Neo-Science of Natural History : Integration of Geoscience and Biodiversity Studies;Proceedings


Resolving Taxonomic Problems of North Pacific Bryozoans

Dick, Matthew H.;Mawatari, Shunsuke F.

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KEYWORDS : Bryozoa;North Pacific;Taxonomy;DNA sequence;Zoogeography


The North Pacific rim is zoogeogographically complex because it is geographically complex and has a complex geological history. Two present-day routes exist for trans-Pacific dispersal of shelfdwelling or intertidal marine organisms: the Bering Sea shelf and the Aleutian archipelago. Dispersal has also been intermittently possible between the Pacific and Atlantic; a seaway connected the North Pacific with the Arctic Ocean in the late Miocene, late Pliocene, and repeatedly during the Quaternary. Ice sheets extending onto the southern Alaskan continental shelf during glacial maxima likely formed a barrier to north-south and east-west dispersal of shelf-dwelling benthic animals. The Bryozoa are one of the most diverse components of intertidal and shelf communities around the North Pacific rim and have a substantial fossil record in the region. Thus they are a good group for addressing evolutionary questions, especially the effects of climatic change on marine benthic faunas. However, their utility in such studies is hampered by poorly resolved alphalevel taxonomy. Lack of resolution stems from the paradigm of cosmopolitanism, difficulty in distinguishing intra- from interspecific variation, and an insufficient understanding of which characters are taxonomically informative. Approaches suggested to resolve these problems include a rejection of cosmopolitanism, detailed study of local bryozoan assemblages with adequate illustration of all species encountered, and utilization of DNA sequence data. To illustrate the power of the third approach, preliminary data are presented from a study that examines the correlation between genetic and morphological variation in an Alaskan population of Rhynchozoon sp. Two divergent lineages of the 16S mitochondrial ribosomal RNA gene were detected, and selected morpholgical characters examined to date suggest the lineages may also be morphologically distinct.