Competition and phylogeny determine community structure in Müllerian co-mimics

Does coevolution in refugia drive mimicry in bumble bees? Insights from a South Asian mimicry group

Müllerian mimicry was proposed to be an example of a coevolved mutualism promoted by population isolation in glacial refugia. This, however, has not been well supported in butterfly models. Here, we use genomic data to test this theory while examining the population genetics behind mimetic diversification in a pair of co-mimetic bumble bees, Bombus breviceps Smith and Bombus trifasciatus Smith. In both lineages, populations were structured by geography but not as much by color pattern, suggesting sharing of color alleles across regions of restricted gene flow and formation of mimicry complexes in the absence of genetic differentiation. Demographic analyses showed mismatches between historical effective population size changes and glacial cycles, and niche modeling revealed only mild habitat retraction during glaciation. Moreover, mimetic subpopulations of the same color form in the two lineages only in some cases exhibit similar population history and genetic divergence. Therefore, the current study supports a more complex history in this comimicry than a simple refugium-coevolution model.

Convergent and environmentally associated chromatic polymorphism in Bryconops Kner, 1858 (Ostariophysi: Characiformes: Iguanodectidae)

Bryconops Kner, 1858, includes two well defined subgenera based on morphological evidence, with each containing at least one species (B. (Bryconops) caudomaculatus and B. (Creatochanes) melanurus) with a very wide distribution, within which regional populations present color variations. To test if phenotypic variation is related to cladogenetic events, we performed tests for phylogenetic independence and determined the strength of convergence for color characters in relation to water type, as the variation between clear, black and white waters is considered to be one of the major driving forces in the evolution of Amazonian fishes. Color characters for fins above the median line of the body were generally found to be independent from phylogeny and the Wheatsheaf test strongly supports convergence of the dorsal fin color between populations of species in the same type of water, with a similar trend suggested for the color of the dorsal lobe of the caudal fin. This means that simple color characters cannot necessarily be relied upon for taxonomic revisions of the genus as local phenotypic variants may represent environmentally determined plasticity or convergent evolution. Further studies are required to determine the validity of these characters.

How to Survive a (Juvenile) Piranha Attack: An Integrative Approach to Evaluating Predator Performance

Figures

Cory cat panel figureDrawing of bite force measuring equipment and indentation rig Pygocentrus nattereri jaw muscle morphology and skull anatomyBox plot grid of number of Pygocentrus nattereri bites before puncture along different body regions of Corydoras trilineatus during feeding trials resultsDrawing of color-coded Corydoras trilineatus with attack frequencies and average bites until puncture by Pygocentrus nattereriBox plot of average voluntary juvenile Pygocentrus nattereri bite forces to standard lengthPanel of linear ordinary least-squares regressions of Pygocentrus nattereri bite force to adductor mandibulae mass, standard length, and body massOrdinary least-squares regressions of voluntary bites to restrained bites of Pygocentrus nattereriPanel of indentation tests for intact and removed Corydoras trilineatus scutesPanel of indentation tests for Corydoras trilineatus body region.

Synopsis

There is an evolutionary arms race between predators and prey. In aquatic environments, predatory fishes often use sharp teeth, powerful bites, and/or streamlined bodies to help capture their prey quickly and efficiently. Conversely, prey are often equipped with antipredator adaptations including: scaly armor, sharp spines, and/or toxic secretions. This study focused on the predator-prey interactions between the armored threestripe cory catfish (Corydoras trilineatus) and juvenile red-bellied piranha (Pygocentrus nattereri). Specifically, we investigated how resistant cory catfish armor is to a range of natural and theoretical piranha bite forces and how often this protection translated to survival from predator attacks by Corydoras. We measured the bite force and jaw functional morphology of P. nattereri, the puncture resistance of defensive scutes in C. trilineatus, and the in situ predatory interactions between the two. The adductor mandibulae muscle in juvenile P. nattereri is robust and delivers an average bite force of 1.03 N and maximum bite force of 9.71 N, yet its prey, C. trilineatus, survived 37% of confirmed bites without any damage. The C. trilineatus armor withstood an average of nine bites before puncture by P. nattereri. Predation was successful only when piranhas bit unarmored areas of the body, at the opercular opening and at the caudal peduncle. This study used an integrative approach to understand the outcomes of predator-prey interactions by evaluating the link between morphology and feeding behavior. We found that juvenile P. nattereri rarely used a maximal bite force and displayed a net predation success rate on par with other adult vertebrates. Conversely, C. trilineatus successfully avoided predation by orienting predator attacks toward their resilient, axial armor and behavioral strategies that reduced the predator's ability to bite in less armored regions of the body.

Mutualistic interactions shape global spatial congruence and climatic niche evolution in Neotropical mimetic butterflies

Understanding the mechanisms underlying species distributions and coexistence is both a priority and a challenge for biodiversity hotspots such as the Neotropics. Here, we highlight that Müllerian mimicry, where defended prey species display similar warning signals, is key to the maintenance of biodiversity in the c. 400 species of the Neotropical butterfly tribe Ithomiini (Nymphalidae: Danainae). We show that mimicry drives large-scale spatial association among phenotypically similar species, providing new empirical evidence for the validity of Müller's model at a macroecological scale. Additionally, we show that mimetic interactions drive the evolutionary convergence of species climatic niche, thereby strengthening the co-occurrence of co-mimetic species. This study provides new insights into the importance of mutualistic interactions in shaping both niche evolution and species assemblages at large spatial scales. Critically, in the context of climate change, our results highlight the vulnerability to extinction cascades of such adaptively assembled communities tied by positive interactions.

Editorial overview: Eco-evolutionary dynamics in microbiology comes of age

The intimate linkage of ecology and evolution is central to our understanding of biodiversity. The traditional perspective was to separate these fields based on timescales, but rapid, contemporary evolution is widely accepted and perhaps even more so in microbial systems. The study of eco-evolutionary dynamics is advancing at great pace and microorganisms are at the forefront of emerging paradigms, driven by conceptual and technological advances, such that we can move beyond the widely studied eco to evo aspects of the field and develop our understanding of how microorganisms shape virtually all processes on the planet (evo to eco).

Comparative analysis of the mitogenomes of two Corydoras (Siluriformes, Loricarioidei) with nine known Corydoras, and a phylogenetic analysis of Loricarioidei

Corydoras is a speciose catfish genus from South America with widely investigated phylogenetic and evolutionary relationships. The complete mitogenomes of C. aeneus and C. paleatus were sequenced, assembled, and annotated using next-generation sequencing. The genome arrangements, gene contents, genome structures, base compositions, evolutionary features, codon usage, and tRNA structures of the two mitogenomes were compared and analyzed with nine published mitogenomes of Corydoras. Phylogenetic analysis was performed using concatenated nucleotide sequences with 13 protein-coding genes and two rRNAs with 44 mitogenomes of Siluriformes. These results provide information on the mitogenomes of eleven Corydoras species and evolutionary relationships within the suborder Loricarioidei, which may be applicable for further phylogenetic and taxonomic studies on Siluriformes and Loricarioidei.

Science and hobby joining forces for the discovery of three new Corydoras (Siluriformes: Callichthyidae) from the rio Tapajós basin, Brazil, with comments on Corydoras sp. CW111

Abstract An expedition crowdfunded by aquarists to a region of the Brazilian state of Pará drained by the Tapajós and Xingu river basins resulted in the capture of five species of Corydoras from the rio Jamanxim basin, a tributary to the rio Tapajós, of which three could be confirmed as new and described herein. The new species can be promptly diagnosed from their congeners by the combination of features related to color pattern and osteology. Considering the gathered information on color patterns and morphology plus field observations, the new species are considered to compose two distinct Müllerian mimicry rings, with two of them forming a mimetic pair, while the third one forms a pair with a fourth non-identified species captured in the same expedition. An identification key to the species of Corydoras from the rio Tapajós basin is also provided.

Transposable element annotation in non-model species: The benefits of species-specific repeat libraries using semi-automated EDTA and DeepTE de novo pipelines

Transposable elements (TEs) are significant genomic components which can be detected either through sequence homology against existing databases or de novo, with the latter potentially reducing the risk of underestimating TE abundance. Here, we describe the semi-automated generation of a de novo TE library using the newly developed EDTA pipeline and DeepTE classifier in a non-model teleost (Corydoras fulleri). Using both genomic and transcriptomic data, we assess this de novo pipeline's performance across four TE based metrics: (i) abundance, (ii) composition, (iii) fragmentation, and (iv) age distributions. We then compare the results to those found when using a curated teleost library (Danio rerio). We identify quantitative differences in these metrics and highlight how TE library choice can have major impacts on TE-based estimates in non-model species.

Corydoras fulleri (Siluriformes: Callichthyidae), a new catfish species from the rio Madeira basin, Peru

A new long-snouted Corydoras species is described from two tributaries of the río Manuripe and a tributary of the río Madre de Dios, rio Madeira basin, Peru. Corydoras fulleri can be distinguished from its congeners by having the following features: (a) branch of the temporal sensory canal at sphenotic, which gives rise to the supraorbital canal, with two pores; (b) upper tooth plate of branchial arch with three series of teeth; (c) area at the corner of the mouth, ventral to the maxillary barbel, with a small fleshy flap; (d) two moderate-sized dark-brown or black blotches on caudal-fin base, one on its lateral portion and another one on its dorsal portion, blotches variably diffuse and/or fused with each other; (e) absence of a dark-brown or black stripe transversally crossing the orbit; (f) a longitudinal dark-brown or black stripe on the postdorsal region of flank midline, variably fused with the lateral peduncular blotch, some specimens with slender, longitudinally elongated, dark-brown or black blotch on flank midline, forming a dash-like marking, stripe or dash-like blotch diffuse in some specimens; and (g) region around dorsal-fin origin generally lacking dark brown or black blotch, or displaying diffuse blotch.

Why aren't warning signals everywhere? On the prevalence of aposematism and mimicry in communities

Warning signals are a striking example of natural selection present in almost every ecological community - from Nordic meadows to tropical rainforests, defended prey species and their mimics ward off potential predators before they attack. Yet despite the wide distribution of warning signals, they are relatively scarce as a proportion of the total prey available, and more so in some biomes than others. Classically, warning signals are thought to be governed by positive density-dependent selection, i.e. they succeed better when they are more common. Therefore, after surmounting this initial barrier to their evolution, it is puzzling that they remain uncommon on the scale of the community. Here, we explore factors likely to determine the prevalence of warning signals in prey assemblages. These factors include the nature of prey defences and any constraints upon them, the behavioural interactions of predators with different prey defences, the numerical responses of predators governed by movement and reproduction, the diversity and abundance of undefended alternative prey and Batesian mimics in the community, and variability in other ecological circumstances. We also discuss the macroevolution of warning signals. Our review finds that we have a basic understanding of how many species in some taxonomic groups have warning signals, but very little information on the interrelationships among population abundances across prey communities, the diversity of signal phenotypes, and prey defences. We also have detailed knowledge of how a few generalist predator species forage in artificial laboratory environments, but we know much less about how predators forage in complex natural communities with variable prey defences. We describe how empirical work to address each of these knowledge gaps can test specific hypotheses for why warning signals exhibit their particular patterns of distribution. This will help us to understand how behavioural interactions shape ecological communities.

Towards an ecology of protective coloration

The strategies underlying different forms of protective coloration are well understood but little attention has been paid to the ecological, life-history and behavioural circumstances under which they evolve. While some comparative studies have investigated the ecological correlates of aposematism, and background matching, the latter particularly in mammals, few have examined the ecological correlates of other types of protective coloration. Here, we first outline which types of defensive coloration strategies may be exhibited by the same individual; concluding that many protective coloration mechanisms can be employed simultaneously, particularly in conjunction with background matching. Second, we review the ecological predictions that have been made for each sort of protective coloration mechanism before systematically surveying phylogenetically controlled comparative studies linking ecological and social variables to antipredator defences that involve coloration. We find that some a priori predictions based on small-scale empirical studies and logical arguments are indeed supported by comparative data, especially in relation to how illumination affects both background matching and self-shadow concealment through countershading; how body size is associated with countershading, motion dazzle, flash coloration and aposematism, although only in selected taxa; how immobility may promote background matching in ambush predators; and how mobility may facilitate motion dazzle. Examination of nearly 120 comparative tests reveals that many focus on ecological variables that have little to do with predictions derived from antipredator defence theory, and that broad-scale ecological studies of defence strategies that incorporate phylogenetics are still very much in their infancy. We close by making recommendations for future evolutionary ecological research.

Help or hindrance? The evolutionary impact of whole-genome duplication on immunogenetic diversity and parasite load

Whole-genome duplication (WGD) events occur in all kingdoms and have been hypothesized to promote adaptability. WGDs identified in the early history of vertebrates, teleosts, and angiosperms have been linked to the large-scale diversification of these lineages. However, the mechanics and full outcomes of WGD regarding potential evolutionary impacts remain a topic of debate. The Corydoradinae are a diverse subfamily of Neotropical catfishes with over 170 species described and a history of WGDs. They are divided into nine mtDNA lineages, with species coexisting in sympatric-and often mimetic-communities containing representatives of two or more of the nine lineages. Given their similar life histories, coexisting species of Corydoras might be exposed to similar parasite loads and because of their different histories of WGD and genome size they provide a powerful system for investigating the impacts of WGD on immune diversity and function in an animal system. Here, we compared parasite counts and the diversity of the immune-related toll-like receptors (TLR) in two coexisting species of Corydoras catfish (C. maculifer and C. araguaiaensis), one diploid and one putative tetraploid. In the putative tetraploid C. araguaiaensis, we found significantly lower numbers of parasites and significantly higher diversity (measured by both synonymous and nonsynonymous SNP counts) in two TLR genes than in the diploid C. maculifer. These results provide insight into how WGD may impact evolution, in this case by providing greater immunogenetic diversity.

Artificial whole genome duplication in paleopolyploid sturgeons yields highest documented chromosome number in vertebrates

Critically endangered sturgeons, having undergone three whole genome duplication events, represent an exceptional example of ploidy plasticity in vertebrates. Three extant ploidy groups, combined with autopolyploidization, interspecific hybridization and the fertility of hybrids are important issues in sturgeon conservation and aquaculture. Here we demonstrate that the sturgeon genome can undergo numerous alterations of ploidy without severe physiological consequences, producing progeny with a range of ploidy levels and extremely high chromosome numbers. Artificial suppression of the first mitotic division alone, or in combination with suppression of the second meiotic division of functionally tetraploid zygotes (4n, C-value = 4.15) of Siberian sturgeon Acipenser baerii and Russian sturgeon A. gueldenstaedtii resulted in progeny of various ploidy levels—diploid/hexaploid (2n/6n) mosaics, hexaploid, octoploid juveniles (8n), and dodecaploid (12n) larvae. Counts between 477 to 520 chromosomes in octoploid juveniles of both sturgeons confirmed the modal chromosome numbers of parental species had been doubled. This exceeds the highest previously documented chromosome count among vertebrates 2n ~ 446 in the cyprinid fish Ptychobarbus dipogon.

A journey through the Amazon Middle Earth reveals Aspidoras azaghal (Siluriformes: Callichthyidae), a new species of armoured catfish from the rio Xingu basin, Brazil

Aspidoras azaghal n. sp. was discovered during a multitaxonomic scientific expedition to the remote Amazon Terra do Meio region in tributaries to the rio Xingu basin, Pará, Brazil. The new species can be promptly distinguished from its congeners by the following combination of features: (a) absence of the first dorsal-fin element; (b) parieto-supraoccipital fontanel located medially on bone; (c) absence of a longitudinal dark-brown or black stripe along flank midline; (d) ventral surface of trunk covered by clearly smaller, irregular and/or roundish platelets; (e) inner laminar expansion of infraorbital 1 well developed; (f) relatively wide frontal bone, with width equal to half of entire length; (g) absence of a thick, longitudinal conspicuous dark-brown stripe along dorsal portion of flank; and (h) poorly developed serrations on posterior margin of the pectoral-fin spine. Besides morphological evidence, the molecular analyses indicated significant differences between the new species and its congeners, with A. albater and A. raimundi as its closest species, showing 6.53% of genetic differentiation in both cases. The intraspecific molecular data revealed gene flow (peer fixation index, FST = 0.05249, P > 0.05, for the cytochrome oxidase I (COI) marker and FST = -0.01466, P > 0.05, for the control region) between specimens upstream and downstream from a 30-m height waterfall at the type-locality, which therefore represent a single population. Furthermore, it was possible to observe a unidirectional gene flow pattern, with genetic diversity increasing in the downstream direction.

Trophic morphology features allow Astyanax endemic species coexistence in a Neotropical river system

Resource partitioning has an essential role in interspecific relations, especially in congener species, which share many morphological traits. In some places, small characids coexist through resource partitioning, which may reduce their interspecific competition. Astyanax species (e.g., Astyanax minor, Astyanax gymnodontus and Astyanax bifasciatus), for example, coexist in different water bodies from the Iguaçu River basin. These species have high phenotypic plasticity and many morphologic specializations that allow them to live in different habitats. Based on evidences that these species modified their feeding habits because of changes in resource availability in Iguaçu River, this study tested two hypotheses: (a) there are differences in head morphology, number of teeth and number of gill rakers among the species of Astyanax; and (b) there are differences in gill arch and gill raker morphology among the species of Astyanax, which may favour their trophic resource partitioning in Iguaçu River. The head morphological traits and quantitative morphological characters were summarized in a principal coordinates analysis (PCoA), and the analysis of similarities (ANOSIM) showed significant differences among species. Gill morphological measurements were analysed through analysis of covariance (ANCOVA), and it also showed significant differences in gill arch and gill raker morphology among species. Therefore, the analysis of ecomorphological traits related to trophic habits revealed some differences that may suggest a tendency of reducing competition for trophic resources in the Iguaçu River basin.

Mechanisms for Color Convergence in a Mimetic Radiation of Poison Frogs

In animals, bright colors often evolve to mimic other species when a resemblance is selectively favored. Understanding the proximate mechanisms underlying such color mimicry can give insights into how mimicry evolves-for example, whether color convergence evolves from a shared set of mechanisms or through the evolution of novel color production mechanisms. We studied color production mechanisms in poison frogs (Dendrobatidae), focusing on the mimicry complex of Ranitomeya imitator. Using reflectance spectrometry, skin pigment analysis, electron microscopy, and color modeling, we found that the bright colors of these frogs, both within and outside the mimicry complex, are largely structural and produced by iridophores but that color production depends crucially on interactions with pigments. Color variation and mimicry are regulated predominantly by iridophore platelet thickness and, to a lesser extent, concentration of the red pteridine pigment drosopterin. Compared with each of the four morphs of model species that it resembles, R. imitator displays greater variation in both structural and pigmentary mechanisms, which may have facilitated phenotypic divergence in this species. Analyses of nonmimetic dendrobatids in other genera demonstrate that these mechanisms are widespread within the family and that poison frogs share a complex physiological "color palette" that can produce diverse and highly reflective colors.

Taxonomic review of the typical long-snouted species of Corydoras (Siluriformes: Callichthyidae) from the río de La Plata basin

Abstract The typical long-snouted species of Corydoras from the río de La Plata basin were reviewed herein, and the previously proposed synonymy of Corydoras ellisae was corroborated. Corydoras areio and C. aurofrenatus are diagnosed from their congeners, excluding those in lineage 1, by the following features: temporal sensory canal in sphenotic with two pores; upper tooth plate of branchial arch with three or four series of teeth; fleshy flap at mouth corner. Corydoras areio differs from all lineage 1 congeners by having infraorbital 2 with relatively wider posterior laminar expansion; absence of large patches of black pigmentation on the body and absence of conspicuous concentration of dark brown or black chromatophores on anterior portion of the dorsal fin; and presence of blotches on flanks not aligned in longitudinal series. Corydoras aurofrenatus differs from all lineage 1 congeners by having ventral surface of head and trunk densely covered by small, not coalescent platelets; middle portion of flank with two or three dark brown or black patches (below the dorsal-fin, below the adipose-fin base, and on the caudal peduncle base, diffuse and variably present), patches decreasing in size posteriorly; poorly developed fleshy flap at the corner of mouth; anteroventral portion of cleithrum exposed.

The paradox behind the pattern of rapid adaptive radiation: how can the speciation process sustain itself through an early burst?

Rapid adaptive radiation poses a distinct question apart from speciation and adaptation: what happens after one speciation event? That is, how are some lineages able to continue speciating through a rapid burst? This question connects global macroevolutionary patterns to microevolutionary processes. Here we review major features of rapid radiations in nature and their mismatch with theoretical models and what is currently known about speciation mechanisms. Rapid radiations occur on three major diversification axes - species richness, phenotypic disparity, and ecological diversity - with exceptional outliers on each axis. The paradox is that the hallmark early stage of adaptive radiation, a rapid burst of speciation and niche diversification, is contradicted by most existing speciation models which instead predict continuously decelerating speciation rates and niche subdivision through time. Furthermore, while speciation mechanisms such as magic traits, phenotype matching, and physical linkage of co-adapted alleles promote speciation, it is often not discussed how these mechanisms could promote multiple speciation events in rapid succession. Additional mechanisms beyond ecological opportunity are needed to understand how rapid radiations occur. We review the evidence for five emerging theories: 1) the 'transporter' hypothesis: introgression and the ancient origins of adaptive alleles, 2) the 'signal complexity' hypothesis: the dimensionality of sexual traits, 3) the connectivity of fitness landscapes, 4) 'diversity begets diversity', and 5) flexible stem/'plasticity first'. We propose new questions and predictions to guide future work on the mechanisms underlying the rare origins of rapid radiation.

OSF-Builder: A New Tool for Constructing and Representing Evolutionary Histories Involving Introgression

Introgression is an evolutionary process which provides an important source of innovation for evolution. Although various methods have been used to detect introgression, very few methods are currently available for constructing evolutionary histories involving introgression. In this article, we propose a new method for constructing such evolutionary histories whose starting point is a species forest (consisting of a collection of lineage trees, usually arising as a collection of clades or monophyletic groups in a species tree), and a gene tree for a specific allele of interest, or allele tree for short. Our method is based on representing introgression in terms of a certain "overlay" of the allele tree over the lineage trees, called an overlaid species forest (OSF). OSFs are similar to phylogenetic networks although a key difference is that they typically have multiple roots because each monophyletic group in the species tree has a different point of origin. Employing a new model for introgression, we derive an efficient algorithm for building OSFs called OSF-Builder that is guaranteed to return an optimal OSF in the sense that the number of potential introgression events is minimized. As well as using simulations to assess the performance of OSF-Builder, we illustrate its use on a butterfly data set in which introgression has been previously inferred. The OSF-Builder software is available for download from https://www.uea.ac.uk/computing/software/OSF-Builder.

Deconstructing an octogenarian misconception reveals the true Corydoras arcuatus Elwin 1938 (Siluriformes: Callichthyidae) and a new Corydoras species from the Amazon basin

After 80 years of misidentifications, the analysis of the holotype of Corydoras arcuatus plus several non-type specimens attributed to this species allowed its recognition and also revealed a new species, both sharing the following diagnostic features: a long, arched, continuous black stripe that runs parallel to the dorsal profile of the body and extends at least from the anterior margin of the first dorsolateral body plate to the posterior portion of caudal peduncle; absence of transverse black bars on caudal fin; infraorbital 2 in contact with sphenotic and compound pterotic. In addition to these features, C. arcuatus can be distinguished from congeners by having the posterior margin of both dorsal and pectoral spines with laminar serrations directed towards their origins. The new species can be additionally distinguished from its congeners by presenting the following combination of features: ventral surface of trunk entirely or partially covered by relatively large and coalescent platelets; absence of spots or blotches on dorsal fin; and posterior margin of both dorsal and pectoral spines with serrations directed towards their tips. Finally, an identification key to all arc-striped species of Corydoras is provided.

Evolution: Fangtastic Venoms Underpin Parasitic Mimicry

Venomous teeth are rare in fishes, which typically utilise spines for defence. A new study reveals the evolutionary origins of fangs and venom in the Nemophini blennies and shows that, in contrast to snakes and lizards, the fangs pre-date the venom.

Local habitat preferences of a semi-aquatic mammal, the Pyrenean desman Galemys pyrenaicus

To date, the large-scale distribution of the endangered Pyrenean desman, Galemys pyrenaicus, has been related to various abiotic factors (e.g. riverbed and riverbank characteristics, hydrology, topography, climate). However, none could fully explain the recent observed range contraction of the species, suggesting the influence of other drivers. In this study, the potential effect of some unexplored variables on the Pyrenean desman presence was investigated at the local scale (i.e. stream reaches) in the French Pyrenees. They described not only the riverbed, riverbanks, water chemistry, topography and pedology but also the presence of potential interacting species. Generalised linear models were implemented to select the best drivers of the Pyrenean desman presence. Our results stressed the relevance of considering human impacts at the riverbed scale, river narrowing and water chemistry to explain the local distribution of the Pyrenean desman. The presence of two potential competitors, the Eurasian water shrew Neomys fodiens and the dipper Cinclus cinclus, was also highly correlated to the species presence in stream reaches. This suggests that all three species may use the same resources within streams, which could be a potential source of competitive interactions. This study not only highlights the importance of maintaining the riverbed integrity for the Pyrenean desman but also stresses the need to assess the extent to which biotic interactions may affect its distribution in order to understand its current decline.

Redescription of Corydoras undulatus Regan, 1912 (Siluriformes: Callichthyidae), with comments on the identity of Corydoras latus Pearson, 1924

A redescription of Corydoras undulatus Regan, 1912 is presented. The original description of C. undulatus is very succinct, as is its diagnosis, which is based only on external morphology. Additional information in the scientific literature on this species is scarce. Specimens from the distribution area of this species were analyzed; Paraná and Paraguay river basins in Argentina, Uruguay river basin in Argentina, Brazil and Uruguay, and the Laguna dos Patos system in Brazil. Morphological analysis, principal component analysis (PCA), meristic comparison and osteological description were performed. Corydoras undulatus can be distinguished from its congeners mainly by having the following combination of characters: mesethmoid short, with anterior tip short, smaller than 50% of the entire bone length; posterior margin of the pectoral-fin spine with nearly all serrations directed towards origin of spine; pectoral-fin spine with conical serrations; and its peculiar color pattern. The analysis of the material from the different basins did not indicate relevant morphological differences, suggesting that the species presents a wide distribution in La Plata and Laguna dos Patos drainages. The shared geographic distribution between these two systems is also present in other fish species. The current work presents data about the type locality, taxonomy, osteology, distribution and ontogenetic variation of color pattern in C. undulatus. Comments on the identity of a very similar congener, Corydoras latus, will also be provided.

Evolutionary Ecology of Fish Venom: Adaptations and Consequences of Evolving a Venom System

Research on venomous animals has mainly focused on the molecular, biochemical, and pharmacological aspects of venom toxins. However, it is the relatively neglected broader study of evolutionary ecology that is crucial for understanding the biological relevance of venom systems. As fish have convergently evolved venom systems multiple times, it makes them ideal organisms to investigate the evolutionary ecology of venom on a broader scale. This review outlines what is known about how fish venom systems evolved as a result of natural enemy interactions and about the ecological consequences of evolving a venom system. This review will show how research on the evolutionary ecology of venom in fish can aid in understanding the evolutionary ecology of animal venoms more generally. Further, understanding these broad ecological questions can shed more light on the other areas of toxinology, with applications across multiple disciplinary fields.

Whole genome duplication and transposable element proliferation drive genome expansion in Corydoradinae catfishes

Genome size varies significantly across eukaryotic taxa and the largest changes are typically driven by macro-mutations such as whole genome duplications (WGDs) and proliferation of repetitive elements. These two processes may affect the evolutionary potential of lineages by increasing genetic variation and changing gene expression. Here, we elucidate the evolutionary history and mechanisms underpinning genome size variation in a species-rich group of Neotropical catfishes (Corydoradinae) with extreme variation in genome size—0.6 to 4.4 pg per haploid cell. First, genome size was quantified in 65 species and mapped onto a novel fossil-calibrated phylogeny. Two evolutionary shifts in genome size were identified across the tree—the first between 43 and 49 Ma (95% highest posterior density (HPD) 36.2–68.1 Ma) and the second at approximately 19 Ma (95% HPD 15.3–30.14 Ma). Second, restriction-site-associated DNA (RAD) sequencing was used to identify potential WGD events and quantify transposable element (TE) abundance in different lineages. Evidence of two lineage-scale WGDs was identified across the phylogeny, the first event occurring between 54 and 66 Ma (95% HPD 42.56–99.5 Ma) and the second at 20–30 Ma (95% HPD 15.3–45 Ma) based on haplotype numbers per contig and between 35 and 44 Ma (95% HPD 30.29–64.51 Ma) and 20–30 Ma (95% HPD 15.3–45 Ma) based on SNP read ratios. TE abundance increased considerably in parallel with genome size, with a single TE-family (TC1-IS630-Pogo) showing several increases across the Corydoradinae, with the most recent at 20–30 Ma (95% HPD 15.3–45 Ma) and an older event at 35–44 Ma (95% HPD 30.29–64.51 Ma). We identified signals congruent with two WGD duplication events, as well as an increase in TE abundance across different lineages, making the Corydoradinae an excellent model system to study the effects of WGD and TEs on genome and organismal evolution.

Comparative gross encephalon morphology in Callichthyidae (Teleostei: Ostariophysi: Siluriformes)

ABSTRACT Callichthyidae comprises the subfamilies Callichthyinae and Corydoradinae, both of which are morphologically distinct and monophyletic. Although there is consensus regarding the monophyly of the family, the relationships of about 80% of its species, currently included in the genus Corydoras, remain poorly known. Despite the vast amount of osteological information for Teleostei, knowledge regarding the phylogenetic implications of encephalon anatomy is sparse and represents a poorly explored source of potential characters. The present study aims to describe the encephalon morphology in members of the Callichthyidae in order to propose new characters that may help address phylogenetic questions regarding this group. In addition to representatives of Callichthyidae, specimens belonging to the Nematogenyidae, Trichomycteridae, Scoloplacidae, Astroblepidae and Loricariidae were dissected for comparative purposes. Head dissection revealed information on the structure of the medulla spinalis, rhombencephalon, mesencephalon, diencephalon and telencephalon. The conditions observed on the encephalons examined suggest that representatives of Callichthyidae have great taste perception and processing, while Corydoradinae stand out for visual acuity and Callichthyinae for mechanoreception processing subunits. Our results also indicate that the encephalon has important features for systematic studies of the family bringing greater resolution to current phylogenetic hypotheses.

Chromosomes of Asian cyprinid fishes: cytogenetic analysis of two representatives of small paleotetraploid tribe Probarbini

Background

Polyploidy, although still poorly explored, represents an important evolutionary event in several cyprinid clades. Herein, Catlocarpio siamensis and Probarbus jullieni - representatives of the paleotetraploid tribe Probarbini, were characterized both by conventional and molecular cytogenetic methods.

Results

Alike most other paleotetraploid cyprinids (with 2n = 100), both species studied here shared 2n = 98 but differed in karyotypes: C. siamensis displayed 18m + 34sm + 46st/a; NF = 150, while P. jullieni exhibited 26m + 14sm + 58st/a; NF = 138. Fluorescence in situ hybridization (FISH) with rDNA probes revealed two (5S) and eight (18S) signals in C. siamensis, respectively, and six signals for both probes in P. jullieni. FISH with microsatellite motifs evidenced substantial genomic divergence between both species. The almost doubled size of the chromosome pairs #1 in C. siamensis and #14 in P. jullieni compared to the rest of corresponding karyotypes indicated chromosomal fusions.

Conclusion

Based on our findings, together with likely the same reduced 2n = 98 karyotypes in the remainder Probarbini species, we hypothesize that the karyotype 2n = 98 might represent a derived character, shared by all members of the Probarbini clade. Besides, we also witnessed considerable changes in the amount and distribution of certain repetitive DNA classes, suggesting complex post-polyploidization processes in this small paleotetraploid tribe.

From the inside out: a new species of armoured catfish Corydoras with the description of poorly-explored character sources (Teleostei, Siluriformes, Callichthyidae)

A new species of the armoured catfish genus Corydoras is described from the Xingu-Tapajos ecoregion, Brazilian Amazon. The new species can be distinguished from its congeners by having the following combination of features: short mesethmoid, with anterior tip poorly developed, smaller than 50% of bone length; posterior margin of pectoral spine with serrations directed towards spine tip or perpendicularly oriented; infraorbital 2 only in contact with sphenotic; ventral laminar expansion of infraorbital 1 poorly or moderately developed; flank midline covered by small dark brown or black saddles with similar size to remaining markings on body; relatively larger, scarcer and more sparsely distributed dark brown or black spots on body; absence of stripe on flank midline; caudal fin with conspicuous dark brown or black spots along its entire surface; slender body; and strongly narrow frontals. A more comprehensive description of poorly-explored internal character sources, such as the gross morphology of the brain, Weberian apparatus and swimbladder capsule elements is presented.

Signals, cues and the nature of mimicry

'Mimicry' is used in the evolutionary and ecological literature to describe diverse phenomena. Many are textbook examples of natural selection's power to produce stunning adaptations. However, there remains a lack of clarity over how mimetic resemblances are conceptually related to each other. The result is that categories denoting the traditional subdivisions of mimicry are applied inconsistently across studies, hindering attempts at conceptual unification. This review critically examines the logic by which mimicry can be conceptually organized and analysed. It highlights the following three evolutionarily relevant distinctions. (i) Are the model's traits being mimicked signals or cues? (ii) Does the mimic signal a fitness benefit or fitness cost in order to manipulate the receiver's behaviour? (iii) Is the mimic's signal deceptive? The first distinction divides mimicry into two broad categories: 'signal mimicry' and 'cue mimicry'. 'Signal mimicry' occurs when mimic and model share the same receiver, and 'cue mimicry' when mimic and model have different receivers or when there is no receiver for the model's trait. 'Masquerade' fits conceptually within cue mimicry. The second and third distinctions divide both signal and cue mimicry into four types each. These are the three traditional mimicry categories (aggressive, Batesian and Müllerian) and a fourth, often overlooked category for which the term 'rewarding mimicry' is suggested. Rewarding mimicry occurs when the mimic's signal is non-deceptive (as in Müllerian mimicry) but where the mimic signals a fitness benefit to the receiver (as in aggressive mimicry). The existence of rewarding mimicry is a logical extension of the criteria used to differentiate the three well-recognized forms of mimicry. These four forms of mimicry are not discrete, immutable types, but rather help to define important axes along which mimicry can vary.

Evolutionary Assembly of Communities in Butterfly Mimicry Rings

Species co-occurrence in ecological communities is thought to be influenced by multiple ecological and evolutionary processes, especially colonization and competition. However, effects of other interspecific interactions and evolutionary relationships are less explored. We examined evolutionary histories of community members and roles of mutualistic and parasitic interactions (Müllerian and Batesian mimicry, respectively) in the assembly of mimetic butterfly communities called mimicry rings in tropical forests of the Western Ghats, India. We found that Müllerian mimics were phylogenetically clustered, sharing aposematic signals due to common ancestry. On the other hand, Batesian mimics joined mimicry rings through convergent evolution and random phylogenetic assembly. Since the Western Ghats are a habitat island, we compared species diversity and composition in its mimicry rings with those of habitat mainland to test effects of biogeographic connectivity. The Western Ghats consisted of fewer mimicry rings and an overall smaller number of aposematic species and mimics compared to habitat mainland. The depauperate mimicry rings in the Western Ghats could have resulted from stochastic processes, reflecting their long temporal and spatial isolation and trickling colonization by the mimetic butterfly communities. These results highlight how evolutionary history, biogeographic isolation, and stochastic colonization influence the evolutionary assembly and diversity of ecological communities.

The golden mimicry complex uses a wide spectrum of defence to deter a community of predators

Mimicry complexes typically consist of multiple species that deter predators using similar anti-predatory signals. Mimics in these complexes are assumed to vary in their level of defence from highly defended through to moderately defended, or not defended at all. Here, we report a new multi-order mimicry complex that includes at least 140 different putative mimics from four arthropod orders including ants, wasps, bugs, tree hoppers and spiders. All members of this mimicry complex are characterised by a conspicuous golden body and an ant Gestalt, but vary substantially in their defensive traits. However, they were similarly effective at deterring predators - even mildly defended mimics were rarely eaten by a community of invertebrate and vertebrate predators both in the wild and during staged trials. We propose that despite the predominance of less defended mimics the three predatory guilds avoid the mimics because of the additive influence of the various defensive traits.

DOI:http://dx.doi.org/10.7554/eLife.22089.001

Many animals use bright colours to warn a potential predator that they can defend themselves. Wasps, for instance, are armed with a harmful sting and advertise this fact via their distinctive yellow and black stripes. Predators often learn to heed such warnings and avoid these unpalatable animals in future. As a result, animals that mimic another animal’s warning signals can reap the benefit of being left alone by predators even if they are otherwise undefended.

Textbooks on evolution are typically full of different examples of mimicry. However, the specifics of these examples are often poorly understood. Ninety years ago a famous Australian entomologist, Alexander Nicholson, suggested the existence of large groups of mimics in the Australian wildlife. More of these so-called “mimetic complexes” have recently been recognized among several species of insect, but not previously in ants.

Now, Pekár et al. have looked at all known ants and ant-like mimics in Australia and discovered over 140 species that use gold and black colours as a warning signal. Most of the species were ants, but the collection of mimics also includes wasps, spiders, true bugs and insects called treehoppers. Some of the mimics were less palatable than others, and they possessed a range of defences, including spines and foul-tasting chemicals.

Pekár et al. then looked in the guts of 12 species of predators in the wild, and found that very few of them ate the mimics. When mimics were offered to three different predators (specifically a lizard and two species of spider), most avoided the mimics regardless of whether they were palatable or unpalatable. Instead, the predators preferred to eat a spider that was not a member of the group of mimics because it lacked the gold colouration.

Further studies are now needed to continue to document the details of this and other mimetic complexes. For example, this includes revealing how the different defences protect the members of the complex from predators do not use vision to recognize their prey and so cannot see the warning colouration. All this is needed to understand evolutionary processes that have fascinated biologists for decades, and explain how such large mimetic complexes evolved and persisted in spite of the influence of the community of predators.

DOI:http://dx.doi.org/10.7554/eLife.22089.002

Variation in male reproductive system characters in Corydoradinae (Loricarioidei: Callichthyidae) reflects the occurrence of different lineages in this subfamily

ABSTRACT Callichthyidae comprises a well-corroborated monophyletic group divided into two subfamilies: Corydoradinae and Callichthyinae. A recent proposal, based on molecular data, suggests that Corydoradinae is composed by nine monophyletic lineages, possibly genera. The species pertaining to those lineages have extensive modification in the size of genome, including diploid, tetraploid and octoploid species. Considering the occurrence of these monophyletic lineages and that the variations in DNA content may imply in significant alterations on the structure of spermatozoa, this study analyzed the morphology of the male reproductive system and the morphometry of the head of the spermatozoa of representatives of the nine lineages of Corydoradinae, seeking for particular characteristics of each lineage. Morphological data revealed a high intra-lineage variation, larger than that observed among species of different lineages. In contrast, morphometric data obtained for eight out of the nine lineages, revealed large congruency with the hypothesis that Corydoradinae is composed by different lineages. These results demonstrate that there is a correlation among variations in DNA content and the size of the spermatozoon head, thus providing additional subsides for the definition of the Corydoradinae lineages.

A new species of Aspidoras (Siluriformes: Callichthyidae) from a small coastal drainage in northeastern Brazil

ABSTRACT A new species of Aspidoras from the rio da Dona basin, a small coastal river drainage in Bahia State, is described herein. The new taxon differs from its congeners by presenting infraorbital 1 with well-developed ventral laminar expansion, nuchal plate nearly reaching to or sometimes contacting posterior process of parieto-supraoccipital, anterior tip of nuchal plate just posterior to dorsal margin of first dorsolateral body plate, and blotches on dorsal half of dorsolateral body plates and/or ventral half of ventrolateral body plates fused with midlateral series of blotches, forming three or four enlarged and oblique black blotches.

Mimicry Cycles, Traps, and Chains: The Coevolution of Toucan and Kiskadee Mimicry

Interspecific social dominance mimicry (ISDM) is a form of social parasitism in which a subordinate species evolves to mimic and deceive a dominant interference competitor in order to avoid attack by the dominant species. ISDM has been proposed to result in (1) antagonistic coevolutionary arms races in appearance between the model and the mimic (e.g., Ramphastos toucans) and (2) the evolution of complexes of multiple species converging on a common visual appearance (e.g., kiskadee flycatchers). We present evolutionary games of antagonistic coevolution in appearance between pairs and triplets of sympatric species under interference competition. We identify conditions for the existence and stability of (1) coevolutionary mimicry cycles in appearance between evader and pursuer strategies of models and mimics, (2) mimicry chains in which three or more species are coevolutionarily entrained to evolve a single common appearance despite differences in their costs and benefits, and (3) mimicry traps in which a subdominant species is evolutionarily constrained from evading mimicry by a third, subordinate mimic species. Mimicry cycles will result in the evolutionary divergence of models and mimics from their ancestral phenotypes. The hierarchical evolutionary dynamics of ISDM traps and chains resemble Müllerian mimicry with variable costs to toxicity.

Revisionary study of the armored catfish Corydoras paleatus (Jenyns, 1842) (Siluriformes: Callichthyidae) over 180 years after its discovery by Darwin, with description of a new species

ABSTRACT The taxon known as Corydoras paleatus carries one of the most complex taxonomic histories among Corydoradinae catfishes. A comprehensive review of specimens attributed to that species from several localities was carried out, allowing the clear recognition of C. paleatus and also of a new species previously misidentified as C. paleatus , described herein. Corydoras paleatus can be distinguished from its congeners by presenting the following unique combination of features: perpendicularly directed serrations along entire posterior margin of the pectoral spine; three large black blotches along midline of flank; hyaline or black pectoral fin; and transversal black bars on caudal-fin lobes. Corydoras paleatus is known from the lower rio Paraná basin, coastal rivers from Southern Brazil and Uruguay and rio Uruguai basin. The new species can be distinguished from its congeners by having the following unique combination of features: three large black blotches along midline of flank; three nasal pores; mesethmoid short; infraorbital 2 not in contact with compound pterotic; striated black spots from the snout tip to nuchal plate region; markedly rounded snout; and anterior portion of dorsal fin spotted. The new species is known from the upper rio Uruguai basin, from the rivers Canoas, do Peixe and Pelotas.

A new species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the río Madre de Dios basin, Peru

ABSTRACT A new species of Corydoras is described from the río Madre de Dios basin, Peru. The new species can be distinguished from its congeners by presenting the following features: a longitudinal black stripe along midline of flank; mesethmoid short, with anterior portion poorly developed; serrations on posterior margin of pectoral spine directed towards the tip of the spine; dorsal fin with the region of the first branched ray, including membrane, with concentration of black pigmentation, the remaining areas with irregular black blotches; absence of a vertically elongated black blotch across the eyes; conspicuously rounded moderately-developed black spots on the snout; and ventral expansion of infraorbital 1 moderately developed.

The complete mitochondrial genome of Corydoras nattereri (Callichthyidae: Corydoradinae)

ABSTRACT The complete mitogenome of Corydoras nattereri , a species of mailed catfishes from southeastern Brazil, was reconstructed using next-generation sequencing techniques. The mitogenome was assembled using mitochondrial transcripts from the liver transcriptomes of three individuals, and produced a circular DNA sequence of 16,557 nucleotides encoding 22 tRNA genes, two rRNA genes, 13 protein-coding genes and two noncoding control regions (D-loop, OrigL). Phylogeographic analysis of closely related sequences of Cytochrome Oxydase C subunit I (COI) demonstrates high diversity among morphologically similar populations of C. nattereri . Corydoras nattereri is nested within a complex of populations currently assigned to C. paleatus and C. ehrhardti . Analysis of mitogenome structure demonstrated that an insertion of 21 nucleotides between the ATPase subunit-6 and COIII genes may represent a phylogenetically informative character associated with the evolution of the Corydoradinae.

A new Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Araguaia basin, Brazil, with comments about Corydoras araguaiaensis Sands, 1990

ABSTRACT A new species of Corydoras is described from the rio Araguaia basin, Goiás, Brazil. The new species can be distinguished from its congeners by presenting the following features: infraorbital 1 with very large ventral laminar expansion; infraorbital 2 contacting compound pterotic; flanks densely covered by irregular black spots; and ventral surface of trunk densely covered by coalescent relatively well-developed platelets. It is also discussed the possibility that C. araguaiaensis comprehends a complex of species.

Two new species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Madeira basin, Brazil

Abstract Two new species of Corydoras are described from the rio Madeira basin, Brazil. The intermediate long-snouted new species can be distinguished from its congeners by presenting the following combination of features: posterior margin of dorsal-fin spine with laminar serrations directed towards the origin of the spine; presence of two longitudinal black stripes on flanks; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; absence of a conspicuous black marbled coloration pattern on head; black spots on caudal fin, some spots arranged, forming transversal bars; and brownish dorsal-fin spine. The short-snouted new speciescan be distinguished from its congeners by the following combination of features: short mesethmoid; posterior laminar expansion of infraorbital 2 very reduced, not in contact with compound pterotic; two or three longitudinal black stripes on flanks; absence of an oblique or vertical black blotch across the eye; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; and ventral surface of trunk naked or covered by sparse platelets.

Redescription of Corydoras guapore Knaack, 1961 (Siluriformes: Callichthyidae), a midwater Corydoradinae species from the rio Guaporé basin

Corydoras guapore was described from the rio Guaporé, Rondônia State, Brazil, based only in three specimens, two of them merely examined alive in an aquarium and apparently not preserved posteriorly. The current location of these two paratypes is uncertain. In the original description, no standard diagnosis was presented and the descriptive information available is scarce and based only in external morphology. Thus, the aim of this study is to provide a redescription of C. guapore based in several topotypes. Corydoras guapore can be distinguished from its congeners by the presence of a short mesethmoid, with the anterior tip poorly developed; posterior margin of pectoral spine with conical serrations directed towards the origin of the spine; and by the lateral portion of caudal peduncle almost entirely blackened. Information about C. guapore ecology and conservation status are also provided.

Trophic interactions induce spatial self-organization of microbial consortia on rough surfaces

The spatial context of microbial interactions common in natural systems is largely absent in traditional pure culture-based microbiology. The understanding of how interdependent microbial communities assemble and coexist in limited spatial domains remains sketchy. A mechanistic model of cell-level interactions among multispecies microbial populations grown on hydrated rough surfaces facilitated systematic evaluation of how trophic dependencies shape spatial self-organization of microbial consortia in complex diffusion fields. The emerging patterns were persistent irrespective of initial conditions and resilient to spatial and temporal perturbations. Surprisingly, the hydration conditions conducive for self-assembly are extremely narrow and last only while microbial cells remain motile within thin aqueous films. The resulting self-organized microbial consortia patterns could represent optimal ecological templates for the architecture that underlie sessile microbial colonies on natural surfaces. Understanding microbial spatial self-organization offers new insights into mechanisms that sustain small-scale soil microbial diversity; and may guide the engineering of functional artificial microbial consortia.