With the start of 21st century, climate change has caught attention of the world due to an increase in natural calamities, all of which have been attributed to climate change either directly or indirectly. There lies too much uncertainty in the possible role of soil in climate feedback, which on finer scale is regulated by microbes. With large body of literature available for the effect of climate change on soil carbon and microbes, there is still uncertainty on how soil microbial community is going to behave under projected climate change and change in land-use patterns. This has been further complicated by the heterogeneity of microbial community among ecosystems and different land-use. The proposed study would try to address various pathways and mechanism through which microbes function under different land use scenario and a glance into the possibility of microbes shaping the ecosystem in the wake of future
climate projections.

Over the years, multiple studies have tried to explain the patterns of species richness and distribution along different gradients through various hypotheses, all of which have equal support and criticism from different quarters. A consistent trend however observed across all these studies shows that most of these questions/hypotheses were studied at a narrow taxonomic level ie: for trees, ants or butterflies etc. but not for multi-taxa communities which coexist and share resources in the ecosystem. While many studies show patterns of different single-taxa communities varying or not varying across different gradients, very few explore this at a multi-taxa community level.
In this proposed study, we try to understand patterns of community structure using a multi-taxa approach along different anthropogenic and natural gradients, trying to understand whether a multi-taxa approach can provide better support to either of the many hypotheses trying to explain patterns along gradients and whether predictors of these patterns change from single-taxa to multi-taxa.

How biodiversity is generated and maintained is a fundamental question in
ecology and evolutionary biology, and studying diversification can give us
key insights into this process. In my thesis, I investigate diversification
patterns of lineage, morphology, and climatic niche, to understand the
underlying processes that have shaped these patterns in the historical
context of the Indian subcontinent. *Hemidactylus *geckos - commonly called
‘house geckos’ - are found in a wide range of habitats and climatic zones,
and are an excellent model system to address this question. My findings
indicate that climate has been a key factor shaping the morphological
diversification in this group. Understanding the broad ancestral climatic
niche of *Hemidactylus *also provides an insight into the climatic history
of Peninsular India.

Reproduction is the avenue for gaining direct fitness. But in certain
species some individuals do not reproduce to gain direct fitness, instead
gain indirect fitness by helping relatives to reproduce; the prime
examples for this come from the worker caste of social insects like ants,
bees and wasps. Indirect fitness has been in focus for explaining the
evolution of workers while overlooking the fact that workers can also gain
direct fitness. One of the avenues for gaining direct fitness by workers
is nest foundation and I have studied this phenomenon in a social wasp. I
found that workers prepare in several ways for nest foundation, like
enhancing nutrient reserve and engaging in dominant interactions, even
before leaving their natal nests. While investigating the emergence of
cooperation and division of labour in newly founded nests, I observed how
these affect the productivities of the new nests. Finally I found that it
is ageing and nutrition and not work done towards gaining indirect fitness
that affect workers’ potential of gaining future direct fitness by
independent reproduction.

The Indian subcontinent’s association at different time periods with different landmasses, and the intense climatic changes it has undergone have been evident in the presence of taxa with various biogeographic affiliations on the subcontinent. Studying the diversity and distribution patterns of the Indian biota will also help understand the role of these climatic and ecological processes in speciation. Due to their fossorial nature, blindsnakes have been a largely unexplored group. They are an excellent system to study, to further understand the role of India’s geological history in the present faunal distributions, given the evidence that they have various modes of dispersal, including oceanic dispersal. Some species are also quite widespread, spanning various biomes. This study aims to decipher the various biogeographical affiliations of the four genera of blindsnakes- Indotyphlops, Grypotyphlops, Argyrophis and Gerrhopilus - found in India, using an integrative approach. We also attempt to study the role of the establishment of monsoons and the subsequent aridification in the northern and central regions of India in the speciation processes that have resulted in the current blindsnake diversity. This will also help in understanding the actual diversity of this highly understudied group and resolve their taxonomy in the process.

Ecosystems can exhibit multiple stable states at similar external conditions. Such systems shift from one stable state to another abruptly and discontinuously, when they cross certain threshold parameters. Some examples of such abrupt shifts include coral bleaching, woodland encroachment of grasslands and desertification in semi-arid ecosystems. These transitions in ecosystems are often associated with loss of biodiversity and economic impacts, therefore are important to predict. These systems with multiple stable states, in some cases, can be understood as systems with a free energy functional having multiple local minima. In this theoretical framework, these abrupt transitions in ecosystems are similar to the discontinuous or first order phase transitions. In this thesis, we use the tools from the theory of non-equilibrium phase transitions to understand the mechanisms that cause abrupt transitions in spatially extended ecosystems and the statistical properties of these systems which can help us predict them.

Previous studies have shown that strong local positive feedback among individuals is an important mechanism for systems to have multiple stable states. In our study, we use a lattice based model of vegetation dynamics with basic processes as birth, death and positive feedback among individuals. In its simple version, this model is in the same universality class as directed percolation which is well known to exhibit a continuous phase transition from an active state to an absorbing state. Using master equation expansion for finite sized systems, we construct stochastic differential equations for our discrete state lattice model. We analytically show that systems with finite size can have multiple stable states even in the absence of positive feedbacks. Our numerical simulations of the spatial models confirm these results. Small sized ecological systems, therefore, can undergo discontinuous transition from an active high density state to a bare state where larger ecosystems would have survived.

It is well-known that systems close to a continuous phase transition show slow recovery from the perturbations. This phenomenon is known as critical slowing down. Since ecological systems are finite in extent and rarely in steady states, signatures of critical slowing down are seen before the discontinuous transition as well. In spatial systems, critical slowing down manifests as increase in spatial correlations and spatial variance in the system. Theoretical studies have shown that these signatures can be used as early warning signals for the imminent transitions. These spatial signals have been tested in microbial systems in lab, but few studies show their validity in the field. We hypothesize that above spatial metrics increase when a transition occurs along the gradient of driver in space. We first test this “space-for-time substitution” in a lattice model where driver changes along space. This model shows a transition from one state to another across space. We show that spatial metrics like variance and correlations show an increase even before the transition along the spatial gradient of driver. We, then, test these theoretical predictions in a savanna ecosystem using remotely-sensed and the ground-truthed data. In this ecosystem, grassland and woodland states co-occur at similar rainfall values and the abrupt transition occurs along the rainfall gradient in space. We show that critical slowing down based spatial indicators show theoretically expected trends before the transition. Therefore, we argue that simple spatial metrics can be used to anticipate the abrupt shifts in large-scale ecosystems.

In addition to the early warning signals, it is important to quantitatively estimate the threshold parameter at which the system is likely to shift to another state. To estimate this threshold, we use the property of phase transitions that systems show diverging correlations at the critical point. Therefore, in finite ecosystems showing alternative stable states, we hypothesize that the spatial location at which variance and correlation in the state variable are maximum will be closest to the transition. We used a spatially-explicit model of vegetation dynamics in which the driver value shows a gradient in space. We show that the point at which spatial variance and correlation in vegetation are maximum, is indeed the critical point of the system. We then test this method of finding the critical point in real ecosystems by analysing spatial data from regions of Africa and Australia that exhibit alternative vegetation biomes.

In summary, we employ a model from non-equilibrium statistical physics to understand abrupt transitions in ecological systems. We show that stochasticity caused by finite sized systems can lead to abrupt transitions in spatial ecosystems. We suggest simple spatial metrics to quantify critical points in real ecosystems, offering a significant advance from current studies that only proposed qualitative metrics of proximity to critical points. This thesis presents an elegant example of how principles of nonequilibrium phase transitions can be applied to a complex biological system, by modelling and testing their predictions with data from ecosystems.

SPEEC-UP is a one day conference of student presentations (of 3 minute duration) on Ecology, Evolution and
Conservation.

Its organised by a bunch of folks from ATREE, IISc and NCBS and will be
held at NCBS on 31st August. Here is the link to abstract submission
*(deadline: 20th June).*

http://speecup-blr.weebly.com/

This is a Bangalore centric student event and we expect this will a way to
provide a platform for students and faculty to get together.

There are cash prizes to be won for best presentations!

Conservation of any concerned taxa in altered ecosystems requires an in-depth knowledge of their ecology, including key interdependent facets such as their physiology, behaviour, and habitat. In addition, ecological and anthropogenic perturbations are known to influence the stress status of free-ranging animals. Understanding and assessing the effect of such disturbances on the stress physiology of an animal, therefore, becomes important to gain a holistic picture about the animals’ well-being and to enable better conservation of that species. Hence, this study, being the first detailed assessment, addresses the proximate causation of influence of some of the fundamental ecological and human-induced stressors on the stress status of free-ranging Asian elephants of the Bandipur National Park, the Nagarahole National Park and Hassan district of Karnataka using the non-invasive technique for measuring faecal glucocorticoid metabolites (fGCM). We assessed the influence of intrinsic (age, sex, body condition and lactation) as well as extrinsic factors (seasonality, group size, and human-induced stressors) on the levels of fGCM. Our findings elucidate that the stress-response in a free-ranging elephant is synergistically influenced by various ecological, social and anthropogenic correlates. Such information can help not only in understanding the health status but also in addressing the causes of conservation problems, evaluating the effect of conservation models and formulating the better strategies for the welfare of elephants.

Division of labour plays a very important role in social insects and could
either be reproductive or non-reproductive in nature. The lack of
morphological differences among individuals in primitively eusocial species
lead to greater flexibility in their social roles making them very
interesting model systems to study division of labour. *Ropalidia
cyathiformis*, a primitively eusocial wasp was chosen as the model system
for the study of reproductive and non-reproductive division of labour. One
of the key findings reveals that while dominance behaviour is used as a
mechanism for reproductive division of labour, age is used for
non-reproductive division of labour. We also compared our findings with
what is already known in a related conspecific, *Ropalidia marginata*. Our
findings showed that *R. cyathiformis* maybe a more primitive species
compared to *R. marginata* and provide a glimpse into the origin of
eusocial insects.

More than 50 years after William Hamilton laid the mathematical foundations of kin-selection theory, how cooperation among genetically distinct individuals evolves and is maintained remains one of the most fundamental and fascinating themes of evolutionary research. Of particular importance to this broad theme is the question of how genetic and behavioural diversity within cooperative groups affects group productivity when the latter is a major component of group-member fitness.
Among animals, examples of within-group behavioural diversity that increase total group cooperative productivity abound. However, although research on microbial social evolution has burgeoned in the past two decades, no study has addressed whether cooperative microbes similarly evolve genetic diversity within natural social groups that increases group productivity. Hence, we tested the effects of natural diversity within fruiting bodies of the social bacterium Myxococcus xanthus on total group spore productivity.
This study demonstrates the first examples of chimeric synergy - i.e. positive effects of social chimerism on total group productivity - among conspecific microbes derived from the same natural social group. Moreover, the “social network” within one set of isolates derived from the same fruiting body were also examined in great detail. These analyses show that the chimeric synergy generated by interaction among the distinct members of this fruiting-body group is broadly distributed across genotypes and interactions rather than being (less interestingly) due to social responses by one genotype or a small minority of genotypes.
Interestingly, the chimeric synergy occurs almost exclusively among M. xanthus isolates derived from the same fruiting body. In contrast, forced chimerism among isolates derived from different fruiting bodies generates almost exclusively strongly negative effects on group productivity (chimeric load). Thus, this study not only document naturally evolved, within-group chimeric synergy among microbes, but also the stark dichotomy of such positive within-group interactions to pervasive between-group antagonism, a dichotomy common among cooperative animal species.
These observations therefore suggest both i) that group-level performance during fruiting body development is a major component of fitness for M. xanthus cells and ii) that such selection can operate to maintain within-group diversity of positive effect on group-level performance while purging within-group diversity of negative effect. These results also reveal the absence of selection for divergent lineages across groups to remain socially compatible, thus leading to the quantitative decay of cooperation as a function of spatial distance between isolate origins (and hence as a function of genetic distance between isolates) in experimental between-group chimeras. Thus, the findings from this study are consistent with an intuitively appealing model of selection operating at multiple levels of biological organization in natural populations of bacteria, with selection among higher-level units (in this case fruiting-body-forming groups) being strong enough to differentiate the fundamental social character of within-group versus between-group genetic variation.