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Sökning: WFRF:(Cornwallis Charlie K.)

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1.
  • Hayward, Alexander, et al. (författare)
  • Pan-vertebrate comparative genomics unmasks retrovirus macroevolution
  • 2015
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Acad Sciences. - 0027-8424 .- 1091-6490. - 1091-6490 (Electronic) 0027-8424 (Linking) ; 112:2, s. 464-469
  • Tidskriftsartikel (refereegranskat)abstract
    • Although extensive research has demonstrated host-retrovirus microevolutionary dynamics, it has been difficult to gain a deeper understanding of the macroevolutionary patterns of host-retrovirus interactions. Here we use recent technological advances to infer broad patterns in retroviral diversity, evolution, and host-virus relationships by using a large-scale phylogenomic approach using endogenous retroviruses (ERVs). Retroviruses insert a proviral DNA copy into the host cell genome to produce new viruses. ERVs are provirus insertions in germline cells that are inherited down the host lineage and consequently present a record of past host-viral associations. By mining ERVs from 65 host genomes sampled across vertebrate diversity, we uncover a great diversity of ERVs, indicating that retroviral sequences are much more prevalent and widespread across vertebrates than previously appreciated. The majority of ERV clades that we recover do not contain known retroviruses, implying either that retroviral lineages are highly transient over evolutionary time or that a considerable number of retroviruses remain to be identified. By characterizing the distribution of ERVs, we show that no major vertebrate lineage has escaped retroviral activity and that retroviruses are extreme host generalists, having an unprecedented ability for rampant host switching among distantly related vertebrates. In addition, we examine whether the distribution of ERVs can be explained by host factors predicted to influence viral transmission and find that internal fertilization has a pronounced effect on retroviral colonization of host genomes. By capturing the mode and pattern of retroviral evolution and contrasting ERV diversity with known retroviral diversity, our study provides a cohesive framework to understand host-virus coevolution better.
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  • Bonato, Maud, et al. (författare)
  • Predicting ejaculate quality and libido in male ostriches: Effect of season and age.
  • 2014
  • Ingår i: Animal Reproduction Science. - : Elsevier. - 1873-2232. ; 151:1-2, s. 49-55
  • Tidskriftsartikel (refereegranskat)abstract
    • The success of artificial breeding program depends largely on the reproductive performance of males. Male performance can vary with season and age impacting on quality and quantity of semen collected for artificial insemination purposes and therefore fertility of inseminated females. We examined variation in semen output and male libido of seven male ostriches (aged 2-5 years) over a period of 24 months. We collected ejaculates using a dummy female and measured semen characteristics (ejaculate volume, sperm concentration, number of spermatozoa per ejaculate, sperm motility and morphology) and male libido (willingness to mount the dummy). A total of 1006 ejaculates were collected. Across months, the volume of semen (mean±SEM) ranged from 1.03±0.12mL to 1.85±0.07mL, the sperm concentration from 3.21±0.12×10(9)/mL to 4.16±0.74×10(9)/mL, and the number of spermatozoa from 3.42±0.28×10(9) to 7.66±0.47×10(9). The largest volume of ejaculates and the highest number of sperm were collected in spring. Ejaculates with higher number of normal sperm were also collected in spring-early summer, whereas ejaculates with higher numbers of live abnormal and dead sperm were collected in winter. Sperm motility was relatively constant over months, despite a reduction in summer (January-February), while male libido peaked in winter (June-July) and spring (October-November). Furthermore, we observed high individual variation between males for all variables tested, except for motility. These results indicate that collections conducted in spring yield higher number of spermatozoa, when the libido of males is also at a maximum. Therefore in this species seasonal variation in semen quality should be considered in breeding programmes by artificial insemination to maximise fertility.
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5.
  • Bonato, Maud, et al. (författare)
  • The effect of temperature and pH on the motility and viability of ostrich sperm
  • 2012
  • Ingår i: Animal Reproduction Science. - : Elsevier. - 1873-2232. ; 133:1-2, s. 123-128
  • Tidskriftsartikel (refereegranskat)abstract
    • As the chemical environment of semen diluents can have a profound effect on sperm quality, we examined the effect of temperature and pH on the motility and viability of sperm in the ostrich. Semen was collected from four males, each male being replicated three times. Ejaculates were diluted and incubated for 10 min at 20 degrees C and 40 degrees C in four different buffers, temperature adjusted at pH 6, 7, 8 and 9 respectively. Average path velocity (VAP), curvilinear velocity (VCL), straight-line velocity (VSL), linearity (LIN), beat cross frequency (BCF) and amplitude of lateral displacement (ALH) were then recorded for each sample using CASA. The viability of sperm was assessed using nigrosin-eosin staining. Sperm incubated at 40 degrees C had higher motility parameters, except for ALH. At 40 degrees C, VAP, VSL and LIN increased with pH while VCL, BCF and ALH were higher for lower pHs. The viability of sperm was not affected by temperature but decreased at pH values > 7. A pH in the neutral range appeared to yield higher quality sperm after in vitro storage at 20 degrees C. However, the effect of different pH levels and temperatures on sperm longevity needs to be investigated further to develop viable ostrich specific diluents. (C) 2012 Elsevier B.V. All rights reserved.
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  • Cornwallis, Charlie K., et al. (författare)
  • Cooperation facilitates the colonization of harsh environments
  • 2017
  • Ingår i: Nature Ecology and Evolution. - : Nature Publishing Group. - 2397-334X. ; 1:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Animals living in harsh environments, where temperatures are hot and rainfall is unpredictable, are more likely to breed in cooperative groups. As a result, harsh environmental conditions have been accepted as a key factor explaining the evolution of cooperation. However, this is based on evidence that has not investigated the order of evolutionary events, so the inferred causality could be incorrect. We resolved this problem using phylogenetic analyses of 4,707 bird species and found that causation was in the opposite direction to that previously assumed. Rather than harsh environments favouring cooperation, cooperativebreeding has facilitated the colonization of harsh environments. Cooperative breeding was, in fact, more likely to evolve from ancestors occupying relatively cool environmental niches with predictable rainfall, which had low levels of polyandry and hence high within-group relatedness. We also found that polyandry increased after cooperative breeders invaded harsh environments,suggesting that when helpers have limited options to breed independently, polyandry no longer destabilizes cooperation. This provides an explanation for the puzzling cases of polyandrous cooperative breeding birds. More generally, this illustrates how cooperation can play a key role in invading ecological niches, a pattern observed across all levels of biological organization from cells to animal societies.
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  • Dean, Rebecca, et al. (författare)
  • Male reproductive senescence causes potential for sexual conflict over mating.
  • 2010
  • Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 20:13, s. 1192-6
  • Tidskriftsartikel (refereegranskat)abstract
    • The realization that senescence, age-dependent declines in survival and reproductive performance, pervades natural populations has brought its evolutionary significance into sharper focus. However, reproductive senescence remains poorly understood because it is difficult to separate male and female mechanisms underpinning reproductive success. We experimentally investigated male reproductive senescence in feral fowl, Gallus gallus domesticus, where socially dominant males monopolize access to females and the ejaculates of multiple males compete for fertilization. We detected the signal of senescence on multiple determinants of male reproductive success. The effect of age on status was dependent upon the intensity of intrasexual competition: old males were less likely to dominate male-biased groups where competition is intense but were as likely as young males to dominate female-biased groups. Mating and fertilization success declined sharply with male age largely as a result of population-level patterns. These age-dependent declines translated into sexually antagonistic payoffs: old males fertilized more eggs when they were dominant, but this resulted in females suffering a drastic reduction in fertility. Thus, male senescence causes potential for sexual conflict over mating, and the intensity of this conflict is modulated socially, by the probability of old males dominating reproductive opportunities.
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9.
  • Downing, Philip A., et al. (författare)
  • Group formation and the evolutionary pathway to complex sociality in birds
  • 2020
  • Ingår i: Nature Ecology and Evolution. - : Nature Publishing Group. - 2397-334X. ; 4:3, s. 479-486
  • Tidskriftsartikel (refereegranskat)abstract
    • Group-living species show a diversity of social organization, from simple mated pairs to complex communities of interdependent individuals performing specialized tasks. The advantages of living in cooperative groups are well understood, but why some species breed in small aggregations while others evolve large, complex groups with clearly divided roles is unclear. We address this problem by reconstructing the evolutionary pathways to cooperative breeding across 4,730 bird species. We show that differences in the way groups form at the origin of cooperative breeding predicts the level of group complexity that emerges. Groups that originate through the retention of offspring have a clear reproductive divide with distinct breeder and helper roles. This is associated with reproductive specialization, where breeders invest more in fecundity and less in care. In contrast, groups formed through the aggregation of unrelated adults are smaller and lack specialization. These results help explain why some species have not transitioned beyond simple groups while others have taken the pathway to increased group complexity.
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  • Downing, Philip A., et al. (författare)
  • Hard-working helpers contribute to long breeder lifespans in cooperative birds
  • 2021
  • Ingår i: Philosophical transactions of the Royal Society of London. Series B, Biological sciences. - : Royal Society Publishing. - 1471-2970. ; 376:1823
  • Tidskriftsartikel (refereegranskat)abstract
    • In many species that raise young in cooperative groups, breeders live an exceptionally long time despite high investment in offspring production. How is this possible given the expected trade-off between survival and reproduction? One possibility is that breeders extend their lifespans by outsourcing parental care to non-reproductive group members. Having help lightens breeder workloads and the energy that is saved can be allocated to survival instead. We tested this hypothesis using phylogenetic meta-analysis across 23 cooperatively breeding bird species. We found that breeders with helpers had higher rates of annual survival than those without helpers (8% on average). Increased breeder survival was correlated with reduced investment in feeding offspring, which in turn depended on the proportion of feeding provided by helpers. Helpers had similar effects on female and male breeder survival. Our results indicate that one of the secrets to a long life is reduced investment in parental care. This appears to be a unique feature of cooperative societies with hard-working helpers. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'
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