@article {158954, title = {Mutation bias alters the distribution of fitness effects of mutations.}, journal = {PLoS Biology}, year = {2025}, abstract = {

Mutation bias is an important factor determining the diversity of genetic variants available for selection. As adaptation proceeds and some beneficial mutations are fixed, new beneficial mutations become rare, limiting further adaptation. The depletion of beneficial mutations is especially stark within the mutational class favored by the existing mutation bias. Recent theoretical work predicts that this problem may be alleviated by a change in the direction of mutation bias (i.e., a bias reversal). If populations sample previously underexplored types of mutations, the distribution of fitness effects (DFE) of mutations should shift towards more beneficial mutations. Here, we test this prediction using\ Escherichia coli, which has a transition mutation bias, with ~54\% single-nucleotide mutations being transitions compared to the unbiased expectation of ~33\% transitions. We generated mutant strains with a wide range of mutation biases, from 97\% transitions to 98\% transversions, either reinforcing or reversing the wild-type transition bias. Quantifying DFEs of ~100 single mutations obtained from mutation accumulation experiments for each strain, we find strong support for the theoretical prediction. Strains that oppose the ancestral bias (i.e., with a strong transversion bias) have DFEs with the highest proportion of beneficial mutations, whereas strains that exacerbate the ancestral transition bias have up to 10-fold fewer beneficial mutations. Such dramatic differences in the DFE should drive large variation in the rate and outcome of adaptation, suggesting an important and generalized evolutionary role for mutation bias shifts.

}, doi = {10.1371/journal.pbio.3003282}, author = {Sane, M and Parveen, S and Agashe, D} } @article {77386, title = {Ontogenic colour change, survival, and mating in the damselfly Agriocnemis pygmaea Rambur (Insecta: Odonata)}, journal = {ECOLOGICAL ENTOMOLOGY}, year = {2020}, month = {04/2020}, abstract = {

1. Damselflies often show intra-specific colour variation, which may represent genetic polymorphism or age-related (ontogenic) colour changes.

2. Such variation has distinct implications for the species{\textquoteright} ecology and evolution. Colour variation in females of the damselfly Agriocnemis pygmaea was studied, which range from blue male-like individuals (andromorphs) to those with a distinct red colour (heteromorphs). From preliminary observations, it was hypothesised that this species exhibits ontogenic colour change from heteromorph to andromorph coloration.

3. Mark-recapture experiments and egg counts of dissected females suggested that immature females are heteromorphic and gradually begin to resemble males as they attain sexual maturity.

4. Reflectance spectra of field-caught individuals indicated that, although males are indistinguishable from andromorphs, they could be easily differentiated from heteromorphs.

5. Finally, field observations and mate choice experiments showed that males rarely attempt to mate with heteromorphic females and prefer andromorphs. Together, this study{\textquoteright}s results suggest that the observed colour variation in A. pygmaea females is ontogenic and is associated with sexual maturity.

}, doi = {10.1111/een.12879}, author = {Joshi, S and Agashe, D} } @article {4893, title = {Host-specific, spatial and temporal variation in culturable gut bacterial communities of dragonflies}, journal = {Current Science}, volume = {110}, year = {2016}, month = {25 April 2016}, pages = {1513-1523}, abstract = {

Many microbial communities are associated with specific animal hosts, with major impacts on the ecological and evolutionary dynamics of both partners. We analysed gut microbial communities of eight dragonfly species in southern India. Adult dragonflies are generalist opportunistic predators; thus, we expected to find relatively high individual variation but low host-specific variation in their gut community composition. However, we find that each host species has a distinct gut bacterial community, with sampling location and month playing a small but significant role in shaping community structure. These patterns suggest that dragonflies either specialize on subsets of available prey, or their guts impose differential selective pressures resulting in distinct communities.

}, author = {Nair, A and Agashe, D} }