Fig. 6

Mean NTI of microbiota of sympatric woodlark and skylarks. The nearest taxon index (NTI) describes the standardised effect size of the observed mean distance to the nearest taxon for all taxa in a community compared to a null distribution. NTI is calculated for each sample and is depicted per sample type and for each lark species separately. Mean NTI values that are significantly different from zero (alpha = 0.05) characterise non-random phylogenetic structure where negative values denote significant phylogenetic overdispersion and positive values denote phylogenetic clustering of bacterial OTUs at the tips of the phylogenetic tree. Sample type means (black circles) and 95% confidence intervals (whiskers) are shown per group