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1.
Susan M. Haig Jeffrey R. Walters Jonathan H. Plissner 《Behavioral ecology and sociobiology》1994,34(4):295-303
We examined the genetic relationship among putative parents, offspring, and helpers in 224 red-cock-aded woodpeckers (Picoides borealis) from the Sandhills of North Carolina. Comparison of DNA similarity with a pedigree constructed from 3,823 individually-marked birds observed from 1979 to 1992 provided verification of observed relatedness in the sampled population (R
2 = 0.87, df = 14, P < 0.001). In this population, breeding pairs may or may not have helpers, most of which are males that remain on their natal territory. Our sample included helpers assisting their parents, helpers assisting a related male and an unrelated female, and helpers assisting an unrelated pair. Band by band comparison and examination of similarity among DNA profiles indicated that all offspring from non-helped nests were sired by their putative parents (n = 28 families). Similarly, all but one offspring in helped nests were also sired by their putative parents (n = 16 families). In the exceptional case, the offspring evidently was sired by a male external to the group. Analysis of similarity values supported the conclusion that matings by helpers or extra-group males are rare or non-existent. Our results indicate that in this species advantages gained by individuals remaining on their natal territories as helpers do not generally include siring offspring.
Correspondence to: S. Haig 相似文献
2.
Ola Svensson Maria Lissåker Kenyon B. Mobley 《Behavioral ecology and sociobiology》2010,64(8):1325-1331
When parental care is costly, parents should avoid caring for unrelated young. Therefore, it is an advantage to discriminate
between related and unrelated offspring so that parents can make informed decisions about parental care. In the present study,
we test the hypothesis that male sand gobies (Pomatoschistus minutus) recognize and differentially care for their own offspring when given a choice between a nest with sired eggs and a second
nest with eggs sired by an unrelated male. The sand goby is a species with exclusive and costly paternal care. Male parasitic
spawnings (e.g., sneaking) as well as nest takeovers by other males are common. Our results show that nests containing sired
eggs were preferred and received significantly more care, as measured by nest building and nest occupancy, than nests with
foreign eggs even when males cared for both nests. These findings suggest that males respond to paternity cues and recognize
their own clutches. Relative clutch size also had a significant effect on male parental care. When sired clutches were larger
than foreign clutches, males preferred to care for their own nest. In the few cases where males chose to take care of foreign
nests, the foreign clutch was larger than their own clutch. Taken together, our results provide evidence that both paternity
cues and clutch size influence parenting decisions among male sand gobies. 相似文献
3.
Michael R. Lennartz Robert G. Hooper Richard F. Harlow 《Behavioral ecology and sociobiology》1987,20(2):77-88
Summary Thirty groups of red-cockaded woodpeckers (Picoides borealis) were studied from 1976–1982 to (1) determine the demographic structure of groups, (2) identify the role helpers play in reproductive activities, and (3) investigate the selective pressures promoting sociality and helping behavior. Groups had only 1 mated pair and 0–2 helpers. Approximately half of all groups had helpers and a given group had helpers some years but not others. Helpers, with rare exception, were males 1 or 2 years old and progeny of 1 or both members of the breeding pair. As a result of higher nestling survival, groups with helpers fledged significantly more young per year than unassisted pairs (
, SD=0.97,n=43 vs.
, SD=1.01,n=50). Nesting success was also associated with size and quality of nesting period home range, but evidence suggested that the increased number of young fledged resulted directly from the action of helpers. There was a significant positive correlation between reproductive success and experience of breeding females among unassisted pairs but a significant negative correlation among pairs with helpers. In groups with experienced females, helpers were assisting both their mothers and fathers and, therefore, were related to the offspring on the average by 0.50. In groups with inexperienced females, helpers were assisting their fathers and unrelated females and were related to the offspring by 0.25. The red-cockaded woodpecker's unique habit of excavating nest and roost cavities in living pines and the extended period of time required for excavation may be an important ecological constraint that promotes the retention of helpers. Because helpers are related to the offspring they help rear, kin selection and gains in indirect fitness may provide a partial explanation of why red-cockaded woodpecker helpers help. However, the negative correlation between the efficacy of helping behavior and the helpers' relatedness to the offspring they help rear implies that helpers are least effective in producing offspring which would represent greatest gains to indirect fitness. This raises questions about the relative importance of kin selection and indirect fitness in the evolution of helping behavior among red-cockaded woodpeckers. 相似文献
4.
Low frequency of extra-pair paternity in pied flycatchers revealed by DNA fingerprinting 总被引:8,自引:0,他引:8
Jan T. Lifjeld Tore Slagsvold Helene M. Lampe 《Behavioral ecology and sociobiology》1991,29(2):95-101
Summary Genetic parentage of 135 nestlings from 27 broods of polygynous and monogamous pied flycatchers Ficedula hypoleuca was analyzed by means of multilocus DNA fingerprinting. The minisatellite probe alpha-globin 3HVR detected approximately 12 scorable bands per fingerprint, and the proportion of bands shared between presumably unrelated adults averaged 0.22+0.08 SD. The fingerprints of 125 of the 135 nestlings made a complete match to those of their putative parents. In 4 nestlings a single mismatched band occurred, but since band sharing with both putative parents was high, the single mismatches were assumed to be caused by mutation. The 6 remaining nestlings had 5 or more mismatched bands each, low band-sharing proportions with their putative father and high band-sharing proportions with their putative mother. We thus conclude that they were all sired through extra-pair copulations (EPCs). Hence, only 4% of nestlings were sired through EPCs, and none resulted from intraspecific brood parasitism. One of the cuckolding males was identified, explaining all 5 mismatched bands in the nestling's fingerprint. Three of the illegitimate nestlings were from primary nests of polygynous males; 3 were from nests of monogamous males. The fact that many males in this study started to advertise for a second female in a distant territory several days before their first mate began egglaying, and still managed to secure almost exclusive paternity in their first brood, suggests that male polyterritoriality is not costly in terms of lost paternity. Common anti-cuckoddry tactics performed by male birds, like high rate of within-pair copulation and continuous mate-guarding thoughout the female's fertilizable period, do not seem to be important in pied flycatchers.Offprint requests to: J.T. Lifjeld 相似文献
5.
Susan L. Balenger L. Scott Johnson Brian S. Masters 《Behavioral ecology and sociobiology》2009,63(3):403-411
Ornamental traits are thought to evolve because they give individuals an advantage in securing multiple mates. Thus, the presence
of ornamentation among males in many monogamous bird species presents something of a conundrum. Under certain conditions,
extra-pair paternity can increase the variance in reproductive success among males, thus increasing the potential for sexual
selection to act. We addressed this possibility in the mountain bluebird (Sialia currucoides), a socially monogamous songbird in which males possess brilliant ultraviolet (UV)-blue plumage. Specifically, we asked whether
a male’s success at siring offspring within his own nest and within the nests of other males was related to his coloration.
In pairwise comparisons, males that sired extra-pair offspring were not more colorful than the males that they cuckolded.
However, males that sired at least one extra-pair offspring were, on average, brighter and more UV-blue than males that did
not sire extra-pair offspring. Brighter, more UV-blue males sired more offspring both with their own mate and tended to sire
more offspring with extra-pair mates and thus sired more offspring overall. Our results support the hypothesis that the brilliant
UV-blue ornamental plumage of male mountain bluebirds evolved at least in part because it provides males with an advantage
in fertilizing the eggs of multiple females. 相似文献
6.
Summary The costs and benefits of helping behavior were analyzed for 36 pairs of the Galápagos mockingbird, Nesomimus parvulus, and their associates. Helping at the nest is usually done by sons or males suspected to be offspring of the breeders. Costs and benefits to breeders were assessed by comparison of pairs with and without helpers, and costs and benefits to helpers were assessed by comparison of birds which help and those which establish themselves as novice breeders.Helping behavior benefits breeders by increasing fledging success and by reducing the adult energy load in territory defense and feeding of nestlings. Breeders assisted by helpers may also benefit by decreased nest predation. Helpers enhance their inclusive fitness by helping, and gain directly by increasing their chances of securing a territory. Helpers do not appear to gain any fitness advantage from the experience of assisting, nor do they increase their survivorship by remaining on natal territory.Ecological and demographic features such as saturated territories and low territory turn-over rates due to high adult survival may be primarily responsible for the evolution of the helping behavior, with kinselection reinforcing it. Associated features of this system are a male-biased population sex ratio, a greater energetic benefit to breeding males than to breeding females in having helpers, earlier dispersal and breeding by females than by males, and much more frequent helping by males than by females. These are interpreted as consequences of brothersister aggression that indirectly minimizes the chances of inbreeding. 相似文献
7.
Jan Komdeur 《Behavioral ecology and sociobiology》1994,34(3):175-186
Prebreeding Seychelles warblers (Acrocephalus sechellensis) frequently act as helpers on their natal territory, aiding in territory defence, predator mobbing, nestbuilding, incubation (only females) and feeding dependent young of their parents. In some cases helpers could attain breeding status (e.g. by joint-nesting) in their natal group and become co-breeders. Comparisons of group size and reproductive success on a given quality territory suggest that the presence of alloparents (helpers and cobreeders) significantly affects the reproductive success of their parents. The influence of alloparents on reproductive success was examined by removing alloparents from breeding units and comparing the success of natural-sized and artificially reduced groups. Removal experiments, controlled for territory quality, group size and breeder age, showed that the presence of one alloparent significantly improved the reproductive success of its parents. Analysis strongly suggests that this was entirely due to helping behaviour (i.e. providing care to offspring of their parents), thereby improving the helper's inclusive fitness benefits from staying at home. However, these experiments showed also that the presence of two or more alloparents in medium-quality territories significantly decreased reproductive success, compared with groups with one alloparent. Several lines of evidence suggest that this may have been due to the joint-nesting and reproductive competition that could occur in breeding groups, or simply to resource depression when a large number of previous offspring remained on their natal territory. 相似文献
8.
Relatedness, polyandry and extra-group paternity in the cooperatively-breeding white-browed scrubwren (Sericornis frontalis ) 总被引:3,自引:0,他引:3
Linda A. Whittingham Peter O. Dunn Robert D. Magrath 《Behavioral ecology and sociobiology》1997,40(4):261-270
We used DNA fingerprinting to examine the genetic parentage and mating system of the cooperatively breeding white-browed
scrubwren, Sericornis frontalis, in Canberra, Australia. Our analyses revealed a remarkable variety of mating tactics and social organization. Scrubwrens
bred in pairs or multi-male groups that consisted of a female and two or more males. Females were always unrelated to the
pair male or alpha (dominant) male. Among multi-male groups we found three different mating tactics. Firstly, when alpha and
beta (subordinate) males were unrelated, they usually shared paternity in the brood. This resulted in both males gaining reproductive
benefits directly. Secondly, when beta males were not related to the female but were related to the alpha males, beta males
sired offspring in some broods. In this situation, beta males gained reproductive benefits both directly and potentially indirectly
(through the related alpha male). Thirdly, when beta males were related to the female or both the female and alpha male, they
remained on their natal territory and did not sire any offspring. Thus beta males gained only indirect reproductive benefits.
Overall, when group members were related closely, the dominant male monopolized reproductive success, whereas when the members
were not related closely the two males shared paternity equally. This positive association between monopolization of reproduction
and relatedness is predicted by models of reproductive skew, but has not been reported previously within a single population
of birds. Other cooperatively breeding birds with both closely related and unrelated helpers may show a similar variety of
mating tactics. Finally, we found that extra-group paternity was more common in pairs (24% of young) than in multi-male groups
(6%), and we discuss three possible reasons for this difference.
Received: 21 May 1996 / Accepted after revision: 14 December 1996 相似文献
9.
Parental care is a costly part of reproduction. Hence, natural selection should favor males which avoid caring for unrelated
young. However, the decision to abandon or reduce care requires cues which are evaluated to give information on potential
reproductive value of the offspring. The prediction that male sand gobies, Pomatoschistus minutus, care for foreign eggs as long as they were spawned in their own nest and at least some of such cues are fulfilled was tested.
Egg-guarding males that had recently taken part in a spawning event were given a clutch of eggs that was sired either by themselves
or another male, in either their own or another male’s aquarium. Males that had not taken part in a spawning event were used
as controls and were given eggs sired by another male. We measured the amount of filial cannibalism and nest building. Control
group males did not care for eggs and ate them all before rebuilding the nest. In the other treatments, there were no significant
effects of paternity, though males moved to another male’s aquarium increased their clutch area threshold and completely consumed
larger clutches than males that were not moved. There was no intermediate response in any treatment in the form of increased
partial filial cannibalism or less well-constructed nests. Our results suggest that egg-guarding males cannot distinguish
between eggs sired by themselves and those sired by other males but are able to react to cues indicating paternity state.
Males do not adopt eggs to attract females in P. minutus. 相似文献
10.
Summary Parental exclusion analyses based on allozyme data were performed on 105 families of cliff swallows (Hirundo pyrrhonota) from southwestern Nebraska, USA. The protein products of seve polymorphic loci were resolved from blood, and at least one parental exclusion occurred at six of these loci. One or both putative parents were excluded for 35 nestlings from 22 different families. The mean number of non-kin nestlings in these families was 1.59. Non-kin nestlings were found in families with brood sizes ranging from two to five. A greater percentage of families in an 1100-nest colony had non-kin offspring than in two smaller colonics, although the difference was not statistically significant. Application of genetic models to these data and the observed distribution of parental exclusions suggested that multiple parentage in cliff swallows results more often from intraspecific brood parasitism than from forced extra-pair copulations. Based on the calculated probabilities of detecting non-kin, we estimate that 23.7% of all nestlings in our population are not the offspring of one or both of their putative parents. We estimate that about 43% of all cliff swallow nests in Nebraska contain at least one offspring resulting from intraspecific brood parasitism, and that about 6% of nests might contain offspring resulting from extra-pair copulations. 相似文献
11.
In cooperative breeders, mature males may compete for fertilizations. In this study, we measured the degree of multiple paternity
in a natural population of a cooperatively breeding fish. Neolamprologus pulcher (Perciformes: Cichlidae) is a highly social cichlid endemic to Lake Tanganyika. We used highly variable microsatellite loci
to survey 12 groups with an average number of 10.6 brood care helpers per group and a total of 43 offspring (mean 3.6 per
brood). In 11 of 12 groups, all young were assigned to the dominant female. The dominant male sired all offspring in three
groups, part of the offspring in four groups, and in five groups, he had no paternity at all. In total, 44.2% of young were
not fathered by the current male territory owner. Multiple paternity was found in 5 of 12 broods (41.7 %), with 8 of 35 young
(22.9 %) being sired by males other than the respective territory owners. This is an exceptionally high rate of extra-pair
paternity among cooperatively breeding vertebrates. Neither helpers present in these territories during collection nor neighbouring
males were unequivocally assigned to have sired these extra-pair young. However, behavioural observations suggest that male
helpers may have produced these young before being expelled from the territory in response to this reproductive parasitism.
We discuss these results in the light of reproductive skew theory, cooperative breeding in vertebrates and alternative reproductive
tactics in fish. 相似文献
12.
James H. Bandoli 《Behavioral ecology and sociobiology》2006,59(5):606-613
Filial cannibalism is hypothesized to allow nest-guarding males to recoup energy lost during nest defense. Males in many species
of fishes occasionally defend broods containing both sired and foster eggs due to shifts in nest site ownership or cuckoldry.
Such males are predicted to consume primarily foster eggs if the ability to discriminate among eggs exists. In a previous
laboratory study, male spottail darters (Etheostoma squamiceps) consumed significantly more foster eggs than sired eggs, suggesting the existence of a mechanism for discrimination using
chemical or positional cues. This discrimination mechanism in the spottail darter was tested by creating nest sites with half
sired eggs and half foster eggs (n=15), or with all sired eggs with half positionally relocated (n=9). Males defended these nests for 2 days in the field, and cannibalism was determined by counting eggs lost during that
interval. Neither foster eggs nor relocated sired eggs were consumed in greater numbers or percentages of the original brood
sizes than the unchanged sired eggs, indicating that male spottail darters do not discriminate between foster and sired eggs
by olfaction or position. Alternatively, the hypothesis that males treat all eggs in nest sites in which they have spawned
as sired explains the results of both studies. 相似文献
13.
Kapheim KM Bernal SP Smith AR Nonacs P Wcislo WT 《Behavioral ecology and sociobiology》2011,65(6):1179-1190
Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish
from other environmental factors. This is an important distinction within the context of social evolution, because if variation
in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as
those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which
might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary
nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive
helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores
provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content
varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content,
for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio
ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in
maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social
plasticity observed in M. genalis. 相似文献
14.
Christian C. Voigt Gerald Heckel Frieder Mayer 《Behavioral ecology and sociobiology》2005,57(5):457-464
We investigated how morphological traits of territorial males in the polygynous bat Saccopteryx bilineata were related to their reproductive success. Because of the frequency of aerial courtship displays and defence manoeuvres, and the high energetic costs of flight, we expected small and symmetric males to be better able to court females on the wing and to monopolize copulations with females in their harems. We predicted that small and symmetric males would sire more offspring within the colony and a larger portion of the young born within their harem than large or asymmetric males. We measured size and fluctuating asymmetry of 21 territorial males and analysed their reproductive success in 6 offspring cohorts (n=209 juveniles) using 11 microsatellite loci. As predicted, small and symmetric males had, on average, a higher reproductive success in the colony than large and asymmetric males. The percentage of young sired by males within their harem increased as males decreased in size, but was not influenced by fluctuating asymmetry. As fluctuating asymmetry of males correlated with their reproductive success within the colony but not within their harems, we infer that fluctuating asymmetry is probably related to female choice, whereas male size is probably important for harem defence on the wing.Communicated by G. Wilkinson 相似文献
15.
Female control of extra-pair fertilization in tree swallows 总被引:4,自引:0,他引:4
Summary In a Canadian population of tree swallows, Tachycineta bicolor, DNA fingerprinting has previously shown that half of all broods contain many offspring resulting from extra-pair copulations (EPCs), whereas the other half contain only legitimate offspring. This bimodal pattern of extra-pair paternity might be due to variation in the effectiveness of male paternity guards, variation in female ability to resist EPCs, and/or variation in female pursuit of EPCs. Here we report experimental evidence for female control of copulations and fertilizations and the occurrence of two alternative copulation strategies among females in this population. Ten paired male tree swallows were removed on the day their mates laid the first egg. Replacement males took over the nestbox within 0.5–23 h and attempted to copulate with the widowed female. Assuming that eggs were fertilized approximately 24 h prior to laying, the first two eggs were fertilized before the male was removed, while the third and subsequent eggs could potentially be fertilized by the replacement male. Fingerprinting revealed that the first two eggs were sired by the resident males in five nests and by extra-pair males in the remaining five nests. The widows that had been faithful to their initially chosen mate rejected copulation attempts by the replacement male until most of the eggs had been laid. Consequently, nearly all eggs laid by these females were sired by the original male. The widows that had been unfaithful prior to male removal copulated sooner with the replacement male than females that were faithful to their mate. However, these replacement males also had a very low fertilization success; most eggs were sired by males that were not associated with the nest. This is consistent with the situation in non-experimental nests where unfaithful females copulate with their mate at the same rate as faithful females, yet unfaithful females have a majority of offspring sired by extra-pair males. We conclude that fertilization patterns to a large extent are determined by the female through active selection and rejection of copulation partners, though our results also allow some speculation that females have control over sperm competition. Female copulation tactics are probably determined some currently unknown fitness benefits of having the offspring sired by particular males.Correspondence to: Raleigh J. Robertson 相似文献
16.
Hugh Drummond Roxana Torres Cristina Rodríguez Juarez Sin-Yeon Kim 《Behavioral ecology and sociobiology》2010,64(4):647-655
In multitudinous breeding colonies, kin interactions could go unnoticed because we are unaware of the kinship among adults
we observe. Evidence of cooperation and competition between close adult kin in a blue-footed booby colony was sought by analyzing
patterns of natal dispersal and proximity of nests. Male and female recruits nested closer to their own natal sites than to
their parents’ current sites. Males (only) dispersed less far when both parents were present than when no parent or one parent
was present, but not selectively close to fathers versus mothers when these were divorced. Neither parental presence nor parental
proximity affected breeding success of recruits of either sex. Although distances between the nests of simultaneously recruiting
broodmates were unrelated to their sex, males dispersed 13.1 m less when a sister was present than when a brother was present.
Neither sex was affected in its dispersal distance by the presence or hatching order/dominance of a broodmate. Neither sex
was affected in its breeding success by the presence versus absence of a broodmate, although female success increased with
proximity of their brothers. Parents and sisters may actively or passively help males establish their first territories near
their natal sites and nearby brothers may help females in their first breeding attempts; otherwise, boobies do not influence
each other’s natal dispersal and first breeding success. It appears that boobies do not nest selectively close to or far from
their parents, offspring, or broodmates. Why there is apparently so little cooperation and altruism between close adult relatives
in booby colonies is puzzling. 相似文献
17.
James V. Briskie Robert Montgomerie Tarmo Põldmaa Peter T. Boag 《Behavioral ecology and sociobiology》1998,43(3):181-190
In species where females copulate with more than one male during a single breeding attempt, males risk investing in offspring
that are not their own. In the polygynandrous Smith's longspur (Calcarius pictus), females copulate sequentially with one to three males for each clutch of eggs and most of these males later assist in feeding
the young. Using multilocus DNA profiling, we determined that there was mixed paternity in >75% of broods (n=31) but that few offspring (<1% of 114 nestlings) were sired by males outside the polygynandrous group. Male feeding rate
increased significantly with the number of young sired, with males siring four nestlings feeding the brood at double the frequency
of males siring only a single nestling. However, male Smith's longspurs appear to show a graded adjustment of paternal care
in response to paternity only when other males are available to compensate for reduced care: feeding rate did not vary in
relation to paternity when only one male provisioned young at the nest. There was no evidence that males could recognise their
own offspring within a brood and feed them preferentially. The number of offspring sired by each male was significantly correlated
with the number of days spent copulating with the attending female: on average, a male sired one offspring for every 2 days
of copulatory access. If males use their access to females to estimate paternity (and thereby decide on their subsequent level
of parental investment), a positive relationship is expected between the amount of female access and the subsequent feeding
rate to the nestlings. Nonetheless, male feeding effort was only weakly correlated with female access and more study is needed
to determine how males estimate their paternity in a brood.
Received: 1 June 1997 / Accepted after revision: 1 April 1998 相似文献
18.
Rita Covas Ambroise Dalecky Alain Caizergues Claire Doutrelant 《Behavioral ecology and sociobiology》2006,60(3):323-331
Indirect fitness benefits are believed to be an important force behind the evolution of cooperative breeding. However, helpers may associate with their relatives as a result of delayed dispersal, hence, kin associations might be a consequence of demographic viscosity rather than active choice. In addition, recent studies showed that helpers may have access to reproduction therefore direct benefits might also play an important role. Here, we investigate the possible roles of direct genetic benefits and kin associations on helping behavior in the sociable weaver Philetairus socius, a colonial and cooperatively breeding passerine. We used a microsatellite-based genotyping method to describe the genetic structure within nests and colonies. Within a colony, we found considerable genetic structure between males but not females. Sociable weaver colonies have several nests that are simultaneously active, giving individuals a choice of associating with a range of first-order kin to unrelated individuals. Helpers were significantly more related to the young in the helped nests than in other nests of the colony, suggesting an active choice for associating with kin. The helpers were generally offspring or first-order relatives of one (50%) or both (43%) breeders, although more infrequently, seemingly unrelated individuals also helped (7%). We found no supporting evidence of extrapair parentage and hence no direct genetic gains from helping in our population. This strong reproductive skew is contrary to theoretical models predicting conflicts over reproduction in stepfamilies. We discuss whether female decisions and/or other direct benefits of remaining in kin associations or helping might explain the high skew observed. 相似文献
19.
In facultatively eusocial hover wasps, some females leave their natal nests while others choose to stay and become helpers.
We tested whether the decisions of 126 newly emerged females to stay or leave depended on group size: the number of females
already resident on their natal nests. We predicted that females would be less likely to stay in larger groups, where the
benefits of helping are probably smaller and there is a smaller chance of inheriting the dominant position. We also predicted
that unrelated females would be less likely to join larger groups. We manipulated group size by removing residents from nests.
Newly emerged females disappeared from their natal nests at a rate of 2.5% per day, but did not disappear from manipulated
nests at higher rates than controls. Experimentally reducing group size also did not increase the frequency of joiners. Newly
emerged females disappeared at twice the rate of older subordinate females, suggesting the existence of a `leaving window'
early in life. One problem is the difficulty of distinguishing between leaving and death.
Received: 7 July 1998 / Accepted after revision: 25 October 1998 相似文献
20.
Reproduction by subordinates in cooperatively breeding Arabian babblers is uncommon but predictable 总被引:4,自引:0,他引:4
In a genetic analysis of the mating system of cooperatively breeding Arabian babblers (Timalidae: Turdoides squamiceps), we identified which individuals in the population are breeding, and how reproductive success was distributed among group
members with respect to their dominance rank, for both males and females. The population was characterized by an asymmetrical
distribution of reproductive success; behaviorally dominant males produced 176 of 186 (95%) of the offspring in 44 social
groups analyzed, and alpha females produced 185 of 186 (99.5%). We evaluated models of reproductive skew by examining genetic
and demographic correlates of reproduction by␣subordinates. Subordinate (beta) males that sired young were more likely to
be recent dispersers from their natal groups or members of newly formed groups than betas that did not reproduce. Breeding
beta males had spent smaller proportions of their lives with the current alpha male and female as alphas than had beta males
that did not sire young. One consequence of the linkage of dispersal with breeding in newly formed, nonnatal groups is that
beta males that sired young had significantly lower genetic similarity to the alpha males in their groups (based on band-sharing
coefficients using multilocus minisatellite DNA fingerprinting) than those that did not sire young. This pattern may occur
generally in species in which group membership accrues both through nondispersal of young (forming groups of relatives) as
well as through dispersal involving coalitions that sometimes include nonrelatives.
Received: 22 July 1997 / Accepted after revision: 5 February 1998 相似文献