Forest cover at landscape scales increases male and female gametic diversity of palm seedlings

Abstract

Genetic diversity shapes the evolutionary potential of plant populations. For outcrossing plants, genetic diversity is influenced by effective population size and by dispersal, first of paternal gametes through pollen, and then of paternal and maternal gametes through seeds. Forest loss often reduces genetic diversity, but the degree to which it differentially impacts the paternal and maternal contributions to genetic diversity and the spatial scale at which these impacts are most pronounced are poorly understood. To address these questions, we genotyped 504 seedlings of the animal‐dispersed palm Oenocarpus bataua collected from 29 widely distributed sites across Ecuador and decomposed the contribution of paternal and maternal gametes to overall genetic diversity. The amount of forest cover at a landscape scale (>10 km radius) had an equally significant positive association with both male and female gametic diversity. In addition, there was a significant positive association between forest cover and effective population size. Stronger fine‐scale spatial genetic structure for female versus male gametes was observed at sites with low forest cover, but this did not scale up to differences in male versus female gametic diversity. These findings show that reductions in forest cover at spatial scales much larger than those typically evaluated in ecological studies lead to significant, and equivalent, decreases of diversity in both male and female gametes, and that this association between landscape level forest loss and genetic diversity may be driven directly by reductions in effective population size of O. bataua, rather than by indirect disruptions to local dispersal processes.

Defaunation is associated with increased fine-scale spatial genetic structure in a small-seeded palm despite high abundances of small-bodied seed dispersers

“…As our study sites were in contiguous forest, we do not anticipate that defaunation has impacted pollinator communities making it so that pollination services have likely remained intact. Indeed, beetle and bee pollinators of another South American palm have been found to maintain gene flow even across severely deforested landscapes (Diaz-Martin & Karubian, 2021). In addition to continued pollen-mediated gene flow from an intact effective population size, a 'time lag effect' may have buffered the recruiting seedlings in our defaunated site from decreases in genetic diversity.…”

“…Most research investigating anthropogenic effects on seed dispersal services in tropical forests has focused on large seeded plants because they are seen as the most vulnerable to losing dispersal services as the large-bodied mutualistic partners they specialize on to disperse their large seeds tend to disappear first after human disturbances (Dirzo et al, 2014;Galetti et al, 2013;Koerner et al, 2017;Kurten, 2013). Such studies have linked the loss of large-bodied frugivores to decreased dispersal and recruitment success of larger seeded plants (Bagchi et al, 2018;Holbrook & Loiselle, 2009;Vanthomme et al, 2010), changes in allele frequencies and lower allelic richness (C. S. Carvalho et al, 2016;Giombini et al, 2017), as well as higher spatial genetic structure and lower genetic diversity (Browne et al, 2015;Diaz-Martin & Karubian, 2021;Giombini et al, 2017). However, generalist relationships are much more common in tropical forests where most plants have smallto medium-sized fruits and seeds that can be consumed by small-, medium-, and large-bodied animals (Howe & Smallwood, 1982;Malhado et al, 2015;McConkey & Brockelman, 2011).…”

The mutualism–antagonism continuum in Neotropical palm–frugivore interactions: from interaction outcomes to ecosystem dynamics

“…Finally, an approach that combines a spatial assessment of the distribution of seedlings and adults (e.g. source trees) with molecular techniques such as genetic parentage analysis (Sezen et al ., 2009 ; Choo, Juenger & Simpson, 2012 ; Giombini, Bravo & Tosto, 2016 ; Giombini et al ., 2017 ; Browne & Karubian, 2018 b ; Diaz‐Martin & Karubian, 2021 ) is a way to shed light on how frugivory influences the spatial and genetic structure of palm populations. The non‐exhaustive list of methods provided here (Fig.…”