Molecular phylogenetic relationships reveal contrasting evolutionary patterns in Gorgoniidae (Octocorallia) in the Eastern Pacific

Abstract

The description and delimitation of species in an evolutionary framework is essential for understanding patterns of biodiversity and distribution, and in the assessment of conservation strategies for natural resources. This study seeks to clarify the evolutionary history and genetic variation within and between closely related octocoral species that are fundamental to benthic marine ecosystems for harbouring a high diversity of associated fauna. For our study system, we focused on members of the Gorgoniidae family in the Eastern Pacific, particularly of the Ecuadorian littoral, a less studied marine ecosystem. According to our results, the diagnosis of the genus Pacifigorgia is here amended to include species previously considered in the genus Leptogorgia. The genera Leptogorgia and Eugorgia are included within a single clade, and neither are recovered as monophyletic. In this case, according to the priority rule of the International Code of Zoological Nomenclature (ICZN), our proposal is to include the species considered in these two genera in Leptogorgia. In addition, we found evidence of interesting speciation patterns: morphological differentiation with no apparent genetic differentiation (in Pacifigorgia), and inconsistencies between mitochondrial and nuclear data that suggest a hybridisation phenomenon (in Leptogorgia). In the first case, recent radiation, ancient hybridisation, sympatric speciation, and in the second, reticulate evolution may have contributed to the evolutionary history of the studied taxa. Therefore, incongruences observed between morphological and molecular evidences in these octocorals, and in corals in general, may reveal the types of events/patterns that have influenced their evolution.

Two new endemic species of Gorgoniidae (Cnidaria, Anthozoa, Octocorallia) from Revillagigedo Archipelago, Mexico

“…Recent molecular phylogenetic evidence (nuclear and mitochondrial markers) of sea fans from the Eastern Tropical Pacific indicates that several species of Eugorgia and Leptogorgia from Ecuador are within a single genetic clade, and neither was recovered as monophyletic (Soler-Hurtado et al 2017). In addition, a world review of the genus Leptogorgia, based on mitogenomics, demonstrate that this genus is a polyphyletic group with at least four clades distributed in the Eastern Atlantic-Mediterranean Sea, South Africa, Western Atlantic, and Eastern Pacific (Poliseno et al 2017).…”

A review of gorgonian coral species (Cnidaria, Octocorallia, Alcyonacea) held in the Santa Barbara Museum of Natural History research collection: focus on species from Scleraxonia, Holaxonia, Calcaxonia – Part II: Species of Holaxonia, families Gorgoniidae and Plexauridae

“…Of note is that WoRMS Data Base (Cordeiro et al 2018b) does list E.aurantiaca and E.daniana as separate species, but that E.daniana has been accepted as Leptogorgiadaniana . Very few species of Leptogorgia ( L.ramulus Milne Edwards & Haime, 1857, is one of few) display the shorter branch lengths seen consistently in species of Eugorgia nor the irregular and pinnate branching of the Eugorgia , which are morphological characters; it is understood that this acceptance is based on the molecular work that was done by Soler-Hurtado et al (2017). Of note is the rationale for this genus change, with Soler-Hurtado et al (2017) noting the 1999 ICZN Principle of Priority (Article 23).…”

“…Very few species of Leptogorgia ( L.ramulus Milne Edwards & Haime, 1857, is one of few) display the shorter branch lengths seen consistently in species of Eugorgia nor the irregular and pinnate branching of the Eugorgia , which are morphological characters; it is understood that this acceptance is based on the molecular work that was done by Soler-Hurtado et al (2017). Of note is the rationale for this genus change, with Soler-Hurtado et al (2017) noting the 1999 ICZN Principle of Priority (Article 23). In the work of Olvera et al (2018), this species is listed as a species of Eugorgia and is not included in the list of Leptogorgia species that are discussed.…”

“…An additional piece of information regarding L.tricorata can be found in the work of Soler-Hurtado et al (2017). Based on molecular analysis, they have proposed that L.tricorata should now be considered a derived form in the genus Pacifigorgia Bayer, 1951 (see page 226, Soler-Hurtado et al 2017).…”

“…An additional piece of information regarding L.tricorata can be found in the work of Soler-Hurtado et al (2017). Based on molecular analysis, they have proposed that L.tricorata should now be considered a derived form in the genus Pacifigorgia Bayer, 1951 (see page 226, Soler-Hurtado et al 2017). Cordeiro et al (2018d) does not show this proposed emendation of the genus Pacifigorgia in the WoRMS Data Base; L.tricorata , however, is shown as an accepted species in the genus Leptogorgia .…”