Behavioural differences and interactions between two sessile bivalves forming mixed-species assemblages

The invasive zebra mussel, Dreissena polymorpha (ZM), established in Europe for a long time, has recently been joined and commonly outcompeted by new invader, the quagga rostriformis bugensis (QM). To identify factors contributing to this displacement, we studied behavioural differences between species: aggregation, movement, responses conspecifics, congeners their alarm cues. Compared ZM, QM were more aggregated less motile, crawling shorter distances time at slower speed. Conversely, exhibited nonlocomotor movements. Both species burrowed showed movements response conspecific heterospecific They also moved presence of ZM delayed locomotion movements, whereas started earlier both Mussel living heterospecifics resembled those In mixed-species aggregations, attached conspecifics often than shells, nonselective. summarize, are mobile, selective regarding attachment site ZM. This allows perform better assemblages spending energy on relocation overgrowing higher extent vice versa. responded signals, which is helpful assemblages, particularly novel areas occupied these species. Nevertheless, similar cues suggest negative interaction congeners.