Magnitude, patterns and drivers of marine diversity
Extensive research provided insights into the magnitude and patterns of diversity for large conspicuous species such as corals and fishes. However, they represent a tiny subset of what really lives in the ocean (<1%). Small taxa have been ignored because (1) they are difficult to identify i.e., they belong to poorly studied groups and in some cases there are no well-defined morphological characters to delineate species (e.g., nematodes); (2) they are difficult to collect and census, i.e., the majority of marine diversity lives out of sight in cracks and crevices of the substrate. The plummeting cost of high throughput DNA sequencing and the technical improvements made in the past few years have transformed our ability to look at the magnitude, patterns and drivers of diversity across all taxa.
My colleagues, students and I have combined DNA-based sequencing approaches with standardized and spatially explicit sampling methods to infer the spatial distribution of overlooked taxonomic groups in the ocean. We have been working in structurally complex and threatened habitats where collecting comparable samples through time and space is difficult. On coral reefs for example, most species lives in the matrix below the surface. To avoid destructive sampling and to control for habitat space, we have used Autonomous Reef Monitoring Systems (ARMS, see photo). ARMS are like small apartment buildings for marine animals. They are fixed to the substrate for a year or two during which they are colonized by a diversity of small invertebrates and fishes. Using this approach we have shown that more than 2/3 of marine diversity is smaller than 2mm and we confirmed that small species are much more widely distributed than small taxa.
Ongoing projects aim at testing theories of community assembly and quantifying how biodiversity scales with habitat diversity, geographic area and body size. We are asking questions such as: Are life history traits good predictors of patterns of species diversity? Are there common drivers of diversity across shallow marine habitats? Can we estimate how many species live in the Ocean? Are there good indicator taxonomic groups of environmental changes? How useful is environmental DNA in seawater to ask the questions listed above?
Processing of whole invertebrate communities in tropical Bocas del Toro. Top: the field team brings the samples to the boat (photo credit: Sean Mattson); Bottom left: Natasha Hinojosa, Owen McMillan and Lyle McMillan are morphosorting specimens (photo credit: Matthieu Leray); Bottom right: Gustav Paulay, curator of invertebrates at the Florida Museum of Natural History, is identifying microscopic mollusks.
Specimens are sorted based on morphological characters, identified to the lowest taxonomic level, photographed and preserved for DNA analysis and further taxonomic work. Top left: unsorted specimens (photo credit: Matthieu Leray); Top right: one specimen per morphospecies is assigned a unique field identifier (photo credit: Matthieu Leray); Bottom left: carcinologist Robert Lasley is taking high resolution photographs of live specimens to document color patterns (photo credit: Matthieu Leray); Bottom right: Francois Michonneau, echinoderm specialist, is placing specimens in vials for archiving of specimens and tissues.
Field guide for >500 invertebrate species associated with coral reefs of Bocas del Toro. PDF available for download here
SELECTED PUBLICATIONS ON THIS TOPIC
Kandler NM, Wooster MK, Leray M, Knowlton N, de Voogd NJ, Paulay G, Berumen ML. 2019. Hyperdiverse macrofauna communities associated with a common sponge, Stylissa carteri, shift across ecological gradients in the Central Red Sea. Diversity11, 18
Pearman JK, Leray M, Villalobos R, Machida R, Berumen M, Knowlton N, Carvalho S. 2018. Cross-shelf investigation of coral reef cryptic benthic organisms reveals diversity patterns of the hidden majority. Scientific Reports8, 8090
Pachelle PPG, Leray M, Anker AA, Lasley R. 2018. Five new records of marine shrimps (Decapoda: Caridea, Stenopodidea) from the Caribbean coast of Panama. Zootaxa. 4438,128-136
Leray M, Knowlton N. 2016. Censusing marine eukaryotic diversity in the twenty-first century. Philosophical Transactions of the Royal Society B371,20150331
Al-Rshaidat MMD, Snider A, Rosebraugh S, Devine AM, Devine TD, Plaisance L, Knowlton N, Leray M. 2016. Deep COI sequencing of standardized benthic samples unveils overlooked diversity of Jordanian coral reefs in the northern Red Sea. Genome59,724-737
Leray M, Knowlton N. 2015. DNA barcoding and metabarcoding of standardized samples reveal patterns of marine benthic diversity. Proceedings of the National Academy of Sciences of the United States of America. 112,2076-2081