Arun’s paper reporting the detailed costs and benefits of evolved immune priming is now published! In an exciting earlier study, we had found that flour beetles exposed to the pathogen Bacillus thuringiensis adapted rapidly via the evolution of either immune priming or pathogen resistance. The new work – led by Arun (now at Edinburgh University) and Imroze Khan (now at Ashoka University) – aimed to test whether these distinct evolved immune responses were costly for a suite of fitness-related traits, and whether these costs could explain how the responses evolved. While we find that immune priming does impose some fitness costs, increased basal resistance appears to be surprisingly cost-free. As a bonus, we found that the enhanced level of immune priming was also transferred across generations. The project involved a ton of painstaking work and careful analysis, and we are all quite proud of the paper. Give it a read!
Shantanu’s work on female colour variation in the widespread, tiny damselfly Agriocnemis pygmaea is now out! Females of this damselfly (seen at the campus pond) come in two colors: red and blue, as well as a bunch of intermediate forms. We wondered whether these colours represent allelic forms, or ontogenic (age-related) change. From laboratory studies and field observations at the pond, Shantanu found that the colour variation is ontogenic. Females start off red, and as they mature and develop eggs, they begin to look blue, resembling males. The colour change coincides with males becoming more interested in mating with them. Read the paper here, or the NCBS news article. Photograph: Shantanu Joshi.
Kruttika’s work testing the impact of butterfly caterpillar microbiomes on growth and survival is published! This was a major collaborative effort with Krushnamegh Kunte, and very new kind of work for our lab. The results were puzzling because unlike patterns from other insects, butterflies seem to be just fine without their bacteria. But in conjunction with Rittik and Ashwin’s recent results with dragonflies, it seems that we’ve uncovered one end of the spectrum of host-microbe interactions. The end that spells “meh!” rather than “I need you”. Here’s a cartoon summary of the work by Kruttika and Shreya. Also read a lay summary here; or read the paper for more details!
Rittik Deb and Ashwin Nair’s paper on the gut bacterial communities of dragonflies is out! We sampled several species of dragonflies from different locations in India, and found that gut bacterial communities varied across host species, location, and season. For some of the dragonflies, we were also able to analyse gut contents, and found that these “generalist predators” eat quite different meals that probably end up introducing distinct bacteria in their guts. So, unlike in most other insects, dragonfly gut bacterial communities seem to be transient and are neutrally assembled (rather than host-selected). Read the paper for more details. Meanwhile, enjoy this beautiful summary of the paper by Pranjal Gupta!
Here’s the latest from Imroze and Arun. A couple years ago we had found surprising levels of variability in immune memory (“priming”), across 10 wild-collected flour beetle populations (Khan et al 2016, Ecology and Evolution). In our new follow-up paper, we figured out what may explain this variation, by systematically analysing change in various fitness components in the populations, after priming. In a nutshell, it appears that priming is beneficial both for reproduction and for survival; but the relative benefits of priming may trade off. So, priming is stronger in beetle populations that are more susceptible to the pathogen; but it is weaker in populations that have a larger investment in fecundity after priming. Read the paper to find out more!