Ignorance is not bliss: Evolutionary naïveté in an endangered desert fish and implications for conservation
Creators
- 1. North Dakota State University
- 2. Minnesota State University, Mankato
Description
Predator naiveté has been invoked to explain the impacts of non-native predators on isolated populations that evolved with limited predation. Such impacts have been repeatedly observed for the endangered Pahrump poolfish, Empetrichthys latos, a desert fish species that evolved in isolation since the end of the Pleistocene. We tested Pahrump poolfish anti-predator responses to conspecific chemical alarm cues released from damaged epidermal tissue in terms of fish activity and water column position. Pahrump poolfish behavioural responses to conspecific alarm cues did not differ from responses to a dechlorinated tap water control. As a positive control, the well-studied fathead minnow, Pimephales promelas, showed significant alarm cue responses in terms of reduced activity and lowered water column position. The density of epidermal club cells, the presumptive source of alarm cues, was significantly lower in Pahrump poolfish relative to fathead minnows. Therefore, anti-predator competence mediated by conspecific alarm cues does not seem to be a component of the ecology of Pahrump poolfish. These findings provide a proximate mechanism for the vulnerability of Pahrump poolfish to non-native predators, with implications for conservation and management of insular species.
Notes
For poolfish behavioral data, the analyses were conducted on a) full data set and b) on a reduced dataset that included only fish with pre-stimulus activities levels that were greater than 50 lines and less than 400 lines. Also, one fish that showed jerky movements was not included in the reduced data set.
For fathead behavioral data, all 30 trials met the criteria described above.
For the histology data, we used a permutation procedure to analyse data as described in Methods.