A simulation model for an Iridaea splendens (Gigartinales, Rhodophyta) population in Vancouver, Canada

Abstract

Populations of Iridaea splendens at Brockton Point, Stanley Park, Vancouver, Canada were observed to alternate in dominance between the gametophytic phase in summer and tetrasporophytic phase in winter . The mechanism regulating this alternation is not clear . Using a matrix projection model to simulate population growth, we show that this alternation is possible if there are differential survival and recruitment rates of the two phases in summer and winter . Sensitivity and elasticity analyses indicate the relative importance of perennation vs . recruitment . Recruitment from tetrasporophytes and from gametophytes both contribute about 25 % to the population growth . Perennation among gametophytes is more important than among tetrasporophytes . The implication of this is that if this population is to be harvested, more tetrasporophytes can be harvested than gametophytes without resulting in the depletion of the resource . This is simulated in the matrix model by comparing the relative effects on population growth of increasing the mortality rate of the perennation phase of tetrasporophyte and gametophyte by 50 to 75 %, and increasing recruitment rate in either phase, from summer to winter or from winter to summer .

Population studies on a South African carrageenophyte: Iridaea capensis (Gigartinaceae, Rhodophyta)

“…This is evidence that the crust of this species is not in fact perennial, as dominance can change rapidly in a single population. This is in line with the model of Ang et al (1990) who estimated that the contribution of annual perennation to population growth was low in The epilithic crustose phase of Iridaea is often confusingly referred to in the literature as the 'perennial holdfast' (see e.g. Hannach & Waaland, 1986).…”

“…More recently, species of Iridaea have been used to study patterns and mechanisms of gametophyte/sporophyte alternation, especially using the resorcinol test to separate life history phases (e.g. Dyck et al, 1985;De Wreede & Green, 1990;Ang et al, 1990). Two species of Iridaea are currently recognised in southern Africa, both being endemic to the cool southwestern Africa marine province (sensu Liining, 1990).…”

Population dynamics and stage structure in a haploid‐diploid red seaweed, Gracilaria gracilis

“…Bierzychudek 1982; Meagher 1982; Valverde & Silvertown 1998; trees and palms, Alvarez‐Buylla et al . 1996; brown seaweeds, Ang & De Wreede 1990; Åberg 1992; and a red seaweed, Ang et al . 1990).…”

“…While matrix models have been developed for different life cycles found in marine algae (Ang & De Wreede 1990), they have been applied to only a handful of species (e.g. Ang & De Wreede 1990, 1993; Ang et al . 1990; Åberg 1992; Chapman 1993; Santos 1993; Santos & Nyman 1998).…”

STRUCTURE AND DYNAMICS OF A POPULATION OF PALMARIA PALMATA (RHODOPHYTA) IN NORTHERN SPAIN1

“…Furthermore, some species exhibit diplobiontic life cycles with isomorphic haploid and diploid free‐living individuals, which are difficult to distinguish in the field. As a result, the development of demographic models that integrate both population structure and dynamics and accommodate complex life cycles have been applied to a few macroalgal species (Ang et al 1990, Åberg 1992, Ang and De Wreede 1993, Chapman 1993, Santos 1993, Santos and Nyman 1998, Lindgren 2000, Engel et al 2001).…”