Bryological and Lichenological Section/ABLS
Villarreal, Juan Carlos , McFarland, Kenneth D. , Goffinet, Bernard .
Thousands of years without sex: The case of the Southern Appalachian Nothoceros aenigmaticus
Sex is widespread across the eukaryotic Tree of Life, despite its intrinsic costs, suggesting it must have a vital role in species’ survival and maintenance. However, the persistence of some lineages (e.g. bdelloid rotifers) over tens of millions of years without engaging in sexual reproduction challenges this paradigm. The frequency of such “evolutionary scandals” remains ambiguous, particularly among plants. Despite the fact that clonality and other forms of asexual propagation are ubiquitous throughout the plant kingdom, especially in bryophytes, few time scales for exclusively clonal plants have been established. We have studied the biology, phylogenetic origin and timing of loss of sexual reproduction in the Southern Appalachian asexual hornwort Nothoceros aenigmaticus. Using a 5-locus matrix we reconstructed the phylogeny of Nothoceros, including samples from all recognized species (51 accessions). We have shown that the Appalachian lineage N. aenigmaticus originated in tropical alpine habitats; its closest relative is found in Mexican mountains. Our phylogeny suggests two independent dispersals to the Southern Appalachians of at least one male and one female spore, to produce the sex allopatry seen in extant populations. A maximum estimate of 1.5 MY for the male plants and 650,000 years for female plants suggests that N. aenigmaticus may have being without sexual reproduction since the Pleistocene. Our estimate represents one of the oldest reports of obligate asexuality in the plant kingdom. A comparison with current models explaining the phylogenetic twiggy pattern of asexuals throughout the Tree of Life is presented.
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1 - University of Connecticut, Ecology and Evolutionary Biology, 75 Northeagleville road, Storrs, CT, 06269-3043, USA
2 - University of Tennessee, Department of Botany, 437 Hesler Biology Bldg, 1406 Circle Drive, Knoxville, Tennessee, 37996-1100, USA
3 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 06269-3043, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 554A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 9:45 AM