Cross-taxon surrogacy amongst plants, beetles, reptiles, and birds in the context of reforestation in rainforest landscapes

There is growing interest in the potential for reforestation to assist the recovery of rainforest biodiversity. There are many pathways through which tropical forests may return to formerly cleared land, and therefore a need to quantitatively compare the extent to which areas reforested with different methods can support rainforest-associated biota, and to monitor the success of reforestation efforts in achieving biodiversity recovery. Because of prohibitively high costs associated with complete biotic inventories, it is desirable to assess the extent to which various taxonomic groups can act as surrogates for one another in monitoring efforts. We assessed the degree of cross-taxon surrogacy amongst native plants, epigaeic beetles, reptiles, and birds across 104 sites within a range of different reforestation pathways (biodiversity plantings, timber plantations, and regrowth) in Australian rainforest landscapes. Reference sites were cleared pasture and intact rainforest. The richness of rainforest-associated species was positively correlated between all pairwise combinations of taxa across sites. All correlations were statistically significant, but predictive power varied from moderate to relatively weak (r² values 0.57-0.12). Similar patterns were found when Mantel correlations in multivariate assemblage similarity in species composition were used. Strongest between-taxon concordance was found by using an index which combined a forested site’s assemblage similarity to rainforest reference sites with its assemblage dissimilarity to pasture reference sites. Faunal taxa were generally more strongly correlated with native plants than with each other, suggesting that native plant assemblages may be the best single indicator taxon for the recovery of rainforest biota.