MEPS 250:91-103 (2003)  -  doi:10.3354/meps250091

Field testing of inter- and intraspecific coalescence among mid-intertidal red algae

Bernabé Santelices*, Diego Aedo, Marcela Hormazábal, Verónica Flores

Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile

ABSTRACT: Although spores, sporelings and juveniles of many ecologically important and competitively dominant seaweed species inhabiting intertidal and shallow subtidal habitats may coalesce, it is unknown whether coalescence among holdfasts of well-established clumps occurs naturally in the field. Using a combination of field and ultrastructural studies, we evaluate if inter- and intraspecific coalescence occurs between clumps of Mazzaella laminarioides and Nothogenia fastigiata and, if so, whether such a process modifies clump shapes and sizes. Interspecific encounters always resulted in cell compression and destruction of the contacting tissues and in the eventual mortality of 1 of the partners (in this case N. fastigiata). In contrast, intraspecific encounters in both species always resulted in coalescence. In these field populations, coalescence seems to be frequent and dynamic and is probably modulated by other community structuring mechanisms such as grazing, abiotic extremes, and mussel recruitment. This field demonstration of coalescence suggests that many intertidal and subtidal populations of coalescing Rhodophyta might be chimeric.

KEY WORDS: Chimerism · Coalescence · Competition · Algae shape · Intertidal habitats · Mazzaella · Nothogenia · Red seaweeds

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