Relative contribution of vegetative propagation and sexual reproduction in the maintenance of Acrosiphonia (Chlorophyta) populations

Abstract

A.V. Sussmann and R.E. Dewreede. 2007. Relative contribution of vegetative propagation and sexual reproduction in the maintenance of Acrosiphonia (Chlorophyta) populations. Phycologia 46: 79–85. DOI: 10.2216/06-33.1

We provide evidence for new vegetative growth in spring from overwintering basal remnants of the green alga Acrosiphonia (Codiolales sensu van den Hoek et al. 1995) long after mortality of the filamentous thalli at two independent study sites in Barkley Sound, British Columbia, Canada. The two study sites differed in Acrosiphonia species composition, abundance and seasonality, but were both characterised by disturbance. At Prasiola Point we estimated approximately 15–30% Acrosiphonia recruitment to originate from vegetative regrowth (based on mapping individual thalli). At Seppings Island significantly lower Acrosiphonia recruitment on cleared boulders than uncleared boulders provided an estimate of approximately 50% recruitment from vegetative regrowth. These results increase our understanding of the complex life history of Acrosiphonia in southwestern British Columbia by detecting the role of vegetative propagation in the maintenance of sexually reproducing populations. The previously undocumented capacity to regenerate in the field by vegetative means also explains the seasonally dense occurrence of the gametophyte phase and Acrosiphonia's success in colonising disturbed environments. In conditions of limited zoospore availability, dispersal and attachment it is advantageous for populations to regenerate vegetatively.

Key Words::

• Acrosiphonia
• Overwintering basal remnants
• Recruitment
• Reproductive strategy
• Sexual reproduction
• Sporic life history
• Vegetative propagation

ACKNOWLEDGMENTS

The authors thank Stefanie Leung, Jeong Ha Kim and Leonard Dyck for their assistance in the field. Also, thanks to Hannah Henderson for her computer skills. This work was funded by a research fellowship from the Natural Sciences and Engineering Research Council of Canada to A.V.S. and an NSERC Discovery Grant to R.E.D. Facilities and equipment available at the Bamfield Marine Sciences Centre were utilised, and the Huuahy-at Band allowed us to conduct work at Prasiola Point, Barkley Sound.