Regional genetic structure and genetic founder effects in the invasive lionfish: comparing the Gulf of Mexico, Caribbean and North Atlantic.
Indo-Pacific lionfish (Pterois volitans and P. miles) recently invaded Western Atlantic waters, rapidly spreading through the Caribbean and Gulf of Mexico (GoM). Previous genetic analyses using the mitochondrial d-loop determined that populations in the Western North Atlantic (NA) region have up to nine haplotypes, whereas Caribbean populations contain four of the North Atlantic haplotypes. The genetic composition of GoM populations, reported here for the first time, could lend insight into the pathway of dispersal into the GoM and better understanding of the biogeography of this recent invader. Here, we determined the genetic composition of lionfish throughout the GoM and compared haplotype composition to Caribbean and North Atlantic regions. We found that GoM samples contained only three d-loop haplotypes that are common in the Caribbean and North Atlantic. The genetic structure differed significantly among the three regions (AMOVA: ΦCT=0.062; p=0.001), but we found no differences between locations within regions (AMOVA: ΦSC=0.005; p=0.092). The composition of GoM samples most closely matches the composition of Caribbean samples indicating that Caribbean populations are the likely source of the GoM populations. As each region was successively invaded, a drop in haplotype diversity and changes in haplotype frequencies occurred indicating dispersal limitation across basin boundaries and founder effects within each basin. The lack of differentiation within regions indicates rapid population growth and unfettered dispersal within basins after initial colonization. We find no evidence of secondary invasions within samples. With well-established populations, the probability of detecting a secondary invasion is minuscule.