BACKGROUND: The evolutionary success of flowering plants is associated with the vast diversity of their reproductive structures. Despite recent progress in understanding angiosperm-wide trends of floral structure and evolution, a synthetic view of the diversity in seed form and function across angiosperms is lacking.
METHODS: Here we present a roadmap to synthesise the diversity of seed forms in extant angiosperms, relying on the morphospace concept, i.e. a mathematical representation which relates multiple traits and describes the realised morphologies. We provide recommendations on how to broaden the range of measurable traits beyond mass, by using key morphological traits representative of the embryo, endosperm, and seed coat but also fruit attributes (e.g., dehiscence, fleshiness). These key traits were used to construct and analyse a morphospace to detect evolutionary trends and gain insight into how morphological traits relate to seed functions. Finally, we outline challenges and future research directions, combining the morphospace with macroevolutionary comparative methods to underline the drivers that gave rise to the diversity of observed seed forms.
CONCLUSIONS: We conclude that this multidimensional approach has the potential, although still untapped, to improve our understanding of covariation among reproductive traits, and further elucidate angiosperm reproductive biology as a whole.

Interspecific variation in body size is one of the most popular topics in comparative studies. Despite recent advances, little is known about the patterns and processes behind the evolution of body size in insects. Here, we used a robust data set comprising all geometrid moth species occurring in Northern Europe to examine the evolutionary associations involving body size and several life-history traits under an explicitly phylogenetic framework. We provided new insights into the interactive effects of life-history traits on body size and evidence of correlated evolution. We further established the sequence of trait evolution linking body size with the life-history traits correlated with it. We found that most (but not all) of the studied life-history traits, to some extent, influenced interspecific variation in body size, but interactive effects were uncommon. Both bi- and multivariate phylogenetic analyses indicated that larger species tend to be nocturnal flyers, overwinter in the larval stage, feed on the foliage of trees rather than herbs, and have a generalist feeding behaviour. We found evidence of correlated evolution involving body size with overwintering stage, host-plant growth form, and dietary specialization. The examination of evolutionary transitions within the correlated evolution models signalled that overwintering as larvae commonly preceded the evolution of large sizes, as did feeding on tree foliage and the generalist feeding behaviour. By showing that both body size and all life-history traits correlated with it evolve at very slow rates, we caution against uncritical attempts to propose causal explanations for respective associations based on contemporary ecological settings.

As a potential anti-predatory defensive structure, the shell ornamentation of marine calcifiers is usually used to understand the macro coevolution of the interactions between predators and preys. Marine calcifiers\' shell ornamentation complexity is generally believed to vary negatively with latitude and water depth. In this paper, we explored the association between shell ornamentation and latitude/bathymetry using the latest global database of living brachiopods. We found that (1) ~59% of living brachiopods species are characterized by smooth shells and that (2) there is no statistically significant linear trend, either positive or negative, between the ornamentation index and latitudes nor with water depths. Both findings are puzzling for living brachiopods as they are sharply contrasted to the patterns of fossil brachiopods whereby the latter, especially Paleozoic brachiopods, are known to exhibit (1) a much greater ornamentation diversity and (2) (at least for the geological periods that have been studied) a linear latitudinal gradient of ornamentation complexity existed. The reasons why living brachiopods have such a high proportion of smooth or weakly ornamented shells and fail to demonstrate an unequivocal linear latitudinal ornamentation gradient were explored and are linked to a multitude of potential factors rather than uniquely only to the predation pressure. Among these, the most plausible factor seems to be the cryptic (refuge-type) habitats (e.g., deep waters, cold polar regions, and submarine rock caves) that living brachiopods have been adapted to due to their low metabolism, where predation pressure is low, allowing brachiopods to enact the predator avoidance strategy rather than having to manufacture robust shell ornamentation to survive in an otherwise highly engaged predator-prey global marine ecosystem.

The mitochondrial genomes of Bilateria are relatively conserved in their protein-coding, rRNA, and tRNA gene complement, but the order of these genes can range from very conserved to very variable depending on the taxon. The supposedly conserved gene order of Annelida has been used to support the placement of some taxa within Annelida. Recently, authors have cast doubts on the conserved nature of the annelid gene order. Various factors may influence gene order variability including, among others, increased substitution rates, base composition differences, structure of noncoding regions, parasitism, living in extreme habitats, short generation times, and biomineralization. However, these analyses were neither done systematically nor based on well-established reference trees. Several focused on only a few of these factors and biological factors were usually explored ad-hoc without rigorous testing or correlation analyses. Herein, we investigated the variability and evolution of the annelid gene order and the factors that potentially influenced its evolution, using a comprehensive and systematic approach. The analyses were based on 170 genomes, including 33 previously unrepresented species. Our analyses included 706 different molecular properties, 20 life-history and ecological traits, and a reference tree corresponding to recent improvements concerning the annelid tree. The results showed that the gene order with and without tRNAs is generally conserved. However, individual taxa exhibit higher degrees of variability. None of the analyzed life-history and ecological traits explained the observed variability across mitochondrial gene orders. In contrast, the combination and interaction of the best-predicting factors for substitution rate and base composition explained up to 30% of the observed variability. Accordingly, correlation analyses of different molecular properties of the mitochondrial genomes showed an intricate network of direct and indirect correlations between the different molecular factors. Hence, gene order evolution seems to be driven by molecular evolutionary aspects rather than by life history or ecology. On the other hand, variability of the gene order does not predict if a taxon is difficult to place in molecular phylogenetic reconstructions using sequence data or not. We also discuss the molecular properties of annelid mitochondrial genomes considering canonical views on gene evolution and potential reasons why the canonical views do not always fit to the observed patterns without making some adjustments. [Annelida; compositional biases; ecology; gene order; life history; macroevolution; mitochondrial genomes; substitution rates.].

The resource-use hypothesis, proposed by E.S. Vrba, states that habitat fragmentation caused by climatic oscillations would affect particularly biome specialists (species inhabiting only one biome), which might show higher speciation and extinction rates than biome generalists. If true, lineages would accumulate biome-specialist species. This effect would be particularly exacerbated for biomes located at the periphery of the global climatic conditions, namely, biomes that have high/low precipitation and high/low temperature such as rainforest (warm-humid), desert (warm-dry), steppe (cold-dry) and tundra (cold-humid). Here, we test these hypotheses in swallowtail butterflies, a clade with more than 570 species, covering all the continents but Antarctica, and all climatic conditions. Swallowtail butterflies are among the most studied insects, and they are a model group for evolutionary biology and ecology studies. Continental macroecological rules are normally tested using vertebrates, this means that there are fewer examples exploring terrestrial invertebrate patterns at global scale. Here, we compiled a large Geographic Information System database on swallowtail butterflies\' distribution maps and used the most complete time-calibrated phylogeny to quantify diversification rates (DRs). In this paper, we aim to answer the following questions: (1) Are there more biome-specialist swallowtail butterflies than biome generalists? (2) Is DR related to biome specialization? (3) If so, do swallowtail butterflies inhabiting extreme biomes show higher DRs? (4) What is the effect of species distribution area? Our results showed that swallowtail family presents a great number of biome specialists which showed substantially higher DRs compared to generalists. We also found that biome specialists are unevenly distributed across biomes. Overall, our results are consistent with the resource-use hypothesis, species climatic niche and biome fragmentation as key factors promoting isolation.

Phylogenetic comparative methods are often used to test functional relationships between traits. However, million-year macroevolutionary observational datasets cannot definitively prove causal links between traits-correlation does not equal causation and experimental manipulation over such timescales is impossible. Although this caveat is widely understood, it is less appreciated that different phylogenetic approaches imply different causal assumptions about the functional relationships of traits. To make meaningful inferences, it is critical that our statistical methods make biologically reasonable assumptions. Here we illustrate the importance of causal reasoning in comparative biology by examining a recent study by Avaria-Llautureo et al (2019). that tested for the evolutionary coupling of metabolic rate and body temperature across endotherms and found that these traits were unlinked through evolutionary time and that body temperatures were, on average, higher in the early Cenozoic than they are today. We argue that the causal assumptions embedded into their models made it impossible for them to test the relevant functional and evolutionary hypotheses. We reanalyze their data using more biologically appropriate models and find support for the exact opposite conclusions, corroborating previous evidence from physiology and paleontology. We highlight the vital need for causal thinking, even when experiments are impossible.

Adaptive landscapes are a common way of conceptualizing the phenotypic evolution of lineages across deep time. Although multiple approaches exist to implement this concept into operational models of trait evolution, inferring adaptive landscapes from comparative datasets remains challenging. Here, I explore the macroevolutionary dynamics of echinoid body size using data from over 5000 specimens and a phylogenetic framework incorporating a dense fossil sampling and spanning approximately 270 million years. Furthermore, I implement a novel approach of exploring alternative parameterizations of adaptive landscapes that succeeds in finding simpler, yet better-fitting models. Echinoid body size has been constrained to evolve within a single adaptive optimum for much of the clade\'s history. However, most of the morphological disparity of echinoids was generated by multiple regime shifts that drove the repeated evolution of miniaturized and gigantic forms. Events of body size innovation occurred predominantly in the Late Cretaceous and were followed by a drastic slowdown following the Cretaceous-Paleogene mass extinction. The discovery of these patterns is contingent upon directly sampling fossil taxa. The macroevolution of echinoid body size is therefore characterized by a late increase in disparity (likely linked to an expansion of ecospace), generated by active processes driving lineages toward extreme morphologies.

Anti-predator defences are typically regarded as relatively static signals that conceal prey or advertise their unprofitability. However, startle displays are complex performances that deter or confuse predators and can include a spectacular array of movements, colours and sounds. Yet, we do not fully understand the mechanisms by which they function, their evolutionary correlates, or the conditions under which they are performed and evolve. Here, we present, to our knowledge, the first phylogenetically controlled comparative analyses of startle displays including behavioural data, using praying mantises as a model system. We included 58 species that provide a good representation of mantis diversity and estimated the strength of phylogenetic signal in the presence and complexity of displays. We also tested hypotheses on potential evolutionary correlates, including primary defences and body size. We found that startle displays and morphological traits were phylogenetically conserved, whereas behavioural traits were highly labile. Surprisingly, body size was not correlated with display presence or complexity in phylogenetically controlled analyses. Species-rich clades were more likely to exhibit displays, suggesting that startle displays were probably involved in lineage diversification. We suggest that to further elucidate the conditions under which startle displays evolve, future work should include quantitative descriptions of multiple display components, habitat type, and predator communities. Understanding the evolution of startle displays is critical to our overall understanding of the theory behind predator-prey dynamics.

Is speciation generally a \"special time\" in morphological evolution, or are lineage-splitting events just \"more of the same\" where the end product happens to be two separate lineages? Data on evolutionary dynamics during anagenetic and cladogenetic events among closely related lineages within a clade are rare, but the fossil record of the bryozoan genus Metrarabdotos is considered a textbook example of a clade where speciation causes rapid evolutionary change against a backdrop of morphological stasis within lineages. Here, we point to some methodological and measurement theoretical issues in the original work on Metrarabdotos. We then reanalyze a subset of the original data that can be meaningfully investigated using quantitative statistical approaches similar to those used in the original studies. We consistently fail to find variation in the evolutionary process during within-lineage evolution compared with cladogenetic events: the rates of evolution, the strength of selection, and the directions traveled in multivariate morphospace are not different when comparing evolution within lineages and at speciation events in Metrarabdotos, and genetic drift cannot be excluded as a sufficient explanation for the morphological differentiation within lineages and during speciation. Although widely considered the best example of a punctuated mode of evolution, morphological divergence and speciation are not linked in Metrarabdotos.

Simpson\'s \"early burst\" model of adaptive radiation was intended to explain the early proliferation of morphological and functional variation in diversifying clades. Yet, despite much empirical testing, questions remain regarding its frequency across the tree of life. Here, we evaluate the support for an early burst model of adaptive radiation in 14 ecomorphological traits plus body mass for the extant mammalian order Carnivora and its constituent families. We find strong support for early bursts of dental evolution, suggesting a classic Simpsonian adaptive radiation along dietary resource axes. However, the signal of this early burst is not consistently recovered in analyses at the family level, where support for a variety of different models emerges. Furthermore, we find no evidence for early burst-like dynamics in size-related traits, and Bayesian analyses of evolutionary correlations corroborate a decoupling of size and dental evolution, driven in part by dietary specialization. Our results are consistent with the perspective that trait diversification unfolds hierarchically, with early bursts restricted to traits associated with higher level niches, such as macrohabitat use or dietary strategy, and thus with the origins of higher taxa. The lack of support for early burst adaptive radiation in previous phylogenetic studies may be a consequence of focusing on low-level niche traits (i.e., those associated with microhabitat use) in clades at shallow phylogenetic levels. A richer understanding of early burst adaptive radiation will require a renewed focus on functional traits and their evolution over higher level clades.