Morphological variations of Gracilaria chilensis Bird, McLachlan et Oliveira, 1986 (Rhodophyta, Gracilariales) in the southeast Pacific

Abstract

The present work is a population morphometric study of Gracilaria from different environments along a latitudinal gradient of the Chilean coast that cover 1,500 km. Gracilaria species have been extensively exploited with an average extraction of 75,000 t per year. In Chile this seaweed is usually found in sandy bottom bays between Antofagasta (23º29'S -70º25'W) and Chiloé (42º03'0''S -73º11'0''W). Observations were made in 51 plants. Macroscopic observations were done in fresh plants, microscopic characters were determined in transversal sections with 20% Karo syrup and stained with aniline blue. Numerical analyses were performed by one-way ANOVA and Principal Component Analysis. The latter analysis was performed for those characters with significant differences among the localities: basal constriction of branches, branch frequency, cortex cell diameter, subcortex cell diameter, thickness of the cortex and medullar cell diameter. The results of the Principal Component Analysis showed that 61% of the variance corresponded to the two first components. There were not observed groups clearly defined. The data suggest that along the coast of Chile there is only one morphotype that corresponds to the description of Gacilaria chilensis Bird, McLachlan et Oliveira, 1986 and it fits to the bulk of the material utilized in commercial production.