Distribution,growth performance and genetic variation of <Emphasis Type="Italic">Erigeron annuus</Emphasis> in the Swiss Alps |
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Authors: | Miluse Trtikova Sabine Güsewell Matthias Baltisberger Peter J Edwards |
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Institution: | (1) Institute of Integrative Biology, ETH Zurich, 8092 Zurich, Switzerland |
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Abstract: | We investigated whether local adaptation has been important in enabling the invasive apomictic species Erigeron annuus to extend its altitudinal range in the Swiss Alps. We first conducted a field survey along several major roads crossing the
Swiss Alps to study the distribution and growth performance of E. annuus along an altitudinal gradient. We then used amplified fragment length polymorphism to assess genetic variation within and
among populations originating from different altitudes. To complement the molecular analyses, we compared the performance
of genotypes with different distributions (i.e. local, occasional, widespread genotypes) in two common gardens at 400 m and
1,000 m a.s.l. Although E. annuus was seldom found above 1,000 m, plant performance in field populations did not decrease with increasing altitude. However,
there was a significant decline in genotypic diversity within populations, and highland (711–1,100 m) populations were more
differentiated (Gst = 0.55) than lowland (200–530 m) populations (Gst = 0.33). In the common garden experiment, local genotypes
(i.e. those restricted to a single population) grew less vigorously than widespread genotypes, and were less likely to reproduce.
We found no evidence for on-going adaptive changes and conclude that any selection acting on particular genotypes at the altitudinal
limit is weak. This leads us to propose that the patterns in the distribution of genotypic diversity in E. annuus are governed by processes of occasional sexual reproduction, dispersal and extinction that are to a large extent independent
of altitude. |
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