Disjunct plant species in South American seasonally dry tropical forests responded differently to past climatic fluctuations

Abstract

Seasonally dry tropical forests (STDFs) are a main component of open seasonally dry areas in South America and their biogeography is understudied compared to evergreen forests. In this work, we identify vascular plant species with long-distance disjunctions across STDF patches of South America based on information available in online repositories and on species taxonomy and distribution, to explore species’ biogeographic patterns. Specifically, we combine distribution data from the Brazilian Flora 2020 Project (BFG) and the Global Biodiversity Information Facility (GBIF) to identify species with a peri-Amazonian distribution, and then use species distribution models to discuss possible scenarios of peri-Amazonian distributions under Pleistocene climatic fluctuations. We identified 81 candidate species for peri-Amazonian distributions in STDFs, including shrubs, herbs, trees and lianas, and provided a summary of their main fruit dispersion syndrome based on the literature to identify prevalent dispersal patterns. The study species responded differently to Pleistocene climatic fluctuations, with both contractions and expansions through time in different rates and do not show consistent larger distributions during past climate conditions. Our results show that a peri-Amazonian distribution is also present in growth-forms other than trees. Also, the prevalence of species with long-distance dispersal strategies such as wind or vertebrate-dispersed can suggest, although biased for Neotropical taxa, an alternative scenario of long-distance dispersal, possibly using stepping-stones of azonal vegetation. We argue that such an alternative scenario, especially for species disjunct with long-dispersal abilities, should be considered to test if STDF disjunctions are relics of a past widespread distribution or not.