Contemporary and historic factors influence differently genetic differentiation and diversity in a tropical palm

Abstract

Population genetics theory predicts loss in genetic variability because of drift and inbreeding in isolated plant populations; however, it has been argued that long-distance pollination and seed dispersal may be able to maintain gene flow, even in highly fragmented landscapes. We tested how historical effective population size, historical migration and contemporary landscape structure, such as forest cover, patch isolation and matrix resistance, affect genetic variability and differentiation of seedlings in a tropical palm (Euterpe edulis) in a human-modified rainforest. We sampled 16 sites within five landscapes in the Brazilian Atlantic forest and assessed genetic variability and differentiation using eight microsatellite loci. Using a model selection approach, none of the covariates explained the variation observed in inbreeding coefficients among populations. The variation in genetic diversity among sites was best explained by historical effective population size. Allelic richness was best explained by historical effective population size and matrix resistance, whereas genetic differentiation was explained by matrix resistance. Coalescence analysis revealed high historical migration between sites within landscapes and constant historical population sizes, showing that the genetic differentiation is most likely due to recent changes caused by habitat loss and fragmentation. Overall, recent landscape changes have a greater influence on among-population genetic variation than historical gene flow process. As immediate restoration actions in landscapes with low forest amount, the development of more permeable matrices to allow the movement of pollinators and seed dispersers may be an effective strategy to maintain microevolutionary processes.

Lessons from a palm: genetic diversity and structure in anthropogenic landscapes from Atlantic Forest, Brazil

“…Contrary to our initial hypothesis, forest loss at a landscape scale did not influence the genetic diversity of E. edulis. Our results indicate that, regardless of the amount of forest cover remaining at the landscape level, the genetic diversity of E. edulis was still high at all sampling sites and was quantitatively similar to other populations of the same species (Gaiotto et al 2003;Conte et al 2008, Carvalho et al 2015. This pattern may reflect the recent history of deforestation because land-use change is often faster than those organisms change genetically (Holzhauer et al 2006), and because small populations can may still maintain high genetic diversity due to very recent population declines (Klank et al 2012).…”

“…However, a recent study of E. edulis in the Brazilian Atlantic Forest has found that populations maintain high genetic diversity despite human disturbance (Carvalho et al 2015). Thus, we believe that E. edulis is a good example of a tropical plant that is experiencing local extirpation before suffering genetic consequences.…”

Genetic diversity and differentiation among Prosopis alba (Leguminosae) populations from dry valleys of Bolivia with different levels of human disturbance and altitude

“…Allelic richness is a parameter that tends to respond rapidly to habitat loss or fragmentation and the remaining parameters are expected to have a higher temporal lag in the variation (da Silva Carvaho, ; Keyhonbadi, Roland, Matter, & Stobeck, ). Habitat perturbation can take longer to affect heterozygosity (Collevatti, Grattapaglia, & Hay, ), and it is also possible that population size of our studied populations has not yet affected severely this index (Kramer et al, ).…”

Phenotypic plasticity and local adaptation favor range expansion of a Neotropical palm

“…Fernandez; Wendt et al., 2011), but molecular analysis with isoenzymes did not find relevant differentiation (Martins et al., 2007), and E. espiritosantensis is no longer considered a valid species. Populations with smaller seeds are found in defaunated forests, as a consequence of a rapid evolutionary change driven by the ecological extinction of large‐gaped birds (Carvalho, Ribeiro, Cortes, Galetti, & Collevatti, 2015; Galetti et al., 2013). Molecular analyses have corroborated the explanations of population divergences according to the site of origin (Gaiotto, Grattapaglia, & Vencovsky, 2003) and to forest fragmentation levels (Carvalho et al., 2015), but neither the investigation of adaptive molecular divergence with SNPs, nor reciprocal transplant experiments, had been performed for E. edulis so far.…”

“…Populations with smaller seeds are found in defaunated forests, as a consequence of a rapid evolutionary change driven by the ecological extinction of large‐gaped birds (Carvalho, Ribeiro, Cortes, Galetti, & Collevatti, 2015; Galetti et al., 2013). Molecular analyses have corroborated the explanations of population divergences according to the site of origin (Gaiotto, Grattapaglia, & Vencovsky, 2003) and to forest fragmentation levels (Carvalho et al., 2015), but neither the investigation of adaptive molecular divergence with SNPs, nor reciprocal transplant experiments, had been performed for E. edulis so far. In addition, investigating the adaptive potential of E. edulis may be critical to assess whether this threatened species will be able to overcome the selective barriers imposed by climate change—a major threat for plant species conservation in the Atlantic Forest (Colombo & Joly, 2010)—as reduced population size and gene flow caused by habitat fragmentation and overexploitation of palm heart, summed with the vulnerability of E. edulis to drought (Silva‐Matos & Alves, 2008), may compromise the persistence of this species under a changing climate.…”