An ecological approach to measuring the evolutionary consequences of gene flow from crops to wild or weedy relatives

Abstract

Premise of the study:Agricultural practices routinely create opportunities for crops to hybridize with wild relatives, leading to crop gene introgression into wild genomes. Conservationists typically worry this introgression could lead to genetic homogenization of wild populations, over and above the central concern of transgene escape. Alternatively, viewing introgression as analogous to species invasion, we suggest that increased genetic diversity may likewise be an undesirable outcome.Methods:Here, we compare the sensitivity of conventional population genetic metrics with species diversity indices as indicators of the impact of gene flow on genetic diversity. We illustrate this novel approach using multilocus genotype data (12 allozyme loci) from 10 wild (Beta vulgaris subsp. maritima) and eight putative crop–wild hybrid beet populations (B. vulgaris subsp. vulgaris × B. vulgaris subsp. maritima) scattered throughout Europe.Results:Conventional population genetic metrics mostly failed to detect shifts in genetic composition of putative hybrid populations. By contrast, species diversity indices unambiguously revealed increased genetic diversity in putative hybrid populations.Discussion:We encourage other workers to explore the utility of our more sensitive approach for risk assessment prior to the release of transgenic crops, with a view toward widespread adoption of our method in studies aimed at detecting allelic invasion.

Little White Lies: Pericarp Color Provides Insights into the Origins and Evolution of Southeast Asian Weedy Rice

“…If Malaysian weeds are, in fact, a crucible where crop and wild alleles can recombine, the weeds could also potentially serve as a bridge for the introduction of crop alleles into wild populations (Snow et al 2010; Campbell et al 2016) or vice versa (Félix et al 2014). Of these two gene flow possibilities, wild-to-crop gene flow may be the less serious problem.…”

Accessing the genetic content of Xylocopa frontalis bees (Apidae, Xylocopini) for sustainable management in pollination services of passion fruit

“…The introgression of new haplotypes or alleles between populations may lead to the homogenization of the populations' gene pool. A rare allele can be replaced by a common one from a different area (Olden et al 2004;Campbell et al 2016), and the loss of genetic variability of locally adapted populations can be disadvantageous to species in the long term, changing for instance the capacity to expand its distribution or increase vulnerability to the invasion of competitors (Olden et al 2004).…”

Clonal diversity and spatial genetic structure in the long-lived herb, Prairie trillium

“…We found the flowering stage class to have significantly higher levels of genetic variation when information theory-based calculations were employed whereas traditional population genetic measures demonstrated no detectable differences. The finding that Shannon-Wiener based-measures are more likely to detect differences among means has recently been noted with regard to crop-wild gene flow literature [34–35] and reviewed in Sherwin et al [36]. Other plant studies of genetic variation in different plant stage classes have demonstrated mixed results with some studies finding no evidence for differences among stage classes (e.g., in another Trillium species; [46]) to those demonstrating significant differences (e.g., bamboo saplings had higher levels of genetic diversity than seedlings; [47]).…”

“…In GenAlEx v. 6.5 [33], we calculated Nei's unbiased gene diversity corrected for sample size (uHe) for all groupings. Recent work in the crop-wild gene flow literature (e.g., [34–35]) and more broadly in population genetics [36], has demonstrated that information theory-based measures (i.e., Shannon-Weiner) may be more sensitive to detecting genetic diversity differences among groups than traditional population genetic measures. We therefore compared these measures (uHe vs. uS-W) in our data set here.…”