No abstract

In 2004, Mytella charruana (d'Orbigny, 1842) (Mollusca: Bivalvia: Mytilidae) became established along the coast of the southeastern United States (SE-US). Using mitochondrial DNA sequencing (cytochrome c oxidase subunit I), we compared genetic variation throughout its native range in South America to its invasive range in the SE-US. Samples from the SE-US were collected in 2006 and 2010 enabling a temporal comparison to evaluate possible genetic changes of the invasive population. We addressed two questions. First, what are the potential source populations (or geographic regions) for the SE-US invasion? Second, how has genetic diversity changed between the two sampling periods within the SE-US? We identified a total of 72 haplotypes, 64 of which were isolated to geographic sites and only 8 were shared among sites. The highly structured native range provides insight into the origin of invasive populations where our results suggest that the introduced SE-US population originated from multiple source populations with the Panama region as the primary source. Additionally, our results indicate that genetic composition of the non-native populations was unchanged between the two sampling periods. Mytella charruana exhibit a significant pattern of genetic structure among natural populations, owing to biogeographic barriers that limit natural dispersal, and an ability to persist in novel habitats, owing to a suite of life-history characters that favor survival under variable conditions. Overall, this study explains why M. charruana may become an increasing threat to locations founded by anthropogenic transportation.

No abstract

The scleractinian corals of the genus Tubastraea Lesson, 1830 are currently globally dispersed and even so still present a confused taxonomy due to the overlap of morphological characters between the species. In this study, we investigate Tubastraea species previously found in the western Atlantic, based on the molecular marker (ITS gene) and morphology, to determine the accuracy of their descriptions. We identified three morphotypes from Brazil which were genetically delimited into two species: Tubastraea coccinea (Morphotypes I and II) and Tubastraea sp. (Morphotype III). Although morphotype I has morphological patterns of Tubastraea aurea (Quoy & Gaimard, 1833) there was no molecular divergence to support the species differentiation and continue to be recognized as a morphological variant of T. coccinea. The third morphotype is both morphologically and genetically distinct from T. coccinea and is also not representative of the species Tubastraea tagusensis Wells, 1982 despite earlier descriptions describing T. tagusensis in Brazil. Morphotype III exhibited distinct morphological characteristics among the other morphotypes, mainly due to greater polyp projection. In addition, it has fusions between septa, a characteristic that differentiates it from T. tagusensis. Nevertheless, molecular phylogenetic analyses showed that Brazilian Tubastraea fell into two well-supported monophyletic clades, and samples collected in the United States overlapped in both clades. Florida samples exhibited fewer morphotypes and showed greater genetic diversity, presenting haplotypes in four other internal clades. This study highlights the need for an integrative approach to conduct a deeper species delimitation of Tubastraea, essential for managing bioinvasion events by sun corals.