Abstract
BackgroundHow species ranges form in landscapes is a matter of long-standing evolutionary interest. However, little is known about how natural phenotypic variations of ecologically important traits contribute to species range expansion. In this study, we examined the phylogeographic patterns of phenotypic changes in life history (seed production) and phenological (flowering time) traits during the range expansion of Aegilops tauschii Coss. from the Transcaucasus and Middle East to central Asia.ResultsOur comparative analyses of the patterns of natural variations for those traits and their association with the intraspecific lineage structure showed that (1) the eastward expansion to Asia was driven by an intraspecific sublineage (named TauL1b), (2) high seed production ability likely had an important role at the initial dispersal stage of TauL1b’s expansion to Asia, and (3) the phenological change to early flowering phenotypes was one of the key adaptation events for TauL1b to further expand its range in Asia.ConclusionsThis study provides for the first time a broad picture of the process of Ae. tauschii’s eastward range expansion in which life history and phenological traits may have had respective roles in its dispersal and adaptation in Asia. The clear association of seed production and flowering time patterns with the intraspecific lineage divergence found in this study invites further genetic research to bring the mechanistic understanding of the changes in these key functional traits during range expansion within reach.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0496-9) contains supplementary material, which is available to authorized users.
Highlights
How species ranges form in landscapes is a matter of long-standing evolutionary interest
Our comparative analyses of the patterns of natural variations for those traits and their association with the intraspecific lineage structure showed that (1) the eastward expansion to Asia was driven by an intraspecific sublineage, (2) high seed production ability likely had an important role at the initial dispersal stage of TauL1b’s expansion to Asia, and (3) the phenological change to early flowering habit was one of the key adaptation events for TauL1b to further expand its range in Asia
To further investigate the intraspecific lineage structure, we analyzed a larger Diversity Arrays Technology (DArT) genotype dataset that was obtained by the use of an additional 84 markers (253 markers in total) for the same set of Ae. tauschii accessions using a Bayesian clustering approach implemented in the software program STRUCTURE 2.3 [34]
Summary
How species ranges form in landscapes is a matter of long-standing evolutionary interest. Little is known about how natural phenotypic variations of ecologically important traits contribute to species range expansion. We examined the phylogeographic patterns of phenotypic changes in life history (seed production) and phenological (flowering time) traits during the range expansion of Aegilops tauschii Coss. From a broad ecological viewpoint, there are two important drivers for species range expansion: dispersal and adaptation. Many genetic studies on the mechanisms that underlie the adaptive change in ecologically important traits (including dispersal traits) were done using model species, whereas a few successful studies addressed the issue using non-model species [11,12,13,14]. Further studies are required to better understand the genetic causes for diverse ecologically important trait changes in the context of the tempo and mode of species range expansion
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