Patterns of genetic diversity, spatial genetic structure and gene flow in Campomanesia xanthocarpa: insights from SSR markers of different genomic origins.

Vanessa S Petry,Gustavo H.F Klabunde,Lilian O Machado,Newton C.F Da Costa,Rubens O Nodari,Valdir M Stefenon

doi:10.1590/0001-3765202120210134

Abstract

Campomanesia xanthocarpa (Mart.) O. Berg is a South American fruit tree species with important ecological and medicinal properties, which remnants are currently found mainly in isolated forest fragments. In this study, SSR markers from three different genomic origins (gene-linked, nuclear neutral, and organellar) were used to evaluate the patterns of genetic diversity, fine-scale spatial genetic structure and historical gene flow in fragmented forest formations of C. xanthocarpa from the Atlantic Forest in southern Brazil. Our results show that the forest fragments present moderate to high levels of genetic diversity in comparison to species presenting similar life traits, although a trend opposite to expected was observed concerning gene-linked and neutral SSR markers. The fine-scale spatial genetic structure revealed different patterns in short and large distance classes, with a distinct influence of gene-linked and neutral markers in driving the genetic structure in each distance class. The presence of an isolation-by-adaptation pattern implies the need for maintenance of the current remnants to assure the conservation of the private alleles. Finally, as the genetic diversity is found predominantly within forest fragments, programs of seed collection and/or genetic rescue should prioritize a larger number of individuals within each fragment, to increase the sampled diversity.

Highlights

More than a third of the world’s forest cover was lost as a result of deforestation, which was widespread in temperate regions in the mid18th to 20th centuries and increased in the tropics over the past half-century (Haddad et al 2015)
Higher estimates were observed for the genelinked markers, in comparison to neutral nuclear markers for A, Ae (p < 0.05 in fragment CF and p > 0.05 for all other fragments) and He (p < 0.05 in fragments CF and IOM and p > 0.05 for all other fragments), but not for the fixation indexes FIS and FIT
Gene-linked markers are directly connected to genes and are expected to be more conserved, while neutral markers are usually hotspots of diversity

Summary

Introduction

More than a third of the world’s forest cover was lost as a result of deforestation, which was widespread in temperate regions in the mid18th to 20th centuries and increased in the tropics over the past half-century (Haddad et al 2015). Remnant forests are likely to suffer from being smaller, more isolated, and with a greater area located near the edge of the forest (Haddad et al 2015). In addition to the edge effect, fragmentation triggers the spatial distribution of plants to change and may affect the abundance and foraging behavior of pollinators (Breed et al 2015). Such processes, in turn, may have negative ecological and genetic consequences in tree populations. Habitat fragmentation and pollinators’ decline are expected to impact the capacity of plant populations to reproduce successfully, generating concerns for their demography, evolution, and long-term persistence. Understanding the biology of plant reproduction is of central importance for dealing with these environmental challenges and for maintaining

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