Biology Reference
In-Depth Information
Table 8.1 General characteristics of metamorphic, paedomorphic, and facultative
salamander life histories
—
cont'd
Metamorphic
Paedomorphic
Facultative
Species may respond to
stressful environmental
factors with precocious
metamorphosis
l
In rare cases, stressful
environmental factors
may cause some species
to metamorphose
(e.g.,
A. mexicanum
)
m,n
Environmental factors
affect the probability of an
individual to express
metamorphosis or
paedomorphosis
b,o,p
a
Wilbur (1980)
.
b
Sprules (1974)
.
c
Denoel, Joly, and Whiteman (2005)
.
d
Duellman and Trueb (1986)
.
e
Armstrong, Duhon, and Malacinski (1989)
.
f
Scott (1993)
.
g
Ryan and Semlitsch (1998)
.
h
Denoel and Joly (2000)
.
i
Bruce (2003)
.
j
Snyder (1956)
.
k
Voss, Kump, Walker, Shaffer, and Voss (2012)
.
l
Wilbur and Collins (1973)
.
m
Smith (1969)
.
n
Voss (unpublished observation).
o
Eagleson and McKeown (1980)
.
p
Semlitsch (1987)
.
growth and is often found where aquatic habitats are ephemeral (
Wilbur,
1980; Wilbur & Collins, 1973
). At the opposite extreme are salamanders that
almost invariably remain paedomorphic until they die as aquatic adults.
Paedomorphic salamanders are associated with isolated and stable aquatic hab-
itats, such as large closed-basin lakes, spring-fed lakes, caldera lakes, and river
systems (
Shaffer, 1984; Sprules, 1974
). In facultative species, metamorphs and
paedomorphs are observed at varying frequencies within the same population.
In such species, it is thought that the ability to express paedomorphosis and
metamorphosis is advantageous when a landscape contains a mixture of
ephemeral and stable aquatic habitats (
Denoel et al., 2005; Semlitsch,
Harris, & Wilbur, 1990; Sexton & Bizer, 1978; Whiteman, 1994; Wilbur,
1980; Wilbur & Collins, 1973
). Facultative life histories are sometimes asso-
ciated with aquatic habitats that may only be permanent for a single year of
reproduction; the fitness advantage must be considerable because it is not un-
common to observe a paedomorphic brood in a cattle-watering tank on an
arid landscape with no permanent ponds (Randal Voss, personal observation).
When facultative species lay eggs in habitats that decline in quality during
the larval period, metamorphosis is initiated in all or some proportion of
individuals in the population (
Semlitsch, 1987; Semlitsch et al., 1990
).
