THE LUSITANIAN FAUNA.
Under the Roman Emperor Augustus, the Spanish peninsula was divided into
three provinces, one of which--namely Lusitania--occupied a large
portion of the present area of Portugal. The term "Lusitanian" is
therefore almost synonymous with Portuguese, but it has frequently been
applied by zoologists and botanists in a much wider sense, so as to
vaguely include the extreme south-west of Europe without any definite
limits. Neither do I propose to restrict the term to everything found
within the borders of Portugal. For the sake of convenience, we may
designate as Lusitanian forms those animals and plants which have
migrated to Central, Southern, or Northern Europe from South-western
Europe. They may really be North-west African species, or they may have
originated on land which lay to the west of Portugal, and which is now
mostly buried beneath a deep sea. Nevertheless, we have received them
from the extreme south-western portion of our continent--they have come
to greater Europe from that direction.
In discussing the component elements of the British fauna and flora in
the third chapter, I have already referred to the distinguishing
characters of the Lusitanian migrants and to their distribution. I need
only repeat, therefore, that these are now principally confined to the
south-western portions of the British Islands. The late Edward Forbes
was the first to trace the Lusitanian flora to its native home. In his
classical memoir on the geological relations of the existing fauna and
flora of the British Isles, he laid the foundations of a new method of
research. We are as yet only beginning to realise the far-reaching
conclusions obtainable by a careful study of the geographical
distribution of animals and plants, though the lines of investigation
were indicated by him more than fifty years ago. Forbes was of opinion
that the Lusitanian element in the British flora was of miocene age, and
that it survived the Glacial period on a now sunken land to the
south-west of Ireland. Mr. Carpenter and myself agree in so far that we
are both inclined to look upon this Lusitanian flora and the
accompanying fauna in Ireland as of pre-glacial origin. But I am not
quite satisfied that the Lusitanian migration ceased to come north then.
It may have received a temporary check; but the presence, for instance,
of the Dartford Warbler (_Melizophilus undatus_) in the south-east of
England would seem to indicate that its northward migration took place
in very recent times. It is possible also that the very restricted
occurrence of the Dartford Warbler may imply that it is gradually
withdrawing towards its centre of origin from a former wider range. Such
an eventuality, as we have seen, has actually taken place in a great
number of instances.
It is not only in the British Islands that we perceive the influence of
the Lusitanian element. Scandinavia, Russia--indeed almost every part of
Europe--can boast of some migrants which have originated in
South-western Europe or on the mysterious lands which lay beyond it. As
a rule, however, we notice a marked decrease of Lusitanian species as we
travel eastward from Western Europe. Nevertheless, certain forms have
travelled far beyond the confines of our continent, and we certainly
meet with them in Asia and Northern Africa.
It is remarkable that we are apt to mistake sometimes for Lusitanian
migrants species which are of Oriental origin. In a previous paper I
classed such animals which had apparently originated in South-western
Europe, but had really come from Asia by a circuitous southern route,
with the Lusitanians. However, there is really no reason why the two
should not be kept apart, provided we can discriminate between the
pseudo-Lusitanians and the true ones. I have already indicated in the
last chapter how these pseudo-Lusitanian migrants originated.
Supposing an Oriental species had left Asia for Europe in miocene times,
it would on its arrival in Greece have had to decide between two
courses. It could either advance into the newly-formed Alpine peninsula
and there remain, or at once push on westward into Southern Italy,
Sicily, and Tunis, by means of the old land-connections, and thence into
Southern Spain. The Atlantic communicated at that time with the
Mediterranean across the valley of the Guadalquivir; but that connection
ceased to exist towards the end of the Miocene Epoch, when the Oriental
migrants were free to ramble through Spain and the whole of the North
European plain. I have indicated on a previous occasion (_a_, p. 484)
that the earliest members of the Red Deer migration, which have left
their traces in the caves of Malta, and whose descendants still live in
Corsica, Sardinia, and North Africa, may have found their way to
Northern Europe in this manner. Many other Asiatic mammals probably
reached the British Islands in a similar way.
I cannot call to mind any large species of mammal which we might
reasonably suppose to have originated in South-western Europe. Even
among the smaller ones, few give us any definite clue in this respect.
For instance, the present range of the genus _Myogale_--a small
Insectivore belonging to the Mole family (_Talpidae_)--teaches us
nothing. The two living species show discontinuous distribution, and are
almost confined to Europe. _Myogale_ occurs fossil in French miocene
deposits, but is unknown beyond the confines of our continent. It is
therefore probably of West European origin. The gap between the South
Russian _M. moschata_ and the Spanish _M. pyrenaica_ is bridged over in
so far as we know from fossil evidence that the former had a much wider
range in pleistocene times, being then found in England, Belgium, and
Germany. _Talpa_, too,--to which genus our common Mole belongs,--seems
to be a West European genus, since it occurs in French miocene deposits.
However, it would be difficult to name many more recent genera which
could be included in the area which I propose to investigate in this
chapter. The genus _Lepus_ is probably not of Lusitanian origin, but the
sub-genus _Oryctolagus_--to which our common Rabbit belongs--has no
doubt had its original home in that region. Only two species of _Lepus_
(_Oryctolagus_) are known, one of which--_Lepus lacostei_--has been met
with in French pliocene deposits. The other is the Rabbit (_L.
cuniculus_). Though generally considered to have been introduced into
the British Islands, no reason can be brought forward in favour of such
a supposition, especially as it is known to have spread into Germany in
pleistocene times from South-western Europe. It occurs in France, the
Spanish peninsula, North-western Africa, and on some of the
Mediterranean islands. Its nearest living relatives, as we should almost
expect, are found in South America.
Of the Lusitanian Birds I have already mentioned the so-called Dartford
Warbler (_Melizophilus undatus_), which ranges from the south of England
to the extreme south-west of Europe. A second species occurs on the
Balearic Islands and on Corsica, Sardinia, and Sicily. The Andalusian
Bush-quail (_Turnix sylvatica_) is probably of North African origin,
and has subsequently spread into Southern Spain and Portugal, and
eastward as far as Sicily. It is an instance of a migrant utilising the
old Mediterranean land-connections in the opposite direction from that
described in the last chapter.
Two of our British Wagtails are very closely related, so much so that it
requires a very critical eye to distinguish them even at close range.
They also frequently interbreed. In their distribution, however, there
is a considerable difference between the White Wagtail (_Motacilla
alba_) and the Pied Wagtail (_M. lugubris_). While the former ranges
almost all over Europe and Asia, the latter is a local form resident in
the British Islands, Southern Scandinavia, and France, and a winter
visitor to Spain and North-west Africa. The genus _Motacilla_ is
probably Oriental in its origin, but it seems as if the Pied Wagtail was
a Lusitanian species which had gradually spread northward, only to
return to South-western Europe in severe weather for shelter.
The Bearded Titmouse (_Panurus biarmicus_)--the only representative of
the family _Panuridae_--may possibly be a Lusitanian bird. The fact of
its being absent from Scandinavia and Northern Russia is suggestive of a
southern origin. It is doubtful whether the bird occurs on the south
side of the Mediterranean, but it is common in the south of France and
Spain, and has also been observed in Sicily, Greece, and Asia Minor. In
Central Europe it is found sparingly, and eastward its range extends as
far as Turkestan.
The genus _Fringilla_, which belongs to the great family of the Finches,
appears to be not only of European origin, but, if the range of the
species counts for anything, I should feel inclined to locate their home
in the south-west. Altogether, five species are known. One of them,
viz., _Fringilla teydea_, is confined to the Island of Teneriffe;
another, _F. madeirensis_, is found in Madeira, the Canaries, and the
Azores; a third, _F. spodiogenys_, inhabits North-west Africa. The two
remaining species have a much wider range. _F. coelebs_--the common
Chaffinch--occurs in Europe, while its range extends eastward to Western
Siberia, Persia, and Turkestan. The other--_F. montifringilla_, known as
the Brambling--is more common in Northern Europe, and generally
frequents the more northern latitudes of Asia as far as Japan.
It might be urged that the peculiar little blue Magpie of
Spain--_Cyanopolius Cooki_--should find a place among the Lusitanian
species, since there is no bird like it anywhere else in Europe. But in
Eastern Siberia there lives a bird so closely allied as to be barely
distinguishable from it. Nevertheless, since there are some
distinguishing characters, it has received a distinct name--_C. cyanus_.
This is a most interesting and remarkable case of discontinuous
distribution, which may perhaps be explained by the supposition that the
genus is of Oriental origin, and has died out at its former
headquarters in Southern Asia and all along the line of migration,
except at the extreme limits of the range in both directions--east and
west.
As we go down in the scale of life--among the lower vertebrates and
invertebrates--we meet with a greater number of prominent members of the
Lusitanian migration. The Bullfinch, Dipper, and Chough, which might be
thought to be of Lusitanian origin, are, as I have shown in the last
chapter, Asiatic.
The European snakes seem to be all of eastern origin, unless
_Tropidonotus viperinus_ might be claimed as a Lusitanian form. Of very
great interest from a zoogeographical point of view is our only European
member of the South American and African family _Amphisbaenidae_. This
species--_Blanus cinereus_--is of the size and shape of an ordinary
earth-worm, from which, however, it may be distinguished by its
snake-like wriggling motions. It lives under stones in Spain and
Portugal, North-west Africa, and Greece. It has, therefore, a somewhat
similar distribution to that of many of the animals and plants referred
to in the last chapter. But here we have an animal which has evidently
utilised the old Mediterranean route described on p. 271, from west to
east. Two other species of _Blanus_ inhabit Asia Minor and Syria, but
most of its nearest relations either live in South America or tropical
Africa. In migrating to North and West Africa, its ancestors probably
made use of the land-bridge which spanned the Atlantic in early
Tertiary times. Another Lusitanian Lizard--belonging not to an aberrant
group, but to the typical Lacertidae--is _Psammodromus hispanicus_. It is
rather variable in colour--generally of a brown or green--and grows to a
length at about four or five inches. It occurs throughout the Spanish
peninsula and also in Southern France. One of the handsomest European
Lizards, which reaches almost a foot in length,--of an olive colour with
greenish or mother-of-pearl reflection, and with two yellow stripes
along each side of the body,--is an allied species (_P. algirus_). From
the Spanish peninsula it passes into Southern France and North Africa.
Two other species of the genus are confined to North-west Africa.
It is quite possible that the genus _Pelobates_ is of south-western
origin. Of the two known species of this genus of Toads, one is found in
the Central European plain and the other on the Spanish peninsula and in
France. The closely allied _Pelodytes punctatus_, too, is confined to
this south-western district, and their nearest relations are found in
Mexico. Similarly, the genus to which the Midwife Toad (_Alytes
obstetricans_) belongs may have its original home in that part of
Europe. Of the two species, one is confined to France, Switzerland,
Belgium, and Western Germany, and the other, viz., _Alytes cisternasii_,
to Spain. _Discoglossus pictus_--a well-known and conspicuous Toad in
Southern Europe--inhabits Spain, Algiers, and Tunis, the islands of
Malta, Sicily, Sardinia, and Corsica. From the general range of the
family _Discoglossidae_, as given in Mr. Boulenger's excellent catalogue,
it appears that nowhere in the vast space between China and New Zealand
has any member of the family been discovered. The peculiar genus of
Salamander--_Chioglossa_--is quite confined to the Spanish peninsula.
The Butterflies _Nemeobius lucina_ and _Charaxes jasius_ may also have
had their home in that south-western district. To this migration also
seems to belong the genus _Gonepteryx_, which has so peculiar a range in
the British Islands. The only British species, known as the Brimstone
Butterfly (_Gonepteryx rhamni_), occurs in the south of England and in
the south and west of Ireland. It is met with over the greater part of
Europe, and its range extends into Asia Minor and Northern India, and
then it reappears again in distinct varieties in Japan and the Amur
district. Three other species of _Gonepteryx_ are known from Tibet and
India, and one (_G. cleopatra_) from Southern Europe and Northern
Africa. All the remaining species inhabit the west, viz., Brazil,
Mexico, and Venezuela. That the genus has migrated from America eastward
to Europe appears to be more probable than a migration in the opposite
direction. At any rate, that an exchange of species between the
south-western portion of the Holarctic Region and the Neotropical area
took place is indicated by the fact, not only that a variety of _G.
cleopatra_ has been found in Madeira, but also that the Canary Islands
possess a distinct form of _Gonepteryx_, viz., _G. cleobule_.
Dr. Kobelt has given us such an exhaustive memoir on the characteristic
Mollusca of the different zoogeographical provinces of Europe, that we
are particularly well informed as regards that group of Invertebrates.
He tells us that the group _Torquilla_ of the genus _Pupa_--which is a
small chrysalis-like snail--is especially characteristic of the
Pyrenees, Spain, and Portugal. In a certain measure they replace there
the _Clausiliae_ which, as we have seen in the last chapter, have come
from the east and are almost entirely absent in the south-west of
Europe. Of about seventy species of _Torquilla_, the larger number are
confined to this district, and some, which like _Pupa_ (_Torquilla_)
_granum_, range eastward, have travelled along the old Mediterranean
highway, _via_ Algiers, Sicily and Greece, to Asia Minor. They are still
found along the whole of this route.
Similarly, we are told by the same author, that _Gonostoma_--a group of
the large genus _Helix_--has a number of species in the same
south-western district, while only one, viz., _Helix obvoluta_, occurs
in England and Germany, and two in the Alps. Southward we again find
many representatives crossing over to North Africa, among which _Helix
lenticula_ has a similar range to _Pupa granum_, which I have just
referred to. The Alpine sub-genus _Campylaea_ is quite absent in the
Lusitanian district.
Among our own British testaceous Land Mollusca, several _Helices_,
viz., _Helix pisana_, _ericetorum_, _virgata_, _acuta_, _fusca_,
_rotundata_, _aculeata_, and probably many others, have come to us from
the south-west. The species of _Hyalinia_ are undoubtedly of very remote
origin, and it would be futile at the present state of our knowledge to
speculate as to their home. Some of our species may possibly be of
British origin. _Balea perversa_ is probably a south-western species,
and certainly _Pupa anglica_, which is quite confined to Western Europe.
[Illustration: Fig. 18.--The Spotted Slug (_Geomalacus maculosus_).]
Much more characteristic of South-western Europe, however, than these
land-shells are some of the slugs. The peculiar genus _Geomalacus_ is
almost entirely confined to Portugal. One species, which I have had
several occasions to refer to in illustration of the term "discontinuous
distribution," ranges far beyond the confines of that country. This is
_Geomalacus maculosus_ (Fig. 18), first discovered in the south-west of
Ireland, and more recently also in Portugal. Although careful search has
been made for it in other parts of the British Islands, this slug has
only been found in the portion of Ireland just indicated. Within the
last few years I have taken it, up to a height of over a thousand feet,
on the promontory north of the Kenmare River, also from sea-level up to
a considerable height near Glengariff, and more recently Messrs. Praeger
and Welch discovered it in abundance near the town of Kenmare. But
beyond this rather circumscribed area in the counties of Cork and Kerry
it does not occur (_vide_ Fig. 19). Several Portuguese species of this
interesting genus have since been added to science by Dr. Simroth and
others. Dr. Simroth, too, has promulgated the view that the genus
_Arion_--to which our common brown garden slug belongs--is of Lusitanian
origin. Indeed, the number of species of _Arion_ diminishes as we leave
that province, though one extends beyond the borders of Europe into
Siberia. The same number of species, viz. five, occur in Germany and in
England. _Testacella_--a slug-like mollusc--which lives underground on
earthworms, and of which genus three species, viz. _T. maugei_, _T.
haliotidea_, _T. scutulum_, are known to inhabit the British Islands, is
another Lusitanian animal. All the species are confined to Western
Europe and North Africa; they do not even reach Germany or Switzerland.
[Illustration: Fig. 19.--Map of the British Islands on which the
geographical distribution of _Geomalacus maculosus_ is indicated in
black.]
I have had occasion to mention once before an extremely interesting
genus of blind Woodlouse, viz., _Platyarthrus_. Like _Testacella_, it
lives underground, and also resembles it in its general range. Its
distribution is therefore of particular interest. It is difficult to
conceive that _Platyarthrus_, from its peculiar mode of life could have
crossed any formidable barrier, such as even a narrow straits of sea.
Its occurrence in Spain and North Africa indicates, therefore, that the
Straits of Gibraltar did not exist at the time when it undertook the
migration southward, just as the English Channel and the Irish Sea could
not have been there when it wandered to England and Ireland. The species
which occurs in the south of England has a wide range in Ireland, and
reaches in Scotland its most northern European limit of distribution.
_Platyarthrus_ is only one of the Lusitanian genera of woodlice. In
Ireland--chiefly on the west coast--we also find a brilliantly coloured
Woodlouse, which is absent from Great Britain, viz. _Metoponorthus
cingendus_. It reappears again on the Continent in the south of France.
Its range is therefore suggestive of a Lusitanian origin; and indeed,
when we examine the general distribution of the genus _Metoponorthus_,
we find that out of the forty-four known species, fully one-half are
confined to Western Europe and North Africa.
My friend and colleague, Mr. Carpenter, informs me that among the Irish
Spiders he is acquainted with, the following are to be looked upon as
Lusitanian species:--
Dysdera crocota.
Oonops pulcher.
Tegenaria hibernica.
Theridion aulicum.
Lasaeola inornata.
Agroeca celans.
do. gracilipes.
Teutana grossa.
Cnephalocotes curtus.
Porrhomma myops.
Of the _Coleoptera_, the genera _Trichis_, _Glycia_, and _Singilis_, all
belonging to the Running Beetles (_Carabidae_), are almost confined to
the Spanish peninsula.
The beetles _Rhopalomesites Tardyi_, _Eurynebria complanata_, and
_Otiorrhynchus auropunctatus_ also belong to this fauna, as also the
Earthworms _Allolobophora veneta_ and _A. Georgii_, and the Millipede
_Polydesmus gallicus_.
It will be evident to every one from these few instances of Lusitanian
species, that somewhere in South-western Europe and North-western
Africa, and also, perhaps, in a larger now submerged western land-area,
there existed an active centre of development, from which animals spread
in all directions.
If the presence of _Platyarthrus_ in North-west Africa proves that the
Straits of Gibraltar had come into existence after its southward
migration, it also suggests that the ancestral home of this woodlouse
was in the Spanish peninsula. Whether this supposition is correct or
not, does not affect the Straits of Gibraltar problem, for in a
migration northward into Spain from Morocco a land-connection would be
equally necessary. Almost every group of vertebrates and invertebrates
furnishes instances of species which must have crossed the Straits on
dry land. Many naturalists have come to this conclusion, and have
clearly expressed their views on the subject. At the commencement of the
present period, says Mr. Bourguignat (p. 354), the north of Africa was a
peninsula of Spain, the Straits of Gibraltar did not exist, and the
Mediterranean communicated by the Sahara with the Atlantic.
The faunas of North-west Africa and the south-western portion of our
continent are so closely related, that an uninterrupted intercourse by
land must have existed for a very long period. The Mediterranean,
however, throughout the Tertiary period--at any rate since miocene
times--must have had almost constant communication with the Atlantic.
According to Professor Suess, this was the case. The Atlantic was joined
with the Mediterranean across the valley of the Guadalquivir during the
Miocene Epoch, so that Andalusia must have belonged to North Africa in
those days. The Straits of Gibraltar are supposed to have been formed in
the next epoch. I have already expressed my disagreement with that
theory from a zoogeographical point of view. The old Guadalquivir
connection probably persisted much longer,--though interrupted by
temporary periods of a partial retreat--so as to uncover sufficient land
to allow of an interchange during miocene as well as pliocene times
between the European and North African faunas. It is in this way,
perhaps, that some of the members of the Alpine fauna have reached Spain
by way of Corsica, Sardinia, and North-western Africa, and _vice versa_.
The Balearic Islands were then connected with Spain; and we find there
many curious survivals which have long ago become extinct on the
mainland.
That the Straits of Gibraltar are only of recent formation has been
suggested on zoogeographical evidence by Bourguignat, Simroth, Kobelt,
and many others. Dr. Kobelt believes that the former land-connection
between the south of Spain and Morocco was much wider than is generally
assumed, and that the coast-line stretched from Oran in Algeria straight
across to Cartagena in Spain (_b_, ii., p. 228).
My allusions to the lands lying beyond the Lusitanian province, refer
chiefly to the Canary Islands and Madeira. Whatever doubts Dr. Wallace
had on the subject of their former connection with Morocco, it cannot be
denied that they used to be of much larger extent, especially in miocene
and pliocene times. It seems extremely probable that these islands
formed part of the mainland of North Africa until comparatively
recently, and that they are the last traces of a sunken continent which
united Africa and South America. A discussion of this problem, however,
must be deferred, as it is a complicated one, and one which would lead
me altogether outside the scope of this little volume. I hope I shall
have an opportunity to publish my views on this subject before long,
meanwhile the reader must content himself with this mere statement.
During the greater portion of the Miocene, and I think for part of the
Pliocene Epoch too, the advance of the Lusitanian species eastward was
barred on the continent of Europe by an arm of the sea which stretched
northward along the Rhone valley from the Mediterranean. The Lusitanian
forms which originated in Southern Spain were able to travel east during
these times by way of North-west Africa, Sicily, Southern Italy, and
Greece; it is possible that some may have reached the Alps in this
manner, and Eastern Europe generally. That the Lusitanian centre was
never a very active one compared with, for instance, the Oriental is
indicated by many distributional facts. It is difficult to understand,
however, why the Oriental species, on the whole, have migrated so far
west, while few Lusitanians have gone very far east. This seems to have
been noted particularly in the case of the flora. Mr. Bonnet drew
attention to the fact that in Tunis there are none of the absolutely
characteristic plants of Morocco and Spain, while the Oriental flora is
represented by a good many species. Lusitanian species have spread
chiefly southward into North Africa, and northward into France, the
British Islands, and even Scandinavia. As I have mentioned in the third
chapter, there are a good many species of Lusitanian origin in the
British Islands. However, we have only a mere remnant of what we ought
to have, had the climate been less trying. It is probable, too, that the
submergence destroyed a good many plants and the insects dependent on
them. That the Lusitanian fauna is very ancient in the British Islands
is proved by the fact of the discontinuous distribution of so many
species. A greater number survived in Ireland than in England.
[Illustration: Fig. 20.--The Strawberry-tree (_Arbutus unedo_) in its
native habitat in the south-west of Ireland. (From a photograph by
Robert Welch.)]
[Illustration: Fig. 21.--The Irish Spurge (_Euphorbia hiberna_) in its
native habitat in the south of Ireland. (From a photograph by Robert
Welch.)]
Altogether--and this was strongly urged by Edward Forbes--the Lusitanian
element is the oldest of the components of our fauna, and it must have
poured into the British Islands for many geological periods almost
without cessation. The same author, in his classic essay, refers
especially to the Lusitanian flora, two prominent members of which are
the British plants, _Arbutus unedo_ (Fig. 20, p. 305) and _Euphorbia
hiberna_ (Fig. 21, p. 306). The former has a wide range in the
Mediterranean region, and occurs in the British Islands only in the
south-west of Ireland. The Spurge, on the other hand, is also found in
the south-west of England, besides Ireland and Southern Europe.
SUMMARY OF CHAPTER VII.
The term "Lusitanian" is in this chapter employed in the wide sense, as
indicating the South-west of Europe and North-western Africa. From this
centre, and probably also from a now sunken land which lay to the west
of it, issued a fauna and flora of which we have abundant evidence in
our own islands, especially in Ireland. Edward Forbes held that the
Lusitanian element of the British flora was of miocene age, and that it
survived the Glacial period in this country.
At the time when the Straits of Gibraltar did not exist, and when there
was free land communication between Asia Minor, Greece, and Tunis, many
Oriental species migrated westward by this ancient Mediterranean route
as far as Spain. They would then have invaded the more central parts of
Europe from the south-west, without however being of Lusitanian origin.
Of the true Lusitanian mammals a typical example is the Rabbit. Then we
have a few birds and several interesting reptiles and amphibians. The
genus to which the Brimstone Butterfly belongs is also of south-western
origin. A number of Mollusca are mentioned which from their range
likewise indicate a Lusitanian origin. Most of our British Slugs and
many of our larger Snails belong to this group.
All these are merely a small remnant of what we received from
South-western Europe during the Miocene and Pliocene Epochs. But they
spread into many parts of Europe, and a few even crossed into Asia. The
antiquity of the Lusitanian element in our fauna is especially indicated
by the frequent recurrence of "discontinuous distribution" among the
species belonging to that section.