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1.
BMC Ecol ; 20(1): 70, 2020 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-33334346

RESUMO

BACKGROUND: Earlier breeding is one of the strongest responses to global change in birds and is a key factor determining reproductive success. In most studies of climate effects, the focus has been on large-scale environmental indices or temperature averaged over large geographical areas, neglecting that animals are affected by the local conditions in their home ranges. In riverine ecosystems, climate change is altering the flow regime, in addition to changes resulting from the increasing demand for renewable and clean hydropower. Together with increasing temperatures, this can lead to shifts in the time window available for successful breeding of birds associated with the riverine habitat. Here, we investigated specifically how the environmental conditions at the territory level influence timing of breeding in a passerine bird with an aquatic lifestyle, the white-throated dipper Cinclus cinclus. We relate daily river discharge and other important hydrological parameters, to a long-term dataset of breeding phenology (1978-2015) in a natural river system. RESULTS: Dippers bred earlier when winter river discharge and groundwater levels in the weeks prior to breeding were high, and when there was little snow in the catchment area. Breeding was also earlier at lower altitudes, although the effect dramatically declined over the period. This suggests that territories at higher altitudes had more open water in winter later in the study period, which permitted early breeding also here. Unexpectedly, the largest effect inducing earlier breeding time was territory river discharge during the winter months and not immediately prior to breeding. The territory river discharge also increased during the study period. CONCLUSIONS: The observed earlier breeding can thus be interpreted as a response to climate change. Measuring environmental variation at the scale of the territory thus provides detailed information about the interactions between organisms and the abiotic environment.


Assuntos
Hidrologia , Passeriformes , Animais , Cruzamento , Mudança Climática , Ecossistema
2.
Oecologia ; 184(4): 917-929, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28756488

RESUMO

In migratory birds, mistimed arrival might have negative consequences for individual fitness, causing population declines. This may happen if arrival time is not synchronized with breeding time, especially when earlier springs favour earlier reproduction. We studied spring arrival time to the breeding areas in a pied flycatcher Ficedula hypoleuca population in southern Norway during a 30-year period (1985-2014). We investigated trends in arrival both for the entire population and for different population fractions (e.g. early vs. late arrivals). We also studied sex and age class differences, along with repeatability of arrival. Finally, we explored how arrival is influenced by environmental conditions at the areas birds use throughout the year, using mixed-effects models and quantile regressions with individual-based data. Spring arrival advanced over five days, at a similar rate through the entire population. Males and adult birds arrived earlier than females and yearlings. Arrival was significantly repeatable for males and females. Birds arrived earlier in years with high temperature and rainfall at the breeding grounds, and low NDVI both on the Iberian Peninsula and in central Europe. Later fractions of the population showed a steeper response to these environmental variables. This intra-population heterogeneity in the responses to the environment probably stems from a combination between the different selection pressures individuals are subject to and their age-related experience. Our results highlight the importance of studying how migration phenology is affected by the environment not only on the breeding grounds but also on the other areas birds use throughout the year.


Assuntos
Migração Animal , Passeriformes , Reprodução , Migração Animal/fisiologia , Animais , Cruzamento , Clima , Mudança Climática , Europa (Continente) , Feminino , Estudos Longitudinais , Masculino , Noruega , Reprodução/fisiologia , Estações do Ano
3.
Sci Adv ; 3(2): e1602298, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28164157

RESUMO

Climate change will affect the population dynamics of many species, yet the consequences for the long-term persistence of populations are poorly understood. A major reason for this is that density-dependent feedback effects caused by fluctuations in population size are considered independent of stochastic variation in the environment. We show that an interplay between winter temperature and population density can influence the persistence of a small passerine population under global warming. Although warmer winters favor an increased mean population size, density-dependent feedback can cause the local population to be less buffered against occasional poor environmental conditions (cold winters). This shows that it is essential to go beyond the population size and explore climate effects on the full dynamics to elaborate targeted management actions.


Assuntos
Aquecimento Global , Modelos Biológicos , Dinâmica Populacional , Estações do Ano , Humanos
4.
Ecol Evol ; 6(5): 1363-77, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26855769

RESUMO

Divergent sexual selection within allopatric populations may result in divergent sexual phenotypes, which can act as reproductive barriers between populations upon secondary contact. This hypothesis has been most tested on traits involved in precopulatory sexual selection, with less work focusing on traits that act after copulation and before fertilization (i.e., postcopulatory prezygotic traits), particularly in internally fertilizing vertebrates. However, postcopulatory sexual selection within species can also drive trait divergence, resulting in reduced performance of heterospecific sperm within the female reproductive tract. Such incompatibilities, arising as a by-product of divergent postcopulatory sexual selection in allopatry, can represent reproductive barriers, analogous to species-assortative mating preferences. Here, we tested for postcopulatory prezygotic reproductive barriers between three pairs of taxa with diverged sperm phenotypes and moderate-to-high opportunity for postcopulatory sexual selection (barn swallows Hirundo rustica versus sand martins Riparia riparia, two subspecies of bluethroats, Luscinia svecica svecica versus L. s. namnetum, and great tits Parus major versus blue tits Cyanistes caeruleus). We tested sperm swimming performance in fluid from the outer reproductive tract of females, because the greatest reduction in sperm number in birds occurs as sperm swim across the vagina. Contrary to our expectations, sperm swam equally well in fluid from conspecific and heterospecific females, suggesting that postcopulatory prezygotic barriers do not act between these taxon pairs, at this stage between copulation and fertilization. We therefore suggest that divergence in sperm phenotypes in allopatry is insufficient to cause widespread postcopulatory prezygotic barriers in the form of impaired sperm swimming performance in passerine birds.

5.
PLoS One ; 8(12): e82886, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24391725

RESUMO

BACKGROUND: Climate change potentially has important effects on distribution, abundance, transmission and virulence of parasites in wild populations of animals. METHODOLOGY/PRINCIPAL FINDING: Here we analyzed paired information on 89 parasite populations for 24 species of bird hosts some years ago and again in 2010 with an average interval of 10 years. The parasite taxa included protozoa, feather parasites, diptera, ticks, mites and fleas. We investigated whether change in abundance and prevalence of parasites was related to change in body condition, reproduction and population size of hosts. We conducted analyses based on the entire dataset, but also on a restricted dataset with intervals between study years being 5-15 years. Parasite abundance increased over time when restricting the analyses to datasets with an interval of 5-15 years, with no significant effect of changes in temperature at the time of breeding among study sites. Changes in host body condition and clutch size were related to change in temperature between first and second study year. In addition, changes in clutch size, brood size and body condition of hosts were correlated with change in abundance of parasites. Finally, changes in population size of hosts were not significantly related to changes in abundance of parasites or their prevalence. CONCLUSIONS/SIGNIFICANCE: Climate change is associated with a general increase in parasite abundance. Variation in laying date depended on locality and was associated with latitude while body condition of hosts was associated with a change in temperature. Because clutch size, brood size and body condition were associated with change in parasitism, these results suggest that parasites, perhaps mediated through the indirect effects of temperature, may affect fecundity and condition of their hosts. The conclusions were particularly in accordance with predictions when the restricted dataset with intervals of 5-15 years was used, suggesting that short intervals may bias findings.


Assuntos
Aves/parasitologia , Mudança Climática , Interações Hospedeiro-Patógeno , Animais , Aves/fisiologia , Europa (Continente) , Feminino , Aquecimento Global , Masculino , Dinâmica Populacional , Reprodução , Fatores de Tempo
6.
Horm Behav ; 63(1): 166-72, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23063536

RESUMO

Plasma testosterone can play an important role in promoting aggressive behaviors relating to territory defense in breeding male birds. Some birds defend territories also during the non-breeding phase, when testosterone circulates at basal levels. In such species, plasma levels of the pro-hormone dehydroepiandrosterone (DHEA) may support non-breeding territoriality by acting as a local substrate for sex steroids. To test this possible role of plasma DHEA, we examined the seasonal DHEA profile of male (and female) European nuthatches Sitta europaea: a male and female nuthatch pair will defend an all-purpose territory throughout the year. We hypothesized that plasma DHEA would be detectable in wintering nuthatches with a territory. However, only ca. half of the territorial wintering males (and females) displayed detectable DHEA levels, suggesting that plasma DHEA is not a major sex steroid precursor during non-breeding. Further, among hatching-year birds, plasma DHEA was significantly lower in territorial birds than in "floaters", i.e., subordinate birds without a territory. To experimentally examine the role of DHEA in non-breeding territoriality, we treated adult wintering males with DHEA and measured effects on aggressive responses to conspecific challenge. DHEA treatment elevated plasma levels of DHEA (and testosterone), but did not enhance territorial behaviors or their persistence. Taken together, our data suggest that DHEA (and, indeed, sex steroids per se) do not regulate non-breeding territoriality in the nuthatch. Given that territorial aggression in nuthatches is expressed year-round, a hormone for its activation may be redundant.


Assuntos
Agressão/fisiologia , Comportamento Animal/fisiologia , Desidroepiandrosterona/sangue , Passeriformes/fisiologia , Territorialidade , Agressão/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Desidroepiandrosterona/farmacologia , Feminino , Masculino , Passeriformes/sangue , Estações do Ano , Fatores Sexuais , Testosterona/sangue
7.
Oecologia ; 172(1): 93-107, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23073637

RESUMO

In birds with bi-parental care, the provisioning link between prey capture and delivery to dependent offspring is regarded as often symmetric between the mates. However, in raptors, the larger female usually broods and feeds the nestlings, while the smaller male provides food for the family, assisted by the female in the latter part of the nestling period, if at all. Prey items are relatively large and often impossible for nestlings to handle without extended maternal assistance. We video-recorded prey delivery and handling in nests of a raptor with a wide diet, the Eurasian kestrel Falco tinnunculus, and simultaneously observed prey transfer from male to female outside the nest. The male selectively allocated larger items, in particular birds and larger mammals, to the female for further processing and feeding of nestlings, and smaller items, in particular lizards and smaller mammals, directly to the nestlings for unassisted feeding. Hence, from the video, the female appeared to have captured larger prey than the male, while in reality no difference existed. The female's size-biased interception of the male's prey provisioning line would maximize the male's foraging time, and maximize the female's control of the allocation of food between her own need and that of the offspring. The male would maximize his control of food allocation by capturing smaller prey. This conflict would select for larger dominant females and smaller energy-efficient males, and induce stronger selection the longer the female depends on the male for self-feeding, as a proportion of the offspring dependence period.


Assuntos
Evolução Biológica , Comportamento Alimentar , Comportamento de Nidação , Aves Predatórias/fisiologia , Animais , Conflito Psicológico , Feminino , Masculino , Comportamento Materno , Comportamento Paterno , Comportamento Predatório , Aves Predatórias/anatomia & histologia , Caracteres Sexuais
8.
PLoS One ; 7(8): e43944, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22937131

RESUMO

The seasonal timing of avian reproduction is supposed primarily to coincide with favourable feeding conditions. Long-term changes in avian breeding phenology are thus mostly scrutinized in relation to climatic factors and matching of the food supplies, while the role of nesting mortality is largely unexplored. Here we show that higher seasonal mean daily mortality rate leads to a shift in the distribution of breeding times of the successful nests to later dates in an an open-nesting passerine bird, the red-backed shrike Lanius collurio. The effect appeared to be strong enough to enhance or counteract the influence of climatic factors and breeding density on the inter-annual variation in mean hatching dates. Moreover, the seasonal distribution of reproductive output was shifted to larger, or smaller, broods early in the season when the nesting mortality increased, or decreased, respectively, during the season. We suggest that population level changes in timing of breeding caused by a general advancement of spring and of the food supplies might be altered by the seasonality in nesting mortality. Hence, we argue that consideration of nesting mortality is of major importance for understanding long-term trends in avian phenology, particularly in species capable of renesting.


Assuntos
Corvos/fisiologia , Comportamento de Nidação/fisiologia , Reprodução/fisiologia , Animais , Cruzamento , Dinâmica Populacional , Estações do Ano
9.
PLoS One ; 7(2): e32611, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22384277

RESUMO

There is growing evidence that post-copulatory sexual selection, mediated by sperm competition, influences the evolution of sperm phenotypes. Evidence for pre-copulatory sexual selection effects on sperm traits, on the other hand, is rather scarce. A recent paper on the pied flycatcher, Ficedula hypoleuca, reported phenotypic associations between sperm length and two sexually selected male traits, i.e. plumage colour and arrival date, thus invoking pre-copulatory sexual selection for longer sperm. We were unable to replicate these associations with a larger data set from the same and two additional study populations; sperm length was not significantly related to either male plumage colour or arrival date. Furthermore, there was no significant difference in sperm length between populations despite marked differences in male plumage colour. We also found some evidence against the previously held assumption of longer sperm being qualitatively superior; longer sperm swam at the same speed as shorter sperm, but were less able to maintain speed over time. We argue that both empirical evidence and theoretical considerations suggest that the evolution of sperm morphology is not primarily associated with pre-copulatory sexual selection on male secondary sexual traits in this or other passerine bird species. The relatively large between-male variation in sperm length in this species is probably due to relaxed post-copulatory sexual selection.


Assuntos
Preferência de Acasalamento Animal , Comportamento Sexual Animal , Espermatozoides/fisiologia , Animais , Biodiversidade , Evolução Biológica , Feminino , Masculino , Modelos Biológicos , Modelos Estatísticos , Passeriformes/genética , Fenótipo , Seleção Genética , Motilidade Espermática
10.
J Anim Ecol ; 81(4): 926-36, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22356622

RESUMO

1. Climate warming has led to shifts in the seasonal timing of species. These shifts can differ across trophic levels, and as a result, predator phenology can get out of synchrony with prey phenology. This can have major consequences for predators such as population declines owing to low reproductive success. However, such trophic interactions are likely to differ between habitats, resulting in differential susceptibility of populations to increases in spring temperatures. A mismatch between breeding phenology and food abundance might be mitigated by dietary changes, but few studies have investigated this phenomenon. Here, we present data on nestling diets of nine different populations of pied flycatchers Ficedula hypoleuca, across their breeding range. This species has been shown to adjust its breeding phenology to local climate change, but sometimes insufficiently relative to the phenology of their presumed major prey: Lepidoptera larvae. In spring, such larvae have a pronounced peak in oak habitats, but to a much lesser extent in coniferous and other deciduous habitats. 2. We found strong seasonal declines in the proportions of caterpillars in the diet only for oak habitats, and not for the other forest types. The seasonal decline in oak habitats was most strongly observed in warmer years, indicating that potential mismatches were stronger in warmer years. However, in coniferous and other habitats, no such effect of spring temperature was found. 3. Chicks reached somewhat higher weights in broods provided with higher proportions of caterpillars, supporting the notion that caterpillars are an important food source and that the temporal match with the caterpillar peak may represent an important component of reproductive success. 4. We suggest that pied flycatchers breeding in oak habitats have greater need to adjust timing of breeding to rising spring temperatures, because of the strong seasonality in their food. Such between-habitat differences can have important consequences for population dynamics and should be taken into account in studies on phenotypic plasticity and adaptation to climate change.


Assuntos
Mudança Climática , Dieta , Ecossistema , Reprodução , Aves Canoras/fisiologia , Adaptação Fisiológica , Animais , Europa (Continente) , Cadeia Alimentar , Larva/fisiologia , Lepidópteros/fisiologia , Federação Russa , Estações do Ano , Temperatura , Fatores de Tempo
11.
Gen Comp Endocrinol ; 174(2): 219-24, 2011 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-21925180

RESUMO

In captivity, the adrenocortical stress response can be permanently altered by events that occur during early life. Free-living animals have rarely been examined in this regard. To examine whether early-life events impact the hypothalamo-pituitary-adrenal (HPA) axis in the natural setting, we evaluated the stress response of free-living interspecifically cross-fostered great tits (Parus major). Cross-fostered birds may show a long-term potentiation of the adrenocortical stress response because species-specific nutritional requirements may not be met in the nest and/or cross-fostered birds may experience psychosocial stress while being raised by heterospecifics. Nevertheless, we hypothesized that in the natural setting, programmed changes in HPA function would be eclipsed by reactive responses to the immediate environment. Thus, we predicted that adult cross-fostered great tits and controls would show no differences in their adrenocortical stress response. Contrary to predictions, we found that stress responsiveness (i.e., the rate of the corticosterone increase associated with capture and handling) was significantly higher in cross-fostered great tits than in controls. Further, stress responsiveness was not significantly different between mature adults and first-year juveniles. Thus, data indicate significant effects of early rearing conditions on adrenocortical reactivity in the natural setting and also suggest that effects of rearing conditions in free-living animals can last into adulthood.


Assuntos
Corticosterona/metabolismo , Sistema Hipófise-Suprarrenal/metabolismo , Glândulas Suprarrenais/metabolismo , Animais , Aves , Feminino , Sistema Hipotálamo-Hipofisário/metabolismo , Masculino , Estresse Fisiológico/fisiologia
12.
Int J Biometeorol ; 55(6): 797-804, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21710281

RESUMO

To study the ecological and evolutionary effects of climate change on timing of annual events, scientists need access to data that have been collected over long time periods. High-quality long-term phenology data are rare and costly to obtain and there is therefore a need to extract this information from other available data sets. Many long-term studies on breeding birds include detailed information on individually marked parents and offspring, but do not include information on timing of breeding. Here, we demonstrate how a study of repeated standard measurements of white-throated dipper Cinclus cinclus nestlings in our study system in southernmost Norway can be used for modeling nestling growth, and how this statistical model can be used to estimate timing of breeding for birds with sparser data. We also evaluate how the accuracies of nestling growth models based on different morphological traits (mass and feather length) differ depending on the nestling age, present user guidelines and demonstrate how they can be applied to an independent data set. In conclusion, the approach presented is likely to be useful for a wide variety of species, even if the preferred measurement may differ between species.


Assuntos
Evolução Biológica , Ecossistema , Comportamento de Nidação/fisiologia , Passeriformes/fisiologia , Animais , Peso Corporal , Cruzamento , Mudança Climática , Modelos Biológicos , Modelos Estatísticos , Noruega , Passeriformes/crescimento & desenvolvimento , Fatores de Tempo
13.
Philos Trans R Soc Lond B Biol Sci ; 366(1567): 969-77, 2011 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-21357219

RESUMO

We briefly review the literature on social learning in birds, concluding that strong evidence exists mainly for predator recognition, song, mate choice and foraging. The mechanism of local enhancement may be more important than imitation for birds learning to forage, but the former mechanism may be sufficient for faithful transmission depending on the ecological circumstances. To date, most insights have been gained from birds in captivity. We present a study of social learning of foraging in two passerine birds in the wild, where we cross-fostered eggs between nests of blue tits, Cyanistes caeruleus and great tits, Parus major. Early learning causes a shift in the foraging sites used by the tits in the direction of the foster species. The shift in foraging niches was consistent across seasons, as showed by an analysis of prey items, and the effect lasted for life. The fact that young birds learn from their foster parents, and use this experience later when subsequently feeding their own offspring, suggests that foraging behaviour can be culturally transmitted over generations in the wild. It may therefore have both ecological and evolutionary consequences, some of which are discussed.


Assuntos
Ecossistema , Comportamento Alimentar , Aprendizagem , Passeriformes/fisiologia , Comportamento Social , Distribuição por Idade , Animais
14.
Med Hypotheses ; 76(6): 901-4, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21440376

RESUMO

The initial evolutionary electromagnetic steps in the history of brain development are still unknown, although such knowledge might be of high relevance in understanding human degenerative diseases. All prokaryote organisms, one-celled or multicellular, must have an inherited system to process and store information activating instincts and reflexes, in order to give a quick response to external stimuli. We argue that magnetite is an obvious compound to be evaluated as an initial precursor from prebiotic Earth history in the evolution of such a system. Magnetite is a stable ferrimagnetic compound, present in organisms ranging from bacteria to humans. It occurred naturally in the early Earth environment and was later synthesized de novo in biotic organisms. We suggest that the use of magnetite has evolved to represent the main storage system for learned memory in all organisms living today.


Assuntos
Evolução Biológica , Encéfalo/crescimento & desenvolvimento , Óxido Ferroso-Férrico , Fenômenos Fisiológicos Bacterianos , Biofilmes , Humanos
15.
J Anim Ecol ; 80(1): 235-43, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20880020

RESUMO

1. Climate change may have profound consequences for many organisms. We have studied fluctuations in a population of the white-throated dipper Cinclus cinclus during 31 years (1978-2008) in a river system in southern Norway in relation to both large-scale and local weather conditions occurring during the non-breeding season. 2. Multiple regression and partial least squares regression were used to model the growth rate of the population, accounting for population size in the previous year. 3. Population growth was influenced by North Atlantic Oscillation (NAO), mean winter temperature, precipitation and timing of ice formation on the main lake in the river system in autumn. These variables explained 84% of the variation in population growth over the 31-year study period. 4. Local winter conditions played a prominent role in explaining the population fluctuations, which is plausible because the dipper depends on open water for foraging. In the study area, winters can be harsh and rivers and lakes may freeze and severely affect the subsequent population size of the dipper in spring. 5. The breeding population of the dipper does not seem yet to have reached a level where all possible territories in the area have been occupied, even after mild winters, and the estimated carrying capacity is also decidedly lower (66 breeding pairs) than the number of available territories. If the trend of milder winters continues, the population might increase in the future. However, strong climate variation is expected to continue in the future, and hence periods of rapid growth of the dipper population will probably be followed by severe declines.


Assuntos
Mudança Climática , Passeriformes/fisiologia , Animais , Ecossistema , Gelo , Dinâmica Populacional , Chuva , Estações do Ano , Temperatura , Fatores de Tempo
16.
Horm Behav ; 58(2): 317-25, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20211184

RESUMO

Plasma testosterone increases during breeding in many male vertebrates and has long been implicated in the promotion of aggressive behaviors relating to territory and mate defense. Males of some species also defend territories outside of the breeding period. For example, the European nuthatch (Sitta europaea) defends an all-purpose territory throughout the year. To contribute to the growing literature regarding the hormonal correlates of non-breeding territoriality, we investigated the seasonal testosterone and corticosterone profile of male (and female) nuthatches and determined how observed hormone patterns relate to expression of territorial aggression. Given that non-breeding territoriality in the nuthatch relates to the reproductive context (i.e., defense of a future breeding site), we predicted that males would exhibit surges in plasma testosterone throughout the year. However, we found that males showed elevated testosterone levels only during breeding. Thus, testosterone of gonadal origin does not appear to be involved in the expression of non-breeding territoriality. Interestingly, territorial behaviors of male nuthatches were stronger in spring than in autumn, suggesting that in year-round territorial species, breeding-related testosterone elevations may upregulate male-male aggression above non-breeding levels. In females, plasma testosterone was largely undetectable. We also examined effects of simulated territorial intrusions (STIs) on testosterone and corticosterone levels of breeding males. We found that STIs did not elicit a testosterone response, but caused a dramatic increase in plasma corticosterone. These data support the hypothesis that corticosterone rather than testosterone may play a role in the support of behavior and/or physiology during acute territorial encounters in single-brooded species.


Assuntos
Corticosterona/sangue , Passeriformes , Estações do Ano , Comportamento Social , Territorialidade , Testosterona/sangue , Agressão/fisiologia , Análise de Variância , Animais , Animais Selvagens , Feminino , Voo Animal , Masculino , Passeriformes/sangue , Análise de Componente Principal , Reprodução/fisiologia , Caracteres Sexuais , Fatores de Tempo , Vocalização Animal
17.
Biol Lett ; 5(1): 58-61, 2009 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-18986959

RESUMO

Theories regarding the role of sexual selection on the evolution of sperm traits are based on an association between pre-copulatory (e.g. female preference) and post-copulatory (e.g. ejaculate quality) male reproductive traits. In tests of these hypotheses, sperm morphology has rarely been used, despite its high heritability and intra-individual consistency. We found evidence of selection for longer sperm through positive phenotypic associations between sperm size and the two major female preference traits in the pied flycatcher, Ficedula hypoleuca. Our results support the sexually selected sperm hypothesis in a species under low sperm competition and demonstrate that natural and pre-copulatory sexual selection forces should not be overlooked in studies of intraspecific sperm morphology evolution.


Assuntos
Passeriformes/genética , Seleção Genética , Espermatozoides/citologia , Animais , Masculino , Preferência de Acasalamento Animal , Passeriformes/anatomia & histologia , Passeriformes/fisiologia
18.
Physiol Biochem Zool ; 80(2): 228-40, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17252519

RESUMO

The "challenge hypothesis" posits that when established social orders are challenged, plasma testosterone (T) in socially monogamous breeding male birds will temporarily increase to facilitate aggressive responses. However, not all birds conform to predictions. To expand upon past findings, we examined effects of direct territorial challenge on T levels in the blue tit (Cyanistes caeruleus). We found that simulated territorial intrusions caused a decline in plasma T during both territory establishment and laying/incubation. Conversely, corticosterone (CORT) levels dramatically increased. We also examined challenged blue tit males for levels of corticosterone-binding globulin (CBG), a carrier molecule that displays affinity for both CORT and T in birds. Although the CBG showed increased occupation by CORT during challenge, effects were not accompanied by a significant increase in the unbound T fraction. Thus, competitive hormone interactions on the CBG do not seem sufficient to explain changes in circulating T levels. To place our results within the context of past findings, we compared all socially monogamous birds tested to date for plasma levels of T during situational territorial intrusion experiments. We found that birds raising only one brood per season (e.g., the blue tit) consistently show no increase in plasma T but instead show elevations in circulating CORT. Thus, we suggest that single-broodedness plays an important role in determining patterns of hormone change and should be considered in future discussions of hormone-behavior interactions.


Assuntos
Agressão/fisiologia , Comportamento Animal/fisiologia , Passeriformes/metabolismo , Territorialidade , Testosterona/sangue , Animais , Proteínas de Transporte/sangue , Corticosterona/sangue , Masculino , Noruega , Passeriformes/sangue , Radioimunoensaio , Análise de Regressão , Reprodução/fisiologia , Especificidade da Espécie
19.
Proc Biol Sci ; 274(1606): 19-23, 2007 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-17015332

RESUMO

A cornerstone of ecological theory is the ecological niche. Yet little is known about how individuals come to adopt it: whether it is innate or learned. Here, we report a cross-fostering experiment in the wild where we transferred eggs of blue tits, Cyanistes caeruleus, to nests of great tits, Parus major, and vice versa, to quantify the consequences of being reared in a different social context, but in an environment otherwise natural to the birds. We show that early learning causes a shift in the feeding niche in the direction of the foster species and that this shift lasts for life (foraging conservatism). Both species changed their feeding niches, but the change was greater in the great tit with its less specialized feeding behaviour. The study shows that cultural transmission through early learning is fundamental to the realization of ecological niches, and suggests a mechanism to explain learned habitat preference and sympatric speciation in animals.


Assuntos
Comportamento Alimentar , Aprendizagem , Passeriformes/fisiologia , Comportamento Social , Animais , Ecossistema , Comportamento de Nidação , Especificidade da Espécie
20.
Proc Biol Sci ; 269(1499): 1449-55, 2002 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-12137574

RESUMO

Sexual-selection theories generally assume that mating preferences are heritable traits. However, there is substantial evidence that the rearing environment may be important for the development of mating preferences, indicating that they may be learnt, or modified by experience. The relative importance of such sexual imprinting across species remains largely unexplored. Here, we report results of a large-scale cross-fostering experiment in the wild in which nestling birds were raised by parents of a different species. We show that resulting sexual imprinting may have a negative effect on pairing success in one species (the great tit, Parus major), but not in two other species (the blue tit, P. caeruleus and the pied flycatcher, Ficedula hypoleuca). A remarkable variation thus seems to exist, even between species that are congeneric and have similar breeding ecologies. The cross-fostering resulted in heterospecific pairings between the two tit species (female blue tit breeding with male great tit), which has never, to our knowledge, been previously documented. However, the chicks fledging from these nests were all blue tit.


Assuntos
Fixação Psicológica Instintiva , Comportamento Sexual Animal , Aves Canoras/fisiologia , Animais , Meio Ambiente , Feminino , Masculino , Comportamento de Nidação , Reprodução , Especificidade da Espécie
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