amphi-Atlantic Distribution Research Articles

Amphi-Atlantic distributions and cryptic species in Sacoglossan sea slugs

Nearly 13% of opisthobranch gastropods in the Atlantic Ocean are regarded as amphi-Atlantic (i.e. species occurring on both eastern and western coastlines of the Atlantic realm). This assumption has been broadly based on morpho-anatomical similarities and has rarely been tested within a molecular phylogenetic framework. Among opisthobranchs, the order Sacoglossa is renowned for its difficult and confusing species taxonomy, particularly in some genera like Elysia, where several cases of cryptic speciation have been documented. Moreover, the width of the Atlantic realm poses a serious challenge to the idea of trans-Atlantic dispersal, particularly in nonplanktotrophic species. The species Bosellia mimetica, Elysia timida and Thuridilla picta are three sacoglossan opisthobranchs with amphiAtlantic status, but doubts have been raised about the conspecificity of eastern and western populations. Here we used methods to test molecular phylogenetic whether the Atlantic Ocean constitutes a barrier for dispersal and hence whether eastern and western populations belong to the same species. We used the criteria of divergence and reciprocal monophyly, supported by concordant genealogically independent genetic markers, to define species. Maximum-likelihood and Bayesian analyses of partial DNA sequences of the mitochondrial cytochrome c oxidase subunit I and 16S rRNA genes and nuclear gene Histone-3 (H3) were used to produce phylogenetic trees. We conclude that the eastern Atlantic species B. mimetica is not amphi-Atlantic, although the H3 gene did not recover reciprocal monophyly between western and eastern populations, perhaps in a result of incomplete lineage-sorting. Elysia timida is the only species showing an amphi-Atlantic distribution, but possibly due to recent introduction in the tropical western Atlantic. Thuridilla picta is restricted to the western Atlantic and therefore not amphi-Atlantic. Populations of ‘T. picta’ inhabiting the Macaronesian archipelagos of Azores and Madeira are a colour form of the eastern Atlantic T. hopei. Our results highlight the difficulty surrounding systematics of Sacoglossa sea slugs and provide further evidence that cryptic speciation is common in the group.

Introduced or glacial relict? Phylogeography of the cryptogenic tunicate Molgula manhattensis (Ascidiacea, Pleurogona)

Aim The tunicate Molgula manhattensis has a disjunct amphi-Atlantic distribution and a recent history of world-wide introductions. Its distribution could be the result of regional extinctions followed by post-glacial recolonization, or anthropogenic dispersal. To determine whether the North Atlantic distribution of M. manhattensis is natural or human-mediated, we analysed mtDNA cytochrome c oxidase subunit I (COI) sequence variation in individuals from cryptogenic and introduced ranges. Location North Atlantic Europe and America; Black Sea; San Francisco Bay; Osaka Bay. Methods Nuclear 18S rDNA sequences were used to resolve phylogenetic relationships and mtDNA COI sequences for phylogeographic analyses. Results Phylogenetic analyses confirmed that M. manhattensis and M. socialis, which are frequently confused, are distinct species. MtDNA haplotype diversity was nearly three times higher with deeper relationships among haplotypes on the North-east American coast than in Europe. Diversity declined from south to north in America but not in Europe. In areas of known introductions (Black Sea, Japan, San Francisco Bay), M. manhattensis showed variable levels of haplotype diversity. Medium-to-high-frequency haplotypes originating from the North-west Atlantic were present in two locations of known introductions, but not in Europe. Private haplotypes were found on both sides of the Atlantic and in introduced populations. The mismatch distribution for the North-east Atlantic coast indicates a recent expansion. Main conclusions Molgula manhattensis is native in North-east America. However, whether it was introduced or is native to Europe remains equivocal. Additional sampling might or might not reveal the presence of putative private European haplotypes in America. The low European diversity may be explained by low effective population size and a recent expansion, or by low propagule pressure of anthropogenic introduction. Absence of medium-to-high-frequency American haplotypes in Europe may be the result of exclusive transport from southern ports, or long-term residence. These arguments are ambiguous, and M. manhattensis remains cryptogenic in Europe.

Session 1

The assemblages of the demersal and deep-water fish assemblages of the Cabo Verde archipelago are described for the first time from a total of 20 longline hauls that extends from coastline to 1200 m water depth. A total of 98 species from 47 different families were caught, and despite the changes of biogeographic affinities with depth, the majority of the species are from a Subtropical and Tropical origin or have a broad geographic distribution (Wide and Amphiatlantic distributions) with small affinities with the Macaronesian islands and the Mediterranean. Depth distribution profiles show a clear turnover of species with depth, and an increase in the depth distribution range of the deeper living species. Furthermore, the indices of species abundance, biomass and the number of species caught, significantly decreased with increasing depth. Four main fish assemblages in a depth-aligned structure are proposed in the present work. A shelf assemblage mainly distributed above the 150 m depth strata, a shelf-break/upper-slope assemblage mainly between the 150–350 m depth strata, a deep/upper-slope assemblage between the 300–600 m depth strata, and a mid- deep/mid-slope assemblage mainly distributed below the 600 m. Species abundances and diversity found below 200 m is relatively low compared with shallow waters. The observed depth zonation of the slope assemblages, roughly agrees with the expected occurrence or influence of different water masses: shelf and surface mixing and seasonal thermocline depth zone, the depth range of occurrence of the intermediate waters (North Atlantic Central Water—NACW), the South Atlantic Central Water—SACW), and Atlantic Equatorial Water—AEW), a mixing or overlapping zone of previous intermediate water masses with the Antarctic Intermediate Water (AAIW), and the Mediterranean Outflow Water (MOW), and a deeper zone where the AAIW predominate.

Spawning, Development, and the Duration of Larval Life in a Deep-Sea Cold-Seep Mussel

We describe culturing techniques and development for the cold-seep mussel "Bathymodiolus" childressi, the only deep-sea bivalve for which development has been detailed. Spawning was induced in mature mussels by injection of 2 mmol l(-1) serotonin into the anterior adductor muscle. The mean egg diameter is 69.15 +/- 2.36 microm (+/-S.D.; n = 50) and eggs are negatively buoyant. Cleavages are spiral and at 7-8 degrees C occur at a rate of one per 3-9 h through hatching, with free-swimming blastulae hatching by 40 h and shells beginning to develop by day 12. When temperature was raised to 12-14 degrees C after hatching, larvae developed to D-shell veligers by day 8 without being fed. Egg size and larval shell morphology indicate that "B." childressi has a planktotrophic larva, but we did not observe feeding in culture. Wide distribution of this species throughout the Gulf of Mexico and amphi-Atlantic distributions of closely related congeners suggest that larvae may spend extended periods in the plankton. Duration of larval life was estimated for "B." childressi by comparing calculated settlement times to known spawning seasons. These estimates suggest variability in the larval duration, with individuals spending more than a year in the plankton.

Cancrincolidae (Copepoda, Harpacticoida) associated with land crabs: A semiterrestrial leaf of the ameirid tree

Morphological evidence suggests harpacticoid copepods have recurrently entered into symbiosis with other crustaceans but only members of the family Cancrincolidae have successfully made the transition from marine habitats to semiterrestrial hosts. Cancrincolids are primarily amphi-Atlantic in distribution (with one outlier in the western Pacific) and typically inhabit the gill chambers of grapsoidean land crabs belonging to the families Grapsidae, Sesarmidae, Varunidae and Gecarcinidae. Morphologically, they are difficult to place because they exhibit unusual autapomorphies and the shared derived characters claimed to unite them with the primitively marine Ameiridae are equivocal. Both maximum parsimony and Bayesian inference solutions based on SSU rDNA gene sequences show topological congruence in placing the Cancrincolidae within the Ameiridae and in firmly resolving it as the sistergroup of taxa that have been reported as obligate or commensal associates of crayfish. This relationship is further supported by swimming leg sexual dimorphism and mandibular palp morphology. Morphological comparison with ameirid copepods revealed the majority of synapomorphies previously proposed in support of cancrincolid monophyly and familial distinctiveness can be attributed to heterochrony. The progressive evolution of cancrincolid associates appears to be largely concordant with the sequential adaptation to terrestriality by their grapsoidean hosts. The current amphi-Atlantic distribution of Cancrincola may suggest its possibly free-living ancestor had already assumed a virtually continuous distribution along the northern seaboard of Gondwana prior to the opening of the South Atlantic during the early Cretaceous, implying symbiotic relationships were established only much later when grapsoidean crabs started to emerge, radiate and diversify in the mid-Tertiary (15–35 mya). The adoption of semi-terrestriality in cancrincolid copepods can be viewed as yet another independent attempt (incursion) to colonize low-salinity environments by members of the family Ameiridae. The possible sistergroup relationships of the Ameiridae and the position of the genus Argestigens Willey are discussed.

Recent divergence, intercontinental dispersal and shared polymorphism are shaping the genetic structure of amphi‐Atlantic peatmoss populations

Several lines of evidence suggest that recent long-distance dispersal may have been important in the evolution of intercontinental distribution ranges of bryophytes. However, the absolute rate of intercontinental migration and its relative role in the development of certain distribution ranges is still poorly understood. To this end, the genetic structure of intercontinental populations of six peatmoss species showing an amphi-Atlantic distribution was investigated using microsatellite markers. Methods relying on the coalescent were applied (IM and MIGRATE) to understand the evolution of this distribution pattern in peatmosses. Intercontinental populations of the six peatmoss species were weakly albeit significantly differentiated (average F(ST) = 0.104). This suggests that the North Atlantic Ocean is acting as a barrier to gene flow even in bryophytes adapted to long-range dispersal. The im analysis suggested a relatively recent split of intercontinental populations dating back to the last two glacial periods (9000-289,000 years ago). In contrast to previous hypotheses, analyses indicated that both ongoing migration and ancestral polymorphism are important in explaining the intercontinental genetic similarity of peatmoss populations, but their relative contribution varies with species. Migration rates were significantly asymmetric towards America suggesting differential extinction of genotypes on the two continents or invasion of the American continent by European lineages. These results indicate that low genetic divergence of amphi-Atlantic populations is a general pattern across numerous flowering plants and bryophytes. However, in bryophytes, ongoing intercontinental gene flow and retained shared ancestral polymorphism must both be considered to explain the genetic similarity of intercontinental populations.

Recent oceanic long-distance dispersal and divergence in the amphi-Atlantic rain forest genus Renealmia L.f. (Zingiberaceae)

Renealmia L.f. (Zingiberaceae) is one of the few tropical plant genera with numerous species in both Africa and South America but not in Asia. Based on phylogenetic analysis of nuclear ribosomal internal transcribed spacer (ITS) and chloroplast trnL-F DNA, Renealmia is shown to be monophyletic with high branch support. Low sequence divergence found in the two genome regions (ITS: 0–2.4%; trnL-F: 0–1.9%) suggests recent diversification within the genus. Molecular divergence age estimates give further support to the recent origin of the genus and show that Renealmia has attained its amphi-Atlantic distribution by an oceanic long-distance dispersal event from Africa to South America during the Miocene or Pliocene (15.8–2.7 My ago). Some support is found for the hypothesis that speciation in neotropical Renealmia was influenced by the Andean orogeny. Speciation has been approximately simultaneous on both sides of the Atlantic, but increased taxon sampling is required to compare the speciation rates between the New World and Old World tropics.

Lack of genetic variation in mtDNA sequences over the amphiatlantic distribution range of the ascidian Ecteinascidia turbinata

The colonial ascidian Ecteinascidia turbinata Herdman 1880 (Phlebobranchiata; Perophoridae) is a widespread tunicate found in tropical and subtropical waters on both sides of the Atlantic and in the Mediterranean Sea (Berrill, 1932). This species has often been reported to foul floats and other human-made structures (e.g. WHOI, 1952). Intercontinental dispersion of this species is attributable to maritime transport as the larvae have short planktonic life-spans (Bingham and Young, 1991) and colonies can attach to ship hulls (Calder et al., 1966). Although introductions of benthic invertebrates may originate in marginal marine habitats (such as marinas), they can eventually spread to open habitats (Turon et al., 2007). In addition, this species has recently elicited interest because one of its secondary metabolites, Ecteinascidin-743, displayed remarkable antitumor activities in in vitro and in vivo models (Rinehart et al., 1990; Sakai et al., 1992; Valoti et al., 1998; Izbicka et al., 1998). In order to obtain the amount required for clinical trials, aquaculture of E. turbinata was intensively developed in Formentera (Balearic Islands, Spain) by Pharmamar S. A. (Spain) and in Long Key (Florida, USA) by CalBioMarine Technologies (Carlsbad, CA) (Carballo et al., 1997; Pomponi, 1999). Analysis of mtDNA sequence data has proven to be a useful tool for tracing recent evolutionary history, such as founder events, population bottlenecks and phylogeography in marine organisms (Gopurenko et al., 1999; King et al., 1999; Wilke and Davis, 2000). The mitochondrial gene cytochrome c oxidase subunit I (COI) has been a molecule of choice to conduct intra-specific phylogeographic studies due to its high degree of variability (e.g. Avise, 2000; Hamm and Burton, 2000; Castilla et al., 2002; Duran et al., 2004b; Reuschel and Schubart, 2005). Among marine invertebrates, the only prominent examples of almost negligible levels of intra-specific variation in COI have been reported for basal Phyla such as sponges and anthozoans (Shearer et al., 2002; Frances and Hoover, 2002; Duran et al., 2004a). In ascidians, the COI gene has proven to be highly polymorphic (Tarjuelo et al., 2001, 2004; Castilla et al., 2002; Turon et al., 2003; Turon and Lopez-Legentil, 2004; Lopez-Legentil and Turon, 2006; Lopez-Legentil et al., 2006). The objective of this study was to analyze a fragment of the mtDNA gene COI in an attempt to determine the intraspecific genetic structure and phylogeography of the ascidian E. turbinata over its amphiatlantic distribution range.

Signatures of seaway closures and founder dispersal in the phylogeny of a circumglobally distributed seahorse lineage.

BackgroundThe importance of vicariance events on the establishment of phylogeographic patterns in the marine environment is well documented, and generally accepted as an important cause of cladogenesis. Founder dispersal (i.e. long-distance dispersal followed by founder effect speciation) is also frequently invoked as a cause of genetic divergence among lineages, but its role has long been challenged by vicariance biogeographers. Founder dispersal is likely to be common in species that colonize remote habitats by means of rafting (e.g. seahorses), as long-distance dispersal events are likely to be rare and subsequent additional recruitment from the source habitat is unlikely. In the present study, the relative importance of vicariance and founder dispersal as causes of cladogenesis in a circumglobally distributed seahorse lineage was investigated using molecular dating. A phylogeny was reconstructed using sequence data from mitochondrial and nuclear markers, and the well-documented closure of the Central American seaway was used as a primary calibration point to test whether other bifurcations in the phylogeny could also have been the result of vicariance events. The feasibility of three other vicariance events was explored: a) the closure of the Indonesian Seaway, resulting in sister lineages associated with the Indian Ocean and West Pacific, respectively; b) the closure of the Tethyan Seaway, resulting in sister lineages associated with the Indo-Pacific and Atlantic Ocean, respectively, and c) continental break-up during the Mesozoic followed by spreading of the Atlantic Ocean, resulting in pairs of lineages with amphi-Atlantic distribution patterns.ResultsComparisons of pairwise genetic distances among the seahorse species hypothesized to have diverged as a result of the closure of the Central American Seaway with those of published teleost sequences having the same distribution patterns show that the seahorses were among the last to diverge. This suggests that their cladogenesis was associated with the final closure of this seaway. Although two other divergence events in the phylogeny could potentially have arisen as a result of the closures of the Indonesian and Tethyan seaways, respectively, the timing of the majority of bifurcations in the phylogeny differed significantly from the dates of vicariance events suggested in the literature. Moreover, several divergence events that resulted in the same distribution patterns of lineages at different positions in the phylogeny did not occur contemporaneously. For that reason, they cannot be the result of the same vicariance events, a result that is independent of molecular dating.ConclusionInterpretations of the cladogenetic events in the seahorse phylogeny based purely on vicariance biogeographic hypotheses are problematic. We conclude that the evolution of the circumglobally distributed seahorse lineage was strongly influenced by founder dispersal, and suggest that this mode of speciation may be particularly important in marine organisms that lack a pelagic dispersal phase and instead disperse by means of rafting.

Phylogeny and Biogeography of <I>Pomaria</I> (Caesalpinioideae: Leguminosae)

Pomaria, traditionally placed in Hoffmannseggia or Caesalpinia, is shown to be a well-supported group of 15 species related to the Erythrostemon group of Caesalpinia sensu lato. Monophyly is well supported by analyses of both nuclear and chloroplast DNA data and by the presence of several unique morphological characters. Nine species of the genus are distributed in the arid and montane regions of the southwestern United States and adjacent Mexico, three species occur in temperate eastern South America, and three species are native to southern Africa. The genus thus exhibits both a New World amphitropical and a New World-African amphi-Atlantic distribution pattern. A biogeographical analysis suggests two dispersals within the genus account for the present distribution: one from North America to Africa and second from North America to South America.

Deep-sea pycnogonids from the North Atlantic and their distribution in the World Ocean

The information on the composition and distribution of present-day pycnogonids in different regions of the World Ocean and, especially, in the northern part of the Atlantic Ocean acquired during the past decades allowed us to perform a biogeographical analysis of these animals, which represent a permanent component of bottom communities. For 34 species of sea spiders (Pycnogonida) found in the North Atlantic deeper than 2 km, ten types of geographical distribution were recognized. Half of the species identified represent Atlantic forms, and 41% of them are endemic forms with West-Atlantic, East-Atlantic, amphi-Atlantic, and central-Atlantic distributions. The other half of the deep-sea Atlantic species have broad geographical ranges. Among them, 11.7% are Atlantic-Pacific species, 14.7% dwell in the Atlantic and West Pacific, 8.9% are low-latitudinal panocaanic species, and 14.7% are panoceanic species able to penetrate to higher latitudes. The zoogeographical species composition shows a significant independence of this fauna in the northern Atlantic Ocean and its relation to the Pacific and Indian oceans. At present, these relations are probably maintained via the temperate latitudes of the Southern Hemisphere and via the Drake Passage; meanwhile, it seems that, previously, they were realized possibly via the ancient Tethys Ocean.

From Europe to America: Pliocene to Recent trans-Atlantic expansion of cold-water North Atlantic molluscs

Data on the geographical distribution, phylogeny and fossil record of cool-temperate North Atlantic shell-bearing molluscs that live in waters shallower than 100 m depth belong to two biogeographic provinces, one in eastern North America north of Cape Cod, the other in northern Europe. Amphi-Atlantic species, which are found in both provinces, comprise 30.8% of the 402 species in the northeastern Atlantic and 47.3% of the 262 species in the northwestern Atlantic. Some 54.8% of these amphi-Atlantic species have phylogenetic origins in the North Pacific. Comparisons among fossil Atlantic faunas show that amphi-Atlantic distributions became established in the Middle Pliocene (about 3.5 million years ago), and that all represent westward expansions of European taxa to North America. No American taxa spread eastward to Europe without human assistance. These results are in accord with previous phylogeographic studies among populations within several amphi-Atlantic species. Explanations for the unidirectional expansion of species across the Atlantic remain uncertain, but may include smaller size and greater prior extinction of the North American as compared to the European fauna and biased transport mechanisms. Destruction of the European source fauna may jeopardize faunas on both sides of the Atlantic.

Three amphi-Atlantic century-scale cold events during the Bølling-Allerød warm period

Oxygen isotope composition of carbonates in the sediments of Crawford Lake, southern Canada, reveals multiple climatic events during the last deglaciation, including the Bølling warming, intra-Allerød cold period, Younger Dryas, Preboreal Oscillation, and early-Holocene 8.2-ka cooling. Here we present a high-resolution record (~50-yr sampling interval) of oxygen isotopes from this site during the Bølling-Allerød warm period and discuss its significance by comparing it with other records around the North Atlantic. These new data show three century-scale cold events, including the intra-Bølling cold period, Older Dryas, and intra-Allerød cold period. These climatic events correlate well in sequence and relative magnitude with those found in Greenland ice cores, European lacustrine sediments, and Atlantic Ocean sediments. Three similar oscillations in glaciochemical records from GISP2 ice core imply shift in atmospheric circulation patterns. The amphi-Atlantic distribution of these climate events suggests that these events likely originated from the North Atlantic Ocean and that climatic signals were transmitted through the atmosphere.

Ctenodrilus serratus (Polychaeta: Ctenodrilidae) is a truly amphi-Atlantic meiofauna species – evidence from molecular data

Specimens of the meiofaunal polychaete Ctenodrilus serratus from six localities on both sides of the North Atlantic were examined by RAPD-PCR and sequencing of the internal transcribed spacers (ITS1, ITS2) and 5.8S DNA. None of the populations showed any monomorphic diagnostic DNA fragments, but rather had a highly polymorphic band pattern; cluster analyses revealed no site-specific clusters of the specimens investigated. Furthermore, sequences were almost identical in populations off the coasts of Europe and the eastern United States, whereas the Bermuda specimens differed to some extent in ITS2. These results indicate the existence of a common gene pool and demonstrate an amphi-Atlantic distribution pattern of the species. Trans-Atlantic dispersal of individuals, by whatever means, must be inferred.

Amphi-Atlantic distribution of the Mancocumatinae (Cumacea: Bodotriidae), with description of a new genus dwelling in marine lava caves of Tenerife (Canary Islands)

A new cumacean genus and species, Speleocuma guanche gen et sp. nov., belonging to the subfamily Mancocumatinae Watling 1977, is described from marine lava caves of Tenerife, Canary Islands. This genus differs from others in the subfamily in having two pairs of pleopods in males and exopods on first to third pereopods, but not on fourth pereopod, in both sexes. Correlation between phylogenetic relationships of the new genus and the geological history of the Canarian archipelago points to a probable origin of this endemism: the subfamily Mancocumatinae show a disjunct distribution on both sides of the Atlantic Ocean, a pattern which has been associated with fauna of Tethyan origin. It is suggested that present day genera of the subfamily evolved from a common shallow water ancestor living in the late Mesozoic (c. 120 Myr BP), when the opening of the Atlantic Ocean had begun. It survived in shallow waters off the west African coast before the emergence of the Canary Islands from the sea floor. Later on, between the late Cretaceous and the Mio-Pliocene, it was able to colonize crevicular habitats of the eastern Canary Islands through continental or land bridges. Finally, their numbers increased to occupy more recent biotops like flooded lava tube caves as well as westward islands such as Tenerife.

Age of association between the nurse shark, Ginglymostoma cirratum, and tapeworms of the genus Pedibothrium (Tetraphyllidea: Onchobothriidae): implications from geography

Abstract The first records of the tapeworm genus Pedibothrium from nurse sharks ( Ginglymostoma cirratum ) in the eastern Pacific and eastern Atlantic Oceans provide new insights on the age of the association between these tapeworms and this host. Four individuals of G. cirratum examined from the southern tip of the Baja Peninsula, Mexico, were found to host P. manteri and P. brevispine . Tapeworm specimens discovered in the collection of J. Cadenet, taken from G. cirratum off Goree near Dakar, Senegal in 1947, were of P. globicephalum and P. manteri . These tapeworm faunas are consistent with those found previously in small and large nurse sharks, respectively, in the western Atlantic Ocean. The distributional data, combined with the non-vagile habits of the nurse shark, indicate this host–parasite association dates from the most recent completion of the Panamanian Isthmus, approximately 2 Mya. This suggests that P. manteri and P. brevispine have remained unchanged for at least 2 Myr. The data from the eastern Atlantic Ocean are less informative. The amphi-Atlantic distribution of P. manteri and P. globicephalum in G. cirratum may have resulted from vicariant events associated with the formation of the Atlantic Ocean. However, fossils of at least two extinct species of Ginglymostoma are also known from both sides of the Atlantic Ocean. Short of parallel evolution of three different species of Ginglymostoma on either side of the Atlantic Ocean, these data seem more consistent with dispersal as an explanation for this disjunction and are thus of limited utility for extending the age of this host–parasite association at this time. Analysis of the degree of genetic divergence among individuals of G. cirratum and among individuals of the broadly distributed species of Pedibothrium from all three localities would be extremely interesting.

Age of association between the nurse shark, Ginglymostoma cirratum, and tapeworms of the genusPedibothrium (Tetraphyllidea: Onchobothriidae): implications from geography

The first records of the tapeworm genus Pedibothrium from nurse sharks (Ginglymostoma cirratum) in the eastern Pacific and eastern Atlantic Oceans provide new insights on the age of the association between these tapeworms and this host. Four individuals of G. cirratum examined from the southern tip of the Baja Peninsula, Mexico, were found to host P. manteri and P. brevispine. Tapeworm specimens discovered in the collection of J. Cadenet, taken from G. cirratum off Gorée near Dakar, Senegal in 1947, were of P. globicephalum and P. manteri. These tapeworm faunas are consistent with those found previously in small and large nurse sharks, respectively, in the western Atlantic Ocean. The distributional data, combined with the non-vagile habits of the nurse shark, indicate this host–parasite association dates from the most recent completion of the Panamanian Isthmus, approximately 2 Mya. This suggests that P. manteri and P. brevispine have remained unchanged for at least 2 Myr. The data from the eastern Atlantic Ocean are less informative. The amphi-Atlantic distribution of P. manteri and P. globicephalum in G. cirratum may have resulted from vicariant events associated with the formation of the Atlantic Ocean. However, fossils of at least two extinct species of Ginglymostoma are also known from both sides of the Atlantic Ocean. Short of parallel evolution of three different species of Ginglymostoma on either side of the Atlantic Ocean, these data seem more consistent with dispersal as an explanation for this disjunction and are thus of limited utility for extending the age of this host–parasite association at this time. Analysis of the degree of genetic divergence among individuals of G. cirratum and among individuals of the broadly distributed species of Pedibothrium from all three localities would be extremely interesting.

Additions to the Marine Algal (Seaweed) Flora of the Azores

Ten species of benthic marine algae, new distribution records for the Azores achipelago, are itemised; two other species records (Heterosiphonia crispella and Laminaria ochroleuca) are confirmed for the islands. Six species (Bryopsis pennata, Cottoniella filamentosa, Dasya baillouviana, Feldmannia paradoxa, Heterosiphonia crispella and Lomentaria clavellosa) show an amphi-Atlantic distribution pattern; four (Bonnemaisonia asparagoides, Laminaria ochroleuca, Pterosphonia ardreana and Stylonema cornu-cervi) show a European-African-Mediterranean distribution pattern. The occurrence of Dudresnaya crassa, a western Atlantic warm-water species, represents an extension of its known distributional range to the east. An Ahnfeltiopsis was found which resembled A. intermedia, a species that occurs in the Atlantic Ocean to the south of the Azores.

A new species of Araripesuchus (Crocodylomorpha, Mesoeucrocodylia) from the lower Cretaceous of Patagonia (Argentina)

ABSTRACT A new species of the genus Araripesuchus from the Albian-Cenomanian locality of the El Chocón (Neuquén Province, Argentina) is described. The diagnosis of the genus is reviewed and its phylogenetic placement within Crocodylomorpha discussed. Araripesuchus is proposed here as being the sister taxon of Neosuchia, corroborating previous phylogenetic analysis. The new species, Araripesuchus patagonicus, differs from the type species, A. gomesii in the relationships of the prefronto-nasal and lachrymo-nasal sutures, the dermal placement of the postorbital bar on the medial side of the jugal, and the greater extension of the squamosals in the skull dorsum. The African species, “Araripesuchus” wegeneri, does not share the diagnostic traits of the genus, and its reassignment to a new genus needs to be considered. The phylogenetic context of Araripesuchus and “A.” wegeneri permits a reanalysis of the role played by their amphiatlantic distribution in the Aptian-Albian. “Araripesuchus” wegeneri and the South American forms might share a pre-Aptian common ancestor, and have been already differentiated and isolated in the African and South American continents by the time of the Aptian-Albian.

Chapmannia (Leguminosae‐Stylosanthinae) extended

The circumscription of Chapmannia, previously considered a monotypic genus confined to Florida, is extended to include also Pachecoa (with a single species in Mexico, Guatemala and Venezuela) and Arthrocarpum (with one species on Socotra and one species in Somalia). The new combinations C. prismatica, C. somalensis and C. gracilis are made. Three new species, C. sericea, C. tinireana and C. reghidensis, are described and illustrated, all from Socotra (Yemen). Chapmannia, with this new circumscription, becomes a markedly disjunct genus with two species in America and five species in the Horn of Africa region. It is suggested that this amphiatlantic distribution can be interpreted in the context of the boreotropics hypothesis.