Sex-Related Differences in Reproductive Allocation, Growth, Defense and Herbivory in Three Dioecious Neotropical Palms

Abstract

BackgroundFrequently, in dioecious plants, female plants allocate more resources to reproduction than male plants. Therefore it is expected that asymmetrical allocation to reproduction may lead to a reproduction-growth tradeoff, whereby female plants grow less than male plants, but invest more in defenses and thus experience lower herbivory than male plants.Methodology/Principal FindingsWe tested these expectations by comparing resource allocation to reproduction, growth and defense and its consequences on herbivory in three sympatric dioecious Chamaedorea palms (C. alternans, C. pinnatifrons and C. ernesti-augusti) using a pair-wise design (replicated male/female neighboring plants) in a Mexican tropical rain forest. Our findings support the predictions. Biomass allocation to reproduction in C. pinnatifrons was 3-times higher in female than male plants, consistent with what is known in C. alternans and C. ernesti-augusti. Growth (height and leaf production rate and biomass production) was higher in male plants of all three species. Female plants of the three species had traits that suggest greater investment in defense, as they had 4–16% tougher leaves, and 8–18% higher total phenolic compounds concentration. Accordingly, female plants sustained 53–78% lower standing herbivory and 49–87% lower herbivory rates than male plants.Conclusions/SignificanceOur results suggests that resource allocation to reproduction in the studied palms is more costly to female plants and this leads to predictable intersexual differences in growth, defense and herbivory. We conclude that resource allocation to reproduction in plants can have important consequences that influence their interaction with herbivores. Since herbivory is recognized as an important selective force in plants, these results are of significance to our understanding of plant defense evolution.

Relative effects of genetic variation sensu lato and sexual dimorphism on plant traits and associated arthropod communities

“…Our findings partially support previous thinking about dioecy effects on plant traits and arthropod communities. Theory predicts that, due to tradeoffs between growth, reproduction, and defense, female plants invest more energy in reproduction and in defensive traits (lower herbivory) and in turn tend to exhibit decreased growth relative to male plants (Cox 1982;Cornelissen and Stiling 2005;Cepeda-Cornejo and Dirzo 2010). Supporting this hypothesis, we found that female B. salicifolia plants produced more flowers than male plants.…”

Changes in sex ratios of a dioecious grass with grazing intensity: the interplay between gender traits, neighbour interactions and spatial patterns

“…As proposed by theory on dioecious species (Delph 1999;Geber, Dawson & Delph 1999;Obeso 2002;Cepeda-Cornejo & Dirzo 2010), Poa genders were dimorphic in traits related to resource allocation. As predicted (Prediction 1), females had lower vegetative growth rates (Table 1) but they were better defended against herbivores than males.…”

“…We also hypothesize that those differences in traits determine, indirectly, their interaction with domestic herbivores. The predictions were the following: 1 Females will have lower vegetative growth than males (Lloyd & Webb 1977;Obeso 2002), will also be better defended than males, and hence less preferred by natural herbivores (Coley, Bryant & Chapin 1985;Jing & Coley 1990;Herms & Mattson 1992;Cepeda-Cornejo & Dirzo 2010). 2 Female biomass will be more negatively affected by the competition with other grass species than males because of slower female growth and higher reproductive requirements (Lloyd & Webb 1977).…”

Disturbance and Resilience in Tropical American Palm Populations and Communities

“…Mauritiinae, Ceroxyleae). Dioecy implies different strategies of resource allocation depending on the sex of the plant, and consequently differential selective effects on male and female plants (Cepeda-Cornejo & Dirzo, 2010). Arecoideae is the most diverse palm subfamily in tropical America with 39 genera, mostly monoecious, with the exception of the dioecious Chamaedorea and Wendlandiella.…”