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Nuclear and plastid haplotypes suggest rapid diploid and polyploid speciation in the N Hemisphere Achillea millefolium complex (Asteraceae).

Abstract：

BACKGROUND:Species complexes or aggregates consist of a set of closely related species often of different ploidy levels, whose relationships are difficult to reconstruct. The N Hemisphere Achillea millefolium aggregate exhibits complex morphological and genetic variation and a broad ecological amplitude. To understand its evolutionary history, we study sequence variation at two nuclear genes and three plastid loci across the natural distribution of this species complex and compare the patterns of such variations to the species tree inferred earlier from AFLP data. RESULTS:Among the diploid species of A. millefolium agg., gene trees of the two nuclear loci, ncpGS and SBP, and the combined plastid fragments are incongruent with each other and with the AFLP tree likely due to incomplete lineage sorting or secondary introgression. In spite of the large distributional range, no isolation by distance is found. Furthermore, there is evidence for intragenic recombination in the ncpGS gene. An analysis using a probabilistic model for population demographic history indicates large ancestral effective population sizes and short intervals between speciation events. Such a scenario explains the incongruence of the gene trees and species tree we observe. The relationships are particularly complex in the polyploid members of A. millefolium agg. CONCLUSIONS:The present study indicates that the diploid members of A. millefolium agg. share a large part of their molecular genetic variation. The findings of little lineage sorting and lack of isolation by distance is likely due to short intervals between speciation events and close proximity of ancestral populations. While previous AFLP data provide species trees congruent with earlier morphological classification and phylogeographic considerations, the present sequence data are not suited to recover the relationships of diploid species in A. millefolium agg. For the polyploid taxa many hybrid links and introgression from the diploids are suggested.

journal_name

BMC Evol Biol

journal_title

BMC evolutionary biology

authors

Guo YP,Wang SZ,Vogl C,Ehrendorfer F

doi

10.1186/1471-2148-12-2

subject

Has Abstract

pub_date

2012-01-03 00:00:00

pages

issn

1471-2148

pii

1471-2148-12-2

journal_volume

pub_type

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Nuclear and plastid haplotypes suggest rapid diploid and polyploid speciation in the N Hemisphere Achillea millefolium complex (Asteraceae).