Jonathan Aguinaga

UC Davis

“Information takers and makers: behavioral variation binds mixed-species groups together”

Mixed-species groups are common in nature, but why they are so widespread remains unclear. One hypothesis is that mixed-species groups provide increased information for decision-making compared to single-species groups. The behavioral variation exhibited in mixed-species groups could be a critical driver for their formation and maintenance. Here, we test for species- and individual-level behavioral variation between two closely related fish species that co-occur in nature: the clonal Amazon (Poecilia formosa) and Atlantic mollies (Poecilia Mexicana). We test individual fish in repeated trials of an open space novel foraging task while in the presence of a control, conspecific, or predator treatment. We use automated tracking to measure key behaviors such as swimming velocity, foraging success, refuge use, sociability, and predator inspection. We find that Amazon mollies are more active and exploratory, can find foraging opportunities more quickly, but investigate conspecifics and predators less often than Atlantics. These behavioral differences suggest that these species collect and use information differently, and potentially explains their frequent co-occurrence in nature and an advantage to mixed-species grouping more broadly.


Mixed-species groups are common in nature, but why they are so widespread is not well understood. One explanation is that within- and between-species behavioral variation can be a critical driver in the formation and maintenance of such mixed-species groups. Here, I evaluate the extent of within- and between-species differences in behavior between a clonal and sexually reproducing pair of fish that co-exist in the wild.

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