Tunisian Spur-thighed Tortoise
Encyclopedia
The Tunisian spur-thighed tortoise (Testudo graeca nabeulensis) or Nabeul tortoise is a subspecies of spur-thighed tortoises. It was originally described as a new species
in 1990, and even placed in a distinct genus
. The spur-thighed or "Greek" tortoises are usually collectively referred to as Testudo graeca, but this covers a wide variety of subspecies
that have very different ecological and morphological
characteristics and appear to comprise at least 3 phylogenetic lineages. As its name implies, it is found in Tunisia
and nearby Algeria
(but see also "Systematics" below).
. The adult males usually have a carapace that seldom exceeds 13 cm (about 4.5 in), whilst the adult females' carapace is no more than 16.5 cm (some 4 in) long. The geographically closest population of the Testudo graeca group, from Morocco
, is decidedly larger.
These tortoises are among the most brightly coloured taxa of the spur-thighed complex, with a light yellow carapace
with strong black markings in the scute
centres. The plastron also has bold colour pattern. Upon the top of the head, right between the eyes, there is a distinct yellowish spot.
Tunisian spur-thighed tortoises are popular as a pet
due to the attractive coloration and small size. They are a bit more delicate than their larger relatives and though their care is not particularly difficult, they are not ideal pets for those who have no experience at all in keeping tortoises. Coming from tropical semiarid habitat, do not hibernate and an attempt to have them do so will cause fatality. This does actually make their care easier for people in warmer regions, but in temperate
climates they require a well-heated and amply lit terrarium even in winter.
rather than a distinct subspecies however. In any case, separating a form that is in all respects a perfectly ordinary Testudo
, compared to more distinct species such as the Russian tortoise
seems to be gross oversplitting
, making Testudo paraphyletic.
Treatment as a distinct genus is also not supported by mtDNA 12S rRNA haplotype
analysis. However, these results still seem to confirm that the Tunisian spur-thighed tortoise constitutes a well-marked lineage of spur-thighed tortoises. The Testudo graeca complex is likely to be split into (at least) three species in the near future; the eastern Maghreb
populations would remain in T. graeca in this case. Consequently, the scientific name that agrees best with the collected evidence would presently be Testudo graeca nabeulensis. As said above however, apart from the Balkans and Eastern populations of the T. graeca complex the present taxon seems to be quite distinct too. As the former two lineages will eventually come to represent good species, perhaps the Tunisian spur-thighed tortoise might also be regarded as specifically distinct.
There are some unresolved questions regarding the relationships of two populations of spur-thighed tortoises. The Libya
n population was described as Testudo flavominimaralis in the same publication which established "F." nabeulensis. These two are rather similar to each other and as noted above, the separation of Furculachelys is highly dubious on these grounds alone. If the eastern Maghreb tortoises are regarded as a distinct species, it is not unlikely that the Libyan population is united with them as a subspecies.
On Sardinia
, there exists a population of spur-thighed tortoises which share the small size, the yellow head spot, and the contrasting markings with the Tunisian population. Their taxonomic
status is enigmatic, as is their very existence on the island, separated from North Africa
by a considerable stretch of the Mediterranean which tortoises are hardly able to cross. There is a distinct local form of the marginated tortoise
on the island however, and that seems to have originated from a deliberate introduction by humans, perhaps by Greek or Roman landowners in the classical antiquity
. While the local marginated tortoises show evidence of pronounced genetic drift
and may thus justifiably regarded as a subspecies despite the absence of lineage sorting, the spur-thighed tortoises of Sardinia are probably best considered an introduced population not yet worthy of taxonomic separation pending further research.
Nonetheless, because the present taxon may well turn out not to be limited to Tunisia and its immediate surroundings, the alternative common name Nabeul tortoise might actually be preferable. It is a literal translation of the scientific name and honors the Tunisian city of Nabeul
where the type material was collected. Even if this fact were generally known, it is not very likely that anyone would believe that these animals are endemic to a single city.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in 1990, and even placed in a distinct genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. The spur-thighed or "Greek" tortoises are usually collectively referred to as Testudo graeca, but this covers a wide variety of subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
that have very different ecological and morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
characteristics and appear to comprise at least 3 phylogenetic lineages. As its name implies, it is found in Tunisia
Tunisia
Tunisia , officially the Tunisian RepublicThe long name of Tunisia in other languages used in the country is: , is the northernmost country in Africa. It is a Maghreb country and is bordered by Algeria to the west, Libya to the southeast, and the Mediterranean Sea to the north and east. Its area...
and nearby Algeria
Algeria
Algeria , officially the People's Democratic Republic of Algeria , also formally referred to as the Democratic and Popular Republic of Algeria, is a country in the Maghreb region of Northwest Africa with Algiers as its capital.In terms of land area, it is the largest country in Africa and the Arab...
(but see also "Systematics" below).
Description and ecology
The Tunisian spur-thighed tortoise is a relatively small tortoiseTortoise
Tortoises are a family of land-dwelling reptiles of the order of turtles . Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The tortoise...
. The adult males usually have a carapace that seldom exceeds 13 cm (about 4.5 in), whilst the adult females' carapace is no more than 16.5 cm (some 4 in) long. The geographically closest population of the Testudo graeca group, from Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
, is decidedly larger.
These tortoises are among the most brightly coloured taxa of the spur-thighed complex, with a light yellow carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
with strong black markings in the scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
centres. The plastron also has bold colour pattern. Upon the top of the head, right between the eyes, there is a distinct yellowish spot.
Tunisian spur-thighed tortoises are popular as a pet
Pet
A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...
due to the attractive coloration and small size. They are a bit more delicate than their larger relatives and though their care is not particularly difficult, they are not ideal pets for those who have no experience at all in keeping tortoises. Coming from tropical semiarid habitat, do not hibernate and an attempt to have them do so will cause fatality. This does actually make their care easier for people in warmer regions, but in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
climates they require a well-heated and amply lit terrarium even in winter.
Systematics
The genus Furculachelys was established for this taxon and "White's tortoise" (or "Selborne tortoise"). The latter seems to be a local morphPolymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
rather than a distinct subspecies however. In any case, separating a form that is in all respects a perfectly ordinary Testudo
Testudo (genus)
Testudo is a genus of tortoises found in North Africa, western Asia, and Europe. Several species are under threat in the wild, mainly from habitat destruction....
, compared to more distinct species such as the Russian tortoise
Russian Tortoise
The Russian tortoise, Horsfield's tortoise or Central Asian tortoise is a species of tortoise that is a popular pet...
seems to be gross oversplitting
Lumpers and splitters
Lumping and splitting refers to a well-known problem in any discipline which has to place individual examples into rigorously defined categories. The lumper/splitter problem occurs when there is the need to create classifications and assign examples to them, for example schools of literature,...
, making Testudo paraphyletic.
Treatment as a distinct genus is also not supported by mtDNA 12S rRNA haplotype
Haplotype
A haplotype in genetics is a combination of alleles at adjacent locations on the chromosome that are transmitted together...
analysis. However, these results still seem to confirm that the Tunisian spur-thighed tortoise constitutes a well-marked lineage of spur-thighed tortoises. The Testudo graeca complex is likely to be split into (at least) three species in the near future; the eastern Maghreb
Maghreb
The Maghreb is the region of Northwest Africa, west of Egypt. It includes five countries: Morocco, Algeria, Tunisia, Libya, and Mauritania and the disputed territory of Western Sahara...
populations would remain in T. graeca in this case. Consequently, the scientific name that agrees best with the collected evidence would presently be Testudo graeca nabeulensis. As said above however, apart from the Balkans and Eastern populations of the T. graeca complex the present taxon seems to be quite distinct too. As the former two lineages will eventually come to represent good species, perhaps the Tunisian spur-thighed tortoise might also be regarded as specifically distinct.
There are some unresolved questions regarding the relationships of two populations of spur-thighed tortoises. The Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
n population was described as Testudo flavominimaralis in the same publication which established "F." nabeulensis. These two are rather similar to each other and as noted above, the separation of Furculachelys is highly dubious on these grounds alone. If the eastern Maghreb tortoises are regarded as a distinct species, it is not unlikely that the Libyan population is united with them as a subspecies.
On Sardinia
Sardinia
Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...
, there exists a population of spur-thighed tortoises which share the small size, the yellow head spot, and the contrasting markings with the Tunisian population. Their taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
status is enigmatic, as is their very existence on the island, separated from North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
by a considerable stretch of the Mediterranean which tortoises are hardly able to cross. There is a distinct local form of the marginated tortoise
Marginated Tortoise
The Marginated tortoise is a species of tortoise found in Greece, Italy and the Balkans in southern Europe. It is the largest European tortoise, reaching a weight of up to 5 kg and a length of 35 cm . Its shell is oblong and has a notable thickness around the middle of the body...
on the island however, and that seems to have originated from a deliberate introduction by humans, perhaps by Greek or Roman landowners in the classical antiquity
Classical antiquity
Classical antiquity is a broad term for a long period of cultural history centered on the Mediterranean Sea, comprising the interlocking civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world...
. While the local marginated tortoises show evidence of pronounced genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
and may thus justifiably regarded as a subspecies despite the absence of lineage sorting, the spur-thighed tortoises of Sardinia are probably best considered an introduced population not yet worthy of taxonomic separation pending further research.
Nonetheless, because the present taxon may well turn out not to be limited to Tunisia and its immediate surroundings, the alternative common name Nabeul tortoise might actually be preferable. It is a literal translation of the scientific name and honors the Tunisian city of Nabeul
Nabeul
Nabeul is a coastal town in northeastern Tunisia, on the south coast near to the Cap Bon peninsula. It is located at around and is the capital of the Nabeul Governorate...
where the type material was collected. Even if this fact were generally known, it is not very likely that anyone would believe that these animals are endemic to a single city.