"The Matthew effect in biology, or: do social insect queens really reverse the fecundity-longevity tradeoff?"Zug, RomanSocial insects seem to contradict one of life-history theory’s fundamental predictions: the tradeoff between fecundity and longevity. It is not always acknowledged, however, that this notion actually comes in two flavors. The first, and more intuitive, variant states that queens not only monopolize reproduction, but also live much longer than workers. The second variant is less well known, but more challenging to explain: among queens, those that lay more eggs are also observed to live longer. Here we tackle the latter issue. Previous theory has convincingly argued that life-history tradeoffs can be masked by differences in resource acquisition, yielding positive fecundity-lifespan relationships in observational data. We extend this work to consider self-reinforcing dynamics in which colonies with a subtle advantage in resource acquisition, due to nothing else than luck (demographic stochasticity), accumulate further advantage over time, analogous to the well-known Matthew effect. We show that this dynamics easily masks the underlying fecundity-longevity tradeoff. Additionally, while allocation variation between individuals can unmask the tradeoff to be more easily visible, our modelling suggests that reasonable values for this variation may still not be sufficient to unmask the tradeoff. Our findings suggest that experimental manipulation of reproductive effort is crucial to detect life-history tradeoffs in social insects and beyond. |
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