DOI: 10.5061/dryad.hqbzkh1kr
title: Intraspecific variation in group structure arises due to environmentally-mediated directional dispersal in a cooperative breeder

description: Many cooperatively breeding species live in groups with complex social
 structure—large group sizes, low but mixed kin structure, and multiple
 breeding pairs—that form as a result of immigration of unrelated
 individuals in addition to offspring delaying or foregoing dispersal.
 Differences in patterns of dispersal can therefore generate variation in
 social structure, even within the same species or population. Yet, the
 mechanisms underlying inter-individual variation in dispersal and
 intraspecific variation in social structure remain poorly studied. Here,
 we examine how environmentally-mediated dispersal patterns inferred from
 genetic data influence variation in social structure in the superb
 starling (Lamprotornis superbus), a complex cooperative breeder that
 inhabits a spatiotemporally variable savanna environment. Using
 genome-wide polymorphic loci and remotely-sensed, fine-scale ecological
 data, we find evidence of not only frequent and long-distance dispersal in
 both sexes (low isolation-by-distance and weak genetic structure), but
 also directional dispersal from small groups occupying low-quality
 territories to large groups occupying high-quality territories. Moreover,
 we find stronger genetic structure among groups in low-quality
 territories, but higher genetic diversity and lower overall relatedness of
 groups in high-quality territories. Long-distance, directional dispersal
 can thus lead to smaller and simpler kin-based social groups in
 low-quality territories, but larger and more complex mixed-kin groups in
 high-quality territories. Thus, individual-level dispersal decisions from
 lower to higher quality habitat that maximize fitness can generate
 intraspecific variation in social structure, even within the same
 population. Such within-population variation in social structure could
 have profound implications for the mechanisms underlying the formation of
 cooperative societies more broadly.
description: ## Intraspecific variation in group structure arises due to
 environmentally-mediated directional dispersal in a cooperative breeder We
 have submitted raw data (**starlings_inds_dryad.csv**,
 **pairwsie.fst.longform_dryad.csv**, **master_group_data_dryad.csv**, and
 **populations.snps_dryad.gen**) and R script
 (**shah_and_rubenstein_dryad_2024.07.01.R**) belonging to Shah S. S. &
 Rubenstein D. R. (2024) Intraspecific variation in group structure arises
 due to environmentally-mediated directional dispersal in a cooperative
 breeder. ## Description of the data and file structure ### Metadata for
 "starling\_inds\_dryad" | Column | Entry | Value | Explanation |
 | ------ | --------- | ----- |
 ------------------------------------------------------------- | | A | ID |
 | unique ID of the individual | | B | Group | | Group IDs for the 22
 superb starling groups part of the study | | C | Latitude | | Latitude | |
 D | Longitude | | Longitude | | E | Sex | M/F | Sex of the individual | |
 F | Age | A, SA | categorical age (A: Adult, SA: Subadult) | ### Metadata
 for "master group data\_dryad" | Column | Entry | Value |
 Explanation | | ------ | ---------------- | --------------------- |
 :---------------------------------------------------------------------------------------------------------------------------------------------------------------- | | A | Site | | group IDs for the 22 superb starling groups part of the study | | B | Region | North, Central, South | geographical zone within Mpala Research Center where the group's territory is located | | C | Latitude | | Latitude | | D | Longitude | | Longitude | | E | r\_group | -0.001 to 0.19 | average relatedness of the group; ranges from 0 or less = unrelated to 1=relatedness to self | | F | r\_females | -0.03 to 0.33 | average relatedness of the females in the group; ranges from 0 or less = unrelated to 1=relatedness to self | | G | r\_males | -0.01 to 0.23 | average relatedness of the males in the group; ranges from 0 or less =unrelated to 1=relatedness to self | | H | mean.NDVI2018 | 0.31 to 0.42 | mean normalized difference vegetation index for the year 2018; higher values indicate more green vegetation | | I | cv.NDVI2018 | 0.21 to 0.41 | coefficient of variation of normalized difference vegetation index for the year 2018; higher values indicate more variation in vegetation greenness over the year | | J | by.humans | yes or no | yes = territory overlaps with permanent human settlement, no = territory does not overlap with permanent human settlement | | K | Obs\_Het | 0.24 to 0.27 | observed heterozygosity | | L | StdErr\_Obs\_Het | 0.003 to 0.004 | standard error of observed heterozygosity | | M | Pi | 0.21 to 0.25 | nucleotide diversity | | N | StdErr\_Pi | 0.002 to 0.003 | standard error of nucleotide diversity | | O | Fis | -0.07 to 0.004 | inbreeding coefficient; values close to 0 indicate lack of inbreeding | | P | StdErr\_Fis | 0.006 to 0.023 | standard error of inbreeding coefficient | | Q | Exp\_Het | 0.196 to 0.238 | expected heterozygosity | | R | StdErr\_Exp\_Het | 0.002 to 0.003 | standard error of expected heterozygosity | ### Metadata for "pairwsie.fst.longform\_dryad" | Column | Entry | Value | Explanation | | ------ | ----------------- | ------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | | A | Group.1 | | group IDs of the first group in the pair | | B | Group.2 | | group IDs of the second group in the pair | | C | Pairwise.Fst | 0.02 to 0.09 | genetic differentiation between group pairs; ranges from 0 to 1 with higher values indicating more genetic differentiation | | D | Group.1.NDVI | | mean NDVI of the first group in the pair | | E | Group.2.NDVI | | mean NDVI of the second group in the pair | | F | Group.1.terr.qual | L or H | L = lower-than-average; H = higher-than-average | | G | Group.2.terr.qual | L or H | L = lower-than-average; H = higher-than-average | | H | Compairson.type | LL, HH, mix | LL = both groups have lower-than-average NDVI; HH = both groups have higher-than-average NDVI; mix = one group has lower- and the other higher-than-average NDVI | ### Metadata for "populations.snps\_dryad.gen" This is a genind object with data on single nucleotide polymorphisms (4,081 loci; 8,162 alleles) for all 235 indvidiauls included in this study. The file can be loaded in R using the function adegenet::read.genepop. The file structure is as follows: @tab: 235 x 8162 matrix of allele counts @loc.n.all: number of alleles per locus (range: 2-2) @loc.fac: locus factor for the 8162 columns of @tab @all.names: list of allele names for each locus @ploidy: ploidy of each individual (range: 2-2) @type: codom @pop: population of each individual (group size range: 6-19) ## Code/Software R is required to run **shah_and_rubenstein_dryad_2024.07.01.R**. The script was created using version 3.6.3.