The causes of species richness patterns across space, time, and clades and the role of "ecological limits"

A major goal of research in ecology and evolution is to explain why species richness varies across habitats, regions, and clades. Recent reviews have argued that species richness patterns among regions and clades may be explained by "ecological limits" on diversity over time, which are said to offer an alternative explanation to those invoking speciation and extinction (diversification) and time. Further, it has been proposed that this hypothesis is best supported by failure to find a positive relationship between time (e.g., clade age) and species richness. Here, I critically review the evidence for these claims, and propose how we might better study the ecological and evolutionary origins of species richness patterns. In fact, ecological limits can only influence species richness in clades by influencing speciation and extinction, and so this new "alternative paradigm" is simply one facet of the traditional idea that ecology influences diversification. The only direct evidence for strict ecological limits on richness (i.e., constant diversity over time) is from the fossil record, but many studies cited as supporting this pattern do not, and there is evidence for increasing richness over time. Negative evidence for a relationship between clade age and richness among extant clades is not positive evidence for constant diversity over time, and many recent analyses finding no age-diversity relationship were biased to reach this conclusion. More comprehensive analyses strongly support a positive age-richness relationship. There is abundant evidence that both time and ecological influences on diversification rates are important drivers of both large-scale and small-scale species richness patterns. The major challenge for future studies is to understand the ecological and evolutionary mechanisms underpinning the relationships between time, dispersal, diversification, and species richness patterns.     

A PHYLOGENETIC PERSPECTIVE ON ELEVATIONAL SPECIES RICHNESS PATTERNS IN MIDDLE AMERICAN TREEFROGS: WHY SO FEW SPECIES IN LOWLAND TROPICAL RAINFORESTS?

Differences in species richness at different elevations are widespread and important for conservation, but the causes of these patterns remain poorly understood. Here, we use a phylogenetic perspective to address the evolutionary and biogeographic processes that underlie elevational diversity patterns within a region. We focus on a diverse but well-studied fauna of tropical amphibians, the hylid frogs of Middle America. Middle American treefrogs show a "hump-shaped" pattern of species richness (common in many organisms and regions), with the highest regional diversity at intermediate elevations. We reconstructed phylogenetic relationships among 138 species by combining new and published sequence data from 10 genes and then used this phylogeny to infer evolutionary rates and patterns. The high species richness of intermediate elevations seems to result from two factors. First, a tendency for montane clades to have higher rates of diversification. Second, the early colonization of montane regions, leaving less time for speciation to build up species richness in lowland regions (including tropical rainforests) that have been colonized more recently. This "time-for-speciation" effect may explain many diversity patterns and has important implications for conservation. The results also imply that local-scale environmental factors alone may be insufficient to explain the high species richness of lowland tropical rainforests, and that diversification rates are lower in earth's most species-rich biome.     

Does the colonization of new biogeographic regions influence the diversification and accumulation of clade richness among the Corvides (Aves: Passeriformes)?

Regional variation in clade richness can be vast, reflecting differences in the dynamics of historical dispersal and diversification among lineages. Although it has been proposed that dispersal into new biogeographic regions may facilitate diversification, to date there has been limited assessment of the importance of this process in the generation, and maintenance, of broad‐scale biodiversity gradients. To address this issue, we analytically derive biogeographic regions for a global radiation of passerine birds (the Corvides, c. 790 species) that are highly variable in the geographic and taxonomic distribution of species. Subsequently, we determine rates of historical dispersal between regions, the dynamics of diversification following regional colonization, and spatial variation in the distribution of species that differ in their rates of lineage diversification. The results of these analyses reveal spatiotemporal differences in the build‐up of lineages across regions. The number of regions occupied and the rate of transition between regions both predict family richness well, indicating that the accumulation of high clade richness is associated with repeated expansion into new geographic areas. However, only the largest family (the Corvidae) had significantly heightened rates of both speciation and regional transition, implying that repeated regional colonization is not a general mechanism promoting lineage diversification among the Corvides.     

Clade age and not diversification rate explains species richness among animal taxa

Animal taxa show remarkable variability in species richness across phylogenetic groups. Most explanations for this disparity postulate that taxa with more species have phenotypes or ecologies that cause higher diversification rates (i.e., higher speciation rates or lower extinction rates). Here we show that clade longevity, and not diversification rate, has primarily shaped patterns of species richness across major animal clades: more diverse taxa are older and thus have had more time to accumulate species. Diversification rates calculated from 163 species-level molecular phylogenies were highly consistent within and among three major animal phyla (Arthropoda, Chordata, Mollusca) and did not correlate with species richness. Clades with higher estimated diversification rates were younger, but species numbers increased with increasing clade age. A fossil-based data set also revealed a strong, positive relationship between total extant species richness and crown group age across the orders of insects and vertebrates. These findings do not negate the importance of ecology or phenotype in influencing diversification rates, but they do show that clade longevity is the dominant signal in major animal biodiversity patterns. Thus, some key innovations may have acted through fostering clade longevity and not by heightening diversification rate.     

Faster Speciation and Reduced Extinction in the Tropics Contribute to the Mammalian Latitudinal Diversity Gradient

The increase in species richness from the poles to the tropics, referred to as the latitudinal diversity gradient, is one of the most ubiquitous biodiversity patterns in the natural world. Although understanding how rates of speciation and extinction vary with latitude is central to explaining this pattern, such analyses have been impeded by the difficulty of estimating diversification rates associated with specific geographic locations. Here, we use a powerful phylogenetic approach and a nearly complete phylogeny of mammals to estimate speciation, extinction, and dispersal rates associated with the tropical and temperate biomes. Overall, speciation rates are higher, and extinction rates lower, in the tropics than in temperate regions. The diversity of the eight most species-rich mammalian orders (covering 92% of all mammals) peaks in the tropics, except that of the Lagomorpha (hares, rabbits, and pikas) reaching a maxima in northern-temperate regions. Latitudinal patterns in diversification rates are strikingly consistent with these diversity patterns, with peaks in species richness associated with low extinction rates (Primates and Lagomorpha), high speciation rates (Diprotodontia, Artiodactyla, and Soricomorpha), or both (Chiroptera and Rodentia). Rates of range expansion were typically higher from the tropics to the temperate regions than in the other direction, supporting the “out of the tropics” hypothesis whereby species originate in the tropics and disperse into higher latitudes. Overall, these results suggest that differences in diversification rates have played a major role in shaping the modern latitudinal diversity gradient in mammals, and illustrate the usefulness of recently developed phylogenetic approaches for understanding this famous yet mysterious pattern.     

Geographic range size, life history and rates of diversification in Australian mammals

Abstract What causes species richness to vary among different groups of organisms? Two hypotheses are that large geographical ranges and fast life history either reduce extinction rates or raise speciation rates, elevating a clade's rate of diversification. Here we present a comparative analysis of these hypotheses using data on the phylogenetic relationships, geographical ranges and life history of the terrestrial mammal fauna of Australia. By comparing species richness patterns to null models, we show that species are distributed nonrandomly among genera. Using sister‐clade comparisons to control for clade age, we then find that faster diversification is significantly associated with larger geographical ranges and larger litters, but there is no evidence for an effect of body size or age at first breeding on diversification rates. We believe the most likely explanation for these patterns is that larger litters and geographical ranges increase diversification rates because they buffer species from extinction. We also discuss the possibility that positive effects of litter size and range size on diversification rates result from elevated speciation rates.     

Diversification and biogeographic patterns in four island radiations of passerine birds

Declining diversification rates over time are a well-established evolutionary pattern, often interpreted as indicating initial rapid radiation with filling of ecological niche space. Here, we test the hypothesis that island radiations may show constant net diversification rates over time, due to continued expansion into new niche space in highly dispersive taxa. We investigate diversification patterns of four passerine bird families originating from the Indo-Pacific archipelagos, and link these to biogeographic patterns to provide independent indications of niche filling. We find a declining diversification rate for only one family, the Paradisaeidae (41 species). These are almost completely restricted to New Guinea, and have on average smaller species ranges and higher levels of species richness within grid cells than the other three families. In contrast, we cannot reject constant diversification rates for Campephagidae (93 species), Oriolidae (35 species), and Pachycephalidae (53 species), groups that have independently colonized neighboring archipelagos and continents. We propose that Paradisaeidae have reached the diversity limit imposed by their restricted distribution, whereas high dispersal and colonization success across the geologically dynamic Indo-Pacific archipelagos may have sustained high speciation rates for the other three families. Alternatively, increasing extinction rates may have obscured declining speciation rates in those three phylogenies.     

THE ROLE OF CLIMATIC TOLERANCES AND SEED TRAITS IN REDUCED EXTINCTION RATES OF TEMPERATE POLYGONACEAE

The latitudinal diversity gradient (LDG) is one of the most striking and consistent biodiversity patterns across taxonomic groups. We investigate the species richness gradient in the buckwheat family, Polygonaceae, which exhibits a reverse LDG and is, thus, decoupled from dominant gradients of energy and environmental stability that increase toward the tropics and confound mechanistic interpretations. We test competing age and evolutionary diversification hypotheses, which may explain the diversification of this plant family over the past 70 million years. Our analyses show that the age hypothesis, which posits that clade richness is positively correlated with the ecological and evolutionary time since clade origin, fails to explain the richness gradient observed in Polygonaceae. However, an evolutionary diversification hypothesis is highly supported, with diversification rates being 3.5 times higher in temperate clades compared to tropical clades. We demonstrate that differences in rates of speciation, migration, and molecular evolution insufficiently explain the observed patterns of differential diversification rates. We suggest that reduced extinction rates in temperate clades may be associated with adaptive responses to selection, through which seed morphology and climatic tolerances potentially act to minimize risk in temporally variable environments. Further study is needed to understand causal pathways among these traits and factors correlated with latitude.     

Does coevolution promote species richness in parasitic cuckoos?

Why some lineages have diversified into larger numbers of species than others is a fundamental but still relatively poorly understood aspect of the evolutionary process. Coevolution has been recognized as a potentially important engine of speciation, but has rarely been tested in a comparative framework. We use a comparative approach based on a complete phylogeny of all living cuckoos to test whether parasite–host coevolution is associated with patterns of cuckoo species richness. There are no clear differences between parental and parasitic cuckoos in the number of species per genus. However, a cladogenesis test shows that brood parasitism is associated with both significantly higher speciation and extinction rates. Furthermore, subspecies diversification rate estimates were over twice as high in parasitic cuckoos as in parental cuckoos. Among parasitic cuckoos, there is marked variation in the severity of the detrimental effects on host fitness; chicks of some cuckoo species are raised alongside the young of the host and others are more virulent, with the cuckoo chick ejecting or killing the eggs/young of the host. We show that cuckoos with a more virulent parasitic strategy have more recognized subspecies. In addition, cuckoo species with more recognized subspecies have more hosts. These results hold after controlling for confounding geographical effects such as range size and isolation in archipelagos. Although the power of our analyses is limited by the fact that brood parasitism evolved independently only three times in cuckoos, our results suggest that coevolutionary arms races with hosts have contributed to higher speciation and extinction rates in parasitic cuckoos.     

Regional differences in rates of plant speciation and molecular evolution: a comparison between eastern Asia and eastern North America

The eastern Asian (EAS)-eastern North American (ENA) floristic disjunction is one of the best-known biogeographic patterns in the Northern Hemisphere. Recent paleontological and molecular analyses have illuminated the origins of the biogeographic pattern, but subsequent diversification and evolution of the disjunct floras in each of the two continents after isolation remains poorly understood. Although similar in climate and floristic composition, EAS has twice as many species as ENA in genera occurring in both regions. Explaining such differences in species diversity between regions with similar environmental conditions (diversity anomalies) is an important goal of the study of the global patterns of biodiversity. We used a phylogenetic approach to compare rates of net speciation and molecular evolution between the two regions. We first identified EAS-ENA disjunct sister clades from ten genera (Asarum, Buckleya, Carpinus, Carya, Cornus, Hamamelis, Illicium, Panax, Stewartia, and Styrax) that represent diverse angiosperm lineages using phylogenetic analyses of ITS (internal transcribed spacer of nuclear ribosomal DNA) sequence data. Species richness and substitution rate of ITS between sister clades were compared. The results revealed a pattern of greater species diversity in the EAS counterparts. A positive relationship between species diversity and ITS substitution rate was also documented. These results suggest greater net speciation and accelerated molecular evolution in EAS. The data support the idea that a regional difference in net speciation rate related to topographic heterogeneity contributes to the diversity anomaly between EAS and ENA. The close relationship between rates of ITS evolution and species richness further suggests that species production may be directly linked to rate of nucleotide substitution.     

Host abundance,durability, basidiome form and phylogenetic isolation determine fungivore species richness

Species with close associations to a specific host species, such as parasites and phytophages, make immense contributions to biodiversity. Hence, factors determining the variation in species richness among hosts are a main focus of ecological research. Investigations of determining factors of fungivorous species among host species are still scarce. Based on ecological patterns of parasites and phytophages, we hypothesized that the species richness of tree‐fungus beetles of the family Ciidae (Coleoptera) would increase with increasing basidiome size, niche diversity of the growth form, durability, increasing abundance and decreasing phylogenetic isolation of the host fungus. Our generalized least‐squares model, controlled by host phylogeny, revealed that Ciidae species richness increases with host abundance, but decreases with host phylogenetic isolation. In contrast with our prediction, Ciidae species richness was higher in annual basidiomes than in perennials. Pileate basidiomes revealed higher species richness than resupinate and stipitate basidiomes, which may be interpreted as being a result of their higher host niche diversity. The importance of host abundance, measured on the landscape scale, corroborates that fungivore species richness among macrofungal hosts is determined by factors similar to those that determine parasite and phytophage species richness among their hosts. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 699–708.     

Speciation dynamics during the global radiation of extant bats

Species richness varies widely across extant clades, but the causes of this variation remain poorly understood. We investigate the role of diversification rate heterogeneity in shaping patterns of diversity across families of extant bats. To provide a robust framework for macroevolutionary inference, we assemble a time‐calibrated, species‐level phylogeny using a supermatrix of mitochondrial and nuclear sequence data. We analyze the phylogeny using a Bayesian method for modeling complex evolutionary dynamics. Surprisingly, we find that variation in family richness can largely be explained without invoking heterogeneous diversification dynamics. We document only a single well‐supported shift in diversification dynamics across bats, occurring at the base of the subfamily Stenodermatinae. Bat diversity is phylogenetically imbalanced, but—contrary to previous hypotheses—this pattern is unexplained by any simple patterns of diversification rate heterogeneity. This discordance may indicate that diversification dynamics are more complex than can be captured using the statistical tools available for modeling data at this scale. We infer that bats as a whole are almost entirely united into one macroevolutionary cohort, with decelerating speciation through time. There is also a significant relationship between clade age and richness, suggesting that global bat diversity may still be expanding.     

Explaining large-scale patterns of vertebrate diversity

The major clades of vertebrates differ dramatically in their current species richness, from 2 to more than 32 000 species each, but the causes of this variation remain poorly understood. For example, a previous study noted that vertebrate clades differ in their diversification rates, but did not explain why they differ. Using a time-calibrated phylogeny and phylogenetic comparative methods, I show that most variation in diversification rates among 12 major vertebrate clades has a simple ecological explanation: predominantly terrestrial clades (i.e. birds, mammals, and lizards and snakes) have higher net diversification rates than predominantly aquatic clades (i.e. amphibians, crocodilians, turtles and all fish clades). These differences in diversification rates are then strongly related to patterns of species richness. Habitat may be more important than other potential explanations for richness patterns in vertebrates (such as climate and metabolic rates) and may also help explain patterns of species richness in many other groups of organisms.     

Shifts in diversification rates and host jump frequencies shaped the diversity of host range among Sclerotiniaceae fungal plant pathogens

The range of hosts that a parasite can infect in nature is a trait determined by its own evolutionary history and that of its potential hosts. However, knowledge on host range diversity and evolution at the family level is often lacking. Here, we investigate host range variation and diversification trends within the Sclerotiniaceae, a family of Ascomycete fungi. Using a phylogenetic framework, we associate diversification rates, the frequency of host jump events and host range variation during the evolution of this family. Variations in diversification rate during the evolution of the Sclerotiniaceae define three major macro‐evolutionary regimes with contrasted proportions of species infecting a broad range of hosts. Host–parasite cophylogenetic analyses pointed towards parasite radiation on distant hosts long after host speciation (host jump or duplication events) as the dominant mode of association with plants in the Sclerotiniaceae. The intermediate macro‐evolutionary regime showed a low diversification rate, high frequency of duplication events and the highest proportion of broad host range species. Our findings suggest that the emergence of broad host range fungal pathogens results largely from host jumps, as previously reported for oomycete parasites, probably combined with low speciation rates. These results have important implications for our understanding of fungal parasites evolution and are of particular relevance for the durable management of disease epidemics.     

Can 'continuity indicator species' predict species richness or red-listed species of saproxylic beetles?

This study investigates the relationship between the abundance of wood-rotting fungus suggested as 'continuity indicator species' and environmental variables for the assemblage of saproxylic (wood-living) beetles associated with Fomitopsis pinicola fruiting bodies in a mature spruce forest in southeastern Norway. The presence of species thought to indicate continuity in old growth is one of the criteria used when finding and delineating small protected areas ('woodland key habitats') in Scandinavian forestry. Although it is clear that remnants of old-growth forest are important for many taxa, documentation as to which entities or species the indicator species indeed indicate is scarce. If stands with a continuous and unbroken input of dead wood have a unique assemblage of wood-rotting fungi, it seems relevant to ask if these stands also have a unique assemblage of rare saproxylic beetles. I find that the indicator species exhibit no significant correlations with beetle species richness or with the presence of red-listed saproxylic beetles as a group. The different characteristics of dead wood conditions are the most important environmental variables that explain both the species richness and the presence of red-listed beetles. Single-species analyses reveal contrasting relationships. The red-listed beetle Atomaria alpina shows a significant and positive association to the abundance of indicator species. Contrary, a group of three red-listed species with similar ecology in the family Cisidae exhibits a significant and negative association to indicator species abundance. This indicates that important patterns are concealed when considering general measures such as overall presence of red-listed beetles. Single-species studies are necessary in order to correctly understand how rare beetles respond to forestry activities and to develop a policy that can secure their continuing existence in the boreal forest.     

Speciation and diversification of parasite lineages: an analysis of congeneric parasite species in vertebrates

The evolutionary diversification of living organisms is a central research theme in evolutionary ecology, and yet it remains difficult to infer the action of evolutionary processes from patterns in the distribution of rates of diversification among related taxa. Using data from helminth parasite communities in 76 species of birds and 114 species of mammals, the influence of four factors that may either be associated with or modulate rates of parasite speciation were examined in a comparative analysis. Two measures of the relative number of congeneric parasite species per host species were used as indices of parasite diversification, and related to host body mass, host density, latitude, and whether the host is aquatic or terrestrial. The occurrence of congeneric parasites was not distributed randomly with respect to these factors. Aquatic bird species tended to harbour more congeneric parasites than terrestrial birds. Large-bodied mammal species, or those living at low latitudes, harboured more congeneric parasites than small-bodied mammals, or than those from higher latitudes. Host density had no apparent association with either measures of parasite diversification. These patterns, however, reflect only the present-day distribution of parasite diversification among host taxa, and not the evolutionary processes responsible for diversification, because the apparent effects of the factors investigated disappeared once corrections were made for host phylogeny. This indicates that features other than host body size, host density, latitude, and whether the habitat is terrestrial or aquatic, have been the key driving forces in the diversification of parasitic helminth lineages. This revised version was published online in July 2006 with corrections to the Cover Date.     

Environmental predictors of global parrot (Aves: Psittaciformes) species richness and phylogenetic diversity

Aim Spatial patterns of phylogenetic diversity (PD) aid our ability to discern diversification rate mechanisms underlying hypotheses for the large‐scale distribution of biodiversity. We develop a predictive framework for the way in which spatial patterns of PD vary with those of species richness, depending on the balance between speciation and extinction rates. Within this framework, diversification processes thought to underlie the productive energy, ambient energy, topographic variability and habitat variety hypotheses predict that gradients of increase in species richness will be associated with: (1) decreasing extinction rates where driven by productive energy, hence increasing relative PD (i.e. PD controlling for species richness, or PD_rel); (2) a similar positive relationship between ambient energy and PD_rel; (3) increasing speciation rates where driven by topographic variability, hence decreasing PD_rel; and (4) no consistent relationship between PD_rel and habitat variety when driven by the latter. We test these predictions using distributional data on parrots. Location Neotropical, Afrotropical, Indo‐Malayan and Australasian realms. Methods Spatial models were used to test the predictions. Results Globally, a positive association between productive energy and PD_rel confirms prediction (1). However, within realms, hump‐shaped relationships suggest the importance of decreasing extinction rates up to a threshold level of productive energy, and the increasing importance of speciation rates thereafter. Ambient energy is positively associated with PD_rel in Australasia, Indo‐Malaya, and globally, supporting prediction (2). However, this is driven by the coincidence of highest PD_rel in areas of high ambient energy and intermediate productive energy (i.e. in seasonal tropical environments), which may be characterized by relatively low speciation and extinction rates. In the Neotropics, increasing topographic variability is associated with decreasing PD_rel and increasing species richness, suggesting an increasing gradient of speciation, supporting prediction (3). Elsewhere, the signal of this mechanism may be obscured by collinearities with energy gradients. The lack of an overall relationship between habitat diversity and PD_rel confirms prediction (4). Main conclusions Spatial patterns of PD_rel in relation to environmental gradients may be sensitive to collinearities among those gradients. Nevertheless, patterns emerge which have implications for the relative importance of speciation and extinction processes in generating latitudinal diversity gradients.     

Time and environment explain the current richness distribution of non‐marine turtles worldwide

Ecological, historical, and evolutionary hypotheses are important to explain geographical diversity gradients in many clades, but few studies have combined them into a single analysis allowing a comparison of their relative importance. This study aimed to evaluate the relative importance of ecological, historical, and evolutionary hypotheses in explaining the current global distribution of non‐marine turtles, a group whose distribution patterns are still poorly explored. We used data from distribution range maps of 336 species of non‐marine turtles, environmental layers, and phylogeny to obtain richness estimates of these animals in 2° × 2° cells and predictors related to ecological, evolutionary and historical hypotheses driving richness patterns. Then we used a path analysis to evaluate direct and indirect effects of the predictors on turtle richness. Ancestral area reconstruction was also performed in order to evaluate the influence of time‐for‐speciation in the current diversity of the group. We found that environmental variables had the highest direct effects on non‐marine turtle richness, whereas diversification rates and area available in the last 55 million yr minimally influenced turtle distributions. We found evidence for the time‐for‐speciation effect, since regions colonized early were generally richer than recently colonized regions. In addition, regions with a high number of colonization events had a higher number of turtle species. Our results suggested that ecological processes may influence non‐marine turtle richness independent of diversification rates, but they are probably related to dispersal abilities. However, colonization time was also an important component that must be taken into account. Finally, our study provided additional support for the importance of ecological (climate and productivity) and historical (time‐for‐speciation and dispersal) processes in shaping current biodiversity patterns.     

Estimating diversification rates from phylogenetic information

Patterns of species richness reflect the balance between speciation and extinction over the evolutionary history of life. These processes are influenced by the size and geographical complexity of regions, conditions of the environment, and attributes of individuals and species. Diversity within clades also depends on age and thus the time available for accumulating species. Estimating rates of diversification is key to understanding how these factors have shaped patterns of species richness. Several approaches to calculating both relative and absolute rates of speciation and extinction within clades are based on phylogenetic reconstructions of evolutionary relationships. As the size and quality of phylogenies increases, these approaches will find broader application. However, phylogeny reconstruction fosters a perceptual bias of continual increase in species richness, and the analysis of primarily large clades produces a data selection bias. Recognizing these biases will encourage the development of more realistic models of diversification and the regulation of species richness.     

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

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.