Duration of colonization and interactions between early and late colonists determine the effects of patch colonization history on patch biodiversity

Patches can vary in their colonization history as the result of many factors, including differences in patch size and isolation, which alter the timing and duration in which one or more species colonize a patch. Prior work has found that the particular time that a species colonizes a patch can affect the performance of co‐occurring species, but it is less clear whether it affects the biodiversity of the patch. Our objective was to evaluate how two components of colonization history affect biodiversity – the total duration of the colonization window in which a predator is able to colonize the patch and the particular time in the patch's colonization history (i.e. early versus late in community development) that colonization by a predator occurs. We conducted an experiment to examine how the duration and timing in which predatory dragonflies colonize recently filled ephemeral ponds affects insect biodiversity. Dragonfly colonization history had an important effect on insect biodiversity. Ponds with a longer colonization history by dragonflies had fewer insect morphotypes than ponds with a shorter colonization history. The timing of dragonfly colonization (i.e. early versus late in community development) had no effect on the number of insect morphotypes present despite altering both the rate of dragonfly metamorph production and the abundance of larval dragonflies present at the end of the study. The effect of duration of long‐term dragonfly colonization on biodiversity stemmed from early colonists weakening the influence of later colonists on insect biodiversity. Though colonization by dragonflies reduced adult insect abundance, differences in the time in which dragonflies colonized ponds had no effect on total insect abundance. Moreover, differences in patch biodiversity appears to be affected more by variation in the duration a patch was colonized by a predator than variation in the time in which a patch was colonized by a predator.