The golden langur is one of the most range restricted colobine monkey, confined to the region between Sunkosh and Manas rivers in Bhutan and adjoining Assam (India). It is closely related to the widely distributed capped langur which is distributed from Eastern Bhutan, Northeast India, parts of Northern Bangladesh to Southern China, and Northwestern Myanmar. Golden langur has been divided into two subspecies whereas capped langurs into four. However, the subspecies status of golden langur is still being debated. Previous studies have hypothesized that an isolated population of capped langurs might have speciated into golden langurs due to geographical barriers like rivers and mountains. This would represent a classic case of budding speciation; wherein peripheral isolates of widely distributed species evolve into a distinct lineage. Furthermore, the presence of intermediate forms between golden langurs and capped langurs found in an overlap zone in central Bhutan hints at a possible hybridization between these two species. Alternately, these intermediate forms might represent clinal variation between golden and capped langurs (intergradation). Given this background, for my thesis research, I aim to investigate the origin and evolutionary history of golden langurs vis-a-vis capped langurs by using multiple nuclear and mitochondrial markers. Genetic data will be used to address three specific questions. 1) Does genetic data support splitting of golden langur into two subspecies? 2) Is there genetic evidence for budding speciation? 3) Are the intermediate forms a case of hybridization or does it represent intergradation?

India is considered the world's snakebite capital, where over 58,000 snakebite fatalities are registered annually. Most bites are primarily attributed to four snake species: the spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell's viper (Daboia russelii), and saw-scaled viper (Echis carinatus) that are collectively termed as the 'big four'. Recent research has unravelled a significant variation in snake venom composition and toxicity at inter- and intraspecific levels, resulting in an alarming ineffectiveness of antivenoms - the only available treatment for snakebites. However, the extent of venom variability, which often results from differing ecologies, evolutionary histories, and/or environmental conditions, remains largely uninvestigated in the majority of clinically important snakes. For example, the influence of varying ecology and environment on the venom of the common krait (B. caeruleus), the snake species with a near-pan-India distribution responsible for the second-highest number of snakebite-related deaths in India, has not been investigated to date. To address this knowledge gap, my PhD research focused on assessing the biogeographic venom variation in this species across India. Furthermore, I have evaluated the repercussion of this geographic venom variation on the preclinical efficacy of commercially available Indian antivenoms.

Similarly, the extent of intrapopulation venom variation, especially at finer geographic scales, remains poorly understood. I had, therefore, employed an interdisciplinary approach involving venom proteomics, biochemistry, and pharmacology, to assess venom variation in monocled cobra (N. kaouthia) sampled across a small spatial scale (<50 km). Finally, I have evaluated in vitro and in vivo venom binding and neutralisation capabilities of conventional antivenoms in countering toxicities inflicted by various individuals in this population.

While conventional antivenoms have saved thousands of lives, they suffer from numerous flaws, such as ineffectiveness against necrotic effects, reduced dose-effectiveness that often leads to many secondary reactions, including fatal anaphylaxis, and unavailability in many primary health centres. Secondary metabolites of plants have been shown to effectively neutralise snakebite pathologies, especially the local effects such as haemorrhage and necrosis. Therefore, I have assessed the antivenomic potential of medicinal plants, such as avaram (Cassia auriculata), utilised in traditional medicine. The neutralising potency of Cassia auriculata flower extracts against medically important snake venoms has been evaluated using in vitro experiments. Finally, I identify the active components in these plant extracts and will explore their potential role in treating snakebites in India.

In terrestrial environments, forests are dominated by plants which structure the landscape, offering habitat to thousands of species. Forests exist also in the ocean, and they are dominated by sessile benthic organisms (such as sponges, corals, bryozoans) which form three-dimensional structures providing architectural complexity and sheltering, feeding, protection for diverse associated biota. These communities are similar to terrestrial forests, with the main difference that they are dominated by animals instead of plants. The term marine animal forest (MAF) has been proposed to define those animals dominated three dimensional communities which are present all over the world, from polar to tropical regions and from shallow to deep. In terrestrial ecosystems, forest are characterized by high associate biodiversity and stable climatic conditions (microclimate). The presence of a microclimate, the role played by forest three dimensionality in supporting biodiversity and have been hypothesized also for MAFs. Nonetheless, their capability to support those ecological functions and therefore to deliver the above cited ecosystem services is still undefined. Even more unknown, because never quantified and demonstrated yet, is the existence of a relationship between forest density and structure and such capability. The seminar will present the current knowledge on the functional ecology of these habitats and their resilience capacity.

To halt the loss of biodiversity in accordance with the Convention on Biodiversity (CBD) and the Aichi objectives, France aims to classify 10% of its territory as a strong protection zone by 2030. These new conservation zones will have to fit into the puzzle of marine spatial planning and respond in space and time to ecological, economic, social and be resilient to climatic issues. Resilience in marine population is tightly linked to population connectivity. Population connectivity enables genetic mixing and accelerates the recovery of a population after a demographic accident. On land, this is achieved through the "green and blue network", by creating corridors of green spaces, removing dams on rivers, and building animal bridges over freeways to link natural areas together. At sea, we call it the "marine blue grid", but it's invisible to us humans. It cannot be developed, but follows the currents of the sea, a network of underwater routes that the vast majority of marine species must use. How can we imagine it? This seminar will present the current state of knowledge and research on the marine blue network in the Gulf of Lion (French Mediterranean coast) as a template methodology for the on-going work on Andaman islands.

Variability in phenotypic traits such as body size or shape is typically lower in animal groups than within their populations ̶̶ indicating that such groups are phenotypically assorted. Active group choice is one of the mechanisms by which such phenotypic assortment can be achieved. Several species of reef fish form mixed-species groups or “fish flocks” where two or more species associate for foraging or anti-predatory benefits. For attendant groups of reef fish which form primarily for foraging benefits – competition for resources between shoal members may result in phenotypically variable groups. Frequency dependent differential predation (predators preferring phenotypically odd individuals) and activity matching may drive phenotypically assorted grouping which is seen in shoaling groups of reef fish that form primarily for anti-predator benefits.

Variability in phenotypic traits such as body size or shape is typically lower in animal groups than within their populations ̶̶ indicating that such groups are phenotypically assorted. Active group choice is one of the mechanisms by which such phenotypic assortment can be achieved. Several species of reef fish form mixed-species groups or “fish flocks” where two or more species associate for foraging or anti-predatory benefits. For attendant groups of reef fish which form primarily for foraging benefits – competition for resources between shoal members may result in phenotypically variable groups. Frequency dependent differential predation (predators preferring phenotypically odd individuals) and activity matching may drive phenotypically assorted grouping which is seen in shoaling groups of reef fish that form primarily for anti-predator benefits.

Variability in phenotypic traits such as body size or shape is typically lower in animal groups than within their populations ̶̶ indicating that such groups are phenotypically assorted. Active group choice is one of the mechanisms by which such phenotypic assortment can be achieved. Several species of reef fish form mixed-species groups or “fish flocks” where two or more species associate for foraging or anti-predatory benefits. For attendant groups of reef fish which form primarily for foraging benefits – competition for resources between shoal members may result in phenotypically variable groups. Frequency dependent differential predation (predators preferring phenotypically odd individuals) and activity matching may drive phenotypically assorted grouping which is seen in shoaling groups of reef fish that form primarily for anti-predator benefits. We investigate the similarities in phenotypic traits (viz. body size, body shape, body markings and colours) in the association patterns for attendant and shoaling groups of reef fish in the Arabian and Andaman Seas. We find that shoaling groups in both the Lakshadweep archipelago and the Andaman Islands undergo phenotypic assortment (showing low phenotypic variability), possibly to overcome the oddity effect thus minimizing their predation risk. We also explore the environmental factors that drive the formation of shoaling groups of herbivorous reef fish by estimating resource abundance and relative predator abundance across a fishing gradient (within and outside Marine Protected Areas) in the Andaman Sea.

It is often proposed that most organisms on this planet are parasites. Their ubiquity, species richness and ecological and economic importance render them a fruitful model to study the processes underlying biodiversity, especially in aquatic environments with their high phylogenetic diversity of potential hosts. Therefore, our team studies the taxonomy, genomics, morphology and ecology of parasitic flatworms (and other parasites) of fishes and other aquatic animals. We focus on study systems with relevance to general evolutionary phenomena (e.g. adaptive radiation) or conservation (e.g. alien invasive species, fisheries, protected wetlands).

Thanks to strong ties with various capacity development initiatives funded by Belgian development cooperation, the team invests consistently in institutional partnerships in the Global South (e.g. co-tutelle PhDs), currently mainly in Africa. This has also led to a research line on biodiversity policy, covering aspects such as biodiversity indicators, stakeholder involvement in natural resource management, assessment of anthropogenic impacts on aquatic ecosystems, and perceptions of biodiversity. In an effort to couple the parasitological and policy-relevant research themes, we are active in the field of One Health, and in IUCN Red Listing.

This presentation will introduce the team, and showcase a selection of representative projects and outputs with emphasis on recent work. It is hoped this will only be the start of discussions on potential common interests and future collaborations

Studying human-nature interactions requires an inter- and trans-disciplinary perspective, and highlights the need for a systematic and structured integration of social science approaches in conservation science and action.

This presentation will showcase highlights from recent projects I led at the Open University of the Netherlands, at Hasselt University and at the VUB & ULB universities of Brussels, Belgium. As an Assistant Professor in Environmental Governance, and as a Visiting Professor in Biology, I have a specific interest in collaborative environmental governance, social-ecological systems management, biodiversity conservation effectiveness, ecosystem services, the plural valuation of nature and human-wildlife conflicts.

Together with my colleagues, I have worked on a range of international research projects, often focusing on mangroves as model systems. Although mangroves are increasingly recognized for the many benefits they provide to humans, they are under threat due to heavy development pressures along tropical coastlines. Understanding and integrating the perspectives of a range of mangrove management stakeholders is key for sustainable mangrove conservation – and this requires the development and application of a range of –social- science methods. Next to mangroves and other coastal systems, our research also focuses on the effectiveness of protected areas (PAs) and on conservation conflict mapping and mitigation.

I will also zoom in on two international Master programmes I’m teaching in: the Tropimundo Master on Tropical Ecosystems and Biodiversity and the Master in Marine & Lacustrine Science & Management (Oceans & Lakes) and briefly introduce our field school experience in mangrove settings. The whole idea is to explore common interests and to reflect on collaboration opportunities.

Sex-biased predation occurs when one sex of a prey species is consumed more than the other, irrespective of their relative availability (sex-ratio). Some of the potential factors leading to sex-biased predation are sex differences in morphology and/or behaviour of prey species. In the context of mate-finding, we often see sex-specific behavioural strategies, such as signalling and searching. The relative risk of predation on the two sexes during mate-finding depends on who signals, who searches, the risks associated with these behaviours, and the degree of involvement in these activities. Prey wing remains found in the roosts of a bat predator, Megaderma spasma, reveal interesting patterns for two katydid genera, Mecopoda and Onomarchus. Mecopoda sp. wing remains are male-biased in the breeding season and female-biased in the non-breeding season, while Onomarchus uninotatus wing remains are female-biased year-round. These two katydids differ in their mate-finding strategies: in Mecopoda sp., which are found close to the ground, males signal acoustically and females search silently to locate them. Onomarchus uninotatus is an arboreal katydid, that uses an acoustic-vibratory multimodal duet for mate-finding within trees, with both sexes signalling and searching to find mates.

To explore the factors driving the sex-biased predation by M. spasma on Mecopoda sp., I used a combination of field observations and enclosure experiments with wild-caught live animals. The males and females of Mecopoda sp. were compared with respect to (i) their availability, i.e., natural sex-ratio across the seasons, (ii) the predation risks associated with different behaviours, and (iii) the prevalence of their risky behaviours in the wild. The results show that the relative availability of the sexes does not explain the male-biased predation on Mecopoda in the breeding season; whereas in the non-breeding season, very few males are available, which could lead to the female-biased predation. Males perform high-risk mate-finding behaviours, such as calling and flight, with a high prevalence in the wild. Although flight is equally risky for both sexes, females rarely fly.

To understand bat predation risk on male and female O. uninotatus and its possible role as a selection pressure driving the evolution of multimodal duetting, outdoor enclosure experiments were performed with live bats and katydids. Bat predation risks were compared (i) between the signalling and searching strategies of each sex, and (ii) between male and female signalling. The findings indicate that bat predation risk fails to explain the evolution of vibrational signalling in O. uninotatus females, as searching by walking is as safe as signalling, leading to an overall low predation risk on females within a tree. However, their duetting behaviour lowers the risk on males, who can shift from high-risk signalling to low-risk searching by walking, once females start signalling.

Finally, I focused on bat predation risk of searching behaviour in O. uninotatus, which potentially takes flights across trees. Comparisons were made between males and females for (i) bat predation risk of flight using enclosure experiments and (ii) across-tree movement patterns using radio-telemetry. I found that flight is equally risky for both sexes, but females move across trees 1.6 times more often and 1.8 times greater distances, which could make them more vulnerable to predation, offering a possible explanation for the female-biased prey remains found in M. spasma roosts.

Overall, this thesis provides a comprehensive examination of the predation risks associated with signalling and searching behaviours of katydids. The interplay between sex-specific behaviours and ecological factors can explain sex-biased predation patterns.

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The terrestrial carbon (C) cycle involves fluxes between multiple pools that determine ecosystem functions and regulate global climate. These fluxes and pools are influenced by changes in abiotic (temperature, precipitation etc.) and biotic (animals, microbes, etc.) factors. In this thesis, I address three questions on how these abiotic and biotic drivers influence the size and stability of these fluxes and pools. In the first chapter, I investigate how covariation between decadal trends (2001-2019) in temperature and precipitation influence the two opposing C-fluxes in the soil-C pool – (1) C-influx through primary production (NPP), and (2) C-efflux through soil heterotrophic respiration (Rh). I estimate how any imbalance between these opposing fluxes affects the vulnerability of soil-C across the globe. I find that changes in C-influx may not compensate for rising C-efflux, under wetter and warmer conditions. Soil-C loss can occur in both tropics and at high latitudes, and precipitation emerged as the key determinant of soil-C vulnerability in a warmer world. This implies that hotspots for soil-C loss/gain can shift in the coming decades to make the soil-C pool vulnerable to climate change despite widespread increase in NPP across the world. In the second chapter, I explored the influence of climate on long-term correlations in vegetation fluctuations (i.e., persistence, measured by the Hurst exponent from time-series data). I found evidence for stronger persistence in warm and dry regions of the world, and there were non-linear relationships between persistence and two key climate variables (i.e., temperature and precipitation). While average temperature and precipitation together explained nearly three-fourths of the spatial variation in vegetation persistence, they had limited ability to explain the observed temporal changes in persistence. We find evidence for change in vegetation persistence across the globe driven by background change in climate. This provides some new insights into the resistance/resilience of vegetation in different ecosystems.  In the third chapter, I investigated how animals – large mammalian herbivores – influence the terrestrial carbon cycle. Their influence on the size of the soil-C pool is well known, but how herbivores control the temporal stability of soil-C has remained largely unknown. I used a long-term field experiment in the Trans-Himalaya (2005-present) to estimate the consequences of herbivore-exclusion on interannual fluctuations in soil-C. I found high interannual variability in soil-C, and herbivores promote temporal stability of soil-C. Grazing by herbivores also mediated the influence of nitrogen on the stability on soil-C. Therefore, conserving large mammalian herbivores in grazing ecosystems can help achieve nature-based climate solutions. Overall, this thesis explores the linkages between three aspects of the terrestrial carbon cycle and climate, and herbivores. It highlights the non-linearities in vegetation-soil-animal interactions which are important for the stability of the terrestrial carbon cycle. 

Parasites and pathogens are ubiquitous in that they affect almost any aspect of life. They influence host populations and entire communities, but can also target specific groups of hosts. A fundamental challenge of infectious disease epidemiology and evolutionary ecology is to identify the factors contributing to the emergence of epidemics and the spread of diseases, and to assess their epidemiological, ecological and evolutionary consequences. An important yet often overlooked factor influencing variation in disease susceptibility and disease spread is the age of the host. Whereas phenomena relating host age to infectious disease biology of humans and other vertebrates are well known, little is known about age effects in invertebrates and they are hardly taken into consideration in studies of host-parasite interactions and evolutionary ecology. This stands in contrast with the role of invertebrates in human well-fare (invertebrates are often vectors for human diseases) as well as their contribution to apiculture and aquaculture, the maintenance of biodiversity and ecosystem functioning. Previously I found that host age at exposure directly affects the interactions between the bacterium Pasteuria ramosa and its water flea host Daphnia magna. Here, I will show that similar age effects are present in single and multi-strain infections by the microsporidian Hamiltosporidium tvaerminnensis, a mixed-mode parasite of D. magna. Using three species of Daphnia (two clones from each host species), and two isolates of the pathogenic yeast Metschnikowia bicuspidata, I will also show the generality and diversity of host age effects. I will further show that clearance of P. ramosa in 30-day-old D. magna can occur at progressed infection phases, a rarely documented phenomenon in invertebrates. Finally, I will show how experimental evolution can be used to test if the parasite can adapt to the host age class it infects predominantly. Ultimately, elucidating the underlying dynamics will improve our understanding of disease ecology and virulence evolution.