Plant communities associated with a species at risk: Omus audouini (Coleoptera: Cicindelidae) in upper salt marsh habitat at Boundary Bay, British Columbia

Abstract

Omus audouini Reiche (Coleoptera: Cicindelidae) is a night-stalking tiger beetle species of conservation concern in Canada with only limited distribution in southwestern British Columbia. Occurrence and plant community associations of O. audouini were quantified at one upper salt marsh site in 2018 at three distances from a flood-protection dike. Omus audouini was strongly associated with plant communities 15 m from the dike that were dominated by Douglas aster, Symphyotrichum subspicatum (Nees) G.L. Nesom (Asteraceae). Plant communities transitioned from a diverse assemblage near the dyke to a Douglas aster dominated estuarine meadow at 15 m and then to a halophyte dominated estuarine marsh at 30 m from the dike. In 2019, O. audouini and plants were sampled at four salt marsh sites. Locations where O. audouini was present were correlated with the presence of S. subspicatum. Indicator species analysis showed that S. subspicatum is a statistically significant indicator of the presence of O. audouini. The results are discussed as they relate to conservation of O. audouini in British Columbia. The indicator plant species will be essential in locating previously unknown populations of O. audouini and mapping potential habitat for this species at risk.