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Testudo (genus)
Encyclopedia
Testudo is a genus
of tortoise
s found in North Africa
, western Asia, and Europe. Several species are under threat in the wild, mainly from habitat destruction
.
They are small tortoises, ranging in length from 7 cm to 35 cm and in weight from 0.7 kg to 7 kg, although the extinct T. atlas
reached 2.5 m. Like most tortoises, they are herbivorous.
and taxonomy
of Testudo is notoriously problematic. Highfield & Martin commented:
Since then, DNA sequence
data has increasingly been utilized in systematics, but in Testudines (turtles and tortoises) its usefulness is limited: In some of these, at least mtDNA is known to evolve
more slowly in these than in most other animals. Paleobiogeographical considerations suggest that the rate of evolution of the mitochondrial 12S rRNA gene is 1-1.63% per million years for the last dozen million years or so in the present genus and ntDNA evolution rate has been shown to vary strongly even between different population of T. hermanni; this restricts sequence choice for molecular systematics and makes the use of molecular clock
s questionable.
Conventionally, five species are placed here:
The first two are more distinct and ancient lineages than the closely related latter 3 species. It was argued that T. horsfieldii belonged in a new genus (Agrionemys) on the basis of the shape of its carapace
and plastron, and its distinctness is supported by DNA sequence
analysis. Likewise, a separate genus Eurotestudo has recently been proposed for T. hermanni; these three lineages were distinct by the Late Miocene
as evidenced by the fossil record. Whether these splits will eventually be accepted remains to be seen. The genus Chersus has been proposed to unite the Egyptian and Marginated Tortoises which have certain DNA sequence similarities, but their ranges are (and apparently always were) separated by their closest relative T. graeca and the open sea and thus, chance convergent
haplotype
sorting would better explain the biogeographical discrepancy.
On the other hand, the Greek Tortoise is widespread and highly diverse. In this and other species, a high number of subspecies
has been described, but not all generally accepted, and several (such as the "Negev Tortoise" and the "Dwarf Marginated Tortoise") are now considered to be local morphs. Some, such as the Tunisian Spur-thighed Tortoise
, have even been separated as a separate genus Furculachelys, but this is not supported by more recent studies. However, it is likely that the "Greek" Tortoise will be split into two or more species in the near future.
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...
of tortoise
Tortoise
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...
s found in 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...
, western Asia, and Europe. Several species are under threat in the wild, mainly from habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
.
They are small tortoises, ranging in length from 7 cm to 35 cm and in weight from 0.7 kg to 7 kg, although the extinct T. atlas
Testudo atlas
Colossochelys atlas, formerly known as Testudo atlas, and originally described as Geochelone atlas, is an extinct species of cryptodire turtle from the Pleistocene period, about 2 million years ago...
reached 2.5 m. Like most tortoises, they are herbivorous.
Systematics
The systematicsSystematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
and taxonomy
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...
of Testudo is notoriously problematic. Highfield & Martin commented:
Synonymies on Testudo are notoriously difficult to compile with any degree of accuracy. The status of species referred have undergone a great many changes, each change introducing an additional level of complexity and making bibliographic research on the taxa extremely difficult. Most early and not a few later checklists contain a very high proportion of entirely spurious entries, and a considerable number of described species are now considered invalid - either because they are homonyms, non-binomial or for some other reason.
Since then, DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data has increasingly been utilized in systematics, but in Testudines (turtles and tortoises) its usefulness is limited: In some of these, at least mtDNA is known to evolve
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
more slowly in these than in most other animals. Paleobiogeographical considerations suggest that the rate of evolution of the mitochondrial 12S rRNA gene is 1-1.63% per million years for the last dozen million years or so in the present genus and ntDNA evolution rate has been shown to vary strongly even between different population of T. hermanni; this restricts sequence choice for molecular systematics and makes the use of molecular clock
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...
s questionable.
Conventionally, five species are placed here:
- Russian TortoiseRussian TortoiseThe Russian tortoise, Horsfield's tortoise or Central Asian tortoise is a species of tortoise that is a popular pet...
or Horsfield's Tortoise, Testudo horsfieldii - Hermann's Tortoise, Testudo hermanni
- Greek TortoiseGreek TortoiseThe spur-thighed tortoise or Greek tortoise is one of four European members of the Testudinidae family of tortoises...
or Spur-thighed Tortoise, Testudo graeca- "Maghreb Tortoise", Testudo (graeca) graeca
- Greek Tortoise, Testudo (graeca) ibera
- "Persian Tortoise", Testudo (graeca) zarudnyi
- Kleinmann's TortoiseKleinmann's TortoiseKleinmann's Tortoise , often called Egyptian Tortoise and occasionally Leith's Tortoise. It is a critically endangered neck-hiding tortoise. Once more widespread, its numbers are now dwindling...
or Egyptian Tortoise, Testudo kleinmanni - Marginated TortoiseMarginated TortoiseThe 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...
. Testudo marginata
The first two are more distinct and ancient lineages than the closely related latter 3 species. It was argued that T. horsfieldii belonged in a new genus (Agrionemys) on the basis of the shape of its 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...
and plastron, and its distinctness is supported by DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
analysis. Likewise, a separate genus Eurotestudo has recently been proposed for T. hermanni; these three lineages were distinct by the Late Miocene
Late Miocene
The Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....
as evidenced by the fossil record. Whether these splits will eventually be accepted remains to be seen. The genus Chersus has been proposed to unite the Egyptian and Marginated Tortoises which have certain DNA sequence similarities, but their ranges are (and apparently always were) separated by their closest relative T. graeca and the open sea and thus, chance convergent
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
haplotype
Haplotype
A haplotype in genetics is a combination of alleles at adjacent locations on the chromosome that are transmitted together...
sorting would better explain the biogeographical discrepancy.
On the other hand, the Greek Tortoise is widespread and highly diverse. In this and other species, a high number 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...
has been described, but not all generally accepted, and several (such as the "Negev Tortoise" and the "Dwarf Marginated Tortoise") are now considered to be local morphs. Some, such as the Tunisian Spur-thighed Tortoise
Tunisian Spur-thighed Tortoise
The Tunisian spur-thighed tortoise 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...
, have even been separated as a separate genus Furculachelys, but this is not supported by more recent studies. However, it is likely that the "Greek" Tortoise will be split into two or more species in the near future.