The orange roughy Hoplostethus atlanticus is a well-known commercial species with a global distribution.There is no consensus about levels of connectivity among populations despite a range of techniques having been applied. We used cytochrome c oxidase subunit I (COI) and cytochrome b sequences to study genetic connectivity at a global scale. Pairwise U ST analyses revealed a lack of significant differentiation among samples from New Zealand, Australia, Namibia, and Chile. However, low but significant differentiation (U ST = 0.02-0.13, P \ 0.05) was found between two Northeast Atlantic sites and all the other sites with COI. AMOVA and the haplotype genealogy confirmed these results. The prevalent lack of genetic differentiation is probably due to active adult dispersal under the stepping-stone model. Demographic analyses suggested the occurrence of two expansion events during the Pleistocene period.

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The marine brooder Excirolana braziliensis (Crustacea: Isopoda) is also a complex of cryptic species on the coast of Chile ABSTRACTSpeciation is a direct consequence of isolated populations in taxa with low dispersal potential. The brooding crustacean Excirolana braziliensis, with a presumably wide geographic range of distribution (~16º N-41º S in the Pacifi c and ~19º N-35º S in the Atlantic), has been detected to correspond to cryptic species on the coast of Panama. Latitudinal variations in reproductive features in E. braziliensis have been attributed to phenotypic plasticity, however, the differences may be the result of divergent populations. Considering that the taxon has been reported to be a complex of cryptic species in other geographic areas and given the phenotypic differences detected along its distribution range, we hypothesized that E. braziliensis is a complex of species in the coast of Chile. We used partial cytochrome c oxidase subunit I (COI) sequences from 132 individuals with the diagnostic morphology of E. braziliensis collected along ~2200 km of coast to determine the genetic structure of E. braziliensis. Phylogenetic and phylogeographic analyses showed three distinct clades with 14 to 19 % of genetic divergence and high values of genetic differentiation. Intra and inter-clade divergence revealed the existence of a species complex of E. braziliensis on the coast of Chile, supporting growing evidence of the high abundance of cryptic species in marine invertebrate taxa.Key words: cryptic species, genetic differentiation, genetic distance, marine peracarids, phylogenetics. RESUMENLa especiación es una consecuencia directa de poblaciones aisladas en taxa con bajo potencial de dispersión. El crustáceo incubador Excirolana braziliensis tiene un rango de distribución presumiblemente amplio (~16º N-41º S en el Pacífi co y ~19º N-35º S en el Atlántico). Se ha detectado que este taxón representa un complejo de especies crípticas en la costa de Panamá. Variaciones latitudinales en características reproductivas en E. braziliensis han sido atribuidas a plasticidad fenotípica, sin embargo, las diferencias podrían deberse a la existencia de poblaciones divergentes. Considerando que se ha reportado que este taxón es un complejo de especies crípticas en otras áreas geográfi cas y dadas las diferencias fenotípicas detectadas a lo largo de su rango de distribución, hipotetizamos que E. braziliensis es un complejo de especies en la costa de Chile. Utilizamos secuencias parciales del gen citocromo c oxidasa subunidad I (COI) de 132 individuos con la morfología diagnóstica de E. braziliensis recolectados a lo largo de ~2200 km de costa para determinar la estructura genética de E. braziliensis. Análisis fi logenéticos y fi logeográfi cos revelaron tres clados que presentaron una divergencia genética entre 14-19 % y valores de diferenciación altos. La divergencia intra e interclados indican que existe un complejo de especies de E. braziliensis en la costa de Chile, lo que se suma a la creciente evidencia de la al...

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Brooding marine isopods of the genus Limnoria inhabit and feed on kelp holdfasts and wood. These substrata have high floating potential, making these species ideal organisms to study the effects of rafting-mediated connectivity on the population structure of brooders living on rafting substrata. It is hypothesized that rafting leaves particular genetic signatures such as low differentiation among distant local populations and absence of isolation by distance (IBD) at a macro-geographic scale (thousands of km). Using cytochrome oxidase I (COI) sequences, we tested the effects of rafting-mediated gene flow with respect to genetic differentiation on L. quadripunctata (from wood and also the holdfasts of the giant kelp Macrocystis pyrifera) and L. chilensis (mainly from the bull kelp Durvillaea antarctica) sampled across 2400 km of the Chilean coast. Analyses of COI data for both species indicated low differentiation between distant locations along the Chilean coast and lack of IBD, bearing the expected genetic signatures of rafting dispersal. Phylogenetic analyses were performed with COI and the nuclear gene 28S to place the genetic diversity of Chilean Limnoria spp. into a wider geographical context. Both markers revealed that L. quadripunctata from Chile is a sister clade to other Limnoria spp. analyzed (L. chilensis, L. segnis, and L. stephenseni), which mainly inhabit D. antarctica. L. chilensis from Chile and subantarctic islands form a tight monophyletic group. Phylogenetic and phylogeographic analyses show that along the studied area, L. quadripunctata and L. chilensis have the genetic signatures of relatively recent or ongoing rafting.KEY WORDS: Peracarids · Rafting · Biogeography · Mitochondrial DNA · COI · 28S · Phylogeny · Phylogeography 455: 111-122, 2012 onize new geographic areas or maintain population connectivity with distant areas (e.g. Waters & Roy 2004, Donald et al. 2005, Fraser et al. 2009, Nikula et al. 2010. Such individuals may form colonizing or founder groups over a wide range of distances, including isolated localities (Johannesson 1988, Cunningham & Collins 1998. Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerBased on the rafting hypothesis, Johannesson (1988) proposed that colonization success would be higher for taxa that brood offspring than for planktonic developers, as she had observed in Rockall with Littorina species. Organisms that live and feed on their raft may persist throughout the voyage, including brooding females, whose juveniles recruit nearby and experience extended parental care. These features increase the probability of long-distance dispersal and successful colonization (Davenport & Stevenson 1998, Thiel & Haye 2006.Species with a low potential for autonomous dispersal (such as brooders and organisms with very short planktonic larval stages) may have a spatial distribution of the genetic diversity conforming to an isolation by distance (IBD) pattern. This pattern is expected when the dispersal potentia...