Potential extinction through competition of two species of terrestrial salamanders

Jaeger, Robert

Brief Description: The research presented here concerns the relationship between the distributions of the plethodontid salamanders Plethodon cinereus cinereus (Green) and P. richmondi shenandoah Full Description: On the north-facing slope of Hawksbill Mountain, Shenandoah National Park, Virginia, Plethodon richmondi shenandoah is primarily restricted to areas of talus, while Plethodon cinereus cinereus is abundant in the deeper soil surrounding these talus slopes. Quadrats sampled during two separate years from each of the habitats show that cinereus is abundant in the soil but fails to enter the talus. P. r. shenandoah occurs infrequently in the soil outside the talus but is most abundant in isolated pockets of soil contained within the talus. In similar quadrats at Blackrock Mountain, where shenandoah is not known to occur, cinereus is again abundant in the soil but is not found in the talus. The talus, of Pleistocene age, appears to be in the process of disintegration with cinereus replacing shenandoah where soil erodes into the rocks. Such data have led to the following hypothesis concerning the distributions of the two species of salamanders: (1) cinereus is prevented from entering the talus by some environmental factor other than competitive exclusion by shenandoah, since it is absent from talus independent of the presence or absence of shenandoah; (2) shenandoah is competitively excluded from the soil outside of the talus by cinereus, since it is usually absent from this soil but common in comparable patches of soil isolated within the rocky confines of the talus; (3) the talus is a suboptimal habitat for shenandoah, since that species is primarily confined to small, scattered patches of soil and not comparatively successful in the larger soilless areas; and (4) shenandoah is faced with potential extinction due to the erosion of soil into its talus refugium followed by a subsequent encroachment of cinereus, and due to the paucity of isolated pockets of soil which are the centers of its distribution.

Potential extinction through competition of two species of terrestrial salamanders

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