Abstract Detail


Quarles, Brandie [1], Donohue, Kathleen [2].

Demographic Consequences of Phenological Tracking.

Phenological tracking, when species use environmental cues to shift the timing of developmental events to match seasonal environments more favorable for survival and reproduction, has been shown to be important for species persistence in response to climate change. Phenological tracking via germination time regulation may be especially impactful since germination time determines the environmental conditions that a plant will experience throughout the life cycle. Plants can control their germination timing by entering dormancy to delay growth within-years (phenological tracking) or between-years (seed banking). Both forms of seed dormancy can stabilize population sizes across time.
I assessed 1) how seed dormancy evolves in response to various environmental conditions, 2) the demographic effects of dormancy with respect to a) population size, b) population fitness, c) above-ground population persistence, and d) fluctuations in population size, and 3) how the demographic effects of dormancy change in response to different environmental conditions. To this end, I established 112 genetically variable experimental populations of Arabidopsis thaliana in the field with about 620 seeds from one of three recombinant inbred line sets (RIL sets) that differed at 2-3 major dormancy loci. I imposed environmental manipulations of soil composition, temperature, and moisture conditions. 48 “Mixed” populations were composed of both dormant and non-dormant genetic lines to investigate the evolution of dormancy itself during the experiment. I monitored environmental conditions, germination timing, population size, and population persistence for 3 years. I also measured individual traits for 2 years (over-wintering size, size at reproduction, height of flowering stalk, branch number, and fruit number).
So far, I have verified that the experimental dormancy treatment had detectable germination time effects under field conditions in year 1. Further, dormancy influenced demography and population persistence primarily via early seedling mortality and the effect of dormancy accumulated over time. Dormant populations had larger seedling populations and higher population persistence over the three years. In addition, the effects of dormancy and the environment depend on each other. For example, environmental treatment influenced population persistence only in Non-Dormant populations, and environmental effects on fecundity depended on whether populations were Dormant. Thus, for some demographic metrics, dormancy mitigates the demographic effects of environmental variation. Overall, these results suggest that phenological tracking via seed dormancy can have beneficial effects on population demography. Also, the more consistent above-ground populations that arise due to high dormancy, may increase the opportunity for selection on other traits. This will be beneficial as phenological tracking alone, may not be sufficient for populations/species to respond to climate change.

1 - Duke University, Biology Department, Room 137, Biological Sciences Building, 130 Science Drive, Durham, NC, 27708, United States
2 - Duke University, Dept Of Biology, Box 90338, Durham, NC, 27708, United States

Seed dormancy
Phenological tracking
Habitat selection.

Presentation Type: Oral Paper
Number: EC06007
Abstract ID:592
Candidate for Awards:Ecological Section Best Graduate Student Paper

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