Morphological differentiation of cryptic lineages within the invasive genus Asparagopsis (Bonnemaisoniales, Rhodophyta)

Abstract:

Rapid identification of introduced seaweeds is crucial to support management and conservation decisions, especially when multiple cryptic lineages of high-profile invasive taxa occur sympatrically. The red seaweed genus Asparagopsis (Bonnemaisoniales, Rhodophyta) comprises two recognised morpho-species characterised by heteromorphic life cycles and presumably morphologically identical ‘Falkenbergia’ tetrasporophyte stages: A. armata and A. taxiformis. Populations of the former were easily identified by the presence of distinctive harpoon-like braches on the gametophyte thalli. Four morphologically cryptic yet genetically distinct mitochondrial lineages of invasive nature were recognised within A. taxiformis. We reported a morphological delineation of tetrasporophytes and gametophytes of Asparagopsis, including cryptic lineages collected from the Mediterranean Sea and the Hawaiian Islands, where multiple Asparagopsis lineages were present. Vegetative anatomical characters of the tetrasporophytes were useful in differentiating A. armata from those of A. taxiformis as well as among tetrasporophyte isolates belonging to the four A. taxiformis lineages. In addition, these characters distinguished lineage 2 native range specimens (Hawaii) from the invasive specimens (Mediterranean Sea), which suggested high levels of morphological plasticity in the invasive taxon. We propose that the taxonomic status of the lineages within A. taxiformis needs to be revised.

Key Words::

• Falkenbergia
• Identification
• Management
• Morphology
• Reproductive
• Taxonomy
• Vegetative

ACKNOWLEDGEMENTS

This work was funded by the project CGL2008/01549/BOS, P09-RNM-5187 (Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain), 806/5.03.3553 and 806/5.03.3673 (Instituto de Estudios Ceutíes, Spain) and a Research Collaboration Agreement between Consejería de Medio Ambiente de la Junta de Andalucía and the University of Málaga. M.Z. is a PhD student, project P09-RNM-5187, at the Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain. Also supported by “El Plan Propio” of the University of Málaga. N.A. is supported by the Commonwealth Research and Environment Facilities (CERF) Marine Biodiversity Hub. Analyses of Hawaiian specimens were supported by a US National Science Foundation grant DEB-0542608 to A.R.S. and G.G. Presting. We thank two anonymous reviewers for their useful comments on previous versions.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/13–247.1.s1.