Abstract
Within plant populations, space-restricted gene movement, together with environmental heterogeneity, can result in a spatial variation in gene frequencies. In biennial plants, inter-annual flowering migrants can homogenize gene frequencies between consecutive cohorts. However, the actual impact of these migrants on spatial genetic variation remains unexplored. Here, we used 10 nuclear microsatellite and one plastid genetic marker to characterize the spatial genetic structure within two consecutive cohorts in a population of the biennial plant Erysimum mediohispanicum (Brassicaceae). We explored the maintenance of this structure between consecutive flowering cohorts at different levels of complexity, and investigated landscape effects on gene flow. We found that cohorts were not genetically differentiated and showed a spatial genetic structure defined by a negative genetic-spatial correlation at fine scale that varied in intensity with compass directions. This spatial genetic structure was maintained when comparing plants from different cohorts. Additionally, genotypes were consistently associated with environmental factors such as light availability and soil composition, but to a lesser extent compared with the spatial autocorrelation. We conclude that inter-annual migrants, in combination with limited seed dispersal and environmental heterogeneity, play a major role in shaping and maintaining the spatial genetic structure among cohorts in this biennial plant.
Highlights
Life span, permitting the existence of inter-annual migrants that bridge years (‘facultative biennials’)[23,24]
We did not find genetic differentiation between two consecutive cohorts of the biennial plant E. mediohispanicum, a result indicating that these cohorts belong to the same gene pool and behave cohesively
We found an association between the microenviroment and the spatial genetic variation
Summary
Life span, permitting the existence of inter-annual migrants that bridge years (‘facultative biennials’)[23,24]. In plants presenting limited seed dispersal, the localized arrival of inter-annual migrants may have predictable effects on the SGS, equalizing the spatial variation in allelic frequencies between consecutive cohorts and balancing population size fluctuations. Slightly self-compatible, this species needs pollinators for a complete seed set[28], whose dispersal occurs at very short distances due to its barochorous dispersal strategy[29]. Populations of this species are patchily distributed and formed by tens to several hundreds of individuals[30]. We assess associations among the spatial variation in genotypes and environmental factors using autoregressive spatial models
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