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Abstract Detail


Hovick, Steve [1], Whitney, Kenneth [2].

Roles of propagule number and genetic diversity in colonization success and subsequent evolution of a ruderal species.

Colonization is a critical filter for most species, setting the stage for both short-term and long-term success. Increased propagule pressure (i.e., more founding individuals) usually enhances colonization success; however, this pattern may be driven by purely numeric effects, by population genetic diversity effects, or both. To determine the independent and interactive effects of propagule size and genetic diversity, we conducted a factorial seed addition experiment in the field in Texas, USA, using the ruderal mustard Arabidopsis thaliana. Our propagule size treatments spanned five levels, from 32 to 960 seeds per 0.25 m2 plot. These propagules were composed of one, four or eight genotypes, randomly selected from a pool of 25. All populations were exposed to ambient or reduced levels of interspecific competition, and monocultures of each genotype were included to quantify additive versus non-additive genetic diversity effects. Colonization success was assessed through three generations post-introduction. Evolutionary change in response to our treatments was determined by using genetic markers to quantify genotypic richness and the relative abundances of individual genotypes in our experimental populations over time.
Increasing propagule pressure enhanced realized genetic diversity over time and in both competitive environments. Increasing propagule pressure also had a strong positive influence on abundance immediately following introduction, particularly in plots where nutrient availability was the greatest and competition reduced. Lastly, greater propagule pressure increased the likelihood of population persistence through three generations. However, many of the largest populations initially experienced rapid declines over time, resulting in no relationship between seed inputs and third-generation abundance in populations that had not gone extinct. In low competition conditions, increased population genetic diversity enhanced the probability of persistence through the third generation, but genotypic mixture populations nevertheless fell significantly short of expectations based on performance of the component genotypes in monoculture (negative non-additive effects). In these low competition populations that persisted through the third generation, abundances fell with increased diversity, and negative non-additivity was apparent in our highest diversity treatment. Negative effects of genetic diversity, and perhaps the predominance of negative non-additive effects of genetic diversity, likely reflect the relative over-representation of poorly performing genotypes in our source pool. Our data show that genetic diversity effects can have offsetting positive and negative effects on colonization and help to clarify factors that can either enhance or buffer the positive effects of propagule pressure on colonization and subsequent evolution.

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1 - The Ohio State University, Dept. Of Evolution, Ecology & Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Avenue, Columbus, OH, 43210, United States
2 - University of New Mexico, Department of Biology, MSC03-2020, 219 Yale Blvd NE, 1 University of New Mexico, Albuquerque, NM, 87131

population genetics
Genetic diversity
propagule pressure
Biological invasion
population biology
Arabidopsis thaliana
recruitment curve.

Presentation Type: Oral Paper
Session: 31, Ecology Section - Population Biology
Location: 106/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 1:30 PM
Number: 31001
Abstract ID:585
Candidate for Awards:None

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