First occurrence of Gracilaria chilensis, and distribution of Gracilariopsis lemaneiformis (Gracilariaceae, Gracilariales) in Peru on the basis of rbcL sequence analysis

Abstract

The terete taxa Gracilariopsis (hereafter Gp.) lemaneiformis (Bory) Dawson, Acleto & Foldvik and Gracilaria (hereafter G.) chilensis Bird, McLachlan & Oliveira resemble each other in branching pattern. This study aims to analyze samples attributed to G. chilensis from a southern locality in Peru using molecular tools, in order to differentiate it from Gp. lemaneiformis samples collected along the Peruvian coast. Species identification of the Gracilariaceae, especially of the terete forms, is notoriously difficult due to morphological plasticity and convergence of their thalli, and the correct taxonomic identification of non-reproductive, cylindrical specimens remains a difficult task (Gurgel & Fredericq 2004). Utilizing traditional morphometric techniques, Edding et al. (2006) concluded that G. chilensis, comprising a single morphotype, is the main species of Gracilaria present along the Chilean coast, in which natural populations are distributed between 30°S and 45°S, from Coquimbo to Southern Chiloe (Bird et al. 1986), with farms extending further north to Antofagasta (24°S) (Santelices & Ugarte 1990). Hoffmann & Santelices (1997) found the establishment of G. chilensis on the coast of Coihaique (45°S) mainly due to aquaculture introduction. This species also occurs in the western Pacific Ocean, ranging from southeastern Australia to New Zealand (Nelson 1987). Gracilariopsis Dawson was long merged into Gracilaria until Fredericq & Hommersand (1989) resurrected Gracilariopsis on the basis of lack of nutritive cells in the cystocarp, and with chorda-type surface spermatangia. Gp. lemaneiformis has a geographical range from Paita, Peru to Antofagasta in northern Chile (Ramírez & Tapia 1991). DNA sequence analysis has been the most reliable and widely used molecular technique to infer phylogenic relationships at the species level within the Gracilariaceae (Gurgel & Fredericq 2004), and recognition of Gracilariopsis as a genus distinct from Gracilaria received strong support from the molecular studies of Bird et al. (1994), and Gurgel et al. (2003), among others. According to Gurgel et al. (2003), Gp. lemaneiformis is shown not to have a worldwide distribution but to be restricted to the vicinity of Peru, whereas the species going under the name Gp. “lemaneiformis” from North and South Carolina is now referred to as Gp. carolinensis Liao et Hommersand, and Gp. “lemaneiformis” from China and Japan constitutes an undescribed species that is related to Gp. heteroclada Zhang et Xia.

Nonnative Gracilaria vermiculophylla tetrasporophytes are more difficult to debranch and are less nutritious than gametophytes

“…The dominance of a particular ploidy phase has attracted attention in the phycological literature (reviewed in Coelho et al 2007); however, empirical tests of differences between ploidies or sexes are rare. In the Gracilariales, tetrasporophytes seem to dominate soft-sediment habitats in which sporic recruitment is severely limited or nonexistent (Kain and Destombe 1995, Guillemin et al 2008b, Krueger-Hadfield et al 2016a, but see Arakaki et al 2015).…”

“…While haploid‐dominated populations in other Gracilaria species have been documented (Kain and Destombe , Arakaki et al. ), we have not yet encountered a gametophyte‐dominated population in the non‐native range of Gracilaria vermiculophylla (Krueger‐Hadfield et al. , ).…”

“…, but see Arakaki et al. ). In the nonnative populations of Gracilaria vermiculophylla , tetrasporophytes dominate (Krueger‐Hadfield et al.…”

“…Gracilarioid species are excellent models with which to empirically test these hypotheses as previously undocumented populations, and even species, are rapidly being found and recorded inhabiting soft‐sediment habitats (e.g., Arakaki et al. , Krueger‐Hadfield et al. ,, ).…”

“…Since Norton and Mathieson's (1983) seminal review on unattached algal populations, very little work has addressed these populations. Gracilarioid species are excellent models with which to empirically test these hypotheses as previously undocumented populations, and even species, are rapidly being found and recorded inhabiting soft-sediment habitats (e.g., Arakaki et al 2015, Krueger-Hadfield et al 2016a,b, 2017. These data will shed light on the invasion ecology of important ecosystem engineers, and advance our ECOLOGICAL DIFFERENTIATION IN GRACILARIA understanding of life cycle evolution, and the maintenance of life cycle diversity.…”