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Caulerpa J.V. Lamouroux is a genus of green macroalgae belonging to the family Caulerpaceae in the order Bryopsidales. The genus comprises 104 currently accepted species, of which 51 have been recorded from Pacific Islands. Among these islands, French Polynesia is found in the middle of the South Pacific Ocean and includes five archipelagos (i.e., the Austral, Gambier, Marquesas, Society, and Tuamotu Islands) where seaweed inventories have reported a total of 16 Caulerpa species so far based on morphology. Here, based on a sampling covering the five archipelagos of French Polynesia, we attempt to (i) verify the taxonomy of Caulerpa species present in these regions based on phylogeny, (ii) describe in more detail the specific diversity between the five archipelagos, and (iii) provide a morphological identification tool for these species. We successfully obtained 134 new tufA sequences for phylogenetic analyses, which corresponded to 13 species. We propose to resurrect C. pickeringii Harvey & Bailey for representatives of C. webbiana var. pickeringii and classify it in the Caulerpa subgenus Araucarioideae. We also transfer C. seuratii to C. pickeringii based on genetic results. A new morphological identification key is provided as well as an updated distribution of Caulerpa species across French Polynesia. [ABSTRACT FROM AUTHOR]

Avrainvillea is a green macroalgal genus of the family Dichotomosiphonaceae (order Bryopsidales). Many species have been morphologically described, but few studies have addressed the genetic diversity of this genus. Based on a rich collection of specimens from the tropical Western Atlantic, Indian and Pacific Oceans, we aimed to (1) reassess Avrainvillea species diversity through species delimitation analyses, (2) update their distribution ranges, (3) reconstruct the species phylogenetic relationships, based on a concatenated multilocus matrix (tufA, rbcL and 18S rDNA) and (4) revise their taxonomy and describe new species where necessary. Our species delimitation approach highlighted 23 secondary species hypotheses in our collection, including nine known and currently accepted species, four species complexes (A. amadelpha, A. lacerata, A. erecta-obscura and A. mazei-nigricans), and eight new species for which we provide descriptions: A. laciniata (Papua New Guinea), A. minima and A. pyrochroma (Madagascar), A. mollis and A. kanakiensis (New Caledonia), A. pavonina (Fiji), A. spongiosa (Pacific) and A. corticata (Indo-Pacific). We also propose the resurrection of A. gracillima Børgesen, the reinstatement of Avrainvillea lacerata var. robustior A.Gepp & E.S.Gepp, and the synonymy of A. rotumensis A.D.R.N'Yeurt, D.S.Littler & Littler with A. pacifica A.Gepp & E.S.Gepp. We complemented the taxonomic work by providing a contemporary dichotomous key for morphological identification of all extant species. Our multilocus phylogeny included 25 species of Dichotomosiphonaceae and recovered Avrainvillea as a polyphyletic group, divided into three distinct clades, with Cladocephalus luteofuscus positioned within the group. The species determined using the species delimitation approach were all monophyletic and 19 of them were highly supported. For the first time, this study also provided genetic sequences for A. asarifolia, A. clavatiramea, A. digitata, A. elliottii, A. fulva, A. gracillima, A. geppiorum, A. pacifica and A. obscura. • Avrainvillea is not monophyletic. • Reassessment of Avrainvillea species diversity delimited 23 secondary species hypotheses. • Eight new species of Avrainvillea were discovered in the Indo-Pacific. [ABSTRACT FROM AUTHOR]

Ulva is a green macroalgal genus with rich species diversity and worldwide distribution. While current knowledge on Ulva diversity focuses on temperate regions, genetic and morphological data in tropical and subtropical areas are scarce and the species richness is not clearly defined. The genus is known for its bloom-forming ability that can induce green tides leading to severe environmental and economic damage. In the last two decades, several important blooms of Ulva spp. have occurred in New Caledonia, requiring further investigations to identify the species involved. As knowledge of New Caledonian Ulva diversity is limited, an update to the Ulva spp. inventory in the area is essential. Based on Ulva specimens collected throughout New Caledonia (Grande Terre, Isle of Pines and Loyalty Islands), we (1) reassessed species diversity using species delimitation methods, (2) analysed morpho-anatomical characters to identify species and/or enrich their diagnosis, and (3) reconstructed a multilocus phylogeny (ITS, rbcL, tufA) of the genus. We found 21 secondary species hypotheses (SSHs) among our dataset, from which five were successfully assigned to U. lactuca, U. ohnoi, U. tepida, U. meridionalis and U. taeniata. Ten SSHs were defined as new species for which we provided taxonomic description, and six other SSHs were singletons that will need to be data-enriched for better interpretation. Our concatenated multilocus matrix included 61 Ulva species. Of these, 15 species were found in New Caledonia and were moderately to strongly supported. Among the Ulva species found in New Caledonia, seven are known to be bloom-forming which highlights the need for strict regulation and regular monitoring of water quality, particularly in areas exposed to strong nutrient input where these species can form green tides. Ulva diversity in New Caledonia was reassessed with 15 species highlighted. Ten new species have been discovered in New Caledonia. Indigenous species caused recent green tides in New Caledonia. [ABSTRACT FROM AUTHOR]

Udoteaceae is a morphologically diverse family of the order Bryopsidales. Despite being very widespread geographically, this family is little known as compared with the closely related Halimedaceae or Caulerpaceae. Using the most extensive Udoteaceae collection to date and a multilocus genetic data set (tufA, rbcL, and 18S rDNA), we reassessed the species diversity of the family, as well as the phylogenetic relationships, the diagnostic morphoanatomical characters, and evolutionary history of its genera, toward a proposed taxonomic revision. Our approach included a combination of molecular and morphological criteria, including species delimitation methods, phylogenetic reconstruction, and mapping of trait evolution. We successfully delimited 62 species hypotheses, of which 29 were assigned (existing) species names and 13 represent putative new species. Our results also led us to revise the genera Udotea s.s., Rhipidosiphon s.s., and Chlorodesmis s.s., to validate the genus Rhipidodesmis, and to propose three new genera: Glaukea gen. nov., Ventalia gen. nov., and Udoteopsis gen. nov. We also identified two large species complexes, which we refer to as the "Penicillus–Rhipidosiphon–Rhipocephalus–Udotea complex" and the "Poropsis–Penicillus–Rhipidodesmis complex". Using a time‐calibrated phylogeny, we estimated the origin of the family Udoteaceae at Late Triassic (ca. 216 Ma), whereas most of the genera originated during Paleogene. Our morphological inference results indicated that the thallus of the Udoteaceae ancestor was likely entirely corticated and calcified, composed of a creeping axis with a multisiphonous stipe and a pluristromatic flabellate frond. The frond shape, cortication, and calcification are still symplesiomorphies for most extant Udoteaceae genera and represent useful diagnostic characters. [ABSTRACT FROM AUTHOR]

Genera and species of the tribes Rhipileae and Rhipiliopsideae are abundant in most coral reef ecosystems worldwide. However, the group has been largely overlooked, and very little genetic data is available to accurately assess its diversity, phylogenetic relationships, and geographic distribution. Our study provided an in‐depth reassessment of tribes Rhipileae and Rhipiliopsideae based on a species‐rich dataset and the combination of molecular species delimitation, multilocus phylogenetic analyses (tufA, rbcL, and 18S rDNA), and morpho‐anatomic observations. Our results revealed an unexpected diversity of 38 morphologically validated species hypotheses, including 20 new species, two of which are described in this paper and one resurrected species (Rhipilia diaphana). Based on our phylogenetic results we proposed to redefine the genera Rhipilia and Rhipiliopsis and described two new genera, Kraftalia gen. nov. (Rhipileae) and Rhipiliospina gen. nov. (Rhipiliopsideae). Finally, we validated Rhipiliella Kraft and included it in the tribe Rhipileae. Although Rhipilia and Rhipiliopsis have a pantropical distribution, none of the species studied here appeared cosmopolitan; instead, they have restricted distributions. [ABSTRACT FROM AUTHOR]

The Udoteaceae family (Bryopsidales, Chlorophyta) is known to be highly diverse morphologically in the Caribbean region, but only few studies have studied its genetic diversity. Using an integrative taxonomic approach, this study aimed at (1) exploring the Udoteaceae species diversity using a combination of five DNA-based species delimitation methods and morpho-anatomical data for confirmation; (2) estimating the discriminatory power of traditional diagnostic characters using a morphology-based clustering method and statistical analyses focused on the genus Udotea ; and (3) reconstructing the phylogeny of the family based on a multilocus analysis ( tuf A , rbc L, 18S rDNA). Our results revealed strong congruence between species hypotheses across delimitation methods and markers. Morpho-anatomical characters proved essential to validate these hypotheses, to assign species names and to unveil new species. Morphological analyses led to relevant results for accurately discriminating Udotea morphospecies. Siphon features and cortication were key characters to define supra-specific groups and to revise the taxonomy of the genus Udotea . Phylogenetic analyses confirmed the polyphyly of Udotea, Rhipocephalus and Penicillus , which led us to propose a revised definition of Udotea sensu stricto based on both genetic and morphological data. Finally, our study emphasizes the importance of combining genetic and morphological data for the taxonomic revision of the Udoteaceae, but stresses the need of including more taxa from other geographical regions to better resolve taxonomic issues. [ABSTRACT FROM AUTHOR]

[Display omitted] • Most of Udoteaceae species are restricted to a single ocean basin. • The Udoteaceae likely originated in Western Tethys during the Triassic period. • The Central Indo-Pacific, Western Indian Ocean, and the Greater Caribbean are the 3 centers of Udoteaceae species diversity. • Different drivers have likely played a role in shaping these diversity centers. • The Central Indo-Pacific is a center of origin, accumulation, and overlap. There is a growing interest in elucidating the biogeographical processes underlying biodiversity patterns of seaweeds, with recent studies largely focusing on red and brown macroalgae. This study focuses on the siphonous green algal family Udoteaceae, which is diverse and globally distributed in tropical to warm-temperate seas, and includes species that form important components of tropical reefs. We explored the historical processes that have shaped current biodiversity patterns in the family by analyzing a comprehensive dataset of 568 specimens sampled across its geographical range, and including 45 species, corresponding to 59% of the known diversity. Historical biogeographical analysis was based on a three-locus time-calibrated phylogeny, and probabilistic modeling of geographical range evolution. Many species were found to have restricted ranges, indicative of low dispersal capacity. Our analysis points toward a Western Tethys origin and early diversification of the Udoteaceae in the Triassic period. Three centers of diversity were identified, which are, in order of highest species richness, the Central Indo-Pacific, the Western Indian Ocean, and the Greater Caribbean. Different drivers have likely played a role in shaping these diversity centres. Species richness in the Central Indo-Pacific likely resulted from speciation within the region, as well as recolonization from neighbouring regions, and overlap of some wider ranged species, corroborating the "biodiversity feedback" model. Species richness in the Western Indian Ocean can be explained by ancient and more recent diversification within the region, and dispersal from the Central Indo-Pacific. The Greater Caribbean region was colonized more recently, followed by diversification within the region. [ABSTRACT FROM AUTHOR]

To assess the photophysiological capacity of the recently described Ulva batuffolosa to form blooms in coral reefs, we monitored its biomass and photophysiological capacity with pulse amplitude modulated (PAM) fluorometry over a year period on a coastal barrier reef in New Caledonia, along with temperature and light. Effective and maximum quantum efficiencies of the photosystem II measured on this Ulva species indicated that the algae was in a "good health" all over the year with high quantum efficiencies under either light (Fq'/Fm') or dark incubated conditions and (Fv/Fm). Photo-acclimation and -regulation status used by this Ulva sp. were driven by seasons (i.e., light and temperature) in the lagoon. Although photo-inhibition was an evidence during the warm period, U. batuffolosa was overall well adapted to tolerate the range of irradiance and temperature that characterized the lagoon over the year, which suggests that photosynthesis is not an impediment to green tides by this species. • Photo-acclimation and regulation status of Ulva batuffolosa were modulated by season. • Ulva batuffolosa was well adapted to support and tolerate high irradiance. • The combination of elevated temperatures and light damaged its physiology. [ABSTRACT FROM AUTHOR]