Monster Seminar JAM - Conservation and genetics of a New Zealand icon: The living fossil tuatara, a basal reptile
Presenter: Dr. Fred Allendorf, Division of Biological Sciences, University of Montana
Tuatara (Sphenodontia) are of immense biological significance as the last remaining representatives of one of four extant orders of reptiles. Two species of Sphenodon are currently recognised: the widespread S. punctatus and S. guntheri which comprises a single natural population of ~400 animals on North Brother Island. Tuatara occurred throughout the North and South Islands of New Zealand in prehuman times, but declined over the last 1000-2000 years as human colonists introduced a succession of mammalian predators and deforested more than 70% of the land. Their extirpation from the two main islands by the 1800s left only 35 remnant populations on offshore islands. Seventeen populations now consist of fewer than 100 adults. Tuatara populations vary widely in amounts of genetic variability; expected heterozygosities ranged from 0.13 to 0.80 at five microsatellite loci. Approximately one-half of the variability in heterozygosity is explained by island size. Low genetic variation in S. guntheri on North Brother Island suggests that its taxonomic distinctiveness results primarily from its small island size and additional historical bottlenecks and not from long-term reproductive isolation. Tuatara exhibit a rare form of temperature dependent sex determination (TSD) in which male hatchlings are produced under warmer incubation conditions. Our simulation results predict extinction within 20 generations of based upon current predictions of temperature increases in New Zealand over the next century. Moreover, because tuatara populations are now small and isolated, neither adaptation nor migration are likely to compensate for male skewed sex ratios.
Date and Time:
May 10, 2007,
11:00 am - 12:30 pm