Tropical freshwater invertebrate species are becoming extinct without being described, and effective conservation is hampered by a lack of taxonomic and distribution data. DNA metabarcoding is a promising tool for rapid biodiversity assessments that has never been applied to tropical freshwater invertebrates across large spatial and taxonomic scales. Here we use DNA metabarcoding to comprehensively assess the benthic freshwater invertebrate fauna of the Perak River basin, Malaysia. Specific objectives were to: (1) assess performance of two DNA metabarcoding protocols; (2) identify gaps in reference databases; (3) generate new data on species diversity and distribution; and (4) draw conclusions regarding the potential value of DNA metabarcoding in tropical freshwater conservation. Organisms were collected by hand and net at 34 sites and divided into small (retained in 0.5‐mm but passing through 1‐mm mesh) and large (retained in 1‐mm mesh) fractions, and a 313‐bp cytochrome c oxidase subunit I fragment amplified and sequenced using general Metazoa primers. Bioinformatic analysis resulted in 468 operational taxonomic units (~species) from 12 phyla. Only 29% of species could be assigned binominal names through matches to public sequence libraries, indicating varying levels of library completeness across Orders. Extraction of small‐fraction DNA with a soil kit resulted in a significantly higher species count than with a general kit, but this was not even across taxa. Metabarcoding (amplification) success rate, estimated via comparison to morphological identifications of the large‐fraction specimens, was high in most taxa analysed but low, for example, in ampullariid and viviparid gastropods. Conversely, a large proportion of species‐site records for Decapoda and Bivalvia came from metabarcoding only. Species richness averaged 29 ± 16 species per site, dominated by Diptera, Annelida, and Odonata, and was particularly high in tributaries of the mountainous Titiwangsa Range. At least eight species are new records for Malaysia, including the non‐natives Ferrissia fragilis (Gastropoda) and Dugesia notogaea (Platyhelminthes). Our study showed that DNA metabarcoding is generally more effective in detecting tropical freshwater invertebrate species than traditional morphological approaches, and can efficiently improve knowledge of distribution patterns and ranges of native and non‐native species. However, current gaps in reference databases, particularly for bioindicator taxa, such as the Plecoptera, Ephemeroptera, and Coleoptera, need to be addressed urgently.
Over half of the cigarettes sold in Singapore contain added flavors such as menthol. We conducted nine focus group discussions (n = 46) with young (age 20-25) current smokers in Singapore to understand the role of flavors in smoking initiation. We found that flavors triggered the curiosity to experiment with tobacco and e-cigarette products and played an important role in the formation of early cigarette preferences. Menthol-flavored cigarettes were the most appealing to participants due to their smoothness and cooling sensation, described as pleasant against Singapore’s hot and humid climate. While some participants believed that flavored and nonflavored cigarettes were equally harmful, others believed that flavored variants had a lower nicotine content and were therefore less harmful, or that the added chemicals in flavored cigarettes could result in higher toxicant exposures. Thus, among young people in Singapore, flavors appear to play an important role in smoking initiation and there appear to be various misperceptions regarding their harmfulness.
1. Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.2. Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.3. This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia.Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.4. Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance.Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.5. These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.
Eriocheir hepuensis Dai, 1991, the Hepu mitten crab, is here formally reported from Thanh Hoa and Quang Ninh Provinces, northern Vietnam. Previous reports of “E. sinensis” and “E. japonicus” from “Cua lông”, Thai Binh Province, northern Vietnam, require clarification, are probably misidentifications of E. hepuensis, and highlight the problems of species identification within Eriocheir. The taxonomy of E. hepuensis is also discussed.
Freshwater decapod crustaceans, with representatives from four main taxonomic groups (Anomura, Astacidea, Brachyura, Caridea), form a large and prominent functional group distributed globally across all types of freshwater habitats. Freshwater decapods play critical ecological roles in aquatic communities and ecosystems, and at the same time have widespread cultural and economic significance. A large proportion of freshwater decapods are imperilled by threats including pollution, habitat loss, invasive species, and importantly, climate change. Direct impacts of climate change, as well as its synergistic effects with other threats, pose a substantial but potentially understudied and possibly even underestimated risk to the conservation of freshwater decapod crustaceans. We assessed patterns of climate change impacts on freshwater decapods, as well as the extent of related research, at a global scale. Based on a comprehensive literature survey of all years up to November 2019, we found that only 49 publications, starting from the first relevant article in 2003, contained empirical evidence of climate change effects on freshwater decapods, with a total of 145 native and 11 non-native freshwater decapod species studied in relation to climate change. Climate-change research has also been increasing for all four groups, but more than half of the literature included the freshwater crayfishes Astacidea. We also found a strong bias towards the Australasian region in climate-change research in freshwater decapods, while no published studies were recorded in the Oceania biogeographic region. Importantly, almost three-quarters of native freshwater decapod species studied were projected/reported to be significantly affected by climate change, while more than 90% of the non-native freshwater decapod species studied were projected/reported to be significantly affected by climate change. Considering the severe impacts demonstrated for several species, and coupled with the notable taxonomic and geographic gaps in research into the rest of the freshwater decapods, there is an urgent need for greater representation in climate-change research across species and in regions of high diversity (such as the Neotropical, Afrotropical, and Indomalayan regions), in order for conservation interventions and measures to be beneficial to the most threatened groups.
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