The clade is highly genetically differentiated, the most unexpected finding are two clearly separated evolutionary lineages; one is comprising of three subspecies (N. steueri, N. liburnicus in N. subtypicus) and the other one another set of taxa (N. subtypicus, N. croaticus in N. dolichopus). N subtypicus in N. croaticus are highly morphologically divergent, they could be assigned to two different ecomorphs, so called lake and daddy longleg ecomorph. Results are indicating that non adaptive radiation acts in allopatry, meanwhile in sympatry adaptive radiation leads to origin of new ecomorph. According to those results, a new working hypothesis was set: competition between species is leading transition from one ecomorph to another. To test the hypothesis, a study of phylogeny, modelling of morphological evolution and modelling of competition and dispersal from spatial and molecular data were performed. Results support our hypothesis that competition was a main process leading to high morphological differentiation within the clade.
In the last decade, several studies have shown that subterranean aquatic habitats harbor cryptic species with restricted geographic ranges, frequently occurring as isolated populations. Previous studies on aquatic subterranean species have implied that habitat heterogeneity can promote speciation and that speciation events can be predicted from species’ distributions. We tested the prediction that species distributed across different drainage systems and karst sectors comprise sets of distinct species. Amphipods from the genus Niphargus from 11 caves distributed along the Western Carpathians (Romania) were investigated using three independent molecular markers (COI, H3 and 28S). The results showed that: 1) the studied populations belong to eight different species that derive from two phylogenetically unrelated Niphargus clades; 2) narrow endemic species in fact comprise complexes of morphologically similar species that are indistinguishable without using a molecular approach. The concept of monophyly, concordance between mitochondrial and nuclear DNA, and the value of patristic distances were used as species delimitation criteria. The concept of cryptic species is discussed within the framework of the present work and the contribution of these species to regional biodiversity is also addressed.
COBISS.SI-ID: 2943567
Subterranean animals are known for their highly evolved phenotypes. They are eyeless, depigmented and possess elongated appendages compared to their surface relatives. Increased antenna and leg length of cave species has traditionally been explained as a consequence of selection for non-visual senses and increased food finding ability in an environment low in energy. Variation in appendage length between cave species is usually thought to result from differences in time since the colonization of the subterranean habitat. In this study, we analyzed appendage length variation in the Dinaric amphipod species Niphargus croaticus. Relative length of appendages varied substantially among populations. Using multilocus phylogenetic analysis, we showed that the species is nested within highly specialized N. steueri species complex and rejected the time hypothesis. Next, we explored the effects and strength of two environmental factors, water flow and presence of a competing species, N. subtypicus. Populations in caves with flowing water had shorter appendages than populations in cave lakes. Presence of the competing sister species did lead to longer appendages in stagnant water, but had no effect in flowing water. Abiotic factors had a stronger effect than biotic factors, but their relative strength differed among appendage pairs. High variation in appendage length between adjacent population shows that the morphology of cave arthropods is changing quickly and therefore cannot be used to predict species age. Rather than being a general adaptation to cave life, long appendages seem to be associated with the absence of water flow as well as character displacement when in sympatry with ecologically similar competing species.
COBISS.SI-ID: 3744591