Thermal ecotypes of amphi-Atlantic algae. II. Cold-temperate species (Furcellaria lumbricalis andPolyides rotundus)

Abstract

Two species of cold-temperate algae from the North Atlantic Ocean, Polyides rotundus and Furceflaria lumbricalis, were tested for growth and survival over a temperature range of -5 to 30 ~ In comparisons of eastern and western isolates, both F. lumbricalis, a North Atlantic endemic, and P. rotundus, a species having related populations in the North Pacific, were quite homogeneous. F. lumbricalis tolerated -5 to 25 ~ and grew well from 0 to 25 ~ with optimal growth at 10-15 ~ P. rotundus tolerated -5 to 27 ~ grew well from 5 to 25 ~ and had a broad optimal range of 10-25 ~ Both species tolerated 3 months in darkness at 0 ~ In neither case could any geographic boundary be explained in terms of lethal seasonal temperatures, suggesting that these species are restricted in distribution by strict thermal and/or daylength requirements for reproduction. The hypothesis that northern species are more homogeneous than southern taxa in terms of thermal tolerance was supported. A second hypothesis, that disjunct cold-temperate species should be more variable than pan-Arctic species, was not supported.

Temperature responses of tropical to warm-temperate Atlantic seaweeds. I. Absence of ecotypic differentiation in amphi-Atlantic tropical-Canary Islands species

“…However, most seaweed species do not have continuous distribution ranges as continents, large bodies of (oceanic) water or adverse seawater temperatures may act as barriers between populations. If these disjunct populations experience different temperature regimes, selective forces may result in (local) ecotypic differentiation of temperature responses (Odum, 1975;Bolton, 1983;Novaczek & Breeman, 1990). Seaweeds with a tropical to subtropical distribution in the Atlantic Ocean show such a geographical disjunction between eastern (tropical West Africa; Cape Verde Islands; Canary Islands) and western (Caribbean; tropical parts of Brazil) populations.…”

THE INVASIVE GENUS ASPARAGOPSIS (BONNEMAISONIACEAE, RHODOPHYTA): MOLECULAR SYSTEMATICS, MORPHOLOGY, AND ECOPHYSIOLOGY OF FALKENBERGIA ISOLATES1

“…The slightly different temperature responses for growth, survival, and tetrasporogenesis of different Pacific isolates may represent temperature ecotypes. Ecotypic differentiation in temperature responses of seaweeds is relatively rare (Breeman 1988), with most reports occurring in seaweed populations that have disjunct distributions, wide latitudinal ranges (Novaczek and Breeman 1990, Novaczek et al 1990), or both. Temperature ecotypes in species with tropical Atlantic/Mediterranean distributions have been linked to their survival in refugia during the last glacial maximum (Pakker and Breeman 1996).…”

A COMPARATIVE STUDY OF TEMPERATURE RESPONSES OF CARIBBEAN SEAWEEDS FROM DIFFERENT BIOGEOGRAPHIC GROUPS1

“…The majority of studies have focused on seaweeds from temperate (e.g. van de Hoek 1982a, b, Cambridge et al 1990, Novaczek and Breeman 1990 and polar (e.g. tom Dieck 1989, 1990) regions, but little attention has been paid to species from the tropics.…”