“Diet evolution and clade richness in Hexapoda: a phylogenetic study of higher taxa”

Posted on by Owen

James L. Rainford and Peter J. Mayhew

Phylogenetic study of sister group contrasts challenges diet and plant feeding as drivers of insect species richness

Plant and insect diversification: not as linked as we thought

The caterpillar of the light knot grass moth (Acronicta menyanthidis) belongs to the very large radiation of plant feeding Lepidoptera. However, many groups of plant-feeding insects are species-poor relative to their non-plant feeding relatives.
(Credit: Peter J. Mayhew)

Insects and flowering plants are two of the most diverse groups of organism on our planet. For a long time the richness of these two lineages has been regarded as linked, and plant-feeding insect groups considered unusually species rich when compared with their nearest relatives. In a new analysis, based on the most complete tree of insect relationships to date, researchers at the University of York have shown that there is not a simple relationship between insect diet and diversity: Many different types of diet can allow diversity to evolve, but when this happens is highly contingent the insect group in question. For example, among plant feeding groups, some radiations such as the butterflies and the weevils are massively diverse, while others, such as some groups of flies, number a mere dozen or so species.

Some specialized diets, such as ectoparasitism (insects feeding on vertebrate hosts), evolve rarely and act as evolutionary traps, from which other diets do not easily evolve, whilst others, such as predation and fungivory, evolve frequently and readily give rise to other dietary types. These findings also reveal general trends towards the origination of specialized diets, many of which involve close coevolution between insects and their animal or plant hosts, as well as providing a broad description of the history of diet evolution across the different insect orders. Thus this new analysis suggests that, rather than a simple predictable relationship between diet and diversification, insects instead show a rich variety of processes, where contingency and historical effects play a greater role in explaining the diversity of different dietary groups. Read the Article