Molecular phylogenetics and biogeography of galaxiid fishes (Osteichthyes: Galaxiidae): dispersal, vicariance, and the position of Lepidogalaxias salamandroides.
TL;DR: The species-rich genus Galaxias is shown to be polyphyletic and the generic taxonomy of the Galaxiinae is reassessed in the light of phylogenetic relationships, and the loss of this migratory phase may be a major cause of speciation.
Abstract: The galaxiid fishes exhibit a gondwanan distribution. We use mitochondrial DNA sequences to test conflicting vicariant and dispersal biogeographic hypotheses regarding the Southern Hemisphere range of this freshwater group. Although phylogenetic resolution of cytochrome b and 16S rRNA sequences is largely limited to more recent divergences, our data indicate that the radiation can be interpreted as several relatively recent dispersal events superimposed on an ancient gondwanan radiation. Genetic relationships contradict the findings of recent morphological analyses of galaxioid fishes. In particular, we examine several hypotheses regarding phylogenetic placement of the enigmatic Lepidogalaxias. Although most workers consider Lepidogalaxias to be an unusual scaled member of the Southern Hemisphere galaxioids, it has also been suggested that this species is related to the Northern Hemisphere esocoids. Our data strongly suggest that this species is not a galaxiid, and the alternative hypothesized esocoid relationship cannot be rejected. The species-rich genus Galaxias is shown to be polyphyletic and the generic taxonomy of the Galaxiinae is reassessed in the light of phylogenetic relationships. Juvenile saltwater-tolerance is phylogenetically distributed throughout the Galaxiinae, and the loss of this migratory phase may be a major cause of speciation.
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TL;DR: The molecular data strongly support the monophyly of salangid fishes, the inclusion ofsalangids in the Osmeridae, and the sister group relationship between salangids and osmerids, and suggest that Plecoglossus can be separated from all the other salangIDS and osMERids.
21 citations
TL;DR: Morphometrics and amplified fragment length polymorphisms were used to examine interspecific differentiation and intraspecific variation in two closely related freshwater fishes (Galaxias ’southern’ and G. gollumoides), suggesting strong reproductive barriers and supporting species status.
Abstract: Morphometrics and amplified fragment length polymorphisms (AFLPs) were used to examine interspecific differentiation and intraspecific variation in two closely related freshwater fishes (Galaxias ’southern’ and G. gollumoides) using sympatric and allopatric populations. The two species were strongly differentiated across all populations, showing 19/24 distinctive morphological features and six fully diagnostic AFLPs. Morphological segregation was principally associated with G. ’southern’ having a larger upper jaw and smaller eye, suggesting that these characters may be useful for field discrimination. No hybridisation was observed between these two fishes, suggesting strong reproductive barriers and supporting species status. Both species showed intraspecific morphological variation among catchments, especially for traits associated with head and mouth morphology. Additionally, G. gollumoides showed intraspecific morphological variation among sites within two streams. Both species showed intraspe...
21 citations
Cites background from "Molecular phylogenetics and biogeog..."
...Genetic divergence associated with drainage evolution has been found in these and other closely related galaxiids (Waters et al. 2000; Wallis et al. 2001; Waters et al. 2001a; Waters & Wallis 2001; Burridge et al. 2006; Waters et al. 2006)....
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TL;DR: While no adult hybrids were detected in the study population, analysis of male broods indicates that interspecies mating is occurring between the two species, and suggests that hybridization may be common in sympatric species of Syngnathus.
Abstract: Hybridization is thought to be an important source of novel genetic variation, and interspecific hybridization may increase the adaptive potential of wild populations. While hybridization has not been previously reported in syngnathid fishes (seahorses and pipefish), the sympatric occurrence of closely related species at high densities increases the probability of interspecies mating in this group. Southern California is home to five species of Syngnathus pipefish, and these species frequently co-occur in near-shore eelgrass beds along the California coast. Recent work has identified exceptionally high levels of genetic diversity in southern populations of Syngnathus leptorhynchus, a widespread species which ranges from Mexico to Alaska. Microsatellite genotyping and mitochondrial sequence data are used here to study the population genetics of S. leptorhynchus and S. auliscus at a site in San Diego Bay where they are found to co-occur at high densities. While no adult hybrids were detected in the study population, analysis of male broods indicates that interspecies mating is occurring between the two species. The lack of premating isolating mechanisms between these two relatives suggests that hybridization may be common in sympatric species of Syngnathus.
19 citations
Cites background or methods from "Molecular phylogenetics and biogeog..."
...2 (a) Secondary structure model of Syngnathus leptorhynchus 16S rRNA after a model for Galaxias brevipinnis (Waters et al. 2000) constructed using xrna 1.1.12beta (Weiser & Noller 1995)....
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...2 (a) Secondary structure model of Syngnathus leptorhynchus 16S rRNA after a model for Galaxias brevipinnis (Waters et al. 2000) constructed using xrna 1....
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...2a; Waters et al. 2000)....
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...© 2006 Blackwell Publishing Ltd, Molecular Ecology, 15, 809–824 data for other members of the genus Syngnathus according to a teleost secondary structure model (Fig. 2a; Waters et al. 2000)....
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TL;DR: Galaxiid species occupy an enormous latitudinal gradient, show a wide variety of life history patterns and are the southernmost native freshwater fishes of the world as discussed by the authors, and played a major role in the postglacial colonization of Andean lakes and streams, and contributes key species to the food webs.
Abstract: South American galaxiids occupy both Patagonia and the ichthyogeographic Chilean Province, encompassing glacial Andean deep lakes, shallow plateau lakes, reservoirs, short Pacific rivers and long Atlantic rivers. The total fish fauna includes 29 species, comprising Neotropical fishes (siluriforms and characids), galaxiids, percichthyids, atherinopsids and mugilids, two lamprey species, and several exotic fishes (salmonids, Gambusia spp. and common carp). The family Galaxiidae shares a common ancestry with the Gondwanan temperate fish fauna, played a major role in the post-glacial colonization of Andean lakes and streams, and contributes key species to the food webs. Galaxiid species occupy an enormous latitudinal gradient, show a wide variety of life history patterns and are the southernmost native freshwater fishes of the world. Knowledge of South American galaxiids has improved notably, but new challenges arise due to climate change, biological invasions, damming, aquaculture and contamination. In this changing environment, the future of South American galaxiids should be carefully considered as a legacy of the old Gondwana and a unique attribute of the freshwaters of southern South America.
18 citations
Cites background from "Molecular phylogenetics and biogeog..."
...The high genetic diversity observed among Piedra Buena (Table S2) individuals suggests that this is a large population, and the possibility of a genetic exchange with other diadromous populations should not be discarded [72]; for example, populations in Tierra del Fuego [63,73,74] and along the Chilean coast [13]....
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TL;DR: Galaxias maculatus, is a gourmet fish of great commercial importance with overexploited fisheries, so, studies of its biology are essential in studying its biology.
Abstract: Galaxias maculatus (Jenyns, 1842) es un pez gourmet de importancia comercial cuyas pesquerias estan sobre-explotadas, siendo esencial el estudio de su biologia para desarrollar su tecnologia de cultivo (galaxicultura), que se encuentra en etapa piloto. Los objetivos de este trabajo son: 1) entregar una sintesis de la informacion de la literatura sobre la biologia de la especie, y 2) identificar la carencia de conocimiento cientifico y puntos criticos para el desarrollo de su tecnologia de cultivo comercial. G. maculatus es un pequeno pez carnivoro, con poblaciones eurihalinas diferenciadas en diadromicas y dulceacuicolas. Las poblaciones diadromicas desovan en los estuarios y la larva migra al mar, retornando a la edad de seis meses para metamorfosearse en adulto. Son escasos los estudios de su sistematica, poblaciones y estado larvario en aguas chilenas, pero los correspondientes a alimentacion, reproduccion y enfermedades son mas numerosos. Las hembras de un ano desovan, aproximadamente, 1.200 huevos adhesivos pero un numero importante muere despues del primer desove (40%). La especie tiene un crecimiento rapido (1,1% dia -1 ) y alto metabolismo, con un promedio de vida de dos anos. Se puede cultivar en cautividad, desovar, incubar sus huevos y obtener larvas; los adultos comen starter pelletizado de salmon y crecen en estanques. El protozoo ciliado Ichtyophthirius multifilis (ich) produce altas mortalidades, en ejemplares en cautiverio, que pueden ser controladas con banos de sal. Los problemas de investigacion a resolver para una futura piscicultura comercial son: identificar y seleccionar las poblaciones adecuadas para cultivo, aumentar el numero de huevos desovados por hembra, desarrollar alimentos para larvas y reproductores, y controlar las enfermedades ectoparasitarias. El punto critico es la masificacion de la produccion mediante el mejoramiento de las tecnicas de reproduccion y larvicultura.
18 citations
Cites background from "Molecular phylogenetics and biogeog..."
...La Tribu Galaxiini se caracteriza por la ausencia de escamas y aleta adiposa (Waters et al., 2000)....
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...…La clasificación taxonómica de Galaxias maculatus (Jenyns, 1842), de acuerdo a Johnson & Patterson (1996), Arratia (1981) y Waters et al. (2000), es la siguiente: Orden Osmeriformes, Suborden Osmeroidei, Superfamilia Galaxioidea, Familia Galaxiidae, Subfamilia Galaxiinae,…...
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...Actualmente, se reconoce a G. maculatus como una sola especie compleja y polimórfica que posee en su área de distribución al menos dos razas o formas eurihalinas: una dulceacuícola y otra diadrómica (McDowall, 1972, 1976a; Johnson & Patterson, 1996; Waters & Burridge, 1999; Waters et al., 2000)....
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..., 2001), lo cuál ha sido corroborado con un enfoque molecular (Johnson & Patterson, 1996; Waters & Burridge, 1999; Waters et al., 2000)....
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...…1971a, 1971b; McDowall, 1968a, 1970, 1971, 1972, 1976a, 1976b; 1988, 2003b; McDowall & Eldon, 1980; Campos, 1972, 1973, 1974, 1979a, 1979b, 1985; Ferriz et al., 2001), lo cuál ha sido corroborado con un enfoque molecular (Johnson & Patterson, 1996; Waters & Burridge, 1999; Waters et al., 2000)....
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References
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TL;DR: The sensitivity of the commonly used progressive multiple sequence alignment method has been greatly improved and modifications are incorporated into a new program, CLUSTAL W, which is freely available.
Abstract: The sensitivity of the commonly used progressive multiple sequence alignment method has been greatly improved for the alignment of divergent protein sequences. Firstly, individual weights are assigned to each sequence in a partial alignment in order to down-weight near-duplicate sequences and up-weight the most divergent ones. Secondly, amino acid substitution matrices are varied at different alignment stages according to the divergence of the sequences to be aligned. Thirdly, residue-specific gap penalties and locally reduced gap penalties in hydrophilic regions encourage new gaps in potential loop regions rather than regular secondary structure. Fourthly, positions in early alignments where gaps have been opened receive locally reduced gap penalties to encourage the opening up of new gaps at these positions. These modifications are incorporated into a new program, CLUSTAL W which is freely available.
63,427 citations
TL;DR: The recently‐developed statistical method known as the “bootstrap” can be used to place confidence intervals on phylogenies and shows significant evidence for a group if it is defined by three or more characters.
Abstract: The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data. In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
40,349 citations
TL;DR: Some examples were worked out using reported globin sequences to show that synonymous substitutions occur at much higher rates than amino acid-altering substitutions in evolution.
Abstract: Some simple formulae were obtained which enable us to estimate evolutionary distances in terms of the number of nucleotide substitutions (and, also, the evolutionary rates when the divergence times are known). In comparing a pair of nucleotide sequences, we distinguish two types of differences; if homologous sites are occupied by different nucleotide bases but both are purines or both pyrimidines, the difference is called type I (or “transition” type), while, if one of the two is a purine and the other is a pyrimidine, the difference is called type II (or “transversion” type). Letting P and Q be respectively the fractions of nucleotide sites showing type I and type II differences between two sequences compared, then the evolutionary distance per site is K = — (1/2) ln {(1 — 2P — Q) }. The evolutionary rate per year is then given by k = K/(2T), where T is the time since the divergence of the two sequences. If only the third codon positions are compared, the synonymous component of the evolutionary base substitutions per site is estimated by K'S = — (1/2) ln (1 — 2P — Q). Also, formulae for standard errors were obtained. Some examples were worked out using reported globin sequences to show that synonymous substitutions occur at much higher rates than amino acid-altering substitutions in evolution.
26,016 citations
TL;DR: A computationally feasible method for finding such maximum likelihood estimates is developed, and a computer program is available that allows the testing of hypotheses about the constancy of evolutionary rates by likelihood ratio tests.
Abstract: The application of maximum likelihood techniques to the estimation of evolutionary trees from nucleic acid sequence data is discussed. A computationally feasible method for finding such maximum likelihood estimates is developed, and a computer program is available. This method has advantages over the traditional parsimony algorithms, which can give misleading results if rates of evolution differ in different lineages. It also allows the testing of hypotheses about the constancy of evolutionary rates by likelihood ratio tests, and gives rough indication of the error of the estimate of the tree.
13,111 citations
01 Jan 1969
10,262 citations