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

Alexander Zizka,José Rubens Pirani,Matheus Colli-Silva

doi:10.21425/f5fbg49882

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.

Highlights

Tropical South America is a global biodiversity center for vascular plants (Ulloa-Ulloa et al 2017, Antonelli et al 2018)
We provide a new list of flowering plant species disjunct in South American seasonally dry tropical forests, considering different types of lifeforms and dispersal syndromes
When searching for taxa occurring in dry deciduous formations according to the BFG, we found 2,302 species of vascular plants

Summary

Introduction

Tropical South America is a global biodiversity center for vascular plants (Ulloa-Ulloa et al 2017, Antonelli et al 2018). If explicitly considered for continental-scale analyses, the open seasonally dry formations are mostly treated as the background in which vicariant events occurred in groups associated to moist forests, rather than entities of their own right (Werneck 2011, Pennington et al 2018) This is problematic, due to the high species richness and endemism observed in these areas (Rizzini 1997, Pennington et al 2006, Ribeiro and Walter 2008, Zizka 2019) and the importance of evolutionary connectivity among biomes for the evolution of South American diversity (see Simon et al 2009, Antonelli et al 2018, Zizka et al 2020)

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