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


A Preliminary Observation of Rapid Changes of Gill Raker Number in Miyabe Charr (Salmonidae) over a Short Term Period

Kobayashi, Haruki;Maekawa, Koji

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KEYWORDS : Changing environment;Rapid evolution;Microevolution;Miyabe charr


We present a preliminary discussion of a case study that is underway to examine whether gill raker number of Miyabe charr (Salvelinus malma miyabei) on Hokkaido, Japan is undergoing a rapid adaptive response to changing environmental conditions. The study involves two populations, one in Shikaribetsu Lake and the other in the Torizaki River. Preliminary data based on museum specimens and recently collected material suggest a rate of increase in gill raker number in the Shikaribetsu Lake population over the past 60 years that is an order of magnitude greater than the estimated average rate of increase since the population became isolated about 10,000 years ago. Conversely, gill raker number in the Torizaki population has decreased since introduction about 30 years ago. We discuss both microevolution and phenotypic plasticity in relation to the observed changes. We emphasize the importance of natural history collections to the study of microevolution.