Cladogenesis and loss of the marine life-history phase in freshwater galaxiid fishes (Osmeriformes: Galaxiidae)

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.     

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.     

GENES MEET GEOLOGY: FISH PHYLOGEOGRAPHIC PATTERN REFLECTS ANCIENT, RATHER THAN MODERN, DRAINAGE CONNECTIONS

Abstract We used DNA analysis of the freshwater Galaxias vulgaris complex (Pisces: Galaxiidae) to test a geological hypothesis of drainage evolution in South Island, New Zealand. Geological evidence suggests that the presently north-flowing Nevis River branch of the Clutha/Kawarau River system (Otago) once flowed south into the Nokomai branch of the Mataura system (Southland). The flow reversal is thought to have resulted from fault and fold activity associated with post-Miocene uplift. Mitochondrial DNA sequence data (control region and cytochrome b genes; 76 individuals; maximum divergence 7.1%) corroborate this geomorphological hypothesis: The Nevis River retains a freshwater fish species ( Galaxias gollumoides ; five sites; 10 haplotypes) that is otherwise restricted to Southland (nine sites; 15 haplotypes). There is no indication that the Nevis River lineage of G. gollumoides lives elsewhere in the Clutha/Kawarau system (> 30 sites). Likewise, two widespread Clutha lineages ( G. 'sp' D; G. anomalus–G. pullus ) are apparently absent from the Nevis (> 30 sites). In particular, G. 'sp D' lives throughout much of the Clutha (12 sites, 23 haplotypes), including a tributary of the Kawarau, but is absent from the Nevis itself. Conventional molecular clock calibrations (based on a minimum Nevis-Mataura haplotype divergence of 3.0%) indicate that the Nevis flow reversal may have occurred in the early-mid Pleistocene, which is roughly consistent with geological data. The broad phylogeographic structure evident in the Clutha system is consistent with the sedentary nature of nonmigratory galaxiids. Our study reinforces the value of combining biological and geological data for the formulation and testing of historical hypotheses.     

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.     

Migratory birds have higher prevalence and richness of avian haemosporidian parasites than residents

Individuals of migratory species may be more likely to become infected by parasites because they cross different regions along their route, thereby being exposed to a wider range of parasites during their annual cycle. Conversely, migration may have a protective effect since migratory behaviour allows hosts to escape environments presenting a high risk of infection. Haemosporidians are one of the best studied, most prevalent and diverse groups of avian parasites, however the impact of avian host migration on infection by these parasites remains controversial. We tested whether migratory behaviour influenced the prevalence and richness of avian haemosporidian parasites among South American birds. We used a dataset comprising ~ 11,000 bird blood samples representing 260 bird species from 63 localities and Bayesian multi-level models to test the impact of migratory behaviour on prevalence and lineage richness of two avian haemosporidian genera (Plasmodium and Haemoproteus). We found that fully migratory species present higher parasite prevalence and higher richness of haemosporidian lineages. However, we found no difference between migratory and non-migratory species when evaluating prevalence separately for Plasmodium and Haemoproteus, or for the richness of Plasmodium lineages. Nevertheless, our results indicate that migratory behaviour is associated with an infection cost, namely a higher prevalence and greater variety of haemosporidian parasites.     

Prevalence and diversity of avian hematozoan parasites in Asia: a regional survey

Tissue samples from 699 birds from three regions of Asia (Myanmar, India, and South Korea) were screened for evidence of infection by avian parasites in the genera Plasmodium and Haemoproteus. Samples were collected from November 1994 to October 2004. We identified 241 infected birds (34.0%). Base-on-sequence data for the cytochrome b gene from 221 positive samples, 34 distinct lineages of Plasmodium, and 41 of Haemoproteus were detected. Parasite diversity was highest in Myanmar followed by India and South Korea. Parasite prevalence differed among regions but not among host families. There were four lineages of Plasmodium and one of Haemoproteus shared between Myanmar and India and only one lineage of Plasmodium shared between Myanmar and South Korea. No lineages were shared between India and South Korea, although an equal number of distinct lineages were recovered from each region. Migratory birds in South Korea and India originate from two different migratory flyways; therefore cross-transmission of parasite lineages may be less likely. India and Myanmar shared more host species and habitat types compared to South Korea. Comparison between low-elevation habitat in India and Myanmar showed a difference in prevalence of haematozoans.     

Hierarchical analyses of genetic variation of samples from breeding and feeding grounds confirm the genetic partitioning of northwest Atlantic and South Atlantic populations of swordfish (Xiphias gladius L.)

In species with high migratory potential, the genetic signal revealing population differentiation is often obscured by population admixture. To our knowledge, the explicit comparison of genetic samples from known spawning and feeding areas has not been conducted for any highly migratory pelagic fish species. This study examines the geographic heterogeneity of swordfish mitochondrial DNA (mtDNA) lineages within the Atlantic Ocean using 330 base pairs of sequence of the control region from 480 individuals. Hierarchical analyses of sequence variation were conducted to test whether samples from areas identified as the corresponding spawning and feeding grounds for the northwest (NW) Atlantic (Caribbean and Georges Banks-US northeast) and the South Atlantic (Brazil-Uruguay and Gulf of Guinea), were more closely related to each other than to samples from any other region, including the Mediterranean Sea, the Indian Ocean, and the Pacific Ocean. Phylogeographic analyses reveal that swordfish mtDNA phylogeny is characterized by incomplete lineage sorting and secondary contact of two highly divergent clades. However, despite this complex phylogenetic signature, results from an analysis of nucleotide diversity and from an analysis of molecular variance (AMOVA) were for the most part concordant and indicate that NW Atlantic and South Atlantic swordfish belong to separate populations. The mtDNA distinctiveness of NW Atlantic and South Atlantic swordfish populations is indicative of philopatric behavior in swordfish towards breeding and feeding areas.     

Geographically contrasting biodiversity reductions in a widespread New Zealand seabird

Unravelling prehistoric anthropogenic impacts on biodiversity represents a key challenge for biologists and archaeologists. New Zealand's endemic Stewart Island Shag (Leucocarbo chalconotus) comprises two distinct phylogeographic lineages, currently restricted to the country's south and southeast. However, fossil and archaeological remains suggest a far more widespread distribution at the time of Polynesian settlement ca. 1280 AD, encompassing much of coastal South Island. We used modern and ancient DNA, radiocarbon dating, and Bayesian modelling, to assess the impacts of human arrival on this taxon. Our analyses show that the southeast South Island (Otago) lineage was formerly widespread across coastal South Island, but experienced dramatic population extinctions, range retraction and lineage loss soon after human arrival. By comparison, the southernmost (Foveaux Strait) lineage has experienced a relatively stable demographic and biogeographic history since human arrival, retaining much of its mitochondrial diversity. Archaeological data suggest that these contrasting demographic histories (retraction vs. stability) reflect differential human impacts in mainland South Island vs. Foveaux Strait, highlighting the importance of testing for temporal and spatial variation in human‐driven faunal declines.     

Local parasite lineage sharing in temperate grassland birds provides clues about potential origins of Galapagos avian Plasmodium

Oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. Our aim was to characterize the geographic origins of two Plasmodium parasite lineages detected in the Galapagos Islands and in North American breeding bobolinks (Dolichonyx oryzivorus) that regularly stop in Galapagos during migration to their South American overwintering sites. We used samples from a grassland breeding bird assemblage in Nebraska, United States, and parasite DNA sequences from the Galapagos Islands, Ecuador, to compare to global data in a DNA sequence registry. Homologous DNA sequences from parasites detected in bobolinks and more sedentary birds (e.g., brown‐headed cowbirds Molothrus ater, and other co‐occurring bird species resident on the North American breeding grounds) were compared to those recovered in previous studies from global sites. One parasite lineage that matched between Galapagos birds and the migratory bobolink, Plasmodium lineage B, was the most common lineage detected in the global MalAvi database, matching 49 sequences from unique host/site combinations, 41 of which were of South American origin. We did not detect lineage B in brown‐headed cowbirds. The other Galapagos‐bobolink match, Plasmodium lineage C, was identical to two other sequences from birds sampled in California. We detected a close variant of lineage C in brown‐headed cowbirds. Taken together, this pattern suggests that bobolinks became infected with lineage B on the South American end of their migratory range, and with lineage C on the North American breeding grounds. Overall, we detected more parasite lineages in bobolinks than in cowbirds. Galapagos Plasmodium had similar host breadth compared to the non‐Galapagos haemosporidian lineages detected in bobolinks, brown‐headed cowbirds, and other grassland species. This study highlights the utility of global haemosporidian data in the context of migratory bird–parasite connectivity. It is possible that migratory bobolinks bring parasites to the Galapagos and that these parasites originate from different biogeographic regions representing both their breeding and overwintering sites.     

Cryptic biodiversity and phylogeographical patterns in a snapping shrimp species complex

Recent investigations suggest that marine biodiversity may be much higher than earlier estimates, and an important hidden source of diversity in marine systems is the phenomenon of cryptic species complexes. Such complexes are informative models for research into the evolutionary processes that govern species compositions of marine fauna. The snapping shrimp genera Alpheus and Synalpheus are known to harbour large numbers of cryptic species; here, I characterize the genetic structure of the Alpheus armillatus species complex in the northern Caribbean, west Atlantic, and Gulf of Mexico using mitochondrial and nuclear sequence data. Over this geographical region, the complex harbours at least three lineages that are probable reproductively isolated species; all major lineages diverged subsequent to the close of the Isthmus of Panama. Only one lineage was present in the Gulf of Mexico, whereas outside the Gulf of Mexico there was no clear tendency for lineage dominance by geographical region, as most sites were populated by shrimp from at least two lineages. However, within each lineage, there was strong evidence of population genetic differentiation between geographical regions. All lineages showed strong signals of demographic expansion, and one lineage showed sharply reduced genetic diversity, suggestive of past population bottlenecks or recently founded populations with low gene flow from other sites. These results show that evolutionary processes leading to divergence and speciation have been common and recent in the snapping shrimp, and suggest that connectivity among shrimp populations may be limited.     

Phylogeography of the flathead mullet Mugil cephalus in the north-west Pacific as inferred from the mtDNA control region

The population genetic structure and historical demography of the flathead mullet Mugil cephalus were investigated using the mtDNA control region (CR) sequences (909–1015 bp) of 126 individuals collected from seven locations in the north-west Pacific between 2005 and 2007. Haplotype diversity ( h = 0·9333–1·000) and nucleotide diversity (π = 0·0046–0·1467) varied greatly among the sampling locations. Phylogenetic analysis of the CR sequences indicated that M. cephalus in the north-west Pacific belongs to two highly divergent lineages (lineages 1 and 2), with the inferred population structure being closely associated with the distribution of both lineages. Two populations were identified, one from the East China Sea and the other from the South China Sea. The former samples were obtained from Taiwan and Qingdao of north China and associated with lineage 1 haplotypes. The latter samples were collected from the Philippines, Pearl River of South China and two samples from Japan, all of which were associated with lineage 2. Japanese samples from Okinawa and Yokosuka had different degrees of mixing between lineages 1 and 2. Historical demographic variables in both populations indicated that Pleistocene glaciations had a strong impact on M. cephalus in the north-west Pacific, resulting in a recent demographic decline of the East China Sea population but in demographic equilibrium for the South China Sea population. Japan appears to be a contact zone between lineages 1 and 2, but it may also be indicative of coexistence between resident and migratory populations. Further global studies are required to clarify the taxonomic status of this cosmopolitan species.     

Duck plague epizootics in the United States, 1967-1995

In 1967, the first confirmed diagnosis of duck plague (DP) in the USA was made from pekin ducks (Anas platyrhynchos domesticus) on commercial duck farms on Long Island, New York. Within 10 mo, DP was confirmed as the cause of death in migratory waterfowl on a Long Island bay. This paper reviews 120 DP epizootics reported from 1967 to 1995 that involved waterfowl species native to North America or were reported in areas with free-flying waterfowl at risk. Duck plague epizootics occurred in 21 states with the greatest number reported in Maryland (29), New York (18), California (16), and Pennsylvania (13). The greatest frequency of epizootics (86%) was detected during the months of March to June. At least 40 waterfowl species were affected with the highest frequency of epizootics reported in captive or captive-reared ducks including muscovy ducks (Cairina moschata) (68%), mallard ducks (A. platyrhynchos) (18%) and black ducks (A. rubripes) (14%). The greatest number of waterfowl died in three epizootics that involved primarily migratory birds in 1967 and 1994 in New York (USA) and 1973 in South Dakota (USA). The greatest number of DP epizootics reported since 1967 appear to have involved flocks of non-migratory rather than migratory waterfowl; therefore, in our opinion it remains unknown if DP is enzootic in either non-migratory or migratory waterfowl.     

Phylogeographic structure,demographic history and morph composition in a colour polymorphic lizard

In polymorphic species, population divergence in morph composition and frequency has the potential to promote speciation. We assessed the relationship between geographic variation in male throat colour polymorphism and phylogeographic structure in the tawny dragon lizard, Ctenophorus decresii. We identified four genetically distinct lineages, corresponding to two polymorphic lineages in the Northern Flinders Ranges and Southern Flinders Ranges/Olary Ranges regions respectively, and a monomorphic lineage in the Mt Lofty Ranges/Kangaroo Island region. The degree of divergence between these three lineages was consistent with isolation to multiple refugia during Pleistocene glacial cycles, whereas a fourth, deeply divergent (at the interspecific level) and monomorphic lineage was restricted to western New South Wales. The same four morphs occurred in both polymorphic lineages, although populations exhibited considerable variation in the frequency of morphs. By contrast, male throat coloration in the monomorphic lineages differed from each other and from the polymorphic lineages. Our results suggest that colour polymorphism has evolved once in the C. decresii species complex, with subsequent loss of polymorphism in the Mt Lofty Ranges/Kangaroo Island lineage. However, an equally parsimonious scenario, that polymorphism arose independently twice within C. decresii, could not be ruled out. We also detected evidence of a narrow contact zone with limited genotypic admixture between the polymorphic Olary Ranges and monomorphic Mt Lofty Ranges regions, yet no individuals of intermediate colour phenotype. Such genetic divergence and evidence for barriers to gene flow between lineages suggest incipient speciation between populations that differ in morph composition.     

Sea-level changes, river capture and the evolution of populations of the Eastern Cape and fiery redfins (Pseudobarbus afer and Pseudobarbus phlegethon, Cyprinidae) across multiple river systems in South Africa

Aim The phylogeography of the two closely related species Pseudobarbus afer and Pseudobarbus phlegethon was investigated to assess the association of evolutionary processes, inferred from mitochondrial DNA (mtDNA) sequence variation, with hypothetical palaeoriver systems and other climatic and landscape changes. Location One western and several southern river systems in South Africa. Methods We sampled known populations and confirmed known distribution gaps. This was followed by an assessment of mtDNA control region sequence variation for 31 localities across 17 river systems across the range of the species complex. A map of possible offshore drainage patterns during the last major regression event was constructed based on bathymetry and geological studies. Results The genetic distinction of four major lineages of P. afer strongly correspond with proposed palaeoriver systems. However, a western ‘Forest’ lineage, is widespread across two such proposed systems and is closely related to P. phlegethon on the west coast of South Africa. Both the ‘Krom’ and ‘St Francis’ lineages were identified in the single palaeoriver system proposed for St Francis Bay. A fourth ‘Mandela’ lineage is restricted to the one or two palaeoriver systems proposed for Nelson Mandela Bay. Four minor lineages were identified within the Forest lineage and two within the Mandela lineage. Main conclusions The close relationship between P. phlegethon and the Forest lineage of P. afer can only be explained by a series of river captures. We suggest the Gourits River system as a historical link that could account for this relationship. On the south coast, lower sea levels than at present allowed confluence between currently isolated river systems, offering opportunities for dispersal among these populations. At present, isolation between different river systems rather than dispersal appears to have a dominant influence on mtDNA diversity.     

Mitochondrial cytochrome b sequence variations and population structure of Siberian chipmunk (Tamias sibiricus) in Northeastern Asia and population substructure in South Korea

Twenty-five chipmunk species occur in the world, of which only the Siberian chipmunk, Tamias sibiricus, inhabits Asia. To investigate mitochondrial cytochrome b sequence variations and population structure of the Siberian chipmunk in northeastern Asia, we examined mitochondrial cytochrome b sequences (1140 bp) from 3 countries. Analyses of 41 individuals from South Korea and 33 individuals from Russia and northeast China resulted in 37 haplotypes and 27 haplotypes, respectively. There were no shared haplotypes between South Korea and Russia--northeast China. Phylogenetic trees and network analysis showed 2 major maternal lineages for haplotypes, referred to as the S and R lineages. Haplotype grouping in each cluster was nearly coincident with its geographic affinity. In particular, 3 distinct groups were found that mostly clustered in the northern, central and southern parts of South Korea. Nucleotide diversity of the S lineage was twice that of lineage R. The divergence between S and R lineages was estimated to be 2.98-0.98 Myr. During the ice age, there may have been at least 2 refuges in South Korea and Russia--northeast China. The sequence variation between the S and R lineages was 11.3% (K2P), which is indicative of specific recognition in rodents. These results suggest that T. sibiricus from South Korea could be considered a separate species. However, additional information, such as details of distribution, nuclear genes data or morphology, is required to strengthen this hypothesis.     

Global spread of wheat curl mite by its most polyphagous and pestiferous lineages

The wheat curl mite (WCM), Aceria tosichella, is an important pest of wheat and other cereal crops that transmits wheat streak mosaic virus and several other plant viruses. Wheat curl mite has long been considered a single polyphagous species, but recent studies in Poland revealed a complex of genetically distinct lineages with divergent host‐acceptance traits, ranging from highly polyphagous to host‐specific. This diversity of WCM genotypes and host‐acceptance phenotypes in Europe, the presumed native range of WCM, raises questions about the lineage identities of invasive WCM populations on other continents and their relationships to European lineages. The goals of this study were to examine the global presence of WCM and determine the relatedness of lineages established in different continents, on the basis of phylogenetic analyses of mitochondrial and nuclear DNA sequence data. Host‐range bioassays of a highly polyphagous WCM lineage were performed to supplement existing data on this lineage's ability to colonise graminaceous and non‐graminaceous hosts. Invasive WCM populations in North and South America and Australia assorted with the only three known polyphagous and pestiferous WCM lineages (‘MT‐1’, ‘MT‐7’ and ‘MT‐8’) from a total of eight currently described lineages. These results show that the most polyphagous lineages were more successful colonisers and reflect a need for extensive surveys for WCM on both crops and wild grass species in invaded continents. The most invasive lineage (‘MT‐1’) was shown to successfully colonise all 10 plant species tested in three families and has spread to North and South America and Australia from its presumed origins in Eurasia.     

Phylogeographical patterns shed light on evolutionary process in South America

The South American continent is composed of several biogeographical regions harbouring the highest biodiversity on the globe, encompassing five of the world's biodiversity ‘hot spots’. Nonetheless, the patterns and processes responsible for shaping its astonishing species diversity are largely unknown. Here, we present a review of current South American phylogeographical knowledge based on published articles on this topic. An appraisal of the literature reveals emerging phylogeographical patterns in the biota of South America. The striking phylogeographical divergence observed among organism lineages in South American studies is suggestive of high levels of undocumented species diversity. The interplay between Pleistocene climatic oscillations and Pliocene/Miocene orogenic events has contributed to shaping the current diversity and distribution of modern lineages in both the tropical and temperate regions of South America. Although older divergence times were observed for a range of species, most herpetofauna underwent an intraspecific lineage split much earlier than other organisms. The geographical ranges of species associated with forest habitats were reduced mainly during glacial cycles, whereas species associated with open vegetation domains have shown variable responses to climatic oscillations. The results suggest a highly complex mosaic of phylogeographical patterns in South America. We suggest future research directions to promote a better understanding of the origin and maintenance of the South American biota.     

Genetic differentiation of the gobies Gymnogobius castaneus and G. taranetzi in the region surrounding the sea of Japan as inferred from a mitochondrial gene genealogy

The phylogenetic relationships between gobies of the genus Gymnogobius were analyzed using mitochondrial cytochrome b gene sequences, focusing on the species currently classified as G. taranetzi and G. castaneus that occur in Japan, South Korea, and Russia. Gobies of the two species collected at 12 localities in Japan, South Korea, and Russia formed a monophyletic clade (called the "castaneus species complex" here) with G. breunigii as the sister clade. Within the species complex, six lineages were recognized: (L1) G. castaneus from the Akigawa River, Tokyo, Japan; (L2) G. castaneus from Yuza, Yamagata, Japan; (L3) G. taranetzi from Russia and South Korea; (L4) G. castaneus from the Tonegawa River, Chiba, Japan; (L5a) G. taranetzi from Shimane, Japan; and (L5b) G. castaneus + G. taranetzi from the Japan Sea coast of northern Japan. The two local lineages of G. castaneus (L1 and L2) are highly divergent from the others. The Japanese populations of G. taranetzi have diverged from the continental G. taranetzi populations, while one mitochondrial lineage (L5b) is shared with G. castaneus of northeast Japan. Therefore, the current species G. taranetzi and G. castaneus as defined morphologically are polyphyletic, necessitating a taxonomic revision. The genetic differentiation of isolated local lineages and the evolution of taranetzi-and castaneus-type gobies have likely occurred repeatedly in brackish/freshwater habitats around the Sea of Japan. We discussed the time of divergence for these gobies based on a tree with the molecular clock assumption.     

Phylogeny of the Southeast Asian freshwater fish genus Pangio (Cypriniformes; Cobitidae)

The genus Pangio is one of the most species-rich of the loach family Cobitidae and widespread across South and Southeast Asia. Its species diversity has never been studied under a clear phylogenetic approach, but four 'species-groups' were proposed according to the most obvious morphological characters. We present here phylogenetic analyses of the genus Pangio based on sequence data of the mitochondrial cytochrome b gene, the nuclear recombination-activating gene 1 (RAG 1) and a combined dataset of 109 specimens from 18 morphologically identified species across the whole distribution area of the genus. Our data reveal the existence of three major lineages within Pangio. Two of our major lineages were congruent with formerly proposed species-groups, the remaining two species-groups together formed the third major lineage; herein we refer to the lineages as to anguillaris-group, kuhlii-oblonga group and shelfordii-group. The application of a molecular clock dated the age of the three lineages to 33-29 million years. At the species level, our data suggest about 30 distinct lineages, indicating that there is a high number of undescribed species within Pangio. The use of Pangio to address biogeographic questions is demonstrated with the example of the shelfordii-group, which is distributed across Sundaland.     

The genetic legacy of polyploid Bolivian Daphnia: the tropical Andes as a source for the North and South American D. pulicaria complex

We investigated genetic variation in asexual polyploid members of the water flea Daphnia pulex complex from a set of 12 Bolivian high-altitude lakes. We used nuclear microsatellite markers to study genetic relationships among all encountered multilocus genotypes, and combined this with a phylogenetic approach using DNA sequence data of three mitochondrial genes. Analyses of mitochondrial gene sequence divergence showed the presence of three very distinct clades that likely represent cryptic undescribed species. Our phylogenetic results suggest that the Daphnia pulicaria group, a complex of predominantly North American species that has diversified rapidly since the Pleistocene, has its origin in South America, as specific tests of topology indicated that all three South American lineages are ancestral to the North American members of this species group. A comparison between variation of nuclear and mitochondrial markers revealed that closely related polyploid nuclear genotypes sometimes belonged to very divergent mitochondrial lineages, while distantly related nuclear genotypes often belonged to the same mitochondrial lineage. This discrepancy suggests that these South American water fleas originated through reciprocal hybridization between different endemic, sexually reproducing parental lineages. It is also likely that polyploidy of the investigated lineages resulted from this hybridization. Nevertheless, no putative diploid parental lineages were found in the studied region.