Directional dispersal between mid-ocean ridges: deep-ocean circulation and gene flow in Ridgeia piscesae

This study examined relationships between bathymetrically induced deep-ocean currents and the dispersal of the hydrothermal vent tubeworm Ridgeia piscesae along the northeast Pacific ridge system. A robust diagnostic model of deep-ocean circulation in this region predicted strong southeasterly currents following contours of the Blanco Transform Fault, a 450-km lateral offset that separates the Gorda and Juan de Fuca ridge systems. Such currents should facilitate the southward dispersal of R. piscesae larvae. Immigration rates for populations north and south of the Blanco Transform Fault were estimated from molecular population genetic data. Mitochondrial DNA evidence revealed population subdivision across the Blanco Transform Fault, and a strong directional bias in gene flow that was consistent with predictions of the circulation model. The distribution of mitochondrial diversity between the northern and southern populations of R. piscesae suggests that the Gorda Ridge tubeworms have maintained larger effective population sizes than the northern populations, a pattern that also exists in co-occurring limpets. Together, these data suggest that the northern vent fields may experience a higher frequency of habitat turnover and consequently more rapid losses of genetic diversity.     

Development and cross‐amplification of nine polymorphic microsatellite markers in the deep‐sea hydrothermal vent polychaete Branchipolynoe seepensis

The hydrothermal vent polychaete Branchipolynoe seepensis lives commensally inside the mantel cavity of the bivalves Bathymodiolus azoricus and Bathymodiolus puteoserpentis that form dense mussel beds around hydrothermal vents on the Mid‐Atlantic Ridge. In order to study its dispersal capabilities and the way individuals develop and reproduce, nine microsatellite polymorphic markers were developed. Polymorphism was tested from three well‐separated populations ranging from 14°N to 35°N along the ridge and showed significant levels of genetic differentiation. Cross‐amplification tests in other polynoid species revealed that most loci could also be useful to study closely related species from both Atlantic and Pacific sites.     

Genetic diversity and connectivity of deep‐sea hydrothermal vent metapopulations

Deep‐sea hydrothermal vents provide ephemeral habitats for animal communities that depend on chemosynthetic primary production. Sporadic volcanic and tectonic events destroy local vent fields and create new ones. Ongoing dispersal and cycles of extirpation and colonization affect the levels and distribution of genetic diversity in vent metapopulations. Several species exhibit evidence for stepping‐stone dispersal along relatively linear, oceanic, ridge axes. Other species exhibit very high rates of gene flow, although natural barriers associated with variation in depth, deep‐ocean currents, and lateral offsets of ridge axes often subdivide populations. Various degrees of impedance to dispersal across such boundaries are products of species‐specific life histories and behaviours. Though unrelated to the size of a species range, levels of genetic diversity appear to correspond with the number of active vent localities that a species occupies within its range. Pioneer species that rapidly colonize nascent vents tend to be less subdivided and more diverse genetically than species that are slow to establish colonies at vents. Understanding the diversity and connectivity of vent metapopulations provides essential information for designing deep‐sea preserves in regions that are under consideration for submarine mining of precious metals.     

Dispersal at hydrothermal vents: a summary of recent progress

The discovery of hydrothermal vents along the Galapagos Rift in 1977 opened up one of the most dynamic and productive research themes in marine biology. In the intervening 25 years, hydrothermal vent faunas have been described from the eastern, northeastern and western Pacific, the mid-Atlantic Ridge and the Indian Ocean in the region of the Rodriguez Triple Junction. In addition, there is evidence of hydrothermal signals from the Gakkel Ridge in the Arctic, the central and southwest Indian Ridges and the Scotia Arc in Antarctica. Although often perceived as a continuous linear structure, there are many discontinuities that have given rise to separate biogeographic provinces. In addition, the intervening 25 years have seen a massive increase in our understanding of the biological processes at hydrothermal vents. However, how vents are maintained, and how new vents are colonised has been relatively poorly understood until recently. This review addresses the known larval development of vent-endemic invertebrates. The distribution of larvae in relation to the hydrothermal plume, and the ocean ridge in general, are discussed and the experimental evidence of larval longevity and transport are discussed using such variables as gene flow and larval development rates. The concept of larval dispersal along the mid-ocean ridge is discussed in relation to dispersal barriers and relates the known biogeography of hydrothermal vent systems to both local and evolutionary processes.     

Migration, isolation, and speciation of hydrothermal vent limpets (Gastropoda; Lepetodrilidae) across the Blanco Transform Fault

The Sovanco Fracture Zone and Blanco Transform Fault separate the Explorer, Juan de Fuca, and Gorda ridge systems of the northeastern Pacific Ocean. To test whether such offsets in the ridge axis create barriers to along-axis dispersal of the endemic hydrothermal vent animals, we examined the genetic structure of limpet populations previously identified as Lepetodrilus fucensis McLean, 1988 (Gastropoda, Lepetodrilidae). Mitochondrial DNA sequences and patterns of allozyme variation revealed no evidence that the 150-km-long Sovanco Fracture Zone impeded gene flow between the Explorer and Juan de Fuca populations. In contrast, the 450-km-long Blanco Transform Fault separates the limpets into highly divergent northern and southern lineages that we recognize as distinct species. We describe southern populations from the Gorda Ridge (Seacliff) and Escanaba Trough as Lepetodrilus gordensis new species and refer northern populations from the Explorer and Juan de Fuca ridge systems to L. fucensis sensu stricto. The species are similar morphologically, but L. gordensis lacks a sensory neck papilla and has a more tightly coiled teleconch. To assess the degree of isolation between these closely related species, we used the Isolation with Migration method to estimate the time of population splitting, effective sizes of the ancestral and derived populations, and rates of migration across the Blanco Transform Fault.     

Oceanic dispersal in a sedentary reef shark (Triaenodon obesus): genetic evidence for extensive connectivity without a pelagic larval stage

Aim Most reef fishes are site‐attached, but can maintain a broad distribution through their highly dispersive larval stage. The whitetip reef shark (Triaenodon obesus) is site‐attached, yet maintains the largest Indo‐Pacific distribution of any reef shark while lacking the larval stage of bony (teleost) fishes. Here we use mitochondrial DNA (mtDNA) sequence data to evaluate the enigma of the sedentary reef shark that maintains a distribution across two‐thirds of the planet. Location Tropical Pacific and Indian Oceans. Methods We analysed 1025 base pairs of the mtDNA control region in 310 individuals from 25 locations across the Indian and Pacific Oceans. Phylogeographic and population genetic analyses were used to reveal the dispersal and recent evolutionary history of the species. Results We resolved 15 mtDNA control region haplotypes, but two comprised 87% of the specimens and were detected at nearly every location. Similar to other sharks, genetic diversity was low (h = 0.550 ± 0.0254 and π = 0.00213 ± 0.00131). Spatial analyses of genetic variation demonstrated strong isolation across the Indo‐Pacific Barrier and between western and central Pacific locations. Pairwise Φ_ST comparisons indicated high connectivity among archipelagos of the central Pacific but isolation across short distances of contiguous habitat (Great Barrier Reef) and intermittent habitat (Hawaiian Archipelago). In the eastern Pacific only a single haplotype (the most common one in the central Pacific) was observed, indicating recent dispersal (or colonization) across the East Pacific Barrier. Main conclusions The shallow haplotype network indicates recent expansion of modern populations within the last half million years from a common ancestor. Based on the distribution of mtDNA diversity, this began with an Indo‐West Pacific centre of origin, with subsequent dispersal to the Central Pacific and East Pacific. Genetic differences between Indian and Pacific Ocean populations are consistent with Pleistocene closures of the Indo‐Pacific Barrier associated with glacial cycles. Pairwise population comparisons reveal weak but significant isolation by distance, and notably do not indicate the high coastal connectivity observed in other shark species. The finding of population structure among semi‐contiguous habitats, but population connectivity among archipelagos, may indicate a previously unsuspected oceanic dispersal behaviour in whitetip reef sharks.     

Distinct patterns of genetic differentiation among annelids of eastern Pacific hydrothermal vents

Population genetic and phylogenetic analyses of mitochondrial COI from five deep-sea hydrothermal vent annelids provided insights into their dispersal modes and barriers to gene flow. These polychaetes inhabit vent fields located along the East Pacific Rise (EPR) and Galapagos Rift (GAR), where hundreds to thousands of kilometers can separate island-like populations. Long-distance dispersal occurs via larval stages, but larval life histories differ among these taxa. Mitochondrial gene flow between populations of Riftia pachyptila, a siboglinid worm with neutrally buoyant lecithothrophic larvae, is diminished across the Easter Microplate region, which lies at the boundary of Indo-Pacific and Antarctic deep-sea provinces. Populations of the siboglinid Tevnia jerichonana are similarly subdivided. Oasisia alvinae is not found on the southern EPR, but northern EPR populations of this siboglinid are subdivided across the Rivera Fracture Zone. Mitochondrial gene flow of Alvinella pompejana, an alvinellid with large negatively buoyant lecithotrophic eggs and arrested embryonic development, is unimpeded across the Easter Microplate region. Gene flow in the polynoid Branchipolynoe symmytilida also is unimpeded across the Easter Microplate region. However, A. pompejana populations are subdivided across the equator, whereas B. symmitilida populations are subdivided between the EPR and GAR axes. The present findings are compared with similar evidence from codistributed species of annelids, molluscs and crustaceans to identify potential dispersal filters in these eastern Pacific ridge systems.     

Recent population expansion and connectivity in the hydrothermal shrimp Rimicaris exoculata along the Mid‐Atlantic Ridge

Aim Deep‐sea hydrothermal vents are unstable habitats that are both spatially and temporally fragmented. In vent species, a ‘short‐term insurance’ hypothesis would lead us to expect mostly self‐recruitment, limiting the loss of larvae in the deep ocean or water column and increasing genetic differentiation over the time elapsed since colonization. Alternatively, a ‘long‐term insurance’ hypothesis would support the prediction of selection for large‐scale dispersal, to ensure long‐term persistence in these ephemeral habitats. The main goal of this study was to infer the spatial and temporal distribution of genetic diversity of the shrimp Rimicaris exoculata, which forms high‐density local populations on hydrothermal vents along the Mid‐Atlantic ridge. Location Deep‐sea hydrothermal vents along the Mid‐Atlantic Ridge. Methods We used sequences of mitochondrial cytochrome c oxidase subunit I (COI, 710 bp) to assess the spatio‐temporal distribution of genetic diversity across five hydrothermal fields from 36° N to 4° S. Results In contrast to previous results from pioneer studies, very high haplotype diversity was observed in vents across the entire region (i.e. 0.69–0.82), indicating current large effective population size and low drift. The star‐like shape of the network of haplotypes, the lack of spatial genetic structure and the significance of tests reflecting demographic effects, together with the fitting of a population expansion model, all support a recent population expansion. Main conclusions Our results suggest a very recent common history of R. exoculata populations/demes along the Mid‐Atlantic Ridge, derived after a common bottleneck or founder event and followed by a concomitant demographic expansion. This study therefore suggests a large effective population size and/or high dispersal capacity, as well as a possible recent (re)colonization of Mid‐Atlantic hydrothermal vents by R. exoculata.     

Population differentiation in the open sea: insights from the pelagic copepod Pleuromamma xiphias

Although a number of recent studies of marine holoplankton have reported significant genetic structure among populations, little is currently known about the biological and oceanographic processes that influence population connectivity in oceanic plankton. In order to examine how depth preferences influence dispersal in oceanic plankton, I characterized the genetic structure of a copepod with diel vertical migration (DVM) (Pleuromamma xiphias), throughout its global distribution, and compared these results to those expected given the interaction of this species' habitat depth with ocean circulation and bathymetry. Mitochondrial COI sequences from 651 individuals from 28 sites in the Indian, Pacific, and Atlantic Oceans revealed highly significant genetic differentiation both within and among ocean basins. Limited dispersal among distinct pelagic provinces seems to have played a major role in population differentiation in this species, with strong genetic breaks observed across known oceanographic fronts or current systems in all three ocean basins. The Indo-West Pacific (IWP) holds a highly distinct genetic population of this species that was sampled in both the western Pacific and eastern Indian Oceans. This suggests that the IWP does not act as a strong barrier to gene flow between basins, as expected, despite the relatively shallow water depth (<200 m) and vertically extensive (>400 m) diel migration of this species. A pattern of isolation by distance was observed in the Indian Ocean with genetic differentiation among samples down to spatial scales of ～800 km, indicating that realized dispersal in P. xiphias occurs over much smaller spatial scales than in previously reported oceanic holoplankton. Given its highly regionalized population genetic structure, P. xiphias may have some capacity to adapt to local oceanographic conditions, and it should not be assumed that populations of this species in distinct pelagic biomes will respond in the same way to shared physical or climatic forcing.     

Comparative Population Structure of Two Deep-Sea Hydrothermal-Vent-Associated Decapods (Chorocaris sp. 2 and Munidopsis lauensis) from Southwestern Pacific Back-Arc Basins

Studies of genetic connectivity and population structure in deep-sea chemosynthetic ecosystems often focus on endosymbiont-hosting species that are directly dependent on chemical energy extracted from vent effluent for survival. Relatively little attention has been paid to vent-associated species that are not exclusively dependent on chemosynthetic ecosystems. Here we assess connectivity and population structure of two vent-associated invertebrates—the shrimp Chorocaris sp. 2 and the squat lobster Munidopsis lauensis—that are common at deep-sea hydrothermal vents in the western Pacific. While Chorocaris sp. 2 has only been observed at hydrothermal vent sites, M. lauensis can be found throughout the deep sea but occurs in higher abundance around the periphery of active vents We sequenced mitochondrial COI genes and deployed nuclear microsatellite markers for both species at three sites in Manus Basin and either North Fiji Basin (Chorocaris sp. 2) or Lau Basin (Munidopsis lauensis). We assessed genetic differentiation across a range of spatial scales, from approximately 2.5 km to more than 3000 km. Population structure for Chorocaris sp. 2 was comparable to that of the vent-associated snail Ifremeria nautilei, with a single seemingly well-mixed population within Manus Basin that is genetically differentiated from conspecifics in North Fiji Basin. Population structure for Munidopsis lauensis was more complex, with two genetically differentiated populations in Manus Basin and a third well-differentiated population in Lau Basin. The unexpectedly high level of genetic differentiation between M. lauensis populations in Manus Basin deserves further study since it has implications for conservation and management of diversity in deep-sea hydrothermal vent ecosystems.     

Contrasting Genetic Structure among Populations of Two Amphidromous Fish Species (Sicydiinae) in the Central West Pacific

Both present-day and past processes can shape connectivity of populations. Pleistocene vicariant events and dispersal have shaped the present distribution and connectivity patterns of aquatic species in the Indo-Pacific region. In particular, the processes that have shaped distribution of amphidromous goby species still remain unknown. Previous studies show that phylogeographic breaks are observed between populations in the Indian and Pacific Oceans where the shallow Sunda shelf constituted a geographical barrier to dispersal, or that the large spans of open ocean that isolate the Hawaiian or Polynesian Islands are also barriers for amphidromous species even though they have great dispersal capacity. Here we assess past and present genetic structure of populations of two amphidromous fish (gobies of the Sicydiinae) that are widely distributed in the Central West Pacific and which have similar pelagic larval durations. We analysed sections of mitochondrial COI, Cytb and nuclear Rhodospine genes in individuals sampled from different locations across their entire known range. Similar to other Sicydiinae fish, intraspecific mtDNA genetic diversity was high for all species (haplotype diversity between 0.9–0.96). Spatial analyses of genetic variation in Sicyopus zosterophorum demonstrated strong isolation across the Torres Strait, which was a geologically intermittent land barrier linking Australia to Papua New Guinea. There was a clear genetic break between the northwestern and the southwestern clusters in Si. zosterophorum (φ_ST = 0.67502 for COI) and coalescent analyses revealed that the two populations split at 306 Kyr BP (95% HPD 79–625 Kyr BP), which is consistent with a Pleistocene separation caused by the Torres Strait barrier. However, this geographical barrier did not seem to affect Sm. fehlmanni. Historical and demographic hypotheses are raised to explain the different patterns of population structure and distribution between these species. Strategies aiming to conserve amphidromous fish should consider the presence of cryptic evolutionary lineages to prevent stock depletion.     

Phylogeography of the crown-of-thorns starfish: genetic structure within the Pacific species

Previous studies of the population genetic structure of the corallivorous crown-of-thorns starfish (COTS) Acanthaster planci in the Pacific Ocean showed high levels of gene flow that were assumed to reflect a high dispersal potential. However, the phylogeographic analyses of the Pacific crown-of-thorns starfish species of this study, using the highly variable mitochondrial control region and the most complete geographic coverage to date, contradict this view. Results show high levels of overall genetic structure (Φ_ST = 0.198), suggesting a complex history of range restrictions and expansions, a pattern that we hypothesize results from changes in topography and oceanography associated with sea-level changes. However, results also show signatures of ongoing gene flow between populations isolated in the past and high levels of genetic connectivity even among distant populations. Combined, these results indicate that while there are significant limits to genetic exchange among populations among Pacific Ocean populations of the crown-of-thorns starfish, the high larval dispersal potential of this species is often achieved as well.     

Amplicon sequencing of 42 nuclear loci supports directional gene flow between South Pacific populations of a hydrothermal vent limpet

In the past few decades, population genetics and phylogeographic studies have improved our knowledge of connectivity and population demography in marine environments. Studies of deep‐sea hydrothermal vent populations have identified barriers to gene flow, hybrid zones, and demographic events, such as historical population expansions and contractions. These deep‐sea studies, however, used few loci, which limit the amount of information they provided for coalescent analysis and thus our ability to confidently test complex population dynamics scenarios. In this study, we investigated population structure, demographic history, and gene flow directionality among four Western Pacific hydrothermal vent populations of the vent limpet Lepetodrilus aff. schrolli. These vent sites are located in the Manus and Lau back‐arc basins, currently of great interest for deep‐sea mineral extraction. A total of 42 loci were sequenced from each individual using high‐throughput amplicon sequencing. Amplicon sequences were analyzed using both genetic variant clustering methods and evolutionary coalescent approaches. Like most previously investigated vent species in the South Pacific, L. aff. schrolli showed no genetic structure within basins but significant differentiation between basins. We inferred significant directional gene flow from Manus Basin to Lau Basin, with low to no gene flow in the opposite direction. This study is one of the very few marine population studies using >10 loci for coalescent analysis and serves as a guide for future marine population studies.     

Characterization of Bacterial Communities in Deep-Sea Hydrothermal Vents from Three Oceanic Regions

Deep-sea hydrothermal vents are considered to be one of the most spectacular ecosystems on Earth. Microorganisms form the basis of the food chain in vents controlling the vent communities. However, the diversity of bacterial communities in deep-sea hydrothermal vents from different oceans remains largely unknown. In this study, the pyrosequencing of 16S rRNA gene was used to characterize the bacterial communities of the venting sulfide, seawater, and tubeworm trophosome from East Pacific Rise, South Atlantic Ridge, and Southwest Indian Ridge, respectively. A total of 23,767 operational taxonomic units (OTUs) were assigned into 42 different phyla. Although Proteobacteria, Actinobacteria, and Bacteroidetes were the predominant phyla in all vents, differences of bacterial diversity were observed among different vents from three oceanic regions. The sulfides of East Pacific Rise possessed the most diverse bacterial communities. The bacterial diversities of venting seawater were much lower than those of vent sulfides. The symbiotic bacteria of tubeworm Ridgeia piscesae were included in the bacterial community of vent sulfides, suggesting their significant ecological functions as the primary producers in the deep-sea hydrothermal vent ecosystems. Therefore, our study presented a comprehensive view of bacterial communities in deep-sea hydrothermal vents from different oceans.     

Discovery of new hydrothermal activity and chemosynthetic fauna on the Central Indian Ridge at 18°-20° S

Indian Ocean hydrothermal vents are believed to represent a novel biogeographic province, and are host to many novel genera and families of animals, potentially indigenous to Indian Ocean hydrothermal systems. In particular, since its discovery in 2001, much attention has been paid to a so-called 'scaly-foot' gastropod because of its unique iron-sulfide-coated dermal sclerites and the chemosynthetic symbioses in its various tissues. Despite increasing interest in the faunal assemblages at Indian Ocean hydrothermal vents, only two hydrothermal vent fields have been investigated in the Indian Ocean. Here we report two newly discovered hydrothermal vent fields, the Dodo and Solitaire fields, which are located in the Central Indian Ridge (CIR) segments 16 and 15, respectively. Chemosynthetic faunal communities at the Dodo field are emaciated in size and composition. In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa. Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field. The newly discovered 'scaly-foot' gastropod has similar morphological and anatomical features to the previously reported type that inhabits the Kairei field, and both types of 'scaly-foot' gastropods genetically belong to the same species according to analyses of their COI gene and nuclear SSU rRNA gene sequences. However, the new morphotype completely lacks an iron-sulfide coating on the sclerites, which had been believed to be a novel feature restricted to 'scaly-foot' gastropods. Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean.     

The discovery of new deep-sea hydrothermal vent communities in the southern ocean and implications for biogeography

Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than previously recognised.     

Dispersal barriers and isolation among deep-sea mussel populations (Mytilidae: Bathymodiolus) from eastern Pacific hydrothermal vents

Deep-sea hydrothermal vent species are widely dispersed among habitat islands found along the global mid-ocean ridge system. We examine factors that affect population structure, gene flow and isolation in vent-endemic mussels of the genus Bathymodiolus from the eastern Pacific Ocean. Mussels were sampled from localities including the Galapagos Rift (GAR, 0 degrees 48' N; 86 degrees 10' W) and the East Pacific Rise (EPR, 13 degrees N to 32 degrees S latitude) across a maximum distance of 4900 km. The sampled range crossed a series of topographical features that interrupt linear aspects of the ridge system, and it encompassed regions of strong cross-axis currents that could impede along-axis dispersal of mussel larvae. Examinations of mitochondrial DNA sequences and allozyme variation revealed significant barriers to gene flow along the ridge axis. All populations from the GAR and EPR from 13 degrees N to 11 degrees S were homogeneous genetically and appeared to experience unimpeded high levels of interpopulational gene flow. In contrast, mussels from north and south of the Easter Microplate were highly divergent (4.4%), possibly comprising sister-species that diverged after formation of the microplate approximately 4.5 Ma. Strong cross-axis currents associated with inflated bathymetry of the microplate region may reinforce isolation across this region.     

Genetic patterns and conservation of the Scarlet Macaw (<Emphasis Type="Italic">Ara macao</Emphasis>) in Costa Rica

Once widely distributed throughout the lowland forests of Costa Rica, scarlet macaws (Ara macao) have been reduced to two major, geographically separated, populations along the Pacific slope. Past demographic declines raise conservation concerns regarding the detrimental effects of population fragmentation. This investigation aimed to evaluate the current status of scarlet macaws along the Pacific slope by examining levels of genetic variation and patterns of genetic structure within and among remnant populations. Statistical analyses using multilocus genotypes revealed strong differentiation between Central and South Pacific populations, suggesting local geographic barriers have historically restricted gene flow between these localities. High genetic diversity suggests neither population suffers from genetic erosion, likely resulting from relatively large population sizes and high dispersal capacity and longevity. However, evidence of disequilibrium within the Central Pacific population infers anthropogenic threats have disrupted natural population dynamics. These results advocate on focusing available resources on habitat restoration and nest protection, as a means to assist in reestablishing demographic stability and maintain the genetic health of wild scarlet macaws in Costa Rica.     

Comparison of a New Thiomicrospira Strain from the Mid-Atlantic Ridge with Known Hydrothermal Vent Isolates

A new autotrophic Thiomicrospira strain, MA-3, was isolated from the surface of a polymetal sulfide deposit collected at a Mid-Atlantic Ridge hydrothermal vent site. The DNA homology among three vent isolates, Thiomicrospira crunogena, Thiomicrospira sp. strain L-12, and Thiomicrospira sp. strain MA-3, was 99.3% or higher, grouping them as the same species, T. crunogena (type strain, ATCC 35932). The fact that T. crunogena and Thiomicrospira sp. strain L-12 were isolated from Pacific vent sites demonstrates a cosmopolitan distribution of this species.