1 Citation 312 Views 21 Downloads
PREMISE OF THE STUDY: Bet-hedging strategies maximize long-term geometric
fitness at the cost of reduced arithmetic fitness by offsetting different
mortality risks. Heterocarpic systems accomplish bet-hedging through the
production of two or more fruit types that vary in dormancy and dispersal
ability. It is unknown whether heterocarpy also offsets predispersal
mortality risks. To address this question, we investigated whether
heterocarpy in Grindelia ciliata (Asteraceae) also offsets mortality risks
posed by a seed predator Schinia mortua (Noctuidae) to increase plant
fitness. METHODS: We conducted two manipulative experiments to quantify
critical life history components of this plant–insect interaction. We
measured predispersal achene mortality from herbivory, postdispersal
achene mortality in the seed bank, and seedling emergence. These
measurements were then used in deterministic models to evaluate
evolutionary consequences of predispersal seed mortality in G. ciliata.
KEY RESULTS: Dormant achene types were less vulnerable to herbivory but
more susceptible to mortality in the seed bank due to delayed seed
emergence. Nondormant achene types experienced high predispersal mortality
but low seed bank mortality due to rapid germination. Our
herbivore-dependent model improved fit between observed and expected
proportions of dormant and nondormant G. ciliata achenes and showed that
heterocarpy could evolve in the absence of postgermination mortality.
CONCLUSIONS: Our study provides empirical support of how predispersal
herbivory can be equally important to postdispersal seed mortality risks
in the evolution and maintenance of a heterocarpic reproductive system and
expands understanding of how bet-hedging theory can be used to understand
this unique reproductive strategy.
312 views reported since publication in 2017.