Thesis Progress Presentation

Marine systems appear to be more homogenous than terrestrial environments with few apparent barriers to dispersal. Despite this, population structuring and speciation are seen in organisms, even with high dispersal capabilities. For my thesis, I am studying a genus of tropical obligate near-shore dolphins and understand how speciation my have occurred in areas where no barriers are apparent and dispersal seems to have occurred across large distances in spite of conducive habitats. The study aims to resolve the taxonomic identity of the Sousa spp. complex in India, and examine population structure and connectivity for the Indian animals and understand how they place in the global phylogeny for the genus.

Discerning spatial patterns of biodiversity and understanding their proximate and ultimate causes is central to biogeography and macroecology. There has been substantial research on species richness along latitudinal and altitudinal gradients. Both ecological and evolutionary factors may drive diversity along these gradients but their effect on the distribution of species as mediated by species-specific traits has received far less attention.
In my first chapter, I focused on species functional trait variation along a latitudinal gradient. I found the effect of environmental filtering at higher latitudes, suggesting that environmental does play an important role in the distribution of species. Studies involving species environment relationships are important in identification and conservation of biodiverse areas. They are also important in the context of rapid climate change and in answering questions as to whether species will move to track their habitat or adapt to new environmental conditions.
To further understand this, in my second chapter, I modeled the potential distribution of 153 endemic woody species of the Western Ghats. Species distribution models (SDMs) are invaluable tools in mapping and conservation of endemic species, and also to understand the relationship between a species and its abiotic and biotic environment and which in turn can help us to generate a predictive map of where populations could potentially occur. For modeling the distribution of these species, I used MaxEnt and Ensemble methods. Species distribution models (SDMs) are used to understand the relationship between species and their environment which is then used to generate a predictive map of where populations could potentially occur. I compared these two methods and to show that Ensemble methods are better than single models. The most important environmental factor varied greatly from one species to another. However, it was observed that Precipitation of the Coldest Quarter, Slope and Forest Canopy Height contributed the most for a number of species.
For my third chapter, I used the results of species distribution modeling (binary maps) from the previous chapter to carry out preliminary assessments of conservation status of 151 endemic woody plants of Western Ghats, based on the categories and criteria proposed by the IUCN. I applied IUCN Criterion B for risk assessments and found that more than 50% of the endemic woody plants are threatened (1.9% Critically endangered, 23.84% Endangered, 30.46% Vulnerable). Of 151 endemic species, only 56 species have been assigned a conservation status by IUCN.

DCC/WWC Meeting

Controversies in wildlife management: feral cats, feral horses and dingoes

We present the first global analysis of elevational gradients in functional and phylogenetic diversity of birds and test for signals of deterministic processes in community assembly. Further, we examine for latitudinal effects in the strength of these deterministic processes.

We systematically selected, compiled and analyzed published data on bird diversity along elevational gradients. For each gradient, we calculated functional and phylogenetic diversity across elevations and described the main patterns for each diversity metric. Then, we calculated standardized effect sizes (SES) of each metric and used these SES values to (1) test the signals of environmental filtering and limiting similarity as deterministic processes shaping assemblages across elevations and (2) to compare changes in within-mountain diversity, among mountains located at different latitudes.

Birds displayed eight different patterns of functional and phylogenetic diversity across elevations, but no global pattern of increase or decrease was found. There is, however, a consistent global pattern of phylogenetic clustering, with mountain species being more closely related to each other at any given elevation. Latitude had a significant effect on within-mountain changes in functional and phylogenetic diversity across elevations, with more negative slopes (stronger decline in diversity metrics with increasing elevation) in tropical mountains.

Our findings challenge the idea that the decline of functional and phylogenetic diversity with elevation is a general pattern, emphasizing the uniqueness of each mountain system. In spite of this great variability, we found a latitudinal effect in the patterns of within-mountain functional and phylogenetic dispersion of birds after controlling for effects of species richness. Environmental filtering, thus, may act differently in tropical and temperate mountains, and calls for more comparative studies on the mechanisms driving community assembly at different latitudes.

We are organizing a One-day symposium themed Collective behaviour on Sept 13th, 2019 at Centre for Ecological Sciences, IISc. The objective of this event is to bring together researchers in Bengaluru working in the area of collective behaviour/phenomena from diverse fields- ecology to physics and engineering.

Tea

9:00-9:15

Session 1

9:15-9:40

Prof Sriram Ramaswamy, Physics, IISc: Flocks in fluid

9:40-10:05

Dr Divya Bellur,APU: Collective behaviour in prey capture and web-building in socia spiders

10:05-10:30

Dr Shashi Thutupalli, NCBS: Probing the physical basis of metabolism

Posters and Tea

10:30-11:30

Student posters + Tea

Session 2

11:30-12:30

Prof Guy Theraulaz, CRCA, CNRS, France & Infosys Chair Professor at IISc: Secrets of a swarm architect: how do ants coordinate their actions to build their nest

Break

12:30-14:00: Lunch

Session 3

14:00-14:20

Dr Danny Raj, Chemical Engg., IISc: Moving through a crowd: a nature-inspired traffic rule

14:20-14:40

Dr Maria Thaker, CES, IISc: The Moving Megaherbivore

14:40-15:00

Dr Mohit K Jolly, BSSE, IISc: United cancer cells stand, divided they fall: decoding mechanisms of collective cell migration during cancer metastasis

Posters and Tea

15:00-15:45: Student posters + Tea

Session 4

15:45-16:10

Dr Varsha Singh, MRDG, IISc: Plasticity in the swarming behavior of Pseudomonas aeruginosa

16:10-16:35

Dr Vijaykumar Krishnamurthy, ICTP, IISc: Patterns in active fluids: nonlinear oscillations, boundary shapes, manifolds and all that

16:35-17:00

Prof Raghavendra Gadagkar, CES, IISc: How wasps choose their new queens - the most important and least understood collective behaviour in the primitively eusocial wasp Ropalidia marginata

Presenters-Posters

Satyajeet Gupta, CES, IISc: Density-dependent fitness effects of hitchhikers on a mutualism

Nikita Zachariah, CES, IISc: Brick-laying to Building Mud Castles: Mound Construction by a Fungus-farming Termite

Tarun, Karthika, Nipun, Civil Engg. IISc: Understanding the Dynamics of a Spiritually Motivated Crowd - Experiences from Kumbh Mela - 2016

Sree Subha Ramaswamy, NCBS: Role of water and pheromones in mound-building behaviour of termites

Hemalatha Somanathan, NCBS: Bee curtain of Asian dwarf honey bee Apis florea

Jitesh Jhawar, CES, IISc: Emergent group-level patterns in fish are explained by simple pairwise interactions

Aakanksha, CES, IISc: Lek polygyny: emergent group behaviour in the mating context

Organizing team,

Jitesh Jhawar (CES, IISc)

Vishwesha Guttal (CES, IISc)

Danny Raj (Chem Engg, IISc)

Pritha Kundu (CES, IISc)

Animals communicating in the context of mate searching benefit by obtaining mates, but also experience costs. Empirical work studying effect of predation on such communication has largely been addressed in an evolutionary context. How individuals trade-off risks and benefits of communication in an ecological context has, however, received much less attention. With this backgroud, my thesis aims at understanding the ecology of predator-prey interactions in the context of mate searching communication, using the tree cricket Oecanthus henryi as a model system. I first estimated the relative predation risk experienced by communicating and non-communicating, male and female crickets from their primary predators, green lynx spiders, at multiple spatial scales within a night. Next, I manipulated predation risk in enclosure experiments and observed how it affects mate searching behaviour and survival, to compare their relative fitness consequences. Finally, I examined how crickets and spiders use space at two different spatial scales, in order to explore whether crickets behaviourally manage the risk they experience while searching for mates.

Spatial ecology incorporates concepts of distance and area, including the granularity of a habitat, a substrate, or a process. A main question is: How do the spatial arrangements of organisms, populations, and landscapes influence ecological dynamics. Spatial ecology applies at various scales, to both the observations and of the processes of interest. These scales range from a cell, to a leaf, a tree, a forest, a continent or the planet. The observations and processes can be at different scales. For example, we could observe disease transmission between two individuals because of our interest in disease spread over a continent. A fundamental concept of scale is its association with species diversity, as shown using ``island biogeography’’. Classically, on literal islands, species diversity increases with island area and with proximity to the mainland. The “island” ideas extend more generally so, for example, local diversity depends on area of a habitat and number of species in the surroundings. The spatial arrangement of habitat affects the distribution and dynamics of populations. For example, continuous habitats allow for well-mixed populations, and fragmented habitat result in semi-isolated or isolated populations. “Metapopulation/Metacommunity” theory applies to fragmented landscapes in which relatively isolated local populations undergo periodic colonizations and extinctions. Despite local extinctions, the recolonizations can allow the collection of local populations to persist indefinitely. Finally, spatial landscape structure doesn’t only affect dynamics of populations, it also affects the genetic structure and genetic diversity of populations, the process of evolution, and which traits evolve.

Individuals interact with others of their kind, and with other species. In some cases just a few interactions can explain a lot about population dynamics and the structure of communities. This leads to simple explanations of observed patterns. In other cases population dynamics depend on the mixed effects of many processes, biotic and abiotic. I am interested in both cases. My work is founded in natural field settings and mostly involves parasitoid wasps and the species with which they interact. I use observational studies, manipulative experiments, population genetics, modeling, and analyses of long-term survey data.

The research system in this talk is a plant-insect community inhabiting 4000 habitat patches. Starting with individual behavior, I ask why a parasitoid uses only 1/3 of an available, yet limited, resource? How can this behavioral restraint be maintained? Next, I consider multitrophic indirect interactions, going as far as the fourth trophic level. I find, for example, that plant chemical defense and plant volatile cues determine the structure of the community. Moving to population dynamics, in classic textbook descriptions, host-parasitoid dynamics have density dependent oscillations. In fact, density dependence is often not evident. I will show, for a butterfly and two host-specific parasitoids, what factors actually control their short-term population dynamics. Finally, using a 25-year survey of six interacting species, I test the ability of direct and indirect interactions to explain large-area and long-term trends. While multiple interactions are needed to understand many short term and local phenomena, only a few are needed to explain large scale community dynamics. Weather plays a big part, and its influence is increasing.