Temperature-dependent competitive outcomes between the fruit flies Drosophila santomea and D. yakuba

We use these data to test whether temperature can indirectly affect the
fitness of Drosophila santomea and D. yakuba by altering interspecific
competitive outcomes. We show that, when raised in isolation, both D.
santomea and D. yakuba display similar variation in relative fitness
across temperatures of 18°C, 22°C, and 25°C. However, D. santomea has
higher fitness than D. yakuba when experiencing interspecific competition
at 18°C, while the inverse is true at 25°C. Patterns of fitness across
thermal and competitive environments therefore indicate that the outcome
of interspecific competition varies with temperature. We then use a
‘coexistence’ experiment to show that D. santomea is rapidly (within 8
generations) extirpated when maintained with D. yakuba at 25°C. By
contrast, D. santomea remains as (or more) abundant than D. yakuba over
the course of ~10 generations when maintained at 18°C. Results provide an
example of how the thermal environment can affect interspecific
competition and suggest that some species may become more prone to
extinction under scenarios of climate change through indirect effects of
the thermal environment on competitive advantages between species.