Temporal Variation in Size-Class and Tempo-Spatial Variation in Proportion of Reproductive Fronds of Amphiroa vanbosseae (Corallinales, Rhodophyta) in the Southwestern Gulf of California, Mexico

Abstract

Temporal variation in size class along with temporal and spatial variations in reproductive fronds of Amphiroa vanbosseae Lemoine were studied in a shallow population in the southwestern Gulf of California. Thalli were collected monthly from a dense population (3- thalli m super(-2) at 2-3 m depth) at El Sargento, BCS, Mexico. Two size-class groups were dominant (50-59 and 60-69 mm) over eight months suggesting very little variation in plant height was present among months. However, when the data were grouped seasonally, the size-class structure showed a trend of bigger plants in spring, suggesting recruitment and mortality were similar over the year with small windows of variation. Temporally, the plants were reproductive all year with a higher proportion of reproductive plants in summer. Spatially, only mature conceptacles were observed in the apical and middle area of the thalli, while in the basal area the plant never became reproductive. However, our observations showed that this population was dominated by bi-tetrasporophyte. Amphiroa vanbosseae appears to grow and reproduce all year, but with a maximum in reproduction during summer when other seaweed species disappear due to environmental stress