An annotated list of the marine mollusks of Ascension Island, South Atlantic Ocean

Rosewater, Joseph

doi:10.5479/si.00810282.189

Cited by 31 publications

(35 citation statements)

References 6 publications

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“…The central Atlantic islands of Ascension and St. Helena show only a small degree of genetic isolation from the continental margins. Estimates of the isolation of these islands, based on the percentage of endemism (e.g., Mortensen 1933;Briggs 1974;Rosewater 1975;Pawson 1978;Lubbock 1980;Edwards 1990;Manning and Chace 1990;Biernbaum 1996), may in some cases be biased upward because of the erroneous elevation of their populations to separate specific status. The offshore islands of the eastern Pacific have provided opportunities for speciation dating back to the Pliocene.…”

Section: Discussionmentioning

confidence: 99%

Phylogeography of the Pantropical Sea Urchin Eucidaris in Relation to Land Barriers and Ocean Currents

Lessios¹,

Kessing²,

Robertson³

et al. 1999

Evolution

127

129

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Abstract.-The pantropical sea urchin genus Eucidaris contains four currently recognized species, all of them allopatric: E. metularia in the Indo-West Pacific, E. thouarsi in the eastern Pacific, E. tribuloides in both the western and eastern Atlantic, and E. clavata at the central Atlantic islands of Ascension and St. Helena. We sequenced a 640-bp region of the cytochrome oxidase I (COI) gene of mitochondrial DNA to determine whether this division of the genus into species was confirmed by molecular markers, to ascertain their phylogenetic relations, and to reconstruct the history of possible dispersal and vicariance events that led to present-day patterns of species distribution. We found that E. metularia split first from the rest of the extant species of the genus. If COI divergence is calibrated by the emergence of the Isthmus of Panama, the estimated date of the separation of the Indo-West Pacific species is 4.7-6.4 million years ago. This date suggests that the last available route of genetic contact between the Indo-Pacific and the rest of the tropics was from west to east through the Eastern Pacific Barrier, rather than through the Tethyan Sea or around the southern tip of Africa. The second cladogenic event was the separation of eastern Pacific and Atlantic populations by the Isthmus of Panama. Eucidaris at the outer eastern Pacific islands (Galapagos, Isla del Coco, Clipperton Atoll) belong to a separate clade, so distinct from mainland E. thouarsi as to suggest that this is a different species, for which the name E. galapagensis is revived from the older taxonomic literature. Complete lack of shared alleles in three allozyme loci between island and mainland populations support their separate specific status. Eucidaris galapagensis and E. thouarsi are estimated from their COI divergence to have split at about the same time that E. thouarsi and E. tribuloides were being separated by the Isthmus of Panama. Even though currents could easily convey larvae between the eastern Pacific islands and the American mainland, the two species do not appear to have invaded each other's ranges. Conversely, the central Atlantic E. clavata at St. Helena and Ascension is genetically similar to E. tribuloides from the American and African coasts. Populations on these islands are either genetically connected to the coasts of the Atlantic or have been colonized by extant mitochondrial DNA lineages of Eucidaris within the last 200,000 years. Although it is hard to explain how larvae can cross the entire width of the Atlantic within their competent lifetimes, COI sequences of Eucidaris from the west coast of Africa are very similar to those of E. tribuloides from the Caribbean. FST statistics indicate that gene flow between E. metularia from the Indian Ocean and from the western and central Pacific is restricted. Low gene flow is also evident between populations of E. clavata from Ascension and St. Helena. Rates of intraspecific exchange of genes in E. thouarsi, E. galapagenisis, and E. tribuloides, on the other hand, are hi...

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Section: Discussionmentioning

confidence: 99%

Phylogeography of the Pantropical Sea Urchin Eucidaris in Relation to Land Barriers and Ocean Currents

Lessios¹,

Kessing²,

Robertson³

et al. 1999

Evolution

127

129

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show abstract

“…Curtailment of the planktic phase could be an adaptation to avoid mass loss of larvae which might otherwise be carried by prevailing currents away from the islands and into the open ocean. This may explain why young oceanic islands, such as Ascension Island, tend to have a benthic fauna with predominantly planktic larvae (Rosewater, 1975;Pawson, 1978) while older islands have a higher proportion of species with nonplanktic larvae (cf. compilations of Thorson, 1965 The doubts concerning the applicability of ' Thorson's Rule ' are partially alleviated by Spight (1981), who presents some preliminary results of what will be the most thorough survey of latitudinal distribution of developmental types for marine invertebrates.…”

Section: )mentioning

confidence: 99%

Larval Ecology of Marine Benthic Invertebrates: Paleobiological Implications

1983

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Summary 1. Modes of larval development play important roles in the ecology, biogeography, and evolution of marine benthic organisms. Studies of the larval ecology of fossil organisms can contribute greatly to our understanding of such roles by allowing us to race effects on evolutionary time scales. 2. Modes of development can be inferred for well preserved molluscan fossils because the size of the initial larval shell (Protoconch I in gastropods, Prodissoconch I in bivalves) reflects egg size. Other morphological criteria are also available, and a comparative approach based on related taxa with known development may be the most reliable method. By combining larval and adult traits, it is possible to recognize modes of larval development in at least some fossil bryozoans, brachiopods, and echinoderms as well. (a) Planktotrophic larvae arise from small eggs, are released in enormous numbers with little parental investment per offspring, and suffer tremendous mortality during and shortly after a planktic existence. These larvae feed on the plankton during development, and are commonly capable of a prolonged free‐swimming existence, and thus wide dispersal. (b) Nonplanktotrophic larvae (which include both planktic lecithotrophic forms and ‘direct developers’) generally arise from large eggs, with relatively few young produced per parent. Relative to planktotrophic larvae, nonplanktotrophic larvae generally receive greater parental investment per larva, and larval mortality is generally lower. These larvae rely on yolk for nutrition during development, and planktic durations are generally much briefer than for species with planktotrophic larvae, so that dispersal capability is considerably less. Energetic investment per egg is generally higher than in planktotrophs, but as there are lower fecundities as well it is difficult to generalize about the total energetic cost of one mode of reproduction against the other. 3. Owing to the high dispersal capability of planktotrophic larvae, it has been suggested that species with such larvae will be geographically widespread, geologically long‐ranging, and exhibit low speciation and extinction rates. Species with nonplanktotrophic larvae will tend to be geographically more restricted, geologically short‐ranging, and exhibit high speciation and extinction rates (again, as a consequence of their characteristically low larval dispersal capabilities). 4. Recognition of differential dispersal capabilities can play a role in paleobiogeo‐graphic analyses. Concurrent study of the distribution of groups with contrasting modes of development will permit testing of hypotheses concerning timing, magnitudes and frequencies of migration and vicariance events. 5. Larval types are not randomly distributed in the oceans, but relationships with other aspects of the organisms' biology and habitats are very complex. Mode of development varies with: (a) Ecology. A simple r–––K model of adaptive strategies is clearly insufficient to explain the observed relationships: while many ‘equilibrium’ sp...

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“…Members of the genus Lasaea have been frequently collected from floating substrata (Rosewater 1975cited in Ó Foighil 1989. The small size of these species, their intertidal crevice-dwelling lifestyle, byssal attachment and brooding of directly developing juveniles (in many Lasaea species) are considered as morphological, behavioural and ecological pre-adaptations to rafting (Ó Foighil 1989, Ó Foighil & Jozefowicz 1999.…”

Section: Mollusca (Bivalvia)mentioning

confidence: 99%

The Ecology of Rafting in the Marine Environment. Ii. the Rafting Organisms and Community

Thiel¹,

Gutow²

2005

Oceanography and Marine Biology - An Annual Review

349

394

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Rafting of marine and terrestrial organisms has been reported from a variety of substrata and from all major oceans of the world. Herein we present information on common rafting organisms and on ecological interactions during rafting voyages. An extensive literature review revealed a total of 1205 species, for which rafting was confirmed or inferred based on distributional or genetic evidence. Rafting organisms comprised cyanobacteria, algae, protists, invertebrates from most marine but also terrestrial phyla, and even a few terrestrial vertebrates. Marine hydrozoans, bryozoans, crustaceans and gastropods were the most common taxa that had been observed rafting. All major feeding types were represented among rafters, being dominated by grazing/boring and suspension-feeding organisms, which occurred on all floating substrata. Besides these principal trophic groups, predators/scavengers and detritus feeders were also reported. Motility of rafting organisms was highest on macroalgae and lowest on abiotic substrata such as plastics and volcanic pumice. Important trends were revealed for the reproductive biology of rafting organisms. A high proportion of clonal organisms (Cnidaria and Bryozoa) featured asexual reproduction, often in combination with sexual reproduction. Almost all rafting organisms have internal fertilisation, which may be due to the fact that gamete concentrations in the rafting environment are too low for successful fertilisation of external fertilisers. Following fertilisation, many rafting organisms incubate their offspring in/on their body or deposit embryos in egg masses on rafts. Local recruitment, where offspring settle in the immediate vicinity of parents, is considered an important advantage for establishing persistent local populations on a raft, or in new habitats. Some organisms are obligate rafters, spending their entire life cycle on a raft, but the large majority of reported rafters are considered facultative rafters. These organisms typically live in benthic (or terrestrial) habitats, but may become dispersed while being confined to a floating item. Substratum characteristics (complexity, surface, size) have important effects on the composition of the rafting community. While at sea, ecological interactions (facilitation, competition, predation) contribute to the community succession on rafts. Organisms capable to compete for and exploit resources on a raft (space and food) will be able to persist throughout community succession. The duration of rafting voyages is closely related to rafting distances, which may cover various geographical scales. In chronological order, three features of an organism gain in importance during rafting, these being ability to (1) hold onto floating items, (2) establish and compete successfully and (3) develop persistent local MARTIN THIEL & LARS GUTOW 280 populations during a long voyage. Small organisms that do not feed on their floating substratum and, with asexual reproduction or direct development, combine all these features appear to be mos...

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An annotated list of the marine mollusks of Ascension Island, South Atlantic Ocean

Cited by 31 publications

References 6 publications

Phylogeography of the Pantropical Sea Urchin Eucidaris in Relation to Land Barriers and Ocean Currents

Phylogeography of the Pantropical Sea Urchin Eucidaris in Relation to Land Barriers and Ocean Currents

Larval Ecology of Marine Benthic Invertebrates: Paleobiological Implications

The Ecology of Rafting in the Marine Environment. Ii. the Rafting Organisms and Community

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