Phylogenetic relationships within Aglaopheniidae (Cnidaria, Hydrozoa) reveal unexpected generic diversity

Abstract

International audienceMorphology can be misleading in the representation of phylogenetic relationships, especially in simple organisms like cnidarians and particularly in hydrozoans. These suspension feeders are widely distributed in many marine ecosystems, and the family Aglaopheniidae Marktanner-Turneretscher, 1890 is among the most diverse and visible, especially on tropical coral reefs. The taxonomy of this family is based on morphological characters with emphasis on reproductive structures for the identification of genera. This study is the most comprehensive molecular phylogeny of the Aglaopheniidae to date, including six genera and 38 species, of which 13 were investigated for the first time and sampled on tropical coral reefs throughout the Indo-Pacific region. For newly sampled individuals, we sequenced the 16S rRNA, the nuclear locus comprising the complete ITS1-5.8S rRNA gene-ITS2 and the first intron of the calmodulin nuclear gene. Phylogenetic analyses of the data revealed and confirmed a general polyphyly, or doubtful monophyly, of all sampled genera in tropical regions based on both the mitochondrial and nuclear markers. Our results revealed that several morphological characters used today are unsuited to resolve phylogenetic relationships between species and genera, as well as the high phyletic diversity within this family. Future revision of the classification of this family will require extensive geographic sampling and the use of an integrative approach

Population differentiation or species formation across the Indian and the Pacific Oceans? An example from the brooding marine hydrozoan Macrorhynchia phoenicea

“…Aglaopheniids’ genus‐level taxonomy is mainly based on the morphology of the reproductive structures (Bouillon et al., ), but as many other characters, life cycles of hydrozoans are subject to convergent or reversible evolution across their phylogeny (Collins, ; Leclère et al., , ; Marques & Collins, ; Miglietta & Cunningham, ) and the diversity of Aglaopheniidae is still under assessment (Moura et al . ; Postaire et al., , ).…”

“…They are among the first fixed organisms to colonize new habitats and provide shelter to a wide variety of invertebrate and microbial taxa (Boero, ; Gili & Hughes, ). Despite their ecological importance and phyletic diversity, this clade is still understudied: its taxonomy is complicated and confused due to the paucity of diagnostic morphological characters, resulting in several systematic revisions and alpha‐diversity assessments during the past two decades (Bouillon & Boero, ; Bouillon et al., ; Cartwright & Nawrocki, ; Collins, ; Marques & Collins, ; Postaire et al ., ; Postaire et al ., ; Ronowicz et al., ). One of their key features is the variety of life history traits and reproductive strategies, notably including a medusa stage of variable duration depending on the taxon (Boero, Bouillon, & Piraino, ; Boero et al .…”

“…Despite their ecological importance and phyletic diversity, this clade is still understudied: its taxonomy is complicated and confused due to the paucity of diagnostic morphological characters, resulting in several systematic revisions and alpha-diversity assessments during the past two decades (Bouillon & Boero, 2000;Bouillon et al, 2006;Cartwright & Nawrocki, 2010;Collins, 2002;Marques & Collins, 2004;Postaire et al, 2016a;Postaire et al, 2016b;Ronowicz et al, 2017).…”

“…The Aglaopheniidae Marktanner-Turneretscher, 1890 is one of the most species-rich families with more than 250 extant species found in all marine ecosystems (Millard, 1975); they are characterized by the absence of a medusa stage and by the incubation of larvae in dedicated structures, even if some species reacquired a temporally reduced medusa-like stage during their evolution (Leclère et al, 2009;Leclère, Schuchert, & Manuel, 2007). Aglaopheniids' genus-level taxonomy is mainly based on the morphology of the reproductive structures (Bouillon et al, 2006), but as many other characters, life cycles of hydrozoans are subject to convergent or reversible evolution across their phylogeny (Collins, 2002;Leclère et al, 2007Leclère et al, , 2009Marques & Collins, 2004;Miglietta & Cunningham, 2012) and the diversity of Aglaopheniidae is still under assessment (Moura et al 2012;Postaire et al, 2016aPostaire et al, , 2016b.…”

One species for one island? Unexpected diversity and weak connectivity in a widely distributed tropical hydrozoan

“…The Aglaopheniidae family (Marktanner-Turneretscher, 1890) represents one of the largest, with over 250 valid species (Bouillon et al, 2006) and is particularly diversified in tropical marine ecosystems. The diversity of this family is still under assessment, as recent publications highlighted that morphological characters provide little clues to the evolutionary history and species richness of this taxon, presenting extensive cases of morphological convergence and low anagenesis (Leclère et al, 2007;Moura et al, 2012;Postaire et al, 2016a, b). Aglaopheniidae species generally do not have a medusa stage but brood their larvae in dedicated structures of the colony (named gonothecae; Millard, 1975) and planulae are released only when mature (Boero et al, 1992).…”