Document: ALE-3-16-4

Aquarium trade and success of the green tropical alga Caulerpa taxifolia invading the Mediterranean Sea.

MEINESZ, A.*

University of Nice - Sophia Antipolis, Nice, France ¹

Abstract:
Caulerpa taxifolia, introduced since 1984 in the Mediterranean Sea extends regularly over more than 6000 hectares along the shoreline of 5 countries, but 90 % of the covered areas are still in the vicinity of the introduction point (under a public aquarium where it was cultivated). Sixteen years after its introduction, phenotypic characteristics of C. taxifolia are unchanged but are quite different from the tropical strains: (i) exceptionally great frond length, (ii) high growth rate, biomass, densities and ecological ranges, never described elsewhere over such large areas, (iii) abnormal gametogenesis (only male gametes), and (iv) resistance to cold temperatures. Studies on the ITS rDNA sequence have shown an identity between the aquarium strains (cultivated in Europe since 1969) and the Mediterranean introduced strain, which, in the absence of sexual reproduction, seems to be a single clone. Two hypothesis can explain the success of the invader: (i) in the aquarium trade network, random selection of an aquarium-Mediterranean adapted clone found in a natural population (C. taxifolia from Moreton Bay, southwestern Australia seems actually the most closely related), (ii) from a closely related tropical strain, selection or evolution of the invader clone by the artificial conditions of culture in aquarium before its release in the Mediterranean Sea. Whatever the reason, human artificial selection of resistant aquarium organisms from world wide origin seems to be the prevailing reason of the success of this marine pest.

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This abstract is being presented at: 1:35 PM in session:
Symposium #6: Ecological Consequences of Adaptive Evolution Among Invasive Species in Terrestrial and Marine Systems.