Pollen flow in fragmented landscapes maintains genetic diversity following stand-replacing disturbance in a neotropical pioneer tree, Vochysia ferruginea Mart

Abstract

In forests with gap disturbance regimes, pioneer tree regeneration is typically abundant following stand-replacing disturbances, whether natural or anthropogenic. Differences in pioneer tree density linked to disturbance regime can influence pollinator behaviour and impact on mating patterns and genetic diversity of pioneer populations. Such mating pattern shifts can manifest as higher selfing rates and lower pollen diversity in old growth forest populations. In secondary forest, where more closely related pollen donors occur, an increase in biparental inbreeding is a potential problem. Here, we investigate the consequences of secondary forest colonisation on the mating patterns and genetic diversity of open-pollinated progeny arrays for the long-lived, self-compatible pioneer tree, Vochysia ferruginea, at two Costa Rican sites. Five microsatellite loci were screened across adult and seed cohorts from old growth forest with lower density, secondary forest with higher density, and isolated individual trees in pasture. Progeny from both old growth and secondary forest contexts were predominantly outcrossed (tm=1.00) and experienced low levels of biparental inbreeding (tm-ts=0.00-0.04). In contrast to predictions, our results indicated that the mating patterns of V. ferruginea are relatively robust to density differences between old growth and secondary forest stands. In addition, we observed that pollen-mediated gene flow possibly maintained the genetic diversity of open-pollinated progeny arrays in stands of secondary forest adults. As part of a natural resource management strategy, we suggest that primary forest remnants should be prioritised for conservation to promote restoration of genetic diversity during forest regeneration.

The resilience of forest fragmentation genetics—no longer a paradox—we were just looking in the wrong place

“…Under these conditions, pollinator behavior is expected to be impacted by the great variation in tree density between old growth (low density) and secondary forest (high density). These assumptions are tested for the long-lived, self-compatible pioneer tree, Vochysia ferruginea, at old growth and secondary forest sites in Costa Rica (Davies et al, 2015). Progeny from both old growth and secondary forest contexts were predominantly outcrossed and experienced low levels of biparental inbreeding, indicating that the mating patterns of V. ferruginea are relatively robust to density differences between old growth and secondary forest stands.…”

“…The second study asks whether some forest contexts are more sensitive than others to population genetic impacts (Davies et al, 2015). During the colonization of open landscapes, seed-source bottlenecks can cause a severe reduction in genetic diversity and is particularly an issue for secondary forest colonizing trees (Davies et al, 2010).…”

“…In this latest focal issue of Heredity we introduce five important studies of neotropical trees and eucalypts (Breed et al, 2015a,b;Davies et al, 2015;Rymer et al, 2015;Vinson et al, 2015) that further advance our understanding of forest fragmentation genetics, and are described below. Overall, from these and other recent studies, our understanding of forest fragmentation genetics has developed in three key areas.…”

Benefits of gene flow are mediated by individual variability in self‐compatibility in small isolated populations of an endemic plant species

“…For example, Schleuning, Niggemann, Becker, and Matthies () concluded that the longevity of Trifolium montanum has likely delayed extirpation of some populations. A lag in fitness declines in perennial species may be particularly long if there is strong selection against selfed progeny (Davies et al., ; Delmas et al., ; Young, Boyle, & Brown, ). Strong selection against inbred progeny in T. virginicum is suspected as census size estimates for some populations in 1984 were exactly the same in 2013; however, we cannot eliminate other factors such as poor pollinator visitation rates or habitat degradation.…”

Isolation and characterization of microsatellite loci in Quercus fabri (Fagaceae)

“…Due to its ability to grow in barren soils, high capacity to sprout, and tolerance to disturbance, Q. fabri is not only a pioneer species for secondary succession of evergreen broadleaved forests (EBLFs) but also plays an important role in the recovery of EBLFs, which have suffered from serious anthropogenic destructions in China and need to be restored and managed efficiently (Song and Chen, 2007). It is therefore necessary to identify the genetic variation of Q. fabri because a better understanding of the genetic background of early successional species will greatly contribute to the success of preliminary stages in forest recovery (Davies et al, 2015).…”