Iberian intertidal turf assemblages dominated by Erythroglossum lusitanicum (Ceramiales, Rhodophyta): structure, temporal dynamics, and phenology

Abstract

Erythroglossum lusitanicum is a foliose, turf-forming member of the Delesseriaceae that colonizes sand-covered intertidal rocks on the Atlantic Iberian Peninsula. We examined (i) the phenology of this alga and (ii) the structure and temporal dynamics of its associated fl ora at two sites over one year. Species diversity was low in the assemblage, which was dominated by E. lusitanicum. Assemblage structure was essentially constant through the year. There were, however, significant differences in E. lusitanicum characteristics between the two sites. At one, E. lusitanicum was more abundant, thalli were longer and wider, and the proportion of plants with tetrasporangia was higher than at the second location. At the first site, the phenological traits tracked a temporal cycle. Thallus length and blade width were highest in April; after gradual deterioration of the apical portions of the plants, individual sizes reached minimum values in July. Subsequently, individual growth rate was low and plant length was nearly constant from September to February. Tetrasporangia were common throughout most of the year; only in July they were totally absent. Temperature and daylength were inversely related to reproduction. Sexual reproductive structures were not observed. The abundant growth of basal proliferations suggests that vegetative propagation very probably plays an important role in the maintenance of E. lusitanicum populations.