Yuefeng Wu

A phylogeny of the Passerida (Aves: Passeriformes) based on mitochondrial 12S ribosomal RNA gene

BackgroundPasserida is the largest avian radiation within the order Passeriformes. Current understanding of the high-level relationships within Passerida is based on DNA–DNA hybridizations; however, the phylogenetic relationships within this assemblage have been the subject of many debates.MethodsWe analyzed the 12S ribosomal RNA gene from 49 species of Passerida, representing 14 currently recognized families, to outline the phylogenetic relationships within this group.ResultsOur results identified the monophyly of the three superfamilies in Passerida: Sylvioidea, Muscicapoidea and Passeroidea. However, current delimitation of some species is at variance with our phylogeny estimate. First, the Parus major, which had been placed as a distinct clade sister to Sylvioidea was identified as a member of the super family; second, the genus Regulus was united with the Sturnidae and nested in the Muscicapoidea clade instead of being a clade of Passerida.ConclusionOur results were consistent with Johansson’s study of the three superfamilies except for the allocation of two families, Paridae and Regulidae.

Comparison of adrenocortical responses to acute stress in lowland and highland Eurasian tree sparrows (Passer montanus): similar patterns during the breeding, but different during the prebasic molt

Previous studies indicate most free-living avian species in both extreme and temperate environments seasonally modulate the adrenocortical responses to acute stress, and those breeding in harsh environments always express reduced adrenocortical responses, which may allow them to obtain maximal reproductive success. However, recent investigations showing a human commensal species, house sparrows (Passer domesticus), expressed similar corticosterone (CORT) responses in both benign and harsh environments. In this study, focusing on another human commensal species, Eurasian tree sparrows (P. montanus), we examined the adrenocortical response to acute stress in lowland populations, among the early and late breeding, the prebasic molt, and the wintering stages, and compared them with previously published data from populations on the Tibetan Plateau. Our results show: (1) similar to highland Eurasian tree sparrows, lowland populations show no differences in baseline CORT levels among life history stages, and the stress-induced CORT (maximal CORT, total and corrected integrated CORT) levels are lower during the early breeding and the prebasic molt stages than those in the late breeding and the wintering stages; (2) highland Eurasian tree sparrows show stronger adrenocortical responses during the prebasic molt stage than lowland populations, whereas there are no differences between the early and the breeding stages (except for maximal CORT). Our results suggest that Eurasian tree sparrows from both harsh and benign environments have similar patterns of adrenocortical responses in the breeding stage, whereas they are different in the prebasic molt stage. In highland birds, the increased maximal CORT levels during the late breeding and the small increases in adrenocortical responses during the prebasic molt are interesting but remain unexplained.

Dynamic interactions between corticosterone, corticosteroid binding globulin and testosterone in response to capture stress in male breeding Eurasian tree sparrows

In birds, corticosterone (CORT), testosterone (T), and corticosteroid binding globulin (CBG) are involved in modulating the trade-off between reproduction and survival. In response to acute stress, increased total plasma CORT is a ubiquitous phenomenon while T levels can decrease, or remain unchanged. Since CORT and T bind competitively with CBG in birds, the underlying regulatory mechanisms and consequences of their dynamic interactions remain largely unknown. Here, we studied the dynamic changes of total CORT, T, and CBG, and estimated free and bound CORT and T in response to capture stress in male Eurasian tree sparrows (Passer montanus) across the nest building, egg-laying, and nestling stages. We predicted that free, bound and total hormone concentrations would increase for CORT and decrease for T in response to acute stress, and the relative magnitude of these changes would vary with life history stage. We found that baseline and stressed-induced CORT values did not vary across breeding sub-stages. However, total and bound CORT increased with stress while free remained unchanged. Baseline levels of total, free and bound T were highest during the nest building and it was the only stage in which all measures of T were affected by stress. Regardless of breeding stage or restraint stress, we did not detect a significant correlation between CORT and T. CBG was found to be mostly unoccupied by steroid hormones under stress and stress-free conditions and this likely provided an adequate buffer for changes in free levels of CORT and T during unpredictable environmental perturbations.

Changes in phytohaemagglutinin skin-swelling responses during the breeding season in a multi-brooded species, the Eurasian Tree Sparrow: do males with higher testosterone levels show stronger immune responses?

AbstractLife-history theory assumes that the fitness costs of immunity may have negative effects on reproductive success. Similarly, the immunocompetence handicap hypothesis is based on findings that testosterone (T) has immunosuppressive effects, although the basis of this hypothesis has recently been challenged. As much of the work examining the relationship between T levels and immune function has been carried out in captive-housed species, these results may not accurately reflect the situation of animals living in natural environments. To better understand the relationship between plasma T levels and immune function, studies focusing on free-living animals are needed. A previous study by our group determined the changes in both baseline and stress-induced T levels in free-living Eurasian Tree Sparrows (Passer montanus) across different annual cycle stages. In this study, we further report the phytohaemagglutinin skin-swelling (PHA) immune response in this multi-brooded species during different breeding sub-stages, and then determine the relationships between the PHA response and both baseline and stress-induced T levels. Our results show that the PHA response varied across the different sub-stages and differed significantly between the first and second brood stage. Furthermore, T levels in male Tree Sparrows are positively correlated with the PHA response during the breeding season, whereas this relationship is negative in females, suggesting that the biological function of T differs between the sexes. Therefore, our results suggest that free-living animals have evolved the ability to orchestrate trade-offs between reproduction and immune functions based on changes in physiology and the environment, which should provide further opportunities to study the flexibility and plasticity of physiological and ecological adaptations in natural environments.ZusammenfassungUnterschiedliche Immunantworten anhand Phytohaemagglutinin-Hautschwellung bei Feldsperlingen während der Brutzeit: Zeigen Männchen mit höheren Testosteronwerten stärkere Immunantworten? Die “Life-history”-Theorie besagt, dass die Kosten für Fitness des Immunsystems negative Auswirkungen auf den Reproduktionserfolg haben können. In gleicher Weise basiert die Immunkompetenz-Handicap-Hypothese darauf, dass Testosteron (T) immunsuppressive Effekte hat, wobei die Basis dieser Hypothese jüngst in Frage gestellt wurde. Da die meisten Arbeiten den Zusammenhang zwischen T-Levels und Immunfunktion an Arten in Gefangenschaft untersucht wurden, spiegeln die dort erzielten Ergebnisse nicht unbedingt die Situation wild lebender Tiere in ihren natürlichen Lebensräumen wider. Um den Zusammenhang zwischen T-Werten im Blutplasma und der Immunfunktion besser zu verstehen, sind Studien an frei lebenden Tieren notwendig. Eine frühere Studie unserer Arbeitsgruppe bestimmte die Veränderungen sowohl der Basis-Testosteronwerte als auch der stressinduzierten Werte bei freilebenden Feldsperlingen zwischen verschiedenen Phasen im Jahreszyklus. In der vorliegenden Studie dokumentieren wir die Immunantwort durch Phytohämagglutinin Hautschwellung (PHA) von Feldsperlingen während unterschiedlicher Brutstadien und bestimmten anschließend die Verhältnisse zwischen der PHA Immunantwort und den Basis- wie stressinduzierten T-Werte. Die Ergebnisse zeigen, dass die PHA Antwort zwischen verschiedenen Brutstadien variiert und sich signifikant zwischen der ersten und zweiten Brutphase unterscheidet. Darüber hinaus waren die T-Werte der Männchen positive korreliert mit der PHA Anwort während der Brutsaison, wohingegen das Verhältnis bei den Weibchen negativ ist. Das deutet auf eine unterschiedliche biologische Funktion von Testosteron für die Geschlechter hin. Daher weisen unsere Ergebnisse daraufhin, dass wildlebende Tiere die Fähigkeit entwickelt haben, den Konflikt zwischen Reproduktion und Immunfunktionen, basierend auf physiologischen und Umweltveränderungen, abzustimmen. Diese Ergebnisse sollten Anlass dazu geben, die Flexibilität und Plastizität physiologischer und ökologischer Anpassungen in natürlichen Lebensräumen weiter zu untersuchen.

Coping With Extreme: Highland Eurasian Tree Sparrows With Molt-Breeding Overlap Express Higher Levels of Corticoserone-Binding Globulin Than Lowland Sparrows

In birds, suppressed expression of stress-induced corticosterone (CORT) during pre-basic molt is generally thought to reflect a physiological trade-off in self-maintenance. And reduced CORT during breeding in extreme environments may maximize reproductive success and optimize their fitness. Highland Eurasian tree sparrows (Passer montanus) are known to express significantly higher stress-induced CORT levels during the pre-basic molt stage. Here, we show that these highland sparrows are characterized by a life history strategy of molt-breeding overlap, with higher corticosterone-binding globulin (CBG) levels favoring molt and breeding consistent with fitness optimization on the Tibetan Plateau. These unique behavioral and physiological strategies reflect natural selection under strong evolutionary pressures in extreme high-altitude environments.

Flying high: Limits to flight performance by sparrows on the Qinghai-Tibet Plateau.

ABSTRACT Limits to flight performance at high altitude potentially reflect variable constraints deriving from the simultaneous challenges of hypobaric, hypodense and cold air. Differences in flight-related morphology and maximum lifting capacity have been well characterized for different hummingbird species across elevational gradients, but relevant within-species variation has not yet been identified in any bird species. Here we evaluate load-lifting capacity for Eurasian tree sparrow (Passer montanus) populations at three different elevations in China, and correlate maximum lifted loads with relevant anatomical features including wing shape, wing size, and heart and lung masses. Sparrows were heavier and possessed more rounded and longer wings at higher elevations; relative heart and lung masses were also greater with altitude, although relative flight muscle mass remained constant. By contrast, maximum lifting capacity relative to body weight declined over the same elevational range, while the effective wing loading in flight (i.e. the ratio of body weight and maximum lifted weight to total wing area) remained constant, suggesting aerodynamic constraints on performance in parallel with enhanced heart and lung masses to offset hypoxic challenge. Mechanical limits to take-off performance may thus be exacerbated at higher elevations, which may in turn result in behavioral differences in escape responses among populations. Summary: Intraspecific differences in flight-related morphological and physiological variables over an ∼3000 m elevational range indicate aerodynamic constraints on flight performance in parallel with enhanced heart and lung masses to offset hypoxic challenge.

Variation in corticosterone response and corticosteroid binding‐globulin during different breeding sub‐stages in Eurasian tree sparrow (Passer montanus)

In free-living animals, it has been well demonstrated that the intensity of the adrenocortical response to acute restraint stress can vary with reproductive investment during breeding. The parental care hypothesis posits that the stress response is negatively correlated with parental investment in avian species. To further test this hypothesis, we examined changes in both free and total corticosterone (CORT) at baseline and stress-induced levels (maximal CORT) and corticosteroid-binding globulin (CBG) capacities, in both sexes of a multi-brooded Eurasian tree sparrows (Passer montanus), during the nest building, the early nestling, the later egg-laying, and the later nestling stages. Our results showed Eurasian tree sparrows did not exhibit any differences between sexes in CORT and CBG levels during the egg-laying or nestling stages. Both sexes had lowered CBG capacities and females exhibited lower maximal CORT during the early compared to later nestling stages. In addition, both sexes had lower maximal free CORT levels during the nest building stage than those of the early nestling stages, and males expressed higher total maximal CORT levels than females during nest building stage. The variation in CORT response and CBG levels during different breeding sub-stages in Eurasian tree sparrow may correlate with their energetic situations and parental investments. J. Exp. Zool. 325A:75-83, 2016.

Life-history dependent relationships between body condition and immunity, between immunity indices in male Eurasian tree sparrows.

In free-living animals, recent evidence indicates that innate, and acquired, immunity varies with annual variation in the demand for, and availability of, food resources. However, little is known about how animals adjust the relationships between immunity and body condition, and between innate and acquired immunity to optimize survival over winter and reproductive success during the breeding stage. Here, we measured indices of body condition (size-corrected mass [SCM], and hematocrit [Hct]), constitutive innate immunity (plasma total complement hemolysis activity [CH50]) and acquired immunity (plasma immunoglobulin A [IgA]), plus heterophil/lymphocyte (H/L) ratios, in male Eurasian tree sparrows (Passer montanus) during the wintering and the breeding stages. We found that birds during the wintering stage had higher IgA levels than those from the breeding stage. Two indices of body condition were both negatively correlated with plasma CH50 activities, and positively with IgA levels in wintering birds, but this was not the case in the breeding birds. However, there was no correlation between CH50 activities and IgA levels in both stages. These results suggest that the relationships between body condition and immunity can vary across life-history stage, and there are no correlations between innate and acquired immunity independent of life-history stage, in male Eurasian tree sparrows. Therefore, body condition indices predict immunological state, especially during the non-breeding stage, which can be useful indicators of individual immunocompetences for understanding the variations in innate and acquired immunity in free-living animals.

The role of climate factors in geographic variation in body mass and wing length in a passerine bird

BackgroundGeographic variation in body size is assumed to reflect adaptation to local environmental conditions. Although Bergmann’s rule is usually sufficient to explain such variation in homeotherms, some exceptions have been documented. The relationship between altitude, latitude and body size, has been well documented for some vertebrate taxa during the past decades. However, relatively little information is available on the effects of climate variables on body size in birds.MethodsWe collected the data of 267 adult Eurasian Tree Sparrow (Passer montanus) specimens sampled at 48 localities in China’s mainland, and further investigated the relationships between two response variables, body mass and wing length, as well as a suit of explanatory variables, i.e. altitude, latitude, mean annual temperature (MAT), annual precipitation (PRC), annual sunshine hours (SUN), average annual wind speed (WS), air pressure (AP) and relative humidity (RH).ResultsOur study showed that (1) although the sexes did not differ significantly in body mass, males had longer wings than females; (2) body mass and wing length were positively correlated with altitude but not with latitude; (3) body mass and wing length were negatively correlated with AP and RH, but not significantly correlated with WS. Body mass was positively correlated with SUN and inversely correlated with MAT. Wing length was not correlated with MAT in either sex, but was positively correlated with SUN and negatively correlated with PRC in male sparrows; (4) variation in body mass could be best explained by AP and SUN, whereas variation in wing length could be explained by RH and AP in both sexes. In addition, variation in male sparrows can be explained by SUN, WS and PRC but not in females.ConclusionsTwo different proxies of body size, body mass and wing length, correlated with same geographic factors and different climate factors. These differences may reflect selection for heat conservation in the case of body mass, and for efficient flight in the case of wing length.

Life-history dependent relationships between plasma alkaline phosphatase activity and body condition in male Eurasian Tree Sparrows

BackgroundIn temperate-breeding birds, individuals must adjust their physiological states from one life-history stage to another in response to changing conditions to maximize ecological fitness. Previous evidences have shown that body mass, size-corrected mass (SCM), and hematocrit (Hct) could be used as estimates of the energetic state of individuals to illustrate life-history trade-offs and individual quality in field physiology. Plasma alkaline phosphatase (ALP) plays critical roles in regulating the metabolism of energy but very limited information is known on its link with body mass or Hct.MethodsWe determined the changes of plasma ALP levels in both early breeding and wintering stages of male Eurasian Tree Sparrows (Passer montanus), and examined the relationships between ALP and body mass, SCM, and Hct of the birds.ResultsOur study showed that (1) in male Eurasian Tree Sparrows, body mass did not vary with life-history stage but plasma ALP activity significantly increased in the wintering stage compared to the breeding stage; (2) ALP activity was not correlated with individual body mass but was positively correlated with individual SCM and Hct. Such positive correlations, however, only occurred in the wintering but not in the breeding stages.ConclusionsOur results suggest that plasma ALP activities in free-living birds can be used as one of the indicators of body condition or nutritional status for analyzing individual variation in the wintering but not in the breeding stages. The life-history dependent relationships between plasma ALP activity and body condition may contribute to our better understanding of the trade-off between individual survival and reproduction in free-living animals.