Gametophyte life-history dominance of Chondrus crispus (Gigartinaceae, Rhodophyta) along the Atlantic coast of Nova Scotia, Canada

doi:2011.26.1.51

Algae > Volume 26(1); 2011 > Article

Algae 2011;26(1): 51-60. doi: https://doi.org/10.4490/algae.2011.26.1.051

Jack L. McLachlan¹,a, Wade Blanchard², Christopher Field², Nancy I. Lewis¹^,*

¹National Research Council Canada, 1411 Oxford St., Halifax, NS B3H 3Z1, Canada
²Department of Statistics, Dalhousie University, Halifax, NS B3H 4J1, Canada adeceased December 2010

*Corresponding Author

Email: Nancy.Lewis@nrc-cnrc.gc.ca

ABSTRACT

Similar to other species of Gigartinaceae Chondrus crispus has an alternation of perennial, isomorphic gametophytic and sporophytic generations. As these two generations co-exist independently within populations and obtain their resources in a similar manner, intraspecific competition is expected. In populations within the southern Gulf of St. Lawrence, fronds of both generations of C. crispus occur in similar numbers. This equivalency can be related to substratum instability, where the population is dynamic with a high turn-over rate of genets. These observations support a stochastic hypothesis to account for distribution of gametophytes and sporophytes in this area. Along the Atlantic coast of Nova Scotia, where the substratum is stable, gametophytes are overwhelmingly predominant. Gametophytic redominance is greatest in the lower littoral zone where C. crispus is abundant and space is limited. Under the fucoid canopy where “free-space” exists, the gametophyte to sporophyte ratio is lower. Gametophytic and sporophytic fronds are distributed equally among different size-classes and size-distribution is not considered a competitive factor. Previous studies have shown that sporophytic fronds of C. crispus are more susceptible to infections by endophytic algae and other pathogens, and are more heavily grazed by herbivores than are gametophytic fronds. Thus, mechanistic factors are strongly implied in the selection of gametophytes in the Atlantic population.

Key words: carrageenan; Chondrus; gametophyte; Geni coefficient; life-history ratio; population structure; size hierarchy; sporophyte