Spatial distribution and reproductive phenology of sexual and asexual Mastocarpus papillatus (Rhodophyta)

Abstract

Fierst J.L., Kübler J.E. and Dudgeon S.R. 2010. Spatial distribution and reproductive phenology of sexual and asexual Mastocarpus papillatus (Rhodophyta). Phycologia 49: 274–282. DOI: 10.2216/09-41.1

Species of the genus Mastocarpus exhibit two distinct life cycles, a sexual alternation of generations and an obligate, asexual direct life cycle that produces only female upright fronds. In the intertidal red alga, M. papillatus (Kützing) sexual fronds dominate southern populations and asexual fronds dominate northern populations along the northeast Pacific coast, a pattern of spatial separation called geographic parthenogenesis. Along the central coast of California, sexual and asexual variants occur in mixed populations, but it is not known whether they are spatially separated within the intertidal zone at a given site. We investigated reproductive phenologies and analyzed patterns of spatial distributions of sexual and asexual M. papillatus at three sites in this region. Sexual M. papillatus were aggregated lower on the shore at two sites and only reproduced during part of a year, while asexual M. papillatus occurred throughout the intertidal range at all sites and reproduced throughout the year. The distribution patterns of sexual and asexual M. papillatus are consistent with a hypothesis of shoreline topography influencing their dynamics of dispersal and colonization. Spatial and temporal partitioning may contribute to the long-term coexistence of sexual and asexual life histories in this, and other, species of Mastocarpus. The occurrence of geographic parthenogenesis at multiple spatial scales in M. papillatus provides an opportunity to gain insight into the phenomenon.

Key Words::

• Apomictic
• Geographic parthenogenesis
• Life cycle
• Mastocarpus papillatus
• Phenology
• Red algae
• Sexual reproduction
• Spatial division
• Tidal elevation

ACKNOWLEDGMENTS

This paper represents partial fulfilment of the Master's degree of J.L. Fierst. We are grateful to P. Raimondi, C. Roe, and C. Hays who graciously provided unpublished data on site characteristics and temperatures for our three sites. We thank John West, Gary Kendrick, and an anonymous reviewer whose comments improved this manuscript. This research was supported by grants from the Phycological Society of America (2001, 2002), PADI Project Aware (2000, 2002), Sigma Xi, and the California State University at Northridge Office of Graduate Studies, Research and International Programs to J.L. Fierst and by grants from the National Institutes of Health (NIH-5SO6GM48680) and California State University at Northridge Sponsored Programs office to S.R. Dudgeon. This paper represents contribution number 136 from the California State University at Northridge Marine Biology Group.