Origin, intra-generic relationships and biogeography
Haploginglymus is endemic to the Iberian Peninsula, where it displays an almost generalised distribution in fresh subterranean waters and is the only niphargid known unless for two disjunct areas on both edges of the Pyrenees, where Niphargus also occurs (Notenboom, 1990). In those areas, the orography is less pronounced than at the central Pyrenean sector, to the point of enabling the local trans-Pyrenean colonization by Niphargus. The latter genus is broadly distributed across the rest of Europe and the Middle East (Esmaeili-Rineh et al., 2015), and seems to have colonised the two foregoing Spanish regions quite recently, apparently after the establishment of Haploginglymus in Iberia. Thus, at least three of the four Niphargus species recorded in Catalonia display a trans-Pyrenean distribution (Karaman, 2015a; b), whereas those from the Basque Country conform a derived monophyletic group within the niphargid tree that appears to be unrelated to Haploginglymus (v. Fig. 2). Thus, the rise of the Pyrenees with its current structural organisation already at the Paleocene/Eocene boundary, 55-47 Myr ago (Vergés et al., 2002) might have played a major role in the differentiation of Haploginglymus from the rest of niphargids, with this age representing a terminus post quem for its origin (Fig. 1).
The nine Haploginglymus samples included in our analysis conform two main monophyletic groups (Figs 2; 3; nodes B and C). One (node B) appears associated to the River Ebro and its tributaries, and comprises the three species recorded at River Matarranya, of which only H. morenoi has been formally described thus far. The second group (node C) is distributed across the southern half of the Iberian Peninsula and comprises the rest of taxa. The genetic divergence among these Haploginglymus lineages is high, as deduced from the observed values of uncorrected pairwise cox1 p-distances (Table 4). With the caveat that DNA sequences from representatives of other parts of the northern sector of the Peninsula are lacking, it is feasible to relate this primary subdivision of the genus to the uplift during the Tertiary Alpine orogeny of two intra-Peninsular mountain ranges: The Central System (that separates the Duero and Tajo river basins) and the Iberian System (that separates the Ebro river basin from the rest of the Peninsula) (v. Fig. 1).