Abstract Detail


Sullivan, Lauren [1], Portlas, Zoe [2], Hamilton, Jill [3].

Evolution of dispersal across a discontinuous landscape.

The evolution of dispersal has major implications to the maintenance of landscape connectivity and gene flow across a species' range. In continuous landscapes, selection for increased dispersal may be favored, promoting movement of individuals to unoccupied habitats, thus decreasing the degree of local competition. With increased dispersal ability individuals may reach favorable habitats during range expansion and colonization. In contrast, when habitats are discontinuous or fragmented, decreased dispersal ability may be favored. This may be particularly true for wind-dispersed species isolated in a matrix of unfavorable habitats as dispersal beyond favorable habitat boundaries may reduce opportunities for growth and reproduction. Thus, historical colonization and contemporary fragmentation have likely played a strong role in the evolution of dispersal and population connectivity. In this study, we use Geum triflorum (Pursh.) as a model to determine how dispersal traits vary across a species' range that includes both continuous and isolated populations. G. triflorum, an herbaceous perennial characteristic of midwestern prairies, has a distinctive trio of flowers that develop multiple achenes, each with a densely wooly style that remain intact during dispersal. These styles are presumed to promote wind dispersal, by increasing the time-aloft for seeds after release from the maternal plant. Over multiple years we sampled individual maternal plants from across the range of G. triflorum. This included once continuous, but contemporarily fragmented midwestern prairies and historically isolated, disjunct populations found across Great Lakes alvar habitats. We ask how does population isolation alter morphological variation in seed mass, shape, and terminal velocity of this wind-dispersed species. Both dispersule (seed plus style) and seed mass differed significantly between regions, with individuals in prairies having heavier mass than those in the alvars (p = 0.01, p < 0.0001 respectively).  Additionally, style length tended to be significantly longer in the alvar regions as compared to the prairie (p < 0.0001). Taken together, this indicates that populations of G. triflorum from the historically isolated alvar habitats are likely to disperse farther given their seeds are smaller and have longer dispersal structures which can increase the time aloft. These results suggest that the dispersal ability of alvar populations may still exhibit evidence of patterns driven by initial long-distance dispersal and colonization, rather than contemporary geographic isolation.  This research will not only inform conservation efforts of G. triflorum, but will also apply to species of conservation interest in other fragmented or isolated environments.

1 - University of Minnesota, Ecology, Evolution and Behavior, 1987 Upper Buford Circle, St. Paul, MN, 55108, USA
2 - North Dakota State University, Biological Sciences, PO Box 6050, Dept 2715, Fargo, ND, 58102, USA
3 - North Dakota State University, Biological Sciences, PO Box 6050, Dept. 2715, Fargo, ND, 58102, United States

seed dispersal
terminal velocity
disjunct populations.

Presentation Type: Oral Paper
Number: 0011
Abstract ID:412
Candidate for Awards:None

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