Research article

Background: An increasing number of studies demonstrate that genetic differentiation and speciation in the sea occur over much smaller spatial scales than previously appreciated given the wide distribution range of many morphologically defined coral reef invertebrate species and the presumed dispersal-enhancing qualities of ocean currents. However, knowledge about the processes that lead to population divergence and speciation is often lacking despite being essential for the understanding, conservation, and management of marine biodiversity. Sponges, a highly diverse, ecologically and economically important reef-invertebrate taxon, exhibit spatial trends in the Indo-West Pacific that are not universally reflected in other marine phyla. So far, however, processes generating those unexpected patterns are not understood.Results: We unraveled the phylogeographic structure of the widespread Indo-Pacific coral reef sponge Leucetta chagosensis across its known geographic range using two nuclear markers: the rDNA internal transcribed spacers (ITS 1&2) and a fragment of the 28S gene, as well as the second intron of the ATP synthetase beta subunit-gene (ATPSb-iII). This enabled the detection of several deeply divergent clades congruent over both loci, one containing specimens from the Indian Ocean (Red Sea and Maldives), another one from the Philippines, and two other large and substructured NW Pacific and SW Pacific clades with an area of overlap in the Great Barrier Reef/Coral Sea...Conclusion: We argue that both founder and vicariance events during the late Pliocene and Pleistocene were responsible to varying degrees for generating the deep phylogeographic structure. This structure was perpetuated largely as a result of the life history of L. chagosensis, resulting in high levels of regional isolation. Reciprocally monophyletic populations constitute putative sibling (cryptic) species, while population para- and polyphyly may indicate incipient speciation processes. The genetic diversity and biodiversity of tropical Indo-Pacific sponges appears to be substantially underestimated since the high level of genetic divergence is not necessarily manifested at the morphological level.researc

Deep genetic divergences among Indo-Pacific populations of the coral reef sponge Leucetta chagosensis (Leucettidae): Founder effects, vicariance, or both?

<p>Abstract</p> <p>Background</p> <p>An increasing number of studies demonstrate that genetic differentiation and speciation in the sea occur over much smaller spatial scales than previously appreciated given the wide distribution range of many morphologically defined coral reef invertebrate species and the presumed dispersal-enhancing qualities of ocean currents. However, knowledge about the processes that lead to population divergence and speciation is often lacking despite being essential for the understanding, conservation, and management of marine biodiversity. Sponges, a highly diverse, ecologically and economically important reef-invertebrate taxon, exhibit spatial trends in the Indo-West Pacific that are not universally reflected in other marine phyla. So far, however, processes generating those unexpected patterns are not understood.</p> <p>Results</p> <p>We unraveled the phylogeographic structure of the widespread Indo-Pacific coral reef sponge <it>Leucetta chagosensis </it>across its known geographic range using two nuclear markers: the rDNA internal transcribed spacers (ITS 1&2) and a fragment of the 28S gene, as well as the second intron of the <it>ATP synthetase beta subunit</it>-gene (<it>ATPSb</it>-iII). This enabled the detection of several deeply divergent clades congruent over both loci, one containing specimens from the Indian Ocean (Red Sea and Maldives), another one from the Philippines, and two other large and substructured NW Pacific and SW Pacific clades with an area of overlap in the Great Barrier Reef/Coral Sea. Reciprocally monophyletic populations were observed from the Philippines, Red Sea, Maldives, Japan, Samoa, and Polynesia, demonstrating long-standing isolation. Populations along the South Equatorial Current in the south-western Pacific showed isolation-by-distance effects. Overall, the results pointed towards stepping-stone dispersal with some putative long-distance exchange, consistent with expectations from low dispersal capabilities.</p> <p>Conclusion</p> <p>We argue that both founder and vicariance events during the late Pliocene and Pleistocene were responsible to varying degrees for generating the deep phylogeographic structure. This structure was perpetuated largely as a result of the life history of <it>L. chagosensis</it>, resulting in high levels of regional isolation. Reciprocally monophyletic populations constitute putative sibling (cryptic) species, while population para- and polyphyly may indicate incipient speciation processes. The genetic diversity and biodiversity of tropical Indo-Pacific sponges appears to be substantially underestimated since the high level of genetic divergence is not necessarily manifested at the morphological level.</p

A horizontal gene transfer supported the evolution of an early metazoan biomineralization strategy

Background: The synchronous and widespread adoption of the ability to biomineralize was a defining event for metazoan evolution during the late Precambrian/early Cambrian 545 million years ago. However our understanding on the molecular level of how animals first evolved this capacity is poor. Because sponges are the earliest branching phylum of biomineralizing metazoans, we have been studying how biocalcification occurs in the coralline demosponge Astrosclera willeyana. Results: We have isolated and characterized a novel protein directly from the calcified spherulites of A. willeyana. Using three independent lines of evidence (genomic architecture of the gene in A. willeyana, spatial expression of the gene product in A. willeyana and genomic architecture of the gene in the related demosponge Amphimedon queenslandica), we show that the gene that encodes this protein was horizontally acquired from a bacterium, and is now highly and exclusively expressed in spherulite forming cells. Conclusions: Our findings highlight the ancient and close association that exists between sponges and bacteria, and provide support for the notion that horizontal gene transfer may have been an important mechanism that supported the evolution of this early metazoan biomineralisation strategy

A horizontal gene transfer supported the evolution of an early metazoan biomineralization strategy

Abstract Background The synchronous and widespread adoption of the ability to biomineralize was a defining event for metazoan evolution during the late Precambrian/early Cambrian 545 million years ago. However our understanding on the molecular level of how animals first evolved this capacity is poor. Because sponges are the earliest branching phylum of biomineralizing metazoans, we have been studying how biocalcification occurs in the coralline demosponge Astrosclera willeyana. Results We have isolated and characterized a novel protein directly from the calcified spherulites of A. willeyana. Using three independent lines of evidence (genomic architecture of the gene in A. willeyana, spatial expression of the gene product in A. willeyana and genomic architecture of the gene in the related demosponge Amphimedon queenslandica), we show that the gene that encodes this protein was horizontally acquired from a bacterium, and is now highly and exclusively expressed in spherulite forming cells. Conclusions Our findings highlight the ancient and close association that exists between sponges and bacteria, and provide support for the notion that horizontal gene transfer may have been an important mechanism that supported the evolution of this early metazoan biomineralisation strategy.</p

Deep genetic divergences among Indo-Pacific populations of the coral reef sponge (Leucettidae): Founder effects, vicariance, or both?-1

An individual producing asexual buds separating from the main animal. The size of both specimens is approximately 4 cm.<p><b>Copyright information:</b></p><p>Taken from "Deep genetic divergences among Indo-Pacific populations of the coral reef sponge (Leucettidae): Founder effects, vicariance, or both?"</p><p>http://www.biomedcentral.com/1471-2148/8/24</p><p>BMC Evolutionary Biology 2008;8():24-24.</p><p>Published online 26 Jan 2008</p><p>PMCID:PMC2267160.</p><p></p

Deep genetic divergences among Indo-Pacific populations of the coral reef sponge (Leucettidae): Founder effects, vicariance, or both?-0

An individual producing asexual buds separating from the main animal. The size of both specimens is approximately 4 cm.<p><b>Copyright information:</b></p><p>Taken from "Deep genetic divergences among Indo-Pacific populations of the coral reef sponge (Leucettidae): Founder effects, vicariance, or both?"</p><p>http://www.biomedcentral.com/1471-2148/8/24</p><p>BMC Evolutionary Biology 2008;8():24-24.</p><p>Published online 26 Jan 2008</p><p>PMCID:PMC2267160.</p><p></p

Sponge Paleogenomics Reveals an Ancient Role for Carbonic Anhydrase in Skeletogenesis

Sponges (phylum Porifera) were prolific reef-building organisms during the Paleozoic and Mesozoic similar to 542 to 65 million years ago. These ancient animals inherited components of the first multicellular skeletogenic toolkit from the last common ancestor of the Metazoa. Using a paleogenomics approach, including gene- and protein-expression techniques and phylogenetic reconstruction, we show that a molecular component of this toolkit was the precursor to the alpha-carbonic anhydrases (alpha-CAs), a gene family used by extant animals in a variety of fundamental physiological processes. We used the coralline demosponge Astrosclera willeyana, a "living fossil" that has survived from the Mesozoic, to provide insight into the evolution of the ability to biocalcify, and show that the alpha-CA family expanded from a single ancestral gene through several independent gene- duplication events in sponges and eumetazoans