Ignorance is not bliss: evolutionary naiveté in an endangered desert fish and implications for conservation

Abstract

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 the conservation and management of insular species.

Ring a bell? Variable recognition of a multicomponent auditory stimulus associated with predation risk by zebrafish responding to full and partial matches

“…Conversely, a predator-recognition window that is too conservative may lead prey to fail to respond to a predator that poses real and imminent danger. For example, invasive predators can benefit from being outside of the generalized predator window of native prey (Goodchild & Stockwell, 2016;Anton et al, 2016Anton et al, , 2020Carthey & Blumstein, 2018;Melotto et al, 2020;Stockwell et al, 2022). Similarly, prey can adjust response intensity to the strength of alarm cue or perception of risk represented by test stimuli (Mirza & Chivers, 2003, Mirza et al, 2006.…”

Commentary: using prey naïveté to inform ecological management

“…Second, prey populations with successful antipredator mechanisms may also evolve naïveté when a predator disappears from a predator–prey interaction (i.e. secondary naïveté ), as postulated by Stockwell et al [1]. Many antipredator mechanisms are costly to maintain thus, naïveté can provide a short-term fitness advantage in the absence of a predator, allowing selection for naïveté [14].…”

“…Stockwell et al . [1] tell the unfortunate story of the pahrump poolfish ( Empetrichthys latos ). The poolfish—a relic of historically larger lakes in the American southwest—is threatened by several novel predators and larvivores.…”

“…We believe that, read correctly, the work of Stockwell et al . [1] should serve both as a warning sign and a source of inspiration for managers, particularly those of aquatic systems. It should serve as a warning sign, because—as we argue below—novel interactions between introduced predators and naïve prey are likely to increase in frequency during the Anthropocene.…”

Acquired predator recognition via epidermal alarm cues but not dietary alarm cues by isolated pupfish

“…Recently, we reported a case of predator naiveté to conspecific olfactory cues in the Pahrump poolfish (Empetrichthys latos) [17]. This endangered species, which has been severely impacted by non-native predators [18][19][20], showed no behavioural response to conspecific epidermal alarm cues [17]. This is a unique case of predator naiveté because Pahrump poolfish lack the olfactoral ability to detect and avoid predation events.…”