Positive Relationships between Association Strength and Phenotypic Similarity Characterize the Assembly of Mixed-Species Bird Flocks Worldwide

Abstract

., et al. 2012. Positive relationships between association strength and phenotypic similarity characterize the assembly of mixed-species bird flocks worldwide. American Naturalist 180: 777-90. AuthorsHari Sridhar, Umesh Srinivasan, Robert A. Askins, Julio Cesar Canales-Delgadillo, Chao-Chieh Chen Submitted February 10, 2012; Accepted August 1, 2012; Electronically published MONTH? xx, 2012 Online enhancement: appendix. Dryad data: http://dx.doi.org/10.5061/dryad.th198.abstract: Competition theory predicts that local communities should consist of species that are more dissimilar than expected by chance. We find a strikingly different pattern in a multicontinent data set (55 presence-absence matrixes from 24 locations) on the composition of mixed-species bird flocks, which are important subunits of local bird communities the world over. By using null models and randomization tests followed by meta-analysis, we find the association strengths of species in flocks to be strongly related to similarity in body size and foraging behavior and higher for congeneric compared with noncongeneric species pairs. Given the local spatial scales of our individual analyses, differences in the habitat preferences of species are unlikely to have caused these association patterns; the patterns observed are most likely the outcome of species interactions. Extending group-living and social-information-use theory to a heterospecific context, we discuss potential behavioral mechanisms that lead to positive interactions among similar species in flocks, as well as ways in which competition costs are reduced. Our findings highlight the need to consider positive interactions along with competition when seeking to explain community assembly.

Insights in the ecology and evolutionary history of the Miscellaneous Crenarchaeotic Group lineage

“…A C-score calculated for each pair of archaeal OTUs was compared with the C-score computed for 5000 randomly assembled null matrices. To avoid biases affecting raw C-score values (that is, OTU number, abundance…), the standardized effect size (SES) was calculated (Sridhar et al, 2012). Because the C-score is an inverse indicator of the frequency of co-occurrence, positive SES values indicate less co-occurrence than expected by chance (that is, predominance of segregation within communities) and vice versa for negative values (that is, predominance of facilitation).…”

Does mixed-species flocking influence how birds respond to a gradient of land-use intensity?

“…2002 -2003, unpublished data). Recent work suggests that birds will associate in flocks with other species of similar body sizes [43]; therefore, we hypothesized that larger birds would prefer joining babbler flocks. To test this hypothesis, we used the phi coefficient as an association measure, calculated by modifying the sp.pair function in the library spaa in R. Other association measures, including the path length (geodesic distance) between nodes in network analyses [44] and simulations of null flocks [45], gave qualitatively similar results (see the electronic supplementary material, methods III).…”

Teleological reasoning about nature: intentional design or relational perspectives?

“…In fact, biologists argue that both human and non-human animals inhabit complex social and mental worlds, and intra-and interspecies cooperative strategies are critical to mutual adaptation and survival [60][61][62][63][64]. Moreover, animals' participation in cooperative socio-ecological systems means that 'other-serving functions' aid own survival.…”