Paternity and paternal effort in the pumpkinseed sunfish

Theoretical models suggest that males should adjust their parentaleffort according to paternity when parental effort is costly,paternity varies among clutches, and males have a cue to assesspaternity. To date, nearly all tests of this theory have beenconducted using birds as model organisms. In this study we examinedthese three factors and the relationship between paternity andmale parental care in a fish system. In the pumpkinseed sunfish(Lepomis gibbosus), parental care is provided exclusively bymales (parentals), but some males (sneakers) parasitize othersby sneaking fertilizations. Parental males significantly lostweight during the parental care period. Clutch size and amountof parental effort did not affect a male's probability of obtainingmore eggs. Paternity was variable among broods. The proportionof young sired by a parental male was not associated with frequencyof fanning eggs or defense of hatched young, but was positivelycorrelated with levels of nest defense during the egg stage.Egg survivorship might restrict an adjustment of fanning behavior,and a general decline in parental behavior (with brood age)might explain the lack of adjustment once the eggs hatch. Parentalmales did not adjust their care when we experimentally manipulatedone possible cue of paternity. Together, these results indicatethat male pumpkinseeds do adjust their care in relation to paternity,but the cues used to assess paternity are not clear.     

Experimentally induced helper dispersal in colonially breeding cooperative cichlids

The ‘benefits of philopatry’ hypothesis states that helpers in cooperatively breeding species derive higher benefits from remaining home, instead of dispersing and attempting to breed independently. We tested experimentally whether dispersal options influence dispersal propensity in the cooperatively breeding Lake Tanganyika cichlids Neolamprologus pulcher and N. savoryi. Cooperative groups of these fishes breed in densely packed colonies, surrounded by unoccupied, but apparently suitable breeding habitat. Breeding inside colonies and living in groups seems to benefit individuals, for example by early detection and deterrence of predators. We show that despite a slight preference of both species for habitat with a higher stone cover, 40% of the preferred habitat remained unoccupied. On average, the colonies contained a higher number of (1) predators of adults, juveniles and eggs, (2) shelter competitors, and (3) other species including potential food competitors, compared to the outside colony habitat. Apparently, habitat differences cannot explain why these cichlids breed in colonies. Accordingly, dispersal may not be limited by a lack of suitable breeding shelters, but by the relatively higher risk of establishing an outside- compared to a within-colony breeding territory. To test whether cichlids prefer within- to outside-colony breeding territories, we provided breeding shelters inside the colony and at the colony edge and studied helper dispersal. As expected, significantly more shelters were occupied within the colony compared to the edge. New breeding pairs with several helpers occupied these shelters. We conclude that although breeding habitat is plentiful outside the colonies, helpers delay dispersal to obtain a higher quality breeding position within the group or colony eventually, or they disperse in groups. Our results suggest that (1) group augmentation and Allee effects are generally important for dispersal decisions in cooperatively breeding cichlids, consistent with the ‘benefits of philopatry hypothesis’, and (2) habitat saturation cannot fully explain delayed dispersal in these species.     

First- and second-order sociality determine survival and reproduction in cooperative cichlids

Cooperative breeders serve as a model to study the evolution of cooperation, where costs and benefits of helping are typically scrutinized at the level of group membership. However, cooperation is often observed in multi-level social organizations involving interactions among individuals at various levels. Here, we argue that a full understanding of the adaptive value of cooperation and the evolution of complex social organization requires identifying the effect of different levels of social organization on direct and indirect fitness components. Our long-term field data show that in the cooperatively breeding, colonial cichlid fish Neolamprologus pulcher, both large group size and high colony density significantly raised group persistence. Neither group size nor density affected survival at the individual level, but they had interactive effects on reproductive output; large group size raised productivity when local population density was low, whereas in contrast, small groups were more productive at high densities. Fitness estimates of individually marked fish revealed indirect fitness benefits associated with staying in large groups. Inclusive fitness, however, was not significantly affected by group size, because the direct fitness component was not increased in larger groups. Together, our findings highlight that the reproductive output of groups may be affected in opposite directions by different levels of sociality, and that complex forms of sociality and costly cooperation may evolve in the absence of large indirect fitness benefits and the influence of kin selection.     

Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay

In cooperative breeding systems, dominant breeders sometimes tolerate unrelated individuals even if they inflict costs on the dominants. According to the ‘pay-to-stay’ hypothesis, (i) subordinates can outweigh these costs by providing help and (ii) dominants should be able to enforce help by punishing subordinates that provide insufficient help. This requires that dominants can monitor helping and can recognize group members individually. In a field experiment, we tested whether cooperatively breeding cichlid Neolamprologus pulcher subordinates increase their help after a forced ‘idle’ period, how other group members respond to a previously idle helper, and how helper behaviour and group responses depend on group size. Previously, idle helpers increased their submissiveness and received more aggression than control helpers, suggesting that punishment occurred to enforce help. Subordinates in small groups increased their help more than those in large groups, despite receiving less aggression. When subordinates were temporarily removed, dominants in small groups were more likely to evict returning subordinates. Our results suggest that only in small groups do helpers face a latent threat of punishment by breeders as predicted by the pay-to-stay hypothesis. In large groups, cognitive constraints may prevent breeders from tracking the behaviour of a large number of helpers.     

Paternity in Sooty Mangabeys

We determined paternity for 78 sooty mangabeys [(Cercocebus torquatus atys (Groves, 1978) equivalent to C. atys (Napier and Napier, 1967)], born between 1986 and 1993, using DNA profile analysis. The analysis is based on two independent assays of the genome of each individual via multilocus DNA probes. The mangabeys were members of either a large (n = 98) or a small (n = 18) group. Overall, during two periods of analysis in the large group, higher-ranking males sired more offspring than their lower-ranking counterparts did, though during one period the correlation between dominance rank and reproductive success is not significant. Of the two males in the small group, the alpha male sired all of the offspring during one period. There is a significant correlation between mounts and the number of surviving offspring each male sired in one birth year. Moreover, the same male did not always sire the offspring of a given female from year to year. Behavioral data focusing on male–offspring interactions show that offspring (n = 15) did not preferentially affiliate with their sire and that males affiliated with infants too infrequently for analysis. Thus, in a large sooty mangabey colony: (1) dominance rank generally predicts reproductive success; (2) adult males are not preferentially attracted to their offspring, or infants to their sires; and (3) the same male generally does not sire the offspring of a given female from year to year.     

Interspecific brood-mixing in Tanganyikan cichlids

Synopsis We collected schools of young, guarded by parents, of six common cichlid species to investigate the frequency and origin of interspecific brood-mixing. The main host species were a piscivore Lepidiolamprologus elongatus and a scale-eater Perissodus microlepis; more than half of their schools included heterospecific young, accounting for 20–40% of the total young. Most of the foreign young belonged to four biparental mouth-brooders whose parents have a habit of carrying their young in their mouths. Many of these young were smaller than the largest young brooded by their own parents. We concluded that adoption of young before independence results from farming-out, a behavior by which parents actively transfer their young to foster parents.     

Predator-induced neophobia in juvenile cichlids

Predation is an important but often fluctuating selection factor for prey animals. Accordingly, individuals plastically adopt antipredator strategies in response to current predation risk. Recently, it was proposed that predation risk also plastically induces neophobia (an antipredator response towards novel cues). Previous studies, however, do not allow a differentiation between general neophobia and sensory channel-specific neophobic responses. Therefore, we tested the neophobia hypothesis focusing on adjustment in shoaling behavior in response to a novel cue addressing a different sensory channel than the one from which predation risk was initially perceived. From hatching onwards, juveniles of the cichlid Pelvicachromis taeniatus were exposed to different chemical cues in a split-clutch design: conspecific alarm cues which signal predation risk and heterospecific alarm cues or distilled water as controls. At 2 months of age, their shoaling behavior was examined prior and subsequent to a tactical disturbance cue. We found that fish previously exposed to predation risk formed more compact shoals relative to the control groups in response to the novel disturbance cue. Moreover, the relationship between shoal density and shoal homogeneity was also affected by experienced predation risk. Our findings indicate predator-induced, increased cross-sensory sensitivity towards novel cues making neophobia an effective antipredator mechanism.     

Scale morphology in Malawian cichlids

The morphology of 24 endemic cichlid species from Lake Malawi was studied with scanning electron microscopy. Several structures possibly of value for taxonomic and evolutionary studies were discovered. Six types of scale shapes and three types of interradial denticles were detected. The spiny area in the exposed part of the scale varied from nonexistent to 148° wide. Several regenerated scales with large focus and short radii were found. Various scale characters, which may prove valuable for phylogenetic purposes, are described and their use in phylogeny construction tested.     

Lateralization of lateral displays in convict cichlids

We examine lateralization of lateral displays in convict cichlids, Amatitlania nigrofasciata, and show a population level preference for showing the right side. This enables contesting pairs of fish to align in a head-to-tail posture, facilitating other activities. We found individuals spent a shorter mean time in each left compared with each right lateral display. This lateralization could lead to contesting pairs using a convention to align in a predictable head-to-tail arrangement to facilitate the assessment of fighting ability. It has major implications for the common use of mirror images to study fish aggression, because the 'opponent' would never cooperate and would consistently show the incorrect side when the real fish shows the correct side. With the mirror, the 'normal' head-to-tail orientation cannot be achieved.     

Reproductive suppression in female cooperatively breeding cichlids

Suppression by dominants of female subordinate reproduction has been found in many vertebrate social groups, but has rarely been shown experimentally. Here experimental evidence is provided for reproductive suppression in the group-living Lake Tanganyika cichlid Neolamprologus pulcher. Within groups of three unrelated females, suppression was due to medium- and small-sized females laying less frequently compared with large females, and compared with medium females in control pairs. Clutch size and average egg mass of all females depended on body size, but not on rank. In a second step, a large female was removed from the group and a very small female was added to keep the group size constant. The medium females immediately seized the dominant breeding position in the group and started to reproduce as frequently as control pairs, whereas clutch size and egg mass did not change. These results show that female subordinate cichlids are reproductively capable, but apparently suppressed with respect to egg laying. Nevertheless, some reproduction is tolerated, possibly to ensure continued alloparental care by subordinate females.     

Temporal diversification of Central American cichlids

Background  

Cichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments. To examine whether ecological opportunity increased diversification (speciation minus extinction) early in a species-rich cichlid radiation, we determined if Heroine cichlids experienced a burst of diversification following their invasion of Central America.     

Paternity loss in contrasting mammalian societies

Recent genetic analyses show that, in social mammals, loss of paternity by breeding males varies with strategies of mate guarding rather than with the degree of polygyny.     

Paternity Recognition in Multi-male Primate Groups

A traditional view of multi-male primate groups has held thatmales provide relatively little direct care to infants, possiblyas a result of low confidence of paternity associated with arelatively promiscuous breeding system. In the last five yearsthis view has changed as a result of a careful documentationof intimate male-infant affiliations in certain species, especiallythe savanna-dwelling baboons (Papio spp.). The occurrence ofthese affiliations raises the question as to whether males carefor their own offspring preferentially and, if so, on what basismale confidence of paternity is mediated. Recent field studiesof baboons suggest that male-infant relationships are mediatedthrough affiliations between the males and the infants' mothers,but the degree to which these male-female affiliations are basedon prior mating experience (hence, paternity) has not been established. Comparative studies of male-infant relations in primates havegiven little attention to the variation in the intensity andform of male care patterns within the set of species that havea multi-male social organization. Among multi-male species,male care of young is reported most often in baboons and barbarymacaques (Macaca sylvanus) and least often in other macaques,chimpanzees (Pan troglodytes), and vervet monkeys (Cercopithecus).This interspecific variation may result both from differencesin the importance of male care to infant survival and from differencesin male confidence of paternity, which in turn may relate toseasonal breeding patterns and, in particular, to the presenceor absence of conspicuous signs of ovulation in females.