identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
DB1087FCFFA9D546FF40FB4663308B53.text	DB1087FCFFA9D546FF40FB4663308B53.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procaccini	<div><p>THE NAME CAULERPA TAXIFOLIA VAR. DISTICHOPHYLLA</p><p>Caulerpa taxifolia var. distichophylla can be distinguished from C. taxifolia by the consistent fragility, shorter length and narrower width of all parts of the thallus (fronds, stolons and pinnules) under all conditions of settlement. Another diagnostic feature is the density of rhizoid pillars per unit length of stolon (Jongma et al. 2013). Caulerpa taxifolia var. distichophylla exhibits a high density and thin diameter of rhizoid pillars, whereas C. taxifolia var. distichophylla shows much thicker pillars at a lower density in C. taxifolia (one each 15 to 20 mm of stolon, Meinesz et al. 1995).</p><p>In the Bay of Villefranche, the ecological characteristics of the sites where the two introduced taxa are found in the Mediterranean are identical. On 30 June 2025, thalli of C. taxifolia and C. distichophylla were observed at the same depths and on the same substrate, separated by only 50 m. This excludes morphological variation induced by local conditions (Fig. 5).</p><p>These two taxa originate from geographically distant regions of Australia: the invasive strain of C. taxifolia is found near Brisbane on the east coast, while C. distichophylla is found near Fremantle on the west coast. Additional records include the Torres Strait, northern Australia (Jongma et al. 2013), and another from Ningaloo Reef south to Cape Naturaliste, approximately 1000 km north of Perth (Belton et al. 2019). Despite now occurring side by side in the Mediterranean, the two taxa remain clearly and consistently distinct morphologically (Fig. 4).</p><p>The morphological and biogeographical distinctions are robust and reflect stable, heritable differences from C. taxifolia (Jongma et al. 2013) .</p><p>Since 1990, the large-scale invasion of parts of the Mediterranean by C. taxifolia and C. cylindracea has resulted in several hundred papers being published on the genus Caulerpa (Silva 2003) .</p><p>Genetic analyses have been widely used to distinguish or group taxa of this highly polymorphic genus, which currently includes nearly 106 specific names and approximately 300 infraspecific epithets, and incorporates the concept of ‘ecads’ (i.e., morphological forms shaped by environmental conditions) (Guiry &amp; Guiry 2025). The invasion of the Mediterranean between 1984 and 2004 by C. taxifolia initially confused with a form of C. mexicana from the Red Sea (Chisholm et al. 1995; Meinesz &amp; Boudouresque 1996) prompted numerous genetic studies, some of which were contradictory. The conclusions of these studies did not always align with prevailing taxonomic interpretations.</p><p>The case of the invasive species C. cylindracea in the Mediterranean Sea illustrates these taxonomic shifts. Initially reported as Caulerpa racemosa (Forsskål) J. Agardh, when first recorded in Libya (Nizamuddin 1991), later referred to as Caulerpa racemosa var. occidentalis (J. Agardh) BØrgesen, (Verlaque et al. 2000), then as Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman &amp; Boudouresque, (Verlaque et al. 2003), and ultimately reinstated at the species level as C. cylindracea Sonder (Belton et al. 2014) .</p><p>Current genetic analyses suggest that C. taxifolia and C. taxifolia var. distichophylla are very closely related. Based on a single C. distichophylla specimen from the Perth region and chloroplast tufA sequence analysis, Famà et al. (2002a, b) identified C. distichophylla as the sister taxon of C. taxifolia, with a sequence divergence of only 0.24%, which is slightly higher than the intraspecific divergence observed within C. taxifolia (0.2%). The authors suggested that the two taxa might represent morphotypes of a single species but emphasised that unequivocal conspecific status would require molecular analyses of more variable genetic regions and additional specimens of C. distichophylla from the Indian Ocean where the taxon appears to be confined (Silva 2003). Subsequently, Jongma et al. (2013) found no statistically significant differences from C. taxifolia when using tufA, rDNA ITS and chloroplast 16S rDNA intron-2 sequences from two additional Australian specimens of C. taxifolia var. distichophylla . Belton et al. (2019) detected a single nucleotide difference between C. taxifolia and C. taxifolia var. distichophylla . This formed a distinct cluster within the C. taxifolia lineage in tufA alignments. However, this separation was not supported by the Generalized Mixed Yule Coalescent model.</p><p>According to Zubia et al. (2019), no complete Caulerpa nuclear genome has yet been published. Complete chloroplast genomes are available for only four species (none of which belong to the C. taxifolia-C. distichophylla complex), and a complete mitochondrial genome has been sequenced only for C. lentillifera J. Agardh, representing three subgenera.</p><p>Future genetic investigations on the genus Caulerpa, should take into account key morphological and structural characteristics: 1) the thallus is coenocytic, consisting of a single siphon, rather than a classic multicellular structure (thus its architecture - morphology is not composed of joined cells); 2) the distribution of organelles within the siphon and their role in morphogenesis are poorly understood; 3) siphons host endosymbiotic bacteria whose functions are unclear (Liddle et al. 1998; Meusnier et al. 2001; Aires et al. 2015; Zubia et al. 2019); and 4) the influence of ploidy level and genome size on Caulerpa morphology and invasive behaviour is largely unexplored (Varela-Álvarez et al. 2012; 2015).</p></div>	https://treatment.plazi.org/id/DB1087FCFFA9D546FF40FB4663308B53	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Meinesz, Alexandre;Meinesz, Coralie	Meinesz, Alexandre, Meinesz, Coralie (2026): Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procaccini, a new invasive species on the French Mediterranean coast. Cryptogamie, Algologie 47 (3): 33-46, DOI: 10.5252/cryptogamie-algologie2026v47a3, URL: https://doi.org/10.5252/cryptogamie-algologie2026v47a3
