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Marine Ecology Progress Series

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MEPS 182:299-303 (1999)  -  doi:10.3354/meps182299

The role of vegetative fragmentation in dispersal of the invasive alga Caulerpa taxifolia in the Mediterranean

Giulia Ceccherelli1,*, Francesco Cinelli2

1Dipartimento di Botanica ed Ecologia Vegetale, Università di Sassari, via Muroni 25, I-07100 Sassari, Italy
2Dipartimento di Scienze dell'Uomo e dell'Ambiente, Università di Pisa, via A. Volta 6, I-56126 Pisa, Italy

ABSTRACT: This study evaluated the importance of fragmentation in the recruitment of the fast-spreading, introduced green alga Caulerpa taxifolia at the margins of beds of the seagrass Posidonia oceanica. A multifactorial experiment was designed to test the hypotheses that there are seasonal differences in patterns of establishment of vegetative fragments, whether this process changes with depth and whether these patterns were consistent at different spatial and temporal scales. Our experimental approach consisted of dispersing drifting fragments of C. taxifolia along the margin of a bed of P. oceanica and recording the number of fragments established after 1 mo. The results show that a surprisingly large number of fragments become established in this habitat and that numbers varied in space and time: the probability of establishment of fragments was greatest during summer especially at the shallow sites, but smaller in spring and smallest in winter. Differences among areas were also found: a great variability in establishment of fragments depended on the site and time within season. Results indicate that dispersal by fragmentation can greatly contribute to a very wide spread of the alga in the Mediterranean. We predict that spread will be greatest during summer when a large proportion of fragments can re-attach to the substratum, even at shallow sites. Such information is important for the understanding of the ecology of this species and, with the help of hydrographic studies, in the prediction of its patterns of geographic dispersal.

KEY WORDS: Caulerpa taxifolia · Dispersal · Vegetative reproduction · Introduced alga · Fragmentation · Colonisation

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