Environmental Uncertainty and the Global Biogeography of Cooperative Breeding in Birds

Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06520, USA.
Current biology: CB (Impact Factor: 9.57). 03/2011; 21(1):72-8. DOI: 10.1016/j.cub.2010.11.075
Source: PubMed


Understanding why organisms as different as amoebas, ants, and birds cooperate remains an important question in evolutionary biology. Although ecology can influence cooperation and conflict within animal societies and has been implicated in species differences in sociality, the environmental predictors of sociality across broad geographic and taxonomic scales remain poorly understood. In particular, the importance of temporal variation in selection pressure has been underestimated in most evolutionary studies. Environmental uncertainty resulting from climatic variation is likely to be an important driver of temporal variation in selection pressure and therefore is expected to impact the evolution of behavioral, morphological, and physiological traits, including cooperation. Using a data set of over 95% of the world's birds, we examine the global geography and environmental, biotic, and historical biogeographic predictors of avian social behavior. We find dramatic spatial variation in social behavior for which environmental and biotic factors--namely, among-year environmental variability in precipitation--are important predictors. Although the clear global biogeographic structure in avian social behavior carries a strong signal of evolutionary history, environmental uncertainty plays an additional key role in explaining the incidence and distribution of avian cooperative breeding behavior.

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    • "Nowadays, differences of perspective more obviously reflect the important taxonomic difference in the nature of cooperative behaviors: investigating direct direct fitness and cost/benefit issues are important where no permanent caste division occurs, while genetic considerations become more important in species in which the allocation to a particular caste is permanent. Thus, vertebrate " helpers, " capable of breeding, typically characterize the former, while studies of social insects have tended to focus on the highly eusocial species that characterize the latter (e.g., Jetz and Rubenstein, 2011; Bourke, 2014). Nevertheless, the similarities between cooperatively breeding vertebrates and the primitively social bees and wasps often remain overlooked, despite the successful application of reproductive skew models (see Nonacs and Hager, 2011) as a shared conceptual framework. "

    10/2015; 3:124. DOI:10.3389/fevo.2015.00124
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    • "In this way , cooperative traits in social spiders appear to be driven by environmental constraints similarly to social mammals or birds ( Emlen , 1982 ; Faulkes et al . , 1997 ; Jetz and Rubenstein , 2011 ) . "

    09/2015; 3(101). DOI:10.3389/fevo.2015.00101
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    • "Despite recognition that the environment shapes animal social behaviour (Krause & Ruxton, 2002; Korb & Heinze, 2008), studies exploring how and why the incidence of animal sociality varies across broad geographical and taxonomic scales are still scarce. Our study, which uses comprehensive environmental data at two spatial scales to tests specific hypotheses about the distribution of spider social systems, joins a few comparative studies (Jetz & Rubenstein, 2011; Purcell, 2011; Majer et al., 2013) that seek to uncover the ecological factors underlying broad geographical patterns of animal sociality. "
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    ABSTRACT: AimTo evaluate the relative importance of environmental factors relevant to specific hypotheses that have been proposed to explain the distribution of social and subsocial Anelosimus spiders in the American continent and Ecuador. For social species, we test the seasonality and prey size hypotheses, which posit that species forming long-lived multifemale colonies require aseasonal conditions and warm and productive environments in which large insects can develop. For subsocial species, we test the rain intensity and predation risk hypotheses, which posit that species whose colonies contain a single female and her offspring cannot occupy areas where strong rains cause frequent damage to their webs and where warm temperatures and high productivity promote greater predation.LocationAmerica, Ecuador.Methods Using generalized linear models, hierarchical variance partitioning, Maxent distribution modelling and phylogenetically controlled regressions, we analysed the relative importance of environmental variables that either directly or indirectly relate to these non-exclusive hypotheses – temperature and precipitation seasonality (seasonality hypothesis), annual temperature and net primary productivity (insect size and predation hypotheses) and rain intensity (rain intensity hypothesis).ResultsTemperature seasonality, followed by annual temperature and rain intensity, were the most important predictors of the distribution of spider sociality across America, whereas temperature and rain intensity predominated in the largely aseasonal Ecuador. In general, social species were associated with lower temperature seasonality, warmer temperatures and higher rain intensity than subsocial species.Main conclusionThe association of social Anelosimus with warm and wet areas in the tropics is consistent with both the seasonality and prey size hypotheses, i.e. both aseasonal conditions and warm temperatures, which allow large insects to develop, are needed for large social colonies to form. That subsocial Anelosimus drop-out from tropical areas with warm temperatures and high rain intensity is consistent with the hypotheses that high predation risk and disturbance by strong rains exclude subsocial Anelosimus from the lowland rain forest.
    08/2015; 24(10). DOI:10.1111/geb.12342
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