Guppies as heterospecific facilitators: a precursor of exploratory behavior?

Abstract

Behavior can explain population-level processes such as dispersal, yet connecting a specific behavioral phenomenon with a larger ecological pattern is often speculative rather than supported by experimental studies. We investigate how exploratory behavior may develop in the killifish, Rivulus hartii through association with another taxon, the guppy, Poecilia reticulata. We hypothesize that exploratory behavior is enhanced by nearby guppies, which embolden Rivulus to move along the river edge, through zones of high predation risk. We tested individual boldness in the presence of both guppies and conspecifics. We also tested for the effect of prior experience with guppies, comparing boldness in Rivulus from locations in which it was either allopatric to or sympatric with guppies. Guppies increased boldness in Rivulus, equivalent to the effect of conspecifics, and prior experience with guppies also increased boldness over that of inexperienced Rivulus. Sympatric Rivulus were shy compared with the allopatric ones when each was tested alone, but this relationship reversed when guppies were present, showing that boldness is a plastic trait that can be influenced by the population of origin. An experimental field-stream test showed that guppies increased movement of Rivulus under predation threat, supporting links in a conceptual framework that connects a behavioral phenomenon, exploratory boldness, with a larger ecological pattern, selection of favorable habitats that, in turn, can lead to increased reproduction and fitness relative to non-dispersers.