COS 96-5 - Seedling emergence, but not survival, is associated with maternal mating opportunity

Tuesday, August 16, 2022

2:30 PM – 2:45 PM EDT

Presenting Author(s)

AW

Amy Waananen

Department of Ecology, Evolution, and Behavior, University of Minnesota, United States

Coauthor(s)

LR

Lea K. Richardson

Program in Plant Biology and Conservation, Northwestern University; Negaunee Institute for Plant Conservation Science and Action at the Chicago Botanic Garden
Glencoe, IL, United States
SN

Scott W. Nordstrom

Graduate Student
Department of Ecology and Evolutionary Biology, University of Colorado Boulder, United States
RT

Riley D. Thoen

Department of Plant Biology, University of Georgia, United States
EE

Erin E. Eichenberger

North Carolina State University, United States
AD

Amy B. Dykstra

Department of Biological Sciences, Bethel University, United States
RS

Ruth G. Shaw

Department of Ecology, Evolution, and Behavior, University of Minnesota, United States
SW

Stuart Wagenius

Negaunee Institute for Plant Conservation Science and Action at the Chicago Botanic Garden, United States

Background/Question/Methods

In plant population biology, the assumption that fecundity (e.g., seed yield) is a reliable proxy for reproductive success often goes unquestioned. However, parental fecundity might not correspond to offspring survival. As a result, fitness estimates derived from fecundity may overestimate fitness. Furthermore, fecundity and survival might respond differently to biotic or abiotic aspects of the environment (e.g., conspecific density) in magnitude or direction. One important factor that may influence reproductive success through effects on both fecundity and offspring survival is mating opportunity, or the abundance and proximity of an individual’s potential mates. In this study, we investigate how mating opportunity affects maternal fecundity and survival of the resulting offspring in 14 isolated populations of a long-lived prairie forb, Echinacea angustifolia. Across seven years (2006-2013), we evaluated the annual mating opportunity of 1278 flowering individuals. The following spring, we found the progeny as seedlings and assessed their survival and growth annually for 8 years. We used aster models to evaluate the relationship of mating opportunity with the initial number of seedlings emerging as well as the number of progeny alive after 8 years.

Results/Conclusions

Maternal mating opportunity was associated with increased seedling production. However, of 914 seedlings that we found and tracked, only 98 survived to age 8. After eight years, we did not detect any effects of mating opportunity on the number of surviving progeny; low juvenile survival largely erased initial differences in offspring counts between maternal plants. These results suggest that mating opportunity increases counts of emerging progeny, but does not have a detectable effect on fitness beyond initial emergence. The findings from this work clarify interpretation of previous studies, which use fecundity as a basis for making projections about individual fitness or population growth. Specifically, our study demonstrates how fecundity-based measures overestimate fitness and fitness differences. Our results also show that the factors that govern juvenile survival play a large role in determining reproductive fitness; future research to characterize these factors will help clarify the evolutionary and demographic consequences of mating opportunity and its effect on seedling production. Future study to investigate how components of fitness across individuals’ lifespans co-vary in response to mating opportunity and other factors will clarify appropriate approaches to account for individual’s fitness and interpret the consequences of selection on any one fitness component.