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11.
Lars?B.?PetterssonEmail author Indar?W.?Ramnarine S.?Anette?Becher Rajindra?Mahabir Anne?E.?Magurran 《Behavioral ecology and sociobiology》2004,55(5):461-468
In many species, population sex ratios have far-reaching consequences for a wide variety of population-level and behavioural processes and can directly influence sexual selection through differential effects on male and female mating behaviour. Although sex ratios are often treated as more or less stable population characteristics, recent theoretical evidence suggests that sex ratios fluctuate under many conditions, and that the amplitude of these fluctuations can be considerable. Few studies have attempted to quantify this variation in systems with prominent, sex ratio-dependent sexual conflict. One of the species with the greatest potential to integrate these factors in the wild is the Trinidadian guppy, Poecilia reticulata. In this study, we quantified natural sex ratio variation both as detailed longitudinal studies of focal guppy populations and as snapshot estimates across a range of freshwater habitats. In line with theoretical predictions, we expected to detect significant sex ratio variation over time. We also investigated the association between juvenile and adult sex ratios to quantify a possible compensatory feedback implied in standard models of sex ratio evolution. Our results confirm that population-level sex ratios in wild guppy populations have a range of dynamic features, with all four focal populations showing significant variation in sex ratio over time. The survey showed that juveniles were generally close to equal (50:50) sex ratios whereas 7 out of 11 adult sex ratios differed significantly from equality. We found no evidence that a surplus of juveniles of the locally rarer sex had been produced. The results indicate that sex ratios and hence the balance between sexual selection and sexual coercion is normally fluctuating in nature, despite juvenile ratios being close to equality.Communicated by J. Krause 相似文献
12.
Survival of Euchaeta japonica
Marukawa prefeeding stages in natural seawater is increased by the addition of a synthetic chelating agent. This increase occurs periodically in inshore waters and more frequently in near-oceanic water. The periodicity is associated with changes in chelator-like characteristics of the seawater. Changes in these characteristics are associated with changes in biological activity in the water. 相似文献
13.
Grant E. Brown Camille J. Macnaughton Chris K. Elvidge Indar Ramnarine Jean-Guy J. Godin 《Behavioral ecology and sociobiology》2009,63(5):699-706
The antipredator behaviour of prey organisms is shaped by a series of threat-sensitive trade-offs between the benefits associated
with successful predator avoidance and a suite of other fitness-related behaviours such as foraging, mating and territorial
defence. Recent research has shown that the overall intensity of antipredator response and the pattern of threat-sensitive
trade-offs are influenced by current conditions, including variability in predation risk over a period of days to weeks. In
this study, we tested the hypothesis that long-term predation pressure will likewise have shaped the nature of the threat-sensitive
antipredator behaviour of wild-caught Trinidadian guppies (Poecilia reticulata). Female guppies were collected from two populations that have evolved under high- and low-predation pressure, respectively,
in the Aripo River, Northern Mountain Range, Trinidad. Under laboratory conditions, we exposed shoals of three guppies to
varying concentrations of conspecific damage-released chemical alarm cues. Lower Aripo (high-predation) guppies exhibited
the strongest antipredator response when exposed to the highest alarm cue concentration and a graded decline in response intensity
with decreasing concentrations of alarm cue. Upper Aripo (low-predation) guppies, however, exhibited a nongraded (hypersensitive)
response pattern. Our results suggest that long-term predation pressure shapes not only the overall intensity of antipredator
responses of Trinidadian guppies but also their threat-sensitive behavioural response patterns. 相似文献