Academic

Topic: 
Biogeography of lizards of the family Scincidae (skinks) from the Indian subcontinent
Speaker: 
Dr. Aniruddha Datta Roy, IISc, Bangalore
Date & Time: 
18 Jun 2024 - 3:00pm
Event Type: 
Invited Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Abstract:

The Indian subcontinent has a unique geological history. Its unique history in conjunction with the topological and climatic heterogeneity has resulted in incredible biotic diversity. In this talk, I focus on lizards of the family Scincidae (commonly known as skinks) as a model system and provide a synthesis of studies that unravel their biogeographic patterns in the Indian subcontinent. As a part of this synthesis, I also highlight some of the studies from my lab at NISER Bhubaneswar (https://biogeosys.in/) that have contributed to our understanding of Indian skink biogeography.

Topic: 
End of an era: Evolutionary Design of Pan-efficacious Next-generation Snakebite Therapy
Speaker: 
Arpan Samanta, IISc, Bangalore
Date & Time: 
12 Jun 2024 - 3:00pm
Event Type: 
Departmental Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Venom is a complex cocktail of biologically active proteins, salts, and organic molecules. The venom toxin-coding genes in animals have convergently originated from endophysiological protein-coding genes via gene duplication, followed by accelerated evolution. Venom research has primarily focussed on snake venoms because of their remarkable compositional variation and the negative impact of snakebites on human health. Research has highlighted that conventional antivenom, the mainstay treatment for snakebites, is ineffective in countering the inter and intraspecific variations in snake venoms. Therefore, in the first chapter of my thesis, I will employ our understanding of venom evolution to design a broadly effective snakebite therapy. With the help of comparative venom gland transcriptomics and evolutionary analysis, I will identify regions in the major venom toxins that remain conserved across populations, regions and even species. I will then synthesise sequences coding these epitopes and undertake DNA immunisation of small mammals (e.g., mice and rabbits). I will employ advanced technologies in antibody discovery, including B cell sorting and yeast display selection, to discover and recombinantly express neutralising antibodies. By targeting such conserved epitopes in the major venom toxins, particularly the three-finger toxins (3FTx) and snake venom metalloproteases (SVMP) from multiple species of elapid and viperid snakes, I aspire to achieve a broad breadth of neutralisation against the most medically important snakes of the Indian subcontinent.

In addition to the evolutionary design of antibodies, I will explore the potential use of animal immunisation with specific toxin families in discovering broadly neutralising antibodies (bNAbs). In Chapter II, I will attempt to discover bNAbs from large mammals immunised with the major venom toxin families from snakes in India and sub-Saharan Africa. Since the immune systems of these animals only get exposed to the major snake venom toxins, it greatly enhances our chance of discovering bNAbs against snakes across continents.

In addition to claiming the lives of over 58,000 Indians annually, snakebites result in over a hundred thousand immutable injuries each year. Research demonstrates that conventional antivenoms are ineffective in countering the morbid effects of snake envenoming. Unfortunately, very limited research has been undertaken towards solving this socioeconomic problem. Therefore, in the third chapter of my thesis, I will undertake an antibody discovery campaign to discover and recombinantly express neutralising antibodies against toxins that inflict morbid symptoms. I will exploit the unique properties of the camelid single heavy chain antibodies (VHH), which offer several advantages over mammalian immunoglobulins, including smaller size, greater tissue penetration potential, and thermostability. As these VHH antibodies are easy to manipulate and humanise, they will greatly reduce the adverse effects of snakebite treatment. 

Overall, with the broadly neutralising antibodies discovered against 3FTx and SVMPs - the two major toxin families in India’s medically most important snakes - I hope to save the lives, limbs and livelihoods of India’s 100,000 annual snakebite victims. In addition to advancing snakebite therapeutics, the findings of my thesis will shed light on the evolution of this highly adaptive complex cocktail.

Topic: 
Strategies of sexual signalling in Peninsular rock agama Psammophilus dorsalis
Speaker: 
Aravind Sridharan, IISc, Bangalore
Date & Time: 
4 Jun 2024 - 3:00pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Abstract:

Inter-sexual selection, or mate choice results in the evolution of expensive and conspicuous traits in many systems. The use of such traits in attracting mates is called sexual signalling. Sexual signalling has largely been studied in the context of indirect competition among males and mate choice by females. Historically, sexual signalling in females was expected to be of limited consequence. However, there is growing evidence of sexual signalling in females that involve energetically costly investments and elaborate conspicuous traits. Do females modulate the use of sexual signals to maximize benefits and minimize costs?

Given the limited understanding of sexual signalling by females in polygynous mating system, we first examined the repertoire of sexual signalling exhibited by females of the Peninsular rock agama Psammophilus dorsalis. We further investigated how females strategically use their sexual signals in response to important factors that may affect the benefits of signalling. In socially polygynous mating systems, males typically invest in elaborate ability-based or honest displays which are intended towards female receivers. Although strategic signalling in males has received greater research attention, here too key questions of how competitors may affect their signalling is poorly understood. Sexual signalling males typically experience male competitors in their environment. We lack a comprehensive understanding of the impact that such unintended audiences have on male sexual signals. We studied how strategies of male signalling are shaped by both mate and competitor environments.

To understand the repertoire of sexual signalling, we set up a context for females to display by simulating the presence of a breeding male by presenting artificial male models to individually tagged female lizards. We found that females use a range of behaviours including stereotypical body postures and dynamic colour signals. We compared the response of lizards to cues of intra-sexual competition and found that distinct signals were used in the contexts of mate attraction and intra-sexual competition.

To understand how females strategically use their sexual signals, we evaluated key hypotheses for how females should modulate their signalling, including male quality, access to high quality mates and breeding season. We simulate male quality using artificial male models to individually tagged, and intensely monitored wild female lizards. We found that females invest

more in signalling towards high quality males and increased their investment towards the later part of their only breeding season. Contrary to that which is typically expected in a polygynous mating system, females not only invest in costly and elaborate sexual signals, but they also modulate their usage to maximise their benefits and minimise their costs. We argue that, even in polygynous mating systems, dispersed distribution of individuals can result in females experiencing limitation in mate availability, resulting in costly sexual signalling.

To understand how males strategically use signals in response to a combination of competitor and mate environments, we collected information on where lizards were found relative to other conspecific lizards. Since Peninsular rock agama change colour states, we then identified how individuals strategically modulate the use of colour signals with respect to other lizards present in their vicinity. We measured the relative size of male neighbours as size can be a measure of competitive ability in contest competitions. We find that individuals appear to modulate the use of sexual signalling in response to both males and females in the vicinity. We found that displays increased with increase in the potential number of mates, and decreased with competing male effect. We found that relative size affects their response to competitor abundance, with smaller males reducing the use of sexual signals in competitor environments.

My thesis highlights the wide repertoire of sexual signals seen in females of a socially polygynous species of lizard and the strategic use of sexual signalling in both males and females. Females exhibit sexual signalling with well-defined sexual signalling postures and colour-based displays that are different from other social contexts. Females, not only use their signals in specific contexts but also use them where they gain maximum benefits. The study emphasizes the scarcity of high-quality males that females may encounter, even in species adhering to conventional sex roles. We demonstrate how female invest in sexual signalling in response to both quality of mates as well as the time of breeding season. We highlight how males flexibly modulate the use of sexual signals through their colour trait in a dynamic environment with breeding females and competing males. My thesis challenges the conventional sex roles in sexual signalling while also investigating the nuanced mating strategies of males and females in a polygynous lizard.

Topic: 
Alternative reproductive tactics in Oecanthus henryi
Speaker: 
Mohammed Aamir Sadiq, IISc, Bangalore
Date & Time: 
30 May 2024 - 3:00pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Alternative reproductive tactics (ARTs) are discrete phenotypes employed by individuals of either sex within a species to maximize their reproductive success in varying social and environmental conditions. These tactics often involve different ways of competing for mates or different tactics for parental investment. Conditional ARTs are a class of ARTs where individuals express an ART depending on an extrinsic or intrinsic cue. The fitness of conditionally expressed ARTs may not necessarily be equal for their persistence. However, there exists a class of conditional ARTs called reversible or flexible ARTs wherein individuals reversibly switch between ARTs in response to a cue. In systems which show flexible ARTs, selection could favour genotypes that gives rse to ARTs that have similar fitness. By virtue of the similarity in mating benefits amongst ARTs, individuals can seamlessly switch between ARTs depending on cues without necessarily incurring fitness losses. My thesis attempts to evaluate the mating benefits as a fitness component of flexible ARTs in Oecanthus henryi. Oecanthus henryi is a tree cricket found in the scrublands of the Indian sub-continent. O. henryi males flexibly adopt three different ARTs to obtain mates. Males can either call to attract females or remain silent. Males can adopt a third tactic, called baffling, wherein males call through a hole they make near the centre of a leaf on their host plant. Baffling is known to amplify the call of a male. In the first chapter of my thesis, I used data from a previously conducted mesocosm experiment to study the expression and mating success of calling and silent ARTs under varying predation risk from their natural predator, the green lynx spider (Peucetia viridans). The findings of the study showed that males were equally likely to call or remain silent on a night and the mating successes of both the ARTs were similar across a steep predation gradient. The similarity in mating success across varying ecological contexts may allow individuals to switch between them without incurring mating related costs. Furthermore, silent males were more likely to aggregate around other callers than callers themselves and obtained a majority of their matings by doing so, which suggests that silent males employ satellite behaviour. In the second chapter of my thesis, I explored the adaptive value of satellite behaviour. While literature suggests that individuals employ satellite behaviour to get mates, its relative advantage over other non-bourgeois tactics remains unexplored. Through laboratory experiments, I showed that silent males do not gain additional mating benefits by behaving as satellites, suggesting that satellite strategy may not be the only alternative tactic employed by silent males to get mates. In the third chapter of my thesis, I investigated why baffling is not commonly observed in the field given its amplification advantage over the other two ARTs, silent and calling. Using an individual-based modelling approach, I explored whether frequency-dependent, density-dependent selection or habitat structure could limit the mating success of bafflers. The results of the study showed that the co-existence of these tactics over ecological time scales is facilitated by the spatial structure of the landscape they inhabit, which served to equalize the otherwise unequal mating benefits of the three tactics. In the last chapter of my thesis, I explore the mortality costs of the two ARTs due to predation. Through laboratory experiments using the green lynx spider as the predator, I showed that the three ARTs elicit a very low but similar likelihood of being attacked and the mortality costs related to these attacks are negligible. The findings suggest that the three ARTs are mildly vulnerable to predation by their natural predator. In summary, my thesis demonstrates that the ARTs expressed by O. henryi provide similar mating benefits. The similar mating benefits of the ARTs and negligible mortality costs due to predation may allow O. henryi males to maximise fitness in varying ecological conditions.

Topic: 
Risk management: How predators shape prey ecology, evolution, and the ecosystem
Speaker: 
Viraj Torsekar, IISc, Bangalore
Date & Time: 
28 May 2024 - 3:00pm
Event Type: 
Research Talk
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Abstract:

Prey traits that facilitate matings and help forage are shaped by a combination of sexual selection and natural selection as they also tend to attract predators. At the ecological scale however, prey individuals manage this predation risk by altering conspicuous traits and behaviours leading to adverse fitness consequences. Therefore, predicting any evolutionary change as an outcome of risk management requires an understanding of the underlying mechanisms governing predator-prey interactions. By developing and addressing theoretical predictions using empirical evidence collected with a combination of field experiments, enclosure experiments, and computer simulations I investigate the following research themes: (a) predation cost of mate searching and fitness consequences of prey defence responses (space use and alternative reproductive tactics), (b) scaling up of individual prey responses to emergent population mating patterns (assortative mating), and (c) the role of habitat choice in potentially structuring populations through assortative mating. Having examined species interactions at individual- and population-level, I then go on to integrate these ideas along with climate into an ecosystem-level framework, to (d) investigate the role of animals in litter decomposition across a precipitation gradient. Based on these results, I develop a framework and link it to my short- and long-term plans which include unifying prey responses in the context of foraging and reproduction, phenotype-environment matching, effect of climate on species interactions, and ecosystem function.

Topic: 
About supergenes that build supercolonies
Speaker: 
Aparna Lajmi
Date & Time: 
21 May 2024 - 3:00pm
Event Type: 
Invited Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Convergent evolution of traits is a common feature across the tree-of-life. However, only certain taxonomic groups repeatedly evolve a specific suite of traits and very little is known about why this is not widespread. In ants, one such complex trait is polygyny (multiple-queen colonies) which has evolved repeatedly from an ancestral phenotype of a monogyne(single-queen colony).  Polygyny results in large supercolonies made up of unrelated workers and several behavioural, morphological, and life history modifications. I will talk about my postdoctoral work examining the genomic basis of such a trait in the desert ants from Israel, where both these traits are found in a single population. I find that differences in the number of queens is associated with the presence of a supergene, a large non-recombining region of a chromosome that codes for a complex trait, much like a sex chromosome. I then discuss how this supergene is inherited, maintained, and possibly introgressed into other lineages. Finally, we look at how conserved this region is and hypothesize about the genomic basis for repeated evolution of such traits.

Topic: 
Pandora’s box: Deciphering the evolutionary ecology of snake venoms and its impact on snakebite therapy in India
Speaker: 
Senji Laxme R R, IISc, Bangalore
Date & Time: 
7 May 2024 - 3:00pm
Event Type: 
Thesis Colloquium
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

Venom, being an adaptive trait, has propelled the expansion of snake lineages across diverse habitats, such as the biogeographically distinct Indian landscapes. Natural selection optimises the potency, composition and lineage-specificity of the snake venom arsenal for effective prey capture or predator deterrence. Therefore, venoms of several closely related snake species have been documented to exhibit tremendous spatial venom variation owing to their distinct evolutionary ecology. However, research on venoms in India has predominantly focused on assessing the compositional variation in certain snake species from restricted locales. These studies have also evaluated the venom variation only from a biochemical perspective without considering the ecological and evolutionary significance of such compositional differences. Hence, several questions pertaining to the evolutionary ecology of Indian snake venoms remain unanswered.

 

Naja naja and Daboia russelii are two medically important snake species that are widely distributed across distinct bioclimatic regions of India, including arid deserts, fertile plains, rainforests and hot-humid coasts. In addition to their clinical relevance in the snakebite scenario, these two species are fascinating model systems to understand the relationship between evolutionary ecology and venom variation. This doctoral thesis was designed to decipher the relationship between various ecological and environmental determinants and the variability in N. naja and D. russelii venoms. For this, venoms of wild-caught snakes from the major biogeographic zones across the country were sampled. A multi-faceted approach involving proteomics, biochemical analysis, pharmacological assessment and toxicity studies was employed to characterise the extent of variability. These studies revealed remarkable intraspecific variation across populations of these two species. The venoms varied significantly in terms of their composition, functional profiles and toxic potencies.

 

Further, the contribution of various abiotic, biotic and life history factors in dictating this variation was evaluated. A theoretical prediction model was developed to explain the variation observed in the enzymatic activities of D. russelii venom due to the combined effect of bioclimatic variables in a region. The feeding ecology is amongst the major biotic factors that drive venom evolution. Therefore, the prey-specificity of N. naja and D. russelii venoms was examined as a proxy to understand the relationship between compositional variation and diet. The venom specificity was determined through in vitro binding and in vivo lethality experiments against distinct prey organisms.

 

In addition to interpopulation variation, venoms were documented to vary between individuals within the same population. Therefore, the extent of intersexual and ontogenetic venom variation within a population was characterised by housing multiple clutches of these venomous snakes under captivity. The differences and similarities in the venom composition, potency and specificity across sexes and ontogenetic stages of N. naja and D. russelii individuals were recorded. While intersexual variation was not observed in either of the species, marked differences were observed between the venoms of young and adult D. russelii snakes. However, adult and juvenile stages of N. naja were found to produce functionally similar venoms. These results shed light on the influence of distinct ecologies on temporal venom variation across the developmental stages of a species.

 

Finally, the repercussions of venom variation at various levels on snakebite treatment in India were investigated by performing WHO-recommended preclinical studies. These studies highlighted the shortcomings of the currently employed conventional antivenom therapy in mitigating snakebites across the country. Overall, these studies also provided valuable insights for the development of advanced snakebite therapeutics that have the potential to save the lives, limbs, and livelihood of India’s thousands of annual snakebite victims.

Topic: 
Unravelling the mechanisms of collective motion in mixed species schools
Speaker: 
Jahanvi Tiwari, IISc, Bangalore
Date & Time: 
23 Apr 2024 - 3:00pm
Event Type: 
Departmental Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

TBD

Topic: 
TBD
Speaker: 
Sofiya, IISc, Bangalore
Date & Time: 
19 Jun 2024 - 3:00pm
Event Type: 
Departmental Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

TBD

Topic: 
Investigating Correlations and Consequences of Risky Behavioural Traits in Psammophilus dorsalis
Speaker: 
CL Dheeraj, IISc, Bangalore
Date & Time: 
29 May 2024 - 3:00pm
Event Type: 
Departmental Seminar
Venue: 
CES Seminar Hall, 3rd Floor, Biological Sciences Building
Coffee/Tea: 
Before the talk
Abstract:

In nature, a single selection pressure can act on multiple traits of an individual animal, and a single trait of an animal can also be under multiple selection pressures. Given the potential for complex trade-offs acting across multiple traits, it would be more ecologically relevant and meaningful to study multiple traits of an animal in the wild, where they are simultaneously under multiple selection pressures. However, such processes have rarely been examined in animals, especially in their natural habitat. In my thesis, I will examine how risky behavioural traits are expressed under multiple selection pressures and how variation in the expression of multiple risky behavioural traits contributes to an animal’s fitness. I will also examine the correlations between different risky behaviours and test hypotheses for such correlations. I will conduct behavioural experiments on Psammophilus dorsalis in their natural habitat to answer these questions. In my 1st chapter, I will examine how natural and sexual selection factors simultaneously affect decision-making in response to threat in adult male P. dorsalis. In my 2nd chapter, I will examine correlations between multiple risky behavioural traits and their relative effects on fitness in adult male P. dorsalis. In my 3rd chapter, I will examine if the expression of risky behavioural traits is heritable in adult male P. dorsalis.

 

 

 

 

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