An official website of the United States government
Disentangling genetic structure for genetic monitoring of complex populations
- Award ID(s):
- 1639014
- PAR ID:
- 10055156
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Evolutionary Applications
- Volume:
- 11
- Issue:
- 7
- ISSN:
- 1752-4571
- Page Range / eLocation ID:
- 1149 to 1161
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract Background Disentangling the drivers of genetic differentiation is one of the cornerstones in evolution. This is because genetic diversity, and the way in which it is partitioned within and among populations across space, is an important asset for the ability of populations to adapt and persist in changing environments. We tested three major hypotheses accounting for genetic differentiation—isolation-by-distance (IBD), isolation-by-environment (IBE) and isolation-by-resistance (IBR)—in the annual plant Arabidopsis thaliana across the Iberian Peninsula, the region with the largest genomic diversity. To that end, we sampled, genotyped with genome-wide SNPs, and analyzed 1772 individuals from 278 populations distributed across the Iberian Peninsula. Results IBD, and to a lesser extent IBE, were the most important drivers of genetic differentiation in A. thaliana . In other words, dispersal limitation, genetic drift, and to a lesser extent local adaptation to environmental gradients, accounted for the within- and among-population distribution of genetic diversity. Analyses applied to the four Iberian genetic clusters, which represent the joint outcome of the long demographic and adaptive history of the species in the region, showed similar results except for one cluster, in which IBR (a function of landscape heterogeneity) was the most important driver of genetic differentiation. Using spatial hierarchical Bayesian models, we found that precipitation seasonality and topsoil pH chiefly accounted for the geographic distribution of genetic diversity in Iberian A. thaliana . Conclusions Overall, the interplay between the influence of precipitation seasonality on genetic diversity and the effect of restricted dispersal and genetic drift on genetic differentiation emerges as the major forces underlying the evolutionary trajectory of Iberian A. thaliana .more » « less
-
Understanding the timescales on which different geologic processes influence genetic divergence is crucial to defining and testing geogenomic hypotheses and characterizing Earth- life evolution. To see if we can recover a genetic signal produced by a hypothetical physical barrier to gene flow, we used a geographically explicit simulation approach. We used the CDMetaPop software to simulate heritable genetic, nonadaptive, data for 20 geographically distinct populations distributed throughout the Baja California peninsula of Mexico, a landscape where a transpeninsular seaway barrier has been proposed to have isolated the southern peninsula and caused the observed latitudinal genetic divergence in over 80 terrestrial species. We simulated 10,000 generations of isolation by a barrier under two dispersal scenarios (1 km and 100 km of max. dispersal from population of origin per generation) and three DNA substitution rates (10-7, 10-8 and 10-9 nucleotide substitutions per site per generation). Our simulations indicate that a physical barrier can produce strong genetic divergence within 10,000 generations, comparable to the continuum of values observed in nature for different taxonomic groups and geological settings. We found that the generation time of the organism was by far the most important factor dictating the rate of divergence. Evaluating different generation times (0.02, 0.2, 2 and 20 years), showed that species with longer generation times require longer periods of isolation to accumulate genetic divergence over 10k generations (~1 My). Simulating 10,000 generations of gene flow following removal of the barrier showed that the divergence signal eroded quickly, in less than 1,000 generations in every scenario, a pattern supported by theory from population genetics. These results are particularly relevant to geogenomic studies because they show that ephemeral gene flow barriers produce different magnitudes of genetic signals depending on attributes of the organism, particularly generation time, and that if reproductive isolation is not achieved during isolation, then the evolutionary signal of an ephemeral barrier may not develop. This work helps guide the limits of detectability when integrating genomic data with geological and climatic processes.more » « less
