Blackburn, D.G. and L.J. Vitt (1992). Reproduction in viviparous South American lizards of the genus Mabuya. In: Reproductive Biology of South American Vertebrates:
Aquatic and Terrestrial, pp. 150-164 (W. Hamlett, ed.).
Springer-Verlag, New York.
Conclusion: Reproductively, South
American Mabuya are among the most extraordinary of squamate
reptiles. Not only have these scincid
lizards evolved a degree of placentotrophy that exceeds that of all other known
squamates, but they have converged strongly on a pattern usually assumed to be
confined to eutherian mammals.
Characteristics of this reproductive pattern include viviparity, a
lengthy gestation period, ovulation of small ova, formation of chorioallantoic
placentae with chorionic areolae and a placentome, and placental provision of
virtually all of the nutrients for development. The independent evolution of such features among mammals and
lizards represents one of the most striking cases of evolutionary convergence
in reproductive specializations to be documented among terrestrial vertebrates
(Blackburn, 1991).
Aside from their similarities to eutherians, however, South
American lizards of the genus Mabuya
are highly worthy of study in their own right. These lizards represent an extreme in the spectrum of reptilian
reproductive features, and their specializations appear to be of functional
significance in the environments that they inhabit (Vitt and Blackburn, 1983,
1991; Vitt, in press). The
extent of intra-generic diversity in reproductive mode, placentation, and fetal
nutritional mode suggests Mabuya to be a model taxon for inquiries into
the evolution of viviparity and placentotrophy, as well as the evolution of
structural – functional complexes, such as is represented by the placenta.
Unfortunately, survival of at least some of the South American
species of Mabuya is now
threatened over wide portions of their ranges.
For example, during the past ten years of habitat destruction in
Pernambuco, M. heathi has become increasingly scarce, and the range of M.
bistriata undoubtedly is being diminished by devastation of the Amazonian
rainforest. Extinction of these
remarkable species would be an incalculable loss, and protection and
maintenance of the genus Mabuya throughout South America is of the
utmost urgency.
Reprints: daniel.blackburn@mail.trincoll.edu