First author Cene Fiser gives a short version of their paper “Coevolution of life history traits and morphology in female subterranean amphipods“.
Fine-tuning evolution often requires compromises. Maximizing female’s fitness by optimization egg number and egg size to the environmental demands is a classic trade-off in evolutionary biology. But, can co-evolving morphological changes affect or even avoid this trade-off? We compared Niphargus species found in springs and in deep caves and showed that cave species are larger, stouter, have larger eggs, yet the number of eggs is not lower compared to spring species. These changes seem to be a result of decreased fluctuations of abiotic factors and of decrease in food availability in deep caves compared to springs. The environmental gradient most likely presents major source of selection that affected all herein studied morphological and life history traits. However, we have shown that the co-evolution of biological traits can modify the otherwise expected outcome of selection. We suggest that increased body size, that also enables storage of more energy, enables allocation of additional nutrients in egg size, yet the number of eggs can remain the same. Additionally, as larger eggs require better supply with water for aeration, bigger species have also modified body shape.