A parallel assessment of morphological and genetic diversity in the kelp Alaria marginata

This study addressed the questions of morphological and genetic variability as a function of biogeographic situation, distance and time on the intertidal seaweed, Alaria marginata Postels et Ruprecht. Specifically, I have attempted to provide a preliminary understanding of the influence of biogeographic scale (cm to 100 plus km), coastal habitats (open vs. inland waters), and seasons on morphological and genetic variability.; Patches of macrophytes were collected at three different seasons from two environmentally contrasting stands, Execution Rock (wave exposed) and Kelp Bay (wave sheltered) (Vancouver Island, British Columbia, Canada). A third stand, Rosario Beach (Whidbey Island, Washington State, USA), was selected to represent an outlying stand.; Based on five characters morphological variation was determined statistically using Bonferroni adjustment test, stepwise discriminant, factor, and cluster analyses.; Morphological variation was observed in patches within and between stands as well as between seasons. Different morphological characters expressed between-stand differences at different times. Macrophytes at the seasonally more homogeneous environment, Execution Rock had limited seasonal variations relative to those at the seasonally more heterogeneous environment, Kelp Bay.; Morphological differences between stands were greater in the winter when environmental differences between stands were least and these morphological differences were less in summer when environmental differences between stands were greatest.; Genetic structuring of Alaria marginata over time and space was investigated using the fingerprinting technique Amplified Fragment Length Polymorphisms (AFLP). The genetic similarity among Alaria individuals increased with decreasing geographic scale considered. A comparison of a wave exposed and a wave sheltered stand demonstrated a greater genetic similarity of patches making up the wave sheltered stand. Greater wave action could break down this genetic structuring in the more wave exposed stand. Between-stand genetic similarities indicated a possible net gene flow between Alaria stands, consistent with local current patterns. Seasonal genetic similarities were altered significantly at one stand. To my knowledge this study is the first application of AFLP to a comprehensive marine population study and the first seaweed study relating genetic structuring to seasonal and environmental differences.; Environmental parameters, including water motion, nutrient availability, and temperature, could explain most of the morphological and genetical structural variation patterns observed in this study.