Evolution of alternative male morphotypes in oxyurid nematodes: a case of convergence?

Male dimorphism has been reported across different taxa and is usually expressed as the coexistence of a larger morph with exaggerated male traits and a smaller one with reduced traits. The evolution and maintenance of male dimorphism are still poorly understood for several of the species in which it has been observed. Here, we analyse male dimorphism in several species of reptile parasitic nematodes of the genus Spauligodon, in which a major male morph (exaggerated morph), which presents the traditional male morphological traits reported for this taxon, coexists with a minor morph with reduced morphological traits (i.e. reduced genital papillae) resembling more closely the males of the sister genus Skrjabinodon than Spauligodon major males. Because of the level of uncertainty in the results of ancestral state reconstruction, it is unclear if the existence of male dimorphism in this group represents independent instances of convergent evolution or an ancestral trait lost multiple times. Also, although the number of major males per host was positively correlated with the number of females, the same did not hold true for minor males, whose presence was not associated with any other ecological factor. Nevertheless, the existence of male dimorphism in Spauligodon nematodes is tentatively interpreted as resulting from alternative reproductive tactics, with differences in presence and number of individuals as indicators of differences in fitness, with the lower numbers of minor males per host likely maintained by negative frequency‐dependent selection.     

Why use population entropy? It determines the rate of convergence

Summary The population entropy introduced by Demetrius is shown to have a precise dynamical meaning as a measure of convergence rate to the stable age distribution. First the Leslie population model is transformed exactly into a Markov chain on a state space of age-classes. Next the dynamics of convergence from a nonequilibrium state to the stable state are analyzed. The results provide the first clear biological reason why entropy is a broadly useful population statistic.     

Phenotypic similarity in sympatric crow species: Evidence of social convergence?

Crows, rooks, and ravens (Corvus spp.) display marked morphological and voice similarities that have been hypothesized to stem from competitive interactions, as a case of nonaposematic mimicry. Here, I test predictions of the mimicry hypothesis at the macrovolutionary scale, examining whether species morphological and acoustic traits covary with those of coexisting congeners, and whether phenotypic similarity has facilitated the coexistence of related species after secondary contact. Body size and the temporal patterns of the commonest call display high levels of similarity among sympatric species, even after controlling for the effect of shared climate and habitat, and phylogenetic constraints in the production of variation. When sister species differed in these acoustic and morphological traits, their transition to secondary sympatry was delayed relative to those with more similar traits. No similarity was found in the sexual call of crows, suggesting that convergence occurs only when function does not favour maintenance of species‐specific traits. Crow similarities in morphological and acoustic features may therefore be associated with coevolving interactions with congeners, in line with a broad array of studies documenting convergence among species that interact aggressively or forage communally.     

Signal convergence in fruits: a result of selection by frugivores?

The Dispersal Syndrome hypothesis remains contentious, stating that apparently nonrandom associations of fruit characteristics result from selection by seed dispersers. We examine a key assumption under this hypothesis, i.e. that fruit traits can be used as reliable signals by frugivores. We first test this assumption by looking at whether fruit colour allows birds and primates to distinguish between fruits commonly dispersed by birds or primates. Second, we test whether the colours of fruits dispersed by primates are more contrasting to primates than the colours of bird‐dispersed fruits, expected if fruit colour is an adaptation to facilitate the detection by seed dispersers. Third, we test whether fruit colour has converged in unrelated plant species dispersed by similar frugivores. We use vision models based on peak sensitivities of birds’ and primates’ cone cells. We base our analyses on the visual systems of two types of birds (violet and ultraviolet based) and three types of primates (trichromatic primates from the Old and the New Worlds, and a dichromatic New World monkey). Using a Discriminant Function Analysis, we find that all frugivore groups can reliably discriminate between bird‐ and primate‐dispersed fruits. Fruit colour can be a reliable signal to different seed dispersers. However, the colours of primate‐dispersed fruits are less contrasting to primates than those of bird‐dispersed fruits. Fruit colour convergence in unrelated plants is independent of phylogeny and can be better explained by disperser type, which supports the hypothesis that frugivores are important in fruit evolution. We discuss adaptive and nonadaptive hypotheses that can potentially explain the pattern we found.     

Multiple origins of endosymbiosis within the Enterobacteriaceae (γ-Proteobacteria): convergence of complex phylogenetic approaches

Background

Protein interactions control the regulatory networks underlying developmental processes. The understanding of developmental complexity will, therefore, require the characterization of protein interactions within their proper environment. The bimolecular fluorescence complementation (BiFC) technology offers this possibility as it enables the direct visualization of protein interactions in living cells. However, its potential has rarely been applied in embryos of animal model organisms and was only performed under transient protein expression levels.

Results

Using a Hox protein partnership as a test case, we investigated the suitability of BiFC for the study of protein interactions in the living Drosophila embryo. Importantly, all BiFC parameters were established with constructs that were stably expressed under the control of endogenous promoters. Under these physiological conditions, we showed that BiFC is specific and sensitive enough to analyse dynamic protein interactions. We next used BiFC in a candidate interaction screen, which led to the identification of several Hox protein partners.

Conclusion

Our results establish the general suitability of BiFC for revealing and studying protein interactions in their physiological context during the rapid course of Drosophila embryonic development.     

Expression of collier in the premandibular segment of myriapods: support for the traditional Atelocerata concept or a case of convergence?

Background  

A recent study on expression and function of the ortholog of the Drosophila collier (col) gene in various arthropods including insects, crustaceans and chelicerates suggested a de novo function of col in the development of the appendage-less intercalary segment of insects. However, this assumption was made on the background of the now widely-accepted Pancrustacea hypothesis that hexapods represent an in-group of the crustaceans. It was therefore assumed that the expression of col in myriapods would reflect the ancestral state like in crustaceans and chelicerates, i.e. absence from the premandibular/intercalary segment and hence no function in its formation.     

Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

Convergent morphologies are thought to indicate functional similarity, arising because of a limited number of evolutionary or developmental pathways. Extant taxa displaying convergent morphologies are used as analogues to assess function in extinct taxa with similar characteristics. However, functional studies of extant taxa have shown that functional similarity can arise from differing morphologies, calling into question the paradigm that form and function are closely related. We test the hypothesis that convergent skeletal morphology indicates functional similarity in the fossil record using ornithischian dinosaurs. The rare transition from bipedality to quadrupedality occurred at least three times independently in this clade, resulting in a suite of convergent osteological characteristics. We use homology rather than analogy to provide an independent line of evidence about function, reconstructing soft tissues using the extant phylogenetic bracket and applying biomechanical concepts to produce qualitative assessments of muscle leverage. We also optimize character changes to investigate the sequence of character acquisition. Different lineages of quadrupedal ornithischian dinosaur stood and walked differently from each other, falsifying the hypothesis that osteological convergence indicates functional similarity. The acquisition of features correlated with quadrupedalism generally occurs in the same order in each clade, suggesting underlying developmental mechanisms that act as evolutionary constraints.     

Local sleep homeostasis in the avian brain: convergence of sleep function in mammals and birds?

The function of the brain activity that defines slow wave sleep (SWS) and rapid eye movement (REM) sleep in mammals is unknown. During SWS, the level of electroencephalogram slow wave activity (SWA or 0.5-4.5 Hz power density) increases and decreases as a function of prior time spent awake and asleep, respectively. Such dynamics occur in response to waking brain use, as SWA increases locally in brain regions used more extensively during prior wakefulness. Thus, SWA is thought to reflect homeostatically regulated processes potentially tied to maintaining optimal brain functioning. Interestingly, birds also engage in SWS and REM sleep, a similarity that arose via convergent evolution, as sleeping reptiles and amphibians do not show similar brain activity. Although birds deprived of sleep show global increases in SWA during subsequent sleep, it is unclear whether avian sleep is likewise regulated locally. Here, we provide, to our knowledge, the first electrophysiological evidence for local sleep homeostasis in the avian brain. After staying awake watching David Attenborough's The Life of Birds with only one eye, SWA and the slope of slow waves (a purported marker of synaptic strength) increased only in the hyperpallium--a primary visual processing region--neurologically connected to the stimulated eye. Asymmetries were specific to the hyperpallium, as the non-visual mesopallium showed a symmetric increase in SWA and wave slope. Thus, hypotheses for the function of mammalian SWS that rely on local sleep homeostasis may apply also to birds.     

Pollen and sperm heteromorphism: convergence across kingdoms?

Sperm competition theory predicts that males should produce many, similar sperm. However, in some species of animals and plants, males exhibit a heteromorphism that results in the production of at least two different types of sperm or pollen grains. In animals, sperm heteromorphism typically corresponds to the production of one fertile morph and one (or more) sterile morph(s), whereas in plants two or more pollen morphs (one of which can be either sterile or fertile) are produced in all flowers but sometimes in different anthers. Heteromorphism has arisen independently several times across phyla and at different phylogenetic levels. Here, we compare and contrast sperm and pollen heteromorphism and discuss the evolutionary hypotheses suggested to explain heteromorphism in these taxa. These hypotheses include facilitation, nutritive contribution, blocking, cheap filler, sperm flushing or killing for animals; outcrossing and precise cross-pollen transfer or bet-hedging strategy for plants; cryptic female choice for both. We conclude that heteromorphism in the two phyla is most likely linked to a general evolutionary response to sexual selection, either to increase one male's sperm or pollen success in competition with other males, or mediate male/female interactions. Therefore, although sperm and pollen are not homologous, we suggest that heteromorphism represents an example of convergence across kingdoms.     

Morphological evolution and changes in foraging behaviour of island and mainland populations of Blue Tit (Parus caeruleus) — a test of convergence and ecomorphological hypotheses

Summary We study the leg morphology and feeding postures of two subspecies of the Blue Tit (Parus caeruleus; Tenerife island and the Iberian Peninsula) and the Coal Tit (Parus ater; Iberian Peninsula). We search for evidence supporting the hypothesis of convergent evolution in morphological and ecological traits and we discuss the role of ecomorphological hypotheses as predictors of foraging differences at the intraspecific level. To overcome the problems introduced by environmental characteristics not related to locomotion and competition, we make observations under controlled situations to manage food quality and food access. We determine that the island Blue Tit has a longer tarsometatarsus, larger foot span and a more proximal insertion of the tibialis cranialis muscle (flexor of the tarsometatarsus) than the mainland Blue Tit. These morphological differences are consistent with the more frequent use of hanging and clinging head-up postures by the Iberian Blue Tit. Several ecomorphological hypotheses obtained at the interspecific level with other taxa, have proved to be of high predictive value for explaining ecological differences considering morphological evolution. The Tenerife Blue Tit and the Iberian Coal Tit clearly show close convergence in both feeding postures and leg structure, although some differences in morphology were found between these two species. Convergence in foraging methods between the island Blue Tit and the mainland Coal Tit can be explained without considering current interspecific competition as a determinant of niche space.     

AWTY (are we there yet?): a system for graphical exploration of MCMC convergence in Bayesian phylogenetics

A key element to a successful Markov chain Monte Carlo (MCMC) inference is the programming and run performance of the Markov chain. However, the explicit use of quality assessments of the MCMC simulations-convergence diagnostics-in phylogenetics is still uncommon. Here, we present a simple tool that uses the output from MCMC simulations and visualizes a number of properties of primary interest in a Bayesian phylogenetic analysis, such as convergence rates of posterior split probabilities and branch lengths. Graphical exploration of the output from phylogenetic MCMC simulations gives intuitive and often crucial information on the success and reliability of the analysis. The tool presented here complements convergence diagnostics already available in other software packages primarily designed for other applications of MCMC. Importantly, the common practice of using trace-plots of a single parameter or summary statistic, such as the likelihood score of sampled trees, can be misleading for assessing the success of a phylogenetic MCMC simulation. AVAILABILITY: The program is available as source under the GNU General Public License and as a web application at http://ceb.scs.fsu.edu/awty.     

A paradox of leaf-trait convergence: why is leaf nitrogen concentration higher in species with higher photosynthetic capacity?

It is well known that leaf photosynthesis per unit dry mass (A_mass) is positively correlated with nitrogen concentration (N_mass) across naturally growing plants. In this article we show that this relationship is paradoxical because, if other traits are identical among species, plants with a higher A_mass should have a lower N_mass, because of dilution by the assimilated carbon. To find a factor to overcome the dilution effect, we analyze the N_mass–A_mass relationship using simple mathematical models and literature data. We propose two equations derived from plant-growth models. Model prediction is compared with the data set of leaf trait spectrum obtained on a global scale. The model predicts that plants with a higher A_mass should have a higher specific nitrogen absorption rate in roots (SAR), less biomass allocation to leaves, and/or greater nitrogen allocation to leaves. From the literature survey, SAR is suggested as the most likely factor. If SAR is the sole factor maintaining the positive relationship between N_mass and A_mass, the variation in SAR is predicted to be much greater than that in A_mass; given that A_mass varies 130-fold, SAR may vary more than 2000-fold. We predict that there is coordination between leaf and root activities among species on a global scale. Kouki Hikosaka is the recipient of the BSJ Award for Young Scientist, 2006.     

On the evolution of protein folds: are similar motifs in different protein folds the result of convergence, insertion, or relics of an ancient peptide world?

This paper presents and discusses evidence suggesting how the diversity of domain folds in existence today might have evolved from peptide ancestors. We apply a structure similarity detection method to detect instances where localized regions of different protein folds contain highly similar sequences and structures. Results of performing an all-on-all comparison of known structures are described and compared with other recently published findings. The numerous instances of local sequence and structure similarities within different protein folds, together with evidence from proteins containing sequence and structure repeats, argues in favor of the evolution of modern single polypeptide domains from ancient short peptide ancestors (antecedent domain segments (ADSs)). In this model, ancient protein structures were formed by self-assembling aggregates of short polypeptides. Subsequently, and perhaps concomitantly with the evolution of higher fidelity DNA replication and repair systems, single polypeptide domains arose from the fusion of ADSs genes. Thus modern protein domains may have a polyphyletic origin.     

Self-incompatibility RNases from three plant families: homology or convergence?

In the Rosaceae, Scrophulariaceae, and Solanaceae, the stylar product of the self-incompatibility (S-) locus is an RNase. Using protein sequence data from 34 RNase genes (three fungal RNases, seven angiosperm non-S RNases, 11 Rosaceae S-alleles, three Scrophulariaceae S-alleles, and ten Solanaceae S-alleles) we reconstructed the genealogy of angiosperm RNases using the neighbor joining method and two distance metrics in order to assess whether use of S-RNases in these families is the result of homology or convergence. Four monophyletic groups of angiosperm RNases were found: the S-RNases of each of the three families and a group comprising most of the angiosperm non-S RNases. The S-RNases of the Scrophulariaceae and Solanaceae were found to be homologous but strong inference concerning the homology or convergence of S-RNases from the Rosaceae with those of the other families was not possible because of uncertain placement of both the root and two of the angiosperm non-S RNases. The most recent common ancestor of the Rosaceae and both the Scrophulariaceae and Solanaceae is shared by ~80% of dicot families. If the -RNases of the Rosaceae are homologous to those of the Scrophulariaceae and Solanaceae, then many other dicot families might be expected to share RNases as the mechanism of gametophytic self-incompatibility.     

Herfindahl–Hirschman Index based performance analysis on the convergence development

The converging performance of culture industry and financial industry in Beijing is an essential method to transform the way of Beijing economic development and promote culture industry into an economic pillar industry of Beijing. Based on this, this paper starts from the convergence status quo of culture industry and finance industry in Beijing, adopts Herfindahl–Hirschman Index (HHI) and input–output analysis to respectively study the converging degree between them. The results are that the converging degree of them is not high, the financial contribution to the industry convergence is not enough and the converging performance is far from expectations for government. In conclusion, this paper puts forward some policy suggestions to improve the convergence of culture industry and finance industry in Beijing.     

Striking case of convergence — Alleged marine gastropods in Cretaceous Burmese amber are terrestrial cyclophoroids. Comment on Yu et al.

Yu et al. (2019) recently described two new species of gastropods from the Cretaceous Burmese amber and attributed them to the marine family Epitoniidae. A close inspection of the images provided by Yu et al. indicates however that the species in question do not belong to that family or any marine gastropod group. In contrast, the two species are attributed here to the terrestrial operculate family Pupinidae (Cyclophoroidea) and tentatively to the genus Pseudopomatias. We briefly review the fossil record of the Cyclophoroidea and Pupinidae and discuss implications of the present revision. After all, Pseudopomatias? lyui (Yu, Wang and Jarzembowski, 2019) and P.? zhuoi (Yu, Wang and Jarzembowski, 2019) belong to the oldest members of the Pupinidae.     

Interspecific sexual attraction because of convergence in warning colouration: is there a conflict between natural and sexual selection in mimetic species?

When species converge in their colour patterns because of mimicry, and those patterns are also used in mate recognition, there is a probability of conflicting selection pressures. Closely related species that mimic one another are particularly likely to face such confusion because of similarities in their courtship behaviour and ecology. We conducted experiments in greenhouse conditions to study interspecific attraction between two mimetic butterfly species, Heliconius erato and Heliconius melpomene. Both species spent considerable time approaching and courting females of the co-mimic species. Experiments using wing models demonstrated the importance of colour pattern in this interspecific attraction. Although males of H. melpomene were attracted to their co-mimics as much as to their own females, H. erato males were more efficient at distinguishing conspecifics, possibly using wing odours. Although preliminary, these results suggest that the use of additional cues may have evolved in H. erato to reduce the cost of convergence in visual signals with H. melpomene. Overall, our results showed that there might be a cost of mimetic convergence because of a reduction in the efficiency of species recognition. Such cost may contribute to explain the apparently stable diversity in Müllerian mimetic patterns in many tropical butterfly assemblages.