Porichthys notatus: Bioluminescence capability, population structure, and systematics

Porichthys is endemic to near shore environments of the New World and has taxa with bioluminescent capabilities. This study uses mtDNA sequences and morphology to reconstruct phylogenetic relationships within the genus Porichthys (Batrachoididae). I attempt to date specific divergence times between clades. Porichthys is not monophyletic. Further, this study shows a well-supported separation between Atlantic and Pacific Porichthys species. The possible radiation of the genus from the Panamanian and Caribbean provinces is supported by tree topology and estimated divergence times. Further, earlier divergence times in the Atlantic Porichthys indicate an Atlantic origin. The morphological data set is concordant with mtDNA sequence data in showing a strong separation between Atlantic and Pacific Porichthys as well as a radiation of the genus from the Caribbean and Panamanian biogeographic provinces, situated along the equator. I also examine the possibility of assortative mating with respect to bioluminescence capability. Isolation of the luciferase gene was unsuccessful in providing data to assess evolution of bioluminescence within Porichthys. A better probe must be developed to locate the luciferase gene in P. notatus. Greater success may be gained by isolation of the luciferase protein. However, analyses of both mtDNA (mitochondria] DNA) and AFLP (amplified length polymorphisms) data suggest some evidence of isolation due to bioluminescence capability, but assortative mating due to bioluminescence capability is not supported. Further, I study the population genetics of Porichthys notatus along the Northeastern Pacific Coast. I use mtDNA sequence data and AFLPs to assess genetic structure of Porichthys notatus. I found limited structure in P. notatus in Puget Sound, a population north of the historic Cordilleran Ice sheet and Cabrillo, a population within the California transition zone in the Los Angeles area. Genetic data suggests that Puget Sound and Cabrillo are source populations for P. notatus off the Pacific Coast. Despite numerous historical barriers to gene flow, only limited genetic structure exists off the California Coast in P. notatus, implying that deep-water dispersal is common. However, data suggest two source populations exist.