''Chelonoidis niger donfaustoi'', known as the eastern Santa Cruz tortoise, is a
subspecies of
Galápagos tortoise
The Galápagos tortoise or Galápagos giant tortoise (''Chelonoidis niger'') is a species of very large tortoise in the genus ''Chelonoidis'' (which also contains three smaller species from mainland South America). It comprises 15 subspecies (13 ...
living on
Santa Cruz Island
Santa Cruz Island ( Spanish: ''Isla Santa Cruz'', Chumash: ''Limuw'') is located off the southwestern coast of Ventura, California, United States. It is the largest island in California and largest of the eight islands in the Channel Islands ...
, within the
Galápagos. Until 2015, ''C. n. donfaustoi'' was considered conspecific with the
western Santa Cruz tortoise
The western Santa Cruz tortoise (''Chelonoidis niger porteri'') is a subspecies of Galápagos tortoise endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country ...
, ''C. n. porteri''.
Tortoise populations on Santa Cruz Island
Earlier
mitochondrial DNA studies of tortoises on Santa Cruz showed up to three genetically distinct lineages found in nonoverlapping population distributions around the regions of Cerro Monturra in the northwest, Cerro Fatal in the east, and La Reserva (or La Caseta) in the southwest. Although traditionally classified together, the lineages were all shown to be more closely related to tortoises on other islands than to each other, and thus are thought to be the result of three separate
colonizations of the island.
Cerro Monturra tortoises are most closely related to ''duncanensis'' tortoises from
Pinzón,
Cerro Fatal to ''chathamensis'' from
San Cristóbal,
while Reserva tortoises are closer to the four southern races of
Isabela.
Tortoises are aided in
oceanic dispersal
Oceanic dispersal is a type of biological dispersal that occurs when terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between isla ...
by their ability to float with their heads up, and to survive up to six months without food or water.
Classification
In 2015, ''Chelonoidis niger donfaustoi'' was reclassified as a new subspecies on the basis of genetic and morphological data.
''C. n. donfaustoi'' is the
sister lineage
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A a ...
to ''C. n. chathamensis'' on San Cristóbal, and is part of a
clade that also includes ''C. n. hoodensis'' of
Española and ''C. n. abingdoni'' of
Pinta.
Genetically, ''C. n. donfaustoi'' differs from other tortoises by
allele
An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.
::"The chro ...
frequency at 12
microsatellite
A microsatellite is a tract of repetitive DNA in which certain DNA motifs (ranging in length from one to six or more base pairs) are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organism's genome. ...
loci
Locus (plural loci) is Latin for "place". It may refer to:
Entertainment
* Locus (comics), a Marvel Comics mutant villainess, a member of the Mutant Liberation Front
* ''Locus'' (magazine), science fiction and fantasy magazine
** '' Locus Award ...
, which allowed assignment to the genetically distinct cluster.
''C. n. donfaustoi'' also shares a set of
nucleotide
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecul ...
s distinct from that of ''C. porteri'' on the same Santa Cruz Island and from ''C. n. chathamensis''.
The reclassification reduced the
range
Range may refer to:
Geography
* Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra)
** Mountain range, a group of mountains bordered by lowlands
* Range, a term used to i ...
of ''C. porteri'' to the western and southwestern parts of Santa Cruz Island.
At the same time it confined ''C. n. donfaustoi'' to the eastern part of Santa Cruz Island, with a population size estimated at 250 individuals.
''C. porteri'' was shown to be part of a clade that includes the
Floreana
Floreana Island (Spanish: ''Isla Floreana'') is an island of the Galápagos Islands. It was named after Juan José Flores, the first president of Ecuador
Ecuador ( ; ; Quechuan languages, Quechua: ''Ikwayur''; Shuar language, Shuar: '' ...
and southern Isabela tortoises, as well as specimens reputedly representing
Rábida and
Fernandina.
The subspecies received the
scientific epithet ''donfaustoi'' in honor of Fausto Llerena Sánchez, who devoted 43 years to giant tortoise conservation as a park ranger within the Galapagos National Park Directorate. “Don Fausto” was the primary caretaker of endangered tortoises in captivity.
''C. n. donfaustoi'' is the 15th known tortoise subspecies to be discovered on the islands, with four of those subspecies being extinct. The classification of a new tortoise subspecies was the first in over a century.
Appearance
While similar to other Galápagos tortoises, ''C. n. donfaustoi'' can be distinguished from them by means of
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard o ...
size and shape.
Some Galápagos tortoises are larger than ''C. n. donfaustoi'', with higher anterior opening of the shell.
References
{{Taxonbar, from=Q21179602
Chelonoidis
Subspecies
Turtles of South America
Endemic reptiles of the Galápagos Islands
Reptiles of Ecuador
Reptiles described in 2015