Question: 3. Briefly describe the survivorship for each species of
salamander when living alone in the type…


3. Briefly describe the survivorship for each species of
salamander when living alone in the type I, II and III talus and
deep soil from the paragraph below.

Competitive Exclusion as a Factor Influencing the
Distributions of Two Species of Terrestrial
Salamanders.

The salamander Plethodon richmondi shenandoah is
restricted to areas of talus on Hawksbill Mountain, Shenandoah
National Park, Virginia, while P. cinereus inhabits the soil
outside the talus. To test the hypothesis that the former species
is excluded from the soil by the latter species, three enclosures
were constructed in each of four habitats: (i) in talus consisting
only of bare rocks, (ii) in talus where soil has infiltrated
between but not under rocks, (iii) in isolated pockets of shallow
soil within the rocky confines of the talus, and (iv) in deep soil
outside the talus. In each habitat one enclosure contained an
isolated sample of shenandoah, another an isolated sample of
cinereus, and the third a mixture of the two species. The above
testes indicated that: (i) neither species survived the extremely
dry conditions of the bard rocks for more than a week, (ii)
shenandoah expressed a higher survivorship than did cinereus in
this relatively dry habitat, (iii) in the shallow soil shenandoah
had lower survivorship in the presence of cinereus than it did in
isolation, and (iv) in the deep soil shenandoah had poorer
survivorship than cinereus in the mixed species enclosure and
poorer survivorship than its isolated control. P. cinereus
apparently inhibits the presence of shenandoah in areas of soil,
while shenandoah survives better under rocky conditions. However,
the talus is a suboptimal habitat for shenandoah, since its
survivorship in isolated enclosures is significantly better in the
presence of soil. It seems unlikely that salamanders other than
cinereus could exclude shenandoah from the soil or that other
animals exert a strong influence. Predation, diseases, and
parasites also do not appear to exclude shenandoah from areas of
deep soil. Competitive exclusion by cinereus has probably
restricted the distribution of shenandoah to the suboptimal talus
refugium.

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