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31.
Aim Because of the obligatory relationship between endoparasitoids and their hosts, we presume that hosts exert strong selection pressure on parasitoids. One prediction is a positive relationship between host diversity and parasitoid richness. This relationship could be the product of resource availability which could lead to more opportunities for speciation, or could represent shared responses to the environment by both groups. Location Argentina and Paraguay. Methods We sampled a 1800‐km transect to test for a correlation between the richness of leaf‐cutting ant hosts and their phorid parasitoids. Regression models were used to assess if host and environmental variables could explain phorid species richness at nest, hectare and locality spatial scales. We used canonical correspondence analysis (CCA) to explore if there were similar responses of phorid species to particular host and environmental variables at different spatial scales, and partial CCA to separate the relative importance of both groups of variables. Results Phorid richness was positively correlated with host richness. Host richness/abundance accounted for 20–53% of the variation in parasitoid richness at the hectare and locality scales of analysis, with most of the variation accounted for by ant abundance. We were not able to assess the prediction at the nest scale as only one phorid species was found at most nests. Climatic variables did not explain phorid species richness once host variables were in the models. Partial CCA showed that host‐related variables accounted for most of the variance associated with phorid species ordination at the nest and hectare scales, but not at the largest grain, the locality, where climatic variables were more important. However, most phorid species did not show particular positions along the climatic gradient. Main conclusions The association between parasitoid richness and host richness and abundance, and the overall weak associations with environmental variables, suggest that these host variables are key factors influencing parasitoid speciation. 相似文献
32.
The black-tailed marmoset (Callithrix argentata melanura) occurs in central-western Brazil and adjacent parts of Bolivia, and is the only member of the genus (Callithrix) to occur naturally outside Brazil. Data presented in this paper extend the range of this marmoset at least 200 km to the southwest into yet another country, Paraguay. 相似文献
33.
A. Magdalena Hurtado Kim Hill Ines Hurtado Hillard Kaplan 《Human nature (Hawthorne, N.Y.)》1992,3(3):185-216
Even though female food acquisition is an area of considerable interest in hunter-gatherer research, the ecological determinants
of women’s economic decisions in these populations are still poorly understood. The literature on female foraging behavior
indicates that there is considerable variation within and across foraging societies in the amount of time that women spend
foraging and in the amount and types of food that they acquire. It is possible that this heterogeneity reflects variation
in the trade-offs between time spent in food acquisition and child care activities that women face in different groups of
hunter-gatherers. In this paper we discuss the fitness trade-offs between food acquisition and child care that Hiwi and Ache
women foragers might face. Multiple regression analyses show that in both populations the daily food acquisition of a woman’s
spouse is negatively related to female foraging effort. In addition, nursing mothers spend less time foraging and acquire
less food than do nonnursing women. As the number of dependents that a woman has increases, however, women also increase foraging
time and the amount of food they acquire. Some interesting exceptions to these general trends are as follows: (a) differences in foraging effort between nursing and nonnursing women are less pronounced when fruits and roots are in season
than in other seasons of the year; (b) foraging return rates decrease for Ache women as their numbers of dependents increase; and (c) among Ache women, the positive effect of number of dependents on foraging behavior is less pronounced when fruits are in
season than at other times of the year. Lastly, in the Hiwi sample we found that postreproductive women work considerably
harder than women of reproductive age in the root season but not in other seasons of the year. We discuss how ecological variation
in constraints, the number of health insults to children that Hiwi and Ache mothers can avoid, and the fitness benefits they
can gain from spending time in food acquisition and child care might account for differences and similarities in the foraging
behaviors of subgroups of Hiwi and Ache mothers across different seasons of the year. Valid tests of the explanations we propose
will require considerable effort to measure the relationship between maternal food acquisition, child care, and adverse health
outcomes in offspring.
This paper is dedicated to Nutsiya, the hardest-working grandmother we ever observed
Kristen Hawkes contributed useful information on female foraging among the Hadza. The research was funded by the National
Science Foundation (BNS-8613215, BNS-538228, BNS-8309834, BNS-8121209) and the L. S. B. Leakey Foundation. The senior author
was supported by fellowships from the Fundacion Gran Mariscal de Ayacucho of Venezuela and the National Institute of Health
(Grant No. 1 RO1 HD16221-01A2).
A. Magdalena Hurtado, Kim Hill, and Hillard Kaplan collaborate in research on the evolutionary ecology of the division of
labor by sex. Ines Hurtado is Senior Research Scientist at the Instituto Venezolano de Investigaciones Científicas, Venezuela.
She studies the immunology of parasite load and atopic illness in Hiwi foragers. 相似文献