Heteromorphic phases of Leathesia marina (Ectocarpales, Ochrophyta) over time from northern Patagonia, Argentina

Abstract

The emergence and evolution of the heteromorphic life history in algae has been considered as a response to the selective pressures of changing environments. The brown alga Leathesia marina has a typical heteromorphic life history, alternating between microscopic branched filaments (gametophytic phase) and a macroscopic erect stage (sporophytic phase). The first aim of this study was to describe vegetative and reproductive morphologies of sporophytes (macrothalli and diploid phase) of L. marina and their relationship with environmental factors in an annual cycle. The second aim was to report the discovery of gametophytes (microthalli and haploid phase) in the natural environment on northern Patagonian coasts, and to describe their morphology, abundance and reproductive output. The macroscopic phase was observed over 8 months, from September to April during the warm season. The microscopic phase was observed in two periods, March–April and September–October. A temporal overlap was observed between the microscopic and macroscopic phases. The population of macrothalli had a type III survivorship curve. The cover, density and size of macrothalli were associated with warmer months, but the abundance of microthalli and reproductive output of both phases were higher in temperate periods. Demographic parameters, including mortality rate, survivorship, reproductive output and the morphological characteristics of L. marina are used to evaluate the adaptation of this species to a changing environment, typical of the temperate coasts of northern Patagonia in Argentina.