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Biospeleology of the Piemonte |
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Systematic Photographic |
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Biospeleology of the Piemonte |
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An outline of Biospeleology
Biogeography
The life, in all its complexity, manifest in nature a great variety of forms and species. Any of these organisms is not accidentally distributed on the surface of the Earth. Every species lives only in an limited area regarding the dimensions of the planet, variable from species to species. There are in fact rare organisms and other that are most common. This inequal distribution space is one fundamental characteristic of the living beings and is due to the fact that every species have evolued, in the course of its history, a particular physiology, behaviour and processes of developement, that work only in a particular environment, with limiting conditions and certain kinds of food resources.
Under this point of view other important processes like the competition, the specialization, the natural selection have an important role. But fundamental it is to comprise that the environmental conditions which temperature, light, humidity and food resources absolutely are not distributed homogenous: therefore, also the distribution of the organisms will not be uniform.
The biogeography studies the distribution of the living beings in the time and in the space and the factors that determine or limit it.
Limits of distribution
The place in which lives habitually an animal or vegetable species and where it is more often available that not elsewhere is called habitat.
Around to the zones of distribution of a species (considered on geographic scale or to level of habitat) exist areas in which such species cannot be present with its own population why the synecological relationships (of competition with the other species) are too much influential and the physical conditions or the lack of food resources are too much marked for its survival. These areas can be considered as true barriers that the species must absolutely cross if it wants to diffuse in other favorable places not still colonized.
Examples of barriers can be the seas or oceans for terrestrial species; extensions of earth, especially desertic, represent instead an insurmountable obstacle for aquatic organisms, but also the mountainous chains render much difficult the diffusion of the life, because they introduce peaks of too much intense cold for numerous living beings.
When the organisms begin to extend its own distribution also on
geographic scale, probably they profit of temporary, seasonal or
permanent climatic changes, or of variations in the distribution of the
habitats (i.e. intense numerical competition, scarsity of food, etc), that permit
them to cross otherwise unsurpassable barriers. In truth the obstacles
are not only the hostile environmental factors, how
much the same physiology and degree of adaptability of the species. Many species, that in past had a
wide distribution, was interested from climatic changes and today they survive
only in some "islands" in which the climate is favorable for them. Such
species are called climatic relict. They aren't
necessarily species with a long evolutionary history, since the climatic
modifications of greater relief have been produced in relatively recent ages.
The northern hemisphere, moreover, is populate by numerous
species whose distributions have been modified in consequence of the
regression towards North of the ices that were extended until the great
lakes in North America and until the Germany in Europe during the
glacial periods of the Pleistocene (the last ones glaciers have been withdrawn
from Britain approximately 10,000 years ago). Many species adapted to the cold
climate was distributed in that age to South of the ice caps, nearly to the
Mediterranean region. Today these areas are much warmer, so that such species
can survives only in particularly cold places (i.e. in the high elevations of the
mountain chains) or much to North, in the Scandinavian countries, in Scotland and Iceland. There are singular
examples of species that, extinguished by now in the northern regions,
today are only represented in mountainous and cold places of southern regions by
populations that can be considered as glacial relict. The glacial age finished with a quick heating of the climate
and the glaciers withdrawn towards the North; the plants and the animals
that have been pushed to South in the course of
the glacial periods, migrated towards North following the ice. The animals fond of the warm could quickly
move towards the North. The answer of the vegetables was obviously slower because of their more gradual ability of diffusion. With the melting of the ice the sea levels
increased and some of the colonizing species that had caught up new areas through mainland
connections were isolated by the elevation of the level of waters. Moreover many termophile vegetables and animals, typical of the Mediterranean region, survived during the
glaciations in the belt of southern Europe or in the coastal zones of western
Europe, where they had found areas with humid and mild climate faraway from the
rigors of ices. Origin of the current distribution of the living beings We consider a whichever new group of
organisms that appeare in a determined territory suited to it. If
it enters in competition with another group, previously settled in the
zone, the expansion of the distribution of the new group can provoke one
contraction of the preexisting distribution of the previous one. Later on, however, its
ability of diffusion will depend initially on its ability to cross
the geographic barriers or to adapt to the different climatic conditions
that characterize this new zone, but could be limited also by the
presence of groups better adapted to that environment. Gradual climatic changes, that interest the entire world,
could provoke phenomena of migration of the faunas and the floras towards North
or South, for to catch up more favorable zones, or could provoke extinctions in those ones
become climatically inhospitable. In the same way the migratory possibilities could vary because of
the appearance of new geographic or ecological barriers. Until not many years ago the different distributions of animals and
vegetables were explained only taking in examination some fundamental factors:
evolution, climatic variations (i.e. glaciations) and connections of zones through
mainland bridges. That finds confirmation in many testimonies offered by the more
recent past. But these and other phenomena must be inserted in a picture much
more complex that interests all our planet. The theory of the continental drift The singular and unforeseeable
distributions of the flora and the glaciers in the Palaeozoic (Carboniferous and
Permian, from 360 to 245 million years ago) make to think to one position of
the continents much different of that current one: joined among themselves to
form an only continent, called Pangea, and extended more to South than currently. In order to catch up the current position they moved away
each other nearly fluctuating to the drift towards North; in the
first years of the last century someone already advanced similar hypothesis, but
was a German, Alfred Wegener, to supply analysis and tests and to
formulate one first theory in 1915. Nevertheless, only from 1953 the theory
of Wegener on the continental drift began to little to little to be accepted.
According to such theory Africa and Eurasia gradually go away from the
American continent; Arabia has approximated to southern Asia and Africa to
Europe, shrinking the ancient ocean of Tetide, which rests can today be
recognized in the Mediterranean Sea, and provoking in the Tertiary and Quaternary (from 65
million years ago to the present) the raising of the alpine chain; Australia has been
detached from Antarctica and it has headed towards North; finally, only in the
Tertiary, India entered in contact with Asia, provoking the raising of the
Himalajan chain. All these movements are still in course, even if slowest (of the order of 3-10 cm per year). In the geologic history of the
Mediterranean basin, applying the "tectonic to plates", the vision of
the palaeogeography of the western Mediterranean and its historical vicissitudes has
been modified a lot regarding the traditional one. The
modern hypothesis on the "rotation" of the Sardinian-Corse microplate in its
movement of drift that have detached it from the French coast for bring
it in the current situation, have carried to rethink the faunistical
population of the Sardinian caves and to verify the correspondence, or the
eventual discordances, from the reconstructions of the geologists, much more that in
these last ones it could perhaps to be the answer and the explanation to
the often artfull reconstructions of "continental bridges" between the
Tuscany and the Sardinia. Such movements cannot not have influenced the living world,
but very gradually, during million of years. Some consequences can be: - climatic changes
Climatic relict
- proximity to the sea with more variable and humid meteorological conditions for the position of the seas among the continents;
- increase of the climatic variability inside of the continental masses for the appearance of new mountainous chains.
The endemites and the glacialism
Also our region during the glaciations of the Quaternarry was subject to the partial occupation of the valley by part of the glacial masses that came down from North and to the creation of some islands free from the ice and perennial snows, constituted by the elevated portions of mounts and by the more meridionals massifs. Such territorial oasis, called "massifs or areas of refuge", constituted practically islands of salvation for the preglacial faunas; here in fact could survive those species that already were settled in, while other planitial elements found shelter here, coming from the neighbouring zones occupied by the ice, and other species pushed towards South by the progressive invasion of the ice.
The geographic isolation, in which these elements found themselves during the Quaternary, without possibility of copulation and therefore of genetic exchanges among the populations of the different "massifs of refuge", favored the formation, inside to the single species, of geographic races or new subspecies or even new species deriving from an single ancestor.
At the end of the Würmian glaciation (the last one, from 75,000 to 10,000 years ago), the invertebrates manifested different levels of ability in the recolonisation of the valley floor after the glaciations, above all in relation to their ecology and therefore to their possibilities of biological adaptation.
Four different categories of endemites can be distinguished:
1.
Stenoendemites: species with particular ecological requirements, today with a very narrow and punctiform areas, and most scarce possibilities of movement, without abilities of recolonisation;2.
Euriendemites of the massifs of refuge: species with limited dissemination possibility and precise ecological requirements, confined in the mountainous massifs;3.
Euriendemites, reimmigrant "to short distance": species that recolonized small portions of areas before covered by ice;4.
Euriendemites, reimmigrant "to long distance": species with wide ecological valence and remarkable abilities of recolonisation, that occupied large regions.Another numerous group of species, ubiquitary, without particular ecological requirements did not have difficulty to recolonize immense territories: they are species that occupe wider areas (i.e. medium-European and euro-Asians species).
Endemites of the Piemonte and the Valley of Aosta
The glacial phenomena have remarkably interested the western alpine arc. Glaciers constituent a summital glacial cap has interested all our higher mountains, above 2000 m, even if cannot be excluded the presence of refuge areas that, for local conditions due to the orographic conformation, can be remained excluded by the grip of the ice also to high elevations; the true refuge belt could has been, but, that one comprised between the valley floor glaciers and the cacuminal caps.
Particularly resistant organisms to the cold can be survived in local conditions. Recently the author has dicovered new species of Opiliones of the genus Ischyropsalis in the high Valsavarenche (Aosta Valley) in the cave called "Borna du Ran".
Much more interesting has been the examination of the prealpine zone, in areas considered marginal regarding to the last glaciations.
The examination of small caves placed in little lenses of limestone in the Valley of Ribordone, collateral Valley of the lower Locana Valley, in the zone of the Peak of Arbella have allowed to discover that one is currently the species more specialized to the hypogean life among the Coleoptera Cholevidae of the Piemonte: Canavesiella lanai, in one belt comprised between 1200 and 1850 m of elevation.
On the left orographic side of the lower Valley of Aosta, in the common of Carema, approximately at 1400 m of altitude, fissures of tectonical origin as the "Boira dal Salè" and the "Cave of the Maletto" have protected from the grip of the ice another Cholevidae, Archeoboldoria lanai. In the northern zone of the western prealpine arc there is a wide belt colonized between 1000 and 1800 m of altitude by the Cholevidae Archeoboldoria doderoana which distribution has been recently (1999) made discontinuous by the discovery of one new species of the same genus: A. pascuttoi in a mine of the lower Cervo Valley, near Biella.
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Coming down along the margins of the western alpine arc, we find to elevations around 900 m, in the low Valley of Lanzo, in the group of Caves of the Pugnetto, the Cholevidae Dellabeffaella roccai.
To south of the Valley of Susa, interested by a most intense glacialism, we find, to elevations comprised between 800 and 1200 m, in the Chisone and Germanasca Valleys, the Cholevidae Dellabeffaella olmii.
Relations between geographic distribution of the Leptodirinae of the "phyletic series of Dellabeffaella" and the maximum extension of the quaternary glacial cover (continuous dark line) in the Western Alps. Archeoboldoria doderoana Jeannel (
ý); Archeoboldoria lanai n.sp. Giachino & Vailati(P); Archeoboldoria pascuttoi n.sp. Giachino, Lana & Vailati (ÝP); Canavesiella lanai n.sp. Giachino (ý); Canavesiella casalei n.sp. Giachino (à); Dellabeffaella roccai Capra (p); Dellabeffaella olmii Casale (Ê).
Still more to South, from the orographic
right side of the Po Valley until the watershed between the Maira and Grana Valleys,
is diffuse the genus Parabathyscia with two species, oodes and
dematteisi, to elevations comprised between 500 and 1300 m.
The living areas of the genus Dellabeffaella and Parabathyscia is overlapped in part to that one of the Carabidae of the genus Doderotrechus, true living fossils, with the species ghilianii, crissolensis and casalei. In particular this last comes down to quotas decidedly low, around 600 m of elevation, and is an endemite of the Caves of Rossana and of the surrounding zones, while the others two species have an living area that goes from the high Po Valley to the righ orographic side of the Chisone Valley, until quotas around 1500 m.
All the zone to south of the Maira Valle is populate by some species of Carabidae Trechinae of the genus Duvalius; the species Agostinia launoi is rare and specialized, and lives in the high Pesio Valley and on the Massif of the Marguareis.
Final considerations
The geographic position of one cavity conditions the presence of a population to its inside. The greater part of the terrestrial troglobites shows a distribution limited to southern Europe and Asia and Southeastern United States, zones marginally interested from the glaciations of the Quaternary; it is believed therefore that the climatic changes, begun to the end of the Tertiary and continued in the Quaternary, have hardly influenced the hypogean population.
Currently exist European areas adapted, from the ecological point of view, to the installation of hypogean organisms, but that instead are much poor of troglobite organisms: they are zones situated to North of the southern margin of the areas covered by the ice.
Particular climatic conditions can induce the movement of epigean organism towards the underground environment (colonization). The population of a subterranean system is strongly conditioned by the historical, palaeogeographic and geologic vicissitudes suffer by the territory in which it lives.
Numerous cavernicole organisms are true and "living fossils", relicts of ancient faunas sometimes with extraordinary modifications and adaptations. Some studies have demonstrated, as an example, that the current distribution of troglobite elements of marine origin, correspond exactly to the configuration of the coasts of the ancient seas: the distribution of Monolistra sp. and Caecosphaeroma sp. (Crustacea Isopoda Spheromidae) reflect the geographic situation of the Mediterranean during the Miocene (from 24 to 5 million years ago). This fact, with the presence of marginal species in the prealpine refuge massifs, allows us to delimit biologically, by means of the discovery of troglobite species, the ancient limits of the seas and the glaciers.
The absence of troglobites in the North of the United States and in the center-northern Europe is probably from due to the massive phenomena of glacialism of the Quaternary, while their absence in some coastal caves can be in some case explained by geologic phenomena like the bradisisms and the elevation of the sea level, that can have interested in past the coastal margins of the continents.
An outline of Biospeleology
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BIBLIOGRAPHY |
BIBLIOGRAPHY |
BIBLIOGRAPHY |
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Biospeleo SUMMARY |
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Systematic Index |
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