In theory, evolutionary modularity allows anatomical structures to respond differently to selective regimes, thus promoting morphological diversification. These differences can then influence the rate and direction of phenotypic evolution among structures. Here we use geometric morphometrics and phenotypic matrix statistics to compare rates of craniofacial evolution and estimate evolvability in the face and braincase modules of a clade of teleost fishes (Gymnotiformes) and a clade of mammals (Carnivora), both of which exhibit substantial craniofacial diversity. We find that the face and braincase regions of both clades display different degrees of integration. We find that the face and braincase evolve at similar rates in Gymnotiformes and the reverse in Carnivora with the braincase evolving twice as fast as the face. Estimates of evolvability and constraints in these modules suggest differential responses to selection arising from fluctuations in phylogenetic integration, thus influencing differential rates of skull-shape evolution in these two clades.

Resolving patterns of ancient and rapid diversifications is one of the most challenging tasks in evolutionary biology. These difficulties arise from confusing phylogenetic signals that are associated with the interplay of incomplete lineage sorting and homoplasy. Phylogenomic analyses of hundreds, or even thousands, of loci offer the potential to resolve such contentious relationships. Yet, how much useful phylogenetic information these large data sets contain remains uncertain and often goes untested. Here, we assess the utility of different data filtering approaches to maximize phylogenetic information and minimize noise when reconstructing an ancient radiation of Neotropical electric knifefishes (Order Gymnotiformes) using ultraconserved elements. We found two contrasting hypotheses of gymnotiform evolutionary relationships depending on whether phylogenetic inferences were based on concatenation or coalescent methods. In the first case, all analyses inferred a previously-and commonly-proposed hypothesis, where the family Apteronotidae was found as the sister group to all other gymnotiform families. In contrast, coalescent-based analyses suggested a novel hypothesis where families producing pulse-type (viz., Gymnotidae, Hypopomidae and Rhamphichthyidae) and wave-type electric signals (viz., Apteronotidae, Sternopygidae) were reciprocally monophyletic.Nodal support for this second hypothesis increased when analyzing loci with the highest phylogenetic information content and further increased when data were pruned using targeted filtering methods that maximized phylogenetic informativeness at the deepest nodes of the Gymnotiformes. Bayesian concordance analyses and topology tests of individual gene genealogies demonstrated that the difficulty of resolving this radiation was likely due to high gene-tree incongruences that resulted from incomplete lineage sorting. We show that data filtering reduces gene tree heterogeneity and increases nodal support and consistency of species Downloaded from https://academic.oup.com/sysbio/advance-article-abstract/doi/10.1093/sysbio/syy085/5232148 by Bukkyo University user on 06 December 20183 trees using coalescent methods; however, we failed to observe the same effect when using concatenation methods. Furthermore, the targeted filtering strategies applied here support the use of "gene data interrogation" rather than "gene genealogy interrogation" approaches in phylogenomic analyses, to extract phylogenetic signal from intractable portions of the Tree of Life.

Convergent evolution is widely viewed as strong evidence for the influence of natural selection on the origin of phenotypic design. However, the emerging evo‐devo synthesis has highlighted other processes that may bias and direct phenotypic evolution in the presence of environmental and genetic variation. Developmental biases on the production of phenotypic variation may channel the evolution of convergent forms by limiting the range of phenotypes produced during ontogeny. Here, we study the evolution and convergence of brachycephalic and dolichocephalic skull shapes among 133 species of Neotropical electric fishes (Gymnotiformes: Teleostei) and identify potential developmental biases on phenotypic evolution. We plot the ontogenetic trajectories of neurocranial phenotypes in 17 species and document developmental modularity between the face and braincase regions of the skull. We recover a significant relationship between developmental covariation and relative skull length and a significant relationship between developmental covariation and ontogenetic disparity. We demonstrate that modularity and integration bias the production of phenotypes along the brachycephalic and dolichocephalic skull axis and contribute to multiple, independent evolutionary transformations to highly brachycephalic and dolichocephalic skull morphologies.

Identifying habitat characteristics that accelerate organismal evolution is essential to understanding both the origins of life on Earth and the ecosystem properties that are most critical to maintaining life into the future. Searching for these characteristics on a large scale has only recently become possible via advances in phylogenetic reconstruction, time-calibration, and comparative analyses. In this study, we combine these tools with habitat and phenotype data for 105 species in a clade of Neotropical suckermouth catfishes commonly known as cascudinhos. Our goal was to determine whether riverine mesohabitats defined by different flow rates (i.e., pools vs. rapids) and substrates (plants vs. rocks) have affected rates of cascudinho cladogenesis and morphological diversification. In contrast to predictions based on general theory related to life in fast-flowing, rocky riverine habitats, Neoplecostomini lineages associated with these habitats exhibited increased body size, head shape diversity, and lineage and phenotype diversification rates. These findings are consistent with a growing understanding of river rapids as incubators of biological diversification and specialization. They also highlight the urgent need to conserve rapids habitats throughout the major rivers of the world.

A new species of the Eigenmannia trilineata species group is described from the Loreto, Peru region of the western Amazon basin. The new species is similar in external appearance to members of the E. trilineata species group, but has a distinct phenotype, being diagnosed from congeners by the following unique combination of characters: four longitudinal dark pigment stipes on the lateral surfaces (over the lateral line, hypaxial muscles, proximal and distal pterygiophore margins); short, relatively round head (head depth 86.8-96.7% head length) with a terminal mouth; intermediate posterodorsal expansion of infraorbital bones 1+2 (60-75% length of infraorbitals 1+2); 11-15 teeth in three rows on the premaxilla; six to seven teeth in a single row on the endopterygoid; eye high on head (suborbital depth 28-36% head length); ii, 13-14 pectoral-fin rays; 183-219 anal-fin rays; and a uniformly dark brown head and pectoral fins on freshly-preserved specimens. The new species extends the geographic range of described species of the E. trilineata species group to the Western Amazon. This new species elevates the current number of valid species within the E. trilineata species group to 15, and the number of species within Eigenmannia to 20.

A new species of the Eigenmannia trilineata species group is described from the río Orinoco basin, Venezuela. The new species is distinguished from congeners by a unique set of characters including an ossified basibranchial 1; 198-217 anal-fin rays; suborbital depth, 21.3-26.1% HL; length of anterodorsal process of maxilla equal to the width of the posterior nostril; premaxilla with 17 teeth distributed in three rows; hyaline pectoral and anal fins; and number of scale series above lateral line, 9-10. It raises the number of species allocated to the Eigenmannia trilineata species group to 13 and the number of species within the genus to 18.Keywords: Biodiversity, Electric-fishes, Taxonomy, Tuvira.Se describe una nueva especie del grupo Eigenmannia trilineata de la cuenca del río Orinoco, Venezuela. La nueva especie se distingue de sus congéneres por una combinación única de caracteres, incluyendo el basibranquial 1 osificado; número de radios de la anal, 198-217; profundidad del suborbital, 21.3-26.1% HL; longitud del proceso anterodorsal de la maxila igual al ancho de la narina posterior; 17 dientes premaxilares distribuidos en tres hileras; aletas pectoral y anal hialinas; y 9-10 hileras de escamas sobre la serie de la línea lateral. La presente contribución eleva el número de especies del grupo Eigenmannia trilineata a 13, y a 18 aquellas dentro del género.

A new species of Hisonotus is described from the upper rio Paraná and rio São Francisco basins. The new species is distinguished from congeners by (1) completely exposed abdomen with no development of dermal plates (with the exception of extremely small platelets present near the urogenital pore in some specimens) and the combination of the following characters: (2) lack of a conspicuous tuft of enlarged odontodes on posterior tip of parieto-supraoccipital; (3) rectangular dorsal-fin spinelet; (4) complete mid-lateral plate series; (5) higher number of vertebrae, 29-30; (6) dark brown coloration on caudal fin with one pair of circular hyaline colored regions at center of both lobes; (7) absence of broad light stripes on dorsolateral surface of head; (8) odontodes not forming longitudinally aligned rows on head and trunk; and (9) apex of teeth yellowish in color.

The coastal basins in Northeastern Brazil used in this study make up two different ecoregions for freshwater fishes (Amazonas estuary and coastal drainages, and Parnaiba) and two areas of endemism for Characiformes (Maranhão and Parnaíba), and exhibits a diversified yet poorly explored freshwater fish fauna. The population structure and biogeography of two migratory freshwater fish species that are commercially exploited from Maranhão and Parnaíba regions were herein analyzed. Molecular sequence data and statistical analyses were used to estimate haplotypes networks and lineage divergence times and correlated with hydrographic history of drainage and paleodrainages of the region. A total of 171 sequences was produced for both species, Schizodon dissimilis (coI, n = 70) and Prochilodus lacustris (D-loop, n = 101). All analyses identified the presence of three genetically delimited groups of S. dissimilis and six groups of P. lacustris. The lineage time analyses indicate diversification among these species within the past 1 million year. The results indicate the influence of geodispersal in the formation of the ichthyofauna in the studied area through headwater stream capture events and reticulated connections between the mouths of rivers along the coastal plain due to eustatic sea level fluctuations.