COLLISELLA AUSTRODIGITALISSP. NOV.: A SIBLING SPECIES OF LIMPET (ACMAEIDAE) DISCOVERED BY ELECTROPHORESIS

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Abstract
A geographic survey of protein polymorphism in the intertidal limpet Collisella digitalis reveals that populations from northern California and Oregon have allelic frequencies at a leucine aminopeptidase locus that are sufficiently different from populations in southern California that individuals can be correctly assigned to their geographic entity with a 98.8% probability on the basis of their genotype. These two groups also have different allelic frequencies at a phosphoglucose isomerase locus, but only slight morphological differences between the groups are evident. Genotype frequency analysis shows that on the central California coast between Monterey Bay and Point Conception both the northern and southern groups are present, but not interbreeding. Thus, these groups are sibling species. The southern species is herein named Collisella austrodigitalis sp. nov. These species are thought to have originated by allopatric speciation, perhaps following the spatial isolation of a population of C. austrodigitalis during an equatorward contraction of that species' range in response to one of the late Cenozoic world wide cooling trends.