A quantitative comparison of the morphological diversity within beetles and true bugs: why immatures matter

Measuring biodiversity is more important than ever due to the ongoing global mass extinction event, often done by counting species. A species number cannot fully reflect the structure of diversity within an ecosystem. In Coleoptera, the group of beetles, the larvae strongly differ morphologically and ecologically from their corresponding adults. We evaluate the morphological diversity of adult and larval beetles from their body shape in comparison to adult and immature true bugs (Heteroptera). The latter have about 10 % of the species richness of beetles and have immatures which are morphologically similar to the corresponding adults. With an elliptic Fourier analysis of the overall body shape, we reconstructed and compared the morphospaces occupied by adult and larval beetles and adult and immature true bugs. The morphological diversity of immature beetles is significantly larger than that of adult beetles, within true bugs it is comparably small. Such potentially ecologically relevant differences can hence be detected by using quantitative morphology.