The signatures of panmixia and disjunction Our genetic and bioacoustic data indicate strong differentiation among local populations of Z. poliogaster from isolated mountains. These deep genetic and bioacoustic splits found in conspecific populations of Z. poliogaster even exceeded the level of divergence between the highland and lowland species. In parallel, the genetic and bioacoustic variability found within each population of Z. poliogaster is rather low. In contrast to these strong intraspecific signatures observed for Z. poliogaster, the lowland Z. abyssinicus showed a contrasting pattern: no differentiation neither genetically, nor bioacoustically, accompanied by high levels of intra-population variation. The genetic and bioacoustic patterns reflect the two opposite distribution settings of the taxa: the lowland species has a continuous distribution across the lowland savannahs. This suggests a panmictic or metapopulation-like structure with interconnected local populations. The high intraspecific variability is maintained in an interconnected population network (i.e. high rates of gene flow) of large populations. The opposite scenario applies to Z. poliogaster, where local populations show strong genetic and bioacoustic differentiation, but comparatively low levels of genetic and bioacoustic variability within single populations or groups. This might be the result of long term isolation at geographically separated mountain exclaves with rather small population sizes. The combination of population differentiation and low variation is a typical feature found in species with highly disjunct occurrences (Habel et al. 2013a). Complex differentiation with patterns in Zosterops poliogaster The bioacoustic and genetic differentiation patterns of Z. poliogaster differ from each other. While our molecular data showed no correlation between the genetic and geographical distance, the bioacoustic data showed similarities in geographically close populations,
Appendix S1: Results of the Structure analysis. Ln(Pr) calculated using the Structure software (white dots) that K is the correct number of populations. The ad-hoc statistic ∆K (black cubes) based on the rate of change in the log probability of data between successive K values (Evanno et al. 2005), is not applicable for K=1, and from the equation given in the methods section it is obvious that it cannot be calculated for the highest K number either (because data for K=1 are needed); we further ignore the high ΔK value obtained for K=2 as suggested by Hausdorf and Hennig (2010). Appendix S2: Analyses of molecular variance (AMOVA) to detect genetic differentiation between the two species, Zosterops poliogaster and Z. abyssinicus, and the differentiation within Z. poliogaster (mountain massifs). Variance values in top line with respective F statistic values (in parenthesis below). Abbreviations: *: p < 0.05; **: p < 0.01; ***: p < 0.001. Respective R-statistics is given Table 3. Group Among groups or species (FCT) Among populations within groups (FSC) Within individuals All Z. abyssinicus vs all Z. poliogaster 0.2440 (0.0815*) 0.8066 (0.2933***) 1.7004 Z. poliogaster (according K = 4) 0.4493 (0.1589***) 0.3524 (0.1482***) 1.6833 Z. poliogaster five mountain areas 1.0142 (0.36595***) 0.0945 (0.0538***) 1.4255
Appendix S3: Matrix of pairwise geographic distances (in km) among all locations and matrix of pairwise genetic distances based on & Edwards (1976) and pairwise Rst-values among all populations analysed for Zosterops poliogaster. Mt. Kulal Aberdares CH- Satellite CH- Simba V. TH- Mbololo TH- Ngangao TH- Chawia TH- Mt. Kasigau Geographic distances Mt. Kulal - 277.29 554.91 497.69 555.11 553.17 562.99 621.53 Aberdares 319.90 252.35 316.96 313.77 322.99 386.89 CH-Satellite 69.68 9.25 13.43 15.84 67.71 CH-Simba Valley 65.26 61.74 70.72 134.91 TH-Mbololo 4.52 8.98 69.93 TH-Ngangao 9.83 73.20 TH-Chawia 64.29 TH-Mt. Kasigau - Cavalli-Sforza & Edwards (1976) Mt. Kulal 0.000 0.313 0.381 0.388 0.451 0.449 0.444 0.452 Aberdares 0.000 0.383 0.402 0.407 0.416 0.402 0.437 CH-Satellite 0.000 0.158 0.443 0.448 0.419 0.479 CH-Simba Valley 0.000 0.424 0.442 0.430 0.480 TH-Mbololo 0.000 0.122 0.194 0.222 TH-Ngangao 0.000 0.149 0.171 TH-Chawia 0.000 0.235 TH-Mt. Kasigau 0.000 Pairwise Rst-values Mt. Kulal 0.00000 Aberdares 0.06739 0.00000 CH-Satellite 0.12212 0.16422 0.00000 CH-Simba Valley 0.36561 0.10798 0.05774 0.00000 TH-Mbololo 0.68427 0.53206 0.04359 0.72115 0.00000