Molecular Phylogeography and Species Discrimination of Freshwater Cladophora(Cladophorales, Chlorophyta) in North America

Biology;Cladophora;Inter-simple sequence repeats;Internal transcribed spacer region;morphometric analysis

Ross, Sara J.

University of Waterloo

关键词: Biology;    Cladophora;    Inter-simple sequence repeats;    Internal transcribed spacer region;    morphometric analysis;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/2977/1/s2ross2006.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Cladophora is a widespread freshwater filamentous cholorophyte genus and is frequentlyobserved in eutrophic waters where it can produce large nuisance blooms. These bloomscan have direct impacts on water intake for power generation, irrigation canals and can beaesthetically unpleasant. Much of the ecological and physiological studies on Cladophorahave assumed that the populations of this genus in North America belong to the speciesCladophora glomerata. However, this has never been tested despite that it is well documentedthat identifying freshwater Cladophora to the species level is difficult duemorphological variability under different ecological conditions. In addition, the speciesepithets for freshwater Cladophora are based on European collections and it is not clear ifthese should be applied to North America. This study examines approximately 40collections of Cladophora from the Laurentian Great Lakes and 43 from various locationsin North America ranging from the Northwest Territories to Puerto Rico. Initially we determined the nucleotide sequences of the internal transcribed spacer (ITS) region of thenuclear ribosomal cistron and observed sequence divergence to be low (0-3%),demonstrating an inability for this marker to resolve species delineation as divergence ofthis region was low. Amplification of the inter-simple sequence repeat (ISSR) regionswere used to analyze microsatellite motif frequency throughout the genome to evaluate thebiogeography relationships, including diversity, of freshwater Cladophora sp. five differentprimers were used on 70 individuals. UPGMA analyses of the presence/absence of bandsdemonstrate that each of the Great Lake populations separate into groups according to theLake they were initially sampled from. However, collections from North America arehighly variable and do not form well supported biogeographic clades. In addition, these collections appear to be distinct from type cultures of freshwater Cladophora from Europe.Supplementary morphological analysis using suggested taxonomically valid criterion(length and diameter of main axis, ultimate branch, and apical cell) none were able todifferentiate Great Lake populations.