Diversity and Distributions 13: 53–65
Distributional similarity (congruence) between phylogenetically independent taxonomic groups has important biogeographical as well as conservation implications. When multiple groups show congruence, one or two of them can be used as surrogates of diversity in others; thus, simplifying some of the challenges of area prioritization for conservation action. Here we test for congruence in complementarity between amphibians, reptiles and birds across seven tropical rainforest sites in the Eastern Himalaya and Indo-Burma global biodiversity hotspots. The results show that while frogs and lizards are strongly congruent with each other, birds as a whole do not show congruence with either of them. However, certain bird subgroups delineated on the basis of broad ecological niche and life history attributes are significantly congruent with both frogs and lizards. Multiple Mantel regression between environmental variable and species distribution dissimilarity matrices indicate that along with differential response to between-site ecological differences, inherent life-history characteristics shared by certain groups contributes to observed patterns of congruence. Our analyses indicate that examining biologically distinct subsets of larger groups can improve the resolution of congruence analyses. This approach can refine area-prioritization initiatives by revealing fine-scale discordances between otherwise concordant groups, and vice versa. Given that monetary resources do not always allow inclusion of multiple groups in biodiversity inventorying efforts, performing such analyses also makes economic sense because it can provide better resolution even with single-group data. In the context of conservation in North-east India, the results highlight the biogeographical complexity of the region, and also point at future priorities for biodiversity inventorying and conservation prioritization, both in terms of areas as well as taxonomic groups.