Simulated extreme climate event alters a plant-frugivore mutualism

Abstract

Anthropogenic climate change is contributing to an increase in the frequency of extreme weather events. These extreme events may affect interactions in mutualisms that provide key ecosystem functions, especially when the event is rare for a given system and participants are differentially affected. The tropical hardwood hammocks of Key Largo, Florida, USA are inhabited by a highly specialized endangered rodent, the Key Largo woodrat (Neotoma floridana smalli), which may be an important seed disperser of many native fleshy-fruited plant species. Other potential mammalian dispersers are generalist omnivores, northern raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana), that are less selective. We sought to demonstrate that extreme climate events could alter seed dispersal mutualisms by differentially affecting fruit preference of potential dispersers. We designed a replicated cafeteria-style experiment across the entire range of the Key Largo woodrat with fruit from sixteen native plant species and simulated an extreme climate event by exposing half of the fruits to sub-freezing temperatures. Freezing temperatures are rare in this tropical environment, but increased frequencies of these types of extreme events are predicted with climate change. Using camera traps, we monitored the removal of fruit and seeds by woodrats and the generalist consumers, predicting that changes in fruit quality resulting from exposure to sub-freezing temperatures would reduce preference by the more specialized woodrat relative to its generalist consumers. Indeed, exposure to subfreezing temperatures decreased the probability of fruit and seed removal by woodrats while generalist consumers preferentially removed more of the fruits and seeds exposed to sub-freezing temperatures. These data provide evidence that extreme climate events may affect species preferences for food asymmetrically, which may shift the dynamics of seed dispersal mutualisms. Over time, increasing frequencies of extreme weather events could indirectly affect communities and ecosystem services by shifting interactions between organisms.