Genome sequences of 31 mycobacteriophages isolated on Mycobacterium smegmatis mc2155 at room temperature

We report the genome sequences of 31 mycobacteriophages isolated on Mycobacterium smegmatis mc2155 at room temperature. The genomes add to the diversity of Clusters A, B, C, G, and K. Collectively, the genomes include 70 novel protein-coding genes that have no close relatives among the actinobacteriophages.

Lifetime inclusive fitness effects of cooperative polygamy in the acorn woodpecker

Although over 50 y have passed since W. D. Hamilton articulated kin selection and inclusive fitness as evolutionary explanations for altruistic behavior, quantifying inclusive fitness continues to be challenging. Here, using 30 y of data and two alternative methods, we outline an approach to measure lifetime inclusive fitness effects of cooperative polygamy (mate-sharing or cobreeding) in the cooperatively breeding acorn woodpecker Melanerpes formicivorus. For both sexes, the number of offspring (observed direct fitness) declined while the number of young parented by related cobreeders (observed indirect fitness effect) increased with cobreeding coalition size. Combining these two factors, the observed inclusive fitness effect of cobreeding was greater than breeding singly for males, while the pattern for females depended on whether fitness was age-weighted, as females breeding singly accrued greater fitness at younger ages than cobreeding females. Accounting for the fitness birds would have obtained by breeding singly, however, lifetime inclusive fitness effects declined with coalition size for males, but were greater for females breeding as duos compared to breeding singly, due largely to indirect fitness effects of kin. Our analyses provide a road map for, and demonstrate the importance of, quantifying indirect fitness as a powerful evolutionary force contributing to the costs and benefits of social behaviors.

Are you my baby? Testing whether paternity affects behavior of cobreeder male acorn woodpeckers

Natural selection is expected to favor males that invest more in offspring they sire. We investigated the relationship between paternity and male behavior in the acorn woodpecker (Melanerpes formicivorus), a cooperative breeder that lives in family groups including offspring that remain on their natal territory, sometimes for years, and cobreeders of both sexes. Regardless of group composition, only one communal nest is attended at a time. Whereas cobreeding females share maternity equally, one male usually sires the majority of young in the group’s communal nest. Copulations are rarely observed, and thus it has not been possible to link paternity to sexual behavior. There were no differences among cobreeder males that did or did not sire young in their propensity to roost in the nest cavity at night. However, cobreeder males that attended females continuously prior to egg-laying were more likely to successfully sire young than males that did not, and the relative share of feeding visits and time spent at the subsequent nest were positively related to a male’s realized paternity. These differences in male behavior were partly due to differences among males and partly to plasticity in male behavior covarying with paternity share. Feedings by males successfully siring young also involved a larger proportion of nutritionally valuable insect prey. Males are aware of their paternity success, apparently because of their relative access to females prior to egg laying, and provide more paternal care at nests in which they are more likely to have sired young.

Lifetime reproductive benefits of cooperative polygamy vary for males and females in the acorn woodpecker (Melanerpes formicivorus)

Cooperative breeding strategies lead to short-term direct fitness losses when individuals forfeit or share reproduction. The direct fitness benefits of cooperative strategies are often delayed and difficult to quantify, requiring data on lifetime reproduction. Here, we use a longitudinal dataset to examine the lifetime reproductive success of cooperative polygamy in acorn woodpeckers (Melanerpes formicivorus), which nest as lone pairs or share reproduction with same-sex cobreeders. We found that males and females produced fewer young per successful nesting attempt when sharing reproduction. However, males nesting in duos and trios had longer reproductive lifespans, more lifetime nesting attempts and higher lifetime reproductive success than those breeding alone. For females, cobreeding in duos increased reproductive lifespan so the lifetime reproductive success of females nesting in duos was comparable to those nesting alone and higher than those nesting in trios. These results suggest that for male duos and trios, reproductive success alone may provide sufficient fitness benefits to explain the presence of cooperative polygamy, and the benefits of cobreeding as a duo in females are higher than previously assumed. Lifetime individual fitness data are crucial to reveal the full costs and benefits of cooperative polygamy.

Habitat Saturation Results in Joint-Nesting Female Coalitions in a Social Bird

Joint nesting by females and cooperative polyandry-cooperatively breeding groups with a male-biased breeder sex ratio-are little-understood, rare breeding systems. We tested alternative hypotheses of factors potentially driving these phenomena in a population of joint-nesting acorn woodpeckers (Melanerpes formicivorus). During periods of high population density and thus low independent breeding opportunities, acorn woodpecker females formed joint-nesting coalitions with close kin. Coalitions were typically associated with groups with a male bias. We found strong evidence for both inter- and intrasexual conflict, as joint nesting conferred a fitness benefit to some males, a significant fitness cost to females, and no gain in per capita reproductive output for either sex. Such conflict, particularly the cost to females, may be an important reason why joint nesting is rare among cooperatively breeding taxa.

Reproductive roles in the cooperatively breeding acorn woodpecker: incest avoidance versus reproductive competition

Incest is rare in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus) despite a polygynandrous mating system in which nearly all group members are close relatives. Here we test the relative importance of avoiding matings between close relatives (incest avoidance) and within-sex competition for breeding opportunities (reproductive competition) in determining the mating system of acorn woodpeckers by examining how reproductive roles change following breeding vacancies. In 83% of cases in which helpers of the same sex were present in the group, reproductive vacancies were resolved when new unrelated immigrants filled the vacancy to the exclusion of resident same-sex helpers, who generally emigrated or did not breed while they remained in the group. Helpers of the opposite sex, especially when male, were significantly more likely to remain in their natal group and in about half the cases inherited and bred following reproductive vacancies. This result was not explainable by reproductive competition, since the number of immigrants was often less than or equal to the number of same-sex helpers in the group. Apparent incest resulted in 5% of cases. The time required to resolve reproductive vacancies was significantly longer for groups with helpers of the same sex as the vacancy. These results confirm that both incest avoidance and reproductive competition are important factors determining reproductive roles within groups of this highly social species.

Patterns of reproductive skew in the polygynandrous acorn woodpecker

We compared observed levels of reproductive skew in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus) with those predicted by two alternative transactional models. "Concession" models predict the degree to which parentage is shared assuming that a single dominant is in complete control of reproduction. Alternatively, "restraint" models predict reproductive sharing assuming that the dominant controls only whether subordinates remain in the group but does not control its share of reproduction. Reproductive skew is high among males: on average, the most successful male sires more than three times as many offspring as the next most successful male. Females share parentage equally and have lower constraints on dispersal and lower survival rates compared with males, which is consistent with predictions from the concessions model. Also as predicted by the concessions model, yearly variation in opportunities for dispersal before the breeding season correlates positively with skew. However, in contrast to concessions but consistent with the restraint model, skew decreases with relatedness. Thus, neither model consistently predicts patterns of reproductive skew in this species. We suggest that models of reproductive skew will need to include competitive interactions among potential breeders and mate choice before they will adequately predict patterns of reproductive partitioning in most vertebrate societies.

Reproductive skew in the polygynandrous acorn woodpecker

Reproductive skew models, which focus on the degree to which reproduction is shared equally (low skew) or monopolized by a single individual (high skew) within groups, have been heralded as providing a general unifying framework for understanding the factors determining social evolution. Here, we test the ability of optimal skew, or "transactional," models, which predict the level of skew necessary to promote stable associations of dominants and subordinates, rather than independent breeding, to predict reproductive partitioning in the acorn woodpecker (Melanerpes formicivorus). This species provides a key test case because only a few vertebrates exhibit polygynandry (multiple breeders of both sexes within a group). Contrary to the predictions of the models, joint-nesting females share reproduction more equitably than expected, apparently because egg destruction and the inability of females to defend their eggs from cobreeders eliminate any possibility for one female to control reproduction. For males, however, reproductive skew is high, with the most successful male siring over three times as many young as the next most successful male. Although this result is consistent with optimal skew models, other aspects of male behavior are not; in particular, the reproductively most successful male frequently switches between nests produced by the same set of cobreeders, and we were unable to detect any phenotypic correlate of success. These results are consistent with an alternative null model in which cobreeder males have equal chance of paternity, but paternity of offspring within broods is nonindependent as a consequence of female, rather than male, control.

Shared parentage and incest avoidance in the cooperatively breeding acorn woodpecker

Social groups of acorn woodpeckers (Melanerpes formicivorus) range in size from unaided pairs to 15 adults. Behavioural indicators of mate guarding, assumed incest avoidance and observations of egg-laying indicate that social organization ranges from monogamous pairs to groups with up to seven male and three female putative cobreeders plus up to 10 nonbreeding helpers. In addition, groups occasionally lack a putative breeder throughout the breeding season. Here we report results from multilocus DNA fingerprinting of 372 nestlings from 123 nests in groups with putative cobreeders of one or both sexes. No extra-group fertilizations were found. Putative cobreeding males within social groups shared paternity. However, the most reproductively successful male was, on average, almost three times as successful as the next most successful and additional males only occasionally sired offspring. In contrast, cobreeding females shared parentage equally. Helpers never bred incestuously when their opposite-sex parent (or another relative, such as their uncle) held breeding status in the group. However, during breeding male vacancies, 14 nestlings were produced when helper males bred incestuously with their mother. Both male and female helpers usually became successful cobreeders with their same-sex parent following replacement of the opposite-sex breeder(s) by unrelated individuals.

Demographic consequences of incest avoidance in the cooperatively breeding acorn woodpecker

The avoidance of breeding with close relatives is an adaptation to inbreeding depression. Unfortunately, inbreeding depression has proved difficult to document or measure in the wild, despite being frequently observed among animals in captivity. We address this problem indirectly by determining the demographic cost of incest avoidance in the cooperatively breeding, polygynandrous acorn woodpecker, Melanerpes formicivorus, following the death or disappearance of all breeders of one sex within a group (a reproductive vacancy). Groups undergoing female vacancies that also contained female nonbreeding helpers experienced significantly lower reproductive success in each of the subsequent 3 years than those in which either no nonbreeding helpers or only male nonbreeding helpers were present, a decrease attributable to incest avoidance between the helper females and the related breeder males in the group. Using a computer simulation combined with a life-table analysis, we estimated that incest avoidance costs the population 9.2-12.1% in overall reproductive potential (measured in fledglings/female) and decreases the population rate of increase by 1.78-2.33%/year. These results suggest the presence, on average, of at least 1.2-1.8 lethal equivalents per individual, a value of the same magnitude as estimated for several other taxa, including humans. Incest avoidance may compound random demographic and environmental events and significantly facilitate the decline of threatened populations even prior to any detrimental effects of inbreeding depression per se. Copyright 1999 The Association for the Study of Animal Behaviour.