Interações bióticas são mais importantes que o clima na parapatria do gênero Callithrix Erxleben, 1777

Abstract

The species range responds to numerous historical and ecological factors, being one of the most essential questions in Biogeography. The genus Callithrix Erxleben 1777 comprises six species of small primates that inhabit the central and eastern regions of Brazil, exhibiting a parapatric pattern of distribution and without natural sympatric zones. Among these species, Callithrix penicillata has the largest area of occurrence, mostly inhabiting the Cerrado biome, parts of the Caatinga, and transition zones with the Atlantic Forest. This species is replaced by Callithrix aurita to the south, a species that is restricted to the Atlantic Forest of the states of Minas Gerais, Rio de Janeiro, and São Paulo. The factors that define spatial separation and substitution between species, however, are not yet elucidated. Thus, the present study aimed to understand the distribution patterns of these species, focusing on the contact zones between taxa. For this, we used species distribution models calibrated with data of climate, landscape, and vegetation and analyzed the characteristics of the parapatric and potential sympatric regions. To test for competitive exclusion, we verified the prevalence of one or another species in potential sympatric areas by counting the occurrence records of each primate overlapping these areas. The climatic variables had a greater relative importance for the distribution models and seem to reflect the climate of the occurrence area of each species, with C. aurita inhabiting colder and humid areas, and C. penicillata in warmer and drier areas, which is probably linked to the biome naturally occupied by each primate. The predominance of C. aurita in the potential sympatric area suggests a process of competitive exclusion that limits C. penicillata to the south of its natural distribution. Thus, we concluded that each species has a limiting factor of its distribution in the contact zone. Climate probably associated with vegetation limits C. aurita, and the presence of a competing species limits C. penicillata. This interaction is of paramount importance for the conservation planning of C. aurita and, consequently, to prevent the expansion of C. penicillata outside its natural areas. The models were not able, however, to predict the invasive potential of C. penicillata, given that regions invaded by this species were not considered adequate, which corroborates the hypothesis that the occupation of this species also depends on non-climatic factors.