Where are they now? The fates of two genetic lineages in an introduced Hawaiian reef fish

Abstract

Humans, both wittingly and unwittingly, have been transporting marine organisms beyond their native ranges for centuries (Ruiz et al. 1997). A central challenge of invasion biology is to identify the factors that determine whether introduced species fail to become established, become benign members of a community, or spread so far and reach such densities as to be considered invasive. Organismal features such as physiological tolerance, niche breadth and fecundity are critical, but by themselves are inaccurate predictors of the fates of introduced species (Sakai et al. 2001). The size, age distribution, and genetic makeup of founder populations are also important, but because they are usually unknown they are most often viewed as sources of uncertainty. For marine species with planktonic larvae, the challenge is even greater because the consequences of a planktonic phase for dispersal and population viability are not well understood. In this issue, Gaither et al. (2010a) present a remarkable account of the introduction of a reef fish for which the number and genetic makeup of the founders are known. Between 1956 and 1961, the Division of Fish and Game for the Territory of Hawaii introduced 12 non-indigenous fish species into Hawaiian waters to establish commercial and sport fisheries. The introduction of Lutjanus kasmira, the bluestriped snapper, was the most successful (Fig. 1). There were two releases of fish from French Polynesia. In 1958, 2431 fish from the Marquesas Islands were released on Oahu, followed in 1961 with an additional 728 fish from the Society Islands. The blue striped snapper rapidly spread to the other Hawaiian Islands, reaching the northwestern end of the archipelago by 1992. The choice of the Marquesas as one of two sources for the introduction was fortuitous. Gaither et al. (2010b) found that the Marquesas population is genetically distinct from all other Indo-Pacific populations of L. kasmira. Mitochondrial cytochrome b sequences of fish from the Marquesas belong to a separate lineage that diverged from others in the species roughly half a Ma. Allele frequencies for several nuclear loci are also distinct. This provided Gaither et al. (2010a) with an extraordinary opportunity to examine what became of the mixed genetic heritage of Hawaiian blue striped snappers after 50 years.