Simulation and analysis of the dynamics of a Fucus distichus (Phaeophyceae, Fucales) population

Abstract

A general 9 X 9 matrix model based on recruit stages and plant size is proposed for a population of the brown alga Fucus distichus L. emend. Powell in False Creek, Vancouver, Canada. Twenty-six matrices were constructed each representing a monthly time interval covering the period from July 1985 to November 1987. Yearly matrices were also constructed as a product of monthly matrices covering periods of 1 yr. The characteristics of these matrices were evaluated by comparing the dominant eigenvalue (i.e. the population growth rate, A), the stable distribution, and reproductive values for each matrix. The relative contribution of each matrix parameter to population growth was assessed using elasticity analysis. The survival and transition of the plants among size classes contribute at least 50 % to the population growth rate. However, because E distichus plants do not exhibit vegetative regeneration, the population can only experience positive growth in the presence of recruitment. Absence of a germling bank has little effect on monthly projected population growth, but can reduce the population growth rate projected from the yearly matrix by as much as 83%. Current population size structure is very different from the projected stable distribution. The stable distribution generally has a large proportion of the plants in the recruit stage. Reproductive values are positively related to plant size but are comparable among the largest 4 size classes. Random combinations of monthly, seasonal, or yearly matrices were used to simulate population growth under various fluctuating environmental conditions. A negative growth rate was obtained in > 6 0 % of the simulation runs. In reality within the sampling period covered, the population is on the decline. It is likely that this population may recover by occasional pulses of a large number of recruits, as was observed in 1986.

Trade‐offs between life‐history traits at range‐edge and central locations

“…), but recruitment is still fundamental for the long‐term stability of populations (Reed et al. , Ang and De Wreede ). Empirical evidence suggests that differences in reproductive allocation among populations of the same species might be the result of selection for plastic phenotypes in habitats with environmental fluctuations (Torang et al.…”

Long-Term Signal of Disturbance: Fucus gardneri after the Exxon Valdez Oil Spill

“…For instance, Ang and DeWreede (1993) showed that, despite the seasonal appearance of macrorecruits (Ͻ1 cm), small individuals (Ͻ5 cm) represented most of the population throughout the year, which contrasts with the high proportion of 5-8 cm individuals observed in PWS in July 1996. However, disturbed sites did not show consistent distinctions based on all ways of calculating ln(AD) and MD metrics (Table 3).…”

Field testing of inter- and intraspecific coalescence among mid-intertidal red algae

“…At those early stages of population development, coalescence seems to replace intraspecific competition, the latter of which is an important mortality factor in the establishment of non-coalescing seaweed populations (e.g. Chapman & Goudey 1983, Santelices & Ojeda 1984, Dean et al 1989, Reed 1990, Ang & DeWreede 1993, Flores-Moya et al 1997, Creed et al 1998, Scrosati 2000. To gain a better understanding of the relative importance of coalescence as a community process, as well as to develop new demographic models for coalescing seaweeds (Santelices 2001), future experimental studies should explore the relationships among coalescence, intraspecific competition and recruitment at different population densities.…”