[acn-l] sampling question regarding negative occurrence data
Chris Herrington (Herrington_C at earth.ci.austin.tx.us)
Tue, 09 Sep 1997 13:30:57 -0500
The Jollyville Plateau salamander, Eurycea sp. occurs in springs and
spring-runs in Travis and Williamson Counties, Texas. The City of
Austin has been asked to provide data which could be used to understand
the limitations of the neotenic species and to identify potential
threats to its viability. We are currently surveying 8 sites to
determine the habitat and water quality factors that potentially affect
the salamander surface populations. Two other sites have been
identified by a field biologist as sites that look suitable for
salamanders but where none have been found and where development impacts
have been observed. The sites are spring-fed and salamanders have been
found downstream in these tributaries. Is it appropriate to study these
sites? With the exception of the reliance of the populations on
thermally stable, perennial spring habitats, we know little about the
factors that led to the current distribution of the salamander. We are
also uncertain about the occurrence or extent of movement of individuals
from site to site. We can not determine the cause(s) for salamander
absence at these sites. (Potential causes include habitat
unsuitability, an inability to colonize the site due to biogeography,
and an inability to recolonize the site following extirpation.) We may
however find some differences between the sites where salamanders are
present and those where they are not. If differences are found, these
differences might be the focus of future studies. We have the personnel
and budget to sample the additional sites. The City of Austin would
appreciate any advice on this question.
Please reply to Chris Herrington
email: Herrington_c at earth.ci.austin.tx.us