Dynamics of Intermittent Stream Fish Metacommunities

Community dynamics are driven by factors that operate across multiple scales. Metacommunity perspectives address the role of spatial configuration and connectivity among habitats and the movement of organisms across community boundaries on local and regional processes and patterns of biodiversity. Temperate headwater streams experience unique spatial community dynamics as hydrological conditions oscillate between flowing and non-flowing stages. In an ongoing field study, we surveyed fish assemblages from two intermittent streams in north Texas to investigate metacommunity dynamics and patterns over time. Preliminary ordination analyses (direct and indirect gradient) indicate distinct spatial structuring of fish communities between and within the two stream systems. However, temporal analysis also indicates that despite distinct communities across space, fish assemblages showed similar directions of change over time, generally due to species losses and habitat changes (degradation) over prolonged drought conditions. Observed patterns of alpha, beta, and gamma diveristy in relation to environmental conditions (connectitivity and refugia quality) have strong implications for community resistance and resilience following seasonal disturbances and potentially enhanced future drought scenarios. Further, analyses of elements of metacommunity structure (EMS; coherence, turnover, and boundary clumping) revealed highly variable metacommunity structures over time, however these patterns differed dramatically depending on the scale of investigation.