Conservation of endangered species - Ecological Applications: Toward a Sustainable World - page 128

5.5.1 Genetic rescue
of the Florida panther

The last remaining population of the Florida panther ( Puma concolor coryi ) became
so small that genetic variation was remarkably low and deleterious alleles occurred
at high frequency (or were 'fi xed' - showing no variation at all). A suite of traits,
doubtless a result of this genetic makeup and rarely seen in other subspecies of the
Puma genus, includes unilateral undescended testes, a kinked tail, a 'cowlick' pattern
on the back, and the poorest semen quality of any cat species (Roelke et al., 1993).
Managers decided to translocate individuals from another subspecies, the Texas
cougar ( Puma concolor stanleyana ), in an attempt to eliminate deleterious variants
and restore more normal levels of genetic variation.
Eight female Texas cougars were introduced in 1995, and fi ve of these produced
offspring with resident Florida panther males. Some of the offspring have also mated
with resident panthers and now about 20% of Florida panthers have some cougar
ancestry. Individuals with cougar ancestry show dramatic reversals in the frequency
of undesirable traits - kinked tails reduced from 88% to 7%, the cowlick trait
reduced from 93% to 24% and abnormal testes development from 68% to zero (Land
et al., 2001). Only one animal with cougar descent has been tested for semen quality,
but this is at least as good as the average for cougars.
It cannot be certain that the Florida panther would have gone extinct without
this genetic rescue, or that the population is now completely safe. But the signs are
good that the probability of extinction has been reduced. Under less urgent circum-
stances, managers would have shied away from diluting the Florida panther gene
pool with that of a different subspecies. But in desperate times, this genetically
desperate measure can be fairly justifi ed.

5.5.2 The pink
pigeon - providing a
solid foundation

The pink pigeon ( Columba mayeri ), once w idespread on the island of Mauritius,
recovered from only nine or ten birds in 1990 to 355 free-living individuals (plus
more in captivity) by 2003. The recovery program depended on captive-breeding on
Mauritius and overseas. In captivity, the aim has been to manage matings to retain
high levels of genetic diversity and to minimize inbreeding. The captive population
was originally descended from just 11 founder individuals but this was augmented
during 1989-94 by adding to the captive gene pool 12 further founder individuals
(of fspr ing from 12 of the 13 remaining wild individuals).
Once captive-reared birds are released into the wild the incidence of inbreeding
depression is not easy to control - the tactic of releasing a large number of individu-
als probably provides the greatest chance of success. Between 1987 and 1997, 256
birds were reintroduced as three subpopulations on Mauritius - wherever possible
selecting birds with minimal inbreeding (based on records in breeding 'stud topics')
and releasing them in groups with good representation of the different founder
ancestries. All birds were banded for unique identifi cation.
The genetics and ecological success of both captive and wild populations have
been carefully monitored. This database means we can evaluate the impact of
inbreeding on survival and reproduction under the controlled situation of captive
rearing and also in the more risky circumstances of the wild. Inbreeding reduces
egg fertility, and survival of nestlings (up to 30 days post-hatching; Figure 5.10), as
well as juveniles and adult birds, but effects are only strongly marked in the most
inbred birds. Highly inbred birds are generally more dramatically affected in the
wild than in captivity, where threats can be more carefully controlled.