I examined two amphibian communities to assess factors
that may impact amphibian biodiversity. The results suggest
that the potential factors which influence the maintenance
of amphibian biodiversity are multi-faceted and thus,
attempts to understand these factors must reflect these
complexities.
I investigated factors that influenced the susceptibility
of western toad (Bufo boreas), Cascades frog (Rana
cascadae), and Pacific treefrog (Hyla regilla) embryos to
infection with the fungal pathogen Saprolegnia ferax. I
found that there were considerable interspecific differences
in susceptibility of anuran embryos to infection with
Saprolegnia. Interspecific differences can be attributed to
differences in egg-laying behavior and sensitivity to
ambient levels of ultraviolet radiation.
I studied the effect of Saprolegnia on competitive
interactions between larval R. cascadae and H. regilla. The
presence of Saprolegnia differentially affected larval
recruitment of the two species and mediated competitive
interactions. These results suggest that pathogens may have
strong effects on species interactions and thus, when
present may have strong influences on community composition.
I examined population differences in response of native
red-legged frogs (R. aurora) to introduced bullfrogs (R.
catesbeiana). Syntopic R. aurora tadpoles reduced their
activity and increased their refuge-use when presented with
the chemical cues of R. catesbeiana, whereas allotopic R.
aurora did not. Predation by R. catesbeiana was lower for
syntopic R. aurora compared with animals from allotopic
populations. Individuals that are unfamiliar with novel,
introduced organisms may not possess adaptations that would
prevent a negative encounter. In field experiments I
demonstrated that introduced R. catesbeiana, and smallmouth
bass Micropterus dolomieui, influenced the microhabitat use,
growth, and survival of larval and metamorphic R. aurora.
These results illustrate the potential complexities of
interactions between native and exotic species. These
results also stress the importance of understanding the
mechanisms of interactions between native and exotic species
to allow for the persistence of native biodiversity. / Graduation date: 1998
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34071 |
| Date | 29 May 1997 |
| Creators | Kiesecker, Joseph Michael |
| Contributors | Blaustein, Andrew R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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