The kelp Lessonia nigrescens Bory is the most ecologically and economically important seaweed in rocky intertidal and shallow subtidal habitats along the temperate Pacific South American coasts. Recent molecular studies suggest the existence of two lineages, one (northern lineage) from 17° S to 30° S and a second (central lineage) from 29° S to 41° S. To identify and name these lineages we performed morphological, nomenclatural and field studies. Four external and three internal anatomical traits permitted a morphological separation of the two lineages. The internal structure of both lineages was different from the isolectotype of Lessonia nigrescens. It is therefore concluded that the name Lessonia nigrescens should not be used for the Chilean material. Chordaria spicata Suhr appears as the oldest available name for the central lineage, while Lessonia berteroana Montagne is the oldest name for the northern lineage. In both cases, the type material consisted of small-sized, apical branches of larger plants. The new combination Lessonia spicata (Suhr) Santelices is proposed for the central lineage and we reinstate Lessonia berteroana for the northern lineage. Laminaria scissa Suhr is reduced to synonym of L. spicata. Representative specimens of Lessonia nigrescens were not found during new visits to its type locality in Cape Horn and along Chile. Future studies should verify the status of this species.

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How closely related marine organisms mitigate competition for resources while foraging at sea is not well understood, particularly the relative importance of interspecific and intraspecific mitigation strategies. Using location and time-depth data, we investigated species-specific and sex-specific foraging areas and diving behaviour of the closely related Humboldt (Spheniscus humboldti) and Magellanic (S. magellanicus) Penguins breeding in sympatry at Islotes Puñihuil in southern Chile during the chick-rearing period. The average duration of foraging trips was <20 h and did not differ significantly between species or between sexes of each species. Magellanic Penguins made significantly deeper and longer dives than Humboldt Penguins. Males of both species made significantly longer dives than females. Total distance travelled per foraging trip was significantly greater for males than for females, and females made more direct trips (less sinuous) than males. Foraging effort was concentrated in waters up to 15 km to the west and south-west of the colony. The overlap in density contours was lower between species than between sexes within a species. In general, dive characteristics and foraging areas differed more between Magellanic and Humboldt Penguins than between the sexes of each species. In contrast to the findings of studies of flying seabirds, the foraging behaviour of these penguins differs more between species than between sexes.