Unio durieui, Deshayes, 1847

Araujo, Rafael, Buckley, David, Nagel, Karl-Otto, García-Jiménez, Ricardo & Machordom, Annie, 2018, Species boundaries, geographic distribution and evolutionary history of the Western Palaearctic freshwater mussels Unio (Bivalvia: Unionidae), Zoological Journal of the Linnean Society 182 (2), pp. 275-299 : 280

The U. durieui + U. gibbus lineage

This clade grouped the samples from the morphospecies U. durieui and U. gibbus as sister lineages ( Fig. 1 ). The U. durieui lineage only included samples from Tunisia and consisted of five different haplotypes among the specimens from the three rivers sampled. Distinct haplotypes were present in each river, but the most frequent haplotype was shared among specimens from the Ziatine and El Maaden rivers (Supporting Information, Fig. S1 ).

Morphologically, U. durieui specimens were elongated with an intermediate shape between U. mancus and U. pictorum , and probably impossible to distinguish in the absence of geographical information. There were also rounded morphotypes similar to U. gibbus , as in the case of El Maaden ( Khalloufi et al., 2011: fig. 5). This species was not found in Morocco but is present in Tunisia and Algeria to the east of the Moulouya River ( Fig. 2 ).

For the morphospecies U. gibbus , we obtained two clearly separated groups (genetic distance of 2.03%, Table 1 ): one representing haplotypes from the Iberian Peninsula (Barbate River) and Morocco, and another consisting of Tunisian haplotypes ( Fig. 2 ; Supporting Information, Fig. S2 ). These two subclades were consistently recovered as distinct species in the bGMYC and M-PTP analyses. From 16 to 22 substitutions separated the Spanish-Moroccan haplotypes from the Tunisian ones. Although the eastern haplotypes were more similar, none of the Spanish, Moroccan and Tunisian specimens shared haplotypes among the 10 detected.

This species had a rounded shape similar to Potomida , but clear diagnostic characters such as the lateral teeth, the umbonal sculpture and shell thickness differentiate the two taxa ( Araujo et al., 2009a: fig. 2).

Figures

Figure 1. Bayesian tree reconstruction based on the two mitochondrial genes analysed. Values on the branches indicate Bayesian posterior probabilities, ML and MP bootstrap values. Results from the species delimitation analyses are also shown in this figure (green: M-PTP with a Bayesian tree; red: M-PTP with an ML tree; blue: bGMYC analysis). Names for the currently recognized morphospecies are also indicated in the phylogenetic tree.

Figure 2. Schematic distribution of the Unio species in the Western Palaearctic. Points indicate the general vicinity of sampled localities. See Supporting Information, Table S1 for details.