Abstract
BackgroundEnvironmental gradients caused by altitudinal gradients may affect genetic variation within and among plant populations and inbreeding within populations. Populations in the upper range periphery of a species may be important source populations for range shifts to higher altitude in response to climate change. In this study we investigate patterns of population genetic variation at upper peripheral and lower more central altitudes in three common plant species of semi-dry grasslands in montane landscapes.Methodology/Principal FindingsIn Briza media, Trifolium montanum and Ranunculus bulbosus genetic diversity, inbreeding and genetic relatedness of individuals within populations and genetic differentiation among populations was characterized using AFLP markers. Populations were sampled in the Swiss Alps at 1800 (upper periphery of the study organisms) and at 1200 m a.s.l. Genetic diversity was not affected by altitude and only in B. media inbreeding was greater at higher altitudes. Genetic differentiation was slightly greater among populations at higher altitudes in B. media and individuals within populations were more related to each other compared to individuals in lower altitude populations. A similar but less strong pattern of differentiation and relatedness was observed in T. montanum, while in R. bulbosus there was no effect of altitude. Estimations of population size and isolation of populations were similar, both at higher and lower altitudes.Conclusions/SignificanceOur results suggest that altitude does not affect genetic diversity in the grassland species under study. Genetic differentiation of populations increased only slightly at higher elevation, probably due to extensive (historic) gene flow among altitudes. Potentially pre-adapted genes might therefore spread easily across altitudes. Our study indicates that populations at the upper periphery are not genetically depauperate or isolated and thus may be important source populations for migration under climate change.
Highlights
Altitudinal gradients comprise an assemblage of environmental, especially climatic, variables which influence the distribution of plant species [1] and, potentially, population genetic variation [2]
We investigated patterns of population genetic diversity in the context of the altitudinal gradient and pollen dispersal mode using the following hypotheses as a heuristic framework: (i) Neutral genetic diversity is lower and inbreeding is higher in upper peripheral populations compared with populations at lower elevations. (ii) Upper peripheral populations are more differentiated and have increased individual relatedness within populations compared to populations at lower elevation. (iii) Altitude has a smaller effect on the above mentioned population genetic traits in the wind-pollinated species compared to the insect-pollinated species
Estimators for population size and distance to nearest neighbouring habitat patch did not differ among the two altitudinal levels in pair-wise Wilcoxon tests (within species Bonferroni corrected P- values (PBonf) of .0.05; estimates in Table 1), despite of B. media which tended to have larger inhabited semi-dry grassland patches within 400 m radius at 1800 compared with 1200 m a.s.l. (PBonf = 0.081)
Summary
Altitudinal gradients comprise an assemblage of environmental, especially climatic, variables which influence the distribution of plant species [1] and, potentially, population genetic variation [2]. Climate change may alter species distributions in mountain regions. Pre-adapted genes for lower altitudinal climatic conditions might move into upper peripheral populations. Due to the uncertainty of plant responses to climate change in mountain regions, an understanding of current distribution patterns of population genetic diversity and differentiation [8] along altitudinal gradients is fundamental for establishing management strategies for resilient species and their habitats. In this study we investigate patterns of population genetic variation at upper peripheral and lower more central altitudes in three common plant species of semidry grasslands in montane landscapes
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