Carbonate sedimentation on subtropical shelves around Lord Howe Island and Balls Pyramid, Southwest Pacific

Kennedy, David M.; Woodroffe, Colin D.; Jones, Brian G.; Dickson, Mark E.; Phipps, C V G

doi:10.1016/s0025-3227(02)00406-1

Cited by 36 publications

(41 citation statements)

References 31 publications

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“…Concerns have been raised that the LHI system does not rule out geographic isolation of populations within the island, because the island may have been larger in the past (29). Studies of the geology and bathymetry indicate that the volcanic areas of LHI currently above sea level were eroded rapidly into their current state within 1-2 million years, after of the initial eruption and since then have been buffered from significant wave erosion by the presence of coral reefs (22,30,31). These studies also indicate that neither LHI nor Ball's Pyramid has subsided, but changes in sea level during glacial periods would have increased the terrestrial extent of both to the limits of the sea mounts upon which they sit (22,30,31).…”

Section: Discussionmentioning

confidence: 99%

“…Studies of the geology and bathymetry indicate that the volcanic areas of LHI currently above sea level were eroded rapidly into their current state within 1-2 million years, after of the initial eruption and since then have been buffered from significant wave erosion by the presence of coral reefs (22,30,31). These studies also indicate that neither LHI nor Ball's Pyramid has subsided, but changes in sea level during glacial periods would have increased the terrestrial extent of both to the limits of the sea mounts upon which they sit (22,30,31). It is questionable whether these increases in size would have generated greater ecological diversity (20) or habitats suitable for many of the species discussed here, because these species are largely restricted to volcanic soils.…”

Section: Discussionmentioning

confidence: 99%

“…To explore the spatial extent of LHI in the past and to assess the possibility of allopatric speciation within the island, we used ArcGIS V9.2 (ESRI, 2009) to generate a digital elevation model for the current extent of LHI and Ball's Pyramid, as well as for the submerged shelves to 100 m below current sea level based on recent bathymetric measurements (30).…”

Section: Methodsmentioning

confidence: 99%

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Speciation with gene flow on Lord Howe Island

Papadopulos

Baker

Crayn

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

191

207

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Understanding the processes underlying the origin of species is a fundamental goal of biology. It is widely accepted that speciation requires an interruption of gene flow between populations: ongoing gene exchange is considered a major hindrance to population divergence and, ultimately, to the evolution of new species. Where a geographic barrier to reproductive isolation is lacking, a biological mechanism for speciation is required to counterbalance the homogenizing effect of gene flow. Speciation with initially strong gene flow is thought to be extremely rare, and few convincing empirical examples have been published. However, using phylogenetic, karyological, and ecological data for the flora of a minute oceanic island (Lord Howe Island, LHI), we demonstrate that speciation with gene flow may, in fact, be frequent in some instances and could account for one in five of the endemic plant species of LHI. We present 11 potential instances of species divergence with gene flow, including an in situ radiation of five species of Coprosma (Rubiaceae, the coffee family). These results, together with the speciation of Howea palms on LHI, challenge current views on the origin of species diversity.Metrosideros | sympatric speciation | geography of speciation S peciation with strong gene flow is controversial among evolutionary biologists (1-3). Unlike speciation without gene flow (e.g., allopatric speciation and polyploid speciation) (4), it requires both divergent natural selection and a mechanism to promote nonrandom mating (5-7). Theoretically, these conditions might coincide via a pleiotropic magic trait, through linkage disequilibrium between genes involved in local adaptation and assortative mating, or because habitat differences within a species' range produce divergent genetic adaptations as well as plastic responses that confer reproductive isolation (e.g., environmentally controlled shifts in flowering time) (3,5,(7)(8)(9)(10). The most controversial incarnation of speciation occurs in sympatry, when gene exchange is high. Numerous definitions of sympatric speciation have been proposed since it was first outlined by Charles Darwin (11). Population genetic definitions focus on random mating with respect to location or habitat of the mating partners. For the biogeographic definition, which we adopt here, the absence of geographic isolation is the key criterion. The relative merits and disadvantages of both views continue to be debated (1-3, 7, 8, 12, 13).In plants, evidence for the influence of sympatric speciation with strong gene flow remains sparse, with a single study on the Howea palms of Lord Howe Island (LHI) presenting the only conclusive evidence (14, 15). On the other hand, sympatric speciation via polyploidization is well known in plants and is thought to have contributed significantly to species diversity but is not thought to involve ongoing gene flow (16). Very few studies have attempted to quantify the frequency of speciation without geographic isolation, and those that have indicate that it is excep...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Speciation with gene flow on Lord Howe Island

Papadopulos

Baker

Crayn

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

191

207

View full text Add to dashboard Cite

show abstract

“…Shelf planation is proposed to have occurred rapidly after the formation of the shield volcanoes (6-7 million years ago), with marine abrasion accounting for the majority (90%) of erosion [26]. Following shelf planation, carbonate sequences were deposited over the basalt platform [29,30,32], and accretionary and erosional processes during sea level lowstands shaped the variable nature of the shelf break.…”

Section: Comparison Of Shelf Morphologymentioning

confidence: 99%

“…Meso-scale mapping at the geomorphic and primary biome classification levels have also been produced for the shelves [30,[32][33][34][35] and habitat classifications have been performed for shallow and mesophotic assemblages [23,34,36,37]. Mapping of geomorphic features has been utilised in assessment reviews of the marine park zoning scheme and research planning [34,38].…”

Section: Introductionmentioning

confidence: 99%

Development of a Seamless, High-Resolution Bathymetric Model to Compare Reef Morphology around the Subtropical Island Shelves of Lord Howe Island and Balls Pyramid, Southwest Pacific Ocean

et al. 2018

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Lord Howe Island and Balls Pyramid are located approximately 600 km offshore of the southeastern Australian mainland, in the subtropical waters of the northern Tasman Sea. Lord Howe Island hosts the most southern coral reef in the Pacific Ocean, and the shelves surrounding both islands feature fossil coral reefs. This study creates a seamless, high-resolution (5 m cell size) bathymetry model of the two shelves to compare and contrast the extent of reef development and shelf morphology. This was produced by integrating satellite-derived depth data (derived to 35 m depth) and multibeam echosounder (MBES) data. Image partitioning and filtering improved the accuracy of the bathymetry estimates and the suitability for integration with MBES data. Diverse accretionary and erosional geomorphic features were mapped on both shelves, with fossil reefs dominating the shelves in 25-50 m depth. Similar patterns of shelf morphology were observed for the middle and outer shelves, while the inner shelf regions were most dissimilar, with reef development greater around Lord Howe Island compared to the more restricted inner shelf reefs around Balls Pyramid. Understanding the relative extent and morphology of shelf features provides insights into the geological and ecological processes that have influenced the formation of the shelves.

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The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution

Quartau

Madeira

Mitchell

et al. 2015

Geochem Geophys Geosyst

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Shelves surrounding reefless volcanic ocean islands are formed by surf erosion of their slopes during changing sea levels. Posterosional lava flows, if abundant, can cross the coastal cliffs and fill partially or completely the accommodation space left by erosion. In this study, multibeam bathymetry, highresolution seismic reflection profiles, and sediment samples are used to characterize the morphology of the insular shelves adjacent to Pico Island. The data show offshore fresh lava flow morphologies, as well as an irregular basement beneath shelf sedimentary bodies and reduced shelf width adjacent to older volcanic edifices in Pico. These observations suggest that these shelves have been significantly filled by volcanic progradation and can thus be classified as ''rejuvenated.'' Despite the general volcanic infilling of the shelves around Pico, most of their edges are below the depth of the Last Glacial Maximum, revealing that at least parts of the island have subsided after the shelves formed by surf erosion. Prograding lava deltas reached the shelf edge in some areas triggering small slope failures, locally decreasing the shelf width and depth of their edges. These areas can represent a significant risk for the local population; hence, their identification can be useful for hazard assessment and contribute to wiser land use planning. Shelf and subaerial geomorphology, magnetic anomalies and crustal structure data of the two islands were also interpreted to reconstruct the long-term combined onshore and offshore evolution of the Faial-Pico ridge. The subaerial emergence of this ridge is apparently older than previously thought, i.e., before 850 ka.

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Carbonate sedimentation on subtropical shelves around Lord Howe Island and Balls Pyramid, Southwest Pacific

Cited by 36 publications

References 31 publications

Speciation with gene flow on Lord Howe Island

Speciation with gene flow on Lord Howe Island

Development of a Seamless, High-Resolution Bathymetric Model to Compare Reef Morphology around the Subtropical Island Shelves of Lord Howe Island and Balls Pyramid, Southwest Pacific Ocean

The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution

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