Phenetic variability of stipe morphology in relation to season, exposure, and depth in the non-digitate complex of Laminaria Lamour. (Phaeophyta, Laminariales) in Nova Scotia

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Abstract
In the non-digitate complex of Laminaria in Nova Scotia two reported species, L. agardhii Kjell. and L. longicruris de la Pyl. are difficult to distinguish using the diagnostic criteria of stipe length and stipe hollow occurrence. A study was made of these traits in relation to season, exposure, and depth. A marked seasonal variability in stipe morphology was found. When only mature plants were examined there was found to be a definite tendency for stipe length and hollow occurrence to increase with decreasing exposure. The differentiation of populations in relation to exposure was clinal with overlap in the variation patterns. When stipe morphology was examined in relation to depth, significant differentiation was found only in a population sampled in a sheltered locality. In exposed localities, no such differentiation occurred. In the sheltered site, the variation with depth was attributed to differing developmental class structures at various depths. The major taxonomic finding of the analyses was the lack of non-overlapping criteria by which L. agardhii and L. longicruris may be delimited. Taxonomic decisions on conspecificity will be made on completion of experimental analysis now in progress.

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