Home About us Contact
|
Home About us Contact | ||
|
|
||
High Energetic Cost (high + energetic_cost)
Selected AbstractsKin structure and queen execution in the Argentine ant Linepithema humileJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2001M. Reuter Every spring, workers of the Argentine Ant Linepithema humile kill a large proportion of queens within their nests. Although this behaviour inflicts a high energetic cost on the colonies, its biological significance has remained elusive so far. An earlier study showed that the probability of a queen being executed is not related to her weight, fecundity, or age. Here we test the hypothesis that workers collectively eliminate queens to which they are less related, thereby increasing their inclusive fitness. We found no evidence for this hypothesis. Workers of a nest were on average not significantly less related to executed queens than to surviving ones. Moreover, a population genetic analysis revealed that workers were not genetically differentiated between nests. This means that workers of a given nest are equally related to any queen in the population and that there can be no increase in average worker,queen relatedness by selective elimination of queens. Finally, our genetic analyses also showed that, in contrast to workers, queens were significantly genetically differentiated between nests and that there was significant isolation by distance for queens. [source] Hatching fraction and timing of resting stage production in seasonal environments: effects of density dependence and uncertain season lengthJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2001M. Spencer Many organisms survive unfavourable seasons as resting stages, some of which hatch each favourable season. Hatching fraction and timing of resting stage production are important life history variables. We model life cycles of freshwater invertebrates in temporary pools, with various combinations of uncertain season length and density-dependent fecundity. In deterministic density-independent conditions, resting stage production begins suddenly. With uncertain season length and density independence, resting stage production begins earlier and gradually. A high energetic cost of resting stages favours later resting stage production and a lower hatching fraction. Deterministic environments with density dependence allow sets of coexisting strategies, dominated by pairs, each switching suddenly to resting stage production on a different date, usually earlier than without density dependence. Uncertain season length and density dependence allow a single evolutionarily stable strategy, around which we observe many mixed strategies with negatively associated yield (resting stages per initial active stage) and optimal hatching fraction. [source] Salt stress and resistance to hypoxic challenges in the common carp (Cyprinus carpio L.)JOURNAL OF FISH BIOLOGY, Issue 3 2000G. De Boeck Long term exposure to brackish water (171 mm NaCl) affected the capacity of common carp Cyprinus carpio to deal with hypoxic conditions and the critical oxygen concentrations for oxygen consumption increased. In addition, regulation of ammonia excretion was lost. The cytosolic phosphorylation potential (the index of the energy status of a cell in terms of potential transferable phosphate groups) in the lateral muscle on the other hand remained relatively unaffected, indicating that oxygen transport to the tissues was not severely compromised. It appears that exposure to brackish water reduces the capacity of common carp to cope with hypoxic conditions mainly because of the high energetic cost of hyperventilation under conditions where energy stores are depleted, and not because of any impeded oxygen transport mechanisms. [source] Fight or flight: antipredator strategies of baleen whalesMAMMAL REVIEW, Issue 1 2008JOHN K. B. FORD ABSTRACT 1The significance of killer whale Orcinus orca predation on baleen whales (Mysticeti) has been a topic of considerable discussion and debate in recent years. Discourse has been constrained by poor understanding of predator-prey dynamics, including the relative vulnerability of different mysticete species and age classes to killer whales and how these prey animals avoid predation. Here we provide an overview and analysis of predatory interactions between killer whales and mysticetes, with an emphasis on patterns of antipredator responses. 2Responses of baleen whales to predatory advances and attacks by killer whales appear to fall into two distinct categories, which we term the fight and flight strategies. The fight strategy consists of active physical defence, including self-defence by single individuals, defence of calves by their mothers and coordinated defence by groups of whales. It is documented for five mysticetes: southern right whale Eubalaena australis, North Atlantic right whale Eubalaena glacialis, bowhead whale Balaena mysticetus, humpback whale Megaptera novaeangliae and grey whale Eschrichtius robustus. The flight strategy consists of rapid (20,40 km/h) directional swimming away from killer whales and, if overtaken and attacked, individuals do little to defend themselves. This strategy is documented for six species in the genus Balaenoptera. 3Many aspects of the life history, behaviour and morphology of mysticetes are consistent with their antipredator strategy, and we propose that evolution of these traits has been shaped by selection for reduced predation. Fight species tend to have robust body shapes and are slow but relatively manoeuvrable swimmers. They often calve or migrate in coastal areas where proximity to shallow water provides refuge and an advantage in defence. Most fight species have either callosities (rough and hardened patches of skin) or encrustations of barnacles on their bodies, which may serve (either primarily or secondarily) as weapons or armour for defence. Flight species have streamlined body shapes for high-speed swimming and they can sustain speeds necessary to outrun pursuing killer whales (>15,20 km/h). These species tend to favour pelagic habitats and calving grounds where prolonged escape sprints from killer whales are possible. 4The rarity of observed successful attacks by killer whales on baleen whales, especially adults, may be an indication of the effectiveness of these antipredator strategies. Baleen whales likely offer low profitability to killer whales, relative to some other marine mammal prey. High-speed pursuit of flight species has a high energetic cost and a low probability of success while attacks on fight species can involve prolonged handling times and a risk of serious injury. [source] Maternal effort and joey growth in koalas (Phascolarctos cinereus)JOURNAL OF ZOOLOGY, Issue 4 2006J. R. Tobey Abstract The extent to which sex-biased maternal investment characterizes mammals is controversial, with less information available for evaluating patterns of maternal effort in marsupials than in placentals. Koalas Phascolarctos cinereus are size-dimorphic animals with a lengthy period of dependency and they reside in mating systems that might favour sex-biased maternal investment. We examined 18 years of data recorded from koalas living at the San Diego Zoo in order to examine how joey development and maternal condition might be connected. Koalas are pregnant for only 1 month, but joey emergence from the pouch does not occur until 32 weeks of age. Neither maternal condition nor age affected sex ratio at joey emergence, and both sexes had the same survivorship prospects. Koala dams transport and nurse joeys for close to 1 year, at which time the two sexes are size dimorphic. Given the poor-quality diet of koalas, combined with maternal transport of infants who are at least 25% of maternal mass, we suggest that infant rearing poses high energetic costs on koala females. We suggest that ecological and energetic constraints have moulded koala maternal strategies such that females maximize allocation of resources to offspring, regardless of sex, in order to increase prospects for joey survivorship. [source] Low birth weight of contemporary African Americans: An intergenerational effect of slavery?AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2009Grazyna Jasienska The average birth weight in the contemporary African-American population is about 250 g lower than the average birth weight of European Americans. Differences in genetic and socioeconomic factors present between these two groups can explain only part of birth weight variation. I propose a hypothesis that the low birth weight of contemporary African Americans not only results from the difference in present exposure to lifestyle factors known to affect fetal development but also from conditions experienced during the period of slavery. Slaves had poor nutritional status during all stages of life because of the inadequate dietary intake accompanied by high energetic costs of physical work and infectious diseases. The concept of "fetal programming" suggests that physiology and metabolism including growth and fat accumulation of the developing fetus, and, thus its birth weight, depend on intergenerational signal of environmental quality passed through generations of matrilinear ancestors. I suggest that several generations that have passed since the abolition of slavery in the United States (1865) has not been enough to obliterate the impact of slavery on the current biological and health condition of the African-American population. Am. J. Hum. Biol., 2009. © 2008 Wiley-Liss, Inc. [source] Insect wing shape evolution: independent effects of migratory and mate guarding flight on dragonfly wingsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009FRANK JOHANSSON Although, in some insect taxa, wing shape is remarkably invariant, the wings of Anisopteran dragonflies show considerable variation among genera. Because wing shape largely determines the high energetic costs of flight, it may be expected that interspecific differences are partly due to selection. In the present study, we examined the roles of long-distance migration and high-manoeuvrability mate guarding in shaping dragonfly wings, using a phylogeny-based comparative method, and geometric morphometrics to quantify wing shape. The results obtained show that migration affects the shape of both front and hind wings, and suggest that mate guarding behaviour may also have an effect, especially on the front wing. These effects on front wing shape are at least partly independent. Our findings are interesting when compared with the geographically widespread and ecologically diverse dipterans Acalyptratae (including the genus Drosophila). The wings in that group are similar in function and structure, but show strikingly low levels of interspecific variation. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 362,372. [source] | ||||||||||||||||||||||