''Lepidodactylus listeri'', also known commonly as Lister's gecko or the Christmas Island chained gecko, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout the world. They range from . Geckos ar ...

, a

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Gekkonidae Gekkonidae (the common geckos) is the largest family of geckos, containing over 950 described species in 64 genera. Members of the Gekkonidae comprise many of the most widespread gecko species, including house geckos (''Hemidactylus''), tokay ge ...

, endemic to

Christmas Island Christmas Island, officially the Territory of Christmas Island, is an Australian external territory comprising the island of the same name. It is located in the Indian Ocean, around south of Java and Sumatra and around north-west of the ...

in the Indian Ocean. It is currently

extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as known only by living members kept in captivity or as a naturalized population outside its historic range due ...

Geographic range

''L. listeri'' is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Etymology

Both the

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''listeri'', and one of the common names, Lister's gecko, are in honour of British naturalist

Joseph Jackson Lister Joseph Jackson Lister FRS FRMS (11 January 1786 – 24 October 1869) was an amateur British opticist and physicist and the father of The 1st Baron Lister. Ancestry In 1705, Thomas Lister, a farmer and maltster, of Bingley, Yorkshire, Englan ...

.xiii + 296 pp.

Description

Lister's gecko is a brown

growing to a snout-vent length (SVL) of . It has a broad, pale fawn/grey

vertebral The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordates ...

stripe which expands to cover the top of the head and matches the colour and pattern of the tail. It has a whitish belly. The body is covered with small, smooth scales. ''L. listeri'' was most abundant in primary

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

on the plateau, but also occurs in disturbed secondary

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

growth. It was absent from mined areas on the island.Cogger HG, Sadlier RA (1999). ''The terrestrial reptiles of Christmas Island – a reappraisal of their status''. Sydney: Australian Museum.

Evolutionary relationships

The closest relatives of ''L. listeri'' are species of ''

Lepidodactylus ''Lepidodactylus'' is a large genus of geckos, commonly known as scaly-toed geckos and closely related to house geckos or dtellas. Geographic range Species in the genus ''Lepidodactylus'' are found from Southeast Asia to Indo-Australia and O ...

'' belonging to the '' lugubris'' group, native to the Mollucas and the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

, with the estimated divergence between ''L. listeri'' and the ''lugubris'' group taking place around 26 million years ago. Unlike '' L. lugubris'', which can be

triploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei ( eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contain ...

and reproduce through

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

, ''L. listeri'' is a

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

, sexually reproducing species.

Decline

''L. listeri'' was considered to be generally common in 1979, and was widespread across the island, but population declines were noted by researchers starting in 1998. Further decline was noted in 2004 and in 2008. By 2009, it was recognized that the species was in imminent danger of extinction, and a captive breeding program was established. The last record of ''L. listeri'' in its native habitat on Christmas Island was in October 2012. The decline of ''L. listeri'' was concurrent with the widespread decline of most endemic mammal and reptile species on Christmas Island, and it is considered that this decline was the result of a common cause, or a combination thereof. The causes of this decline are not well understood. However it is believed that predation by introduced species, particularly the wolf snake (''

Lycodon capucinus ''Lycodon capucinus'', also known as the Oriental wolf snake, is a species of colubrid snake, which is commonly found in the Indo-Australian Archipelago. Named after their enlarged front teeth, which gives them a muzzled appearance similar to can ...

''), may have played a significant role. The wolf snake was introduced around 1982, which is within the timeframe that the population decline began.

Conservation efforts

Prior to the extirpation of this species from Christmas Island, 43 individuals were taken into captivity, starting in August 2009, in order to establish a breeding population. This proved successful with a total population of over 1500 individuals as of July 2022. However, reintroduction is unlikely to occur in the near future, invasive threads are not yet controlled on Christmas Island, and assisted colonization is not yet feasible due to widespread gecko '' L. lugubris''. The genome of the ''L. listeri'' was sequenced in 2022 (along with the Christmas Island blue-tailed skink), making it one of the earliest chromosome-level gecko genomes. The genome was genetically diverse, reflective of large historical population sizes. Despite the captive population being founded from just 43 individuals, there was not evidence of inbreeding in the genome.

Geographic range

Etymology

Description

Evolutionary relationships

Decline

Conservation efforts

See also

References

Further reading