[§ 1] The aim of this study is to determine the population structure of two coralligenous species by studying the intraspecific diversity of the populations and their connectivity in the Mediterranean Sea.

[§ 2] In order to study the connectivity of populations the analysis of the dissimilarity of genetic markers will be performed. Samples will be compared to reveal the population structure within each site^?, and also to unveil if a topographic factor (i.e. slope, orientation or rugosity) would permit a partial explication of this structure. The sampling is equally performed on different ecological profiles in each site in order to know the structure of the population according to the profile^? and thus the species ecology. This implies the possibility to discover cryptic species^?. For this reason, the barcoding method of Cytochrome c oxidase subunit I or COI (or eventually other alternative or complementary markers) would permit to detect the possible presence of cryptic species within the studied ones.

a. Species selection
[§ 3] The study will be addressed to two ubiquitous species in the the Mediterrannean Sea, widespread in most of coralligenous facies and easly indentifiable in situ : the erect and bush-shaped bryozoan Myriapora truncata, and one of the main bioconstructing calcificate algae, Lithophyllum stictaeforme/cabiochiae.

Myriapora truncata (Pallas, 1766)
[§ 4] Myriapora truncata (Figure 1) is an erect, brunching bryozoan, usually bright orange colored. The colony is characterised by dichotomic ramifications ; brunches show round and constant sections, and truncated extremities. Sciaphilic^? species, lives on on hard substrates from about 10 m to more than 40 m depth.

Figure 1 : Myriapora truncata (Pallas, 1766)

[§ 5] Despite its reproduction pattern (a lecitotrophic and brooded larvae with low dispersion potential), it is widespread in all the Mediterranean sea and in some areas of the eastern Atlantic ocean. Nevertheless, it is still unknown whether it is always the same species, or a species complex containing several cryptic, even possibly sympatric, species, as known for other bryozoans. For this reason, it is interesting to verify with genetic markers the possibly presence of cryptic species or local adaptation depending on the geography (basins, regions), ecology (comparing the different “profiles” sensu CIGESMED of a same locality^?) and the population structure (quantification of gene flux, construction of matrices of connectivity).

Lithophyllum stictaeforme/cabiochiae (Areschoug) Hauck / (Boudouresque & Verlaque) Athanasiadis
[§ 6] Since unpublished data (Line Le Gall, personal communication) suggest that Lithophyllum cabiochae is a species complex containing at least 7 different species, and considering that L. stictaeforme and L. cabiochiae are quite difficult distinguish in situ, we will address to those species as “Lithophyllum stictaeforme/cabiochiae” complex (Figure 2).

Figure 1 : Lithophyllum stictaeforme/cabiochiae (Areschoug) Hauck / (Boudouresque & Verlaque) Athanasiadis

[§ 7] The Lithophyllum stictaeforme/cabiochiae Athanasiadis complex is, among other red calcareous algae of the order Corallinales, one of the main coralligenous builders (Feldmann, 1937 ; Laborel, 1961 ; Laubier, 1966 ; Hong, 1982 ; Sartoretto, 1996 ; Athanasiadis,1999 ;Ballesteros, 2006). The thalli of the algae are completely calcified, showing a stony aspect, and they can be pink (L.chabiocae) or purple (L. stictaeforme) colored. Thin rounded, undulating edged and often overlapping leafs spread from a central part fixed to the substrate.
Sciaphilic species, common from the surface (shaded areas) to about 40 m depth.
The taxonomy of this algae is very difficult and the valid scientific name of the species is constantly changing (Table 1).