Latest Events

Topic: 
The contribution of citizen science to biodiversity research in the UK
Speaker: 
Dr. David Roy, Centre for Ecology and Hydrology, UK
Date & Time: 
13 Jun 2018 - 11:00am
Event Type: 
Invited Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

TBA

Topic: 
A mathematical model of the Warburg Effect: Effects of cell size, shape and substrate availability on growth and metabolism in bacteria
Speaker: 
Anshuman Swain, University of Maryland
Date & Time: 
8 Jun 2018 - 3:00pm
Event Type: 
Invited Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Even in the presence of ample oxygen, many organisms simultaneously utilize both the efficient aerobic pathway and the inefficient fermentation pathway for respiration. This behavior is called the Warburg effect (also termed overflow metabolism in bacteria) and has remained an enigmatic and poorly understood phenomenon despite years of experimental work. Here, we focus on bacterial cells and build a model of three trade offs involved in utilization of aerobic and anaerobic respiration pathways (rate versus yield, surface area versus volume, and fast versus slow biomass production) to explain the observed behavior in cellular systems. The constructed model also predicts changes in the relative usage of both pathways in terms of size and shape constraints of the bacterial cell, and identifies how substrate availability and environment influences growth rate. Furthermore, we use the model to explain certain complex phenomena in modern- and paleo-ecosystems like methane and carbon dioxide emissions in the wetland ecosystem and in the end-Permian extinction event, via the concept of overflow metabolism. These predictions from the model are not only testable in lab/field but also hold important implications for understanding such behaviors in ecological systems as well as for making relevant policies in conservation and climate change.

Topic: 
Animal Social Networks: Gaining Insights into Social Styles, Disease Risk, and Wildlife Conservation
Speaker: 
K. N. Balasubramaniam, Department of Population Health and Reproduction, School of Veterinary Medicine, University of California at Davis
Date & Time: 
5 Jun 2018 - 10:00am
Event Type: 
Class
Venue: 
CES Class Room
Coffee/Tea: 
Before the talk
Abstract:

In group-living animals, competitive and cooperative social interactions among individuals give rise to social structure. Understanding variation in social structure is fundamentally important since it captures the strategies adopted by individuals to maximize the benefits of group-living (e.g. cooperative predator defense, offspring care) while minimizing its costs (e.g. disease risk, resource competition). During the last
decade, social network analysis has revolutionized the way we understand social structure. Specifically, network approaches have improved on traditional methods by quantitatively describing higher-order aspects of social life from both direct interactions and secondary pathways that connect group members. Here I illustrate three major avenues in which social networks have been instrumental in animal behavioral and
socioecological research. First, I describe how studies of nonhuman primate social networks have added a fresh perspective to our current understanding of the evolutionary origins of their social styles. Specifically, comparative studies of macaque (Macaca sp.) dominance hierarchies and affiliative grooming social networks have shown that aspects of social style that were thought to be structurally linked in fact constitute a mosaic of unlinked, independently evolving traits. Second, I review how networks can be used to understand links between social life and health outcomes, specifically in epidemiological models that link heterogeneity in social contact patterns with disease risk. The majority of these studies have revealed that central or well-connected individuals maybe potential “superspreaders” of infectious agents, because they show higher parasite prevalence or diversity. Further, comparisons of social networks with microbial phylogenies and transmission networks maybe key in modeling potential transmission pathways of epidemics through animal populations. Third, I review a recent line of research that recognizes the utility of social network analysis in wildlife conservation and population management. Specifically, temporal changes in the structure or fragmentation of social networks of wild animal populations may indicate the impact of human perturbation of the natural environment on the destabilization (or resilience) of wildlife populations. Such structural changes to social networks may in turn impact animal health, reproductive success, and survival. I end by briefly elaborating on how bipartite and multimodal networks constitute a key future direction in our assessments of animal socioecological and human-wildlife systems. They add a level of complexity to social networks and by distinguishing two or more components within a system. I also highlight some caveats and potential pitfalls of network approaches that ought to be considered before their implementation in behavioral and ecological research.

Topic: 
Social Life and Health: Factors Influencing Macaque Social Structure and Infectious Disease Risk
Speaker: 
K. N. Balasubramaniam, Department of Population Health and Reproduction, School of Veterinary Medicine, University of California at Davis
Date & Time: 
4 Jun 2018 - 10:30am
Event Type: 
Invited Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Understanding the origins of animal social life and its impact on health outcomes presents a major challenge for researchers. This is because social diversity is influenced by multiple evolutionary and ecological factors and has complex impacts on health. My research addresses this challenge by examining the influence of both intrinsic characteristics (e.g. phylogenetic history) and extrinsic socioecological factors (e.g. resource competition, human impact) on animal social life and health. Its broader impact lies in the conservation and management of both problematic and endangered wildlife populations. To-date, my work has focused on captive and free-living groups of nonhuman primates, particularly macaques (Macaca sp.). In addition to displaying diverse social structures, macaques also share close physiology, evolutionary histories, and ecological space with humans, making them an ideal model genus. First I present aspects of my past research, which focused on understanding the evolutionary origins of macaque social structure. Specifically, I found that some aspects of macaque social structure related to their dominance hierarchies show strong phylogenetic signals, while others related to the structure of affiliative grooming social networks, show only
moderate-to-weak signals. Further, my findings on free-ranging rhesus macaques (M. mulatta) and wild Tibetan macaques (M. thibetana) found that socioecological factors may influence variation in grooming exchange behaviors. My current research deals with how macaque social structure influences health outcomes, specifically infectious disease risk. I examine how broader social contexts and/or microbe-specific characteristics may determine whether/when macaques’ social networks may socially buffer animals against pathogenic infection, facilitate contact-mediated pathogen transmission, or present ‘social-bottlenecks’ that prevent the group-wide spread of infectious agents. I’m also currently conducting long-term assessments of human-macaque interfaces as dynamic, Coupled-Systems. This work is examining how anthropogenic factors may influence the social structure of free-living macaque populations in Asia by inducing environmental stressors or by constraining the time available for animals to engage in social interactions.
As part of my three-track future research plan, I will first build on my research on captive macaques to unravel the co-evolutionary, paradoxical links between primate socioecology and disease risk. I also aim to capitalize on the on-going coupled systems research to test conflicting hypotheses (evolutionary versus acquired) related to the sharing of gut microbiota at human-macaque interfaces. Finally, I look forward to establishing the Coupled-Systems approach as a unifying framework to assess the drivers and feedback effects of interactions and conflict between humans and other wildlife groups and populations. I end by encouraging the conceptualization of social structure as a set of social reaction-norms, i.e. where groups/species may respond similarly to variation in ecological factors, but have inherently different ranges of responses to the same conditions.

Topic: 
Biogeography and comparative phylogeography of freshwater snails of India
Speaker: 
Maitreya Sil, IISc
Date & Time: 
20 Jun 2018 - 3:00pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
After the talk
Abstract:

One of the fundamental questions in biogeography is how paleoclimate and paleogeology shape biotic distribution. However, to understand these processes at different time frames, one needs to look at patterns at both intra and inter-species and levels. Freshwater gastropods owing to their ecology are particularly susceptible to environmental fluctuations and therefore are an ideal model system to study these processes. In my first two chapters, I have investigated the origin and evolution of two snail families, Ampullaridae and Viviparidae. Here, I explored the role of tectonic history of India and several paleoclimatic and paleogeological events in shaping their distribution in the Indian subcontinent in a phylogenetic framework. In the third chapter, I have addressed how late Quaternary climatic fluctuations have affected the distribution and demography of two species of Viviparidae snails: Bellamya bengalensis and B. cf. dissimilis, in the subcontinent using phylogenetic and population genetic tools as well as statistical phylogeographic inference. I discuss how these various abiotic factors have affected the distribution of these snail species at different geological time frames and levels of biological organization.

Topic: 
Influence of landscape composition on butterfly population: A behavioural ecological approach
Speaker: 
Ravi Jambhekar, IISc
Date & Time: 
31 May 2018 - 3:00pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
After the talk
Abstract:

A central question in ecology involves understanding the processes underlying patterns in population abundance and the distribution of species at small and large spatial scales. The distribution of individuals of a species across a landscape may be influenced by both local factors, such as resource abundance; and by landscape-level factors, such as the size of habitat patches, connectivity between patches and the permeability of the matrix surrounding habitat patches, all of which influence the colonisation and extinction of local populations and the movement of individuals between populations. How these local and landscape-level factors affect the distribution of a species may vary widely between species, because the response of species to these ecological conditions may depend on species-specific traits, such as body size, behaviour and other functional traits. There is relatively little known about how ecological factors interact with functional traits to influence species distribution in a landscape. I investigated the ecological processes at local and landscape levels influencing population densities by taking a behavioural ecological approach and using butterflies as a model system. I also examined how functional traits affect the relationships between ecological factors and species distribution in a landscape. I first examined how resource dispersion, an important ecological condition affecting butterfly populations, affects key behavioural decisions of butterflies. Studying the behaviour of individuals allows us to link population patterns with underlying ecological and evolutionary processes. I describe how butterflies appear to respond to resource dispersion at both small and large spatial scales and to balance acquiring two distinct types of resources when making foraging and habitat-use decisions. I then examined how landscape-level factors, specifically patch size, connectivity and matrix permeability, affect butterfly populations. I tested whether the apparent response of a species to landscape-level factors was affected by species-specific traits, specifically whether it was a habitat generalist or specialist and how permeable the matrix was to it. Finally, I test and describe how diverse functional traits, including morphological, life-history and behavioural traits, affect relationships between landscape composition and population density patterns of butterflies.

Topic: 
Large Herbivore Dung Decomposition: Insights into organic matter and nutrient dynamics in a tropical forest of southern India
Speaker: 
Ekta Chaudhary, IISc
Date & Time: 
3 Jul 2018 - 2:00pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
After the talk
Abstract:

Large herbivores can selectively feed on nutrient rich resources, resulting in regular deposition of high quality organic matter in the form of dung. In tropical forests such as in southern India it is estimated that large herbivores contribute to several hundred kilograms of dung on a daily basis. Decomposition of this dung and its implications on nutrient cycling in an ecosystem, has recently become a subject of interest to ecologists across the globe. However, most of our understanding on dung decomposition and its implication come from agroecosystem studies conducted on cattle dung. The identity of primary insect communities involved in dung comminution and feeding is well documented, but little is known of the processes and their impact on nutrient and carbon dynamics. We had set out with three primary objectives: 1) To identify the dung feeding insect communities, 2) Quantify the changes in dung composition during the decomposition and 3) Identify the impact of dung beetles on nutrient leachate and organic matter inclusion into the soil. To address these objectives, we carried out in-situ and ex-situ experiments in a tropical forest of southern India, the Mudumalai national park, for three large herbivores- elephant, gaur and cheetal, that constitute the major herbivore biomass of the region. We found two insect communities, termites and dung beetles, actively feeding on dung. However, their community composition, diversity and abundance varied with the age of the dung and the seasons. During the course of the experiments, we found that crude carbon is readily reduced but remains unaffected by seasons and across the three forest types (dry thorn, dry deciduous and moist deciduous) of the study area. We also analysed the recalcitrant component of carbon, lignin and easy to degrade, monosaccharides to understand what forms of carbon may be reduced in this process. Monosaccharides remained unaffected during the experiments, but lignin was reduced across habitats and seasons. The final experiment looking at the leachates from dung into the soil showed considerable difference between the herbivore dungs, but no effect of the dung beetle activity compared to the controls. To our knowledge, this study is among the first to use a comprehensive approach to study dung decomposition and its impact on nutrient and organic matter dynamics. It also helps in building a basic understanding of the direct role of large herbivores in cycling of nutrients.

Topic: 
Climate-growth relationships of west Himalayan Fir (Abies pindrow) along an altitudinal gradient in northwestern Himalaya
Speaker: 
Rayees Malik, IISc
Date & Time: 
2 Jul 2018 - 2:30pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
After the talk
Abstract:

Climate change has a significant impact on forests and people dependent on them. High mountains around the globe are some of the most vulnerable systems and of great concern for conservation. The Himalayan mountains are experiencing a higher warming than average global warming, which can significantly impact their biodiversity, vegetation distribution and ecosystem structure. The plants growing in the Himalaya will have to adapt accordingly to survive the changing climate. Variations in climate impact tree growth and significantly influence cambial phenology and wood formation. There is a need to precisely document cambial phenology and wood formation in Himalayan trees to better understand climate-growth relationships and their response to future climate change. In this thesis, the dynamics of cambial phenology along an altitudinal range of the west Himalayan fir, Abies pindrow, was studied. Various stages of cambial phenology, duration and rate of wood formation were assessed from anatomical observations of xylem during the growing season from samples taken from three sites at various altitudes (2392-2965 m a.s.l.) over two years. In the 2nd part, climate-growth relationship along the altitudinal gradient using tree rings was investigated between monthly climate and radial tree growth from 1901-2016. The relationship was also studied using seasonal climate data. The temporal stability of this relationship was also studied to understand the impact of recent climate warming on climate-growth relationship. Finally, site chronologies from climatically sensitive trees were built and their response to regional climate was used for reconstruction purposes. The lower altitudinal site trees showed a good response to early growing season precipitation which was used to reconstruct the spring precipitation of Srinagar for last 200 years. Furthermore, growth responses to daily climate data was used to reconstruct the regional climate at a more finer scale. These findings give new insights into the dynamics of cambial phenology and climate-growth relationships and help in better understanding of potential impacts of climate change on tree growth and forest productivity in Himalayan forests.

Topic: 
The origin of life
Speaker: 
Dr. Samay Pande, ETH Zurich, Zurich, Switzerland
Date & Time: 
3 Jul 2018 - 10:30am
Event Type: 
Invited Seminar
Venue: 
CES Class Room
Abstract:

Life on earth can be extremely complex where different parts function together for the survival and reproductive success of the organism as a whole. Evolution of complexity required several small steps known as major transitions. Among such transitions during the evolution of life, certain events are unique (for example; evolution of genetic code), whereas other transitions might have happened multiple times through the history of evolution of life on earth.

There are obvious difficulties associated with discussing rare events such as evolution of genetic code, evolution of eukaryotic cells, and origin of life. However, we have an advantage while making prediction about how life must have originated on earth. This is because our predictions about the origin of life should adhere to the well-accepted laws of chemistry and mechanisms of natural selection. Since, most living organisms contain self-sustaining chemical system- dependent on external source of energy, and properties such as heredity, reproduction and differential reproduction. It is predicted that early life on earth must have exhibited these properties. Furthermore, growing body of evidence suggests that RNA molecules must have served as a replicating molecule responsible for heredity and also for coding metabolism inside primitive cells.

For evolution of metabolism and maintenance of RNA, both template and replicase activity is needed to be enclosed in some form of a physical compartment. Additionally, compartmentalization will lead to concentration of molecules, provide protection from environmental conditions, and allow evolution of cooperative network between replicating molecules. Given the significance of compartmentalization, I will discuss how simple lipid vesicles – protocells - might have functioned as an early barrier between extracellular and intracellular environment. However, without complex machinery used by modern cells for growth and division, simple vesicle-like early cells must have exhibited properties of spontaneous duplication and growth. I will discuss how the mechanism of spontaneous duplication and growth might have resulted in competition between vesicles. Overall, in this seminar, we will review properties of the early cell-like structure that until recently was a complete black box, and how the information gained from recent empirical evidence has helped us better understand the early evolution of life on earth.

Topic: 
Bacterial growth and survival is a socially multifaceted process
Speaker: 
Dr. Samay Pande, ETH Zurich, Zurich, Switzerland.
Date & Time: 
2 Jul 2018 - 10:30am
Event Type: 
Invited Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Cooperation has played a grand role in the evolution of diversity and complexity of life on our planet. Some of the most spectacular and most visible examples of cooperation are reproductive cooperation among social insects such as honeybees, division of labor in the colony of leaf-cutting ants and among cells of multicellular organisms. In all of these examples individuals within a group are highly related. Such high relatedness might be favored because it prevents conflict that might disrupt the functioning of the cooperative group. However, interactome within and between social groups of organisms that have retained reproductive autonomy and exhibit within group variations remain unknown.
Using natural social groups of Myxococcus xanthus that are internally diverse, we show that within-social-group diversity in the natural populations has positive effects on overall group productivity. This positive effect of mixing was only limited to interactions between isolates from the same social group and might be the result of overwhelmingly common bidirectional positive interaction effects between pairs of isolates. Strikingly though, mixing effects between isolates derived from different fruiting body were strongly negative. Our findings therefore provide an intuitive ecological explanation for the ease, with which possible shift in the level of selection might occur in the populations that coexist together over an evolutionary timescale.
Next, using two natural isolates of M. xanthus sampled from the same fruiting body on soil, we demonstrate that M. xanthus spore germination is a cooperative process involving production of public good molecule. Moreover, inability to germinate defect exhibited by one strain under saline stress in pure culture is socially complemented by the presence of another strain that is fully proficient at germination. Complementation confers a cheating advantage to the defective strain and is mediated by secretion of glycine betaine, an osmo-protectant utilized in all domains of life that functions as a public-good molecule necessary for germination in salty environments. These findings suggest that spore germination may be a socially multi-faceted process in other microbes as well.
Bacteria use dormancy as a bet-hedging strategy to overcome unfavourable environmental conditions. The dormant individuals such as spores or persister-cells with low metabolic activity can determine community dynamics in future generations. Although importance of social interactions has been documented among actively growing microbes, role of social interactions between individuals in diverse communities during transition to, and away from dormancy, remained unclear. Our results demonstrate importance of synergistic interactions within natural social groups of M. xanthus during conversion of actively growing cells to dormant spores and also during resuscitation of spores to actively growing cells.

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