could help to estimate probable niche differences. Previous studies on local distribution and reproductive behavior of the two subspecies of Canthon rutilans support their allopatry. Here we estimated the geographical distribution of these taxa to examine the congruency between the environmental characteristics of the occurrence localities derived from geographical and local data, in order to facilitate the future study of the causal factors that are more likely to explain their segregation. To do so, a database including most of the available distributional information about these subspecies was compiled. The data derived from 23 environmental variables in the occurrence cells were used to estimate those variables with different mean values among the two subspecies, and also to generate distributional maps reflecting the probable distribution of the two subspecies. Ten variables have statistically significant different values among both subspecies. Canthon rutilans rutilans would be present in colder places, living in the high elevation localities of the Atlantic Forest or Pampas biomes, whereas C. rutilans cyanescens seems to be restricted to lowland forested areas. Probable distribution maps show geographical sympatry in almost half of the distribution range of C. r. rutilans. As former results suggest that they are in allopatry at a local scale, these results propose that fine-grain environmental factors would be promoting the segregation of taxa, but also that coarse-grain data should be used with caution when the aim is to estimate niche differences.