Distinguishing between genetic individuals in ascophyllum nodosum populations on the swedish west coast

Abstract

Distinguishing between genetic individuals of the brown alga Ascophyllum nodosum in the field may be difficult due to fragmentation of the holdfast and the fact that an apparently single holdfast may originate from more than one zygote. A new method has been developed for estimating the errors due to holdfasts growing together. The mean number of incorrectly recognized individuals per total number of individuals was 4% for destructive sampling and 8% for non-destructive sampling for populations from two sites, both having a sex ratio of 1: 1 males and females. The error is lower for destructive sampling because it is possible to use the dark regions on the section surface of a cut holdfast as a means of separating individuals growing together. Once the errors are estimated, there are several ways of reducing them by at least one half. Although it is possible to distinguish genetic individuals, it is suggested that it be done only in studies where the individual variation in different traits is important and that frond (or other modular unit) behaviour be used in other studies. © 1989 British Phycological Society.