Geropogon hybridus (L.) Sch.Bip. (Asteraceae) exhibits micro-geographic genetic divergence at ecological range limits along a steep precipitation gradient

Abstract

We analyzed the population genetic pattern of 12 fragmented Geropogon hybridus ecological range edge populations in Israel along a steep precipitation gradient. In the investigation area (45 9 20 km 2), the annual mean precipitation changes rapidly from 450 mm in the north (Mediterranean-influenced climate zone) to 300 mm in the south (semiarid climate zone) without significant temperature changes. Our analysis (91 individuals, 12 populations, 123 polymorphic loci) revealed strongly structured populations (AMOVA U ST = 0.35; P \ 0.001); however, differentiation did not change gradually toward range edge. IBD was significant (Mantel test r = 0.81; P = 0.001) and derived from sharply divided groups between the northernmost populations and the others further south, due to dispersal or environmental limitations. This was corroborated by the PCA and STRUCTURE analyses. IBD and IBE were significant despite the micro-geographic scale of the study area, which indicates that reduced precipitation toward range edge leads to population genetic divergence. However, this pattern diminished when the hypothesized gene flow barrier was taken into account. Applying the spatial analysis method revealed 11 outlier loci that were correlated to annual precipitation and, moreover, were indicative for putative precipitation-related adaptation (BAYESCAN, MCHEZA). The results suggest that even on micro-geographic scales, environmental factors play prominent roles in population divergence, genetic drift, and directional selection. The pattern is typical for strong environmental gradients, e.g., at species range edges and ecological limits, and if gene flow barriers and mosaic-like structures of fragmented habitats hamper dispersal. Keywords Environmental association studies Á Fragmented habitats Á Isolation by distance (IBD) Á Isolation by environment (IBE) Á Range edge populations Handling editor: Christoph Oberprieler.

Genetic Structure and Eco-Geographical Differentiation of Wild Sheep Fescue (Festuca ovina L.) in Xinjiang, Northwest China

“…For out-crossed species, gene flow via pollen and seed dispersal is one of the most important determinants in the establishment of population genetic diversity and structure [ 16 ]. However, gene flow is often interrupted by isolation and environmental heterogeneity [ 17 , 18 , 19 ]. Notably, historical climatic oscillations have greatly influenced the biodiversity of plant species.…”

“…Actually, the heterogeneity of landscapes triggered by orogenic movements has formed many special habitats [ 34 , 35 ]. Many alleles and traits related to adaptation have been filtered under these special eco-geographic habitats due to their independent development at different elevations or under different edaphic characteristics, temperatures or levels of precipitation [ 18 , 36 ]. The morphological assessment and isozyme methods need a long time and considerable effort to establish the individuals and populations in replicated field experiments in homogenous environments, while the molecular marker techniques such as amplified fragment-length polymorphism (AFLP) analysis are more efficient because they provide much more detailed insight into genetic diversity and variation at the DNA level [ 37 , 38 ].…”

Divergent selection and genetic structure of Sideritis scardica populations from southern Balkan Peninsula as revealed by AFLP fingerprinting

“…This approach correlates individual loci occurrence with environmental variables, thus aiming to determine whether each investigated molecular marker is selected by one or a set of specific environmental variables 16 . The described methods provide the opportunity to identify adaptive genetic variation in non-model organisms for which the genomic data are scarce and species are of conservation concern 21 .…”

Genetic Structure and Eco-Geographical Differentiation of Wild Sheep Fescue (<em>Festuca ovina</em> L.) in Xinjiang, Northwest China

“…Actually, the heterogeneity of landscapes triggered by orogenic movements has formed many special habitats [34,35]. Many alleles and traits related to adaptation have been filtered under these special eco-geographic habitats due to their independent development at different elevations or under different edaphic characteristics, temperatures or levels of precipitation [18,36]. Replacing morphological assessment and isozyme methods, modern molecular marker techniques such as amplified fragment-length polymorphism (AFLP) analysis provide much more detailed insight into genetic diversity and variation at the DNA level [37,38].…”