Polyandry facilitates postcopulatory inbreeding avoidance in house mice

The avoidance of genetic incompatibilities between parental genotypes has been proposed to account for the evolution of polyandry. An extension of this hypothesis suggests polyandry may provide an opportunity for females to avoid the cost of inbreeding by exploiting postcopulatory mechanisms that bias paternity toward unrelated male genotypes. Here we test the inbreeding avoidance hypothesis in house mice by experimentally manipulating genetic compatibility via matings between siblings and nonsiblings. We observed little difference in reproductive success between females mated to two siblings or females mated to two nonsiblings. Females mated to both a sibling and a nonsibling tended to have a lower litter survival, but only when the first male to mate was a sibling. Microsatellite data revealed that paternity was biased toward nonsiblings when a female mated with both a sibling and a nonsibling. Unlike previous studies of invertebrates, paternity bias toward the sibling male was independent of mating sequence. We provide one of the first empirical demonstrations that polyandry facilitates postcopulatory sexual selection in a vertebrate. We discuss this result in relation to the possibility of selective fertilization of ova based on major histocompatibility complex (MHC) haploid expression of sperm.     

Egg-hatching benefits gained by polyandrous female locusts are not due to the fertilization advantage of nonsibling males

Several studies suggest that polyandrous females bias paternity in favor of unrelated males to avoid inbreeding depression. Here we tested whether the migratory locust biases sperm usage toward unrelated males by analyzing the paternity of offspring from females mated with either two siblings, or two nonsiblings, or a sibling and a nonsibling in either order. We found that the eggs of females mated only with siblings had decreased hatching success. When females mated with both a nonsibling and a sibling, egg hatchability was significantly increased. Subsequent paternity analyses found no evidence that females could avoid fertilization by sibling males. Therefore, improvement of the hatchability of eggs sired by siblings suggests that rather than biased fertilization by females toward genetically compatible or superior males, male-induced maternal effects or direct effects of male ejaculates might influence the survival of offspring sired by related males.     

Ontogenetic isolation favours sibling cannibalism in mites

Inclusive fitness theory suggests that cannibalistic individuals should preferentially eat unrelated prey when given a choice between related and unrelated individuals. Using the predatory mite Phytoseiulus persimilis, I investigated whether having contact with siblings during a sensitive ontogenetic phase or not determines whether cannibalistic protonymphs tend to eat more sibling or nonsibling larvae in choice situations. Cannibals reared with siblings preferentially ate nonsibling larvae when these had been reared in a sibling group but showed no preference when the larvae had been reared in isolation. Cannibals reared in isolation showed no preference when the larvae had been reared in a sibling group and preferentially ate sibling larvae when these had been reared alone. The occurrence of preferential sibling cannibalism when both cannibal and prey had been reared in isolation suggests the use of self-referent phenotype matching to distinguish between siblings and nonsiblings.     

Kinship alters the effects of forced cohabitation on body weight,mate choice and fitness in the rat-like hamster Tscheskia triton

It has been documented that social isolation imparts deleterious effects on gregarious rodents species,but caging in group imparts such effects on solitary rodents. This study was attempted at examining how kinship to affect body weight,behavioral interaction,mate choice and fitness when we caged male and female rat-like hamsters Tscheskia triton in pair,a solitary species. We found that females paired with nonsibling males became heavier than the females paired with sibling males,but both agonistic and amicable behavior between paired males and females did not differ between sibling and nonsibling groups. This indicated that kinship might reduce females' obesity in response to forced cohabitation,and dissociation might exist between physiological and behavioral responses. Furthermore,binary choice tests revealed that social familiarity between either siblings or nonsiblings decreased their investigating time spent in opposite sex conspecific of cage mates and/or their scents as compared with those of nonmates,suggesting effects of social association on mate and kin selection of the hamsters. On the other side,both females and males caged in pair with siblings show a preference between unfamiliar siblings or their scents and the counterparts of nonsiblings after two month separation,indicating that the kin recognition of the hamsters might also rely on phenotype matching. In addition,cohabitation (or permanent presence of fathers) elicited a lower survival of pups in nonsibling pairs than sibling pairs,but did not affect litter size,suggesting that kinship affects fitness when housing male and female ratlike hamsters together. Therefore,inbreeding might be adapted for rare and endangered animals.     

Consequences of mating with siblings and nonsiblings on the reproductive success in a leaf beetle

Choosing a suitable mating partner is crucial for the fitness of an individual, whereby mating with siblings often results in inbreeding depression. We studied consequences of mating with siblings versus nonsiblings in the mustard leaf beetle, Phaedon cochleariae (Coleoptera: Chrysomelidae), on lifetime reproductive traits. Furthermore, we analyzed whether cuticular hydrocarbon (CHC) profiles are family specific and could potentially influence the mating behavior of young adults. We hypothesized a reduced reproductive success of females mated with siblings and a more rapid mating of males with nonsiblings. The hatching rate from eggs of sibling pairs was lower compared to that of nonsibling pairs, pointing to inbreeding depression. Furthermore, the number of eggs laid by females decreased over time in both sibling and nonsibling pairs. Interestingly, the CHC profiles and the body mass differed between families. However, the beetles did not avoid siblings and accepted them as readily as nonsiblings for mating in no‐choice tests. In summary, although it had negative consequences to mate a sibling and although siblings could potentially be recognized by their CHC profiles, the beetles did not show a delayed mating with siblings. Our results indicate that P. cochleariae beetles have not developed a precopulatory mechanism to avoid inbreeding, at least under the test conditions applied here. We predict that instead a polyandrous mating system and/or postcopulatory mechanisms might have evolved in this species by which inbreeding costs can be reduced.     

Self-grooming and sibling recognition in meadow voles,Microtus pennsylvanicus,and prairie voles,M. ochrogaster

Self-grooming in response to the odours of an opposite-sex conspecific may reflect sexual motivation on the part of the actor. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, and prairie voles,M. ochrogaster , both self-groom at different rates when exposed to the odours of their siblings as compared to those of nonsiblings. This prediction was studied under the context of social memory for siblings and the effects of isolation on memory for siblings. The hypothesis explains the self-grooming responses of meadow voles isolated from their siblings for 10 days and of prairie voles isolated from their siblings for 20 days. However, 20 days of isolation for male and female meadow voles, and 30 days of isolation for male prairie voles were sufficient to induce these animals to self-groom at a similar rate to both sibling and nonsibling odours, suggesting that after isolation these animals no longer recognized their opposite-sex siblings. Female prairie voles isolated for 30 days self-groomed more in response to the odours of male nonsiblings than to those of male siblings, suggesting that female prairie voles still recognize their male siblings after isolation. This study is the first to provide empirical evidence that, in the context of sibling recognition, self-grooming behaviour is directed at unfamiliar opposite-sex conspecifics, and that the communicative function of self-grooming (sexual motivation) is associated with social memory for siblings. Differences in the self-grooming behaviour of meadow voles and prairie voles may be associated with several aspects of their life history characteristics.     

Lifetime inbreeding depression in a leaf beetle

Ongoing habitat loss and fragmentation result in rapid population size reductions, which can increase the levels of inbreeding. Consequently, many species are threatened by inbreeding depression, a loss of individual fitness following the mating of close relatives. Here, we investigated inbreeding effects on fitness‐related traits throughout the lifetime of the mustard leaf beetle (Phaedon cochleariae) and mechanisms for the avoidance of inbreeding. Previously, we found that these beetles have family‐specific cuticular hydrocarbon profiles, which are likely not used as recognition cue for precopulatory inbreeding avoidance. Thus, we examined whether adult beetles show postcopulatory inbreeding avoidance instead. For this purpose, we determined the larval hatching rate of eggs laid by females mated sequentially with two nonsiblings, two siblings, a nonsibling, and a sibling or vice versa. The beetles suffered from inbreeding depression throughout their entire ontogeny, as evinced by a prolonged larval development, a decreased larval and adult survival and a decreased reproductive output of inbred compared to outbred individuals. The highest larval hatching rates were detected when females were mated with two nonsiblings or first with a sibling and second with a nonsibling. Significantly lower hatching rates were measured in the treatments with a sibling as second male. Thus, the results do not support the existence of postcopulatory inbreeding avoidance in P. cochleariae, but revealed evidence for second male sperm precedence. Consequently, an alternative strategy to avoid inbreeding costs might exist in this beetle, such as a polyandrous mating system, potentially coupled with a specific dispersal behavior.     

Behavioral solutions to breeding cheetahs in captivity: Insights from the wild

Knowledge of cheetahs' behavior is increasingly seen as the key to solving the mystery of cheetahs' poor breeding performance in captivity. In the absence of zoos' maintaining systematic records of individuals' behavior during introductions, behavior of free-living animals can be informative. In the wild, most female cheetahs probably mate with males living in small groups or coalitions; thus, zoos may benefit from replicating these social conditions, provided injuries can be minimized. Relations between free-living coalition members are amicable, and escalated aggression was never witnessed during 4 years of observation. Some antagonism was seen in newly formed trios, although this had disappeared in longer established coalitions. Minor aggression occurred over carcasses, being greater at small and intermediate sized kills than at large ones. In the presence of females, mild intramale aggression was only seen within 1 of 7 coalitions. Free-living females showed similar rates of behavior in the presence of different numbers of males, aside from more frequent growling at large groups. These findings suggest that captive institutions should be less nervous about housing male cheetahs together and introducing females to groups of males for purposes of breeding. © 1993 Wiley-Liss, Inc.     

Over-marking and Adjacent Marking are Influenced by Sibship in Male Prairie Voles,Microtus ochrogaster

Scent over-marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific. Over-marking may provide advantages in the transfer of information to the individual whose scent is on top but not to the individual whose scent is on the bottom. We tested the hypothesis that over-marking is a competitive form of olfactory communication and that male prairie voles would over-mark the scent marks of same-sex conspecifics more than those of same-sex siblings. Two age-matched male voles (first male and second male) were placed successively into an arena in which they were allowed to explore freely and scent mark for 15 min at age 12, 20, 28, 36, 44, and 52 d. The first male was placed into a clean arena, whereas the second male was placed into an arena containing either the scent marks of an age-matched male sibling or nonsibling. Age affected the total number of scent marks deposited by the voles; 12-20-d-old voles deposited fewer scent marks, over-marks and adjacent marks than did 28-52-d-old voles. Sibship did not affect the total number of scent marks deposited by the first and second voles but did affect the number of over-marks and adjacent marks deposited by the second vole. Siblings received significantly fewer over-marks and adjacent marks than did nonsiblings; this effect was most dramatic after the voles reached 28 d of age, a time coincident with the onset of puberty. Males separated from siblings and housed singly at 44-d-old and tested at 52-d-old, deposited significantly more over-marks and adjacent marks in arenas if the first vole was a nonsibling than if it was a sibling. This differential scent-marking supports the hypothesis that over-marking and adjacent marking are used as competitive forms of olfactory communication by male prairie voles.     

Reciprocity in play,grooming, and proximity in sibling and nonsibling young rhesus monkeys

Play, grooming, and proximity, and the degree to which these were reciprocated between pairs, were studied in immature sibling and nonsibling rhesus monkeys (Macaca mulatta)in four established captive groups over two seasons. “Interaction reciprocity” and “partner reciprocity” were assessed for each dyad for each of the three behaviors. In play, interaction reciprocity was based on the ratio between the play initiations by each dyad member,in grooming on the ratio between the grooming durations by each dyad member, and in proximity on the relative responsibility for proximity maintenance. Two or three most frequent (top) partners for each behavior were found for each individual. If two monkeys were among each other’s top partners, they were said to be reciprocal partners. Monkeys played with nonsiblings as much as with siblings but spent more time grooming and in proximity with siblings than with nonsiblings. Same-age nonsiblings (peers) were more frequent partners than other nonsiblings for each behavior. Siblings’ grooming interactions were more reciprocal than those of nonsiblings. There was no such effect for play and proximity. All-male dyads tended to be more reciprocal in play interactions, and all-female dyads tended to be more reciprocal in grooming interactions. In play, but not in grooming or proximity, the interaction reciprocity of reciprocal partners was higher than that of nonreciprocal dyads. It is argued that the three behaviors have similar roles in infant’s social development but they differ in the expression of this role. Hence the reciprocity patterns vary with the behavior.     

Postcopulatory inbreeding avoidance by female crickets only revealed by molecular markers

Multiple mating is thought to provide an opportunity for females to avoid the costs of genetic incompatibility by postcopulatory selection of compatible sperm haplotypes. Few studies have tested the genetic incompatibility hypothesis directly. Here we experimentally manipulated the compatibility of females with their mates using the gryllid cricket Teleogryllus oceanicus. We recorded the hatching success of eggs laid by females mated with two nonsibling males, two siblings, or one nonsibling male and one sibling. In contrast with two previous studies on crickets that have adopted this approach, the hatching success of eggs did not differ between females mated with two full siblings and females mated with two unrelated males, indicating that embryo viability was not a cost of inbreeding in this species. We assigned paternity to offspring produced by females mated to both a sibling and a nonsibling male using microsatellite markers. As in previous studies of this species, we were unable to detect any difference in the proportion of offspring sired by the 1st and the 2nd male to mate with a female when females were unrelated to their mates. However, in our experimental matings the proportion of offspring sired by the nonsibling male depended on his sequence position. Paternity was biased toward the nonsibling male when he mated first. Our data show that molecular analyses of paternity are essential to detect subtle mechanisms of postcopulatory sexual selection.     

Molecular genetic insights on cheetah (Acinonyx jubatus) ecology and conservation in Namibia

The extent and geographic patterns of molecular genetic diversity of the largest remaining free-ranging cheetah population were described in a survey of 313 individuals from throughout Namibia. Levels of relatedness, including paternity/maternity (parentage), were assessed across all individuals using 19 polymorphic microsatellite loci, and unrelated cheetahs (n = 89) from 7 regions were genotyped at 38 loci to document broad geographical patterns. There was limited differentiation among regions, evidence that this is a generally panmictic population. Measures of genetic variation were similar among all regions and were comparable with Eastern African cheetah populations. Parentage analyses confirmed several observations based on field studies, including 21 of 23 previously hypothesized family groups, 40 probable parent/offspring pairs, and 8 sibling groups. These results also verified the successful integration and reproduction of several cheetahs following natural dispersal or translocation. Animals within social groups (family groups, male coalitions, or sibling groups) were generally related. Within the main study area, radio-collared female cheetahs were more closely interrelated than similarly compared males, a pattern consistent with greater male dispersal. The long-term maintenance of current patterns of genetic variation in Namibia depends on retaining habitat characteristics that promote natural dispersal and gene flow of cheetahs.     

Effects of white adipose tissue grafts on total body fat and cellularity are dependent on graft type and location

Surgical removal of body fat (lipectomy) triggers compensatory increases in nonexcised white adipose tissue (WAT), thus restoring adiposity levels in many species, including Siberian hamsters. In Siberian hamsters, when their lipectomized WAT is transplanted to another site (autologous grafts, no net change in body fat), healthy grafts result, but the lipectomy-induced compensatory increases in nonexcised WAT masses are exaggerated, an effect that apparently occurs only when the grafts contact intact WAT. When WAT is added to nonlipectomized hamsters to increase body fat, native WAT pads do not decrease. Thus WAT addition or removal-replacement does not induce compensatory WAT responses consistent with total body fat regulation as does WAT subtraction. Therefore, we tested whether the exaggerated response to lipectomy occurring with autologous WAT transplantation is dependent on graft site placement and whether the donor graft source [inguinal or epididymal WAT (IWAT, EWAT), sibling vs. nonsibling] affected body fat responses to WAT additions in nonlipectomized hamsters. Lipectomized hamsters received subcutaneous autologous EWAT grafts placed remotely from other WAT (ventrum) or in contact with intact WAT (dorsum), whereas intact hamsters received EWAT or IWAT grafts from sibling or nonsibling donors. The exaggerated response to lipectomy only occurred when grafts were in contact with intact WAT. EWAT, but not IWAT, additions to nonlipectomized siblings or nonsiblings increased native IWAT and retroperitoneal WAT mass but not EWAT mass compared with controls. Collectively, WAT transplantation to either lipectomized or nonlipectomized hamsters increased body fat contingent on graft contact with intact or native WAT.     

Efficiency and Significance of Multiple Vocal Signals in Sibling Competition

Animals can compete for resources by displaying various acoustic signals that may differentially affect the outcome of competition. We propose the hypothesis that the most efficient signal to deter opponents should be the one that most honestly reveals motivation to compete. We tested this hypothesis in the barn owl (Tyto alba) in which nestlings produce more calls of longer duration than siblings to compete for priority access to the indivisible prey item their parents will deliver next. Because nestlings increase call rate to a larger extent than call duration when they become hungrier, call rate would signal more accurately hunger level. This leads us to propose three predictions. First, a high number of calls should be more efficient in deterring siblings to compete than long calls. Second, the rate at which an individual calls should be more sensitive to variation in the intensity of the sibling vocal competition than the duration of its calls. Third, call rate should influence competitors’ vocalization for a longer period of time than call duration. To test these three predictions we performed playback experiments by broadcasting to singleton nestlings calls of varying durations and at different rates. According to the first prediction, singleton nestlings became less vocal to a larger extent when we broadcasted more calls compared to longer calls. In line with the second prediction, nestlings reduced vocalization rate to a larger extent than call duration when we broadcasted more or longer calls. Finally, call rate had a longer influence on opponent’s vocal behavior than call duration. Young animals thus actively and differentially use multiple signaling components to compete with their siblings over parental resources.     

An investigation of sibling recognition in Rana cascadae tadpoles

Sibling recognition was studied experimentally in tadpoles of the Cascades frog, Rana cascadae. Sibships were divided into two groups at an early developmental stage. One group was reared with siblings and the second with a mixture of siblings and non-siblings. Whe given a choice of associating with a sibling or non-sibling group, individuals reared with siblings preferred siblings. One mixed-reared group spent more time associating with unfamiliar siblings than unfamiliar nonsiblings. Tadpoles of another mixed-reared group preferred to associate with pure siblings over a mixture of siblings and non-siblings with which they were reared. When the stimulus animals were taken exclusively from the mixed-rearing tank, two mixed-reared groups showed no sibling preferences. Our results suggest that early association with non-siblings does not affect sibling recognition in this species.     

Discrimination against Water Containing Unrelated Conspecifics and a Marginal Effect of Relatedness on Spacing Behaviour and Growth in Juvenile Brown Trout, Salmo trutta L.

In this study, we assessed whether juvenile brown trout are able to discriminate between, and swim towards, water containing unrelated conspecifics and blank stream water. In a second stage we investigated the behavioural response to sibling-scented vs. nonsibling conspecific-scented water, and how the social environment could affect growth. All the six families (full sibs) tested showed an overall preference to blank water instead of water scented by unfamiliar fish of similar age and size. This result reveals that juvenile brown trout are able to detect chemical water components released by conspecifics, and show a biased behaviour based on this ability. When trout were given the choice between water scented by sibs and unfamiliar nonsibs, results were variable, some families spent more time in the sibling-scented water channel (only significant for one of six families) while others showed the opposite trend. Large within-family variation was also observed in the responses of individual fish towards water scented by siblings and nonsiblings. When fish from three of the families were reared with either siblings or nonsiblings, we obtained results that were only partially consistent with the hypothesis that fish growth could be enhanced in the preferred social environment (which had been predicted from the results of the choice tests).     

Coalition formation,mate selection and pairing behaviour of the Crested Francolin

Transect field observations were conducted on the behaviour of Crested Francolin Dendroperdix sephaena to describe male coalitions in the Borakalalo National Park, North West province, South Africa during May, August, October and December 2008, and again in July 2009. Crested Francolin form male coalitions following the breeding season in May. Young males leave their natal coveys and join old males in these coalitions, which are not based on kinship and consist of up to nine members. These coalitions are joined by a young female from June to October, followed by the breeding season when pairs replace coalitions. The coalition is a prelude to successful mating. The single female calls in the coalition, which triggers a cacophony, and her presence often erupts in physical conflicts between males. This cacophony is interpreted as signal jamming where males prevent one another from forming a duet with the female, clearly showing competition between them for winning over the female for mating. A well-synchronised duet forms the basis of pair formation. Old females are not particularly selected for pairing. The coalition is also a surrogate covey for young males because it optimises predator surveillance. The pair bond also optimises predator surveillance for each other throughout the year.     

Territorial vocalization in sympatric damselfish: acoustic characteristics and intruder discrimination

Damselfishes are well known for their aggressive, territorial behaviour during which the use of vocalization behaviour has been well documented. However, agonistic acoustic signalling has been understudied in particular when the vocalizations are interspecific. In this study, we characterize and compare the previously undescribed vocalization behaviour of longfin damselfish (Stegastes diencaeus), in an agonistic context, with the closely related and sympatric dusky damselfish (Stegastes adustus). Next, we examined if these congeneric species modulate their vocalizations in a similar pattern to previously described aggressive behaviour patterns. Audio field recordings of territorial males were obtained in response to three separate stimuli: (1) conspecific male damselfish, (2) heterospecific male damselfish and (3) a common intruder, the slippery dick wrasse (Halichoeres bivittatus). The vocal repertoires of both longfin and dusky damselfish comprised the same three distinct call types: chirps, pops and pulse trains. However, temporal measures of the calls showed significant differences between species. Additionally, dusky damselfish were more vocal overall, producing more calls and spending more time calling than longfin damselfish. These responses were stimulus and species dependent, as the two species modulated acoustic response by modulating pulse number based on intruder species. These results suggest that these closely related species of damselfish use vocalization behaviours that are both unique and context dependent.     

Proceptive calling by female lion-tailed macaques

During 6 years of monitoring breeding groups of lion-tailed macaques, it was discovered that females regularly emitted a non-copulatory vocalization during the follicular portion of the menstrual cycle. In the majority of cases females focused visually on a particular male when calling. Two-thirds of all calls were directed at males living outside the group. The responses of targeted males were consistent with the evidence from its temporal pattern that calling is a behavior used by females to draw attention to their willingness to receive copulations. Given that lion-tails are highly arboreal, it is postulated that in the wild state females use calls to attract the attention of males under conditions of limited visibility. As an unambiguous indicator of receptivity, this vocalization may facilitate the reproductive management of captive populations.     

Singing in the Face of Danger: the Anomalous Type II Vocalization of the Splendid Fairy-Wren

Males of certain species of fairy-wrens (Aves: Maluridae) emit a unique vocalization, the Type II vocalization, in response to the calls of potential predators. We conducted field observations and playback experiments to identify the contexts in which the Type II vocalization is emitted by splendid fairy-wren ( Malurus splendens ) males, and to examine social and genetic factors that influence its occurrence. In field observations and controlled playback experiments, Type II vocalizations were elicited most consistently by calls of the predatory gray butcherbird ( Cracticus torquatus ). Some vocalizations from other avian species also elicited Type II vocalizations, and the majority of these were vocalizations from avian predators. Splendid fairy-wrens are cooperative breeders, and males that responded with Type II vocalizations to playbacks of butcherbird calls tended to be primary rather than secondary males, had larger cloacal protuberances, and were older than those that did not respond. In addition, secondary males that were sons of resident females were more likely than non-sons to respond with a Type II vocalization. In another playback experiment, females responded similarly to the Type I song and Type II vocalizations of their mates. Although the Type II vocalization is emitted primarily in response to predator calls, it is inconsistent with an alarm call explanation. Patterns of reproductive success among Type II calling males suggest that it does not function as an honest signal of male quality. At present, the function of the vocalization remains anomalous, but indirect fitness benefits may play a role in its explanation.