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ACCLIMATIZATION
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ACCLIMATIZATION , the See also:process of See also:adaptation by which animals and See also:plants are gradually rendered capable of surviving and flourishing in countries remote from their See also:original habitats, or under meteorological conditions different from those which they have usually to endure, and at first injurious to them . The subject of acclimatization is very little understood, and some writers have even denied that it can ever take See also:place . It is often confounded with domestication or with See also:naturalization; but these are both very different phenomena . A domesticated See also:animal or a cultivated plant need not necessarily be acclimatized; that is, it need not be capable of enduring the severity of the seasons without See also:protection . The See also:canary See also:bird is domesticated but not acclimatized, and many of our most extensively cultivated plants are in the same See also:category . A naturalized animal or plant, on the other See also:hand, must be able to withstand all the vicissitudes of the seasons in its new See also:home, and it may therefore be thought that it must have become acclimatized . But in many, perhaps most cases of naturalization (see Appendix below) there is no See also:evidence of a See also:gradual adaptation to new conditions which were at first injurious, and this is essential to the See also:idea of acclimatization . On the contrary, many See also:species, in a new See also:country and under somewhat different See also:climatic conditions, seem to find a more congenial See also:abode than in their native See also:land, and at once flourish and increase in it to such an extent as often to exterminate the indigenous inhabitants . Thus L . See also:Agassiz (in his See also:work on See also:Lake See also:Superior) tells us that the road-See also:side weeds of the See also:north-eastern See also:United States, to the number of 130 species, are all See also:European, the native weeds having disappeared westwards; while in New See also:Zealand there are, according to T . See also:Kirk (Transactions of the New Zealand See also:Institute, vol. ii. p . 131), no less than 250 species of naturalized plants, more than zoo of which spread widely over the country and often displace the native vegetation . Among animals, the European See also:rat, See also:goat and See also:pig are naturalized in New Zealand, where they multiply to such an extant as to injure and probably exterminate many native productions . In none of these cases is there any indication that acclimatization was necessary or ever took place . On the other hand, the fact that an animal or plant cannot be naturalized is no See also:proof that it is not acclimatized . It has been shown by C . See also:Darwin that, in the See also:case of most animals and plants in a See also:state of nature, the competition of other organisms is a far more efficient agency in limiting their See also:distribution than the See also:mere See also:influence of See also:climate . We have a proof of this in the fact that so few, comparatively, of our perfectly See also:hardy See also:garden plants ever run See also:wild; and even the most persevering attempts to naturalize them usually fail . See also:Alphonse de See also:Candolle (Geographic botanique, p . 798) informs us that several botanists of See also:Paris, See also:Geneva, and especially of See also:Montpellier, have sown the seeds of many hundreds of species of See also:exotic hardy plants, in what appeared to be the most favourable situations, but that in hardly a single case has any one of them become naturalized . Attempts have also been made to naturalize See also:continental See also:insects in See also:Britain, in places where the proper See also:food-plants abound and the conditions seem generally favourable, but in no case do they seem to have succeeded . Even a plant like the See also:potato, so largely cultivated and so perfectly hardy, has not established itself in a wild state in any See also:part of See also:Europe . Different Degrees of Climatal Adaptation in Animals and Plants.—Plants differ greatly from animals in the closeness of their adaptation to meteorological conditions . Not only will most tropical plants refuse to live in a temperate climate, but many species are seriously injured by removal a few degrees of See also:latitude beyond their natural limits .
This is probably due to the fact, established by the experiments of A
.
C
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See also:Becquerel, that plants possess no proper temperature, but are wholly de-pendent on that of the surrounding See also:medium
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Animals, especially the higher forms, are much less sensitive to See also:change of temperature, as shown by the extensive range from north to See also:south of many species
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Thus, the See also:tiger ranges from the See also:equator to See also:northern See also:Asia as far as the See also:river See also:Amur, and to the isothermal of 32° Fahr
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The See also:mountain See also:sparrow (Passer See also:montana) is abundant in See also:Java and See also:Singapore in a See also:uniform See also:equatorial climate, and also inhabits Britain and a considerable portion of northern Europe
.
It is true that most terrestrial animals are restricted to countries not possessing a See also:great range of temperature or very diversified climates, but there is See also:reason to believe that this is due to quite a different set of causes, such as the presence of enemies or deficiency of appropriate food
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When supplied with food and partially protectedfrom enemies, they often show a wonderful capacity of enduring climates very different from that in which they originally flourished
.
Thus, the See also:horse and the domestic See also:fowl, both natives of very warm countries, flourish without See also:special protection in almost every inhabited portion of the globe
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The See also:parrot tribe See also:form one of the most pre-eminently tropical See also:groups of birds, only a few species extending into the warmer temperate regions; yet even the most exclusively tropical genera are by no means delicate birds as regards climate
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In the See also:Annals and See also:Magazine of Natural See also:History for 1868 (p
.
381) is a most interesting See also:account, by See also:
A considerable number of See also:African and Amazonian parrots, See also:Bengal parroquets, four species of See also: The recently See also:extinct Siberian See also:mammoth and woolly See also:rhinoceros were closely allied to species now inhabiting tropical regions exclusively . Wolves and foxes are found alike in the coldest and hottest parts of the See also:earth, as are closely allied species of falcons, owls, sparrows and numerous genera of waders and aquatic birds . A See also:consideration of these and many analogous facts might induce us to suppose that, among the higher animals at least, there is little constitutional adaptation to climate, and that in their case acclimatization is not required . But there are numerous examples of domestic animals which show that such adaptation does exist in other cases . The See also:yak of Thibet cannot See also:long survive in the plains of See also:India, or even on the hills below a certain See also:altitude; and that this is due to climate, and not to the increased See also:density of the See also:atmosphere, is shown by the fact that the same animal appears to thrive well in Europe, and even breeds there readily . The See also:Newfoundland dog will not live in India, and the See also:Spanish breed of fowls in this country suffer more from See also:frost than most others . When we get See also:lower in the See also:scale the adaptation is often more marked . See also:Snakes, which are so abundant in warm countries, diminish rapidly as we go north, and wholly cease at See also:lat . 62° . Most insects are also very susceptible to cold, and seem to be adapted to very narrow limits of temperature . From the foregoing facts and observations we may conclude, firstly, that some plants and many animals are not constitution-ally adapted to the climate of their native country only, but are capable of enduring and flourishing under a more or less extensive range of temperature and other climatic conditions; and, secondly, that most plants and some animals are, more or less closely, adapted to climates similar to those of their native habitats . In See also:order to domesticate or naturalize the former class in countries not extremely differing from that from which the species was brought, it will not be necessary to acclimatize, in the strict sense of the word . In the case of the latter class, however, acclimatization is a necessary preliminary to naturalization, and in many cases to useful domestication, and we have therefore to inquire whether it is possible . Acclimatization by Individual Adaptation.—It is evident that acclimatization may occur (if it occurs at all) in two ways, either by modifying the constitution of the individual submitted to the new conditions, or by the See also:production of offspring which may be better adapted to those conditions than their parents . The alteration of the constitution of individuals in this direction is not easy to detect, and its possibility has been denied by many writers . C . Darwin believed, however, that there were indications that it occasionally occurred in plants, where it can be best observed, owing to the circumstance that so many plants are propagated by cuttings or buds, which really continue the existence of the same individual almost indefinitely . He adduced the example of vines taken to the See also:West Indies from See also:Madeira, which have been found to succeed better than those taken directly from See also:France . But in most cases See also:habit, however prolonged, appears to have little effect on the constitution of the individual, and the fact has no doubt led to the See also:opinion that acclimatization is impossible . There is indeed little or no evidence to show that any animal to which a new climate is at first prejudicial can be so acclimatized by habit that, after subjection to it for a few or many seasons, it may live as healthily and with as little care as in its native country; yet we may, on See also:general principles, believe that under proper conditions such an acclimatization would take place . Acclimatization by Variation.—A See also:mass of evidence exists showing that See also:variations of every conceivable See also:kind occur among the offspring of all plants and animals, and that, in particular, constitutional variations are by no 'means uncommon . Among cultivated plants, for example, hardier and more See also:tender varieties often arise . The following cases are given by C . Darwin: Among the numerous See also:fruit-trees raised in North See also:America some are well adapted to the climate of the northern States and See also:Canada, while others only succeed well in the See also:southern States . Adaptation of this kind is sometimes very See also:close, so that, for example, few English varieties of See also:wheat will thrive in See also:Scotland . See also:Seed-wheat from India produced a miserable See also:crop when planted by the Rev . M . J . See also:Berkeley on land which would have produced a good crop of English wheat . Conversely, See also:French wheat taken to the West Indies produced only barren spikes, while native wheat by its side yielded an enormous See also:harvest . See also:Tobacco in See also:Sweden, raised from home-grown seed, ripens its seeds a See also:month earlier than plants grown from See also:foreign seed . In See also:Italy, as .long as See also:orange trees were propagated by grafts, they were tender; but after many of the trees were destroyed by the severe frosts of 1709 and 1763, plants were raised from seed, and these were found to be hardier and more productive than the former kinds . Where plants are raised from seed in large quantities, varieties always occur differing in constitution, as well as others differing in form or See also:colour; but the former cannot be perceived by us unless marked out by their behaviouf under exceptional conditions, as in the following cases . After the severe winter of 186o–1861 it was observed that in a large See also:bed of araucarias some plants stood quite unhurt among See also:numbers killed around them . In C . Darwin's garden two rows of See also:scarlet runners were entirely killed by frost, except three plants, which had not even the tips of their leaves browned . A very excellent example is to be found in See also:Chinese history, according to E . R . Huc, who, in his L' See also:Empire chinois (tom. ii. p . 359), gives the following See also:extract from the See also:Memoirs of the See also:Emperor Khang:—" On the 1st See also:day of the 6th See also:moon I was walking in some See also:fields where See also:rice had been sown to be ready for the harvest in the 9th moon . I observed by See also:chance a stalk of rice which was already in See also:ear . It was higher than all the See also:rest, and was ripe enough to be gathered . I ordered it to be brought to me . The See also:grain was very See also:fine and well grown, which gave me the idea to keep it for a trial, and see if the following year it would preserve its precocity . It did so . All the stalks which came from it showed ear before the usual See also:time, and were ripe in the 6th moon . Each year has multiplied the produce of the preceding, and for See also:thirty years it is this rice which has been served at my table . The grain is elongate and of a reddish colour, but it has a sweet See also:smell and very pleasant See also:taste .
It is called Yu-mi, Imperial rice, because it was first cultivated in my gardens
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It is the only sort which can ripen north of the great See also:wall, where the winter ends See also:late and begins very See also:early; but in the southern provinces, where the climate is milder and the land more fertile, two harvests a year may be easily obtained, and it is for me a sweet reflection to have procured this See also:advantage for my See also:people." Huc adds his testimony that this kind of rice flourishes in See also:Manchuria, where no other will grow
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We have here, therefore, a perfect example of acclimatization by means of a spontaneous constitutional variation
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That this kind of adaptation may be carried on step by step to more and more extreme climates is illustrated by the following examples
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Sweet-peas raised in See also:Calcutta from seed imported from See also:England rarely blossom, and never yield seed; plants from French seed See also:flower better, but are still sterile; but those raised from See also:Darjeeling seed (originally imported from England) both flower and seed profusely
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The See also:peach is believed to have been tender, and to have ripened its fruit with difficulty, when first introduced into See also:Greece; so that (as Darwin observes) in travelling northward during two thousand years it must have become much hardier
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See also:Sir J
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See also: By degrees the fecundity improved, and in about twenty years became equal to what it is in Europe . The same author tells us that, according to Garcilaso, when fowls were first introduced into See also:Peru they were not fertile, whereas now they are as much so as in Europe . C . Darwin adduced the following examples . See also:Merino See also:sheep bred at the Cape of Good See also:Hope have been found far better adapted for India than those imported from England; and while the Chinese variety of the See also:Ailanthus See also:silk-See also:moth is quite hardy, the variety found in Bengal will only flourish in warm latitudes . C . Darwin also called See also:attention to the circumstance that writers of agricultural See also:works generally recommend that animals should be removed from one See also:district to another as little as possible . This See also:advice occurs even in classical and Chinese agricultural books as well as in those of our own day, and proves that the close adaptation of each variety or breed to the country in which it originated has always been recognized . Constitutional Adaptation often accompanied by See also:External Modification.—Although in some cases no perceptible alteration of form or structure occurs when constitutional adaptation to climate has taken place, in others it is very marked . C . Darwin collected a large number of cases in his Animals and Plants under Domestication . In hislontributions to the Theory of Natural Selection (p. i67), A . R.See also:Wallace has recorded cases of simultaneous variation among insects. apparently due to climate or other strictly See also:local causes . He found that the butterflies of the See also:family Papilionidae, and some others, became similarly modified in different islands and groups of islands . Thus, the species inhabiting See also:Sumatra, Java and See also:Borneo are almost always much smaller than the closely allied species of See also:Celebes and the See also:Moluccas; the species or varieties of the small See also:island of See also:Amboyna are larger than the same species or closely allied forms inhabiting the surrounding ;islands; the species found in Celebes possess a See also:peculiar form of wing, quite distinct from that of the same or closely allied species of adjacent islands; and, lastly, numerous species which have.tailed wings in India and the western islands of the See also:Archipelago, gradually lose the tail as we proceed eastward to New See also:Guinea and the Pacific . Many of these curious modifications may, it is true, be due to other causes than climate only, but they serve to show how powerfully and mysteriously local conditions affect the form and structure of both plants and animals; and they render it probable that changes of constitution are also continually produced, although we have, in the See also:majority of cases, no means of detecting them . It is also impossible to determine how far the effects described are produced by spontaneous favourable variations or by the See also:direct See also:action of local conditions; but it is probable that in every case both causes are concerned, although in constantly varying proportions . Selection and Survival of the Fittest as Agents in Naturalization . —We may now take it as an established fact that varieties of animals and plants occur, both in domesticity and in a state of nature, which are better or worse adapted to special climates . There is no See also:positive evidence that the influence of new climatal conditions on the parents has any tendency to produce variations in the offspring better adapted to such conditions.' Neither does it appear that this class of variations are very frequent . It is, however, certain that whenever any animal or plant is largely propagated constitutional variations will arise, and some of these will be better adapted than others to the climatal and other conditions of the locality . In a state of nature, every recurring severe winter or otherwise unfavourable See also:season weeds out those individuals of tender constitution or imperfect structure which may have got on very well during favourable years, and it is thus that the adaptation of the species to the climate in which it has to exist is kept up . Under domestication the same thing occurs by what C . Darwin has termed "unconscious selection." Each See also:cultivator seeks out the kinds of plants best suited to his See also:soil and climate and rejects those which are tender or otherwise unsuitable . The See also:farmer breeds from such of his stock as he finds to thrive best with him, and gets rid of those which suffer from cold, See also:damp or disease . A more or less close adaptation to local conditions is thus brought about, and breeds or races are produced which are sometimes liable to deterioration on removal even to a See also:short distance in the same country, as in numerous cases quoted by C . Darwin (Animals and Plants under Domestication) . The Method of Acclimatization.—Taking into consideration the foregoing facts and illustrations, it may be considered as proved-1st, That habit has little (though it appears to have some) definite effect in adapting the constitution of animals to a new climate; but that it has a decided, though still slight, influence in plants when, by'the process of See also:propagation by buds, shoots or grafts, the individual can be kept under its influence for long periods; and, That great and sudden changes of climate often check See also:reproduction even when the health of the individuals does not appear to suffer . In order, therefore, to have the best chance of acclimatizing any animal or plant in a climate very dissimilar from that of its native country, and in which it has been proved that the species in question cannot live and maintain itself without acclimatization, ,we must adopt some such See also:plan as the following: 1 . We must transport as large a number as possible of adult healthy individuals to some intermediate station, and increase them as much as possible for some years . Favourable variations of constitution will soon show themselves, and these should be carefully selected to breed from, the tender and unhealthy individuals being rigidly eliminated . 2 . As soon as the stock has been kept a sufficient time to pass through all the See also:ordinary extremes of climate, a number of the hardiest may be removed to the more remote station, and the same process gone through, giving protection if necessary while the stock is being increased, but as soon as a large number of healthy individuals are produced, subjecting them to all the vicissitudes of the climate . It can hardly be doubted that in most cases this plan would succeed . It has been recommended by C . Darwin, and at one of the early meetings of the Societe Zoologique d' Acclimatation, at Paris, Isodore See also:Geoffroy St Hilaire insisted that it was the only method by which acclimatization was possible . But in looking through the long See also:series of volumes of Reports published by this society, there is no sign that any systematic See also:attempt at acclimatization has even once been made . A number of foreign animals have been introduced, and more or less domesticated, and some useful exotics have been cultivated for the purpose of testing their applicability to French See also:agriculture or See also:horticulture; but neither in the case of animals nor of plants has there been any systematic effort to modify the constitution of the species, by breeding largely and selecting the favourable variations that appeared . Take the case of the See also:Eucalyptus globulus as an example . This is a Tasmanian See also:gum-See also:tree of very rapid growth and great beauty, which will thrive in the extreme south of France . In the Bulletin of the society a large number of attempts to introduce this tree into general cultivation in other parts of France are recorded in detail, with the failure of almost all of them . But no precautions such as those above indicated appear to have been taken in any of these experiments; and we have no intimation that either the society or any of its members are making systematic efforts to acclimatize the tree . The first step would be, to obtain seed from healthy trees growing in the coldest climate and at the greatest altitude in its native country, See also:sowing these very largely, and in a variety of soils and situations, in a part of France where the climate is somewhat but not much more extreme . It is almost a certainty that a number of trees would be found to be quite hardy . As soon as these produced seed, it should be sown in the same district and farther north in a climate a little more severe . After an exceptionally cold season, seed should be collected from the trees that suffered least, and should be sown in various districts all over France . By such a process there can be hardly any doubt that the tree would be thoroughly acclimatized in any part of France, and in many other countries of central Europe; and more good would be effected by one well-directed effort of this kind than by hundreds of experiments with individual animals and plants, which only serve to show us which are the species that do not require to be acclimatized . Acclimatization of See also:Man.—On this subject we have, unfortunately, very little direct or accurate See also:information .
The general See also:laws of See also:heredity and variation have been proved to apply to man as well as to animals and plants; and numerous facts in the distribution of races show that man must, in remote ages at least, have been capable of constitutional adaptation to climate
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If the human See also:race constitutes a single species, then the mere fact that man now inhabits every region, and is in each case constitutionally adapted to the climate, proves that acclimatization has occurred
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But we have the same phenomenon in single varieties of man, such as the See also:American, which inhabits alike the frozen wastes of See also:Hudson's See also:Bay and Tierra del Fuego, and the hottest regions of the tropics,—the See also:low equatorial valleys and the lofty plateaux of the See also:Andes
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No doubt a sudden transference to an extreme climate is often prejudicial to man, as it is to most animals and plants; but there is every reason to believe that, if the See also:migration occurs step by step, man can be acclimatized to almost any part of the earth's See also:surface in comparatively few generations
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Some eminent writers have denied this
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Sir Ranald See also: 
They only show that acclimatization is in most cases necessary, not that it cannot take place . The best examples of partial or See also:complete acclimatization are to be found where European races have permanently settled in the tropics, and have maintained themselves for several generations . There are, however, two See also:sources of inaccuracy to be guarded against, and these are made the most of by the writers above referred. to, and are supposed altogether to invalidate results which are otherwise opposed to their views . In the first place, we have the possibility of a mixture of native See also:blood having occurred; in the second, there have almost always been a See also:succession of immigrants from the See also:parent country, who continually intermingle with the families of the early settlers . It is maintained that one or other of these mixtures is absolutely necessary to enable Europeans to continue long to flourish in the tropics . There are, however, certain cases in which the sources of See also:error above mentioned are reduced to a minimum, and cannot seriously affect the results; such as those of the See also:Jews, the Dutch at the Cape of Good Hope and in the Moluccas, and the Spaniards in South America . The Jews are a good example of acclimatization, because they have been established for many centuries in climates very different from that of their native land; they keep themselves almost wholly See also:free from intermixture with the people around them; and they are often so populous in a country that the inter-mixture with Jewish immigrants from other lands cannot seriously affect the local purity of the race . They have, for instance, attained a See also:population of millions in such severe climates as See also:Poland and See also:Russia; in the towns of See also:Algeria they have succeeded so conspicuously as to bring about an outburst of See also:anti-semitism; and in See also:Cochin-See also: |