Harilaos A Lessios

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The causes of speciation in the sea are rarely obvious, because geographical barriers are not conspicuous and dispersal abilities or marine organisms, particularly those of species with planktonic larvae, are hard to determine. The phylogenetic relations of species in cosmopolitan genera can provide information on the likely mode of their formation. We(More)
After a 12-million-year (My) process, the Central American Isthmus was completed 2.8 My ago. Its emergence affected current flow, salinity, temperature, and primary productivity of the Pacific and the Atlantic and launched marine organisms of the two oceans into independent evolutionary trajectories. Those that did not go extinct have diverged. As no(More)
A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for(More)
Comparative phylogeographic studies often reveal disparate levels of sequence divergence between lineages spanning a common geographic barrier, leading to the conclusion that isolation was nonsynchronous. However, only rarely do researchers account for the expected variance associated with ancestral coalescence and among-taxon variation in demographic(More)
Echinometra is a pantropical sea urchin made famous through studies of phylogeny, speciation, and genetic structure of the Indo-West Pacific (IWP) species. We sequenced 630 bp of the cytochrome oxidase I (COI) mitochondrial gene to provide comparable information on the eastern Pacific and Atlantic species, using divergence between those separated by closure(More)
The ecologically important sea urchin Diadema antillarum suffered mass mortalities in 1983, first noted in Panama and then reported from the rest of the Caribbean. We documented the effects of this mortality at two localities on the Atlantic coast of Panama, Punta Galeta and the San Blas Archipelago. At Punta Galeta, affected by the mortality in January(More)
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(More)
To understand how allopatric speciation proceeds, we need information on barriers to gene flow, their antiquity, and their efficacy. For marine organisms with planktonic larvae, much of this information can only be obtained through the determination of divergence between populations. We evaluated the importance of ocean barriers by studying the(More)
The high biodiversity of tropical marine hotspots has long intrigued evolutionary biologists and biogeographers. The genus Haemulon (grunts) is one of the most important (numerically, ecologically, and economically) reef fish groups in the New World and an excellent candidate to test hypotheses of speciation and diversity generation in the Greater(More)
The 'impassable' Eastern Pacific Barrier (EPB), ca 5000 km of deep water separating the eastern from the central Pacific, is the World's widest marine biogeographic barrier. Sequencing of mitochondrial DNA in 20 reef fish morphospecies encountered on both sides of the barrier revealed cryptic speciation in two. Among the other 18 species only two showed(More)