Character displacement in the midst of background evolution in island populations of Anolis lizards: a spatiotemporal perspective.

Negative interactions between species can generate divergent selection that causes character displacement. However, other processes cause similar divergence. We use spatial and temporal replication across island populations ofAnolislizards to assess the importance of negative interactions in driving trait shifts. Previous work showed that the establishment ofAnolis sagreion islands drove residentAnolis carolinensisto perch higher and evolve larger toepads. To further test the interaction's causality and predictability, we resurveyed a subset of islands nine years later.Anolis sagreihad established on one island between surveys. We found thatA. carolinensison this island now perch higher and have larger toepads. However, toepad morphology change on this island was not distinct from shifts on six other islands whoseAnoliscommunity composition had not changed. Thus, the presence ofA. sagreionly partly explainsA. carolinensistrait variation across space and time. We also found thatA. carolinensison islands with previously establishedA. sagreinow perch higher than a decade ago, and that currentA. carolinensisperch height is correlated withA. sagreidensity. Our results suggest that character displacement likely interacts with other evolutionary processes in this system, and that temporal data are key to detecting such interactions.