Dataset of diverse evolutionary pathways shape cichlid egg size in Lake Tanganyika

Optimal egg size is a classic and important concept in life history
theory. Here, we examined the ecological factors affecting egg size, using
a comparative analysis of 83 cichlid species from Lake Tanganyika, which
employ either a mouth-brooding or substrate-brooding. The two strategies
differ substantially in regard to spatial limitations and food
availability for offspring, potentially leading to divergent responses to
the ecological factors influencing egg size. We observed a strong negative
correlation between egg size and egg number in species that exhibit
mouth-brooding, but not in substrate-brooding cichlids. Our results
suggest that the importance of the relationship between clutch size and
egg size varies substantially between these two types of parental care.
Interestingly, in mouth-brooding species, we found that egg size increases
when offspring exhibit external feeding behaviors (grazing behavior). We
also demonstrate that substrate-brooding species with shorter periods of
parental care typically produced larger eggs, compared to species with
relatively longer periods of parental care. Overall, our results
demonstrate that behavioral differences, including parental care type and
duration, play an important but often overlooked role in the evolution of
egg size across species.