Tricky Morphology: A New Species of Chamaecrista (Leguminosae) Shows Strong Morphological Convergence Among Not Closely Related Species Found in Similar Habitat

Abstract— Plants from Brazilian campos rupestres usually present morphological strategies that allow them to survive in extreme environments. However, in Chamaecrista (Leguminosae, Caesalpinioideae), one of the most diverse genera in the campos rupestres, needle-like leaflets are rare. Reviewing the species that present such leaf morphology, we describe Chamaecrista acicularis, a new species from the Canastra Range, in the southwestern region of the state of Minas Gerais, Brazil. Phylogenetic analyses revealed that C. acicularis is not closely related to other quite similar needle-like leafleted species and that this trait evolved convergently. We also present comments on the phylogenetic relationships of needle-like leafleted species as well as the evolution of the leaflet amplitude, and a detailed description of C. acicularis alongside illustrations, photos, geographical distribution, a key to the needle-like leafleted species and taxonomic notes on similar species. Additionally, we expand the description of Chamaecrista strictifolia and present an informal conservation status for all needle-like leafleted species.

The limits of convergence: the roles of phylogeny and dietary ecology in shaping non-avian amniote crania

Cranial morphology is remarkably varied in living amniotes and the diversity of shapes is thought to correspond with feeding ecology, a relationship repeatedly demonstrated at smaller phylogenetic scales, but one that remains untested across amniote phylogeny. Using a combination of morphometric methods, we investigate the links between phylogenetic relationships, diet and skull shape in an expansive dataset of extant toothed amniotes: mammals, lepidosaurs and crocodylians. We find that both phylogeny and dietary ecology have statistically significant effects on cranial shape. The three major clades largely partition morphospace with limited overlap. Dietary generalists often occupy clade-specific central regions of morphospace. Some parallel changes in cranial shape occur in clades with distinct evolutionary histories but similar diets. However, members of a given clade often present distinct cranial shape solutions for a given diet, and the vast majority of species retain the unique aspects of their ancestral skull plan, underscoring the limits of morphological convergence due to ecology in amniotes. These data demonstrate that certain cranial shapes may provide functional advantages suited to particular dietary ecologies, but accounting for both phylogenetic history and ecology can provide a more nuanced approach to inferring the ecology and functional morphology of cryptic or extinct amniotes.

Phenotypic plasticity triggers rapid morphological convergence

Phenotypic convergence, the independent evolution of similar traits, is ubiquitous in nature, happening at all levels of biological organizations and in most kinds of living beings. Uncovering its mechanisms remains a fundamental goal in biology. Evolutionary theory considers that convergence emerges through independent genetic changes selected over long periods of time. We show in this study that convergence can also arise through phenotypic plasticity. We illustrate this idea by investigating how plasticity drives Moricandia arvensis, a mustard species displaying within-individual polyphenism in flowers, across the morphological space of the entire Brassicaceae family. By compiling the multidimensional floral phenotype, the phylogenetic relationships, and the pollination niche of over 3000 Brassicaceae species, we demonstrated that Moricandia arvensis exhibits a plastic-mediated within-individual floral disparity greater than that found not only between species but also between higher taxonomical levels such as genera and tribes. As a consequence of this divergence, M. arvensis moves outside the morphospace region occupied by its ancestors and close relatives, crosses into a new region where it encounters a different pollination niche and converges phenotypically with distant Brassicaceae lineages. Our study suggests that, by inducing phenotypes that explore simultaneously different regions of the morphological space, plasticity triggers rapid phenotypic convergence.

Hard to catch: experimental evidence supports evasive mimicry

Most research on aposematism has focused on chemically defended prey, but the signalling difficulty of capture remains poorly explored. Similar to classical Batesian and Müllerian mimicry related to distastefulness, such ‘evasive aposematism' may also lead to convergence in warning colours, known as evasive mimicry. A prime candidate group for evasive mimicry areAdelphabutterflies, which are agile insects and show remarkable colour pattern convergence. We tested the ability of naive blue tits to learn to avoid and generalizeAdelphawing patterns associated with the difficulty of capture and compared their response to that of birds that learned to associate the same wing patterns with distastefulness. Birds learned to avoid all wing patterns tested and generalized their aversion to other prey to some extent, but learning was faster with evasive prey compared to distasteful prey. Our results on generalization agree with longstanding observations of striking convergence in wing colour patterns amongAdelphaspecies, since, in our experiments, perfect mimics of evasive and distasteful models were always protected during generalization and suffered the lowest attack rate. Moreover, generalization on evasive prey was broader compared to that on distasteful prey. Our results suggest that being hard to catch may deter predators at least as effectively as distastefulness. This study provides empirical evidence for evasive mimicry, a potentially widespread but poorly understood form of morphological convergence driven by predator selection.

Myoglobin primary structure reveals multiple convergent transitions to semi-aquatic life in the world’s smallest mammalian divers

Identifying the phylogenomic underpinnings of specialized phenotypes that fueled transitions into new adaptive zones is central to evolutionary biology but is often confounded by a fragmentary fossil record, morphological convergence, and unresolved phylogenetic relationships. The speciose mammalian order Eulipotyphla (e.g., moles, shrews, hedgehogs, solenodons) combines an unusual diversity of semi-aquatic, semi-fossorial, and fossorial forms that arose from terrestrial forbearers, yet the ecomorphological pathways leading to these lifestyles have been disputed for a century and more, calling for novel approaches. Here we resolve previously intractable eulipotyphlan intra-family relationships and establish the net surface charge of the oxygen-storing muscle protein myoglobin-readily determined from its primary structure-as a molecular signature to trace ancient lifestyle transitions based on protein sequence alone. Our analyses confidently resolve fossorial habits having evolved twice in talpid moles and reveal five independent origins of a semi-aquatic lifestyle in the order housing the world’s smallest endothermic divers.