RESEARCH

Drivers & Repercussions of UK Insect Declines

Insect populations face pressures from multiple drivers including intensified land use, climate change, pollution, and novel pests and pathogens. While these drivers have long been recognized, research into the complex, potentially interacting effects of drivers acting in combination is lacking. Despite growing public concern, there is remarkably little hard evidence of general, cross-taxon insect declines in the UK or abroad. In DRUID, we will bring together the widest possible set of standardised monitoring data with two contrasting sets of more spatially comprehensive data: modelled occupancy and abundance estimates from species records in biodiversity databases, and novel biomass, abundance and morphodiversity estimates from post-processed radar data. Using these data, we will assess the drivers of change in terrestrial and aquatic insect populations and communities and fully quantify the links between these populations and natural capital. As the postdoctoral fellow at Leeds, I am involved in the assessments of freshwater insect communities & the radar-derived biological data. YOu may read more about our ongoing work at DRUID and BioDAR

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Hawkmoths of Eaglnest Wildlife Sanctuary - An Inventory

This page contains a comprehensive photo gallery (along with the keys used for species delineation) of over 70 hawkmoth morphospecies which were encountered during my doctoral work in Eaglenest Wildlife  Sanctuary. Hawkmoths are easy to distinguish from species of other moth families even on a screen thereby reducing sampling effort in the field. The ability to identify the family at a glance meant that none of the other thousand moths on the screen had to be examined or processed, and we had an immediate count of the sampling success for each day. Sphingids have been the targets of considerable taxonomic studies and we have a better knowledge of their geographical distributions, compared to other families, largely through the on-going efforts of Ian Kitching and his team of collaborators (Kitching 2017). Ironically, the lower species richness of hawkmoths compared to most other macrolepidopteran families – 1500 extant hawkmoth species, contra ~23,000 Geometridae (Scoble and Hausmann 2007) or ~35,000 Noctuidae (Quimbayo et al. 2010) – is an advantage in diversity studies. The rate limiting step in studies of tropical insect diversity is specimen identification (Brehm et al. 2003; Brehm et al. 2016), which may not even be possible at the level of species without DNA-based identifications for many groups and may lead to erroneous measures of diversity (Brehm et al. 2016). Our study is part of a much larger biodiversity project to investigate patterns in distribution of many other taxa (ongoing projects on other moth families, frogs and ants)

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Top. An illuminated moth screen which was designed for my PhD work. Bottom: Two representative images for hawkmoth species in a resting pose on the moth screen fabric.

Photogrammetric method for obtaining morphological traits of free-ranging moths

Photogrammetric studies of free-ranging animals are limited to mammals and birds. Recent advances in insect photogrammetry, including 3D imaging, are entirely associated with museum specimens. We present a rapid, simple, accurate, and inexpensive morphometric method targeting thousands of free-ranging insects attracted to light screens using images taken without collecting a specimen or even constraining the individual in any manner. A reference grid printed on the screen is used to calibrate the images for shape and size without prior knowledge of the camera-subject configuration. The method requires only inexpensive, off-the-shelf, consumer equipment, and freely available programming (R statistical language) and image processing (ImageMagick) tools. We demonstrate the efficacy of the method using a dataset of 3675 images of free-ranging hawkmoths (Lepidoptera:Sphingidae) imaged in natural repose on a screen. We show that this method introduces no bias and has a high degree of correspondence with traditional morphometry using collected specimens. We also propose error metrics, which quantify the calibration quality and identify images with poor data. Although this method is particularly suited for the hyperdiverse moth community, which dominates the dynamics of many terrestrial ecosystems, it can be used for other phototropic taxa identifiable on an image to (morpho)-species. It will help in accumulating reliable trait data from hundreds of thousands of individual insects without any expenditure on specimen collection. It is particularly suited for studies which require multi-epoch, multi-locate sampling like investigations into ecosystem stability, climate change, and community assembly.

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A cartoon illustrating the landmark digitization locations for the developed photogrammetric method. 

Taxonomic scale dependency of Bergmann’s patterns: A cross-scale comparison of hawkmoths and birds along a tropical elevational gradient

Bergmann’s rule predicts a larger body size for endothermic organisms in colder environments. The confounding results from previous studies may be due to the differences in taxonomic (intraspecific, interspecific and community) and spatial (latitudinal vs elevational) scales. We compared Bergmann’s patterns for endotherms (Aves) and ectotherms (Lepidoptera: Sphingidae) along a same 2.6 km elevational transect in the eastern Himalayas. Using a large data spanning 3,302 hawkmoths (76 morpho-species) and 15,746 birds (245 species), we compared the patterns at the intraspecific (hawkmoths only), interspecific and community scales. Hawkmoths exhibited positive Bergmann’s pattern at the intraspecific and abundance-weighted community scale. Contrary to this, birds exhibited a strong converse-Bergmann’s pattern at interspecific and community scales, both with- and without-abundance. Overall, all metrics which incorporate local traits and/or species abundances show stronger correlations than when this information is lacking. The multiplicity of patterns at a single location provides the opportunity to disentangle the relative contribution of individual- and species-level processes by integrating data across multiple nested taxonomic scales for the same taxa. We suggest that future studies of Bergmann’s patterns should explicitly address taxonomic- and spatial-scale dependency, with species relative abundance and intraspecific trait variation as essential ingredients especially at short elevational scales.

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Three hypothetical scenarios are shown to illustrate a positive Bergmann’s pattern at three taxonomic scales: intraspecific (BR-I), interspecific (BR-S) and community (BR-C). Each circle represents an individual, colors represent different species, and the size of the circle is proportional to the body size of the individual. a). BR-I: In the intraspecific approach, individuals of the same species are measured at different points along a temperature gradient, and individuals observed at higher temperatures exhibit lower body size; b). BR-S: In the interspecific approach, multiple species are recorded along a temperature gradient, and overall smaller species are observed at higher temperatures; c). BR-C: In the community approach, all individuals within a pre-defined grid (or latitudinal / elevational belt) are measured and community mean body size is lower at higher temperature. The BR-C pattern can occur due to i). Intraspecific variation (e.g. individuals of red species are becoming smaller with increasing temperature); ii). Interspecific variation (e.g. blue species is replaced by the smaller orange species, which is further replaced by the even smaller grey species), or due to iii). Variation in species abundances (e.g. the green species of constant body size is
found across the breadth of the gradient, however its abundance is higher in the community at higher temperatures).

Intraspecific trait variability and community assembly in  hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas, India

We investigated some aspects of hawkmoth community assembly at 13 elevations along a 200-2770 m transect in the eastern Himalayas, a little studied biodiversity hotspot of global importance. We measured the morphological traits of body-mass, wing-loading, and wing aspect-ratio of 3301 free-ranging individuals of 76 species without having to collect or even constrain them. We used these trait measurements and T-statistic metrics to assess the strength of intra-community (“internal") and extra-community (“external”) filters which determine the composition of communities vis-a-vis the regional pool of species. The trait distribution of constituent species turned out to be non-random subsets of the community trait distribution, providing strong evidence for internal filtering in all elevational communities. The external filter metric was more ambiguous. However, the elevational dependence of many metrics including that of the internal filter, provided evidence for external (i.e. environmental) filtering. On average, a species occupied as much as 50-75% of the total community trait space; yet the T-statistic metric for internal filter was sufficiently sensitive to detect a strong non-random structure in the trait distribution. We suggest that the change of T-statistic metrics along the environmental gradient may provide more clues to the process of community assembly than previously envisaged. A large, smoothly varying and well sampled environmental span would make it easier to discern them. Developing T-statistics for combined analysis of multiple traits will perhaps provide a more accurate picture of internal/filtering and niche complementarity. Moths are a hyper-diverse taxon and a very important component of many ecosystems. Our technique for accurately measuring body and wing dimensions of free-ranging moths can generate trait database for a large number of individuals in a time- and resource-efficient manner for a variety of community assembly studies using this important taxon.

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The plots show the standardised effect sizes (SES) of T-statistics metrics for body mass (BM), wing loading (WL), and wing aspect ratio (AR) for each of the 13 elevational communities. The vertical bars represent the 95% distribution of simulated null communities, and the dots are the observed values. The metrics are variance ratios of (a) TIP/IC: intra-population to intra-community (b) TIC/IR: intra-community to regional, assessed using individual trait values, and (c) TPC/PR: intra-community to regional, assessed using population mean values. See text for more details.

Functional randomness despite high taxonomic turnover across a broad elevational gradient in a global biodiversity hotspot: A case study of hawkmoths and birds

We examined the patterns and processes of taxonomic and functional dissimilarities for two disparate organismal groups (ectothermic hawkmoths and endothermic birds) across a broad tropical elevational gradient. Turnover and nestedness components for taxonomic and functional dissimilarities were obtained using the methods developed by Baselga (2013) and Leprieur et al., 2012. We used Generalized Dissimilarity Modeling (GDM) with geographic distance, contemporary and historic climatic variables to assess the relative importance of dispersal and environmental processes in determining the two facets of beta diversity. Functional redundancy (FRed) was calculated for both organismal groups using the Simpson’s diversity indices. Null modeling was used to determine randomness in species and trait distributions.Turnover dominated taxonomic and functional dissimilarities, however the contribution of nestedness was considerably higher to the latter. Overall, the rate of dissimilarity with distance, for both facets of diversity, was significantly higher for birds, with stronger contributions of geographic distance and historic climate; whereas the hawkmoth dissimilarities were strongly correlated with only contemporary climate. Taxonomic dissimilarities deviated significantly from null, whereas functional dissimilarities exhibited high redundancy and randomness. Communities for both taxa exhibited high functional redundancy. Overall, our results suggest that while the drivers of beta-diversity exhibit idiosyncrasy and taxon-specificity; for a given taxa, they are consistent across the two facets of dissimilarity. More importantly, regardless of the principal predictor, the net result was that of high taxonomic turnover, which is de-coupled to a high degree from functional turnover in these tropical ecosystems. The large redundancy in trait values, despite high species turnover, indicates functional resilience of these tropical communities. The consistency of this pattern, across two disparate organismal groups, is suggestive of a key mechanism in which tropical communities may retain functionality of ecosystems in a changing environment.

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Relationship between observed functional dissimilarity of each elevational-site pair for a). hawkmoths, and b). birds, with the fitted predictor from the GDM (predicted ecological distance between elevational-site pairs); Partial regression fits (I-splines) for the different predictors significantly associated with either hawkmoth (blue) or bird (red) functional dissimilarities are shown in plots c) through h). The maximum height and shape of each function provides an indication of the independent contribution of the predictor and variation in it’s strength along the environmental gradient. Relative importance of each predictor, obtained from the scaled values of the maximum height of the corresponding I-spline functions is shown in i).

Change in species relative abundance profiles along a 2600 m elevational gradient: Consistency in patterns or mechanisms?

The distribution of individuals across species, also known as Species Abundance
Distribution (hereafter SAD), is a fundamental property of an ecological community, next only to species richness and diversity. Indeed, some indices of species diversity are based on the SAD (e.g. Fisher 1943). A SAD is the vector of abundances of all species present in the community and this distribution can be plotted in a variety of ways to facilitate visual comparisons amongst communities. In fact, the diversity of plotting forms used to depict SADs sometimes hinders comparative analysis across studies (Magurran 2004). We have shown that evenness of species abundances within a community decreases with elevation for both hawkmoth and birds. The decline in evenness was consistent across multiple measures including parameters from models (e.g. standard deviation of a Log-normal fit), as well as model-independent metrics such as the width of the octave binned species abundance distributions, slope of rank-abundance curves and Pielou's evenness index. High evenness has been previously observed in stable, more productive ecosystems with high species richness and more resource/niche partitioning (like at low elevations and latitudes), whereas low evenness is linked to unstable, variable and less productive environments where few species dominate (like at high elevations and latitudes). We also found that the Log-series and Neutral models fit the individual elevational communities of hawkmoths the best, while bird communities are more mixed with Log-normal dominating the fits. However, for the regional pool as a whole the Log-normal was by far the best fit for both taxa. Models of SAD are directly related to processes of community assembly (MacArthur 1957; Fisher 1943; Preston 1948; Tokeshi 1994; Hubbell 2001; McGill et al. 2007; Chen et al. 2012). Theoretical as well as empirical studies use these models to investigate the relative importance of niche vs neutral mechanisms. Investigations of SADs along environmental gradients have typically either fit a model and tested the change of model parameters (Ulrich et al. 2016; Arellano et al. 2017), or confined themselves to largely qualitative descriptions of the change in RACs between different sites (e.g. Whittaker 1965; James & Rathbun 1981; Ellis & Betts 2011). Unlike beta diversity, SADs can also be used to demonstrate the response of a community pattern along an environmental gradient even when the different communities have no species in common. Most studies have shown a strong decline in evenness with latitude which is consistent with the hypothesis that stable, more productive habitats contain more even communities with more equitable abundance distribution (Ulrich et al 2016). (Manuscript under preparation)

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Rank-abundance curves for individual elevational communities
for birds (top row) and hawkmoths (bottom row), at the level of species, genus and family (birds only). The colors represent four elevational bins (Blue: highest; Yellow: lowest).

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Correlation between the widths of Parameter of the log-normal
fit and of the octave binned SAD for hawkmoths (blue)
and birds (red) at the level of species, genus and family.

Comprehensive Human-Wildlife Conflict (HWC) Management Strategy in select Districts / Landscapes of Uttarakhand

HWC is a widespread and globally recognized concern, and understanding the drivers of spatial and temporal variation in its magnitude and frequency has become a primary target for scientists, and management practitioners alike. As part of my current postdoctoral research, I work on a project entitled “Comprehensive Human -Wildlife Conflict (HWC) management strategy in select districts / landscapes of Uttarakhand”, or the HWC-Component which was carried out by the Wildlife Institute of India (WII), Dehradun, which is part of the much larger “SECURE” Himalaya project (“Securing Livelihoods, Conservation, Sustainable use and Restoration of High Range Himalayan Ecosystems”), is implemented in four states of the Indian Himalayan Region (IHR) namely, Jammu & Kashmir, Himachal Pradesh, Uttarakhand and Sikkim. With financial support from the GEF (Global Environment Funds), the project is an integrated approach of MoEF&CC and United Nations Development Programme (UNDP) towards conservation of high-altitude biodiversity and reducing dependency of local communities on natural ecosystems and aims to support the local communities to effectively promote sustainable land and forest management in alpine pastures and forests in high range Indian Himalayan ecosystems that secure sustainable livelihoods and ensures conservation of globally significant biodiversity and threatened species. The project facilitates a paradigm shift from the current approach of conservation to demonstrate a new approach of landscape-based conservation. This is a participatory approach, which focuses on working with various sectors and partners in areas within and outside protected areas, to effectively reduce
threats to biodiversity of local, national and global significance.

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A comparison of elevational alpha diversity profiles between hawkmoths and birds, at multiple taxonomic scales and spatial extents

Diversity patterns along elevational gradients have been documented for nearly all major groups of organisms. Separating the “universal” determinants of elevational diversity patterns from the idiosyncrasies of each taxon and region has been the major focus of this field during the last decade. Global variation in the diversity of elevational patterns and processes has played a pivotal role in highlighting the importance of spatial and taxonomic scale in diversity analysis. Ecologists have recognised the scale-dependency of biodiversity since a long time, however explicit investigations into the consequences of this dependence, and its pervasiveness in ecological literature, were not addressed until recently. In this study, we present a comparative cross-scale investigation of local elevational diversity profiles for hawkmoths and birds, across varying spatial and taxonomic scales. The two taxa are sampled simultaneously, along the same identical transect spanning 2600 m in elevation, in the eastern Himalayan ranges of northeast India – a global biodiversity hotspot. The standardized and concurrent sampling is expected to minimize the confounding influence of multiple predictors, that vary in time (e.g. biogeographic history) and space (e.g. regional area across different elevational bands) across mountain systems, and further reduce the complexity associated with cross-region comparisons. Our primary objective is to investigate how a local elevational diversity pattern for hawkmoths and birds changes across varying (i) vertical extent (with and without inclusion of the lowest elevations), and (ii) taxonomic scale (e.g. orders, families and genera for birds; subfamilies for hawkmoths). We further assess the consequences of a variation in pattern across multiple scales, for the relative predictive strength of five predictors that have shown maximum correlation for the two taxa previously. Using structural equation modeling, we test the multiple competing hypotheses and discuss the difference observed across varying scales. While our primary objective is to investigate the variation in patterns and processes across scale for any given taxa, we also present a comparison of patterns across the two disparate organismal groups.

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PUBLICATIONS

  1. Mungee, M. and Athreya, R.*, 2020a. Rapid photogrammetry of morphological traits of free ranging moths. Ecological Entomology, https://doi.org/10.1111/een.12907

  2. Sathyakumar, S.*, Mungee, M., Pal, R., 2020. Biogeography of the Mountain Ranges of South Asia. In: Goldstein, M.I., DellaSala, D.A. (Eds.), Encyclopedia of the World's Biomes, vol. 1. Elsevier, pp. 543–554. ISBN: 9780128160961

  3. Mungee, M.* and Athreya, R., 2020b. Functional randomness despite high taxonomic turnover across an elevational gradient in a global biodiversity hotspot: A case study of hawkmoths and birds. BioRxiv, p.867770. (Under review)

  4. Mungee, M.* and Athreya, R., 2021a. Intraspecific trait variability and community assembly in hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas, India. Ecology and Evolution, 11(6), pp.2471-2487.

  5. Mungee M.*, Pandit, R. & Athreya R., 2021b, Taxonomic scale dependency of Bergmann’s patterns: A cross-scale comparison of hawkmoths and birds along a tropical elevational gradient, Journal of Tropical Ecology (accepted for publication)

  6. Mungee M.*, Pandit, R. & Athreya R., 2021c, A comparison of elevational alpha diversity profiles between hawkmoths and birds, at multiple taxonomic scales and spatial extents (Under preparation)

  7. Sathyakumar, S.*, Rawat, G.S., Bhatnagar Y.V., Maheshwari, A., Mungee, M., Bhartwal, D., Rao, Y., Ganguly, S., 2020,  UNDP-GEF Funded report on 'Comprehensive Human-Wildlife Conflict (HWC) Management Strategy in select Districts / Landscapes of Uttarakhand' under the SECURE Himalaya Project, Wildlife Institue of India, pp 1- 116  

  8. Sathyakumar, S.*, Rawat, G.S., Bhatnagar Y.V., Maheshwari, A., Mungee, M., Bhartwal, D., Rao, Y., Ganguly, S., 2020,  UNDP-GEF Funded report on 'Landscape Management Strategy and Action Plan for the Darma-Byans-Chaudhans and Gangotri-Govind landscapes of Uttarakhand' under the SECURE Himalaya Project, Wildlife Institue of India, pp 1- 167