About a month ago, Dr. Alex Reis, a freelance science journalist from Germany wrote to me asking for comments on a new publication in Nature Communications on predatory cannibalism in Drosophilla melanogaster larvae.
Dr. Reis’s article, which appeared in the Munich Eye, quotes me on the importance of such work.
Here are full text of questions that Dr. Reis sent me, and my answers:
Why study cannibalism?
Cannibalism is a puzzling phenomena when viewed from the perspective of a Darwinian individual who is trying to increase his/her chances of survival, and thus increase fitness. No doubt that cannibalism has benefits because conspecifics offer near ideal nutritional package. But it also means the individual is at risk of being cannibalized by other conspecifics!
Given the potential risk of death, even with the best nutrition, its not at all clear why so many species across taxa exhibit cannibalism, and under what circumstances can cannibalism evolve. Apart from what it means to individuals, cannibalism can regulate competition within and between species, and therefore their population dynamics as well. All this makes the study of cannibalism extremely important.
What do you think is the evolutionary relevance of this study?
A major challenge in studying evolution of cannibalism is that it is typically not easy to disentangle various costs and benefits associated with cannibalism with other confounding factors (of course, this is a general issue in studying the evolution of any animal behaviour). Moreover, we can very rarely see what sort of changes driven by natural selection can occur over evolutionary time scales.
Vijendravarma et al succeed overcoming these challenges by a simple and elegant experimental study. They chose Drosophila melanogaster which is an extremely well studied lab model system and clearly identify both proximate and ultimate factors that are influencing cannibalism. Importantly, they are also able to observe the rapid evolution of cannibalistic traits by running experimental evolution in nutrient limited environments. So, this paper provides a compelling evidence for how malnutritioned environments can lead to the evolution of cannibalism, and also maintain polymorphism in cannibalistic species.
What can it teach us about the biology and genetics of Drosophila and possibly other insect species?
First, this paper shows that Drosophilla may have a new regulating factor affecting interactions and population dynamics of both this and other species of Drosophilla (i.e., earlier, people have considered competition within and between species, but not cannibalism!). It also suggests that Drosophilla offers sufficient genetic variations in their populations leading to rapid evolution of cannibalism in a few experimental evolutions conducted in laboratory.
Secondly, many studies on cannibalism have focussed on morphological features of species that provide arms (and defenses) for/against cannibalism or chemical signal that may induce or prevent cannibalism, whereas this study could potentially open up ways for exploring new avenues such as genetic or even neuronal for cannibalism.