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.

Understanding the causal processes that have generated the stunning biodiversity in tropical forests has been fundamental to ecological and evolutionary research. In this talk, I will explore the role of the geographical, geological and ecological processes on biogeography and diversification among two arthropod groups (centipedes and butterflies) at different spatial scales, the Western Ghats in peninsular India and the South and Southeast Asia. To this end, I have integrated multiple lines of evidence, including DNA sequences, morphological traits, and data from geology, climate, and ecology, finding that geographic and geo-climatic processes have played an important role in diversification in both centipedes and butterflies. While some of the molecularly-delineated centipede species did not exhibit morphological divergence, they occupied distinct climatic niches across the Western Ghats, suggesting ecological speciation. Butterflies showed morphological variation in wing patterns and mimicry, which are thought to be involved in ecological adaptation. However, there was no significant effect of wing pattern diversity, and mimicry detected on diversification rates, indicating that geographic factors played an important role in their diversification. These two case studies highlight the need to assess multiple ecological and evolutionary axes when examining diversification patterns and processes. I will follow this by demonstrating the use of molecular phylogenies and biogeography to understand community assembly of species, which has traditionally been studied from under an ecological lens. I will show that evolutionary history, biogeographic isolation, and stochastic colonisation influence assembly of mimetic butterfly communities.
Towards the end, I will talk about my future research, where I plan to focus on exploring processes that influence extant diversity patterns using multiple soil arthropods taxa that vary across evolutionary and ecological gradients. Currently, such multi-taxa and multi-disciplinary studies are lacking in India and are limited to few studies in the world. I hope insights from these studies will contribute towards our understanding to broader questions in evolutionary biology such as: How did tropical biodiversity originate and how is it maintained? Why are the tropics so species rich? Why are some lineages more diverse than others? Also, I hope to contribute substantially towards understanding arthropod evolution and systematics in one of the most biodiverse and less explored regions in the world.

Exploring drives of ecological communities has been central to community ecology. Multiple factors have thought to influence community structure, including geographic isolation and area, niche-based, neutral, and historical processes. In the last two decades, community phylogenetic framework has emerged to integrate both ecological and evolutionary processes and their role in community structure.
Community phylogenetic method explicitly incorporates species’ evolutionary relationships, a proxy for how species are similar to each other based on DNA data. It helps to understand the relative role of different factors such as phylogenetic inertia, biogeography, and more contemporary ecological processes such as competition, habitat filtering, and predation simultaneously. It also helps community ecologists to link short‐term local processes to continental and global processes that occur over deep evolutionary time scales. In this lecture, I will discuss the merging of community ecology and phylogenetic biology, highlighting the challenges, debates, and new areas of enquiry in this field.

Thesis defense

Thesis Colloquium

Thesis Colloquium