High Connectivity in Rastrelliger kanagurta: Influence of Historical Signatures and Migratory Behaviour Inferred from mtDNA Cytochrome b

Phylogeographic patterns and population structure of the pelagic Indian mackerel, Rastrelliger kanagurta were examined in 23 populations collected from the Indonesian-Malaysian Archipelago (IMA) and the West Indian Ocean (WIO). Despite the vast expanse of the IMA and neighbouring seas, no evidence for geographical structure was evident. An indication that R. kanagurta populations across this region are essentially panmictic. This study also revealed that historical isolation was insufficient for R. kanagurta to attain migration drift equilibrium. Two distinct subpopulations were detected between the WIO and the IMA (and adjacent populations); interpopulation genetic variation was high. A plausible explanation for the genetic differentiation observed between the IMA and WIO regions suggest historical isolation as a result of fluctuations in sea levels during the late Pleistocene. This occurrence resulted in the evolution of a phylogeographic break for this species to the north of the Andaman Sea.     

Comparative phylogeography of the western Indian Ocean reef fauna

Assessing patterns of connectivity at the community and population levels is relevant to marine resource management and conservation. The present study reviews this issue with a focus on the western Indian Ocean (WIO) biogeographic province. This part of the Indian Ocean holds more species than expected from current models of global reef fish species richness. In this study, checklists of reef fish species were examined to determine levels of endemism in each of 10 biogeographic provinces of the Indian Ocean. Results showed that the number of endemic species was higher in the WIO than in any other region of the Indian Ocean. Endemic species from the WIO on the average had a larger body size than elsewhere in the tropical Indian Ocean. This suggests an effect of peripheral speciation, as previously documented in the Hawaiian reef fish fauna, relative to other sites in the tropical western Pacific. To explore evolutionary dynamics of species across biogeographic provinces and infer mechanisms of speciation, we present and compare the results of phylogeographic surveys based on compilations of published and unpublished mitochondrial DNA sequences for 19 Indo-Pacific reef-associated fishes (rainbow grouper Cephalopholis argus, scrawled butterflyfish Chaetodon meyeri, bluespot mullet Crenimugil sp. A, humbug damselfish Dascyllus abudafur/Dascyllus aruanus, areolate grouper Epinephelus areolatus, blacktip grouper Epinephelus fasciatus, honeycomb grouper Epinephelus merra, bluespotted cornetfish Fistularia commersonii, cleaner wrasse Labroides sp. 1, longface emperor Lethrinus sp. A, bluestripe snapper Lutjanus kasmira, unicornfishes Naso brevirosris, Naso unicornis and Naso vlamingii, blue-spotted maskray Neotrygon kuhlii, largescale mullet Planiliza macrolepis, common parrotfish Scarus psicattus, crescent grunter Terapon jarbua, whitetip reef shark Triaenodon obesus) and three coastal Indo-West Pacific invertebrates (blue seastar Linckia laevigata, spiny lobster Panulirus homarus, small giant clam Tridacna maxima). Heterogeneous and often unbalanced sampling design, paucity of data in a number of cases, and among-species discrepancy in phylogeographic structure precluded any generalization regarding phylogeographic patterns. Nevertheless, the WIO might have been a source of haplotypes in some cases and it also harboured an endemic clade in at least one case. The present survey also highlighted likely cryptic species. This may eventually affect the accuracy of the current checklists of species, which form the basis of some of the recent advances in Indo-West Pacific marine ecology and biogeography.     

Phylogeography of the Crown-of-Thorns Starfish in the Indian Ocean

Background

Understanding the limits and population dynamics of closely related sibling species in the marine realm is particularly relevant in organisms that require management. The crown-of-thorns starfish Acanthaster planci, recently shown to be a species complex of at least four closely related species, is a coral predator infamous for its outbreaks that have devastated reefs throughout much of its Indo-Pacific distribution.

Methodology/Principal Findings

In this first Indian Ocean-wide genetic study of a marine organism we investigated the genetic structure and inferred the paleohistory of the two Indian Ocean sister-species of Acanthaster planci using mitochondrial DNA sequence analyses. We suggest that the first of two main diversification events led to the formation of a Southern and Northern Indian Ocean sister-species in the late Pliocene-early Pleistocene. The second led to the formation of two internal clades within each species around the onset of the last interglacial. The subsequent demographic history of the two lineages strongly differed, the Southern Indian Ocean sister-species showing a signature of recent population expansion and hardly any regional structure, whereas the Northern Indian Ocean sister-species apparently maintained a constant size with highly differentiated regional groupings that were asymmetrically connected by gene flow.

Conclusions/Significance

Past and present surface circulation patterns in conjunction with ocean primary productivity were identified as the processes most likely to have shaped the genetic structure between and within the two Indian Ocean lineages. This knowledge will help to understand the biological or ecological differences of the two sibling species and therefore aid in developing strategies to manage population outbreaks of this coral predator in the Indian Ocean.     

Population genetics of the brooding coral Seriatopora hystrix reveals patterns of strong genetic differentiation in the Western Indian Ocean

Coral reefs provide essential goods and services but are degrading at an alarming rate due to local and global anthropogenic stressors. The main limitation that prevents the implementation of adequate conservation measures is that connectivity and genetic structure of populations are poorly known. Here, the genetic diversity and connectivity of the brooding scleractinian coral Seriatopora hystrix were assessed at two scales by genotyping ten microsatellite markers for 356 individual colonies. S. hystrix showed high differentiation, both at large scale between the Red Sea and the Western Indian Ocean (WIO), and at smaller scale along the coast of East Africa. As such high levels of differentiation might indicate the presence of more than one species, a haploweb analysis was conducted with the nuclear marker ITS2, confirming that the Red Sea populations are genetically distinct from the WIO ones. Based on microsatellite analyses three groups could be distinguished within the WIO: (1) northern Madagascar, (2) south-west Madagascar together with one site in northern Mozambique (Nacala) and (3) all other sites in northern Mozambique, Tanzania and Kenya. These patterns of restricted connectivity could be explained by the short pelagic larval duration of S. hystrix, and/or by oceanographic factors, such as eddies in the Mozambique Channel (causing larval retention in northern Madagascar but facilitating dispersal from northern Mozambique towards south-west Madagascar). This study provides an additional line of evidence supporting the conservation priority status of the Northern Mozambique Channel and should inform coral reef management decisions in the region.Subject terms: Haplotypes, Structural variation, Conservation biology, Population dynamics, Biogeography     

Uvigerina proboscidea abundances and paleoceanography of the northern Indian Ocean DSDP Site 214 during the Late Neogene

This study attempts to understand the significance of Uvigerina proboscidea in paleoceanographic reconstructions at the northern (tropical) Indian Ocean DSDP Site 214 from the Late Miocene through the Pleistocene. In this interval at this site, U. proboscidea is the most abundant species of the benthic assemblage and shows abrupt frequency changes (about 1–74%). Based on relative percentages of U. proboscidea calibrated with oxygen and carbon isotope record and the sediment accumulation rates, the modern distribution of the species in the Indian Ocean, and other evidence, the peaks of abundance of U. proboscidea are inferred to represent times of high-surface productivity. This productivity is related to intensified trade winds during strong southwest (SW) Indian monsoons, causing widespread upwelling along equatorial divergence in the Indian Ocean. The sudden increase of U. proboscidea abundance at approximately 8.5–7.5 Ma reflects significant upwelling at the equatorial divergence. This event corresponds to the permanent build-up of West Antarctic ice sheets, and a major increase in SW Indian monsoons related upwelling in the northwestern Indian Ocean. The Chron-6 carbon shift at approximately 6.2 Ma is marked by another peak of abundance, reflecting widespread ocean fertility. The highest abundances of U. proboscidea and highest sediment accumulation rates occur between 5.8 and 5.1 Ma, which coincides with the greatest development of Antarctic ice sheets and strong southwest monsoons. The higher percentages at 3.2–3.1 Ma, approximately 2.4 Ma, and 1.6 Ma all represent phases of high productivity at the equatorial divergence.     

Cultivation and utilisation of red seaweeds in the Western Indian Ocean (WIO) Region

Seaweed farming in the Western Indian Ocean (WIO) Region is carried out in a number of countries, most of them farming Eucheuma denticulatum, Kappaphycus alvarezii and Kappaphycus striatum. These species are farmed mostly in Tanzania with limited production in Madagascar, Mozambique and Kenya; current production (2012) stands at 15,966 t (dry weight) year^?1 of Eucheuma and Kappaphycus, valued at US$ 4.2 million with 95 % of this tonnage coming from Tanzania. Other countries in the region have limited or no seaweed production owing to problems of epiphytes, ice ice and markets. The problem of epiphytes coupled with ice ice that WIO countries are facing causes die-off of Kappaphycus which is the preferred species in foreign markets for its thicker gel, kappa carrageenan (vs. the weaker iota carrageenan from Eucheuma). New efforts are put to curb these problems including moving seaweed farms to deeper waters and cultivation trials of other carrageenophytes as well as agar-producing species, agarophytes. Research work has been initiated to evaluate Gracilaria and Hypnea farming and processing in Tanzania, the Republic of Mauritius and Mayotte. Gracilaria farming is at experimental stages as a biofilter of fishpond effluents and as potential species for the production of agar with growth rates of 1.5–1.9 % day^?1. Hypnea farming is only being initiated in Mauritius and Mayotte at present. Other innovations including value addition by making various seaweed products and encouraging the consumption of seaweed as food at least in Tanzania and Mauritius are increasing further the importance of the seaweed farming and processing industry in the WIO Region.     

The Diversity and Biogeography of Western Indian Ocean Reef-Building Corals

This study assesses the biogeographic classification of the Western Indian Ocean (WIO) on the basis of the species diversity and distribution of reef-building corals. Twenty one locations were sampled between 2002 and 2011. Presence/absence of scleractinian corals was noted on SCUBA, with the aid of underwater digital photographs and reference publications for species identification. Sampling effort varied from 7 to 37 samples per location, with 15 to 45 minutes per dive allocated to species observations, depending on the logistics on each trip. Species presence/absence was analyzed using the Bray-Curtis similarity coefficient, followed by cluster analysis and multi-dimensional scaling. Total (asymptotic) species number per location was estimated using the Michaelis-Menten equation. Three hundred and sixty nine coral species were named with stable identifications and used for analysis. At the location level, estimated maximum species richness ranged from 297 (Nacala, Mozambique) to 174 (Farquhar, Seychelles). Locations in the northern Mozambique Channel had the highest diversity and similarity, forming a core region defined by its unique oceanography of variable meso-scale eddies that confer high connectivity within this region. A distinction between mainland and island fauna was not found; instead, diversity decreased radially from the northern Mozambique Channel. The Chagos archipelago was closely related to the northern Mozambique Channel region, and analysis of hard coral data in the IUCN Red List found Chagos to be more closely related to the WIO than to the Maldives, India and Sri Lanka. Diversity patterns were consistent with primary oceanographic drivers in the WIO, reflecting inflow of the South Equatorial Current, maintenance of high diversity in the northern Mozambique Channel, and export from this central region to the north and south, and to the Seychelles and Mascarene islands.     

Associations between climate stress and coral reef diversity in the western Indian Ocean

Climatic–oceanographic stress and coral reef diversity were mapped in the western Indian Ocean (WIO) in order to determine if there were associations between high diversity coral reefs and regions with low‐to‐moderate climate stress. A multivariate stress model developed to estimate environmental exposure to stress, an empirical index of the coral community's susceptibility to stress, and field data on numbers of fish and corals taxa from 197 WIO sites were overlain to evaluate these associations. Exposure to stress was modeled from satellite data based on nine geophysical–biological oceanographic characteristics known to influence coral bleaching (i.e. temperature, light, and current variables). The environmental stress model and the coral community's susceptibility index were moderately correlated (r=?0.51) with southern and eastern parts of the WIO identified as areas with low environmental stress and coral communities with greater dominance of bleaching stress‐sensitive taxa. Numbers of coral and fish taxa were positive and moderately correlated (r=0.47) but high diversity regions for fish were in the north and west while diversity was highest for corals in central regions from Tanzania to northwestern Madagascar. Combining three and four of these variables into composite maps identified a region from southern Kenya to northern Mozambique across to northern–eastern Madagascar and the Mascarene Islands and the Mozambique–South Africa border as areas where low‐moderate environmental exposure overlaps with moderate‐high taxonomic diversity. In these areas management efforts aimed at maintaining high‐diversity and intact ecosystems are considered least likely to be undermined by climate disturbances in the near term. Reducing additional human disturbances, such as fishing and pollution, in these areas is expected to improve the chances for their persistence. These reefs are considered a high priority for increased local, national, and international management efforts aimed at establishing coral reef refugia for climate change impacts.     

Genetic structure and diversity of coffee (Coffea) across Africa and the Indian Ocean islands revealed using microsatellites

Background and Aims

The coffee genus (Coffea) comprises 124 species, and is indigenous to the Old World Tropics. Due to its immense economic importance, Coffea has been the focus of numerous genetic diversity studies, but despite this effort it remains insufficiently studied. In this study the genetic diversity and genetic structure of Coffea across Africa and the Indian Ocean islands is investigated.

Methods

Genetic data were produced using 13 polymorphic nuclear microsatellite markers (simple sequence repeats, SSRs), including seven expressed sequence tag-SSRs, and the data were analysed using model- and non-model-based methods. The study includes a total of 728 individuals from 60 species.

Key Results

Across Africa and the Indian Ocean islands Coffea comprises a closely related group of species with an overall pattern of genotypes running from west to east. Genetic structure was identified in accordance with pre-determined geographical regions and phylogenetic groups. There is a good relationship between morpho-taxonomic species delimitations and genetic units. Genetic diversity in African and Indian Ocean Coffea is high in terms of number of alleles detected, and Madagascar appears to represent a place of significant diversification in terms of allelic richness and species diversity.

Conclusions

Cross-species SSR transferability in African and Indian Ocean islands Coffea was very efficient. On the basis of the number of private alleles, diversification in East Africa and the Indian Ocean islands appears to be more recent than in West and West-Central Africa, although this general trend is complicated in Africa by the position of species belonging to lineages connecting the main geographical regions. The general pattern of phylogeography is not in agreement with an overall east to west (Mascarene, Madagascar, East Africa, West Africa) increase in genome size, the high proportion of shared alleles between the four regions or the high numbers of exclusive shared alleles between pairs or triplets of regions.     

Gephyrocapsa occurrence during the Middle Pleistocene transition in the Northern Pacific Ocean (Shatsky Rise)

The gephyrocapsids, main component of the Pleistocene calcareous nannofossil assemblages, are here discussed as biostratigraphical and paleoclimate tools. The occurrence of the genus Gephyrocapsa is quantitatively analysed in the core ODP 198-1209B, collected in the NW Pacific Ocean. The studied stratigraphic succession covers a time interval including the Middle Pleistocene Transition (MPT), a highly investigated period characterized by important global climate changes. During the Pleistocene, Gephyrocapsa is extremely abundant and provides several bioevents used in biostratigraphy. In addition to the known standard events, we observe the occurrence of particular Gephyrocapsa morphogroups and significant changes in the relative abundance of G. caribbeanica. In the Early-Middle Pleistocene we identify four intervals based on the Gephyrocapsa content. Moreover, during the MPT, the stratigraphic distribution of Gephyrocapsa underlines a dominance of both the small morphogroup and the medium-sized G. caribbeanica that could be dependent on their paleoecology. Small Gephyrocapsa and G. caribbeanica seem to be more competitive than other coccolithophores during the global oceanographic variations and the re-organisation of the glacial-interglacial periodicity during the MPT.     

Population genetic structure and connectivity of the seagrass Thalassia hemprichii in the Western Indian Ocean is influenced by predominant ocean currents

This study is the first large‐scale genetic population study of a widespread climax species of seagrass, Thalassia hemprichii, in the Western Indian Ocean (WIO). The aim was to understand genetic population structure and connectivity of T. hemprichii in relation to hydrodynamic features. We genotyped 205 individual seagrass shoots from 11 sites across the WIO, spanning over a distance of ~2,700 km, with twelve microsatellite markers. Seagrass shoots were sampled in Kenya, Tanzania (mainland and Zanzibar), Mozambique, and Madagascar: 4–26°S and 33–48°E. We assessed clonality and visualized genetic diversity and genetic population differentiation. We used Bayesian clustering approaches (TESS) to trace spatial ancestry of populations and used directional migration rates (DivMigrate) to identify sources of gene flow. We identified four genetically differentiated groups: (a) samples from the Zanzibar channel; (b) Mozambique; (c) Madagascar; and (d) the east coast of Zanzibar and Kenya. Significant pairwise population genetic differentiation was found among many sites. Isolation by distance was detected for the estimated magnitude of divergence (D_EST), but the three predominant ocean current systems (i.e., East African Coastal Current, North East Madagascar Current, and the South Equatorial Current) also determine genetic connectivity and genetic structure. Directional migration rates indicate that Madagascar acts as an important source population. Overall, clonality was moderate to high with large differences among sampling sites, indicating relatively low, but spatially variable sexual reproduction rates. The strongest genetic break was identified for three sites in the Zanzibar channel. Although isolation by distance is present, this study suggests that the three regionally predominant ocean current systems (i.e., East African Coastal Current, North East Madagascar Current, and the South Equatorial Current) rather than distance determine genetic connectivity and structure of T. hemprichii in the WIO. If the goal is to maintain genetic connectivity of T. hemprichii within the WIO, conservation planning and implementation of marine protection should be considered at the regional scale—across national borders.     

Radiolarian biogeography in surface sediments of the eastern Indian Ocean

We analyzed recurrent groups of Radiolaria in 74 core top samples from a transect through the eastern Indian Ocean in order to supplement our previous results from the western Indian Ocean (Johnson and Nigrini, 1980). We now identify six distinct recurrent groups and nine radiolarian assemblages in the combined data set of 120 samples; this extended sample coverage has led to several re-interpretations of the oceanographic significance of the radiolarian distribution patterns. Assemblage boundaries closely reflect the presence of major oceanographic fronts and surface currents including the South Equatorial Divergence, Subtropical Gyre, Subtropical Convergence, and Antarctic Convergence. At least four major aspects of the assemblages in the eastern transect are notably different from those in the western transect, leading to a marked east-west asymmetry in faunal distribution patterns across the Indian Ocean. The assemblage formerly associated with strong upwelling near the Arabian Peninsula is present throughout the Bay of Bengal as well, and is interpreted to reflect high salinity and low oxygen in the subsurface waters of the Indian Ocean north of the Equator. A new assemblage has been identified associated with the westward-flowing Pacific water into the eastern Indian Ocean in low latitudes, and may be a potential stratigraphic and paleoclimatic marker for times of low sea level when this westward near-surface flow was shut off (i.e., glacial maxima). An extensive region in the core of the subtropical gyre between 25°S and 35°S is relatively barren of Radiolaria, yet is marked by a characteristic assemblage distributed asymmetrically, perhaps reflecting the lack of a strong boundary current off the west coast of Australia. Assemblage boundaries in the vicinity of the eastward circumpolar flow are not strictly zonal, and may indicate significant deviations from the mean eastward flow as a necessary condition for conservation of potential vorticity when the flow encounters topographic irregularities.     

How marine currents influenced the widespread natural overseas dispersal of reptiles in the Western Indian Ocean region

In a recent contribution to this journal, Wilmé et al. (2016) proposed that the giant tortoises of the islands of the Western Indian Ocean (WIO: Aldabra, the Mascarenes, and the Granitic Seychelles) might have originated from translocation by early Austronesian sailors. Prompted by this paper we review recent literature and show that natural overseas dispersal was remarkably widespread in the colonization history of terrestrial reptiles in the WIO region. Almost 90% of the successful colonization events are supported by prevailing marine surface currents. However, these currents may change over geological (and evolutionary) time‐scales, and eddies and counter‐currents may facilitate transport against the main current direction. We review the cases of the extant and extinct WIO giant tortoises and suggest that the current distribution of all lineages can be convincingly explained by overseas dispersal.     

The evolution of the Indian Ocean parrots (Psittaciformes): extinction, adaptive radiation and eustacy

Parrots are among the most recognisable and widely distributed of all bird groups occupying major parts of the tropics. The evolution of the genera that are found in and around the Indian Ocean region is particularly interesting as they show a high degree of heterogeneity in distribution and levels of speciation. Here we present a molecular phylogenetic analysis of Indian Ocean parrots, identifying the possible geological and geographical factors that influenced their evolution. We hypothesise that the Indian Ocean islands acted as stepping stones in the radiation of the Old-World parrots, and that sea-level changes may have been an important determinant of current distributions and differences in speciation. A multi-locus phylogeny showing the evolutionary relationships among genera highlights the interesting position of the monotypic Psittrichas, which shares a common ancestor with the geographically distant Coracopsis. An extensive species-level molecular phylogeny indicates a complex pattern of radiation including evidence for colonisation of Africa, Asia and the Indian Ocean islands from Australasia via multiple routes, and of island populations ‘seeding’ continents. Moreover, comparison of estimated divergence dates and sea-level changes points to the latter as a factor in parrot speciation. This is the first study to include the extinct parrot taxa, Mascarinus mascarinus and Psittacula wardi which, respectively, appear closely related to Coracopsis nigra and Psittacula eupatria.     

Zoogeography of the shallow-water holothuroids of the western Indian Ocean

Aim To analyse the zoogeography of the shallow‐water holothuroids of the western Indian Ocean (WIO). Based on this analysis we ask to what extent differences in species’ ability to disperse across potential barriers provide an explanation for holothuroid zoogeography. Location Shallow‐waters (50 m isobaths) of the WIO, extending from Suez to Cape Town and from the coastline of East Africa upward to 65° E. Methods Data for the analysis were obtained from Samyn's (2003) monograph on the shallow‐water sea cucumbers of the WIO. A species presence/absence matrix with a resolution of 1° latitude/longitude was constructed. These cells were assigned to eight coarser operational geographical units, which were delimited on the basis of published faunistic and geological borders. The analytical zoogeographical methods employed were cluster analysis on several β‐diversity coefficients and parsimony analyses of endemicity. The influence of life‐history strategies on the distribution pattern was analysed through examination of latitudinal and longitudinal gradients, and by plotting cumulative curves for species number against range size. Results The shallow‐water holothuroid fauna of the WIO can be split into several biogeographical units. To the north, we found evidence that the northern Red Sea holothuroid fauna differs from that of the southern Red Sea. The latter has closest affinity with south‐east Arabia and the Persian Gulf, and thus the biogeographical barrier of Bab‐el‐Mandab nowadays seems to be of minor importance. The cold upwelling at the east coast of Somalia forms an effective barrier for holothuroids and especially those with lecitothrophic (short‐lived) larvae. Even though the circumtropical biogeographical pattern is not well resolved, important taxonomic turnovers suggest that it is composed of several distinct subprovinces. Taxonomic turnover is at least partially dictated by the dispersion capacity of the different orders. Main conclusions This study concludes that the WIO is best split into at least three biogeographical realms: (1) the Red Sea and associated Arab Basin, (2) the asymmetrical circumtropical region stretching from the horn of Africa to southern Mozambique, and (3) southern Africa. Conspicuous differences in dispersal abilities of the three dominant orders are identified. The biogeography of the WIO is best explained by: (1) species’ dispersion ability, (2) the prevalent current patterns, and (3) to a lesser, geographically limited extent, recent geological history. As a serendipitous discovery, we found that Rapoport's rule does not hold in the WIO.     

Bacterial Communities Associated with Porites White Patch Syndrome (PWPS) on Three Western Indian Ocean (WIO) Coral Reefs

The scleractinian coral Porites lutea, an important reef-building coral on western Indian Ocean reefs (WIO), is affected by a newly-reported white syndrome (WS) the Porites white patch syndrome (PWPS). Histopathology and culture-independent molecular techniques were used to characterise the microbial communities associated with this emerging disease. Microscopy showed extensive tissue fragmentation generally associated with ovoid basophilic bodies resembling bacterial aggregates. Results of 16S rRNA sequence analysis revealed a high variability between bacterial communities associated with PWPS-infected and healthy tissues in P. lutea, a pattern previously reported in other coral diseases such as black band disease (BBD), white band disease (WBD) and white plague diseases (WPD). Furthermore, substantial variations in bacterial communities were observed at the different sampling locations, suggesting that there is no strong bacterial association in Porites lutea on WIO reefs. Several sequences affiliated with potential pathogens belonging to the Vibrionaceae and Rhodobacteraceae were identified, mainly in PWPS-infected coral tissues. Among them, only two ribotypes affiliated to Shimia marina (NR043300.1) and Vibrio hepatarius (NR025575.1) were consistently found in diseased tissues from the three geographically distant sampling localities. The role of these bacterial species in PWPS needs to be tested experimentally.     

Rapid radiation in spiny lobsters (Palinurus spp) as revealed by classic and ABC methods using mtDNA and microsatellite data

Background  

Molecular tools may help to uncover closely related and still diverging species from a wide variety of taxa and provide insight into the mechanisms, pace and geography of marine speciation. There is a certain controversy on the phylogeography and speciation modes of species-groups with an Eastern Atlantic-Western Indian Ocean distribution, with previous studies suggesting that older events (Miocene) and/or more recent (Pleistocene) oceanographic processes could have influenced the phylogeny of marine taxa. The spiny lobster genus Palinurus allows for testing among speciation hypotheses, since it has a particular distribution with two groups of three species each in the Northeastern Atlantic (P. elephas, P. mauritanicus and P. charlestoni) and Southeastern Atlantic and Southwestern Indian Oceans (P. gilchristi, P. delagoae and P. barbarae). In the present study, we obtain a more complete understanding of the phylogenetic relationships among these species through a combined dataset with both nuclear and mitochondrial markers, by testing alternative hypotheses on both the mutation rate and tree topology under the recently developed approximate Bayesian computation (ABC) methods.     

Response of predatory snails to a novel prey following the geographic range expansion of an intertidal barnacle

During a geographic range expansion, the success of a species colonizing a new region may be influenced by how resident predators respond to this novel prey. The volcano barnacle Tetraclita rubescens has recently expanded its range > 300 km northward along the coast of California, USA. In the historic portion of its range, Tetraclita is preyed upon by a southern dogwhelk, Nucella emarginata. In newly colonized northern habitats, Tetraclita has joined an assemblage of mid-intertidal barnacles preyed upon by two species of northern dogwhelks (N. ostrina and N. canaliculata). Using a combination of field enclosures and laboratory experiments, we tested the impacts of northern whelks on volcano barnacles relative to other barnacle species. In the field, juvenile Tetraclita were rarely consumed. In laboratory trials with larger barnacles, Tetraclita were nearly immune to drilling by northern whelks, perhaps due to superior morphological defenses. In all experiments, prior encounters with Tetraclita did not appear to increase the frequency of predation on this barnacle; northern whelk species rarely preyed on Tetraclita even when collected from a site where this barnacle was abundant. In contrast, the southern whelk N. emarginata readily preyed on Tetraclita in laboratory trials, perhaps reflecting a longer shared evolutionary history between these species. Overall, our results suggest that the success of a population established beyond a species' historical range boundary may be influenced by the functional traits of that species in relation to the composition and evolutionary history of the surrounding community.     

Cranial morphometrics and mitochondrial DNA sequences distinguish cryptic species of the longface emperor (Lethrinus olivaceus), an emblematic fish of Indo-West Pacific coral reefs

Range-wide morphometric variability (cranial measurements) and genetic variability (nucleotide sequences of the cytochrome b gene) were investigated in the longface emperor, Lethrinus olivaceus (Lethrinidae), an emblematic large predatory fish of Indo-West Pacific coral reefs. Two cranial morphotypes were observed, one present from the Indian Ocean to the Coral Triangle and the other one, from the Coral Triangle to the western Central Pacific. The two morphotypes are concordant with reciprocally monophyletic mitochondrial lineages separated by 9.5% net nucleotide distance. These results suggest an old evolutionary history for L. olivaceus, which consists of two distinct species (Lethrinus sp. A in the Indian Ocean and Coral Triangle, Lethrinus sp. B in the western Pacific Ocean), whose distribution ranges meet or overlap in the eastern part of the Coral Triangle, in Taiwan and in West Papua. Lethrinus sp. A comprises two distinct mitochondrial lineages separated by 1.7% net nucleotide distance, one exclusive to the populations from the Indian Ocean, the other exclusive to Coral Triangle populations. The latter observation might be explained by vicariance, whereby the two lineages have been isolated from one another on either side of the Sunda Shelf because of low sea level in the Pleistocene. To clarify the nomenclature of this species complex, we recommend sequencing a fragment of the cytochrome b gene of the holotypes of L. olivaceus and of its first junior synonyms L. rostratus and L. waigiensis.