Parapatry of Phanaeus splendidulus and P. dejeani (Coleoptera: Scarabaeidae: Scarabaeinae) in two mountain ranges in the Atlantic Forest.

Parapatry occurs when species exhibit adjacent distributions in space, with contact in their boundaries, with or without overlapping. Many factors can generate this pattern, such as environmental conditions and interspecific competition. Mountains are excellent systems to study parapatry because they exhibit large environmental heterogeneity within a small geographical area. Phanaeus splendidulus and P. dejeani are two similar dung beetle species with apparent sympatric distributions at geographical scale, but with a hypothesized parapatric distribution in mountains. We assessed whether P. splendidulus and P. dejeani indeed exhibit a parapatric distribution in two mountain ranges in the Atlantic Forest. We also tested the effects of environmental conditions and interspecific competition on the observed pattern of abundance for both species for one mountain. We placed pitfall traps at every 50 m of elevation from 600 to 2400 m a.s.l. at Itatiaia National Park and from 100 to 2050 m a.s.l. at Serra dos Órgãos National Park in Brazil. We used temperature, vegetation cover, litter volume and soil granulometry as environmental predictors of each species abundance and the abundance of its congeneric species as a measure of interspecific competition. Phanaeus splendidulus and P. dejeani indeed exhibited a parapatric distribution and a small overlapping area, with P. splendidulus reaching up to 1450 m a.s.l. in Itatiaia National Park and 1250 m a.s.l. in Serra dos Órgãos National Park, and P. dejeani occurring above to 1000 m a.s.l. Only maximum temperature was significantly related to species abundance. Maximum temperature affected positively P. splendidulus abundance and negatively P. dejeani, suggesting that these species have opposite climate preferences. The abundance of the congeneric species was not significant for either species. Understand species distributions and what drives them is critical to understand the evolution of species interaction, their responses to the environment and for conservation, in a world of climate change. [ABSTRACT FROM AUTHOR]