Aggression towards shared enemies by heterospecific and conspecific cichlid fish neighbours

Topi K Lehtonen

doi:10.1007/s00442-019-04483-0

Abstract

Successful territory defence is a prerequisite for reproduction across many taxa, and often highly sensitive to the actions of territorial neighbours. Nevertheless, to date, assessments of the significance of the behaviour of heterospecific neighbours have been infrequent and taxonomically restricted. In this field study, I examined the importance of both heterospecific and conspecific neighbours in a biparental fish, the convict cichlid, Amatitlania siquia. This was done by assessing the colonisation rates of vacant territories, the rates of aggression by the territory holders, and the overall rates of aggression towards intruders, in treatments that controlled the proximity of both neighbour types. Convict cichlid pairs colonised vacant nesting resources (territory locations) at similar rates independent of the proximity of heterospecific (moga, Hypsophrys nicaraguensis) or conspecific neighbours. However, a model of sympatric cichlid intruder was subjected to considerably higher overall levels of aggression when mogas were nearby. In contrast, the proximity of conspecifics did not have a significant effect on the overall aggression towards the intruder. These results suggest that previously demonstrated higher survival of convict cichlid broods in close proximity of mogas may be driven by aggression towards shared enemies. No conclusive evidence was found regarding whether mogas also influence convict cichlids’ investment into anti-intruder aggression: the results show a marginally non-significant trend, and a moderately large effect size, to the direction of a lower investment in mogas’, but not conspecifics’, proximity. More generally, heterospecific neighbours may provide protective benefits in a wider range of ecological settings than commonly considered.

Highlights

Success in aggressive defence of a breeding territory towards rivals and would-be predators of offspring is often a prerequisite for reproduction
To investigate protective territorial aggression, and potential for energy savings with regard to heterospecific and conspecific neighbours, I focused on two species of Neotropical, territorial cichlid fish, convict cichlids, Amatitlania siquia, and mogas, Hypsophrys nicaraguensis (Fig. 1a)
In experiment 3, I assessed the rate of aggression directed to an intruder model, which was placed next to the focal convict cichlid territory that was associated with a nesting resource and occupied by a convict cichlid pair

Summary

Introduction

Success in aggressive defence of a breeding territory towards rivals and would-be predators of offspring is often a prerequisite for reproduction. To investigate protective territorial aggression, and potential for energy savings with regard to heterospecific and conspecific neighbours, I focused on two species of Neotropical, territorial cichlid fish, convict cichlids, Amatitlania siquia, and mogas, Hypsophrys nicaraguensis (Fig. 1a). In both species, the male and female of a breeding pair claim a territory, which is aggressively defended as a site for egg laying and later rearing the fry (McKaye 1977a; Lehtonen 2008; Lehtonen et al 2015). Despite mogas being larger than convict cichlids, the two species use an overlapping niche space, and their juveniles, in particular, are likely to have very similar diets and shared would-be predators (McKaye 1977a; Lehtonen 2008; personal observations)

Materials and methods

Results

Discussion

Compliance with ethical standards