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Subordinate Individuals (subordinate + individual)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Foraging Behaviour of Subordinate Great Tits (Parus major).

ETHOLOGY, Issue 10 2001
Can Morphology Reduce the Cost of Subordination?
This paper studies the magnitude of the behavioural shift, from forage standing to forage hanging, of subordinate great tits (Parus major) in two different social contexts: feeding solitarily vs. feeding with a dominant conspecific. The aim is to test the hypothesis that differences in morphological design provide subordinates with varying abilities to reduce the presumed costs of subordination. We find that different subordinate individuals change the foraging behaviour, occupying a different niche when an intra-specific competitor is present. Morphology linked to sexual dimorphism, specifically body mass, is the factor responsible for the different magnitudes of change. Lighter subordinates can remain longer than heavier ones at the feeding patch without interrupting their foraging. Thereby, the former reduce the costs of being subordinate more than the latter. Among subordinates, females are lighter than males; they also spend more time feeding in the presence of a dominant conspecific than males do. No differences are found between age categories. We find no relationship between tarsus length and individual ecological plasticity. Our results support the idea that the ecological plasticity due to morphological differences is a mechanism that allows subordinate individuals to overcome costs associated with subordination. [source]

Effects of elevated CO2 on the size structure in even-aged monospecific stands of Chenopodium album

GLOBAL CHANGE BIOLOGY, Issue 4 2003
HISAE NAGASHIMA
Abstract To investigate the effect of elevated CO2 on the size inequality and size structure, even-aged monospecific stands of an annual, Chenopodium album, were established at ambient and doubled CO2 with high and low nutrient availabilities in open top chambers. The growth of individual plants was monitored non-destructively every week until flowering. Elevated CO2 significantly enhanced plant growth at high nutrients, but did not at low nutrients. The size inequality expressed as the coefficient of variation tended to increase at elevated CO2. Size structure of the stands was analyzed by the cumulative frequency distribution of plant size. At early stages of plant growth, CO2 elevation benefited all individuals and shifted the whole size distribution of the stand to large size classes. At later stages, dominant individuals were still larger at elevated than at ambient CO2, but the difference in small subordinate individuals between two CO2 levels became smaller. Although these tendencies were found at both nutrient availabilities, difference in size distribution between CO2 levels was larger at high nutrients. The CO2 elevation did not significantly enhance the growth rate as a function of plant size except for the high nutrient stand at the earliest stage, indicating that the higher biomass at elevated CO2 at later stages in the high nutrient stand was caused by the larger size of individuals at the earliest stage. Thus the effect of elevated CO2 on stand structure and size inequality strongly depended on the growth stage and nutrient availabilities. [source]

Reproductive conflict delays the recovery of an endangered social species

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2009
Andrés López-Sepulcre
Summary 1Evolutionary theory predicts that individuals, in order to increase their relative fitness, can evolve behaviours that are detrimental for the group or population. This mismatch is particularly visible in social organisms. Despite its potential to affect the population dynamics of social animals, this principle has not yet been applied to real-life conservation. 2Social group structure has been argued to stabilize population dynamics due to the buffering effects of nonreproducing subordinates. However, competition for breeding positions in such species can also interfere with the reproduction of breeding pairs. 3Seychelles magpie robins, Copsychus sechellarum, live in social groups where subordinate individuals do not breed. Analysis of long-term individual-based data and short-term behavioural observations show that subordinates increase the territorial takeover frequency of established breeders. Such takeovers delay offspring production and decrease territory productivity. 4Individual-based simulations of the Seychelles magpie robin population parameterized with the long-term data show that this process has significantly postponed the recovery of the species from the Critically Endangered status. 5Social conflict thus can extend the period of high extinction risk, which we show to have population consequences that should be taken into account in management programmes. This is the first quantitative assessment of the effects of social conflict on conservation. [source]