''Oligosoma nigriplantare'', the Chatham Islands skink, is a species of

skink Skinks are a type of lizard belonging to the family (biology), family Scincidae, a family in the Taxonomic rank, infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one o ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Scincidae. It is the sole reptile species found on the

Chatham Islands The Chatham Islands ( ; Moriori language, Moriori: , 'Misty Sun'; ) are an archipelago in the Pacific Ocean about east of New Zealand's South Island, administered as part of New Zealand, and consisting of about 10 islands within an approxima ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, where it occurs on all the major islands except Chatham Island itself. Given the geological history of the Chatham Islands, it is assumed that ''O. n. nigriplantare'' previously occurred on Chatham Island; however, there are no fossil records or historical reports of ''O. n. nigriplantare'' on Chatham Island. Since ''O. n. nigriplantare'' is almost locally extinct on

Pitt Island Pitt Island ( Moriori: , ) is the second largest island in New Zealand's Chatham Islands, with an area of . It lies about to the east of New Zealand's main islands, and about to the southeast of Chatham Island, from which it is separated by ...

as a result of introduced mammals, the presence of introduced mammals on Chatham Island might have resulted in the local extinction of ''O. n. nigriplantare''. On vegetated islands, ''O. n. nigriplantare'' inhabits grassland and shrub habitat, but it also occurs on marine rock stacks with sparse vegetation.Freeman A. (2000). "A preliminary study of habitat use in the skink Oligosoma nigriplantare nigriplantare on Rangitira Island, New Zealand". ''Herpetofauna''. 30, 7–10. Substantial morphological variation (body size, colour and colour pattern) is evident within ''O. n. nigriplantare'', potentially indicating morphological evolution following its colonization of the Chatham Islands. Indeed, ''O. n. nigriplantare'' (up to 91 mm Snout to Vent Length; SVL) has a substantially larger body size than '' Oligosoma nigriplantare polychroma'' (up to 77 mm SVL). Recent genetic studies indicate that ''O. n. nigriplantare'' diverged from ''Oligosoma nigriplantare polychroma'' (its nearest relative) 5.86–7.29 million years ago.Liggins, Chapple, Daughertry and Ritchie (2008). "Origin and post-colonization evolution of the Chatham Islands skink ''(Oligosoma nigriplantare nigriplantare'')". ''Molecular Ecology'' 962-1083vol:17 iss:14 pg: 3290-3305. This pre-dates the emergence date for the Chatham Islands, but indicates that ''O. n. nigriplantare'' colonized the Chatham Islands via overwater dispersal on a single occasion. There is substantial morphological variability evident in ''O. n. nigriplantare'', and a shallow level of genetic differential between islands within the Chatham Islands indicating low gene flow between islands, but not speciation between islands. The level of genetic and morphological divergence between ''O. n. nigriplantare'' and ''Oligosoma nigriplantare polychroma'' might warrant their recognition as distinct species.

References

{{Taxonbar, from=Q3013429 nigriplantare Endemic fauna of New Zealand Reptiles described in 1874 Taxa named by Wilhelm Peters Endemic reptiles of New Zealand