THE INVASIVE GENUS ASPARAGOPSIS (BONNEMAISONIACEAE, RHODOPHYTA): MOLECULAR SYSTEMATICS, MORPHOLOGY, AND ECOPHYSIOLOGY OF FALKENBERGIA ISOLATES¹

Abstract

The genus Asparagopsis was studied using 25 Falkenbergia tetrasporophyte strains collected worldwide. Plastid (cp) DNA RFLP revealed three groups of isolates, which differed in their small subunit rRNA gene sequences, temperature responses, and tetrasporophytic morphology (cell sizes). Strains from Australia, Chile, San Diego, and Atlantic and Mediterranean Europe were identifiable as A. armata Harvey, the gametophyte of which has distinctive barbed spines. This species is believed to be endemic to cold‐temperate waters of Australia and New Zealand and was introduced into Europe in the 1920s. All isolates showed identical cpDNA RFLPs, consistent with a recent introduction from Australia. Asparagopsis taxiformis (Delile) Trevisan, the type and only other recognized species, which lacks spines, is cosmopolitan in warm‐temperate to tropical waters. Two clades differed morphologically and ecophysiologically and in the future could be recognized as sibling species or subspecies. A Pacific/Italian clade had 4–8° C lower survival minima and included a genetically distinct apomictic isolate from Western Australia that corresponded to the form of A. taxiformis originally described as A. sanfordiana Harvey. The second clade, from the Caribbean and the Canaries, is stenothermal (subtropical to tropical) with some ecotypic variation. The genus Asparagopsis consists of two or possibly three species, but a definitive taxonomic treatment of the two A. taxiformis clades requires study of field‐collected gametophytes.

Microsatellite markers in an invasive strain of Asparagopsis taxiformis (Bonnemaisoniales, Rhodophyta): Insights in ploidy level and sexual reproduction

“…The similarity between the Californian population and the two Mediterranean populations is congruent with findings obtained with the cox marker because the three populations all belong to lineage 2 whereas the more distantly related Hawaiian population belongs to cox lineage 1. Moreover, failure of the microsatellite primers to generate any products with thalli in lineages 3 and 4 corroborated the distinction of lineage 3 and 4 from lineages 1 and 2 and confirms the existence of cryptic diversity in A. taxiformis reported by Ní Chualáin et al (2004) and by Andreakis et al (2004Andreakis et al ( , 2007.…”

“…Ní Chualáin et al (2004) revealed ecophysiological dissimilarities between Atlantic and Indo-Pacific-Mediterranean populations. Recently, four morphologically identical but genetically divergent mitochondrial lineages within A. taxiformis specimens collected worldwide were uncovered (Andreakis et al, 2007) suggesting cryptic speciation events within the species.…”

Eco-touristic snorkelling routes at Marinha beach (Algarve): Environmental education and human impacts

“…This fact coincides with the disappearance from the samples of Asparagopsis armata, the most abundant non-calcareous red algae of the 2008 census. A. armata, a recent invasive species from Australia [62], has long hooked stolons [63], which enable the algae to get entangled with other marine organisms and, thus cover large areas of the substrate [64]. The life cycle and temperature tolerance of this species is rather complex, requiring short day lengths [65,66] and temperatures approximately between 17°C and 18°C [62,65].…”

Ecophysiological studies of the non-indigenous speciesGracilaria vermiculophylla(Rhodophyta) and its abundance patterns in Ria de Aveiro lagoon, Portugal

“…However, spore recruitment of G. vermiculophylla at northern latitudes is limited to warmer months and this may have an effect in regulating the species' northern distribution. In its native Pacific region, G. vermiculophylla has an extensive latitudinal range (www.algaebase.org; Kim et al, 2010) and multiple introductions of NIS have been reported, for example for Asparagopsis armata (Guiry & Dawes, 1992;Chuala´in et al, 2004). The low survival success of Ria de Aveiro G. vermiculophylla spores at 5 C could therefore reflect a different introduction from the western Pacific region than the populations in northern Europe: Kim et al (2010) found that the same haplotype was common in populations of G. vermiculophylla in northern Europe and the probable original donor population but unfortunately, no samples were included from any southern European site; Rueness (2005) suggested that G. vermiculophylla reached northern Europe through secondary introduction from the south.…”