Explaining global insect species richness: lessons from a decade of macroevolutionary entomology

Abstract

The last 10 years have seen more research on insect macroevolution than all the previous years combined. Here, I summarize and criticise the claims that have been made by comparative phylogenetic and fossil studies, and identify some future opportunities. We know the fossil record and phylogeny of insects much better than we did 10 years ago. We cannot simply ascribe the richness of insects, or their subtaxa, to either age or diversification rate. There is evidence that fossil family richness peaked much earlier than previously suspected. Phylogenetic evidence, however, suggests that species‐level net diversification rates are accelerating, though this is highly variable across taxa, implying ongoing changes in global taxonomic composition. Although there is evidence that wings and metamorphosis have had some macroevolutionary effects, the most definitive broad phylogenetic study does not suggest that they directly elevated net diversification of species. There is little evidence that insect body size influences net diversification rate. Compared to other phyla, arthropod richness, of which insects comprise the major part, is best explained by non‐marine habit, presence of parasitic lifestyles, a skeleton, vision, and dioecy. Herbivory cannot yet robustly be said to increase diversification over other diets across all insects: there are contrary analyses, and effects differ in different taxa. Many phylogenetic studies now document how it sometimes does: from co‐speciation, to diffuse co‐evolution with host shifting. The last decade has shown that climate change and biogeographic processes are likely important in generating or limiting insect diversification, but there is a need for greater statistical rigour in such studies. There is also a need to understand the validity of some widely used statistical methods better, and to make better use of the data and methods that exist. Macroevolutionary entomology could greatly benefit from online data integration platforms to facilitate analyses of broader scope.

Red Data Book invertebrates in a protected area of European Russia

“…Because of the immense lack of knowledge on the conservation status of invertebrates, any intensification in the study of these animals could lead to a remarkable increase in the number of known species and their presence in Protected Areas with possible description of new taxa (Anufriev 2016, Bouchard et al 2017, Mayhew 2018. Generalised data on the increase in the number of species known from the Mordovia State Nature Reserve between 1936 and 2018 shows that a plateu is far from being reached (Fig.…”

Multivariate similarity clustering analysis: a new method regarding biogeography and its application in global insects

“…Insecta is the largest classification group within Animalia (Lu 2019), and the observed species diversity and richness of insects is a major challenge to account for Earth's taxonomic composition (Mayhew 2018). Most insect data come from the usual groups in the usual parts of the world, and the accurate species number still remains poorly known with respect to current extinction risk (Stuart et al 2010;Collen et al 2012).…”

“…vicariance) events greatly influenced the insect diversity, especially many herbivorous clades (Nyman et al 2012;Kergoat et al 2016). Numerous studies have also been implemented to investigate the diversity-dependent diversification and interspecific interactions, with the effects of mating system and sexual selection relatively ignored in the last decades (Wiens 2017;Mayhew 2018). By using comparative phylogenetic and fossil information, the macroevolution and diversity of insects have been well explained by numerous studies.…”

Fundamental and specialized questions on host race formation and speciation – an introduction

“…The power of hostassociated differentiation in insect evolution is evident in how it generated some of the most species-rich groups. These mega-diverse radiations represent many different types of insect-host relationships (Mayhew, 2018). They can be adversarial in nature, such as the parasitoids and parasites with their hosts, and phytophagous insects with their host plant.…”