Patuxent Wildlife Research Center


Morphological variation of Plethodon shenandoah and Plethodon cinereus in
high-elevation areas of Shenandoah National Park

In order for resource managers at Shenandoah National Park to implement long-term monitoring for the federally-endangered Shenandoah salamander, Plethodon shenandoah, absolute certain identification of the species in the field is critical. During annual surveys, field researchers have observed wide variation in color morphology of Plethodon cinereus in the park, particularly when comparing high elevation areas (>900m; where it co-occurs with P. shenandoah) with other, lower elevation sites (700-900m).  If the main characteristics used to distinguish the species (i.e. stripe width and ventral pigmentation) are phenotypically plastic, the possibility of misidentification presents a major concern for research and monitoring efforts.  Indeed, preliminary monitoring efforts have located individuals in three distant localities that have intermediate morphologies between the two species.

Current statistical methods commonly incorporate uncertainty related to nondetection of a species (so-called ‘false negative’ errors), but recent studies find that bias in estimates of occupancy, colonization, and extinction can be severe when misidentification errors (‘false positives’) occur.  Moreover, the largest bias often occurs when occupancy probabilities are low, such as with rare species like P. shenandoah.  Although analytical techniques exist which can account for this error, accounting for false positives in this way decreases the precision of population parameter estimates; therefore, false positive errors should be dealt with during the design phase of a study when at all possible.  Accounting for this bias is especially important given the consequences for management of endangered species when estimates are inaccurate.  We will incorporate genetic verification with field-based species determination based on a suite of morphological characters (including color morphology of both P.shenandoah and P.cinereus in high-elevation habitats), allowing us to estimate the probability of false positives in previously collected data, as well as develop methods to account for and reduce the probability of false positives in future research and monitoring efforts, which will be implemented beginning in 2013.

sampling a vernal pool
Plethodon shenandoah

amplexed Rana sylvatica
Plethodon cinereus

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