Analysis of Freshwater and Marine Ulva flexuosa in Southern California

In 2011 Mars et. al. proposed a novel approach to identifying three different subspecies within European waters of Ulva flexuosa, (subsp. pilifera, paradoxa, and flexuosa). Their use of morphological and molecular techniques to separate each subspecies was used as a guide for this study to determine if these techniques would work for U. flexuosa within California waters. Eleven freshwater, five brackish water, and two saltwater samples of Ulva were collected and were assessed using classic morphological methods and molecular techniques. The molecular methods examined the DNA region ITS1-5.8S-ITS2 (ITS) and the chloroplast RUBISCO LSU (rbcL) genes. The morphological methods followed Mares et al. guide to differentiate between subspecies. All the samples collected, except one, were determined, morphologically to be the within the species criteria for Ulva flexuosa, however, this guide was not able to separate any specimen down to the subspecies level. The molecular analysis suggested that all of the freshwater samples were indeed U. flexuosa and only half of those could be aligned with the subspecies paradoxa. The other freshwater samples did not align themselves with any subspecies and none were aligned with the subspecies pilifera. The samples that were collected in the brackish or saltwater were not shown to be U. flexuosa by molecular analysis but instead two different species either Ulva torta or Ulva linza. The finding of this study suggest that Mares et al. (2011) is not an acceptableguide to assess the identity of U. flexuosa down to the subspecies level with in Southern California, especially in water with higher salinity. The morphological plasticity within the genus Ulva demonstrates the need for more molecular techniques in the identification of U. flexuosa and its subspecies.