A molecular assay identifies morphological characters useful for distinguishing the sibling species Littorina scutulata and L-plena. Hohenlohe, P. A. & Boulding, E. G. Journal of Shellfish Research, 20(1):453–457, June, 2001.
A molecular assay identifies morphological characters useful for distinguishing the sibling species Littorina scutulata and L-plena [pdf]Paper  abstract   bibtex   
Sibling species Littorina scutulata and L. plena are difficult to distinguish in the field. Here we present anew molecular tool and use it to evaluate the discrete kind quantitative morphological characters that have been proposed as diagnostic. We collected 385 snails of both species from I I sites in Washington state and used restriction enzyme digestion of a PCR-amplified, 480 bp fragment of the mitochondrial cytochrome b gene to distinguish the species, This new molecular assay produces species-specific restriction fragment patterns that correspond with identification of males by penis morphology. To evaluate the usefulness of morphological characters, we scored three discrete shell characters (presence of basal band, presence of basal ridge, and size of checker pattern) as well as tentacle coloration. The four discrete characters differ significantly between the two species, though none is completely diagnostic. Tentacle coloration is the most reliable character and may be combined with the shell characters for successful identification. The two species also differ significantly in overall size and in three out of five size-independent shell shape measurements, with L. scutulata having larger, taller-spired shells with narrower apertures. However, shell shape does not separate the species well because of intraspecific variation, and it is unlikely to be useful for species identification. Further analysis suggests that at least some of this intraspecific variation is genetic rather than environmental. The distributions of the two species overlap broadly in Washington, though only L. plena was found in exposed outer coast habitats, contrary to previous work.
@article{hohenlohe_molecular_2001,
	title = {A molecular assay identifies morphological characters useful for distinguishing the sibling species {Littorina} scutulata and {L}-plena},
	volume = {20},
	shorttitle = {A molecular assay identifies morphological characters useful for distinguishing the sibling species {Littorina} scutulata and {L}-plena},
	url = {http://webpages.uidaho.edu/hohenlohe/Hohenlohe&Boulding2001.pdf},
	abstract = {Sibling species Littorina scutulata and L. plena are difficult to distinguish in the field. Here we present anew molecular tool and use it to evaluate the discrete kind quantitative morphological characters that have been proposed as diagnostic. We collected 385 snails of both species from I I sites in Washington state and used restriction enzyme digestion of a PCR-amplified, 480 bp fragment of the mitochondrial cytochrome b gene to distinguish the species, This new molecular assay produces species-specific restriction fragment patterns that correspond with identification of males by penis morphology. To evaluate the usefulness of morphological characters, we scored three discrete shell characters (presence of basal band, presence of basal ridge, and size of checker pattern) as well as tentacle coloration. The four discrete characters differ significantly between the two species, though none is completely diagnostic. Tentacle coloration is the most reliable character and may be combined with the shell characters for successful identification. The two species also differ significantly in overall size and in three out of five size-independent shell shape measurements, with L. scutulata having larger, taller-spired shells with narrower apertures. However, shell shape does not separate the species well because of intraspecific variation, and it is unlikely to be useful for species identification. Further analysis suggests that at least some of this intraspecific variation is genetic rather than environmental. The distributions of the two species overlap broadly in Washington, though only L. plena was found in exposed outer coast habitats, contrary to previous work.},
	number = {1},
	journal = {Journal of Shellfish Research},
	author = {Hohenlohe, P. A. and Boulding, E. G.},
	month = jun,
	year = {2001},
	keywords = {Littorina scutulata},
	pages = {453--457},
}
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