Foxed intra- and interspecific differentiation in &lt;em&gt;Leptogorgia&lt;/em&gt; (Octocorallia: Gorgoniidae). A description of a new species based on multiple sources of evidence

M Mar Soler-Hurtado,Pablo J López-González,César Megina,Annie Machordom

doi:10.3989/scimar.04509.01c

Abstract

The challenges of delimiting and identifying marine invertebrate species impede estimations of true biodiversity. This is particularly true in the case of gorgonian diversity, in which only classical morphological characters (e.g. branching pattern, size and colouration of the colony and sclerites, etc.), which can be homoplastic and continuous, have been used. In this study, using an integrative taxonomic approach, we analysed two morphs initially considered as two eco-typical variants of Leptogorgia alba Duchassaing and Michelotti, 1864, living sympatrically in the littoral area of Ecuador. We explored the use of classical morphological and morphometric characters to delimit species in combination with the analyses of molecular markers (mtMutS, CoxII-Igr-CoxI, ITSs, and 28S rRNA) to infer phylogenetic relationships. Based on our results, two species should be considered, L. alba and a new species, L. manabiensis n. sp., which showed distinguishing morphological features that cannot be attributed to phenotypic plasticity. Both species also showed significant differences in morphometric, non-correlated characters in all size classes. The phylogenetic analyses showed a polyphyletic L. alba - L. manabiensis n. sp. species complex, and ancestral polymorphism and incomplete lineage sorting as possible evolutionary processes leading to this pattern. In conclusion, the combination of morphological and morphometric evidences provides the best support for the identification and delimitation of these challenging species. In addition, molecular analyses, mainly supported by nuclear markers, allow fundamental aspects of the evolutionary history of these organisms to be discerned.

Highlights

Several studies have highlighted the difficulties of identifying marine species, especially invertebrates, using only morphological characters (Calvo et al 2009, López-González et al 2015, Alfaya et al 2015), which can lead to an underestimation of biodiversity, and possibly adversely impact the conservation of endangered species or those with restricted distributions
In the PCR protocol column, we indicate annealing temperature, time in seconds for the denaturation, annealing and elongation, respectively, and the number of cycles for each gene, independent of the primer combination used. *PCRs were performed with the following primer combinations: Cox: 1+3, or 1+4 and 2+3; mtMutS: 5+6; ITSs: 7+8; 28S rRNA: 9+10 or 9+11
Based on the evidence provided by the study of the differentiation of two Leptogorgia morphs, supported mainly by morphological and morphometric analyses, and framed by their evolutionary history, here we describe a new species within the family Gorgoniidae

Summary

Introduction

Several studies have highlighted the difficulties of identifying marine species, especially invertebrates, using only morphological characters (Calvo et al 2009, López-González et al 2015, Alfaya et al 2015), which can lead to an underestimation of biodiversity, and possibly adversely impact the conservation of endangered species or those with restricted distributions (see e.g. Rocha-Olivares et al 2001, Dincă et al 2011, Eberle et al 2016).Understanding species boundaries in corals, in octocorals, is a challenge for several fields of study, including taxonomy, evolutionary biology, life history and ecology (Vermeij et al 2007, Stefani et al 2008, Gori et al 2012). Morphometric analyses have shown that the observed overlapping range for some continuous characters in octocorals is widely attributed to an apparent phenotypic plasticity, making consistent taxonomic units difficult to establish (Weinbauer and Branko 1995, Sánchez 2009). Evolutionary processes, such as interspecific hybridization, explosive radiation and incomplete lineage sorting (Hatta et al 1999, Vollmer and Palumbi 2004, Forsman et al 2010), may contribute to the difficulty of distinguishing closely related species. Anthozoan mitochondrial genomes, especially those of octocorals, evolve 10 to 100 times more slowly than those of other metazoans (France and Hoover 2002, McFadden et al 2004, Hellberg 2006), and possible incongruences between mitochondrial and nuclear phylogenetic reconstructions may be attributed to hybridization

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Conclusion