A relict species restricted to a quartzitic mountain in tropical America: an example of microrefugium?

Abstract

We examined the distribution of Coccoloba cereifera,a tropical endemic species that occurs in a small area in the Espinhaco mountain range, southeastern Brazil. It is hypothesized that its narrow distribution is strongly related to the spatially scattered distribution of sandfields. However, this soil type extends far beyond the small region where C. cereifera is currently found, indicating that other factors might be involved in the distribution of this species. Coccoloba cereifera also displays all traits of a relict population in a microrefugium. As a result, we were encouraged to explore other factors potentially related to the distribution of the species. In an attempt to aid in the understanding of the processes and mechanisms that lead C. cereiferato present the narrow actual distribution, we applied two distribution modelling approaches to investigate the potential distribution of the species beyond the small known distribution area. The distribution seems to be strongly associated with sandy patches/grasslands formed among rocky outcrops and is limited by some topoclimatic and/or topographic features. Some of them related to the existence of a microrefugium, a fact also suggested by the pattern of distribution of the species in the past. From the management point of view, the existence of a microrefugium in this area calls for changes in conservation efforts and priorities.