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Most models of habitat selection assume that individual animals choose and either reuse or abandon sites based on a constant
reassessment of site quality. When survival is a function of the presence of conspecifics, however, the benefits of returning
to traditional sites may override resource assessment. Many animals form roosting aggregations at what appear to be traditional
sites. At our study site in Nicaragua, the harvestman Prionostemma sp. forms diurnal roosting aggregations on a small subset of the available spiny palm trees. With respect to physical characteristics
and microclimate, the spiny palms used by the harvestmen resembled a random sample of those available, yet the same subset
of trees was used in two different years (2001, 2003). This suggests that the location of aggregation sites is traditional,
not a product of habitat limitation. Individual harvestmen were not faithful to particular roost sites, however, which raises
the question of how the tradition could be maintained over time. In this paper, we present evidence, derived from a series
of small-scale field experiments, that the harvestmen mark roosting sites chemically and enter marked sites preferentially
when searching for places to roost. We also show that the harvestmen are sensitive to changes in site quality (the presence
of spines) but will continue to use degraded traditional sites when no intact spiny palms are nearby. This system provides
an example of how animal traditions could be maintained over multiple generations without learning. Site-labeling can be viewed
as an external form of social memory. 相似文献
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When endoparasitoid wasps oviposit into hosts which have already been parasitized (= superparasitism), this results in potentially
lethal interlarval competition. For solitary species, the decision to lay additional eggs should therefore be based on the
probability of superparasite survival in any superparasitized host. In this study, in vitro contests staged between three larval instars of Venturia canescens Grav. (Hymenoptera: Ichneumonidae) reveal that the age difference between competitors affects the outcome of interlarval
competition. Three parameters were used to assess parasitoid performance: the number of fights initiated, the number of bites
inflicted, and the duration of each bite. When fighting takes place between two first instars, then both competitors were
found to be evenly matched. However, at greater age differences, first-instar competitors appeared to win more fights than
their larger second instar rivals. The advantage shown by younger competitors is most pronounced in contests staged between
first and third instar larvae. These findings are consistent with the increasingly high levels of conspecific superparasitism
shown by V. canescens in the first 5 days after initial host attack, suggesting that this parasitoid can deploy her use of deliberate superparasitism
in an adaptive way.
Received: 13 December 1995/Accepted after revision: 5 March 1996 相似文献
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Alex?C.?C.?WilsonEmail author Richard?K.?Grosberg 《Behavioral ecology and sociobiology》2004,57(1):40-49
Like many modular organisms, genetically distinct colonies of the hydrozoan Hydractinia symbiolongicarpus naturally fuse to produce chimeras. One of the principal cooperative benefits of fusion arises from the increased size of the resulting chimeric individual, which may enhance survivorship. However, fusion also promotes conflict through competition between cell lineages for representation in reproductive tissues. Previous studies on H. symbiologicarpus show that, consistent with kin selection theory, a highly polymorphic self/non-self recognition system limits fusion to close kin. However, these recognition systems are intrinsically subject to error. Conspecific acceptance threshold theory predicts that as the costs and benefits of making recognition errors change, or the frequencies of encounters between acceptable and unacceptable kin vary, the recognition system should respond. Specifically, as the benefits of acceptance decline or the frequency of encounters with unacceptable individuals increases, the acceptance threshold should become more restrictive. We tested this hypothesis by monitoring changes in the expression of fusion/rejection behaviors of H. symbiolongicarpus during colony establishment, a period of high mortality when the size-dependent benefits of fusion may be changing most rapidly, and the frequency of encounters with close kin declines. Across seven full-sib families, fusion frequencies between pairs of sibling colonies declined from 73% for 3-day-old colonies to 58% by day 12. This decline is consistent with optimal acceptance threshold theory. However, the period of maximum decline also corresponds to an interval during which the recognition effector mechanism becomes fully functional, suggesting that the shift to a more restrictive conspecific acceptance threshold may reflect an intrinsic constraint on recognition system maturation.Communicated by T. Czeschlik 相似文献
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