An empirical test of freshwater vicariance via river capture

River capture is a geomorphological process through which stream sections are displaced from one catchment to another, and it may represent a dominant facilitator of interdrainage transfer and cladogenesis in freshwater-limited taxa. However, few studies have been conducted in a manner to explicitly test the biological significance of river capture. Here we present a multispecies phylogeographical analysis to test whether the nonmigratory fish fauna of the Von River (South Island, New Zealand) is the product of a well-documented, Late Quaternary capture of a section of the Oreti River (Southland drainage). Specifically, we predict that nonmigratory fishes of the Von River will exhibit closer genetic affinities with those of Southland, rather than those of the Clutha system, into which the Von River presently drains. Mitochondrial DNA phylogeography (control region and cytochrome b sequence data) and analysis of nuclear orthologues of mtDNA sequences indicate that 'flathead'Galaxias of the Von River (n = 31, three sites) have greatest genetic affinities with those of Southland (Galaxias 'southern', n = 216, 38 sites), rather than with those of the Clutha River (Galaxias sp. 'D', n = 73, 32 sites). Likewise, Von River 'roundhead'Galaxias (n = 52, four sites) have greatest genetic affinities with those of Southland drainages (Galaxias gollumoides, n = 223, 58 sites), rather than with those of the Clutha River (Galaxias pullus, Galaxias anomalus, Galaxias gollumoides of the Nevis tributary; n = 68, 32 sites). These findings are consistent with our predictions that genetic affinities of the nonmigratory fish fauna in the Von River would reflect past, rather than present, drainage connections. Consequently, river capture is responsible for the nonmigratory fish fauna of the Von River. In a broader context, river capture has frequently influenced the distribution of genetic lineages among catchments in New Zealand freshwater-limited fish, and its biogeographical significance may have been underestimated in other regions.     

Mitochondrial DNA phylogenetics of the Galaxias vulgaris complex from South Island, New Zealand: rapid radiation of a species flock

Mitochondrial control region sequence variation was examined in the Galaxias vulgaris complex, a group of freshwater-limited galaxiid fishes endemic to South Island, New Zealand. Phylogenetic analyses were used to test the monophyly of seven non-migratory ( G. vulgaris complex) and one migratory ( G. brevipinnis ) species. Newly-described taxa, some diagnosed on the basis of subtle differences in morphology, are associated with strongly monophyletic mtDNA lineages. Although the current taxonomy is supported generally, sequence data suggest that Southland G. anomalus should be attributed to G. gollumoides , whereas Southland and Stewart Island G. depressiceps represent a new southern lineage. Molecular clock calibrations suggest that migratory and non-migratory forms, separated by a maximum of 6·4% sequence divergence, diverged no earlier than the mid-late Pliocene. Biogeographical implications of high diversity (eight lineages) in the south (Otago-Southland) and low diversity (one lineage) in central South Island (Canterbury) are discussed. The unresolved relationships among species may reflect a rapid evolutionary radiation, essentially a star phylogeny.     

Genetic and morphological evidence for reproductive isolation between sympatric populations of Galaxias (Teleostei: Galaxiidae) in South Island, New Zealand

New Zealand's South Island houses a flock of closely related stream-resident fish taxa (Galaxias vulgaris sensu lato), including a number of species recently described on the basis of subtle morphological differences. The taxonomic status of some members of the species complex remains uncertain. This study examines the degree of reproductive isolation between recently recognized morphotypes from Southland (G. 'southern', flatheads; G. gollumoides, roundheads) which co-occur in Bushy Creek, a tributary of the Mataura R. Although these morphotypes are broadly sympatric in Southland and Stewart Island, Bushy Creek is their only documented zone of contact. Molecular (microsatellite, isozyme and mtDNA markers) and morphological analyses of 139 fish samples across a 500-m transect (seven stations) reveal a cline from predominantly G. 'southern' (N=85) to predominantly G. gollumoides (JV=54), corresponding with a gradual increase in stream gradient. Multivariate analyses of genotypic and morphological data independently reveal distinct clusters that are completely congruent with mtDNA type, suggesting an absence of mtDNA introgression. Our data support the separate species status of G. 'southern' and G. gollumoides under both biological and phylogenetic species concepts. We suggest that the speciation of these taxa occurred in allopatry through independent losses of diadromy, with sympatry resulting from secondary contact.     

Introgressive hybridization between Galaxias depressiceps and Galaxias sp D (Teleostei: Galaxiidae) in Otago, New Zealand: Secondary contact mediated by water races

Central Otago (New Zealand) was the focus of an intense period ofgold mining in the late 19th century. Mining relied on high waterpressure for sluicing, often requiring extensive systems of water raceslinking headwaters over large distances. On Rough Ridge, races connectedheadwaters of Otago's two major river systems, the Taieri and theClutha. We employed genetic analysis of freshwater fish(Galaxias) populations to assess the biological implications ofrace-development. The two galaxiid taxa found on Rough Ridge (G. spD and G. depressiceps) are reciprocally monophyletic formtDNA and have three fixed allozyme differences. Rough Ridge aside,G. sp D is apparently absent from the Taieri system and G.depressiceps from the Clutha system. Distributions of mitochondrialDNA, allozyme and microsatellite alleles imply that artificialconnections have facilitated bidirectional introgression: movementof G. sp D alleles into the Taieri system and G.depressiceps alleles into the Clutha. The finding of some identicalcontrol region haplotypes (of both lineages) on either side of thecatchment boundary confirms the recency of genetic exchange. Near theinferred region of contact, samples from Linn Burn (Taieri) are pureG. depressiceps for three diagnostic allozymes and mtDNA.Samples from upper Pool Burn (Clutha) are pure G. sp D forthese same four markers. However, other collections from around thecontact zone represent genetic mixtures forming a cline. We fear thatsimilar human-induced mixing may have happened elsewhere in uplandOtago.     

Geological dates and molecular rates: rapid divergence of rivers and their biotas

We highlight a novel molecular clock calibration system based on geologically dated river reversal and river capture events. Changes in drainage pattern may effect vicariant isolation of freshwater taxa, and thus provide a predictive framework for associated phylogeographic study. As a case in point, New Zealand's Pelorus and Kaituna rivers became geologically isolated from the larger Wairau River system 70 to 130 kyr BP. We conducted mitochondrial DNA phylogeographic analyses of two unrelated freshwater-limited fish taxa native to these river systems (Gobiomorphus breviceps, n = 63; Galaxias divergens, n = 95). Phylogenetic analysis of combined control region and cytochrome b sequences yielded reciprocally monophyletic clades of Pelorus-Kaituna and Wairau haplotypes for each species. Calibrated rates of molecular change based on this freshwater vicariant event are substantially faster than traditionally accepted rates for fishes but consistent with other recent inferences based on geologically young calibration points. A survey of freshwater phylogeographic literature reveals numerous examples in which the ages of recent evolutionary events may have been substantially overestimated through the use of "accepted" calibrations. We recommend that--wherever possible--biologists should start to reassess the conclusions of such studies by using more appropriate molecular calibrations derived from recent geological events.     

Fine‐scale habitat preferences influence within‐river population connectivity: a case‐study using two sympatric New Zealand Galaxias fish species

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River capture, range expansion, and cladogenesis: the genetic signature of freshwater vicariance

River capture is potentially a key geomorphological driver of range expansion and cladogenesis in freshwater-limited taxa. While previous studies of freshwater fish, in particular, have indicated strong relationships between historical river connections and phylogeographic pattern, their analyses have been restricted to single taxa and geological hypotheses were typically constructed a posteriori. Here we assess the broader significance of river capture among taxa by testing multiple species for the genetic signature of a recent river capture event in New Zealand. During the Quaternary an upper tributary of the Clarence River system was diverted into the headwaters of the Wairau River catchment. Mitochondrial DNA (control region and cytochrome b) sequencing of two native galaxiid fishes (Galaxias vulgaris and Galaxias divergens) supports headwater exchange: populations from the Clarence and Wairau Rivers are closely related sister-groups, whereas samples from the geographically intermediate Awatere River are genetically divergent. The upland bully Gobiomorphus breviceps (Eleotridae), in contrast, lacks a genetic signature of the capture event. We hypothesize that there is an increased likelihood of observing genetic signatures from river capture events when they facilitate range expansion, as is inferred for the two galaxiid taxa studied here. When river capture merely translocates genetic lineages among established populations, by contrast, we suggest that the genetic signature of capture is less likely to be retained, as might be inferred for G. breviceps. Rates of molecular evolution calibrated against this recent event were elevated relative to traditional estimates, consistent with the contribution of polymorphisms to branch lengths at shallow phylogenetic levels prior to fixation by purifying selection and drift.     

Geological subsidence, river capture, and cladogenesis of galaxiid fish lineages in central New Zealand

We used mtDNA and isozyme analysis of a freshwater fish, Galaxias divergens (Osmeriformes: Galaxiidae), to test a hypothesis of drainage evolution in South Island, New Zealand. Geological evidence indicates that the presently north-flowing Kaituna River branch of the Pelorus River system once flowed south into the Wairau River system. The subsequent flow-reversal is thought to have resulted from Pleistocene subsidence in central New Zealand. mtDNA sequence data corroborated this geological hypothesis: rivers draining into Pelorus Sound were found to retain a genetic lineage of G. divergens that is otherwise restricted to the Wairau River system and adjacent coastal drainages (based on current sampling). Other sampled drainages in northern South Island and southern North Island were found to house lineages that were highly divergent from the Wairau–Pelorus clade. Isozyme data yielded groupings based on fixed differences that were largely congruent with mtDNA clades. Standard molecular calibrations suggest that vicariant isolation of Pelorus and Wairau systems (drainage reversal) occurred in the mid-Pleistocene rather than the late Pleistocene as suggested by geology. Future multidisciplinary analyses will aim to improve our understanding of geological and molecular evolutionary rates.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88 , 367–376.     

Extreme intraspecific mitochondrial DNA sequence divergence in Galaxias maculatus (Osteichthys: Galaxiidae), one of the world's most widespread freshwater fish

Biogeographic controversies surrounding the widespread freshwater fish, Galaxias maculatus, were addressed with DNA sequence data. Mitochondrial cytochrome b and 16S rRNA sequences were obtained from representatives of six populations of this species. Substantial levels of cytochrome b (maximum 14.6%) and 16S rRNA sequence divergence (maximum 6.0%) were detected between western Pacific (Tasmania-New Zealand) and South American (Chile-Falkland Islands) haplotypes. A considerable level of divergence was also detected between Tasmanian and New Zealand haplotypes (maximum 5.1%) and within and among Chilean and Falkland Island G. maculatus (maximum 3. 8%). The phylogenetic structure of haplotypes conflicts with the accepted pattern of continental fragmentation. Molecular clock calibrations suggest that haplotype divergences postdate the fragmentation of Gondwana. These findings point to marine dispersal rather than ancient vicariance as an explanation for the wide distribution. The phylogenetic structure of South American haplotypes was not consistent with their geographic distribution. We consider factors such as population divergence, population size, dispersal, secondary contact, and philopatry as potential causes of the high level of mtDNA nucleotide diversity in this species.     

Biogeography of a southern hemisphere freshwater fish: how important is marine dispersal?

Galaxias maculatus is one of the world's most widely distributed freshwater fish. This species has a marine-tolerant juvenile phase, and a geographical range extending through much of the southern hemisphere. We conducted phylogeographic analyses of 163 control region haplotypes of G. maculatus, including samples from New Zealand (five locations), Tasmania (one location) and Chile (one location). A lack of genetic structure among New Zealand samples suggests that marine dispersal facilitates considerable gene flow on an intra-continental scale. The discovery of a Tasmanian-like haplotype in one of 144 New Zealand samples indicates that inter-continental marine dispersal occurs but is insufficient to prevent mitochondrial DNA differentiation among continents. The sister relationship of Tasmanian and New Zealand clades implies that marine dispersal is an important biogeographical mechanism for this species. However, a vicariant role in the divergence of eastern and western Pacific G. maculatus cannot be rejected.     

Isozyme analysis of Galaxias species (Teleostei: Galaxiidae) from the Taieri River, South Island, New Zealand: a species complex revealed

We examined genetic differentiation among 23 samples of non-migratory river galaxias from 17 streams in the Taieri River system, South Island, New Zealand. Four major genetic types were found, two of which occur in narrow sympatry in one location. These were compared with topotypical material representing Galaxias anomalus from the Clutha system (Otago) and G. vulgaris from the Waimakariri system (Canterbury) in order to establish identity. Morphological examination of these four major genetic types revealed consistent concomitant differences. The results suggest that there are at least three species of river galaxias in the Taieri system: G. anomalus, G. vulgaris and at least one previously undescribed species. We propose that the genetic structuring and subsequent speciation 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 New Zealand. This structuring may be exacerbated by population fragmentation over the last century owing to the negative influence of introduced trout. The phylogenetic diversity within the river system mirrors the diverse flora and invertebrate fauna of the region, and has conservation implications that parallel those resulting from our improved knowledge of the New Zealand 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

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.     

Variation in Life History of Land-Locked Lacustrine and Riverine Populations of Galaxias maculatus (Jenyns 1842) in Western Australia

Galaxias maculatus is one of the most naturally widely distributed species in the world yet there is no published literature on the biology of Western Australian populations. Galaxias maculatus in the rivers of the south coast of Western Australia inhabit an environment that is variable and at times unpredictable. By examining trends in gonadal development, lengths at first maturity, growth and appearance and persistence of larvae of G. maculatus in two saline rivers (Jerdacuttup River and Oldfield River) and one freshwater lake (Moates Lake), the life histories of populations in contrasting environments were determined. The stable conditions that prevail in the low salinity, cool waters of Moates Lake have fostered an extremely protracted breeding and larval recruitment period (year round) in comparison to limited recruitment in the riverine environments which experience less predictable flow events and water quality (salinity). An upstream migration for breeding in the Jerdacuttup and Oldfield rivers is similar to land-locked G. maculatus in south-eastern Australia and is a reversal of the downstream migration in Moates Lake or populations with marine larval dispersal, i.e. diadromous populations. Differences in population demographics existed between these habitats, with smaller maximum sizes and significantly smaller sizes at maturation occurring in the rivers compared to the lake. In Moates Lake approximately 93, 6 and 1% were 0+, 1+ and 2+, respectively; while cohort progression in the rivers suggests that most fish do not live beyond their first year. As an adaptable opportunist, G. maculatus can modify its life history strategy at a local level to persist in varied and sometimes unpredictable environments.     

Phylogeography of the freshwater fish, Mogurnda adspersa, in streams of northeastern Queensland, Australia: evidence for altered drainage patterns

A phylogeographic survey was used to elucidate the relative roles of historical processes and contemporary gene flow in structuring the genetic pattern observed with Mogurnda adspersa. This species of freshwater fish is found in the rivers and streams of the northeastern highlands of Queensland, Australia. Specifically, this project focused on populations in the Tully and Herbert Rivers in the Atherton Tablelands. Sequence analysis indicated that three distinct clades exist in the headwaters of the Tully River. The population sampled from one of the Tully River streams (Cheetah Creek) contained haplotypes that displayed ≈ 3.4% sequence divergence from other haplotypes detected in this river. Furthermore, these haplotypes formed part of the clade which exists throughout not only the Herbert River but other surrounding drainages in the area. These results support the hypothesis that the current genetic structure is strongly affected by changes in drainage patterns due to geomorphological processes that occurred in the recent past.     

中国北鳅谱系地理学分析

北鳅(Lefua costata)为冷水性鱼类,分布于淮河以北,分析遗传结构能够反映其适应环境变迁的响应.基于线粒体D-loop区211条序列分析了我国北鳅的谱系地理学和遗传多样性,样本采自9条水系共18个样点.单倍型分析显示共计55个单倍型,呈高单倍型多样性(h=0.9304)和高核苷酸多样性(π=0.0087).单...     

Patterns of genomic divergence and introgression between Japanese stickleback species with overlapping breeding habitats

With only a few absolute geographic barriers in marine environments, the factors maintaining reproductive isolation among marine organisms remain elusive. However, spatial structuring in breeding habitat can contribute to reproductive isolation. This is particularly important for marine organisms that migrate to use fresh‐ or brackish water environments to breed. The Japanese Gasterosteus stickleback species, the Pacific Ocean three‐spined stickleback (G. aculeatus) and the Japan Sea stickleback (G. nipponicus) overwinter in the sea, but migrate to rivers for spawning. Although they co‐occur at several locations across the Japanese islands, they are reproductively isolated. Our previous studies in Bekanbeushi River showed that the Japan Sea stickleback spawns in the estuary, while the Pacific Ocean stickleback mainly spawns further upstream in freshwater. Overall genomic divergence was very high with many interspersed regions of introgression. Here, we investigated genomic divergence and introgression between the sympatric species in the much shorter Tokotan River, where they share spawning sites. The levels of genome‐wide divergence were reduced and introgression was increased, suggesting that habitat isolation substantially contributes to a reduction in gene flow. We also found that genomic regions of introgression were largely shared between the two systems. Furthermore, some regions of introgression were located near loci with a heterozygote advantage for juvenile survival. Taken together, introgression may be partially driven by adaptation in this system. Although, the two species remain clearly genetically differentiated. Regions with low recombination rates showed especially low introgression. Speciation reversal is therefore likely prevented by barriers other than habitat isolation.     

Reproductive biology, species status and taxonomic relationships of four recently discovered galaxiid fishes in a New Zealand river

The reproductive biology of four recently discovered, largely allopatric non-migratory Galaxias species in the Taieri River, New Zealand, was compared with the closely related Galaxias vulgaris . Timing of spawning was similar (late winter/spring) but spawning habitat, spawning behaviour and nest structure differed among the Taieri species and G. vulgaris . Patterns of fecundity also differed among the Taieri species but, with G. vulgaris , they form a distinct group of galaxiids with maxima of 800–1500 eggs having diameters of 2·3–2·8 μn. The different spawning behaviours of the Taieri galaxiids, in particular the differences in spawning orientation, provide evidence for prezygotic isolating mechanisms and support their status as separate species. In cladistics terms, the results indicate that Galaxias anomalus, G. eldoni and G. vulgaris are sister taxa, while G. depressiceps and Galaxias sp. form a second cluster.     

The cyprinodont fish Rivulus (Aplocheiloidei: Rivulidae) in Trinidad and Tobago: molecular evidence for marine dispersal, genetic isolation and local differentiation

Mitochondrial DNA sequences (756 bp) were obtained from the cytochrome b gene of 36 Rivulus individuals collected from 10 sites in Trinidad and one site in Tobago. Eight haplotypes were identified. Low genetic divergence (0.5%) between one western Trinidad (Blue Basin) haplotype and Rivulus hartii from north-western Venezuela (Paria peninsula) and high genetic divergence ( c. 11%) between these and the remaining other Trinidad and Tobago haplotypes suggests that the islands were colonized by two lineages. The commoner haplotype is distributed throughout lowland Trinidad, possibly a reflection of flooding of the Orinoco River leading to high dispersal between watersheds. Rivulus from higher altitude (Northern Range) localities that would not have been affected by such flooding show high genetic divergence between sites. The genetic differentiation between northern and southern watersheds suggests isolation between some of these drainages.     

Landscape genetic patterns of the rainbow darter Etheostoma caeruleum: a catchment analysis of mitochondrial DNA sequences and nuclear microsatellites

Catchment population structure and divergence patterns of the rainbow darter Etheostoma caeruleum (Percidae: Teleostei), an eastern North American benthic fish, are tested using a landscape genetics approach. Allelic variation at eight nuclear DNA microsatellite loci and two mitochondrial DNA regions [cytochrome (cyt) b gene and control region; 2056 aligned base pairs (bp)] is analysed from 89 individuals and six sites in the Lake Erie catchment (Blanchard, Chagrin, Cuyahoga and Grand Rivers) v. the Ohio River catchment (Big Darby Creek and Little Miami River). Genetic and geographic patterning is assessed using phylogenetic trees, pair‐wise F_ST analogues, AMOVA partitioning, Mantel regression, Bayesian assignment, 3D factorial correspondence and barrier analyses. Results identify 34 cyt b haplotypes, 22 control region haplotypes and 137 microsatellite alleles whose distributions demonstrate marked genetic divergence between populations from the Lake Erie and Ohio River catchments. Etheostoma caeruleum populations in the Lake Erie and Ohio River catchments diverged c. 1·6 mya during the Pleistocene glaciations. Greater genetic separations characterize the Ohio River populations, reflecting their older habitat age and less recent connectivity. Divergence levels within the Lake Erie catchment denote more recent post‐glacial origins. Notably, the western Lake Erie Blanchard River population markedly differs from the three central basin tributary samples, which are each genetically distinguishable using microsatellites. Overall relationships among the Lake Erie sites refute a genetic isolation by geographic distance hypothesis. Etheostoma caeruleum populations thus exchange few genes and have low migration among tributaries and catchments.     

Threatened native freshwater fishes in Australia–some case histories

Case histories of some of Australia's most threatened native freshwater fishes are presented. These include: six endangered species, Galaxias fontanus, G. johnsroni, G. pedderensis (Galaxiidae), Melanataenia euchamensis (Melanotaeniidae), Maccullochella sp. nov. and M. macquariensis (Percichthyidae): one vulnerable species, Galaxias tanycephalus: two potentially threatened species. Galaxias parvus and Prototroctes maraena (Prototroctidae); one indeterminate species. Maccllochella sp.; one restricted species, Macquaria australasica (Percichthyidae). Aspects of their taxonomy, distribution and reasons for their decline are discussed. Conservation management strategies that have been or are being applied to most of these species include protection of the fish and their habitats, establishment of refuge populations, and artificial propagation and re-establishment programmes.