Abstract
Identifying environmental factors that structure intraspecific genetic diversity is of interest for both habitat preservation and biodiversity conservation. Recent advances in statistical and geographical genetics make it possible to investigate how environmental factors affect geographic organisation and population structure of molecular genetic diversity within species. Here we present a study on a common and wide ranging insect, the blue tailed damselfly Ischnuraelegans, which has been the target of many ecological and evolutionary studies. We addressed the following questions: (i) Is the population structure affected by longitudinal or latitudinal gradients?; (ii) Do geographic boundaries limit gene flow?; (iii) Does geographic distance affect connectivity and is there a signature of past bottlenecks?; (iv) Is there evidence of a recent range expansion and (vi) what is the effect of geography and climatic factors on population structure? We found low to moderate genetic sub-structuring between populations (mean FST = 0.06, Dest = 0.12), and an effect of longitude, but not latitude, on genetic diversity. No significant effects of geographic boundaries (e.g. water bodies) were found. FST-and Dest-values increased with geographic distance; however, there was no evidence for recent bottlenecks. Finally, we did not detect any molecular signatures of range expansions or an effect of geographic suitability, although local precipitation had a strong effect on genetic differentiation. The population structure of this small insect has probably been shaped by ecological factors that are correlated with longitudinal gradients, geographic distances, and local precipitation. The relatively weak global population structure and high degree of genetic variation within populations suggest that I. elegans has high dispersal ability, which is consistent with this species being an effective and early coloniser of new habitats.
Highlights
The spatial structuring of intraspecific neutral genetic diversity contains important information about both historical and current evolutionary processes
To investigate the geographic pattern of intraspecific genetic diversity of I. elegans, we investigated the molecular structure of 22 populations over most of the western part of this species’ geographical range, along with four populations of its congeneric sister species I. graellsii
Population genetic analyses and geographic structure Populations contained a substantial fraction of genetic variation, as shown by the pronounced genetic diversity at each locus (Table 1)
Summary
The spatial structuring of intraspecific neutral genetic diversity contains important information about both historical and current evolutionary processes. Intrinsic life history traits of the species studied (e.g. dispersal and lifespan) affect population genetic structure and the geographic distribution of molecular diversity [7,8]. A variety of factors have been put forward to explain the geographic structure of genetic diversity within species, only a few studies have explicitly tested the causal environmental factors behind these geographic patterns [15]. Evaluating the importance of different environmental factors is crucial since these factors often interact dynamically with each other, thereby confusing the spatial signatures of molecular differentiation. A recent study by Kittlein and Gaggiotti[16] found that the interactions between various environmental factors can mask expected isolation-by-distance signatures that are often found in population genetic studies
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