The Neotropical tree Ilex paraguariensis A. St. Hil. (Aquifoliaceae): pollen and seed dispersal in a fragmented landscape

Abstract

Ilex paraguariensis is a dioecious, Neotropical tree endemic to South America with wide cultural, economic and ecological signi cance. However, due to extensive fragmentation and deforestation throughout its natural area of occurrence, studies on gene ow and genetic diversity are needed to drive genetic conservation and improvement strategies. Based on the sampling of all adult and juvenile trees in two I. paraguariensis populations, we investigate the reali ed pollen and seed ow and dispersal distance, spatial genetic structure (SGS) and genetic diversity using microsatellite markers. We found limited genetic di erentiation between populations (G’ st = 0.033), but signi cant di erences in terms of genetic diversity (R: 4.7 vs 3.9, H 0 : 0.495 vs 0.371, H e : 0.445 vs 0.375), pollen (10 vs. 23.3%) and seed immigration (0 vs. 3.3%), mating among relatives (t r : 16 vs 30%) and biparental inbreeding (F r : 0.253 vs. 0.345). Within populations, the genetic diversity was similar between adults and juveniles, but adults presented signi cantly lower xation index than juveniles, suggesting selection against inbred individuals between juvenile and adult life stages. We also found similar mean pollen (255 vs. 293 m) and seed (385 vs. 323 m) dispersal distances within populations. Our results show that the studied populations are not genetically isolated and some mating occurs among related trees due to SGS; however, the frequency of biparental inbred individuals decrease over the life course due to inbreeding depression. These results contribute directly to species management and seed collection and inform in situ and ex situ conservation programs.

Keywords

• conservation genetics, gene ow, mixed ombrophilous forest, microsatellite markers, population genetics