RESUMO
Recent molecular investigations of the small-subunit rRNA gene sequences have indicated that established taxonomic hierarchies can be clearly at odds with the degree of evolutionary divergence (as inferred from molecular divergence) between supposedly equivalent taxa at every rank (i.e., species through class), both within and across biological divisions. This is particularly true between the Rhodophyta and the Phaeophyta, whose higher-order taxa appear under- and overinflated, respectively. We present two plausible alternatives that algal taxonomists might adopt in order to invoke discussion on their relative merits.
Assuntos
Eucariotos/classificação , Eucariotos/genética , Filogenia , Phaeophyceae/classificação , Phaeophyceae/genética , RNA Ribossômico/genética , Rodófitas/classificação , Rodófitas/genéticaRESUMO
The distributions of Laminaria saccharina and the long and short stipe forms of L. groenlandica about Vancouver Island were correlated with temperature, salinity, and water motion. The 2 forms of L. groenlandica were absent from areas of high temperature and low salinity. The long stipe form was restricted to areas of heavy surf and the short stipe form to areas of moderate surf. L. saccharina was absent from areas subjected to surf. These observations were subjected to laboratory and field tests involving gametophytes and sporophytes of both species. The distributions of the 2 forms of L. groenlandica can be explained on the basis of temperature and salinity distributions: both forms require low temperature and high salinity for survival. L. saccharina has a wide range of tolerance to temperature and salinity; surf appears to be the controlling agent.
