Ariolimax columbianus

Recent unpublished evidence suggests Ariolimax columbianus is not monophyletic but rather that populations north of Mendocino Co., California (= Ariolimax columbianus) are evolutionarily distinct from the more southern populations (potentially attributable to the name Ariolimax buttoni (Pilsbry and Vanatta, 1896)) (see Leonard et al., 2007). The genus Ariolimax Mörch, 1860 is currently broken into 5 taxa in 2 subgenera based on penis morphology. In A. (Ariolimax), sensu stricto, A. (A.) columbianus columbianus (Gould, 1851) ranges from central California to southeast Alaska while A. (A.) c. stramineus Hemphill, 1891 is found on the coast of south-central California. In A. (Meadarion) Pilsbry, 1948. A. (M.) dolichophallus Mead, 1943, A. (M.) californicus californicus Cooper, 1872, and A. (M.) c. brachyphallus Mead 1943 are known from different parts of the San Francisco Peninsula. Sequence data from 3 mitochondrial and 2 nuclear genes (unpublished but see Pearse et al., 2007) reveal an unresolved polytomy of 5 distinct clades- but not the original 5. There are 2 clades within A. (A.) c. columbianus, for which Pearse et al. (2007) propose species rank: A. columbianus ranging from northwest California to southeast Alaska and A. buttoni (Pilsbry and Vanatta, 1896) in north-central California. A. stramineus forms a third species-clade, and a fourth distinct clade is an undescribed species on Mount Palomar, San Diego County, California. The fifth clade (Meadarion) comprises at least 4 subclades, 3 already named as species or subspecies. Pearse et al. (2007) propose treating each as a species distinguished by morphology and sexual behavior: A. californicus and A. dolichophallus are found mainly in San Mateo and Santa Cruz counties, respectively, while A. brachyphallus has a disjunct distribution on the northern tip of the San Francisco Peninsula, the Monterey Peninsula in Monterey County, and Cambria in San Luis Obispo County. A fourth subclade corresponds to an undescribed species found on Fremont Peak, San Benito County. More in-depth analyses are needed to resolve the relationship among these 8 species, and whether the subgenus Ariolimax is paraphyletic with respect to Meadarion.

This species is widespread from central California to southern Alaska.

Recent molecular evidence suggests that A. columbianus, as defined by Mead (1943) and Pilsbry (1948), is not monophyletic but rather that populations of Ariolimax north of Mendocino Co., California (the true A. columbianus, since the species was described from specimens collected near the Columbia River) are evolutionarily distinct from the more southern populations (Leonard et al., 2005; Pearse et al., 2005). The name Ariolimax buttoni (Pilsbry and Vanatta, 1896) has been revived to designate the southern clades formerly included in A. columbianus (see Leonard et al., 2007). As such, A. columbianus occurs from the area north of Mendocino Co., California, north to southeastern Alaska (Pilsbry, 1948; Roth and Sadeghian, 2003; Leonard et al., 2007).