A revised checklist and preliminary assessment of the macrobenthic marine algae and seagrasses of Oregon

A new checklist of the macrobenthic marine algae and seagrasses of Oregon is presented. The list includes 50 new records and 89 new names, providing an overall nomenclatural change in the recorded flora of 36 percent since the earlier list of Phinney (1977). Of the 387 taxa reported, 20 percent have distributional boundaries within the state, indicating that Oregon is an area of relatively minor floristic change. Species overlap analyses with the floras of SE Alaska-Washington and California show that the Oregon flora is closer in composition to its northern neighbor than to its southern (Jaccard coefficients of 54 and 44, respectively). Species richness is surprisingly low: Oregon has 227 fewer taxa than SE Alaska-Washington and 336 fewer than California. The depauperate nature of the flora has been proposed to be caused by latitudinal range and temperature differences, lack of sheltered habitats, sand domination, seasonal upwelling, and human disturbance. Some of these factors are influential. However, an analysis of taxa with west-coast distributions skipping Oregon indicates that many taxa may have been overlooked because of their small size, crustose morphology, and/or subtidal location. The lack of species richness is therefore also attributed to insufficient study. Additional surveys concentrating on the cryptic taxa will be necessary to determine if Oregon's seaweed flora is truly species-poor. Within the checklist, the following new binomials have been proposed: Botrytella pacifica (Hollenberg) comb. nov., Cryptopleura farlowiana (J. Agardh) ver Steeg et Josslyn comb. nov., and Kallymeniopsis oblongifructa (Setchell) comb, nov.