Macroinvertebrate communities in ephemeral ponds: Effects of competition, landscape, and hydroperiod on species diversity

Ephemeral ponds in the Northeast are fishless habitats that support unique invertebrate communities.  I examined the effects of competition from salamander larva, hydroperiod, and habitat type on invertebrate species richness in four ephemeral ponds in Northwestern New Jersey within the Delaware Water Gap.  The ponds were sampled every other week over the course of the spring of 2004 using  1 meter long dipnet sweeps. A total of 76 species and 1,977 individuals were collected. Mean species richness by site per visit ranged from 4 to 17.  Individual based rarefaction curves were created using EstimateS, with the two open canopy sites being the most diverse.  Using likelihoods extracted from mixed models, I calculated AICc (Akaike's Information Criterion for small sample size) for six candidate models as well as 10,000 bootstrap model selection frequencies and confidence intervals.  I found that habitat type (open canopy combined with long hydroperiod) had the strongest effect on species richness.  A model using only habitat type also had strong support. Presence or absence of competition from salamander larva had little impact on species richness.  With climate change models predicting changes in precipitation and evapotranspiration, the hydrology of ephemeral ponds is expected to change.   This research supports the idea community level changes in response to climate change may be more complex because of non-linearities arising from the interaction of altered hydrology and landscape characters.