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

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• 作者：Christina M. Müller ; Benjamin Schulz ; Daniel Lauterbach…
• 关键词：Environmental association studies ; Fragmented habitats ; Isolation by distance (IBD) ; Isolation by environment (IBE) ; Range edge populations
• 刊名：Plant Systematics and Evolution
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：303
• 期：1
• 页码：91-104
• 全文大小：1408KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Plant Sciences; Plant Ecology; Plant Anatomy/Development; Plant Systematics/Taxonomy/Biogeography;
• 出版者：Springer Vienna
• ISSN：2199-6881
• 卷排序：303

文摘

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 × 20 km2), 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 Φ_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.