Differences of spatial distribution and seasonal succession among Ulva species (Ulvophyceae) across salinity gradients

Abstract

Ogawa T., Ohki K. and Kamiya M. 2013. Differences of spatial distribution and seasonal succession among Ulva species (Ulvophyceae) across salinity gradients. Phycologia 52: 637–651. DOI: 10.2216/13-199.1

Ulva species are common along seashores as well as in brackish lakes and estuaries, and recent molecular phylogenetic examinations have revealed inter- and intraspecific genetic diversity and wide distributions across oceans. However, Ulva species are difficult to identify because of their simple morphologies and high plasticity, and thus ecological properties such as salinity preference and phenology have been reported for a limited number of species. This study examined the genetic diversity, spatial distribution, and seasonal succession of Ulva species collected from various salinity regimes in Mikata-goko and Minami River, Fukui, Japan, during a 2-year period. By analysing the internal transcribed spacer regions of 125 specimens from a marine site and 1169 specimens from seven brackish sites, we detected four marine species (Ulva compressa, U. linza, U. torta, and Ulva sp. 1) and six brackish species (two subspecies of U. flexuosa, U. limnetica, U. prolifera, U. simplex, Ulva sp. 2, and Ulva sp. 3). Two additional species (U. californica and Ulva sp. 4) were found in other brackish lakes. Roughly three distribution patterns (low- and high-salinity brackish, and wide-range) were recognized among the brackish species. Phenological patterns were diverse among Ulva species: some species appeared only for a few months, and others were found at all times of the year. More than one ribotype, including heterozygous ribotypes, were detected within each of the five species (U. linza, U. prolifera, U. simplex, U. torta, and Ulva sp. 1). In the most dominant species U. prolifera, ribotypes pro1, pro2, and pro1/2 were distributed from low- to high-salinity brackish sites; whereas, the other five ribotypes were restricted to the high-salinity brackish sites, suggesting ecotypic differentiation within U. prolifera.

Key Words::

• Brackish water
• Estuary
• Internal transcribed spacer
• Phenology
• rbcL

ACKNOWLEDGEMENTS

The authors would like to acknowledge the staffs of the Fukui Prefectural Kaihin Shizen Center for supporting sampling. We are grateful to Dr. Shinya Yoshikawa for valuable discussion. This work was financially supported by the Mikimoto Fund for Marine Ecology and JSPS KAKENHI (19570092).

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/13-199.1.s1.