Helpful Female Subordinate Cichlids Are More Likely to Reproduce

Abstract

BackgroundIn many cooperatively breeding vertebrates, subordinates assist a dominant pair to raise the dominants' offspring. Previously, it has been suggested that subordinates may help in payment for continued residency on the territory (the ‘pay-to-stay hypothesis’), but payment might also be reciprocated or might allow subordinates access to reproductive opportunities.Methodology/Principal FindingsWe measured dominant and subordinate female alloparental brood care and reproductive success in four separate experiments and show that unrelated female dominant and subordinate cichlid fish care for each other's broods (alloparental brood care), but that there is no evidence for reciprocal ‘altruism’ (no correlation between alloparental care received and given). Instead, subordinate females appear to pay with alloparental care for own direct reproduction.Conclusions/SignificanceOur results suggest subordinate females pay with alloparental care to ensure access to the breeding substrate and thereby increase their opportunities to lay their own clutches. Subordinates' eggs are laid, on average, five days after the dominant female has produced her first brood. We suggest that immediate reproductive benefits need to be considered in tests of the pay-to-stay hypothesis.

Kinship reduces alloparental care in cooperative cichlids where helpers pay-to-stay

“…Clutches produced by the subordinate females received little alloparental care from the dominant female, which suggests that alloparental care of subordinates is not reciprocated by dominant females. Thus, reciprocal exchange of the same commodity 41 , resembling for instance a tit-for-tat paradigm, appears not to be important for brood care decisions of N. pulcher females 35 . The patterns of alloparental brood care we found cannot be explained solely by kin-selection 1 or by group augmentation models 21 , without involving coercive mechanisms (see Table 5 for summary).…”

“…cleaning and fanning) could not be measured and potential effects of subordinate reproduction were not considered, which can strongly affect subordinate helping effort 35,49 . Potential effects of relatedness on alloparental brood care have generally received much attention 4 .…”

“…Brood care was observed and quantified following a protocol established in previous studies 35,40 . The frequencies of egg cleaning acts and egg fanning bouts were recorded during a 15-min observation period for both females and the male.…”

“…The clutch was assigned to the dominant or the subordinate female using observations of sham-spawning and substrate cleaning behaviour of the breeding shelter on the days preceding clutch deposition. This method has been validated by molecular parentage analysis and was shown to yield very little error 35 . After the brood care observation the eggs were temporarily removed, counted and a sample of B5 eggs was collected for egg mass assessment.…”

“…If such compensation occurs, however, similar eviction rates of related and unrelated subordinates might be expected in case helping depends on coercion 28 . Furthermore, if subordinates breed in the territory of dominants 34 , alloparental brood care should not be reciprocated by the dominant female 35 in a pay-to-stay scenario, and dominant female fitness should be independent of relatedness to subordinates, as helper payment may only compensate for imposed costs and not provide net fitness benefits to dominants 28 . Finally, if helping is triggered by coercion and if unrelated subordinates need to compensate for imposing costs on dominants 27,28 , they should increase their investment in alloparental brood care behaviour if these costs to dominants are experimentally raised; in contrast, such increased cost compensation should be weaker or absent in related subordinates.…”