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Caves are long-known examples of evolutionary replications where similar morphologies (troglomorphies) evolve independently as the result of strong natural selection of the extreme environment. Recently, this paradigm has been challenged based on observations that troglomorphies are inconsistent across taxa and different subterranean habitats. We investigated the degree of replicated phenotypic change in two independent cave invasions by the freshwater isopod Asellus aquaticus; the first in a sulphidic aquifer in Romania, the second in a sinking river in the Dinaric Karst in Slovenia. Both ancestral surface populations still live alongside the subterranean ones. Phylogenetic analyses show independence of the two colonization events, and microsatellite analysis shows no evidence of ongoing genetic exchange between surface and subterranean ecomorphs. The overall morphology has changed dramatically at both sites (50 of 62 morphometric traits). The amount of phenotypic change did not reflect differences in genetic diversity between the two ancestral populations. Multivariate analyses revealed divergent evolution in caves, not parallel or convergent as predicted by the current paradigm. Still, 18 traits changed in a parallel fashion, including eye and pigment loss and antennal elongation. These changes might be a consequence of darkness as the only common ecological feature, because Romanian caves are chemoautotrophic and rich in food, whereas Slovenian caves are not. Overall, these results show that morphologically alike surface populations can diverge after invading different subterranean habitats, and that only about one-third of all changing traits behave as troglomorphies in the traditional sense.

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The family Moitessieriidae includes minute dioecious gastropods exclusively inhabiting subterranean waters, including thermal ones. Only empty shells were collected in most species, the vast majority of them are described from their gross shell morphology alone. Several visits to a site are usually required to obtain at least some living individuals. High variability in shell morphology and the lack of diagnostic features, coupled with anticipated high levels of endemism, has resulted in a long list of nominal moitessierid species. Type specimens stored as empty shells omit unambiguous identification and delimitation of species boundaries. Due to inaccessibility of cave animals and consequent lack of material suitable for molecular analysis, the phylogenetic relationships, as well as the taxonomy of the family at genus/species level, are far from being understood. The anatomy of the family is also poorly known and provided only for a few taxa. The distinctness of the Moitessieriidae has sometimes been questioned, and their monophyly not proved. Twelve species of the Balkan Moitessieriidae are considered: two species of Paladilhiopsis, two species of Bythiospeum, six species of Iglica, Costellina turrita and Lanzaia bosnica. The shell morphology of each species, as well as the reproductive system of Paladilhiopsis and Iglica, were analysed. DNA sequences of nuclear histone H3, ribosomal 18S, ribosomal 28S and mitochondrial cytochrome oxidase subunit I (COI) were applied to infer phylogenetic relationships among the taxa. The sequences of Bythiospeum from GenBank have been used to infer relationships between Bythiospeum and Paladilhiopsis that were recently synonymized. Paladilhiopsis and Iglica are distinct, but closely related genera, as is the genus Bythiospeum, which does not occur in the Balkans. Its relationships with both former taxa remain unresolved. The Moitessieriidae are clearly distinct from all other families of the Truncatelloidea, however, their monophyly remains doubtful.

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Freshwater truncatelloidean gastropods include numerous minute cryptic species, displaying simple morphologies, all of which hampers their taxonomic research based on morphology. Phylogenetic relationships among all but one extant species of the genus Kerkia from five localities in Croatia and one in Slovenia were therefore analysed based on one mitochondrial (cytochrome c oxidase subunit I) and three nuclear markers (18S, 28S and H3). Kerkia kusceri (Bole, ), K. jadertina Kuščer, 1933, K. j. sinjana (Kuščer, 1933), and K. kareli Beran, Bodon et Cianfanelli, 2014, were collected from their type localities. Our analysis confirmed their distinctness, recovering two additional clades that may represent yet undescribed species from Croatia. Apart from Kerkia, Hauffenia media Bole, , H. subpiscinalis (Kuščer, 1932) and H. erythropomatia (Hauffen, 1856) from Slovenia were analysed. Their distinctness together with the rejection of the eligibility for separate genus Erythropomatiana for the latter species was proven. Interestingly, its sequence divergence exceeded all previous estimates for species‐level divergence within the Truncatelloidea, implying a species‐level separation both for the COI and for nuclear loci. High p‐distances for the COI/nuclear loci (0.128/0.027, respectively) confirmed also the uniqueness of both genera. A comparison of their COI sequences with the reference sequences of Alzoniella Giusti et Bodon, 1984, Avenionia Nicolas, 1882, Fissuria Boeters, 1981, and Agrafia Szarowska et Falniowski, 2011, has shown that Kerkia and Hauffenia are not sister clades. The most striking, however, was the apparent introgression of the ‘Hauffenia’ mtDNA type from central Slovenia (cave Babja luknja) into two Kerkia clades from central (Ljubač) and southern (Podgrađe) Croatia, that are located 210 km and 360 km away, respectively. The introduced ‘Hauffenia’ mtDNA type and the closest Hauffenia erythropomatia COI differed by 0.8%. Secondary loss of isolating mechanisms between phylogenetically distant organisms and the severe lack of information on distribution of these underground taxa were postulated as possible explanations of this interesting phenomenon.

Three Dinaric subgenera of cave shrimps from the genus Troglocaris s. l.: T. sg. Troglocaris Dormitzer, 1853 (=Troglocaris s. str.), T. sg. Spelaeocaris Matjasˇicˇ, 1956 and T. sg. Troglocaridella Babic´, 1922 comprise 12 currently known species and phylogenetic lineages. On the basis of the results of previous molecular studies and the extensive morphometric analysis, appropriateness of several former and the existence of some new metric descriptors are examined by multivariate statistical methods. In discriminant function analyses (DFA), all subgenera are distinctly separated even when only sexually non-dimorphic characters are used. Since considerable number of these characters is acknowledged, a joined analysis of both sexes is proven to be appropriate for the identification of the subgenera. Characters for the species recognition of Spelaeocaris and Troglocaridella females are provided. In the subgenus Troglocaris s. str., molecularly recognized phylogroups are separated by DFA despite the expressed clinal variation. Also, minimum spanning tree (MST) demonstrates the existence of considerable morphological differences. The amounts of morphological difference (indicated by the length of the MST lines) and genetic difference are concordant i.e. morphological differences among the subgenera exceed the ones within the subgenera.