Biodiversity loss from deforestation may be partly offset by the expansion of secondary forests and plantation forestry in the tropics. However, our current knowledge of the value of these habitats for biodiversity conservation is limited to very few taxa, and many studies are severely confounded by methodological shortcomings. We examined the conservation value of tropical primary, secondary, and plantation forests for 15 taxonomic groups using a robust and replicated sample design that minimized edge effects. Different taxa varied markedly in their response to patterns of land use in terms of species richness and the percentage of species restricted to primary forest (varying from 5% to 57%), yet almost all between-forest comparisons showed marked differences in community structure and composition. Cross-taxon congruence in response patterns was very weak when evaluated using abundance or species richness data, but much stronger when using metrics based upon community similarity. Our results show that, whereas the biodiversity indicator group concept may hold some validity for several taxa that are frequently sampled (such as birds and fruit-feeding butterflies), it fails for those exhibiting highly idiosyncratic responses to tropical land-use change (including highly vagile species groups such as bats and orchid bees), highlighting the problems associated with quantifying the biodiversity value of anthropogenic habitats. Finally, although we show that areas of native regeneration and exotic tree plantations can provide complementary conservation services, we also provide clear empirical evidence demonstrating the irreplaceable value of primary forests. biodiversity indicators ͉ congruence ͉ conservation ͉ tropical forests ͉ Amazon

The identification of high-performance indicator taxa that combine practical feasibility and ecological value requires an understanding of the costs and benefits of surveying different taxa. We present a generic and novel framework for identifying such taxa, and illustrate our approach using a large-scale assessment of 14 different higher taxa across three forest types in the Brazilian Amazon, estimating both the standardized survey cost and the ecological and biodiversity indicator value for each taxon. Survey costs varied by three orders of magnitude, and dung beetles and birds were identified as especially suitable for evaluating and monitoring the ecological consequences of habitat change in our study region. However, an exclusive focus on such taxa occurs at the expense of understanding patterns of diversity in other groups. To improve the cost-effectiveness of biodiversity research we encourage a combination of clearer research goals and the use of an objective evidence-based approach to selecting study taxa.

The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)—has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

Plantations and secondary forests are becoming dominant components of many tropical forest landscapes. Yet we have an insufficient understanding of the value of these habitats for biodiversity conservation, and almost none for most arthropods in species-rich tropical forests. We sampled epigeic arachnids (Amblypygi, Araneae, Opiliones, Scorpiones, and Uropygi) in primary, secondary ( 14-19 years), and Eucalyptus plantation (4-5 years) forests in the Jari region of northeastern Brazilian Amazonia. We sampled five independent sites in each forest type between January and June 2005, collecting a total of 4824 individuals (3177 adults. 1 12 species), including 1864 adults (75 species) in Eucalyptus, 776 (60) in secondary forest, and 536 (72) in primary forest. We compared species richness, species-abundance distributions, and community structure, between the three forest types and identified the species that were characteristic of each forest type. Rarefaction analyses showed that undisturbed primary forest harbored significantly more species and a similar overall abundance as second-growth forest; while levels of species richness were similar between secondary forest and Eucalyptus. The species composition and abundance structure of arachnid assemblages was distinct in all three forest types. Considering all species sampled, 19% were only sampled in primary forest, 4% in secondary forest, and 19% in Eucalyptus. Most species sampled in plantation forests are known to be wide-ranging habitat generalists. Our data indicate that regenerating forests are not biological deserts (57% and 56% of species sampled in primary forest were also captured in secondary and plantation forests respectively) and can, therefore, help mitigate some of the negative effects of deforestation for epigeic arachnids. However, these replacement habitats do not provide a substitute for primary forest and may fail to conserve many of those species most at risk from extinction.

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