Original paper

Habitat and phenology of the endangered riffle beetle Heterelmis comalensis and a coexisting species, Microcylloepus pusillus, (Coleoptera: Elmidae) at Comal Springs, Texas, USA

Bowles, David E.; Barr, Cheryl B.; Stanford, Ruth


Habitat characteristics and seasonal distribution of the riffle beetles Heterelmis comalensis and Microcylloepus pusillus were studied at Comal Springs, Texas, during 1993-1994, to aid in developing sound recommendations for sustaining their natural populations. Comal Springs consists of four major spring outlets and spring-runs. The four spring-runs are dissimilar in size, appearance, canopy and riparian cover, substrate composition, and aquatic macrophyte composition. Habitat conditions associated with the respective populations of riffle beetles, including physical-chemical measurements, water depth, and current velocity, were relatively uniform and varied little among sampling dates and spring-runs. However, the locations of the beetles in the respective spring-runs were not well correlated to current velocity, water depth, or distance from primary spring orifices. Factors such as substrate size and availability and competition are proposed as possibly influencing their respective distributions. Maintaining high-quality spring-flows and protection of the physical habitat of Heterelmis comalensis presently are the only means by which to ensure the survival of this endemic species.


conservationhabitat conditionssubstrate availabilitycompetition