Gymnophthalmus underwoodi Grant, 1958, Barbados. Gymnoph-thalmus underwoodi is actually a complex of species, or independent evolutionary units. Some populations of Gymnophthalmus underwoodi are bisexual, and others are unisexual, all-female species (parthenogens). The species was described from a series of female specimens from Barbados; no males were found. It was later proved that the Caribbean populations and some South American populations are parthenogenetic, reproducing without males or sperm.
Charles J. Cole and others (1983, 1990) and Laurence M. Hardy and others (1989) showed that this species is a product of hybridization. They suggested that G. underwoodi evolved from G. speciosus and a yet-undescribed Gymnophthalmus. Cole not only predicted what the undiscovered parent species would look like, he also predicted the specific arrangement of its 22 pairs of chromosomes and the nature of 33 of the unknown species' proteins!
Later, Cole and others (1993) reported the missing ancestor of G. underwoodi to be G. cryptus, a bisexual species described in 1992 from the Orinoco River drainage in Venezuela. After it arose in the upper Orinoco River watershed, G. underwoodi dispersed throughout the Guiana region and reached islands in the West Indies. Because multiple hybridization events could have occurred, there may be other clonal lineages of G. underwoodi that exist in a complex of species. Experts presume that more cryptic species exist that have not been described by 2002.
OTHER COMMON NAMES None known.
These are small microteiids with a snout-vent length of 1.4-1.7 in (3.6-4.3 cm). The tail is about 1.5 times body length. The body is cylindrical, and the dorsal and ventral scales are smooth. The limbs are fully developed but small, with four fingers and five toes. These lizards usually are shiny bronze or olive on back, darker on the flanks, with a light dorsolateral stripe. The tail may be the same color as the body or range from bluish to orange or red.
The Gymnophthalmus underwoodi species complex occurs in the Guianan region of South America and in Trinidad and other islands of the West Indies.
These lizards are found in open types of tropical forest in leaf litter or grass. They are often found in microhabitat patches exposed to direct sunlight.
Gymnophthalmus underwoodi, like almost all gymnophthalmids, is a secretive denizen of leaf litter, and its behavior has never been studied. Because their diet consists of small surface-dwelling arthropods, it is likely these lizards actively search for their prey among leaf litter and under logs and other objects. They do not obviously bask, but they do occur mostly in leaf litter receiving direct sunlight. These lizards are part of a large group of lizards that are heliothermic, the Teoidea, almost all of which are strictly diurnal and not territorial.
In a study of an Amazonian lizard community, Vitt and Zani (1991) documented several orders of small insects in the diet of this species, specifically dermapterans, collembolans, and dipterans.
Like other microteiids, this species lays eggs. Clutch size may range from one to four with an average clutch size of two.
Not listed by the IUCN. Lack of knowledge about the ecology of this species complex impedes fully informed decisions about conservation needs. Threats include habitat destruction, and it will be difficult to assess the importance of habitat loss to cryptic species in the G. underwoodi complex until the distributions of different forms are understood.
SIGNIFICANCE TO HUMANS None known. ♦
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