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Thomas J Near - One of the best experts on this subject based on the ideXlab platform.
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phylogeny and time scale of diversification in the fossil rich sunfishes and black basses teleostei percomorpha Centrarchidae
Molecular Phylogenetics and Evolution, 2021Co-Authors: Thomas J Near, Daemin KimAbstract:Abstract Species of the North American freshwater fish lineage Centrarchidae are apex predators in their habitats and are among the world’s most popular sport fishes. Centrarchids boast a rich fossil record that extends from the latest Eocene to the Pleistocene. To investigate the phylogeny and timing of diversification of Centrarchidae, we deploy a dataset of DNA sequences of 16 nuclear genes sampled from nearly all of the recognized and undescribed species. We also utilize previously published morphological datasets to assess the phylogenetic placement of one of the oldest known centrarchid fossils, †Plioplarchus whitei. A Bayesian multispecies coalescent species tree analysis provides insight on relationships that evaded resolution in earlier studies, such as the relationships of Acantharchus pomotis, the resolution of a clade consisting of species previously synonymized under the Spotted Bass, Micropterus punctulatus, and a clade of recently described species previously considered populations of the Redeye Bass, Micropterus coosae. This new molecular phylogeny and the inclusion of †P. whitei and other centrarchid fossils in the tip-dated fossilized birth–death analysis results in a new hypothesis of the timing of diversification in Centrarchidae that contextualizes the ages of centrarchid fossils to the timing of speciation among the extant species. In addition to providing new temporal perspectives on the diversification of freshwater fishes in North America, this study may close of the chapter of centrarchid phylogeny inferred using Sanger-sequenced genes, as the use of genomic-scale datasets becomes mainstream in the phylogenetics of fishes.
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introgression and species delimitation in the longear sunfish lepomis megalotis teleostei percomorpha Centrarchidae
Systematic Biology, 2021Co-Authors: Daemin Kim, Thomas J Near, Bruce H BauerAbstract:Introgression and hybridization are major impediments to genomic-based species delimitation because many implementations of the multispecies coalescent framework assume no gene flow among species. The sunfish genus Lepomis, one of the world's most popular groups of freshwater sport fish, has a complicated taxonomic history. The results of ddRAD phylogenomic analyses do not provide support for the current taxonomy that recognizes two species, L. megalotis and L. peltastes, in the L. megalotis complex. Instead, evidence from phylogenomics and phenotype warrants recognizing six relatively ancient evolutionary lineages in the complex. The introgressed and hybridizing populations in the L. megalotis complex are localized and appear to be the result of secondary contact or rare hybridization events between non-sister species. Segregating admixed populations from our multispecies coalescent analyses identifies six species with moderate to high genealogical divergence, whereas including admixed populations drives all but one lineage below the species threshold of genealogical divergence. Segregation of admixed individuals also helps reveal phenotypic distinctiveness among the six species in morphological traits used by ichthyologists to discover and delimit species over the last two centuries. Our protocols allow for the identification and accommodation of hybridization and introgression in species delimitation. Genomic-based species delimitation validated with multiple lines of evidence provides a path towards the discovery of new biodiversity and resolving long-standing taxonomic problems.
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DOI:10.1093/sysbio/syr052 Advance Access publication on July 20, 2011 Phylogeny and Temporal Diversification of Darters (Percidae: Etheostomatinae)
2016Co-Authors: Thomas J Near, Christen M. Bossu, Gideon S. Bradburd, Rose L. Carlson, Richard C. Harrington, Phillip R. Hollingsworth, Benjamin P. Keck, A. EtnierAbstract:Abstract.—Discussions aimed at resolution of the Tree of Life are most often focused on the interrelationships of major organismal lineages. In this study, we focus on the resolution of some of the most apical branches in the Tree of Life through exploration of the phylogenetic relationships of darters, a species-rich clade of North American freshwater fishes. With a near-complete taxon sampling of close to 250 species, we aim to investigate strategies for efficient multilocus data sampling and the estimation of divergence times using relaxed-clock methods when a clade lacks a fossil record. Our phylogenetic data set comprises a single mitochondrial DNA (mtDNA) gene and two nuclear genes sampled from 245 of the 248 darter species. This dense sampling allows us to determine if a modest amount of nuclear DNA sequence data can resolve rela-tionships among closely related animal species. Darters lack a fossil record to provide age calibration priors in relaxed-clock analyses. Therefore, we use a near-complete species–sampled phylogeny of the perciform clade Centrarchidae, which ha
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DOI:10.1093/sysbio/syr052 Phylogeny and Temporal Diversification of Darters (Percidae: Etheostomatinae)
2016Co-Authors: Thomas J Near, Christen M. Bossu, Gideon S. Bradburd, Rose L. Carlson, Richard C. Harrington, Phillip R. Hollingsworth, Benjamin P. Keck, A. EtnierAbstract:Abstract.—Discussions aimed at resolution of the Tree of Life are most often focused on the interrelationships of major organismal lineages. In this study, we focus on the resolution of some of the most apical branches in the Tree of Life through exploration of the phylogenetic relationships of darters, a species-rich clade of North American freshwater fishes. With a near-complete taxon sampling of close to 250 species, we aim to investigate strategies for efficient multilocus data sampling and the estimation of divergence times using relaxed-clock methods when a clade lacks a fossil record. Our phylogenetic data set comprises a single mitochondrial DNA (mtDNA) gene and two nuclear genes sampled from 245 of the 248 darter species. This dense sampling allows us to determine if a modest amount of nuclear DNA sequence data can resolve rela-tionships among closely related animal species. Darters lack a fossil record to provide age calibration priors in relaxed-clock analyses. Therefore, we use a near-complete species–sampled phylogeny of the perciform clade Centrarchidae, which has a rich fossil record, to assess two distinct strategies of external calibration in relaxed-clock divergence time estimates o
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BEAST and *BEAST analyses
2016Co-Authors: Christen M. Bossu, Jeremy M. Beaulieu, Patrick A. Ceas, Thomas J NearAbstract:We utilized a Bayesian strategy that relied on external fossil calibrations in the perciform fish clade Centrarchidae to time-calibrate the mtDNA phylogeny, individual gene trees inferred from each of the ten nuclear genes and a phylogeny inferred from the concatenation of ten nuclear genes, and a phylogeny inferred from the concatenation of ten nuclear and two mitochondrial genes in BEAST. We also calibrated divergence times on a nuclear species tree using *BEAST, excluding the mitochondrial genes to avoid incongruence among gene trees resulting from mitochondrial replacement via introgressive hybridization that is common among species of Ceasia. The xml files were generated in BEAUti, however the species tree divergence time xml file were also changed by hand. All samples were collected in the field and accession numbers for each gene accompany this dryad submissio
Phillip M. Harris - One of the best experts on this subject based on the ideXlab platform.
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interspecific relationships and the evolution of sexual dimorphism in pygmy sunfishes Centrarchidae elassoma
Molecular Phylogenetics and Evolution, 2014Co-Authors: Michael W Sandel, Fritz C Rohde, Phillip M. HarrisAbstract:The genus Elassoma represents a small but unique component of the aquatic biodiversity hotspot in southeastern North America. We present the first phylogeny of the seven described species, corroborated by sequence data from mitochondrial and nuclear protein coding genes. This analysis reveals a Coastal Plain clade sister to the geographically isolated, and federally protected, Elassoma alabamae. The Coastal Plain clade contains the widespread E. zonatum, which is sister to a clade primarily restricted to lowland Neogene subprovinces. We analyzed morphometric data in a phylogenetic context to illustrate the evolution of sexual shape dimorphism within the genus. Sixteen univariate and three multivariate traits were tested for significant sexual dimorphism for each species, and relative transformation rates were inferred from the time tree. A simple index of interspecific sexual dimorphism revealed greater disparity among sympatric species comparisons than among allopatric comparisons. Results implicate geology as a primary factor influencing ecological diversification, and sexual selection as a mechanism reinforcing reproductive isolation in areas of secondary contact. We discuss putative roles of geological history and sexual selection in the generation and maintenance of the aquatic biodiversity gradient in southeastern North America.
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Congeneric phylogeographical sampling reveals polyphyly and novel biodiversity within black basses (Centrarchidae: Micropterus)
Biological Journal of the Linnean Society, 2011Co-Authors: Justin C. Bagley, Kevin J. Roe, Richard L. Mayden, W. Holznagel, Phillip M. HarrisAbstract:For groups of animals with limited or unstable taxonomic resolution, congeneric phylogeographical sampling represents a way to potentially increase resolution of species limits and internal branches during phylogenetic inference. We investigated species limits and whether there was better support for hypothesized relationships among Micropterus (black basses) using wide geographical sampling. Bayesian and maximum likelihood estimates of Micropterus phylogeny including 205 mitochondrial DNA cytochrome b (1140 bp) sequences (150 haplotypes) representing eight extant species and one subspecies recovered eight well-supported clades. Haplotypes from fish identified as Micropterus coosae, Micropterus henshalli, Micropterus punctulatus, Micropterus salmoides, and Micropterus treculii created eight forms of broad-sense polyphyly in the tree, which we hypothesized were the result of incomplete lineage sorting and hybridization-mediated introgression (natural and anthropogenic, i.e. associated with stocking). Our findings mostly agree with hypothesized relationships. However, they provide a more complex view of Micropterus biodiversity, highlighting population-level processes. Our data also provide a useful guide for expanding character sampling (nuclear loci and morphology) to evaluate the history, distinctiveness, and geographical distributions of genetic lineages within and among black basses. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 346–363.
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Systematics and Zoogeography of the Rock Basses (Centrarchidae: Ambloplites)
Copeia, 2008Co-Authors: Kevin J. Roe, Richard L. Mayden, Phillip M. HarrisAbstract:Abstract This study examines the role that historical events have played in the diversification of members of the genus Ambloplites by estimating divergence times of clades within the genus. DNA sequences of the mitochondrial cytochrome b gene were used to develop phylogenetic hypotheses for Ambloplites using maximum parsimony and Bayesian methods. The timing of diversification within and between species of Ambloplites was estimated using nonparametric rate-smoothing and penalized likelihood methods calibrated by fossil dates. Monophyly of three of the four species was supported. The ages of the most recent common ancestors of species of Ambloplites estimated in this study confirm earlier estimates that in most instances, their origins occurred prior to the Pleistocene. A comparison of estimated divergence times of lineages to sea level fluctuations indicates a correspondence to extremely high or low sea stands throughout the Neogene Period. Populations of Ambloplites in the Ozarks and Ouachita highlands ...
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A mitochondrial DNA perspective on the molecular systematics of the sunfish genus Lepomis (Actinopterygii: Centrarchidae)
Copeia, 2005Co-Authors: Phillip M. Harris, Richard L. MaydenAbstract:Abstract Complete mitochondrial DNA cytochrome b gene sequences from 56 specimens representing all 12 species of Lepomis were used to examine phylogenetic relationships within the genus. Results supported the monophyly of Lepomis and all previously recognized subgenera, except Eupomotis, but there was no support for previously proposed relationships among subgenera. Seven species were recovered as monophyletic lineages, while five species (L. auritus, L. macrochirus, L. marginatus, L. miniatus, and L. symmetricus) were recovered as either poly- or paraphyletic or were placed as parts of unresolved polytomies with other species. Parametric bootstrapping tests rejected monophyly for only two of the five species (L. auritus and L. symmetricus). Without additional data, including increased geographic sampling and a comparable nuclear gene phylogeny, it is not possible to determine whether the failure to support monophyly for these two species reflects the presence of cryptic species or results from hybridization.
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phylogenetic relationships of the genera of north american sunfishes and basses percoidei Centrarchidae as evidenced by the mitochondrial cytochrome b gene
Copeia, 2002Co-Authors: Kevin J. Roe, Phillip M. Harris, Richard L. MaydenAbstract:Abstract The phylogenetic relationships of genera of the family Centrarchidae and its affinities to the Elassomatidae were examined using the mitochondrial DNA sequences of the cytochrome b gene. A total of 32 individuals representing 16 species from nine genera of centrarchids were sequenced. Outgroup were drawn from other perciform families including several families previously proposed to be closely related to the Centrarchidae. Phylogenetic analysis was conducted using the optimality criteria of maximum parsimony with two weighting schemes and using the maximum likelihood method. A priori and a posteriori alternative hypotheses of relationships within the Centrarchidae were investigated using the Shimodaira and Hasegawa Test. The results of all analyses support the monophyly of the Centrarchidae, although the interrelationships of centrarchid genera differed between analyses. Elassoma was never recovered as the sister taxon to the Centrarchidae; however, the sister relationship of these taxa could not...
Peter C Wainwright - One of the best experts on this subject based on the ideXlab platform.
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scaling of in vivo muscle velocity during feeding in the largemouth bass micropterus salmoides Centrarchidae
Physiological and Biochemical Zoology, 2011Co-Authors: Andrew M Carroll, Peter C WainwrightAbstract:AbstractMany vertebrates undergo large increases in body size over the course of a lifetime, and these increases are often accompanied by changes in morphological and physiological parameters. For instance, in most animals, increases in size with growth are accompanied by decreases in the maximum speed of shortening (Vmax) in locomotor muscles. Curiously, in muscles involved in suction feeding, Vmax shows no decreases with size in vitro, despite the fact that timing of kinematic events involved in suction feeding (e.g., time to peak gape) slow with increased size. The goal of this study was to examine whether muscular speed in vivo varies with size during suction feeding in the largemouth bass (Micropterus salmoides). The dorsal epaxial musculature of 10 individual bass (varying from 123 to 685 g and from 18.1 to 32.0 cm standard length [SL]) was implanted with sonometric crystals to measure muscle length during feeding on elusive prey (large goldfish). No relationship was found between the mean individua...
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fossil calibrations and molecular divergence time estimates in centrarchid fishes teleostei Centrarchidae
Evolution, 2005Co-Authors: Thomas J Near, Daniel I. Bolnick, Peter C WainwrightAbstract:Molecular clock methods allow biologists to estimate divergence times, which in turn play an important role in comparative studies of many evolutionary processes. It is well known that molecular age estimates can be biased by heterogeneity in rates of molecular evolution, but less attention has been paid to the issue of potentially erroneous fossil calibrations. In this study we estimate the timing of diversification in Centrarchidae, an endemic major lineage of the diverse North American freshwater fish fauna, through a new approach to fossil calibration and molecular evolutionary model selection. Given a completely resolved multi-gene molecular phylogeny and a set of multiple fossil-inferred age estimates, we tested for potentially erroneous fossil calibrations using a recently developed fossil cross-validation. We also used fossil information to guide the selection of the optimal molecular evolutionary model with a new fossil jackknife method in a fossil-based model cross-validation. The centrarchid phylogeny resulted from a mixed-model Bayesian strategy that included 14 separate data partitions sampled from three mtDNA and four nuclear genes. Ten of the 31 interspecific nodes in the centrarchid phylogeny were assigned a minimal age estimate from the centrarchid fossil record. Our analyses identified four fossil dates that were inconsistent with the other fossils, and we removed them from the molecular dating analysis. Using fossil-based model cross-validation to determine the optimal smoothing value in penalized likelihood analysis, and six mutually consistent fossil calibrations, the age of the most recent common ancestor of Centrarchidae was 33.59 million years ago (mya). Penalized likelihood analyses of individual data partitions all converged on a very similar age estimate for this node, indicating that rate heterogeneity among data partitions is not confounding our analyses. These results place the origin of the centrarchid radiation at a time of major faunal turnover as the fossil record indicates that the most diverse lineages of the North American freshwater fish fauna originated at the Eocene-Oligocene boundary, approximately 34 mya. This time coincided with major global climate change from warm to cool temperatures and a signature of elevated lineage extinction and origination in the fossil record across the tree of life. Our analyses demonstrate the utility of fossil cross-validation to critically assess individual fossil calibration points, providing the ability to discriminate between consistent and inconsistent fossil age estimates that are used for calibrating molecular phylogenies.
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investigating phylogenetic relationships of sunfishes and black basses actinopterygii Centrarchidae using dna sequences from mitochondrial and nuclear genes
Molecular Phylogenetics and Evolution, 2004Co-Authors: Thomas J Near, Daniel I. Bolnick, Peter C WainwrightAbstract:Abstract The 32 species of the Centrarchidae are ecologically important components of the diverse fish communities that characterize North American freshwater ecosystems. In spite of a rich history of systematic investigations of centrarchid fishes there is extensive conflict among previous hypotheses that may be due to restricted taxon or character sampling. We present the first phylogenetic analysis of the Centrarchidae that combines DNA sequence data from both the mitochondrial and nuclear genomes and includes all described species. Gene sequence data were collected from a complete mtDNA protein coding gene (NADH subunit 2), a nuclear DNA intron (S7 ribosomal protein intron 1), and a portion of a nuclear DNA protein-coding region (Tmo-4C4). Phylogenetic trees generated from analysis of the three-gene dataset were used to test alternative hypotheses of centrarchid relationships that were gathered from the literature. Four major centrarchid lineages are present in trees generated in maximum parsimony (MP) and Bayesian maximum likelihood analyses (BML). These lineages are Acantharchus pomotis, Micropterus, Lepomis, and a clade containing Ambloplites, Archoplites, Centrarchus, Enneacanthus, and Pomoxis. Phylogenetic trees resulting from MP and BML analyses are highly consistent but differ with regard to the placement of A. pomotis. Significant phylogenetic incongruence between mtDNA and nuclear genes appears to result from different placement of Micropterus treculi, and is not characteristic of relationships in all other parts of the centrarchid phylogeny. Slightly more than half of the 27 previously proposed hypotheses of centrarchid relationships were rejected based on the Shomodaira–Hasegawa test.
Daniel I. Bolnick - One of the best experts on this subject based on the ideXlab platform.
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Intergeneric Spawning Between Captive Female Sacramento Perch (Archoplites interruptus) and Male Rock Bass (Ambloplites rupestrus), Teleostei: Centrarchidae
The American Midland Naturalist, 2006Co-Authors: Daniel I. Bolnick, Chris E. MillerAbstract:Abstract The North American freshwater fish family Centrarchidae is well known for extensive natural hybridization, but there are no reports of voluntary spawning between genera. We document courtship and spawning in an aquarium between two separate pairs of a male Rock Bass (Ambloplites rupestris) and a female Sacramento Perch (Archoplites interruptus). One trial resulted in a low frequency of fertilized eggs, but these did not survive beyond the blastula stage. Fossil and molecular evidence suggests that these species have been isolated for at least 15 million years, so this spawning implies that courtship among species can persist longer during species divergence than previously appreciated.
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tempo of hybrid inviability in centrarchid fishes teleostei Centrarchidae
Evolution, 2005Co-Authors: Daniel I. Bolnick, Thomas J NearAbstract:Hybrid viability decreases with divergence time, a pattern consistent with a so-called speciation clock. However, the actual rate at which this clock ticks is poorly known. Most speciation-clock studies have used genetic divergence as a proxy for time, adopting a molecular clock and often far-distant calibration points to convert genetic distances into age. Because molecular clock assumptions are violated for most genetic datasets and distant calibrations are of questionable utility, the actual rate at which reproductive isolation evolves may be substantially different than current estimates suggest. We provide a robust measure of the tempo at which hybrid viability declines with divergence time in a clade of freshwater fishes (Centrarchidae). This incompatibility clock is distinct from a speciation clock because speciation events in centrarchids appear to be driven largely by prezygotic isolation. Our analyses used divergence times estimated with penalized likelihood applied to a phylogeny derived from seven gene regions and calibrated with six centrarchid fossils. We found that hybrid embryo viability declined at mean rate of 3.13% per million years, slower than in most other taxa investigated to date. Despite measurement error in both molecular estimated ages and hatching success of hybrid crosses, divergence time explained between 73% and 90% of the variation in hybrid viability among nodes. This high correlation is consistent with the gradual accumulation of many genetic incompatibilities of small effect. Hybrid viability declined with the square of time, consistent with an increasing rate of accumulation of incompatibilities between divergent genomes (the snowball effect). However, the quadratic slope is due to a lag phase resulting from heterosis among young species pairs, a phenomenon rarely considered in predictions of hybrid fitness. Finally, we found that reciprocal crosses often show asymmetrical hybrid viabilities. We discuss several alternative explanations for this result including possible deleterious cytonuclear interactions. Speciation-clock studies have been a small cottage industry recently, but there are still novel insights to be gained from analyses of more taxonomic groups. However, between-group comparisons require more careful molecular-clock calibration than has been the norm.
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fossil calibrations and molecular divergence time estimates in centrarchid fishes teleostei Centrarchidae
Evolution, 2005Co-Authors: Thomas J Near, Daniel I. Bolnick, Peter C WainwrightAbstract:Molecular clock methods allow biologists to estimate divergence times, which in turn play an important role in comparative studies of many evolutionary processes. It is well known that molecular age estimates can be biased by heterogeneity in rates of molecular evolution, but less attention has been paid to the issue of potentially erroneous fossil calibrations. In this study we estimate the timing of diversification in Centrarchidae, an endemic major lineage of the diverse North American freshwater fish fauna, through a new approach to fossil calibration and molecular evolutionary model selection. Given a completely resolved multi-gene molecular phylogeny and a set of multiple fossil-inferred age estimates, we tested for potentially erroneous fossil calibrations using a recently developed fossil cross-validation. We also used fossil information to guide the selection of the optimal molecular evolutionary model with a new fossil jackknife method in a fossil-based model cross-validation. The centrarchid phylogeny resulted from a mixed-model Bayesian strategy that included 14 separate data partitions sampled from three mtDNA and four nuclear genes. Ten of the 31 interspecific nodes in the centrarchid phylogeny were assigned a minimal age estimate from the centrarchid fossil record. Our analyses identified four fossil dates that were inconsistent with the other fossils, and we removed them from the molecular dating analysis. Using fossil-based model cross-validation to determine the optimal smoothing value in penalized likelihood analysis, and six mutually consistent fossil calibrations, the age of the most recent common ancestor of Centrarchidae was 33.59 million years ago (mya). Penalized likelihood analyses of individual data partitions all converged on a very similar age estimate for this node, indicating that rate heterogeneity among data partitions is not confounding our analyses. These results place the origin of the centrarchid radiation at a time of major faunal turnover as the fossil record indicates that the most diverse lineages of the North American freshwater fish fauna originated at the Eocene-Oligocene boundary, approximately 34 mya. This time coincided with major global climate change from warm to cool temperatures and a signature of elevated lineage extinction and origination in the fossil record across the tree of life. Our analyses demonstrate the utility of fossil cross-validation to critically assess individual fossil calibration points, providing the ability to discriminate between consistent and inconsistent fossil age estimates that are used for calibrating molecular phylogenies.
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investigating phylogenetic relationships of sunfishes and black basses actinopterygii Centrarchidae using dna sequences from mitochondrial and nuclear genes
Molecular Phylogenetics and Evolution, 2004Co-Authors: Thomas J Near, Daniel I. Bolnick, Peter C WainwrightAbstract:Abstract The 32 species of the Centrarchidae are ecologically important components of the diverse fish communities that characterize North American freshwater ecosystems. In spite of a rich history of systematic investigations of centrarchid fishes there is extensive conflict among previous hypotheses that may be due to restricted taxon or character sampling. We present the first phylogenetic analysis of the Centrarchidae that combines DNA sequence data from both the mitochondrial and nuclear genomes and includes all described species. Gene sequence data were collected from a complete mtDNA protein coding gene (NADH subunit 2), a nuclear DNA intron (S7 ribosomal protein intron 1), and a portion of a nuclear DNA protein-coding region (Tmo-4C4). Phylogenetic trees generated from analysis of the three-gene dataset were used to test alternative hypotheses of centrarchid relationships that were gathered from the literature. Four major centrarchid lineages are present in trees generated in maximum parsimony (MP) and Bayesian maximum likelihood analyses (BML). These lineages are Acantharchus pomotis, Micropterus, Lepomis, and a clade containing Ambloplites, Archoplites, Centrarchus, Enneacanthus, and Pomoxis. Phylogenetic trees resulting from MP and BML analyses are highly consistent but differ with regard to the placement of A. pomotis. Significant phylogenetic incongruence between mtDNA and nuclear genes appears to result from different placement of Micropterus treculi, and is not characteristic of relationships in all other parts of the centrarchid phylogeny. Slightly more than half of the 27 previously proposed hypotheses of centrarchid relationships were rejected based on the Shomodaira–Hasegawa test.
Jeffrey R Baylis - One of the best experts on this subject based on the ideXlab platform.
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male body size and paternal behaviour in smallmouth bass micropterus dolomieui pisces Centrarchidae
Animal Behaviour, 1995Co-Authors: Daniel D Wiegmann, Jeffrey R BaylisAbstract:Male smallmouth bass defend nest sites and progeny after spawning. Females may consequently discriminate between potential mates with respect to characters that indicate paternal quality. Survivorship of offspring was previously found to be positively related to the site tenacity of a male following a disturbance at the nest. In this study, a comparison of the behaviour of 462 males over four spawning seasons indicated that both body size and the developmental stage of offspring in nests influenced male guarding behaviour. Large males were more site-tenacious than small males following a human disturbance at the nest, but the strength of the association differed between spawning seasons. Males that were guarding eggs at the time of intrusion were more tenacious than males that were guarding larvae, suggesting the higher ventilation requirements of eggs may motivate males to assume higher risks of injury. Male tenacity depended neither on the date of the spawning season on which male behaviour was evaluated, male age, nor the number of offspring defended after accounting for male body size and the developmental stage of offspring. Male body size could thus provide female M. dolomieui with an a priori indicator of the paternal quality of potential mates. Comparisons of male mortality indicated that the cost of reproduction did not depend on body size and that large parental males suffered a higher reproduction-independent mortality than small parental males. Size-dependent mortality could consequently favour a relatively higher investment into current progeny by large males. Large males should also be capable of a higher absolute investment into current offspring than small males because of size-dependent metabolism and reduced feeding during the period of parental care. Higher absolute investment by large males may explain the apparent female mate preference for large male M. dolomieui and the tendency for females to prefer large males as mates in other fishes with paternal care.
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sexual selection and fitness variation in a population of smallmouth bass micropterus dolomieui pisces Centrarchidae
Evolution, 1992Co-Authors: Daniel D Wiegmann, Jeffrey R Baylis, Michael H HoffAbstract:Monogamy is often presumed to constrain mating variance and restrict the action of sexual selection. We examined the reproductive patterns of a monogamous population of smallmouth bass (Micropterus dolomieui), and attempted to identify sources of within-season fitness variation among females and known-age males. Many males did not acquire a nest site, and many territorial males were unsuccessful in acquiring a mate. The likelihood that territorial males mated depended on several aspects of nest sites. Mated males of age three were larger than the average size of age-three males in the population. The mean sizes of age-four and age-five mated males were not different from the average of same-age males in the population. Thus, selection resulting from the acquisition of a mate favored large size among only age-three males. Timing of nest construction and breeding among territorial males was negatively related to male size and did not depend on male age after taking male size into account. Indirect evidence (numbers of eggs deposited in nests) suggests that the timing of spawning among females was also negatively related to female size. Fertility selection favored early reproduction within the season by males of all ages, but large male size was favored among only age-four males. The combined early breeding of fecund females and female mate choice of large males may explain the positive correlation between the size of age-four males and the number of eggs acquired. Despite large differences of female fecundity, however, the variance of relative mate number contributed about two times more than the variance of relative fertility among females to the total variance of relative fitness within each sex.