Cryptic diversity, biogeography and genetic variation in Northeast Pacific species of Porphyra sensu lato (Bangiales, Rhodophyta)

Abstract

We sequenced the chloroplast rubisco large subunit (rbcL) gene in 236 samples of Porphyra sensu lato from the northeast Pacific. Comparisons of sequences within the study area as well as comparisons with published sequences revealed up to five cryptic species among the 22 named species: a species closely related to Porphyra abbottiae, a species previously identified as P. pseudolinearis, a species closely related to P. pseudolanceolata and previously identified as that species, a previously unknown species from the eastern Aleutian Islands, and a species closely related to P. schizophylla and previously identified as that species. All of these previously unrecognized species had high bootstrap values separating them from the other species. In addition, our wide geographic sampling allowed us to extend, curtail or clarify the geographic ranges of a number of the species. We also provide published sequences for P. gardneri and P. smithii for the first time. We compared amount of sequence divergence within species grouped on the basis of sexuality (monoecious, sectored into separate male and female “halves”, or dioecious), habitat (high, mid, or low intertidal/subtidal), and seasonality (winter, spring, or summer) using Tukey’s HSD t test, but we observed no significant differences between species grouped in this manner. Different species showed different levels of genetic variation in the rbcL gene apparently unrelated to these traits. Also, we observed no differences in the patterns of genetic variation in a species based on whether the specimens were collected from outside or from within the region covered by ice during Pleistocene glaciations.