Deep Narayan Shah

Climatic and Catchment-Scale Predictors of Chinese Stream Insect Richness Differ between Taxonomic Groups

Little work has been done on large-scale patterns of stream insect richness in China. We explored the influence of climatic and catchment-scale factors on stream insect (Ephemeroptera, Plecoptera, Trichoptera; EPT) richness across mid-latitude China. We assessed the predictive ability of climatic, catchment land cover and physical structure variables on genus richness of EPT, both individually and combined, in 80 mid-latitude Chinese streams, spanning a 3899-m altitudinal gradient. We performed analyses using boosted regression trees and explored the nature of their influence on richness patterns. The relative importance of climate, land cover, and physical factors on stream insect richness varied considerably between the three orders, and while important for Ephemeroptera and Plecoptera, latitude did not improve model fit for any of the groups. EPT richness was linked with areas comprising high forest cover, elevation and slope, large catchments and low temperatures. Ephemeroptera favoured areas with high forest cover, medium-to-large catchment sizes, high temperature seasonality, and low potential evapotranspiration. Plecoptera richness was linked with low temperature seasonality and annual mean, and high slope, elevation and warm-season rainfall. Finally, Trichoptera favoured high elevation areas, with high forest cover, and low mean annual temperature, seasonality and aridity. Our findings highlight the variable role that catchment land cover, physical properties and climatic influences have on stream insect richness. This is one of the first studies of its kind in Chinese streams, thus we set the scene for more in-depth assessments of stream insect richness across broader spatial scales in China, but stress the importance of improving data availability and consistency through time.

Range shifts of a relict Himalayan dragonfly in the Hindu Kush Himalayan region under climate change scenarios

Although understanding of geographic range shifts of many species in response to global climate change is expanding steadily, little is known about the Himalayan fauna, which in particular is affected by relatively faster warming rates than other parts of the world. Anticipated increases in temperature and changes in hydrological regimes will have significant adverse impacts on the habitat suitability for many species. This threat will even be higher to endemic and already threatened species due to their restricted distribution and narrow climate tolerance ranges. We investigated the range shifts of a relict Himalayan dragonfly (Epiophlebia laidlawi), a species that is endemic to the Hindu Kush Himalayan region. Currently, the species is only known from few localities in Bhutan, India and Nepal. For conservation of the species, it is necessary to foresee potential suitable habitat areas and range shifts due to global climate change. Here, we first estimated the current potential geographic distribution by identifying the suitable habitat area in the region using bioclimatic envelope models, by means of consensus projections of six algorithms as implemented in the BIOMOD-package in the software program R. We then used the current distribution to render future projections under the A2a and B2a IPCC emission scenarios for the years 2050 and 2080. Models predict that the suitable habitat area of the species will shift on average 374 m and 599 m uphill under the extreme (A2a) climate warming scenario, and 294 m and 342 m uphill under the moderate (B2a) scenario by 2050 and 2080, respectively. Future suitable habitat areas are projected to remain only in the high mountains of eastern Nepal. The results will help conservationists to delineate priority habitats in the first step towards the species conservation in the region.

Phylogeographic Analysis Elucidates the Influence of the Ice Ages on the Disjunct Distribution of Relict Dragonflies in Asia

Unusual biogeographic patterns of closely related groups reflect events in the past, and molecular analyses can help to elucidate these events. While ample research on the origin of disjunct distributions of different organism groups in the Western Paleartic has been conducted, such studies are rare for Eastern Palearctic organisms. In this paper we present a phylogeographic analysis of the disjunct distribution pattern of the extant species of the strongly cool-adapted Epiophlebia dragonflies from Asia. We investigated sequences of the usually more conserved 18 S rDNA and 28 S rDNA genes and the more variable sequences of ITS1, ITS2 and CO2 of all three currently recognised Epiophlebia species and of a sample of other odonatan species. In all genes investigated the degrees of similarity between species of Epiophlebia are very high and resemble those otherwise found between different populations of the same species in Odonata. This indicates that substantial gene transfer between these populations occurred in the comparatively recent past. Our analyses imply a wide distribution of the ancestor of extant Epiophlebia in Southeast Asia during the last ice age, when suitable habitats were more common. During the following warming phase, its range contracted, resulting in the current disjunct distribution. Given the strong sensitivity of these species to climatic parameters, the current trend to increasing global temperatures will further reduce acceptable habitats and seriously threaten the existences of these last representatives of an ancient group of Odonata.

Development of a macroinvertebrate-based Nepal Lake Biotic Index (NLBI): an applied method for assessing the ecological quality of lakes and reservoirs in Nepal

In Nepal, the impairment status of lakes and reservoirs has generally been measured and classified based on nutrient concentrations and physico-chemical parameters, typically with no direct measurement of biological communities. In response to the recent focus on the bioassessment of lakes and reservoirs, the macroinvertebrate-based Nepal Lake Biotic Index (NLBI) has been developed. Benthic samples were collected from reference and impaired lakes during 2006 and 2009 from two ecological zones: Terai-Siwaliks and Mid-Hills. We used a tolerance score based on a ten-point scoring system ranging from very pollution sensitive to very pollution tolerant taxa to calculate the NLBI. In reference to the transformation scale, the calculated NLBI describes the lake water quality as high, good, fair, poor and bad. Candidate metrics of richness measures and tolerance measures discriminated well between the reference and impaired lakes (Mann-Whitney U test, p < 0.01). The relationships between the biological metrics and the environmental variables were also established with the lake water quality class (LWQC). Further, the validation of the NLBI performance was done by assessing nine lakes/reservoirs from both the zones. Thus, the index presented here provides an effective method to measure the ecological condition of lakes and reservoirs in Nepal.

Current and Future Latitudinal Gradients in Stream Macroinvertebrate Richness Across North America

Abstract: Freshwater ecosystems are highly vulnerable to warming climates. However, macroecological studies of climate-change effects on aquatic biodiversity are rare because of a lack of standardized large-scale surveys, e.g., along large latitudinal gradients. Our goal was to assess the overall richness pattern and projected differences in present and future patterns of the stream insect orders Ephemeroptera (E), Plecoptera (P), Trichoptera (T), and combined EPT along an extensive latitudinal gradient across North America (30 to 70° N). We applied Bioclimatic Envelope Models (BEMs) to project present-day and future climatically suitable areas for EPTs on a spatial resolution of 10 arc-min (20 km × 20 km) across North America. To overcome issues related to spatially biased sampling, we assessed climatically suitable areas (CSAs) for each genus and modeled potential generic richness/grid cell, rather than assessing observed generic richness patterns directly. Projected present-day generic richness was greatest between 40 and 48°N latitude, with peaks at 44, 45, and 47°N for the E, P, and T orders, respectively. Our models projected that CSAs would shift an average 4.2 to 5.2°, 4.4 to 5.3° and 3.4 to 4.1°N latitude by 2080 for E, P, and T genera, respectively. Overall, the present-day projected generic EPT richness is highest in the warm and cool temperate zones and shows a unimodal richness pattern that is projected to shift northward under climate-change conditions. A similar northward shift of richness patterns might also apply to other aquatic insects with relatively narrow thermal sensitivity and terrestrial, winged adults, e.g., freshwater Diptera or many aquatic Coleoptera. This large-scale application of genus-by-genus models gives a first approximation of the likely consequences of climate-change effects on freshwater biota across North America.

Evaluation of benthic macroinvertebrate assemblage for disturbance zonation in urban rivers using multivariate analysis: Implications for river management

River pollution has tremendously increased in the major cities of South Asia, where the rivers have become a repository for domestic, agricultural, municipal and industrial wastes. This study presents the evaluation of benthic macroinvertebrate assemblage as a means of assessing ecological status, determining different disturbance zones and identifying environmental variables and stressors that deteriorate the river ecosystem. In total, 20 sites in 36-km stretch of the main stem of the Bagmati River and 7 sites on its tributaries were selected for sampling in the post-monsoon and pre-monsoon seasons during the time period 2008–2010. The Ganga River System Biotic Score (GRSbios) index was applied to determine the ecological status. The ecological status of the different Bagmati River stretches ranged from reference (Class 1) to extremely polluted (Class 5). We identified three types of disturbance zones along the river, ranging from minimally polluted to extremely polluted. A river corridor survey was conducted to identify any river stressing factors, revealing a sharp deterioration of the river from upstream to downstream with increasing concentrations of chloride and ortho-phosphate phosphorus. Effluents and Activities and Facilities were found to be the major stressing factors to the river ecosystem. The information gained should help water managers find the most time-efficient and cost-effective measures to address river degradation.