Abstract Detail

Reproductive Processes

Blake-Mahmud, Jennifer [1], Struwe, Lena [2].

Time for a change: patterns of sex expression, health, and mortality in striped maple (Acer pensylvanicum).

The ability of individuals to change sex during their lifetime is known as environmental sex determination (ESD). This represents a unique life history trait, allowing plants to allocate resources differentially to male and female functions across lifetimes, potentially maximizing fitness in response to changing environmental or internal cues. We investigated an often-cited example of ESD, Acer pensylvanicum, to see whether it conformed to theoretical predictions that females are larger and in better condition. We also explored whether sex correlates with growth and mortality. We documented patterns of sex expression over four years in populations located in New Jersey, USA and collected data on size, mortality, health, and growth. Using a machine-learning algorithm known as a boosted classification tree, we developed a model to predict the sex of a tree based on its previous sex, condition and size. In our study, more than 50% of the trees switched sex expression during a four-year period, with 26% of those trees switching sex at least twice. Consistently monoecious trees could change sex expression by as much as 95%. Size and condition were both important predictors of sex, with condition exerting three times more relative influence than size on expressed sex. Healthy trees are more likely to be male; female sex expression increases with decreasing health. Growth rate negatively correlates with multiple years of female sex expression. Populations maintain similar male-skewed sex ratios across years and locations and may result from differential mortality: 75% of dead trees flowered female immediately before death. In conclusion, our study shows for the first time that A. pensylvanicum strongly exhibits ESD and that femaleness correlates with individual-level factors in previously unsuspected ways. The mortality findings advance our understanding of puzzling non-equilibrium sex ratios and life history trade-offs resulting from male and female sex expression.

1 - Rutgers University, Ecology And Evolution Department, 14 College Farm Road, New Brunswick, NJ, 08901, United States
2 - Rutgers University, Ecology, Evolution, & Natural Resources, 237 Foran Hall, 59 Dudley Road, New Brunswick, NJ, 08901, United States

Keywords:
environmental sex determination
Plasticity
sex ratios
Sapindaceae
morality
plant reproduction
health
dioecy
Temperate trees
Acer
Machine Learning.

Presentation Type: Oral Paper
Session: 29, Reproductive Processes II
Location: 111/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 3:45 PM
Number: 29009
Abstract ID:492
Candidate for Awards:None