SUMMARY1. Various groundwater habitats have exceptionally high levels of endemism caused by strong hydrographical isolation and low dispersal abilities of their inhabitants. More than 10% of macro-stygobiotic species nevertheless occupy relatively large ranges, measuring from some hundred to over 2000 km in length. These species represent a challenge because their distributions disregard hydrographical boundaries, and their means to disperse and maintain long-term gene flow are unknown. 2. Based on mitochondrial and nuclear gene sequences, we examined the phylogeographic structure of six formally recognised stygobiotic species (Niphargus virei, N. rhenorhodanensis, Troglocaris anophthalmus, T. hercegovinensis, Spelaeocaris pretneri, Proteus anguinus) and searched for cryptic lineage diversity in a genus-wide phylogeny of Niphargus. Using treebased criteria as well as comparative divergence measures, we identified cryptic lineages, which may tentatively be equated with cryptic species. 3. Fourteen analysed nominal stygobiotic species with large ranges emerged as highly diversified, splitting into 51 tentative cryptic lineages. The degree of divergence was within the range or larger than the divergence of other related pairs of sister species. A substantial part (94%) of the cryptic lineages had ranges <200 km in length. One half of them were recorded at single sites only. The largest range recorded was that of a cryptic N. virei lineage (700 km), while none of the very large traditional ranges (e.g. Niphargus aquilex -2300 km, N. tauri -1900 km) could be corroborated. 4. These data suggest that small ranges of macro-stygobionts are the rule, and ranges over 200 km are extremely rare. 5. The implications of this result for groundwater biodiversity assessment and conservation include a considerable increase in overall diversity at the regional and continental scale and a strong decrease in faunal similarities among regions, coupled with greater endemism.

Current theory predicts that a shift to a new habitat would increase the rate of diversification, while as lineages evolve into multiple species, intensified competition would decrease the rate of diversification. We used Holarctic amphipods of the genus Gammarus to test this hypothesis. We sequenced four genes (5,088 bp) for 289 samples representing 115 Gammarus species. A phylogenetic analysis showed that Gammarus originated from the Tethyan region with a saline ancestry in the Paleocene, and later colonized the freshwater habitat in the Middle Eocene. Ancestral range reconstruction and diversification mode analysis combined with paleogeological and paleoclimatic evidence suggested that the habitat shift from saline to freshwater led to an increased diversification rate. The saline lineage of Gammarus dispersed to both sides of the Atlantic at 55 million years ago (Ma), because of the few barriers between the Tethys and the Atlantic, and diversified throughout its evolutionary history with a constant diversification rate [0.04 species per million years (sp/My)]. The freshwater Gammarus, however, underwent a rapid diversification phase (0.11 sp/My) until the Middle Miocene, and lineages successively diversified across Eurasia via vicariance process likely driven by changes of the Tethys and landmass. In particular, the freshwater Gammarus lacustris and Gammarus balcanicus lineages had a relatively high diversification shift, corresponding to the regression of the Paratethys Sea and the continentalization of Eurasian lands during the Miocene period. Subsequently (14 Ma), the diversification rate of the freshwater Gammarus decreased to 0.05 and again to 0.01 sp/My. The genus Gammarus provides an excellent aquatic case supporting the hypothesis that ecological opportunities promote diversification.evolution | molecular dating | range expansion

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The world's obligate cave‐dwelling fauna holds considerable promise for biogeographic analysis because it represents a large number of independent evolutionary experiments in isolation in caves and adaptation to subterranean life. We focus on seven north temperate regions of at least 2000 km2, utilizing more than 4300 records of obligate cave‐dwelling terrestrial invertebrates. In North America, highest diversity was found in northeast Alabama while in Europe highest diversity was found in Ariège, France, and in southeast Slovenia. Based on these regions as well as more qualitative data from 16 other regions, we hypothesize that a ridge (ca 42°–46° in Europe and 34° in North America) of high biodiversity occurs in temperate areas of high productivity and cave density. This may reflect a strong dependence of cave communities on long term surface productivity (as reflected in actual evapotranspiration), because the subterranean fauna relies almost entirely on resources produced outside caves. This dependence may explain the unique biodiversity pattern of terrestrial cave invertebrates.

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