Contrasting Forms of Competition Constrain Elevational Distribution of Species
Shih Fan Chan1, Wei Kai Shih2, An Yu Chang1,3, Dr. Sheng Feng Shen1, Dr. I Ching Chen2
1Biodiversity Research Center, Academia Sinica, Taipei, Taiwan, 2National Cheng Kung University , Tainan, Taiwam, 3Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan
The most influential hypothesis regarding species geographic limits suggests that abiotic factors constrain distribution boundaries of species in harsh environments, such as high elevation or high latitude, while inter-specific competition sets range boundaries at more benign environments. However, it has long been recognized—at least since Darwin’s On the Origin of species—that harsh climate strengthens competition enough to set species range limits. We show, for the first time, by a series of experimental manipulations, that temperature determined the types of competition and set the upper and lower elevational range limits of burying beetles (Nicrophorus nepalensis). The elevational distribution range of N. nepalensis is much wider than where it can reproduce successfully, representing sink populations at both limits. Blow flies are the beetle’s major competitors for their key breeding resource (carcasses). At the upper elevational limit, cool temperature inhibits the emission of carcass volatile and maggot development. The time required to locate the carcass determines their breeding success, representing typical exploitation competition. In contrast, at the lower elevational limit, direct interference competition dominants because higher temperature enables both species to detect and arrive at the carcasses quickly. The burying beetles struggle to exclude the rapid developing maggots to breed successfully. These different types of competition reflect Darwin’s classic hypothesis that a species’ geographic range limits is determined not by climate alone, but its effect on mediating biotic interactions.
Biography:
I-Ching’s work focuses on different aspects of biological responses to climate changes and habitat degradation, including species range shifts, the association with biological traits, and consequences of community reshuffling. Particularly, she concentrates on bird and butterfly species in the tropical mountains, where species may have adapted to the stable and cloudy environments but the ecosystems are vulnerable to a change in climate variability and diverse human activities.