Genetic diversity in Undaria pinnatifida (Laminariales, Phaeophyceae) deduced from mitochondria genes – origins and succession of introduced populations

Abstract

S. Uwai, W. Nelson, K. Neill, W.D. Wang, L.E. Aguilar-Rosas, S.M. Boo, T. Kitayama and H. Kawai. 2006. Genetic diversity in Undaria pinnatifida (Laminariales, Phaeophyceae) deduced from mitochondria genes – origins and succession of introduced populations. Phycologia 45: 687–695. DOI: 10.2216/05-66.1To elucidate the genetic diversity of the brown alga Undaria pinnatifida in native and introduced populations worldwide, and to discuss the transoceanic introduction processes, we investigated the haplotype divergence of the mitochondrial loci of the coding region of cox3 and noncoding region between tatC and tLeu genes. In its native range (Japan, Korea and China), we found 27 haplotypes, which were classified into 4 genetic and biogeographical groups: (1) Northern Japan type, distributed in Hokkaido and Pacific northern Honshu; (2) Continental type, found in Korea and China; (3) Pacific central Japan type; and (4) Sea of Japan type. Among the introduced populations, European and Mexican populations agreed with the Northern Japan type. In Australia, the Tasmanian population agreed with the Sea of Japan type, whereas the Victorian population was of the Continental type. Very high diversities were found in New Zealand: 10 haplotypes were found (including 2 only in old herbarium specimens), including both the Northern Japan type and the Continental type. The haplotype found in California agreed with a component of the Central Japan type collected at Kanagawa Prefecture. The samples from Argentina agreed with the Continental type. The alignment of the European populations with the Northern Japan type is consistent with the notion that the Undaria in Europe was first introduced with oyster spat. It is speculated that Californian and Mexican populations were recently introduced by shipping vectors. There have been many introduction events to New Zealand since the late 1980s, and the dominant haplotypes in the local populations appear to have changed over time. Introduction to Argentina/Australia (Victoria) could have resulted from secondary introductions from New Zealand populations, because transport within the same latitudinal range is considered to be easier than transport by shipping across the equator. Within Japan, the occurrence of both the Continental and the Northern Japan types in the Osaka Bay area is considered to be the result of recent intentional introduction for fisheries purposes.