Abstract
Introduced species represent one of the most serious global threats to biodiversity. In this field-based study, we assessed behavioural responses of brood tending cichlid fish to an invasive predator of their offspring. This was achieved by comparing parental defence responses of the endangered arrow cichlid (Amphilophus zaliosus), a fish species endemic to the crater lake Apoyo in Nicaragua, towards the bigmouth sleeper (Gobiomorus dormitor), a formidable predator of cichlid fry, and all other potential fish predators of offspring. The bigmouth sleeper was recently introduced into Apoyo but naturally co-exists with cichlids in a few other Nicaraguan lakes. Arrow cichlid parents allowed bigmouth sleepers to advance much closer to their fry than other predators before initiating aggressive brood defence behaviours. Interestingly, parents of a very closely related species, A. sagittae, which has coevolved with bigmouth sleepers in crater lake Xiloá, reacted to approaching bigmouth sleepers at comparable distances as to other predators of cichlid fry. These results provide a novel demonstration of the specific mechanism (i.e. naive parental behaviour) by which invasive predators may negatively affect species that lack the adequate behavioural repertoire.
Highlights
Introduced species that have subsequently become abundant in their new habitats are considered to be one the leading global threats to biodiversity [1,2], with ample evidence suggesting that freshwater ecosystems may be especially susceptible to the influence of species introductions [3,4,5]
During the 15-minute observation periods, 25 A. zaliosus and 18 A. sagittae broods were approached by both bigmouth sleepers as well as other potential offspring predators, allowing paired comparison between the two predator groups
Compared with native fish predators, the non-native bigmouth sleepers were able to approach the broods of A. zaliosus closer before they were chased away
Summary
Introduced species that have subsequently become abundant in their new habitats (often called ‘invasive species’) are considered to be one the leading global threats to biodiversity [1,2], with ample evidence suggesting that freshwater ecosystems may be especially susceptible to the influence of species introductions [3,4,5] This pattern may be due to lack of coevolution among prey and novel predators in many freshwater systems: to avoid native predators, prey organisms typically display particular behaviours (reviewed by [6,7]) that may be inappropriate or ineffective when dealing with novel invaders. The same assessment was conducted for another species within the Midas cichlid complex, A. sagittae, that has coevolved in sympatry with bigmouth sleepers in Xiloa This natural experiment allowed us to investigate the consequences of novel predation pressure in terms of adjustment of brood defence behaviours and to assess the potential of the new invader to contribute to the decline of A. zaliosus
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