Similar species that co-occur in an ecosystem may reduce competition by concentrating their activity at different times, in different places, or both. Writing in Oikos, Bouinier and colleagues investigated spatial and temporal niche partitioning in Amazonian butterflies of the Morpho genus. In the first phase of the study, they sampled males of nine species in a rainforest site in French Guiana to record their hourly activity; they then subjected individuals of all species to thermal tolerance tests in the laboratory, including their recovery from cold and hot ‘knock-out’ stress. In the field, the species reduce their overlap by preferring both different times of the day and different vertical layers. Notably, even two distinctly coloured morphs of one species tend to be active at different times. There was up to 5 °C difference in the temperatures of the time windows preferred by distinct species, and yet there were no clear correlations between activity time and thermal traits. However, butterflies that are more active in the canopy were more heat tolerant than those that are more active in the understory, whereas the latter were more cold tolerant. These findings thus suggest differences in thermal traits as a mechanism that enables the vertical stratification of co-occurring butterfly species, but not necessarily their temporal segregation, which the authors speculate is the result of interspecific interactions. The study thus showcases both the power and the limits of physiological ecology in explaining niche partitioning among species.
Original reference: Oikos https://doi.org/10.1002/oik.11567 (2025)
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