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At least 271 records · Page 15Linked to original sources
PubMed2006

Life history evolution in cichlids 2: directional evolution of the trade-off between egg number and egg size.

The negative relationship between offspring number and offspring size provides a classic example of the role of trade-offs in life history theory. However, the evolutionary transitions in egg size and clutch size that have produced this negative relationship are still largely unknown. Since body size may affect both of these traits, it would be helpful to understand how evolutionary changes in body size may have facilitated or constrained shifts in clutch and egg size. By using comparative methods with a database of life histories and a phylogeny of 222 genera of cichlid fishes, we investigated the order of evolutionary transitions in these traits in relation to each other. We found that the ancestral large-bodied cichlids first increased egg size, followed by a decrease in both body size and clutch size resulting in the common current combination of a small-bodied cichlid with a small clutch of large eggs. Furthermore, lineages that deviated from the negative relationship between clutch and egg size underwent different transitions in these traits according to their body size (large bodied genera have moved towards the large clutch/small egg end of the continuum and small bodied genera towards the small clutch/large egg end of the continuum) to reach the negative relationship between clutch size and egg size. Our results show that body size is highly important in shaping the negative relationship between clutch size and egg size.

Animals↗
PubMed1997

The evolution of insect flight: implications for the evolution of the nervous system.

The Insecta encompasses a prodigiously diverse group as measured at the species, family and ordinal levels, but the nervous system bears evidence of conservatism. The early acquisition of flight must have been a major factor in the diversification of body form. Arguments are presented that predator evasion was a primary factor in the origin of flight and that a conserved set of giant interneurons played a key element in the transition.

Animals↗