Symposium: “Macroecology of sexual selection: a predictive conceptual framework for large-scale variation in reproductive traits”

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Glauco Machado, Bruno A. Buzatto, Solimary García-Hernández, and Rogelio Macías-Ordóñez

Is sex hotter is hot climates?

A mating pair of the North American harvestman Leiobunum vittatum. In northern cold climates with short breeding seasons, males chase females. In southern warmer climates, males defend reproductive territories.
(Credit: John R. Maxwell)

The exuberant variety of animal life forms in the tropics, with their many sounds, smells, and colors, have lured naturalists for centuries. Considering that these traits are mainly used to attract mating partners, one may ask whether sexual interactions are stronger in warm climates. Until some years ago, researchers were unable to answer this question because information on sexual behavior of many species was widely scattered in the scientific literature, and because large datasets on climate were unavailable. The growing interest on global warming and data widely available on the internet circumvented these limitations and created the opportunity to investigate links between climate and sexual interactions.

Two males of the South American harvestman Serracutisoma proximum fighting for the possession of a reproductive territory on the vegetation. In this species, males are armed with spines on their legs.
(Credit: Bruno A. Buzatto)

In a new paper appearing in The American Naturalist, researchers from Brazil, Colombia, and Mexico explore how temperature and rainfall influence the reproductive strategies of a group of arachnids commonly known as harvestmen or daddy-longlegs. They show that species living in warm and humid places have longer breeding seasons than species living in cold and dry places. They also show that the time devoted to reproduction may affect mating behavior. Males in areas with long breeding seasons attract females by establishing reproductive territories that are defended with extravagant weaponry. On the other hand, short breeding seasons are associated with weaponless males that simply chase females. In a fast-changing world, it is imperative to understand how reproduction―a key process in the life of any organism―can be affected by the climate warming. The authors conclude that when the climate gets hotter, aggressive interactions between males for access to females are fiercer.