## 4 Discussion  
The description of the strains investigated in this study was particularly tricky and complicated since neither asexual nor sexual reproductive structures developed in axenic conditions. As a consequence, it was not possible to describe the range of diagnostic traits amongst these newly identified lineages. To better characterize these fungi, we tried to mimic the saline environment by using a culture medium supplemented with seawater, since it is well known that only this method supports a measurable growth of vegetative mycelium [33]. The family Halospaheriaceae, to whom the genus _Corollospora_ belongs, includes the largest number of marine lignicolous species. It was thus realistic to induce sporulation by placing wood and cork specimens on the colony surface prior to transfer them into seawater. Despite wood colonization, sporulation did not occur, whereas chlamdospores were abundantly produced. Likewise, strains of _Corollospora_ sp. isolated from intertidal decayed wood of mangrove trees and driftwood in Saudi Arabia did not develop reproductive structures but only chlamdospores that were much bigger and not comparable to those observed in this study [30]. It must be considered that strictly vegetative growth with no sporulation is a common feature of marine fungi [46; 47; 48] that are likely to rely on their dispersion to hyphal fragments and/or chlamdospores. Most probably, a necessary requisite for fungi to develop reproductive structures is the occurrence of those environmental conditions these organisms are adapted to (e.g., high salinity, low temperature, high pressure, wet-dry cycles, etc.). The phylogenetic analysis based on ribosomal genes (nrITS, nrLSU, nrSU) and RPB1, shows a clear distance between the strains under investigation and the other species of _Corollospora_, _Corollospora martima_ being the closest one. This new and strongly supported clade may include one or more novel species. Hypothetically, the tree highlights the presence of three clusters that include: (i) MUT 1954 and MUT 1961; (ii) MUT 1938, MUT 5040, MUT 5049 and MUT 5082; (iii) MUT 1587, MUT 1950, and MUT 5048 (Figure 1). Bearing in mind the conclusion drawn by [PERSON] et al. [15] that indicated the need of sequencing more genetic markers to clarify the relations among the species of the genus _Corollospora_, a dataset focused on this new group, together with _C. martima_, was built with the addition of three more protein-coding genes, namely RPB2, TEF-1\(\alpha\) and \(\beta\)-TUB (Figure 2). From one side, this strongly supported tree points out once more the distance from _C. martima_, strengthening the idea that we are dealing with a new species. It is  
Figure 4: Growth rate on MEASW of the strains investigated over 28 days. The symbol indicates the isolation substrate (asterisk: driftwood; full circle: oil spill; vertical line: leaves of _Posidonia ocunica_); the color indicates the position in the phylogenetic tree (red: Clade 1, Subclade 1a; green: Clade 1, Subclade 1b; purple: Clade 1; blue: Clade 2). undeniably complicated to define a fungal species, and _Corollospora mediterranea_ was here established following the recommendations outlined by [PERSON] and [PERSON] [49], who, dealing with the issue of the species boundaries and identification of new taxa, pointed out a number of key elements to follow. Notably, all the ITS sequences (including 5.8S) analyzed are longer than the minimum 450 base pairs required and display a percentage of identity with the closest relative \(C\). _maritima_ < 95%. In addition, as recommended, the strongly supported phylogenetic tree includes the minimum number (4-5) of closely related taxa of the same genus (Figure 1). A thorough inspection of the tree shown in Figure 2 reveals the presence of two clusters: the former (Clade 1) consists of MUT 1950 and two subclusters (MUT 5040, MUT 5048 and MUT 5082; MUT 1587, MUT 1938, MUT 5049), the latter (Clade 2) includes MUT 1954 and MUT 1961.