To date, invertebrate-derived DNA (iDNA) has been widely utilized to obtain inventories of mammals and other vertebrate groups from tropical regions (e.g. Invertebrate samplers have tended to be haematophagous species, of which arguably the most popular have been leeches (Abrams et al., 2019 Drinkwater et al., 2018 Fahmy et al., 2019 Schnell et al., 2018 Tessler et al., 2018 Weiskopf et al., 2017) and dipteran flies (Calvignac-Spencer et al., 2013 Gogarten et al., 2019 Hoffmann et al., 2018 Kocher, de Thoisy, Catzeflis, Valiere, et al., 2017). One such area that has seen rapid progress is the use of animal-feeding invertebrate species as samplers of vertebrate diversity. In particular, advances in sequencing now allow for the routine metabarcoding of environmental DNA (eDNA) samples, thereby revolutionizing molecular ecology. In recent years, the toolkit for biodiversity monitoring has expanded from solely field-based methods to also encompass molecular techniques. These and other studies of how land-use change relates to biodiversity have increasingly utilized data generated by LiDAR, an approach that allows new and improved opportunities to quantify forest structure and microclimatic variables across spatial scales (Asner et al., 2018 Deere et al., 2020 Seaman et al., 2019). Within heavily logged forest, for example, forest remnants have been shown to be important for birds (Mitchell et al., 2018) and invertebrates (Gray et al., 2014). Even within highly degraded forest, animal community composition tends to be more similar to forest than it is to agricultural plantations (Gray et al., 2014 Wearn et al., 2017). As a result, such forests show lower resilience to numerous local and climatic stressors (Struebig et al., 2015) and are at greater risk of conversion to commodity agriculture (Edwards et al., 2011).ĭespite the well-known negative effects of forest degradation on ecosystem processes, there is evidence that these degraded habitats can still support biodiversity and have considerably greater conservation value than alternative agricultural landscapes (Deere et al., 2017 Gibson et al., 2011). In addition to altering floral and faunal community composition (Laurance et al., 2018 Wilkinson et al., 2018), logged forests can show changes in diverse ecosystem functions, including litter decomposition, predation and seed dispersal (Bovo et al., 2018 Robert M.
For example, microclimatic extremes are more frequent in logged forests than in older growth forests (Blonder et al., 2018 Hardwick et al., 2015 Jucker et al., 2018). The removal of trees, and the associated damage from timber extraction, causes lasting changes to vegetation structure and microclimate, with knock-on consequence for species diversity (Blonder et al., 2018). Tropical ecosystems are under pressure from deforestation (Hansen et al., 2013) and other anthropogenic activities driving forest degradation (Lewis et al., 2015). By revealing differences in mammal diversity across a human-modified tropical landscape, our study demonstrates the value of iDNA as a noninvasive biomonitoring approach in conservation assessments. In addition, our analysis revealed differences between the community recorded in the heavily logged forest and that of the twice logged forest. Although the accumulation curves of diversity estimates were comparable across these habitat types, diversity was higher in twice logged forest, with more taxa of conservation concern. We recorded lower mammal diversity in the most heavily degraded forest compared to higher quality twice logged forest. We screened 557 individual leeches for mammal DNA by targeting fragments of the 16S rRNA gene and detected 14 mammalian genera. Here we use iDNA from blood-feeding leeches ( Haemadipsa picta) to assess differences in mammalian diversity across a gradient of forest degradation in Sabah, Malaysian Borneo. This approach is particularly promising for sampling in the biodiverse humid tropics, where rapid land-use change for agriculture means there is a growing need to understand the conservation value of the remaining mosaic and degraded landscapes. The application of metabarcoding to environmental and invertebrate-derived DNA (eDNA and iDNA) is a new and increasingly applied method for monitoring biodiversity across a diverse range of habitats.
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