The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Gustavo P. Viozzi - One of the best experts on this subject based on the ideXlab platform.
-
la estructura de las comunidades de helmintos de galaxias maculatus Osmeriformes galaxiidae en diferentes sitios de un lago de la patagonia argentina
Ecología Austral, 2015Co-Authors: María Valeria Fernández, Liliana Semenas, Gustavo P. ViozziAbstract:The spatial variation of helminth communities of an aquatic system can be attributed to different biotic and abiotic factors. In South America, this type of studies has not been conducted in freshwater environments. The lake Nahuel Huapi is the largest within the Nahuel Huapi National Park. As it presents a diversity of habitat, this lake offers an ideal environment to identify factors that impact over the helminth communities of Galaxias maculatus (small puyen) at different sites of the lake. In order to analyze these variations, 144 small puyens were captured in five sites of the lake with different environmental characteristics. Community analyses were performed, and composition of communities and abundance of the different species of helminths were related with biotic and abiotic factors of the different sites. The size of the host, shallow littorals with aquatic vegetation, and anthropic impact were the factors that determined the variations in composition and abundance of the component communities of helminths in the prey fish Galaxias maculatus from Nahuel Huapi Lake.
-
parasites of the peladilla aplochiton zebra Osmeriformes galaxiidae from patagonia argentina and chile
Comparative Parasitology, 2012Co-Authors: Valeria Fernandez, Liliana Semenas, Gustavo P. ViozziAbstract:Abstract Aplochiton zebra is found inhabiting lakes and rivers in Patagonia (Chile and Argentina) and the Malvinas Islands (Falklands Islands). The “peladilla” is not commercially fished; thus, not much is known about its biology. In previous studies, 7 parasite species were recorded from this fish species. The aim of the present work is to provide new data of A. zebra parasites from surveys in Argentinean Patagonia and to compile the published information from Argentina and Chile. A total of 217 A. zebra from 5 lakes were collected and 15 parasite species were found: 2 Protozoa, 1 Myxozoa, 6 Digenea, 1 Cestoda, 1 Acanthocephala, 3 Nematoda, and 1 Mollusca. This checklist contributes 11 new records of parasites from A. zebra.
-
Parasites of the “Peladilla,” Aplochiton zebra (Osmeriformes: Galaxiidae), from Patagonia (Argentina and Chile)
Comparative Parasitology, 2012Co-Authors: Valeria Fernandez, Liliana Semenas, Gustavo P. ViozziAbstract:Abstract Aplochiton zebra is found inhabiting lakes and rivers in Patagonia (Chile and Argentina) and the Malvinas Islands (Falklands Islands). The “peladilla” is not commercially fished; thus, not much is known about its biology. In previous studies, 7 parasite species were recorded from this fish species. The aim of the present work is to provide new data of A. zebra parasites from surveys in Argentinean Patagonia and to compile the published information from Argentina and Chile. A total of 217 A. zebra from 5 lakes were collected and 15 parasite species were found: 2 Protozoa, 1 Myxozoa, 6 Digenea, 1 Cestoda, 1 Acanthocephala, 3 Nematoda, and 1 Mollusca. This checklist contributes 11 new records of parasites from A. zebra.
-
metazoan parasites of galaxias maculatus Osmeriformes galaxiidae from argentinean patagonia
Comparative Parasitology, 2009Co-Authors: Gustavo P. Viozzi, Liliana Semenas, Norma Brugni, Veronica FloresAbstract:A checklist, based on bibliographical records and original data from an extensive survey, is presented for the metazoan parasites of Galaxias maculatus (Jenyns, 1842) in Argentinean Patagonia. The checklist includes 33 metazoan parasite entries: 5 myxozoans, 12 digeneans, 2 monogeneans, 3 cestodes, 2 acanthocephalans, 7 nematodes, 1 copepod, and 1 bivalve. Gyrodactylus sp., Pomphorhynchus patagonicus Ortubay, Ubeda, Semenas and Kennedy, 1991, and Hysterothylacium patagonense Moravec, Urawa and Coria, 1997 are reported for the first time from G. maculatus in South America. Although this checklist enlarges the knowledge of G. maculatus parasites, a large portion of Patagonia remains unexplored, and many of its lakes and rivers have never been surveyed for parasites, especially in the southern part of the region.
-
A new genus of Cystidicolid nematode from the stomach of Galaxias maculatus (Osmeriformes: Galaxiidae) in Patagonia (Argentina).
The Journal of parasitology, 2009Co-Authors: Norma Brugni, Gustavo P. Viozzi, María Valeria Fernández, Rocío VegaAbstract:During a parasitological survey of Galaxias maculatus (Jenyns) from Patagonian Andean Lakes, specimens of a new species of nematode were collected from the stomach of fish and studied by light and scanning electron microscopy. This species is described as the only member of a newly proposed genus of Cystidicolidae by having oral opening dorsoventrally elongated, 2 lateral pseudolabia, 4 cephalic papillae, stoma (vestibule) elongated, esophagus divided into anterior muscular and posterior glandular sections, and caudal alae in males. Placonema n. gen. (Habronematoidea, Cystidicolidae) is characterized by the combination of the following features: oral opening dorsoventrally elongated demarcated by 4 sclerotized plates and 2 well-developed pseudolabia projected to the buccal cavity, each pseudolabium with conspicuous, conical, anterior protuberances. Four cephalic papillae and deirids simple. Male with caudal alae, area rugosa absent, 4 pairs of preanal papillae, unpaired papilla present on anterior cloacal lip, and 6 pairs of postanal papillae. Larvigerous eggs without filaments. Placonema pataguense n. gen. n. sp. infects the stomach of G. maculatus from Lake Patagua (Patagonia, Argentina) and is the first species of Cystidicolidae described from G. maculatus.
Liliana Semenas - One of the best experts on this subject based on the ideXlab platform.
-
la estructura de las comunidades de helmintos de galaxias maculatus Osmeriformes galaxiidae en diferentes sitios de un lago de la patagonia argentina
Ecología Austral, 2015Co-Authors: María Valeria Fernández, Liliana Semenas, Gustavo P. ViozziAbstract:The spatial variation of helminth communities of an aquatic system can be attributed to different biotic and abiotic factors. In South America, this type of studies has not been conducted in freshwater environments. The lake Nahuel Huapi is the largest within the Nahuel Huapi National Park. As it presents a diversity of habitat, this lake offers an ideal environment to identify factors that impact over the helminth communities of Galaxias maculatus (small puyen) at different sites of the lake. In order to analyze these variations, 144 small puyens were captured in five sites of the lake with different environmental characteristics. Community analyses were performed, and composition of communities and abundance of the different species of helminths were related with biotic and abiotic factors of the different sites. The size of the host, shallow littorals with aquatic vegetation, and anthropic impact were the factors that determined the variations in composition and abundance of the component communities of helminths in the prey fish Galaxias maculatus from Nahuel Huapi Lake.
-
parasites of the peladilla aplochiton zebra Osmeriformes galaxiidae from patagonia argentina and chile
Comparative Parasitology, 2012Co-Authors: Valeria Fernandez, Liliana Semenas, Gustavo P. ViozziAbstract:Abstract Aplochiton zebra is found inhabiting lakes and rivers in Patagonia (Chile and Argentina) and the Malvinas Islands (Falklands Islands). The “peladilla” is not commercially fished; thus, not much is known about its biology. In previous studies, 7 parasite species were recorded from this fish species. The aim of the present work is to provide new data of A. zebra parasites from surveys in Argentinean Patagonia and to compile the published information from Argentina and Chile. A total of 217 A. zebra from 5 lakes were collected and 15 parasite species were found: 2 Protozoa, 1 Myxozoa, 6 Digenea, 1 Cestoda, 1 Acanthocephala, 3 Nematoda, and 1 Mollusca. This checklist contributes 11 new records of parasites from A. zebra.
-
Parasites of the “Peladilla,” Aplochiton zebra (Osmeriformes: Galaxiidae), from Patagonia (Argentina and Chile)
Comparative Parasitology, 2012Co-Authors: Valeria Fernandez, Liliana Semenas, Gustavo P. ViozziAbstract:Abstract Aplochiton zebra is found inhabiting lakes and rivers in Patagonia (Chile and Argentina) and the Malvinas Islands (Falklands Islands). The “peladilla” is not commercially fished; thus, not much is known about its biology. In previous studies, 7 parasite species were recorded from this fish species. The aim of the present work is to provide new data of A. zebra parasites from surveys in Argentinean Patagonia and to compile the published information from Argentina and Chile. A total of 217 A. zebra from 5 lakes were collected and 15 parasite species were found: 2 Protozoa, 1 Myxozoa, 6 Digenea, 1 Cestoda, 1 Acanthocephala, 3 Nematoda, and 1 Mollusca. This checklist contributes 11 new records of parasites from A. zebra.
-
metazoan parasites of galaxias maculatus Osmeriformes galaxiidae from argentinean patagonia
Comparative Parasitology, 2009Co-Authors: Gustavo P. Viozzi, Liliana Semenas, Norma Brugni, Veronica FloresAbstract:A checklist, based on bibliographical records and original data from an extensive survey, is presented for the metazoan parasites of Galaxias maculatus (Jenyns, 1842) in Argentinean Patagonia. The checklist includes 33 metazoan parasite entries: 5 myxozoans, 12 digeneans, 2 monogeneans, 3 cestodes, 2 acanthocephalans, 7 nematodes, 1 copepod, and 1 bivalve. Gyrodactylus sp., Pomphorhynchus patagonicus Ortubay, Ubeda, Semenas and Kennedy, 1991, and Hysterothylacium patagonense Moravec, Urawa and Coria, 1997 are reported for the first time from G. maculatus in South America. Although this checklist enlarges the knowledge of G. maculatus parasites, a large portion of Patagonia remains unexplored, and many of its lakes and rivers have never been surveyed for parasites, especially in the southern part of the region.
-
Do environmental differences between lakes in northwestern Argentinean Patagonia affect the infection of Philureter trigoniopsis (monogenea) in Galaxias maculatus (Osmeriformes)
The Journal of parasitology, 2009Co-Authors: Gustavo P. Viozzi, Liliana SemenasAbstract:Philureter trigoniopsis is the only parasite found in the ureters and urinary bladder of Galaxias maculatus in Patagonian Andean lakes. The dynamics of this endoparasitic monogenean were studied in Lake Gutierrez, a body of water with scarce shoreline vegetation, where the host has an annual cycle of migration to the deep pelagic zone of the lake. To compare variations of the infection related to differences between lakes, G. maculatus specimens were sampled monthly with baited traps from September 1998 to November 1999 in Lake Moreno, which is an oligotrophic body of water with emergent shoreline vegetation and where the fish do not migrate to the deep pelagic areas of the lake. In addition, data for summer infections of P. trigoniopsis from 10 Andean Patagonian lakes that differ in aquatic vegetation, depth, and area were compared. In Lake Moreno prevalence of P. trigoniopsis showed a seasonal pattern, with 1-yr-old fish exhibiting the highest values of prevalence and mean intensity. Negative correlations between water temperature and prevalence and between age of fish and abundance were found. Our results suggest that age of fish may be the main factor structuring the distribution of P. trigoniosis in populations of G. maculatus. At the regional level the relationship between the infection and the characteristics of the lakes was also observed, with prevalence and mean intensity of P. trigoniopsis in G. maculatus higher in large deep lakes without macrophytes.
Jonathan M Waters - One of the best experts on this subject based on the ideXlab platform.
-
Genetic diversity in New Zealand Galaxias vulgaris sensu lato (Teleostei: Osmeriformes: Galaxiidae): a test of a biogeographic hypothesis
Journal of Biogeography, 2008Co-Authors: Graham P. Wallis, Jonathan M Waters, Karen F. Judge, Julie Bland, Tim M. BerraAbstract:Aim To test whether a geologically recent region with low endemism shows low genetic diversity in a freshwater fish species complex, in contrast to an adjacent area with high diversity. The low endemism is generally postulated to be the combined effect of Pleistocene glaciations and the unstable nature of the recent gravel outwash from young mountains to the west. This rock aggradation has formed a plain, crossed by several braided rivers. The faunas of these rivers have the potential to interchange through flooding or course changes. Location Southern and central South Island, New Zealand (NZ). We define the boundary of these two biogeographical regions as the Waitaki River, the most southerly braided river. To the north lies the Canterbury Plain, formed from coalesced alluvial fans; to the south is the Otago peneplain and associated mountain ranges. Methods Previous work has revealed considerable genetic structuring in the stream-resident fish Galaxias vulgaris Stokell sensu lato, including a species complex in the southern region of South Island, NZ. Using isozyme electrophoresis, we have now examined genetic variation among a total of 58 samples of non-migratory river galaxias from 24 river systems in South Island: 16 in the central region and eight to the south. Results Whereas samples from the central region do exhibit significant genetic structuring (Wright’s FST=0.331), they are more genetically homogeneous (mean Nei’s D= 0.032) than populations to the south of the Waitaki River (FST=0.826, mean D=0.374). Main conclusions The results concur with our expectations of differences between the central and southern regions. We suggest that the divergence in the south reflects geological stability, whereas relatively shallow divergences within the central region reflects the more recent formation of the Canterbury Plain and its unstable braided rivers. The genetic structuring of this group has been promoted by the absence of the marine juvenile phase that is found in five other members of the genus native to NZ. This diversity of the southern region mirrors its diverse flora and invertebrate fauna, and has conservation implications that parallel those resulting from our improved knowledge of the NZ herpetofauna through the application of genetic analysis.
-
evolution and biogeography of new zealand s longjaw galaxiids Osmeriformes galaxiidae the genetic effects of glaciation and mountain building
Freshwater Biology, 2008Co-Authors: Jonathan M Waters, D CrawAbstract:Summary 1. The biological impact of glaciation in Southern Hemisphere freshwaters is poorly understood. Several large rivers of eastern South Island, New Zealand, represent a mosaic of glaciated and non-glaciated regions, and are thus well-suited for studies of post-glacial recolonization. 2. We conducted mtDNA analyses of South Island's endemic non-migratory longjaw galaxiids Galaxias prognathus and G. cobitinis (Osmeriformes: Galaxiidae) to test hypotheses of post-glacial recolonization, and to assess the vicariant effects of Pleistocene mountain building. 3. We analysed the phylogeography of longjaw cytochrome b sequences from 38 sites in central South Island (n = 83). On the basis of our sampling it seems that G. prognathus and G. cobitinis have a parapatric distribution in the Waitaki River system, their disjunction broadly coinciding with three large post-glacial lakes. Waitaki clades of both species are deeply divergent relative to conspecific taxa in drainages to the north and south. 4. Tests for recent population growth – predicted under post-glacial expansion of G. prognathus– do not refute recent recolonization of streams above glaciated lakes in the Waitaki River drainage. The apparent absence of potential ‘source’ populations from non-glaciated regions suggests a post-glacial population decline for G. prognathus below the Waitaki lakes. 5. Molecular clock calibrations based on several freshwater vicariant events elsewhere in New Zealand supported the geologically-derived hypothesis of Waitaki–Canterbury drainage isolation approximately 300 ka.
-
Phylogenetics of the australasian mudfishes : Evolution of an eel-like body plan
Molecular phylogenetics and evolution, 2005Co-Authors: Jonathan M Waters, Robert M. McdowallAbstract:The mudfish genus Neochanna (Osmeriformes: Galaxiidae) contains six species that exhibit varying degrees of morphological and ecological adaptation to life in swampy conditions. Here, we present the first molecular phylogenetic analysis (16S rRNA+cytochrome b; 1681bp) of the entire genus to (1) test for monophyly of Australian and New Zealand taxa and (2) elucidate morphological character evolution. In addition, we analyse a matrix of 21 morphological characters to test for congruence between mitochondrial DNA and morphology, and to examine total evidence under a Bayesian framework. Molecular data indicate that the diadromous Tasmanian mudfish, N. cleaveri, is sister to a clade of five non-diadromous New Zealand mudfishes. Mapping of morphological characters onto the molecular phylogeny suggests an evolutionary transition from a plesiomorphic "stream" galaxiid morphotype to a more specialised "anguilliform" galaxiid morphotype. Pelvic fins have become increasingly reduced and dorsal, anal, and caudal fins are increasingly confluent. Associated with these changes are elongated nostrils, reduced eyes, and increased anterior cranial ossification. Morphological and total evidence analyses yield similar or identical topologies, respectively. The phylogenetic distribution of diadromy in Neochanna is consistent with a single loss of this character state in New Zealand. However, the strong sister relationship (3.6% divergent; 100% bootstrap support) detected between non-diadromous N. burrowsius (South Island, NZ) and N. rekohua (Chatham Islands) indicates geologically recent dispersal across 850km of ocean. Diadromy may therefore have been retained in the common ancestor of these two mudfish species, and subsequently lost from both lineages.
-
cladogenesis and loss of the marine life history phase in freshwater galaxiid fishes Osmeriformes galaxiidae
Evolution, 2001Co-Authors: Jonathan M Waters, Graham P. WallisAbstract:Abstract Switches from migratory (diadromous) to nonmigratory (freshwater) life histories are known to have occurred repeatedly in some aquatic taxa. However, the significance of the loss of diadromy as an initiator for speciation remains poorly understood. The rivers of New Zealand's South Island house a species flock of recently derived nonmigratory galaxiid fishes known as the Galaxias vulgaris complex. Members of this complex are morphologically and genetically similar to the diadromous G. brevipinnis found in New Zealand and southeastern Australia. We hypothesised that South Island's G. vulgaris complex (at least 10 nonmigratory lineages) represents a number of independent radiations from a migratory G. brevipinnis stock, with repeated loss of diadromy. Sequence data were obtained for 31 ingroup samples (G. vulgaris complex and G. brevipinnis) plus four outgroup taxa. A well-resolved phylogeny based on 5039 base pairs of the mitochondrial genome suggests that diadromy has been lost on three separate ...
-
CLADOGENESIS AND LOSS OF THE MARINE LIFE-HISTORY PHASE IN FRESHWATER GALAXIID FISHES (Osmeriformes: GALAXIIDAE)
Evolution; international journal of organic evolution, 2001Co-Authors: Jonathan M Waters, Graham P. WallisAbstract:Switches from migratory (diadromous) to nonmigratory (freshwater) life histories are known to have occurred repeatedly in some aquatic taxa. However, the significance of the loss of diadromy as an initiator for speciation remains poorly understood. The rivers of New Zealand's South Island house a species flock of recently derived nonmigratory galaxiid fishes known as the Galaxias vulgaris complex. Members of this complex are morphologically and genetically similar to the diadromous G. brevipinnis found in New Zealand and southeastern Australia. We hypothesised that South Island's G. vulgaris complex (at least 10 nonmigratory lineages) represents a number of independent radiations from a migratory G. brevipinnis stock, with repeated loss of diadromy. Sequence data were obtained for 31 ingroup samples (G. vulgaris complex and G. brevipinnis) plus four outgroup taxa. A well-resolved phylogeny based on 5039 base pairs of the mitochondrial genome suggests that diadromy has been lost on three separate occasions. Thus, speciation in these galaxiid fishes is partly an incidental phenomenon caused by switches from diadromous to nonmigratory strategies. However, much of the subsequent nonmigratory diversity is monophyletic, suggesting that drainage evolution (vicariance) has also played a major role in cladogenesis. Levels of sequence divergence among major ingroup lineages (1.6-12.7%) suggest that the radiation is considerably older relative to Northern Hemisphere (postglacial) complexes of salmonid, osmerid, and gasterosteid fishes. Sympatric taxa are not monophyletic, suggesting that their coexistence reflects secondary contact rather than sympatric speciation. The monophyly of New Zealand G. brevipinnis is well supported, but both mitochondrial DNA and nuclear sequences indicate that G. brevipinnis is paraphyletic on an intercontinental scale. The divergence (maximum 11.5%) between Tasmanian and New Zealand G. brevipinnis, although large, supports marine dispersal rather than vicariance as the principle biogeographic mechanism on an intercontinental scale.
Graham P. Wallis - One of the best experts on this subject based on the ideXlab platform.
-
Extreme positive selection on a new highly-expressed larval glycoprotein (LGP) gene in Galaxias fishes (Osmeriformes: Galaxiidae)
Molecular biology and evolution, 2010Co-Authors: Lise J. Wallis, Graham P. WallisAbstract:We describe the intron–exon structure and DNA/protein sequences of a new larval glycoprotein (LGP) gene from nine species of galaxiid fish. The gene has a distant similarity to Danio THP (Tamm–Horsfall urinary glycoprotein; uromodulin) and cichlid SPP120 (seminal plasma glycoprotein) due to conserved features of its zona pellucida (ZP) domain, including eight highly conserved cysteines and a consensus furin cleavage site. Using a combination of 454 sequencing of cDNA and exon-primed intron-spanning sequencing of genomic DNA, we obtained full sequences of the coding region (996 bp) and its intervening sequences (1,459 bp). LGP shows an exceptionally strong signal of positive selection over the entire coding region, as evidenced by dN/dS values .1. Across nine species of Galaxias, 87/332 (26%) amino acid residues are variable, compared with 9/386 (2%) for mitochondrial cytochrome b (cytb) in the same group of species. Across 36 interspecific pairwise comparisons, genetic distances are in all cases larger for coding region than for introns, by a factor of 2.4-fold on average. Reading frame, gene structure, splice sites, and many ZP motifs are conserved across all species. Together with the fact that the gene is expressed in all species, these results argue clearly against the possibility of a pseudogene. We show by 454 sequencing and quantitative polymerase chain reaction that the transcript is abundant (ca. 0.5%) in newly hatched larvae and appears to be almost absent from a range of adult tissues. We postulate that the strong Darwinian evolution exhibited by this protein may reflect some type of immunoprotection at this vulnerable larval stage.
-
Genetic diversity in New Zealand Galaxias vulgaris sensu lato (Teleostei: Osmeriformes: Galaxiidae): a test of a biogeographic hypothesis
Journal of Biogeography, 2008Co-Authors: Graham P. Wallis, Jonathan M Waters, Karen F. Judge, Julie Bland, Tim M. BerraAbstract:Aim To test whether a geologically recent region with low endemism shows low genetic diversity in a freshwater fish species complex, in contrast to an adjacent area with high diversity. The low endemism is generally postulated to be the combined effect of Pleistocene glaciations and the unstable nature of the recent gravel outwash from young mountains to the west. This rock aggradation has formed a plain, crossed by several braided rivers. The faunas of these rivers have the potential to interchange through flooding or course changes. Location Southern and central South Island, New Zealand (NZ). We define the boundary of these two biogeographical regions as the Waitaki River, the most southerly braided river. To the north lies the Canterbury Plain, formed from coalesced alluvial fans; to the south is the Otago peneplain and associated mountain ranges. Methods Previous work has revealed considerable genetic structuring in the stream-resident fish Galaxias vulgaris Stokell sensu lato, including a species complex in the southern region of South Island, NZ. Using isozyme electrophoresis, we have now examined genetic variation among a total of 58 samples of non-migratory river galaxias from 24 river systems in South Island: 16 in the central region and eight to the south. Results Whereas samples from the central region do exhibit significant genetic structuring (Wright’s FST=0.331), they are more genetically homogeneous (mean Nei’s D= 0.032) than populations to the south of the Waitaki River (FST=0.826, mean D=0.374). Main conclusions The results concur with our expectations of differences between the central and southern regions. We suggest that the divergence in the south reflects geological stability, whereas relatively shallow divergences within the central region reflects the more recent formation of the Canterbury Plain and its unstable braided rivers. The genetic structuring of this group has been promoted by the absence of the marine juvenile phase that is found in five other members of the genus native to NZ. This diversity of the southern region mirrors its diverse flora and invertebrate fauna, and has conservation implications that parallel those resulting from our improved knowledge of the NZ herpetofauna through the application of genetic analysis.
-
cladogenesis and loss of the marine life history phase in freshwater galaxiid fishes Osmeriformes galaxiidae
Evolution, 2001Co-Authors: Jonathan M Waters, Graham P. WallisAbstract:Abstract Switches from migratory (diadromous) to nonmigratory (freshwater) life histories are known to have occurred repeatedly in some aquatic taxa. However, the significance of the loss of diadromy as an initiator for speciation remains poorly understood. The rivers of New Zealand's South Island house a species flock of recently derived nonmigratory galaxiid fishes known as the Galaxias vulgaris complex. Members of this complex are morphologically and genetically similar to the diadromous G. brevipinnis found in New Zealand and southeastern Australia. We hypothesised that South Island's G. vulgaris complex (at least 10 nonmigratory lineages) represents a number of independent radiations from a migratory G. brevipinnis stock, with repeated loss of diadromy. Sequence data were obtained for 31 ingroup samples (G. vulgaris complex and G. brevipinnis) plus four outgroup taxa. A well-resolved phylogeny based on 5039 base pairs of the mitochondrial genome suggests that diadromy has been lost on three separate ...
-
CLADOGENESIS AND LOSS OF THE MARINE LIFE-HISTORY PHASE IN FRESHWATER GALAXIID FISHES (Osmeriformes: GALAXIIDAE)
Evolution; international journal of organic evolution, 2001Co-Authors: Jonathan M Waters, Graham P. WallisAbstract:Switches from migratory (diadromous) to nonmigratory (freshwater) life histories are known to have occurred repeatedly in some aquatic taxa. However, the significance of the loss of diadromy as an initiator for speciation remains poorly understood. The rivers of New Zealand's South Island house a species flock of recently derived nonmigratory galaxiid fishes known as the Galaxias vulgaris complex. Members of this complex are morphologically and genetically similar to the diadromous G. brevipinnis found in New Zealand and southeastern Australia. We hypothesised that South Island's G. vulgaris complex (at least 10 nonmigratory lineages) represents a number of independent radiations from a migratory G. brevipinnis stock, with repeated loss of diadromy. Sequence data were obtained for 31 ingroup samples (G. vulgaris complex and G. brevipinnis) plus four outgroup taxa. A well-resolved phylogeny based on 5039 base pairs of the mitochondrial genome suggests that diadromy has been lost on three separate occasions. Thus, speciation in these galaxiid fishes is partly an incidental phenomenon caused by switches from diadromous to nonmigratory strategies. However, much of the subsequent nonmigratory diversity is monophyletic, suggesting that drainage evolution (vicariance) has also played a major role in cladogenesis. Levels of sequence divergence among major ingroup lineages (1.6-12.7%) suggest that the radiation is considerably older relative to Northern Hemisphere (postglacial) complexes of salmonid, osmerid, and gasterosteid fishes. Sympatric taxa are not monophyletic, suggesting that their coexistence reflects secondary contact rather than sympatric speciation. The monophyly of New Zealand G. brevipinnis is well supported, but both mitochondrial DNA and nuclear sequences indicate that G. brevipinnis is paraphyletic on an intercontinental scale. The divergence (maximum 11.5%) between Tasmanian and New Zealand G. brevipinnis, although large, supports marine dispersal rather than vicariance as the principle biogeographic mechanism on an intercontinental scale.
Guangchun Lei - One of the best experts on this subject based on the ideXlab platform.
-
A multilocus phylogeny of Asian noodlefishes Salangidae (Teleostei: Osmeriformes) with a revised classification of the family.
Molecular phylogenetics and evolution, 2011Co-Authors: Li Guo, Rong Xia, Guangchun LeiAbstract:A group of small and transparent Asian noodlefishes (Osmeriformes: Salangidae) are commercially important fishery species, however, interrelationships among these fishes remain unresolved in previous studies using mitochondrial markers. We re-examine phylogenetic relationships of Salangidae by including complete taxon sampling, based on seven nuclear loci and one mitochondrial gene using a multilocus coalescence-based species-tree method. Our results show a well-resolved phylogeny of Salangidae that does not agree with previous hypotheses. The topology test suggests that our hypothesis represents the most likely phylogeny. Using the inferred species-tree as criterion, we recombine the rank of subfamilies and genera in the Salangidae, and erect a new genus Neosalangichthys. Our revised classification of Salangidae is well supported by reinterpreting previously proposed diagnostic characters. Finally, re-defined synapomorphic characters are used to erect a key to the genera of Salangidae.
-
Phylogenetic position of the enigmatic Lepidogalaxias salamandroides with comment on the orders of lower euteleostean fishes
Molecular phylogenetics and evolution, 2010Co-Authors: Rong Xia, J. Andrés López, Robert M. Mcdowall, Guangchun LeiAbstract:This study examines phylogenetic placement of the enigmatic Western Australian Lepidogalaxias, and extends previous studies by including eight new taxa to enable re-examination phylogenetic relationships of lower euteleostean fishes at the ordinal level, based on mitochondrial genomes from 39 ingroup taxa and 17 outgroups. Our results suggest that Lepidogalaxias occupies a basal position among all euteleosts, in contrast with earlier hypotheses that variously suggested a closer relationship to esocid fishes, or to the galaxiid Lovettia. In addition our evidence shows that Osmeriformes should be restricted Retropinnidae, Osmeridae, Plecoglossidae and Salangidae. This reduced Osmeriformes is supported in our results as the sister group of Stomiiformes. Galaxiidae, which is often closely linked to Osmeriformes, emerges as sister group of a combined Osmeriformes, Stomiiformes, Salmoniformes, Esociformes and Argentiformes, and we give Galaxiiformes the rank of order to include all remaining galaxioid fishes (Galaxias and allied taxa, Aplochiton and Lovettia). Our results also support a sister group relationship between Salmoniformes and Esociformes, which are together the sister group of Argentiniformes.