Intrinsic factors drive spatial genetic variation in a highly vagile species,the wedge‐tailed eagle Aquila audax,in Tasmania

Knowledge of dispersal in a species, both its quantity and the factors influencing it, are crucial for our understanding of ecology and evolution, and for species conservation. Here we quantified and formally assessed the potential contribution of extrinsic factors on individual dispersal in the threatened Tasmanian population of wedge‐tailed eagle Aquila audax. As successful breeding by these individuals appears strongly related to habitat, we tested the effect of landscape around sampling sites on genetic diversity and spatial genetic variation, as these are influenced by patterns of dispersal. Similarly, we also tested whether habitat intervening sampling sites could explain spatial genetic variation. Twenty microsatellites were scored, but only a small proportion of spatial genetic variation (4.6%) could be explained by extrinsic factors, namely habitat suitability and elevation between sites. However, significant clinal genetic variation was evident across Tasmania, which we explain by intrinsic factors, likely high natal philopatry and occasional long‐distance dispersal. This study demonstrates that spatial genetic variation can be detected in highly vagile species at spatial scales that are small relative to putative dispersal ability, although here there was no substantial relationship with landscape factors tested.     

Intrinsic differences in dispersal between populations of gastropods separated by a few metres: Evidence from reciprocal experimental transplantation

Differences between populations in dispersive behaviour can strongly influence population and community structure and have important implications for evolution. Differences in dispersal can be caused by intrinsic differences among populations or by different extrinsic cues. In a semi exposed shore in Co. Wicklow, Ireland, intertidal gastropods, Littorina littorea moved long distances in areas with low natural population density compared to areas with high natural density but were not influenced by density per se. A reciprocal experimental transplantation distinguished between intrinsic and extrinsic factors as causes of differences in dispersive behaviour. Snails from the area of high density were transplanted to the area of low density and vice versa. Comparisons were also carried out with controls (disturbed and undisturbed individuals) in each area. Dispersal of transplanted snails was compared with that of snails translocated within each area. Mean distances displaced and percentage dispersal were monitored after two days period. To test temporal generality the experiment was done twice. The two experiments yielded different outcomes. The majority of evidence supported the intrinsic model: transplanted snails dispersed differently from controls in their new area and similarly to controls in their area of origin. However, in one of the experiments there was some evidence suggesting influence of extrinsic factors or an interaction between extrinsic and intrinsic factors. Further research is required to identify whether the observed intrinsic differences are genetic or due to internal conditions that have been modified by the animal's present and/or past environment. This study reinforces the value of repeated experimental transplantation to characterize factors causing differences in behaviour.     

Simple shifts in redox/thiol balance that perturb blood coagulation.

The biological chemistry that underlies and regulates the blood coagulation cascade is not fully understood. To begin to understand this, we performed clotting assays under various redox conditions. By varying the amount of oxidant and/or antioxidant in these assays, we observed that both the intrinsic/tenase complex and the extrinsic pathways were susceptible to shifts in the thiol/redox balance. We established a dichotomy where blood clotting via the intrinsic pathway was sensitive to oxidation whereas the tissue factor or extrinsic pathway was more sensitive to reduction. These differential inhibitory effects present a conceptual mechanism for selective modulation of the activities of clotting factors specific for the respective pathways. These data also suggest that blood clotting may be influenced by unidentified redox or thiol equilibria.     

Relative contributions of offspring quality and environmental quality to adult field performance

Determinants of adult performance, such as growth and survival, are influenced by extrinsic, environmental and intrinsic, phenotypic factors. The relative importance of extrinsic and intrinsic factors, while ecologically relevant, is rarely estimated simultaneously. We estimate the relative contributions of offspring size (intrinsic) and various environmental factors (extrinsic) on adult performance in the marine colonial bryozoan Watersipora subtorquata. We used a variance partitioning approach for both new and previously published data, enabling us to examine the performance of over 1000 individuals in the field. We found offspring size to explain relatively little variation in adult performance. Of the environmental factors taken to account, temporal variation and an environmental gradient had the strongest influences.     

Variation of plasma protein parameters in four free-ranging reindeer herds and in captive reindeer under defined feeding conditions

Plasma total protein (TP), albumin (ALB) and globulin (GLOB) concentrations and albumin/globulin ratio (A/G) were analysed from blood samples collected from free-ranging reindeer (Rangifer tarandus tarandus) herds at varying times of year. The same parameters were followed in nine captive reindeer with varying protein and energy intake. Variation in the blood constituents of free-ranging reindeer was analysed in relation to different extrinsic and intrinsic factors and compared to findings from captive animals, allowing the analysis of effects of protein and energy intake. There was large overall variation in TP, ALB, GLOB and A/G ratio in the free-ranging animals, ranging between 36-110 g/L, 18-59 g/L, 17-59 g/L and 0.5-2.1. The variation between months and years was significant for all variables except the A/G ratio, where no year effect was noted. Increase in live body mass was associated with a small significant increase and pregnancy with a small significant decrease in all dependent variables, except for the A/G ratio. Age did not have a significant effect on any of the blood constituents when body mass was included in the same model. In captive animals, feeding lichens with low protein content was related to a significant decline in TP, ALB and GLOB, but not in the A/G ratio, whereas feeding commercial ration increased plasma TP, ALB and GLOB significantly. Extrinsic factors such as season and year explained majority of variation in the blood constituents of free-ranging reindeer, whereas body mass, pregnancy and age had only a minor influence. It is concluded that plasma TP and ALB, and to a lesser extent GLOB and A/G ratio may serve as nutritional biomarkers of reindeer.     

Old pythons stay fit; effects of haematozoan infections on life history traits of a large tropical predator

We document the impact of blood parasite infections caused by Hepatozoon sp. on water python (Liasis fuscus) life history traits such as growth rates, condition, reproductive output and survival. Individual snakes maintained similar among-year parasite loads. Hepatozoon infections affected python growth rate, i.e. snakes suffering from high infection levels exhibited significantly slower growth compared to individuals with low parasite loads. Our results suggest that the parasites also affected the pythons nutritional status (condition), as snakes with low condition scores suffered from higher parasite infection levels than snakes with high scores. Furthermore, our data suggest that parasitaemia may affect female reproductive output, as reproductive female pythons harboured lower parasite loads compared to non-reproductive adult females. High levels of parasite infections also affected juvenile python survival, as recaptured snakes harboured significantly lower parasite loads compared to non-recaptured yearling pythons. In our study area, water python have very few natural predators and, hence, experience low mortality rates and commonly reach an age of >15 years. In contrast to results obtained in other studies, parasite loads in larger/older pythons were lower compared to younger snakes, suggesting that only snakes harbouring lower levels of parasitaemia were able to survive to old age. We suggest that a possible cause for the opposing results regarding parasite prevalence and host age may be due to different levels of extrinsic mortality rates and longevity. Long-lived organisms, such as water pythons, may invest relatively more into crucial self-maintenance functions such as parasite defence, compared to short-lived organisms.     

温度对三种满江红光合及固氮活性的影响

本文报道满江红(Azolla imbricata)、卡洲满江红(A. caroliniana)和蕨状满江红(A. filiculoides)的光合与固氮(乙炔还原)活性对温度的反应差异。根区培养液温度在7—40℃范围内满江红与卡洲满江红的光合活性在30℃达到峰值,高于或低于30℃均急剧下降。而蕨状满江红在7—25℃的根区温度范围内光合活性差异不大,高于25℃则下降(图2)。0℃24小时或40℃2小时暗预处理对三种满江红光合活性与乙炔还原活性表现出不同影响(图3,4)。本文报道的方法可用于满江红生理生态参量的比较研究。     

Temporal and spatial complexity of maternal thermoregulation in tropical pythons

Parental care is a widespread adaptation that evolved independently in a broad range of taxa. Although the dynamics by which two parents meet the developmental needs of offspring are well studied in birds, we lack understanding about the temporal and spatial complexity of parental care in taxa exhibiting female-only care, the predominant mode of parental care. Thus, we examined the behavioral and physiological mechanisms by which female water pythons Liasis fuscus meet a widespread developmental need (thermoregulation) in a natural setting. Although female L. fuscus were not facultatively thermogenic, they did use behaviors on multiple spatial scales (e.g., shifts in egg-brooding postures and surface activity patterns) to balance the thermal needs of their offspring throughout reproduction (gravidity and egg brooding). Maternal behaviors in L. fuscus varied by stage within reproduction and were mediated by interindividual variation in body size and fecundity. Female pythons with relatively larger clutch sizes were cooler during egg brooding, suggesting a trade-off between reproductive quantity (size of clutch) and quality (developmental temperature). In nature, caregiving parents of all taxa must navigate both extrinsic factors (temporal and spatial complexity) and intrinsic factors (body size and fecundity) to meet the needs of their offspring. Our study used a comprehensive approach that can be used as a general template for future research examining the dynamics by which parents meet other developmental needs (e.g., predation risk or energy balance).     

Extrinsic and intrinsic influences on tree growth — anatomical analysis of spruce branches

Summary In order to differentiate between environmental (extrinsic) influences affecting tree growth, and those causing (intrinsic) temporary irregularities in a single tree, we investigated the anatomy of three branches of comparable size and age, taken from two 60-year-old European spruces [Picea abies (L.) Karst]. Wood depositions in five consecutive internodes (4–8) along the branches were analysed. Internodal cross-sections were evaluated to discover whether extrinsic factors may have influenced the structure of the cambial xylogenic derivatives, or whether structural variations were caused by intrinsic events. Features occurring in all three branches were evaluated as extrinsically influenced. Observations like earlywood disturbances, distribution of resin ducts, duplication of radial files, and increments with narrow or broad latewood bands were considered. The ratio of radial cell number to ring width was used to define the vigour of cambial growth during the years covered. Meteorological data of the growing periods (May–September 1981–1988) representing mean values of temperature, cloudiness, sunshine and precipitation were used to characterize weather conditions. They were considered as extrinsic influences, possibly affecting anatomical structures.     

Hematologic responses in captive white-winged doves (Zenaida asiatica), induced by various radiotransmitter attachments

White blood cell counts, heterophil-lymphocyte ratios, and leukocyte differentials of captive white-winged doves (Zenaida asiatica) from Texas equipped with different radiotransmitter attachment packages were monitored. Doves were segregated by gender and age by males, females, and hatching year; individuals housed in 30 large outdoor pens in groups of seven. Treatments consisted of controls, glue-on transmitters, body loop harnesses, surgically implanted intracoelomic transmitters, surgically implanted subcutaneous transmitters, intracoelomic surgery without implants, and subcutaneous surgery without implants. We used multivariate analysis of variance with pen as a blocking variable and gender nested and repeated measures analysis of variance to identify differences among any of the transmitter attachment techniques and the control for dependent variables. We found no difference in blood parameters between transmitter attachment technique versus a control.     

Evaluating the role of body size and habitat type in movement behavior in human‐dominated systems: A frog's eye view

1. Animal movement is a key process that connects and maintains populations on the landscape, yet for most species, we do not understand how intrinsic and extrinsic factors interact to influence individual movement behavior.
2. Land‐use/land‐cover changes highlight that connectivity among populations will depend upon an individual''s ability to traverse habitats, which may vary as a result of habitat permeability, individual condition, or a combination of these factors.
3. We examined the effects of intrinsic (body size) and extrinsic (habitat type) factors on desiccation tolerance, movement, and orientation in three anuran species (American toads, Anaxyrus americanus; northern leopard frogs, Lithobates pipiens; and Blanchard''s cricket frogs, Acris blanchardi) using laboratory and field studies to connect the effects of susceptibility to desiccation, size, and movement behavior in single‐habitat types and at habitat edges.
4. Smaller anurans were more vulnerable to desiccation, particularly for species that metamorphose at relatively small sizes. Habitat type had the strongest effect on movement, while body size had more situational and species‐specific effects on movement. We found that individuals moved the farthest in habitat types that, when given the choice, they oriented away from, suggesting that these habitats are less favorable and could represent barriers to movement.
5. Overall, our work demonstrated that differences in habitat type had strong impacts on individual movement behavior and influenced choices at habitat edges. By integrating intrinsic and extrinsic factors into our study, we provided evidence that population connectivity may be influenced not only by the habitat matrix but also by the condition of the individuals leaving the habitat patch.

     

Intrinsic and Extrinsic Factors Influence Expression of Defensive Behavior in Plains Hog‐Nosed Snakes (Heterodon nasicus)

Animals failing to deter predation are eaten. Among the many deterrents to predation, antipredator behaviors are perhaps the most variable, ranging from active (fight or flight) to passive (immobility). We assessed variation in the expression of a passive defensive behavior, death‐feigning, in Plains Hog‐nosed Snakes (Heterodon nasicus) and predicted that intrinsic and extrinsic factors would influence the duration of this behavior and the latency to its onset. We simulated predatory attacks on 27 snakes encountered in the field, and analyzed the behavioral responses of snakes as a function of differences among individuals (sex and size) and environmental factors (temperature and microhabitat). Larger snakes death‐feigned for longer durations than smaller ones; this relationship was stronger for female snakes than for males. Death feints were initiated sooner when snakes were encountered at higher temperatures. Extrinsic factors had a greater influence on latency to death‐feigning behavior, whereas intrinsic factors more strongly influenced its duration. Because our results involved wild snakes, they provide an improved, highly relevant understanding of individual and environmental factors that regulate the expression of immobile defensive behavior. Furthermore, additional hypotheses can now be proposed that address the evolution of defensive behaviors that leave animals prone to attack.     

Functional difference between intrinsic and extrinsic coagulation pathways. Kinetics of factor X activation on human monocytes and alveolar macrophages

Activation of coagulation factor X via the intrinsic pathway requires the assembly of factors IXa and VIII on lipid membranes. It is known that the platelet expresses membrane sites for assembly of factors IXa/VIII and promotes efficient factor X activation. We now show that human blood monocytes, but not lymphocytes or polymorphonuclear leukocytes, also express appropriate sites for factors IXa/VIII assembly. The maximal rate of factor X activation by factors IXa (0.75 nM) and VIII (1 unit/ml) assembled on monocytes is similar to the maximal rate on platelets. This rate, adjusted per micromole of lipid phosphorus, is 1636 +/- 358 nM factor Xa/min on monocyte, and 1569 +/- 54 nM factor Xa/min on platelets. At physiologic concentrations of factors X and VIII, the activation rate increases with factor IXa concentration asymptotically approaching a maximum. Half-maximal rate is achieved with 1.0 +/- 0.16 nM factor IXa. Monocytes and macrophages, but not platelets, can express membrane tissue factor and thus promote simultaneous assembly of two distinct factor X-activating protease complexes. In these studies, blood monocytes and alveolar macrophages are used as membrane sources in kinetic experiments comparing factor X activation by intrinsic (factor IXa/VIII) versus extrinsic (factor VII/tissue factor) protease complexes. At plasma concentration of factors VIII and VII, apparent Km on the monocyte is 14.6 +/- 1.4 nM for intrinsic and 117.0 +/- 10.1 nM for extrinsic activation. The apparent Km on alveolar macrophages is 12.1 +/- 1.9 and 90.6 +/- 10.2 nM for intrinsic and extrinsic activation, respectively. Maximal rates on monocytes at saturating concentration of factors IXa, VIII, and VII are 48.0 +/- 11.2 nM factor Xa/min, for intrinsic activation, and 16.5 +/- 5.5 nM factor Xa/min, for extrinsic activation. These data show that the monocyte/macrophage is the only blood-derived cell type with membrane sites for both intrinsic and extrinsic pathway assembly. We have exploited this characteristic of the monocyte/macrophage membrane to demonstrate that factor X activation by the intrinsic pathway protease is more efficient than activation via the extrinsic pathway protease complex.     

Reproductive plasticity, ovarian dynamics and maternal effects in response to temperature and flight in Pararge aegeria

In nature, ovipositing females may be subjected to multiple extrinsic and intrinsic environmental factors simultaneously. To adequately assess a species response to environmental conditions during oviposition it may therefore be necessary to consider the interaction between multiple intrinsic and extrinsic factors simultaneously. Using the butterfly, Pararge aegeria, this study examined the combined effects of extrinsic (temperature and flight) and intrinsic (body mass and age) factors on ovarian dynamics, egg provisioning and reproductive output, and explored how these effects subsequently influenced offspring fitness when egg-stage development occurred in a low humidity environment. Both temperature- and flight-mediated plasticity in female reproductive output was observed, and there were strong temperature by flight interaction effects for the traits oocyte size and egg mass. As females aged, mean daily fecundity differed across temperature treatments, but not across flight treatments. Overall, temperature had more pronounced effects on ovarian dynamics than flight. Flight mainly influenced egg mass via changes in relative water content. A mismatch between the physiological response of females to high temperature and the requirements of their offspring had a negative impact on offspring fitness via effects on egg hatching success.     

Plant species,mycorrhiza, and aphid age influence the performance and behaviour of a generalist

1. Life‐history traits of herbivores are shaped by the combination of various extrinsic and intrinsic variables. However, studies investigating the impact of both variables on insect behavioural phenotypes are rare, and research including the modulation of host plant quality by arbuscular mycorrhiza (AM) (extrinsic variable) and the herbivore developmental stage (intrinsic variable) on aphid behaviour is lacking. 2. To study the influences of extrinsic and intrinsic variables on aphid performance and behaviour, individuals of the generalist aphid pest Myzus persicae (Sulzer) were reared on Plantago lanceolata and Poa annua plants that were either non‐mycorrhized (NM) or mycorrhized (AM). Aphid performance was monitored over 2 weeks. Behavioural traits of nymphs were recorded twice during development after removing individuals from their feeding sites and placing them in an unknown environment (‘open field’), causing disturbance. Plant quality was determined by measuring the water content and leaf mass per area (LMA). 3. Differences in body mass of nymphs at day 6 dependent on plant species and treatment were compensated by the individuals within 4 days. Behavioural traits, considered as activity and exploration, were affected by the interaction between extrinsic and intrinsic variables (activity and exploration) and changed over ontogeny (activity). Independent of AM, a lower water content and LMA were recorded in P. annua leaves. 4. Overall, this study demonstrates that extrinsic and intrinsic variables need to be considered in combination and behavioural traits should be studied repeatedly during insect ontogeny to understand the complexity of microbe‐modulated plant–herbivore interactions.     

Intrinsic and extrinsic contributions to the passive moment at the metacarpophalangeal joint

The purpose of this investigation was to determine whether the passive range of motion at the finger joints is restricted more by intrinsic tissues (cross a single joint) or by extrinsic tissues (cross multiple joints). The passive moment at the metacarpophalangeal (MP) joint of the index finger was modeled as the sum of intrinsic and extrinsic components. The intrinsic component was modeled only as a function of MP joint angle. The extrinsic component was modeled as a function of MP joint angle and wrist angle. With the wrist fixed in seven different positions the passive moment at the MP joint of eight subjects was recorded as the finger was rotated through its range at a constant rate. The moment-angle data were fit by the model and the extrinsic and intrinsic components were calculated for a range of MP joint angles and wrist positions. With the MP joint near its extension limit, the median percent extrinsic contribution was 94% with the wrist extended 60° and 14% with the wrist flexed 60°. These percentages were 40 and 88%, respectively, with the MP joint near its flexion limit. Our findings indicate that at most wrist angles the extrinsic tissues offer greater restraint at the limits of MP joint extension and flexion than the intrinsic tissues. The intrinsic tissues predominate when the wrist is flexed or extended enough to slacken the extrinsic tissues. Additional characteristics of intrinsic and extrinsic tissues can be deduced by examining the parameter values calculated by the model.     

International variability of ages at menarche and menopause: patterns and main determinants.

The purpose of this study was to review published studies on the variability of age at menarche and age at menopause throughout the world, and to identify the main causes for age variation in the timing of these events. We first present a summary table including mean (or median) values of the age at menarche in 67 countries, and of the age at menopause in 26 countries. General linear models showed that mean age at menarche was strongly linked to the mean female life expectancy, suggesting that one or several variables responsible for inequalities in longevity similarly influenced the onset of menarche. A closer examination of the data revealed that among several variables reflecting living conditions, the factors best explaining the variation in age at menarche were adult illiteracy rate and vegetable calorie consumption. Because adult illiteracy rate has some correlation with the age at which children are involved in physical activities that can be detrimental in terms of energy expenditure, our results suggest that age at menarche reflects more a trend in energy balance than merely nutritional status. In addition, we found the main determinant of age at menopause to be the mean fertility. This study thus suggests that, on a large scale, age at menarche is mainly determined by extrinsic factors such as living conditions, while age at menopause seems to be mainly influenced by intrinsic factors such as the reproductive history of individuals. Finally, these findings suggest that human patterns cannot be addressed solely by traditional, small-scale investigations on single populations. Rather, complementary research on a larger scale, such as this study, may be more appropriate in defining some interesting applications to the practical problems of human ecology.     

Environmental heterogeneity and neighbourhood interference modulate the individual response of Juniperus thurifera tree-ring growth to climate

Individual variation of tree-ring growth response to climate and heterogeneity of the local environment are usually neglected in dendrochronological research. Even if there is evidence showing that individual responsiveness to climate may depend on intrinsic traits such as tree age, size or sex, its modulation by the local heterogeneity of extrinsic factors has been less studied. Using an extensive, strictly regular sampling scheme across a 3300 ha woodland, we assessed the individual variation of tree-ring growth responses to climate in 100 Juniperus thurifera L. trees. The climatic response was evaluated by bootstrapped correlations of both population- and individual-based tree-ring chronologies with monthly records of precipitation, cloudiness, minimum and maximum temperatures. We studied also the influence of extrinsic abiotic (elevation, slope, heat load, tree location) and biotic (competition from neighbouring trees) factors on the individual growth variation and its climatic response. At a population level, growth was controlled by February–March precipitation, April minimum temperature, and June water stress. A significant proportion of individuals did not respond to those variables, but were sensitive to others not relevant at the population level. Inter-annual growth variation was strongly modulated by competition, whereas trees under lower competition levels, in eastern and warmer areas, were the most responsive to climate. The individual climatic response was, at least partially, modulated by the local heterogeneity of extrinsic factors. By considering environmental heterogeneity and neighbourhood interference we can identify the spectrum of site-dependent climatic responses in a population, which in turn will enable more realistic predictions of tree responses to ongoing climate change.     

Does body size influence thermal biology and diet of a python (Morelia spilota imbricata)?

Current theory predicts that larger‐bodied snakes not only consume larger prey (compared with smaller individuals), but may also have a different range of prey available to them due to their thermal biology. It has been argued that smaller individuals, with lower thermal inertia (i.e. faster cooling rates at nightfall when air temperature falls and basking opportunities are limited), may be thermally restricted to foraging and hunting during the day on diurnally active prey, and have reduced capacity to hunt crepuscular and nocturnal prey species. This predictive theory was investigated by way of dietary analysis, assessment of thermal biology and thermoregulation behaviour in an ambush forager, the south‐west carpet python (Morelia spilota imbricata, Pythonidae). Eighty‐seven scats were collected from 34 individual pythons over a 3‐year radiotelemetry monitoring study. As predicted by gape size limitation, larger pythons took larger prey; however, 65% of prey items of small pythons were represented by nocturnally active, small mammals, a larger proportion than present in larger snakes. Several measures of thermal biology (absolute body temperature, thermal differential of body temperature to air temperature, maximum hourly heating and cooling rates) were not strongly affected by python body mass. Additionally, body temperature was only influenced by the behavioural choice of microhabitat selection and was not affected by python body size or position, suggesting that these behavioural choices do not allow smaller pythons to vastly increase their temporal foraging window. By coupling dietary analysis, measures of body temperature and behavioural observations of free‐ranging animals, we conclude that, contrary to theoretical predictions, a small body size does not thermally restrict the temporal window for ambush foraging in M. s. imbricata. An ontogenetic or size‐determined switch from ambush feeding to actively foraging on slower prey would account for the differences in prey taken by these animals. The concept of altered foraging behaviour warrants further investigation in this species.