Rare genotype advantage promotes survival and genetic diversity of a tropical palm

Abstract

Negative density dependence, where survival decreases as density increases, is a well-established driver of species diversity at the community level, but the degree to which a similar process might act on the density or frequency of genotypes within a single plant species to maintain genetic diversity has not been well studied in natural systems. In this study, we determined the maternal genotype of naturally dispersed seeds of the palm Oenocarpus bataua within a tropical forest in northwest Ecuador, tracked the recruitment of each seed, and assessed the role of individual-level genotypic rarity on survival. We demonstrate that negative frequency-dependent selection within this species conferred a survival advantage to rare maternal genotypes and promoted population-level genetic diversity. The strength of the observed rare genotype survival advantage was comparable to the effect of conspecific density regardless of genotype. These findings corroborate an earlier, experimental study and implicate negative frequency-dependent selection of genotypes as an important, but currently underappreciated, determinant of plant recruitment and within-species genetic diversity. Incorporating intraspecific genetic variation into studies and theory of forest dynamics may improve our ability to understand and manage forests, and the processes that maintain their diversity.

The relative contributions of seed and pollen dispersal to gene flow and genetic diversity in seedlings of a tropical palm

“…In particular, we consider it possible that a bimodal distribution of seed dispersal distances related to frugivore dispersal processes may exist (e.g., Jordano et al, ), but may be difficult to detect due to the relative rarity of long‐distance dispersal events. Although anecdotal data from GPS tracking devices indicate umbrellabirds are capable of dispersing seeds several kilometers (Karubian & Durães, ), we observed low rates of seed immigration and a maximum seed dispersal distance of 656 m in this study, similar to a 3% rate of seed immigration and maximum seed dispersal of 645 m in a separate study with naturally dispersed O. bataua seeds (Browne & Karubian, ). There were also differences among our three plot types in their spatial arrangement relative to source trees and to the boundaries of our study area that may have led us to underestimate long‐distance dispersal events (both pollen and seed) to Lek plots, due to their lower average distance to source trees and longer distance from the study boundary.…”

“…However, a lack of seed dispersal creates strong spatial genetic structure among seedlings despite robust pollen movement, supporting the perspective that seed dispersal is a key determinant of fine‐scale genetic structure among seedlings (Hamrick, ; Sork & Smouse, ). Future research might extend this work on seedlings to investigate the ultimate consequences of these dispersal differences for genetic structure of adults; it is possible that effects may be limited due to and a survival advantage for rare genotypes (Browne & Karubian, , ) in this study population.…”

Evidence of within-species specialization by soil microbes and the implications for plant community diversity

“…Other studies show that the seedlings that establish near conspecific adults are not necessarily offspring, but instead represent a diversity of genotypes (30,31). In addition, recent experimental work with a tropical palm species has shown that seedlings with rare genotypes are more likely to survive than seedlings with common genotypes (20), and related theoretical work suggested that this can promote population-level genetic diversity (32). Our experimental results suggest that the patterns found in those previous studies could have been driven by highly specialized soil microbes, but additional studies are needed to confirm whether soil microbes produce these patterns of seedling recruitment under natural environmental conditions.…”

Intraspecific Variation on Palm Leaf Traits of Co-occurring Species—Does Local Hydrology Play a Role?

“…Again, there are no studies of intraspecific variation on palms regardless of the evidence for genetic variation from local to broad scales. Genotypic negative frequency-dependent selection has been shown to increase genetic diversity at local scales (Browne and Karubian, 2018). At large scales, genetic variation across species ranges has been detected in widespread palms (Gomes et al, 2011;Melo et al, 2018), suggesting that widespread palms may have enough genetic variation to adjust to varying environments.…”