Systematics/Phytogeography / Taxonomie/ Section
Peirson, J. A. .
Ecological and Phenological Divergence of Solidago simplex Populations in the Glaciated Great Lakes Region: Implications for Reproductive Isolation and Speciation.
Many plant species harbor substantial amounts of range-wide morphological and phenological variation. This population-level variation has often been attributed to local differences in environmental conditions and to broad clinal variation in rainfall and the length of the growing season. Relatively few studies, however, have examined this type of variation in the context of ecological (habitat) divergence and its potential effects on reproductive isolation and speciation, especially in lowland glaciated regions. Data from three primary sources (historical data from herbarium specimens, field data from natural populations, and common garden data) were used to examine population-level differences in ecology and flowering phenology in Solidago simplex across its disjunct range in the glaciated Great Lakes region. Herbarium and field data indicate that S. simplex populations are restricted to four distinct, allopatric habitats in the region: dolomite and granite/basalt outcrops, sand dunes, and xeric Jack Pine barrens. Herbarium and field data also reveal that populations in these habitats have markedly divergent flowering phenologies, with pine barren and rock outcrop populations flowering early (late June to early August). Geographically proximal (within 80 km) pine barren and sand dune populations have consistently non-overlapping flowering periods and also differ in a number of morphological traits. These phenological and morphological differences are maintained in the common garden. The patterns of variation uncovered in this study differ somewhat from earlier taxonomic work on S. simplex, and the stark ecogeographic, morphological, and phenological differences among Great Lakes region populations suggest that these ecological varieties are likely distinct, reproductively isolated species. Similar patterns of divergence in Great Lakes region populations of S. hispida (with specialized rock outcrop and sand dune taxa) and S. speciosa (with an early-flowering pine barren taxon) support the hypothesis that adaptation to specialized habitats has been an important evolutionary force in this recently glaciated environment.
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1 - University of Michigan, Department of Ecology & Evolutionary Biology, 830 North University Avenue, Ann Arbor, Michigan, 48109-1048, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM