Population biology of the crustose red alga Lithophyllum incrustans Phil. Three populations on the east coast of Britain

Abstract

The distribution of the criistose red alga I.ithophvllum inriuJtanJ in the British Isles is described. Three populations are analysed demographically, two having age class distributions corresponding to a type 111 sur\ivorship curve characteristic of poptilations in which the greatest mortality occurs in the youngest age classes. The more southern of these two populations has a longer generation time (14.2 years) than the more northern (8.5 years). The third and most southern population has an age class distribution dominated by the 6-and 7-year-old categories. There were few sexual thalli (around 3 " , , ) but they appeared to put more effort into reproduction than the asexual thalli.

Patterns of fucoid reproductive biomass allocation

“…For example, total reproductive effort in the opportunistic green alga Ulva lactuca L. varies seasonally, being minimal in spring (20%) and maximal (60%) during late summer (Niesembaum, 1988). The perennial crustose red alga Lithophyllum incrustans Philippi exhibits a wide range of reproductive effort (10-55%, X = 14%), depending upon its age and reproductive composition (Edyvean & Ford, 1984a, b;Ford, Hardy & Edyvean, 1983). Chopin, Pringle & Semple (1988) compdred the reproductive capacity of Chondrus crispus Stackhouse (as mm 2 of sorus/0.25 m 2) from harvested and nonharvested populations in the Gulf of St. Lawrence, Canada.…”

“…Cousens (1986) emphasized analogous problems, plus the *Present address: Juneau Center for Fisheries and Ocean Science, University of Alaska Fairbanks, Juneau, Alaska, 99801 0007 1617/92/030271 +22 $08.00/0 difficulty of differentiating between current and previous years' growth (biomass) in many perennial seaweeds. To date relatively few quantitative reproductive assessments of green and red algae have been conducted, and most studies have emphasized fucoid algae and kelps that have discrete receptacles and sori, respectively (Chopin, Pringle & Semple, 1988;De Wreede & Klinger, 1988;Edyvean & Ford, 1984a, b;Fernfindez & Men6ndez, 1991;Ford, Hardy & Edyvean, 1983;Niesembaum, 1988;Santelices, 1990).…”

Spore production byLithophyllum incrustans(Corallinales, Rhodophyta) in the British Isles

“…Cystocarpic conceptacles, which form from female conceptacles, are similar in size to asexual conceptacles but lack the columella (Edyvean & Moss, 1984). Ford et al (1983) found that the conceptacles of asexual plants were laid down in distinct layers and related this to seasonality of reproduction. Ford et al (1983) and Edyvean & Ford (1984a,b) noted that the percentage of sexual plants in populations increases towards the south-* School of Biological Sciences, University of Bath, Bath BA2 7AY, U.K. west of the country and that asexual plants produced bispores and/or tetraspores.…”

“…In the south of England it extends littorally east to the Isle of Wight (Adey & Adey, 1973). On the east coast of Britain it is restricted to north of the river Tyne (Ford, Hardy & Edyvean, 1983).…”

“…Ford et al (1983) found that the conceptacles of asexual plants were laid down in distinct layers and related this to seasonality of reproduction. Ford et al (1983) and Edyvean & Ford (1984a,b) noted that the percentage of sexual plants in populations increases towards the south-* School of Biological Sciences, University of Bath, Bath BA2 7AY, U.K. west of the country and that asexual plants produced bispores and/or tetraspores. The present study was undertaken to determine the seasonality of reproduction and any seasonal or regional variation in the type of Spores produced.…”