Biology subjects

Pal, R. S.

Publications and source records attributed to Pal, R. S..

3 recordsLinked to original sources

bioRxiv2025

Sexual conflict over mating duration and frequency in Zygogramma bicolorata

Duration and frequency of mating are the most prominent aspects of mating behaviour over which sexual conflict can occur. Parthenium beetle (Zygogramma bicolorata) exhibits an extremely high mating rate, with each mating typically lasting several hours. We investigated mating behaviour in this beetle to assess if there is sexual conflict. Theories of sexual conflict predict that such mating behaviour, while being beneficial to the males, should be detrimental to the females with regard to reproduction and/or survival. We experimentally manipulated the length and number of matings, and examined the effect on fecundity and survivorship of the females. While long mating has previously been identified as a mate-guarding strategy that benefits the males, our data reveal that it is detrimental to female fitness, supporting the sexual conflict hypothesis. Further, we checked natural variation in mating duration and its correlation with key fitness components. Our results show that female longevity is negatively correlated to reproductive rate, but positively correlated to lifetime reproduction. We argue that such a pattern is consistent with sexual conflict. While being the first clear demonstration of sexual conflict in this species, we discuss its significance, including a potential role in reducing its efficacy as a biocontrol.

animal behavior and cognition↗

bioRxiv2024

Adaptation to yeast restriction through the evolution of resource acquisition, macronutrient reserve, and ovarian function

Optimization of reproduction under dietary adversity is an important aspect of diet-dependent adaptation. Yet, little is known about the mechanism of such adaptive evolution. Here, we investigated a set of experimentally evolved populations of Drosophila melanogaster where early-life fecundity evolved as an adaptation to chronic protein restriction. We tested the role of resource acquisition and macronutrient storage, and changes in ovarian function that could have allowed such reproductive adaptation. We show that higher early-life fecundity was associated with the increased larval feeding rate, aiding in accumulation of higher protein content at the time of eclosion. Further evidence also suggests increase in reproductively allocated lipid content. Evolved females were found to have larger ovaries that also had a higher number of mature, post-vitellogenic oocytes that seem to readily allow the attainment of higher fecundity. Our results further show the evolution of plasticity in ovariole count (depending on mating status) and total egg-chamber count in females. These results are important in understanding the putative role of genetic variance and covariances that aid or limit the evolution of reproductive optimization, especially under nutritional adversity.

evolutionary biology↗

bioRxiv2024

Long mounting with repeated copulations in Zygogramma bicolorata: A test of adaptive significance of a curious mating behaviour

Long matings are abundant in insects despite the range of the costs involved. The causes and consequences of the evolution of long matings remain an interesting problem for behavioural ecologists. We studied the Parthenium beetle (Zygogramma bicolorata), which is known to show extraordinarily long copulations. Our detailed investigation showed, for the first time, that the long mounting in this species entails repeated copulation. Each of these copulations is preceded and succeeded by a leg-rubbing behaviour. We found the same characteristic pattern in laboratory and semi-natural conditions. We conducted a series of interrupted mounting assays to examine the fitness consequences of the duration of mounting. We tested multiple hypotheses regarding the transfer of sperm and non-sperm components, and the function of leg rubbing in modulating the female copulatory behaviour. Sperm transfer and fertility did not exhibit a linear increase with the number of copulations. There was also no evidence of nutrient transfer by the males. In contrast, our experiments reveal significant cost of long mounting in these beetles. We showed female remating behaviour can be modulated by the long previous mounting. Our data also suggest that leg rubbing may reduce female resistance to mating. While the long mating possibly serves as copulatory mate guarding, the males may increase their competitive ability through modulating female remating. We also propose leg rubbing to be a copulatory courtship behaviour. Our study provides preliminary insights into the evolution of long mating in such systems and necessitates further research on sexual selection.

animal behavior and cognition↗