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

Abstract

One of the most intriguing questions in plant ecology is which evolutionary strategy allows widely distributed species to increase their ecological range and grow in changing environmental conditions. Phenotypic plasticity and local adaptations are major processes governing species range margins, but little is known about their relative contribution for tree species distribution in tropical forest regions. We investigated the relative role of phenotypic plasticity and local adaptation in the ecological distribution of the widespread palm Euterpe edulis in the Brazilian Atlantic Forest. Genetic sampling and experiments were performed in old‐growth remnants of two forest types with higher (Seasonal Semideciduous Forests vs. Submontane Rainforest) and lower biogeographic association and environmental similarities (Submontane Rainforest vs. Restinga Forest). We first assessed the molecular genetic differentiation among populations, focusing on the group of loci potentially under selection in each forest, using single‐nucleotide polymorphism (SNPs) outliers. Further, we looked for potential adaptive divergence among populations in a common garden experiment and in reciprocal transplants for two plant development phases: seedling establishment and sapling growth. Analysis with outlier loci indicated that all individuals from the Semideciduous Forest formed a single group, while another group was formed by overlapping individuals from Submontane Rainforest and Restinga Forest. Molecular differentiation was corroborated by reciprocal transplants, which yielded strong evidence of local adaptations for seedling establishment in the biogeographically divergent Rainforest and Semideciduous Forest, but not for Restinga Forest and Submontane Rainforest. Phenotypic plasticity for palm seedling establishment favors range expansion to biogeographically related or recently colonized forest types, while persistence in the newly colonized ecosystem may be favored by local adaptations if climatic conditions diverge over time, reducing gene flow between populations. SNPs obtained by next‐generation sequencing can help exploring adaptive genetic variation in tropical trees, which impose several challenges to the use of reciprocal transplants.

The Potential for Rapid Evolution under Anthropogenic Climate Change

“…That such variation is adaptive has occasionally been demonstrated by showing that populations perform at their peak under the conditions experienced in the region where the population originated. Experiments have identified among-population adaptive variation in traits such as heatshock protein production in corals [78], growth potential in palms [84], lethal temperatures in snails [80] and thermal performance in anole lizards [45].…”

Genetic diversity and population structure of Euterpe edulis by REML/BLUP analysis of fruit morphology and microsatellite markers

“…In E. edulis, it has been assessed using microsatellite markers (Gaiotto et al 2003, Conte et al 2006) and isozymes (Conte et al 2008). Morphology-based diversity studies on E. edulis have also been carried out and detcted a wide variation in fruit morphology among natural populations (Cardoso et al 2000, Oliveira et al 2015, Marçal et al 2016, Brancalion et al 2018).…”

Genetic structure among the endangered Brazilian Euterpe Edulis Mart (Arecaceae) morphotypes

“…These F ST values indicate unusual genetic divergence among E. edulis populations compared to other populations of the species, even when under influence of fragmentation and geographically distant (Conte et al , 2008;Santos et al , 2015). Thus, we believe that the differences found between the populations of this palm tree should not be related to habitat fragmentation, but to naturally occurring evolutionary events, such as local adaptation (Brancalion et al , 2018). In addition, it is important to draw attention to RE and BN that have the same morphotype and are geographically close, with low to moderate F ST , indicating occurrence of gene flow, as reported by Gaiotto et al (2003) for these same populations.…”

“…Although we have used microsatellite markers that are considered neutral, we believe that the genetic clusters that distinguish E. edulis morphotypes are a consequence of populations being shaping in different environmental or ecological conditions. This hypothesis is based on recent studies using SNPs (Single Nucleotide Polymorphism) markers, demonstrating that E. edulis populations inserted in different environmental and ecological conditions are genetically different (Brancalion et al , 2018;Alves-Pereira et al , 2019). Thus, it is believed that there is adaptation of species to different conditions and that this adaptation remains mainly locally, favoring the genetic divergence directed by the environment (Rellstabet al , 2017;Sork, 2017).…”

“…Currently, it is only known that populations ofE. edulis in different environmental conditions are genetically different (Brancalion et al , 2018;Alves-Pereira et al , 2019). However, it is not known whether populations with morphological differences are also genetically different.…”