Created 16/03/2017
16 Mar
2017

Both the nature of species and the criteria used to define them have been intensely debated. This is particularly true for recently diverged species and in taxonomic groups that are morphologically simple, such as many algae. Recently, a new line of thinking was put forth among biologists whereby species are considered as scientific hypotheses (species hypotheses) and species delineation is a process of refutation based on the acquisition of new evidence. This approach was developed by Alejandro Montecinos (Montecinos et al. 2017) during his “co-tutelle” thesis within the framework of French-Chilean international lab (UMI CNRS UPMC) to investigate the difficult taxonomic history of the genus Ectocarpus.

We ended up recognizing 15 cryptic species within the Ectocarpus subgroup siliculosi using three independent species delimitation approaches on a sampling of 729 Ectocarpus specimens collected mainly along the European and Chilean coasts. The 15 species showed different patterns of geographic distribution, varying from rare species with narrow ranges to common cosmopolitan species (E. siliculosus and E. crouaniorum). Our results demonstrated that the sequenced genome Ectocarpus strain, actually used as model species for brown algae and previously recognized as E. siliculosus, is in reality a rare unnamed species only present in Peru and the Northern coast of Chile. Another interesting observation is that several of the different cryptic species have been observed to occupy different spatio-temporal ecological niches related to different tide levels and/or host specificity. Finally, our analyses suggest the existence of incomplete lineage sorting or introgression between five of these 15 recently diverging lineages and the possible existence of different levels of reproductive barriers within this species complex. All these results open a very interesting field of research deciphering the process of evolution and diversification in this group using the tools available from the model organism for genomics and genetics of the brown macroalgae.

A highlight was published by Frederik Leliaert and Olivier De Clerck in volume 53, Issue 1, of Journal of Phycology on the paper published in the same volume by Alejandro Montecinos and collaborators.

 

Fig. Leliaert et De Clerck (2017). Ectocarpus sp. NZKU 1–3 (CCAP 1310/56) et arbre phylogénétique cox1 des Ectocarpus du sous groupe siliculosi montrant les 15 espèce délimitées sur la base des des marqueursmoléculaires par Montecinos et al (2017)

Figure from Leliaert and De Clerck[1] (2017). Ectocarpus sp. strain NZKU 1–3 (CCAP 1310/56) in culture (photo by Olivier De Clerck), and cox1 phylogenetic tree of the Ectocarpus sub- group siliculosi showing the 15 DNA-delimited species by Montecinos[2] et al. (2017).

Références

[1] Leliaert F, De Clerck O (2017) Refining species boundaries in algae. Journal of Phycology 53, 12-16.

[2] Montecinos AE, Couceiro L, Peters AF, et al. (2017) Species delimitation and phylogeographic analyses in the Ectocarpus subgroup siliculosi (Ectocarpales, Phaeophyceae). Journal of Phycology 53, 17-31.