Presentation Detail

Evolution in Response to Anthropogenic Change

Wadgymar, Susana M. [1], Gilbert, Benjamin [2], Cumming, Matthew N. [3], Tucker, Caroline M. [4], Cadotte, Marc W. [4], Weis, Arthur E. [1].

Hot, crowded, and unfriendly: disentangling the direct and indirect effects of warming and competition on phenology, growth, and fitness.

Climate change has influenced patterns of growth and phenology in many plant species. The adaptive nature of life history traits suggests that any warming-induced plasticity is likely to influence patterns of selection. However, competitive interactions can also influence the expression of these traits, and studies examining responses to climate change have not typically accounted for variation in the competitive environment. Selection for specific traits may be weaker or stronger in the presence of competitors, depending on common responses to warming cues. For example, selection for earlier flowering onset with warming may be dampened when a competitor species has an earlier phenology, or alternately be heightened when a competitor has a later phenology. This potential for competitive interactions to alter the selective regimes imposed by warming remains unexplored.
We manipulated competitive and thermal regimes for 3 temperate annual plant species: Sinapis arvensis (early flowering), Chamaecrista fasciculata (intermediate flowering) and Ambrosia artemisiifolia (late flowering). Each species was planted in high and low density monocultures as well as in polycultures that included all three species. These communities were then either artificially warmed via infra red heating or exposed to ambient temperatures. Seed production was measured for each individual and selection on flowering phenology (a temperature-sensitive trait) and plant size (a trait representative of competitive ability) was estimated in each environment.
The effect of warming on patterns of selection depended on the species considered and the competitive environment. For the early-flowering species, ambient temperatures produced selection for early flowering in all competitive environments except low density monocultures. Warmer temperatures consistently dampened the strength of selection in this species. For the intermediate flowering species, early-flowering individuals only had higher fitness when grown among conspecifics, and in warmed treatments this effect was only apparent at low densities. Directional selection for larger plant size was significant for all species in all treatments but was stronger in monoculture plots for early and late species and strongest in polyculture plots for the intermediate species.
These results suggest that the effects of increased temperature and competition on a species may depend on its position within the developmental sequence of a community. Specifically, species with intermediate flowering times face competition from early and later developing species, and this produces a constraint on selection for flowering time. Over time, this may lead to altered competitive dynamics that can act synergistically with the direct effects of global warming.

1 - University of Toronto, Department of Ecology and Evolutionary Biology, 25 Willcocks St. , Toronto, ON, M5S3B9, Canada
2 - University of Toronto , Department of Ecology and Evolutionary Biology, 25 Harbord St., Toronto, ON, M5S3G5, Canada
3 - University of Toronto, Department of Ecology and Evolutionary Biology, Weis Lab, 25 Willcocks St., Toronto, ON, M5S3B9, Canada
4 - University of Toronto - Scarborough, Department of Biological Sciences, 1265 Military Trail, Toronto, ON, M1C1A4, Canada

Keywords:
plasticity
selection
flowering time
artificial warming
Climate Change
Competition
plant size.

Presentation Type: Regular Oral Presentation
Session: 32
Location: Rendezvous B/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 2:00 PM
Number: 32003
Abstract ID:665
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation