January American Naturalist highlights

"Nontrophic interactions, biodiversity, and ecosystem functioning: an interaction web model"
Alexandra Goudard (Ecole Normale Supérieure and Université Pierre et Marie Curie) and Michel Loreau (McGill University)

Most ecological theories deal with simple consumer–resource interactions. Scientists at Ecole Normale Supérieure (Paris) and McGill University provide a novel approach to incorporate nontrophic interactions, such as pollination and habitat modification, in ecosystem models, which allows them to study the dynamics of complex interaction webs.

Their model adds nontrophic interactions to a food web in the form of modifications of trophic interactions. It also tracks nutrient fluxes in the food web and hence satisfies the principle of mass conservation. Using this model, they show that nontrophic interactions can profoundly influence ecosystem properties such as species diversity, biomass, and production. In turn, the nature, prevalence, and strength of species interactions depend on species diversity. Counterintuitively, strong positive interactions tend to deteriorate ecosystem functioning because consumers become very efficient at exploiting their resources. "Nontrophic interactions are still poorly studied theoretically, and their impact on biodiversity and ecosystem functioning was largely unknown," says Michel Loreau, Canada Research Chair in theoretical ecology. "We hope that our new approach will boost their study and contribute to a more comprehensive theory of complex ecological systems. Organisms interact in many other ways than through feeding on each other or competing for shared resources," he adds. "Ecology should be able to account, not only for the diversity of species, but also for the diversity of their interactions."

"Mating frequency and inclusive fitness in Drosophila melanogaster"
Nicholas K. Priest (University of Virginia and Indiana University), Laura F. Galloway (University of Virginia), and Deborah A. Roach (University of Virginia)

Sexual conflict resolution?

In the gene’s eye view, female mating frequency is difficult to understand. A substantial body of evidence, taken throughout the animal kingdom, demonstrates that females mate frequently, even when bouts of mating decrease offspring production. This finding is counterintuitive because we would expect natural selection to remove mating behaviors which decrease fitness. However, new research suggests that frequent mating females receive fitness benefits from an unexpected source: their daughters. Evolutionary Biologists from the University of Virginia – Nick Priest, Laura Galloway and Deborah Roach – manipulated the mating frequency of female fruit flies, Drosophila melanogaster, and observed how mating frequency affected the lifetime reproductive output of those females and their daughters. They found that frequent mating decreased maternal survival and reproductive output, but increased the reproductive output of daughters.