Investigations on the subaerial green algal order Trentepohliales (ulvophyceae; chlorophyta) in the Southeastern USA

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Trentepohliales is an understudied order of subaerial green algae ( Chlorophyta, Ulvophyceae) found throughout the Southeastern USA and in many regions with high humidity and warm temperatures. Monthly collections of a common trentepohlialean taxon, Trentepohlia arborum, were made at three sites within Tuscaloosa County, Alabama, USA and observed for seasonality, variation in morphological features, and reproductive structures. The economically important trentepohlialean taxon, Cephaleuros virescens, has been reported in the literature from almost every tropical and subtropical region. In this study a systematic and phylogenetic assessment was performed on strains of C. virescens samples gathered from the Southeastern USA and overseas. The use of primers specifically designed during this study for the chloroplastencoded large subunit rubisco, or rbcL, for C. virescens were successful in amplifying sequences for phylogenetic analyses. Results of this investigation indicate that several entities are currently grouped under the name "Cephaleuros virescens". These lineages share a similar morphology and habitat and possibly represent a case of morphological convergence and cryptic diversity. Based on topotype material from the Guianas, C. virescens appears to be restricted to tropical Central and South America, with several unnamed species of Cephaleuros occurring in Southeastern USA and overseas. The D 1- D2 region from the nuclear-encoded large subunit ribosomal DNA, or D 1-D2 LSU rDNA, was also assessed with several trentepohlialean taxa and compared with previous reports based on rbcL and the small subunit ribosomal DNA, or SSU rDNA. Results of this investigation suggest that the shorter D1-D2 LSU rDNA contains enough phylogenetic signal, similar to rbcL and SSU rDNA, to reconstruct the phylogeny of representatives in the family Trentepohliaceae; moreover, D 1-D2, because of its shorter length represents a cost-effective alternative; this study also supports the use of D 1-D2 as an excellent option for current efforts of the DNA Barcoding for Life project for green algae.

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