Most of the larger European high mountain systems possess endemic species (or at least subspecies) confined to just one of them. As the Alps are by far the most extensive and highest mountain system of Europe, it is not surprising that the highest number and amount of endemics of typical high mountain species is found in this mountain range, as for example demonstrated by lepidopterans and especially in the little mobile group of the micro-moths 20. Some of these alpine endemics (in animals as well as in plants) are widespread all over this mountain area, stretching almost the entire range from Nice in the southwest to Vienna in the northeast (in many cases showing remarkable genetic substructure, see below); while others are more or less local endemics of some parts of the Alps.

Two types of hotspots for local endemics of the Alps can be distinguished:

(i) Species with their ranges restricted to peripheral regions of the Alps and mostly confined to lower and intermediate elevations (e.g. observed in some Erebia species, Lycaenids etc.; for details see Varga & Schmitt 20). The largest concentrations of these local endemics are in the regions of the southwestern and the southeastern Alps, two regions with larger areas at lower altitudes not covered by ice during glaciations. These ice-free areas most probably served as centres of glacial survival, from where these species only performed altitudinal shifts, but no major range expansions over large parts of the deglaciating Alps. As these taxa might have performed these altitudinal shifts repeatedly through the climatic fluctuations of the Pleistocene, these refuge areas might also be the locations of the evolutionary process of speciation 1. However, genetic analyses in this group of species are scarce and in butterflies restricted to the three taxa Coenonympha darwiniana 30, C. macromma 30 and Erebia sudetica inalpina (Figure 1) 31. The latter is today confined to the region of Grindelwald (Berner Oberland, northwestern Alps) and most probably survived at least the last glaciation in a geographically restricted refuge area northwest of the Alpine ice-shield, likely suffering population bottlenecks and subsequent genetic erosion 31. The two Coenonympha taxa are restricted to the south-central Alps (C. darwiniana) and the Alpes Maritimes (C. macromma). Both might have survived also at least the last ice age at lower elevations close to their recent distributions 30.

(ii) Species restricted to some parts of the Inner Alps, as for example a number of (often flightless) micro-moth species 32 and beetles 5, but only a single butterfly species (i.e. Erebia nivalis) 20. These species in general are confined to high alpine habitats and may have survived glaciations in situ at so called Nunataks (i.e. small ice-free areas topping over the ice-shield of the Inner Alps). For animals, survival in these areas is only supported by chorological data sets (i.e. distribution pattern) 520, but genetic data in plants give some support for these refuges (see Schönswetter et al. 33 for a recent review, 3435).

Although the Alps are the European mountain system with the highest number of endemic species, numerous endemic genetic lineages or taxa are known for almost all high mountain systems in parts of Europe not entirely being covered by ice during the glacial periods. However, there are peculiar differences between the more marginal (e.g. Cantabrian Mts., Bulgarian Mts.) and more central (e.g. Carpathians, Massif Central, Apennines) mountain systems.

Thus, the more marginal mountain areas of Europe have particularly high proportions of old evolutionary units (often with relict status) when compared to more geographically central mountain ranges. For example, cases of such old genetic lineages are known for the flora of the Cantabrian Mts. in northwestern Spain [e.g. 363738]; the number of examples in animals is rather low, but the known cases support the patterns observed in plants well, e.g. the butterfly Proclossiana eunomia 3940 and the caddisfly Drusus discolor (Figure 2) 41.

Another stronghold of strongly differentiated genetic lineages and endemic species is situated in the Bulgarian high mountain systems. Thus, the most distinct genetic lineages of the beetle Nebria rufescens and the butterfly Erebia pandrose, two arctic-alpine species, were found here 42; a strongly differentiated genetic lineage was also found in the Proclossiana eunomia populations from the Stara Planina 39. In the spiders of the Pardosa saltuaria species group, the populations from the Bulgarian mountains, and also from the Pyrenees, showed a strong differentiation from a northern clade including the Alps, Carpathians, some middle high mountains of Central Europe and Scandinavia (Figure 3) 43. The caddisfly Drusus discolor also showed strongly differentiated genetic lineages for all of the marginal mountain systems of Europe where the taxon occurs, including the high mountain systems of Bulgaria (Figure 2) 41. Also plants in the Balkan high mountain systems showed strongly differentiated genetic lineages from other regions of Europe 44.

Furthermore, the distribution pattern of some species and subspecies strongly support these observed genetic structures. Thus, the eastern Balkan mountains are the only mountain range of the southern part of Europe where the fairly widespread mountain ringlet Erebia epiphron is lacking, but the species is substituted by its sister taxon Erebia orientalis supporting the strong evolutionary independence of this region. Regarding this latter species, each of the three mountain ranges harbouring it (i.e. Rila, Pirin, Stara Planina) has its own subspecies with strong morphological differentiations among them 4546. A similar situation is also observed for the only occurrences of Euphydryas cynthia outside the Alps: the male individuals of the Pirin population consistently have a considerably more extended white wing colouration than average populations from the Alps, while the white colouration is strongly reduced in the Rila individuals 45. This also underlines the evolutionary independence among these mountain ranges of the eastern Balkan Peninsula on a fairly small geographic scale of sometimes only few tens of kilometres.

Such old lineages are fewer in the mountain systems with closer geographic connections with the Alps (e.g. Carpathians, Massif Central), and genetic differentiations of these mountain systems from the Alps are often low; most examples come from plants [e.g. 36384748], but also include the Pardosa saltuaria spider species group (Figure 3) 43. On the species level, these mountain ranges mostly share their species with the Alps. However, well distinguished subspecies are known for these mountain species with many examples in the genus Erebia (e.g. E. epiphron, E. euryale, E. gorge, E. manto, E. melas) 49, but the ages of these splits are mostly unknown and some even might be rather recent, even postglacial.

The Pyrenees have an intermediate position, in which they show some close connections to the Alps (see below), but also have numerous endemic species (e.g. in lepidopterans Erebia gorgone, three Sattleria species) 2049; their number however is much lower than in the Alps, which are considerably higher and much more extended. Many mountain species with larger distributions show endemic lineages in the Pyrenees or parts of them, thereby supporting the idea of differentiation centres at the lower elevations of the Pyrenean area and recent (mostly postglacial) range shifts to higher altitudes of the mountains, as demonstrated for the butterflies Erebia epiphron (Figure 4) 50, Erebia euryale (Figure 5) 51, Erebia pandrose 42 and Erebia manto (unpublished data), but also other animal 4143 and plant species 36.

The summer-arid high mountain areas of the extreme south of Europe (especially southern Iberia and the southern Balkan Peninsula) and the Maghreb (here in particular the Atlas Mts.) do not have the typical alpine zonation 52, but show typical oro-Mediterranean characteristics. Some mountain species show local endemism to strongly confined mountain blocks in this area as e.g. known for a number of butterfly species 204549. These species in many cases represent relicts of often old invasions of species with their closed biogeographical connections to Central Asia 205354.

The Alps as the largest European high mountain system show a remarkable phylogeographic structure in many species. In plants, a differentiation into four genetic units along the Alps seems the most common feature with these lineages typically being confined to the southwestern, western central, eastern central and eastern Alps and the eastern lineages more often being of higher genetic diversity than the more western ones 23342. A quite similar pattern to that in many plant species was proposed for the leaf beetle Oreina elongata 55. Also other animals frequently show different genetic lineages in the Alps, but their number is often less than in plants, and in many cases, only a western and an eastern lineage can be distinguished. This is the case in the two butterflies Erebia melampus (Figure 1) 31 and Erebia euryale (Figure 5) 51, the wolf spiders species group Pardosa saltuaria (Figure 3) 43 and the caddisfly Drusus discolor (Figure 2) 41. In the first case, two strongly differentiated lineages (supported by allozyme polymorphisms 31 and differences in the male genitalia 56) can be distinguished with a contact zone running north-south through Tyrol and along the Adige/Etsch valley (maybe with some hybridisation in a limited area of southeastern Switzerland and South Tyrol). The differentiation between these two lineages is rather advanced, and they most probably represent different species, with the eastern lineage showing a significantly higher genetic diversity than the western one 31. These genetic and morphological differences are best explained by allopatric differentiation in two centres; and as the beginning of the first split is assumed to be older than the last ice age, the location of the initial differentiation centres must remain enigmatic. However, the most likely Würm glacial refuge centres are in the hilly areas south of the Upper Italian Lakes for the western lineage and in the lower elevation areas of the southeastern Alps (eastern Carinthia, Styria, Friul, parts of Slovenia) for the eastern lineage. Based on the higher genetic diversities of the populations belonging to the eastern lineage, we may assume that the survival conditions were more suitable in this eastern region and/or this refuge area was geographically considerably more extended than the more western refuge 31. A very similar pattern was observed for Erebia euryale (Figure 5) with the only difference that survival of the western lineage is more likely around the southwestern Alps 51. The caddisfly Drusus discolor repeats this geographic structure of a western and an eastern Alpine lineage (Figure 2) 41. A much more complicated case is known in the butterfly Erebia epiphron 50. This species comprises four strongly differentiated lineages in the Alps: western Alps, Aosta valley, northern Alps and eastern Alps (Figure 4). These lineages most probably evolved in four differentiation centres west, south, southeast and north of the Alps, often linking the Alps with other mountain systems (see below).

As in the Alps, more than one genetic lineage per species is also observed in mountain elements of the Pyrenees 20. However, the Pyrenees are considerably less extended than the Alps, and the maximum number of different lineages found here is not as high as in the Alps; many species do not show marked differentiation over the Pyrenees. As an example, two different lineages are observed in the Pyrenees for Erebia epiphron (Figure 4), one in the western and the other in the eastern parts of these mountains, with the first one most probably surviving the last ice age north and the second in the southeastern parts of the Pyrenees 50. Also for the plant Cardamine alpina, AFLP patterns suggest survival in multiple Pyrenean refugia 57.

Although being the largest high mountain system of eastern/southeastern Europe, only a few genetic analyses include populations from more than one part of the Carpathian arc. However, compiling existing data for different plant species revealed a generally lower genetic diversity of the populations in the Carpathians than in the Alps, maybe due to higher topographic isolation of alpine habitats in the Carpathians 58.

One study on animals that included a considerable number of samples from the Carpathian region was performed on the caddisfly Drusus discolor and showed a remarkable differentiation between the northwestern and the southern Carpathians (Figure 2). This thus supports the idea of a long lasting separation between these two parts of this high mountain system predating at least the last glaciation 41. Similar cases are also reported for plants as Hypochaeris uniflora 59 and Campanula alpina 60.

Thus, multiple glacial survival centres exist along the Carpathian arc, as in the cases of the Pyrenees and especially Alps, but the number of known cases is still rather limited. Therefore, a research focus on the phylogeography of the Carpathians is needed.

The biogeographical links between the Pyrenees and the Alps are seen in the occurrences of many taxa with restricted distributions in these two areas, e.g. in lepidopterans by taxa as Euchloe simplonia, Polyommatus g. glandon, Aricia n. nicias, Erebia o. oeme 49. However, the same genetic lineages are also repeatedly found in these two regions, as in the case of Erebia cassioides 61 and Erebia epiphron (Figure 4), which has genetically very similar populations in the western Pyrenees and the southwestern Alps, e.g. the Wallis in Switzerland 50. The genetic similarity in this case is best explained by a Würm glacial link between the Pyrenees and the Alps, and thus a more widespread distribution in the hilly regions of France between these two high mountain systems during this time period. The postglacial disjunction has not been sufficiently long for the evolution of a clear differentiation between these now disjunct parts of the distribution. Similar patterns are also known for mountain plant species 476263646566. In the case of Carex curvula, the Pyrenean populations are nested within the western Alps group and show a low level of genetic diversity, probably due to recent long distance colonisation 67.

As in the case of the Pyrenees-Alps connections, many biogeographical interactions exist between the northeastern Alps and the northwestern Carpathians (i.e. Tatra Mts.). Typical examples are found in distribution patterns of lepidopterans like Pieris bryoniae and Erebia pharte 49. An mtDNA analysis of the wolf spider species complex Pardosa saltuaria also underlines this link as the same mtDNA lineage was detected in the Alps and Carpathians (Figure 3) 43.

So far other genetic data for animals are lacking, but data on plants support this biogeographical link (e.g. for Pritzelago alpina 36 and Senecio carniolicus 48). For Ranunculus alpestris, the Carpathians have been colonised stepwise from an eastern Alpine lineage 68, and the arctic-alpine Ranunculus pygmaeus colonised the Alps relatively recently from the east through the Tatra Mts. 69. A relatively similar genetic link was observed between the northern Alps and the mountains of northern Moravia about 200 km west of the High Tatra Mts. for the butterfly Erebia epiphron (Figure 4) 50.

Nevertheless, many examples also revealed long-lasting separations between the populations from the Alps and the Carpathians 57606570.

The southeastern edge of the Alps is biogeographically strongly linked with the mountains of the western Balkan Peninsula, as demonstrated by many occurrences of identical mountain beetle species in the southeastern Alps and the northwestern Balkan mountains 520. While less in number, this distribution type is also known in the Lepidoptera for taxa like Coenonympha gardetta, Erebia ottomana, E. stirius, E. oeme spodia, E. epiphron aetheria and E. styx trentae 49. These distribution patterns support the survival of mountain species in the southeastern parts of the Alps and adjoining areas (as demonstrated for Erebia melampus (Figure 1) 31 and Erebia euryale (Figure 5) 51), with postglacial retreat into the Alps in the northwest and the northwestern Balkan mountains in the southeast.

Genetic data sets supporting these biogeographical links for animals are (to my knowledge) not available at the moment, but genetic data on plants support these connections e.g. in the species Pulsatilla vernalis 65 and Polygonatum verticillatum 38. Considering morphological studies, the western Balkan populations of Erebia pandrose in the high mountain systems of Monte Negro, Serbia and Macedonia are closely related with populations existing in the southeastern Alps. This thus supports a recent (i.e. Würm glacial) biogeographical link between these two areas that are now separated by several hundreds of kilometres with no mountains over 2,000 m. On the contrary, the Erebia pandrose populations of the high mountain systems Rila and Pirin in Bulgaria are strongly differentiated from this group, and more closely related with the populations from the southern Carpathians 71, thus underlining a biogeographical east-west split throughout the central Balkan Peninsula 72.

The Danube valley apparently has often acted as effective dispersal barrier between the Carpathians and the high mountain systems of the eastern Balkan Peninsula 20 with Erebia medusa being a well studied case in the Lepidoptera 18. However, many connections between the mountain systems of these two areas are also known. Thus, a morphometric study of the male genitalia of Erebia pandrose demonstrated high similarities between these two high mountain areas 71 and hereby also supported a close biogeographical link between them.

An allozyme analysis of the mountain forest species Erebia euryale revealed by far the highest genetic diversity in this species in the populations from the Bulgarian Rila and the Romanian southern Carpathians, but no significant differentiation was detectable between these two areas (Figure 5) 51. This is most probably due to the fact that these two areas were linked by cool forested areas during at least the last ice age allowing massive gene flow between these two regions; thus, at least the region of the Iron Gate (passage of the Danube through the southern Carpathians) must have been extensively covered by this type of forest during this time period. Furthermore, this study supports the conclusion of other analyses based on fossil remains (e.g. pollen, remains of animals) 737475767778 that southeastern Europe was the most important glacial retreat of the representatives of the European mountain forest biome.

Furthermore, the distribution of many mountain species (e.g. Erebia melas, E. cassioides, Coenonympha rhodopensis) in the Bulgarian high mountain systems and the southern Carpathians underlines the biogeographical connections of the high mountain biota of both areas 20. Genetic links between both areas are also known for plant species 67.