1,721,077 research outputs found
Genetic evidence on origin and dispersal of human populations speaking languages of the Nostratic macrofamily
No full textContemporary patterns of allele frequencies
allow inferences on past evolutionary processes. L. L. Cavalli-
Sforza [(1988) Munibe 6, 129-137] and C. Renfrew [(1991)
Cambridge Archaeol. J. 1, 3-23] proposed that neolithic farmers
from the Near East propagated a group of related ancestral
languages, from which three or four linguistic families developed.
Here we show that genetic variation among Indo-
European, Elamo-Dravidian, and Altaic speakers (grouped by
some linguists in the Nostratic macrofamily) supports this
hypothesis, whereas the evidence on Afro-Asiatic speakers is
ambiguous. Gene-frequency climes within these linguistic famiies
suggest that language diffusion was largely associated with
population movements rather than with purely cultural transmission.
Archeological, linguistic, and genetic evidence can be
reconciled by envisagng a process of population growth and
multidirectional dispersal from the Near East as the main
factor shaping genetic and liistic diversity in Eurasia and
perhaps in North Africa
Strategic ejaculate adjustments and mismatches: are males paying sperm senescence costs?
No full textIn many species, males show anticipatory plasticity for sperm production, which they adjust to match perceived mating opportunities. While the strategic adjustment of sperm production is likely to be beneficial, it may be also associated with costs, including those arising from the expression of a phenotype that is poorly matched to the conditions that males will subsequently experience. Mismatch costs are exacerbated by trade-offs between investment in the ejaculate and investment in other traits and by trade-offs among individual ejaculate traits. Trade-offs, in fact, may determine a decrease in male competitiveness, due to impaired ability to obtain copulations or to reduced ejaculate quality. We explored mismatch costs using male guppies, which are known to increase sperm production, but reduce their investment in sexual behaviour, when maintained in the presence of females. Increasing ejaculate size in the absence of females could impose costs that would be paid when an opportunity to mate eventually arises. One of such costs may involve male post-copulatory competitiveness and may be associated with increased sperm senescence. To explore mismatch costs, firstly we induced two groups of males to differentiate their sperm production by exposing them or not to female stimuli. Then, we isolated them to prevent matings and have their sperm ageing. Finally, we compared ejaculate quality between the groups. Contrary to expectations, we found that female-stimulated males did not suffer from increased sperm senescence. These costs are probably minimized by the high level of plasticity associated with this trait, resulting in sperm production being quickly re-adjusted to a new environment. Other types of mismatch costs may be more relevant, for example, those related to trade-offs with sexual behaviour
Exploratory behaviour covaries with preference for unfamiliar males in female guppies
No full textMany animals, from humans to invertebrates, exhibit sexual preference for unfamiliar partners. This may reduce the risk of inbreeding and increase offspring heterozygosity. An alternative less tested hypothesis is that selection for neophilia in other contexts (e.g. exploration of unfamiliar environments) may promote mate preference for unfamiliar partners. We tested whether exploratory tendency covaries with female preference for unfamiliar mates in the guppy, Poecilia reticulata, a species in which exploratory behaviour show significant phenotypic and genetic variation. We measured the exploratory behaviour of females using an unfamiliar environment test. The same females were also tested for preference for an unfamiliar male over a male with which they had spent the previous 24 h. We found that a female's tendency to explore an unfamiliar environment was positively correlated with the strength of her preference for unfamiliar males. Our results support the hypothesis that exploration might play a role in the evolution and maintenance of preference for unfamiliar males via functional pleiotropy
Population-level food availability affects postcopulatory sexual selection dynamics in the guppy
Full text linkPostcopulatory sexual selection (PCSS), namely sperm competition and cryptic female choice, is typically investigated in benign environments, with a fixed number of partners, which mate at the same time intervals; all conditions that are rarely met in natural populations.Although there is increasing evidence that environmental fluctuations affect sexual selection before mating, whether and to which extent they influence postcopulatory trajectories is still little explored.PCSS was investigated in replicate populations of guppies (Poecilia reticulata) in which males and females mated after maintained for 2 weeks on either restricted (RE) or ad libitum (AL) diet and the paternity of the offspring produced by multiply mated females was assigned using microsatellite markers.Compared to AL fish, RE females (i) had fewer mating partners, but the time interval between the first and the last mating was not affected; (ii) produced broods with a lower variance in male fertilization success (a measure of the opportunity for PCSS); and (iii) produced broods with a paternity bias towards the first mate (reversing the last sperm precedence observed in AL populations), and associated more towards males with higher courtship rate.Our results demonstrate that short-term limitation in food availability significantly influence PCSS by modifying both fertilization success variance and sperm precedence pattern. Environmental variation should therefore become part of the research paradigm to improve our understanding of postcopulatory evolutionary dynamics.Read the free Plain Language Summary for this article on the Journal blog
Three early books on birds’ eggs: Marsili’s Danubius Pannonico-Mysicus (1726), Zinanni’s Delle Uova e dei Nidi degli Uccelli (1737) and Klein’s Ova avium plurimarum ad naturalem magnitudinem delineata et genuinis coloribus picta (1766)
No full textThe three earliest – all eighteenth-century – illustrated accounts of birds’ eggs were by Luigi Marsili (or Marsigli): Danubius Pannonico-Mysicus, Giuseppe Zinanni (or Ginanni): Delle Uova e dei Nidi degli Uccelli, and Jacob Theodor Klein: Ova avium plurimarum ad naturalem magnitudinem delineata et genuinis coloribus picta. Marsili’s account describes and illustrates the nests and eggs of just 15 different birds (whose identity is sometimes uncertain), which together with 59 plates of birds forms part of a multi-disciplinary account of the River Danube. Zinanni’s volume (which also includes an appendix on grasshoppers) describes the nests and eggs of 106 birds, and is more extensive and accurate since he shot the adult birds attending nests from which the illustrated eggs were collected. Zinanni’s book includes 34 black-and-white engraved plates each with between one and nine eggs of species that (excluding domesticated or exotic species) were probably those that occurred around his home in north-east Italy. Klein’s volume includes 145 coloured plates of eggs – the first published coloured images of eggs – and his classification of birds based on feet and toes. We present some biographical information and details of each author’s career and a summary of their books’ contents. The text of Zinanni’s volume is the most “philosophical” of the three and includes a discussion – based on the writings of Lorenzo Bellini and Antonio Vallisneri – of what he calls “airways” within the egg that have apparently not been noticed or commented on by subsequent researchers
Trade-offs of strategic sperm adjustments and their consequences under phenotype–environment mismatches in guppies
No full textIn polyandrous species males invest significant resources in producing large and high-quality ejaculates. As ejaculates are costly, males are expected to modulate their investment in response to social cues associated with the expected level of sperm competition or mating opportunity, to anticipate future mating conditions. Another consequence of ejaculate costs is that the increase in ejaculate production may be traded against traits linked to mate acquisition. In such cases, the effect of this anticipatory plasticity in ejaculate investment on a male's reproductive success will depend on the balance between postcopulatory benefits and precopulatory costs in the sociosexual context subsequently encountered. Here, we used the guppy, Poecilia reticulata, a live-bearing fish characterized by intense sperm competition, to investigate how mismatches between anticipatory phenotypes and the social conditions subsequently experienced affect male reproductive success. Male guppies kept in visual contact with females, a social stimulus predicting high mating opportunities, increase their sperm production compared to female-deprived males which foresee fewer opportunities to mate, but simultaneously reduce their courtship rate. Using a paired experimental design, we manipulated the male's perceived mating opportunities by housing them in the presence (FP) or in the absence (FA) of females. We then measured male mating and insemination success under two conditions: (1) a female-biased sex ratio, matching expected FP cues; and (2) a male-biased sex ratio, matching expected FA cues. Under a female-biased sex ratio, mating and insemination success were not affected by previous exposure to females, although FP males experienced a lower risk of sperm depletion after several copulations. However, FP males showed a small, but significant, reduction in their mating success under a male-biased sex ratio, when directly competing with an FA male. Males showed significant repeatability in mating and insemination success within a sex ratio context, suggesting that the costs of mismatching anticipatory ejaculate responses are probably low in this species
Genetic similarity in Long Eared Owl communal winter roosts: a DNA fingerprinting study
No full textThe long-eared owl is a nocturnal predator which winters communally and breeds in the same areas in loose colonies during the spring. We tested the hypothesis that roosts, particularly stable roosts, are formed by close relatives, a condition under which group-related behaviours such as information sharing or helping at nest are more likely to be developed. DNA fingerprinting analysis was used to examine genetic similarity within and between two long-eared owl populations, one wintering in a traditional roost and the other in an unstable roost, and both breeding around their roosting sites. Although genetic similarity within roosts was higher than that between roosts, the difference was not significant. Observed genetic similarity within roosts was smaller than that reported in the bird species whose roosts work as information centres. On the other hand, the presence of some closely related individuals in the roost and behavioural observations suggest that co-operation between kin might have occurred, at least in one of the two study sites
Maternal predator-exposure affects offspring size at birth but not telomere length in a live-bearing fish
Full text linkThe perception of predation risk could affect prey phenotype both within and between generations (via parental effects). The response to predation risk could involve modifications in physiology, morphology, and behavior and can ultimately affect long-term fitness. Among the possible modifications mediated by the exposure to predation risk, telomere length could be a proxy for investigating the response to predation risk both within and between generations, as telomeres can be significantly affected by environmental stress. Maternal exposure to the perception of predation risk can affect a variety of offspring traits but the effect on offspring telomere length has never been experimentally tested. Using a live-bearing fish, the guppy (Poecilia reticulata), we tested if the perceived risk of predation could affect the telomere length of adult females directly and that of their offspring with a balanced experimental setup that allowed us to control for both maternal and paternal contribution. We exposed female guppies to the perception of predation risk during gestation using a combination of both visual and chemical cues and we then measured female telomere length after the exposure period. Maternal effects mediated by the exposure to predation risk were measured on offspring telomere length and body size at birth. Contrary to our predictions, we did not find a significant effect of predation-exposure neither on female nor on offspring telomere length, but females exposed to predation risk produced smaller offspring at birth. We discuss the possible explanations for our findings and advocate for further research on telomere dynamics in ectotherms
Sperm production is negatively associated with muscle and sperm telomere length in a species subjected to strong sperm competition
Full text linkLife-history theory suggests that ageing is one of the costs of reproduction. Accordingly, a higher reproductive allocation is expected to increase the deterioration of both the somatic and the germinal lines through enhanced telomere attrition. In most species, males' reproductive allocation mainly regards traits that increase mating and fertilization success, that is sexually selected traits. In this study, we tested the hypothesis that a higher investment in sexually selected traits is associated with a reduced relative telomere length (RTL) in the guppy (Poecilia reticulata), an ectotherm species characterized by strong pre- and postcopulatory sexual selection. We first measured telomere length in both the soma and the sperm over guppies' lifespan to see whether there was any variation in telomere length associated with age. Second, we investigated whether a greater investment in pre- and postcopulatory sexually selected traits is linked to shorter telomere length in both the somatic and the sperm germinal lines, and in young and old males. We found that telomeres lengthened with age in the somatic tissue, but there was no age-dependent variation in telomere length in the sperm cells. Telomere length in guppies was significantly and negatively correlated with sperm production in both tissues and life stages considered in this study. Our findings indicate that telomere length in male guppies is strongly associated with their reproductive investment (sperm production), suggesting that a trade-off between reproduction and maintenance is occurring at each stage of males' life in this species
Effects of chronic dietary cadmium on hepatic glutathione levels and glutathione peroxidase activity in starlings (Sturnus vulgaris)
No full textThe effects of chronic exposure to dietary cadmium on the levels of hepatic glutathione (GSH) and on the activity of the glutathione peroxidase enzymes (GSH-Px) were studied for the first time in starlings (Sturnus vulgaris). Thirty-three individuals (17 females and 16 males) were divided into three groups: One represented the untreated control and two were respectively fed with diets containing 10 and 50 ppm cadmium chloride (CdCl(2)). The total duration of treatment was 22 weeks. The three groups respectively accumulated mean hepatic Cd residues of 2.29, 75.71, and 208.49 ppm. Hepatic GSH increased in the treated groups respectively 24% and 52% in comparison to controls. Total GSH-Px activity in the liver was inhibited in the group fed with 50 ppm, due to inhibition of the selenium-dependent fraction of the enzyme, while the selenium-independent fraction did not change significantly. During the treatment, after 14 weeks of exposure to cadmium, the 50 ppm-treated group showed a 47% decrease of the activity of the selenium-dependent GSH-Px and a 50% increase of the somatic liver index in comparison with controls
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