COS 58-1
Interactive effect of disturbance gradient and regional context on cross-taxa congruence of birds, bryophytes, mites and vascular plants
Cross-taxon congruence implies that diversity patterns of different taxonomic groups covary spatially due to shared response patterns to underlying ecological and biogeographical processes. Such similarities in community structure and underlying causes frequently form the basis to use certain surrogate, often well-known, taxa to assess and monitor trends of overall biodiversity of other taxa congruent with them. The utility of surrogate taxa for biodiversity assessment assumes that the congruence between the monitored taxon and the other taxa of interest remains consistent across the study region and ecological gradients; but this assumption is not well understood. Here, we examine how gradient of anthropogenic disturbance and regional context interactively might influence the strength of cross-taxon congruence among four taxonomic groups (vascular plants, birds, mites, and mosses) in two distinct Alberta ecoregions: the Boreal (128 sites) and the Grasslands (120 sites) using broad scale data collected in Alberta, Canada. We also examine change in cross-taxon congruence strength across a wide range (low to high) of anthropogenic disturbance intensity. We calculate congruence in species composition using Procrustes and Mantel tests and conduct resampling without replacement to generate confidence intervals and compare congruence strength between high and low disturbance sites. Together, these analyses allow us to: 1) assess whether disturbance influences cross-taxa congruence and (2) cross-taxon congruence is consistent across ecoregions
Results/Conclusions
In both ecoregions, congruence between taxa was higher when the full disturbance gradient across sites was considered compared with analysis restricted to sites with either high or low disturbance levels. We found congruency was stronger in high than in low disturbance sites in the Boreal, but found the reverse pattern in the Grassland. These relationships suggest that disturbance gradient length and intensity influence cross-taxon congruence through their effects on the size of species pools and assembly of ecological communities. Moreover, regional context can influence (or even reverse) the relative strength of cross-taxon congruence along disturbance gradients and hence may fundamentally limit on the utility and transferability of surrogates for biodiversity monitoring across regions. Long-term biodiversity monitoring will prove more effective if multiple biota characteristics of the biogeography and ecology regime are monitored.