Metabarcoding to establish freshwater indicators of environmental degradation in the Indo-Burmese biodiversity hotspot

Biodiversity hotspots of the world are increasingly exposed to anthropogenic pressures and resulting ecosystem breakdowns. However, biotic surveys for ecological status assessment are rarely conducted in poorly characterised, yet highly diverse ecosystems in the tropics and subtropics. Here, we addressed the challenge of developing a monitoring system for the highland streams of the Indo-Burmese biodiversity hotspot in Bangladesh, using a meta-barcoding approach to investigate the impacts of growing anthropogenic pressures on poorly studied invertebrate communities. Species richness and beta diversity in the region were correlated with anthropogenic stressors that varied greatly between sampling sites. A partial-network approach allowed us to identify potential indicator species for either a good or poor ecological status. Overall, our results document high species richness and pronounced responses to disturbance in these unexplored, but threatened habitats. In combination with classical taxonomy approaches, metabarcoding can therefore serve as a valuable tool to rapidly generate lacking baseline information facilitating the conservation of vulnerable ecosystems.

New species and records of Cloeodes Traver, 1938 (Ephemeroptera, Baetidae) from Costa Rica

The nymph of Cloeodes dantasp. nov. is described from male and female nymphs collected from highland streams in the Caribbean Slope of the Costa Rica Central Volcanic Mountain Range. Adults are unknown. In addition, C. excogitatus and C. redactus are recorded for the first time in the country. Cloeodes dantasp. nov. can be differentiated from all described species by the predominantly brownish coloration on females and a similar coloration on males but with segments VII–IX light yellow and light brown, with no conspicuous marks or patterns; abundant scale-bases throughout most parts of the body; hindwings pads absent; the presence of three spines in the corners of the posterior margin of sternum III, and the posterior margin of tergum III with 28–30 spines on each side of the middle line (spine with a base width up to 0.5× spine length).

Gastric mill age estimates for ringed crayfish Faxonius neglectus neglectus (Faxon) and the influence of temperature on band formation

Counting bands via the gastric mill is a potential direct approach for ageing crayfish; however, the validity of ageing crustaceans using the gastric mill is unknown. Our study objectives were to 1) compare gastric mill age estimates to a traditional aging technique, 2) compare ageing precision among the ossicles, and 3) examine the effects of temperature on gastric mill band formation. From 2017–2018, we collected 681 ringed crayfish Faxonius neglectus neglectus (Faxon) from ten Ozark Highland streams. Our length-frequency analysis reflected seven age classes, whereas gastric mill age estimates indicated individuals were up to 10 yr of age. The length-frequency analysis age estimates showed good congruence (± 1 yr) with age estimates from the gastric mill 78% of the time. The coefficient of variation (CV) of age estimates from gastric mill bands between our readers was 29.7%. Ageing precision was highest when using the zygocardiac ossicles (CV = 12.4%). Gastric mill age estimates for known age-1 crayfish from a thermally stable laboratory were not significantly different from one, whereas age estimates from a thermally varying laboratory were greater than one. Our results indicate molting frequency does not control gastric mill band formation, and temperature plays a role in band formation.

Structure and ecological aspects of zooplankton (Testate amoebae, Rotifera, Cladocera and Copepoda) in highland streams in southern Brazil

Aim: This study aimed to characterize the zooplankton structure in highland streams in southern Brazil, Pelotas River sub-basin, as well as the respective relationships with the environmental conditions in the different seasons. Methods Zooplankton was collected using a plankton net (68 µm mesh) and concentrated into a volume of 50 ml for later analysis in the laboratory. Sampling occurred during the winter (August 2013), spring (November 2013), summer (February 2014) and autumn (May 2014). Results Rotifers and testate amoebae were the predominant groups. Mean abundance, diversity and evenness varied considerably between the different seasons. The variability of zooplankton was correlated to environmental conditions (conductivity, suspended solids, pH, temperature and dissolved oxygen). Conclusions The seasonal variation of the zooplankton community made it possible to elucidate some questions involving the ecology of these organisms in highland streams in southern Brazil. These unique ecosystems warrant further research and monitoring efforts, including studies of their hydrological patterns, biological diversity and adaptive mechanisms of the zooplankton community.

Response of benthic invertebrate communities to a land use gradient in tropical highland streams in Nigeria

Benthic invertebrate communities have been shown to respond to habitat degradation as a result of land use changes. Although these changes have been well documented in temperate regions, their effects in the tropics have been poorly documented particularly where land use activities differ markedly (e.g., tea, maize and plantations). A survey 55 1st and 2nd order highland tropical streams, across four land use categories, ranging from continuous tropical montane rain forest to intensive crops and pasture. Streams were sampled in the tropical dry season (October–March) for physico-chemical parameters and components of the biological community, (i.e., fine particulate organic matter [FPOM], coarse particulate organic matter [CPOM], algae and benthic invertebrates). Catchment riparian conditions and human water use activities were used to generate a multivariate land use intensity gradient score. Temperatures in pasture streams were warmer than forest streams (up to 25oC) and dissolved oxygen levels frequently low (15–79%). However, physico-chemical conditions did not show any clear patterns across land uses categories. In contrast, benthic invertebrate communities showed strong response with the highest taxonomic diversity in continuous forest streams (mean 20 taxa) and the lowest in streams with intensive crops (e.g., cabbage crops, mean 8 taxa). Marked changes were found in invertebrate communities with several taxa occurring primarily in forested streams (e.g., the mayflies Heptageniidae and Oligoneuriidae and brachyuran crabs). Tropical land use farming (e.g., tea, maize, cabbage) have significant impacts on the benthic invertebrate assemblages of highland streams in Nigeria. However, not all crop and plantation streams had highly impacted communities because some have wider riparian buffer zones. This study further highlight the importance of conservation and management of montane forest fragments in these regionsKeywords: Tropical, Nigeria, highland, benthic invertebrates, land use, degradation