No abstract

There is an urgent societal need to better predict how specific genotypes perform in different environments. For example, in order for assisted gene flow to contribute to robust populations of harvested forests (Aitken & Bemmels, 2016) or key fish habitat reef systems (Matz et al., 2020), transplanted genotypes must be good candidates to increase the overall population fitness. Similarly, restoration of degraded ecosystems depends heavily on the identification of optimally adapted source populations if restoration efforts are to be successful (Houde et al., 2015). Likewise, climate change is a growing threat to biodiversity (Nunez et al., 2019;Urban et al., 2016) and there is a need to address environmental impacts on vulnerable populations. Most efforts to assess climate change impacts

Heterozygote disadvantage is potentially a potent driver of population genetic divergence. Also referred to as underdominance, this phenomena describes a situation where a genetic heterozygote has a lower overall fitness than either homozygote. Attention so far has mostly been given to underdominance within a single population and the maintenance of genetic differences between two populations exchanging migrants. Here we explore the dynamics of an underdominant system in a network of multiple discrete, yet interconnected, populations. Stability of genetic differences in response to increases in migration in various topological networks is assessed. The network topology can have a dominant and occasionally non-intuitive influence on the genetic stability of the system.

Plant-associated microbes are critical players in host health, fitness and productivity. Despite microbes’ importance in plants, seeds are mostly sterile, and most plant microbes are recruited from an environmental pool. Surprisingly little is known about the processes that govern how environmental microbes assemble on plants in nature. In this study we examine how bacteria are distributed across plant parts, and how these distributions interact with spatial gradients. We sequenced amplicons of bacteria from the surfaces of six plant parts and adjacent soil of Scaevola taccada, a common beach shrub, along a 60 km transect spanning O’ahu island’s windward coast, as well as within a single intensively-sampled site. Bacteria are more strongly partitioned by plant part as compared with location. Within S. taccada plants, microbial communities are highly nested: soil and rhizosphere communities contain much of the diversity found elsewhere, whereas reproductive parts fall at the bottom of the nestedness hierarchy. Nestedness patterns suggest either that microbes follow a source/sink gradient from the ground up, or else that assembly processes correlate with other traits, such as tissue persistence, that are vertically stratified. Our work shines light on the origins and determinants of plant-associated microbes across plant and landscape scales.