Abstract
Interdependencies in social groups of animals are a combination of multiple pairwise interactions. Heterospecific groups are often characterized by important species that contribute more to group initiation, maintenance or function than other species. However, in large heterospecific groups, many pairwise interactions are not realised, while others may not be biologically significant, confounding inferences about species importance. Hence, in this study, we examine context dependent changes in species importance and assortment in mixed-species bird flocks from a tropical field site in Southern India using social network analysis. Specifically, we ask how the structural importance of a species and the clustering patterns of species relationships depends on species richness in mixed-species flocks. We constructed both raw and filtered networks; while our results are largely correlated, we believe that filtered networks can provide insights into community-level importance of species in mixed-flocks while raw networks depict flock-level patterns. We find significant differences in flocks of different richness in that different species emerge as structurally important across flocks of varying richness. We also find that assortment is higher in two-species flocks and decreases with an increase in the number of species in the flock (‘flock richness’ hereafter). We argue that the link between structural importance of species in mixed-species flock networks and their functional significance in the community critically depends on the social context: namely, the species richness of the mixed-species flock. We propose that examining species structural importance at different flock-richness values provides insights into biologically meaningful functional roles of species. More generally, we suggest that it is important to consider context when interpreting species centrality and importance in network structure.
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The data used in this study is available as supplementary material with the manuscript.
Change history
10 January 2022
A Correction to this paper has been published: https://doi.org/10.1007/s00442-021-05093-5
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Acknowledgements
PB and HS would like to thank Narayan, Nagesh, Sadanand and Chandrakant, Sandeep, Pandurang, Prasad, Bala, Ramdas and Prashant who helped with data collection. HS was supported by a grant from the Indian National Science Academy. LVM was supported by National Science Foundation (NSF) IOS-1750606 to D.S. and NSF DGE-1545261. KS and PB thank the DBT-IISc Partnership Programme for support.
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PB developed this project with guidance from HS and KS. PB and HS collected the data for this study. DS and LVM contributed to discussions related to the analysis. PB and DS analysed this data with inputs from all other authors. PB wrote the first draft of the manuscript. All authors contributed to the following drafts of the manuscript.
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Communicated by Robert L. Thomson.
The original online version of this article was revised: Author affiliation and acknowledgement section updated.
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Bangal, P., Sridhar, H., Shizuka, D. et al. Flock-species richness influences node importance and modularity in mixed-species flock networks. Oecologia 198, 431–440 (2022). https://doi.org/10.1007/s00442-021-05053-z
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DOI: https://doi.org/10.1007/s00442-021-05053-z