Genetic monitoring of translocated plant populations in practice

Abstract

Many critically endangered species have been reduced to small and isolated relict populations that are often genetically depauperate and suffer from genetic load and low fitness (Aguilar, Ashworth, Galetto,

Genetic monitoring to assess the success of restoring rare plant populations with mixed gene pools

“…They translocated 700 nursery‐grown transplants to each of three grassland sites, evenly mixing transplants that had been cultivated by seed sourced from the two source populations (Figure 1). After two years, Van Rossum et al (2020) assessed genetic variation and structure in founder transplants, seed progeny and new recruits (F1 offspring) and quantified fitness components of seed progeny from founder transplants and newly established F1 offspring.…”

“…In many cases, the genetic benefits of mixing source populations during genetic rescue are expected to outweigh the risks of outbreeding depression and loss of local adaption (Ralls et al., 2018). After genetic augmentation using mixed sources at two sites with declining native populations, Van Rossum (2020) found increased genetic diversity and seed set relative to pretranslocation levels, although translocated and native plants exhibited minimal outcrossing. Their study design also allowed them to assess the extent of pollen flow and seed dispersal—key processes typically not evaluated in plant translocations (Menges, 2008)—in contributing to spatial genetic structure.…”

“…A major strength of Van Rossum et al (2020) is that it is one of the first to track genetic structure and variation throughout the process of translocation, which can be susceptible to genetic changes across multiple stages. For example, loss of genetic diversity can occur if source populations are undersampled, specific genotypes become favoured during propagation or nursery production, or small founder sizes result from poor transplant survival in the field.…”

“…In self‐incompatible species, loss of genetic diversity at any of these stages could reduce the availability of compatible mates and compromise plant fitness in translocated populations. The study design of Van Rossum et al (2020), which allowed them to detect losses in genetic variation at any of these stages, revealed that mixed‐source translocations with A. montana overcame these potential genetic and demographic barriers; genetic variation in translocations with mixed population sources remained similar or increased across successive generations. A robust translocation design also contributed to this early restoration success, including using large founder sizes from diverse population sources and managing habitat at translocation sites.…”

“…Van Rossum et al (2020) in this issue of Molecular Ecology uses detailed assessments of genetic parameters and fitness to understand the outcomes of mixing two genetically differentiated source populations in translocations of the rare, self-incompatible perennial herb, Arnica montana, whose populations are declining at low elevations in Western Europe. They examine genetic changes throughout the translocation process (source populations to F1 offspring) and demonstrate the maintenance of high genetic diversity in successive generations for all three translocations.…”