Evolution in a Glaciated Landscape: Contribution of Endemism to Great Lakes Biodiversity
Reznicek, Anton A. .
Through a Glass Darkly – Development of Great Lakes Vegetation Occupied by Endemic Plants.
The re-vegetation of the Great Lakes landscape and the evolution of our flora after deglaciation are well known. From pollen records, tree migration has been well documented, and the tempo of the re-foresting of the landscape is clear. However, the evolution of non-forest communities in the matrix is much less well understood. They occupy small areas, harbor small populations, and are poorly sampled by pollen. Many of the biogeographically interesting elements of the flora – most of the disjuncts and almost all of the endemics – are not forest plants. The endemics in particular occur primarily on dunes, beaches, alvars (glaciated limestone pavements), and even fens. Understanding the origin and development of these communities is important for understanding the evolution of endemics and disjuncts, even though it is clear that different elements in a community may differ in their history. While the patterns of re-vegetation of the landscape are controlled by macroclimate and the configuration of the Great Lakes, more important to the endemics are the local controls of topography, microclimate, hydrology, and substrate. Unlike forests, analogs of these open habitats were present in some form immediately or soon after deglaciation and occupied a greater area than at present. Some of these habitats have been continuously available in time (if not in space) since deglaciation. They can thus offer refuge for relicts of earlier stages in the revegetation process, and their dynamics provide insight into the drivers of evolution of endemics. They act as a murky window into the past. Due to the different macroclimates in the past, plant communities immediately after deglaciation probably have no precise homologs in the present, but despite this, many of the topographical, hydrological and soil conditions are available in specialized microsites in the present day communities, especially rocky and, to a lesser extent, sandy shorelines.
Log in to add this item to your schedule
1 - University of Michigan, University Herbarium, 3600 Varsity Drive, Ann Arbor, Michigan, 48108, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Boulevard A/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:30 AM