The Role of Local and Upstream Colonisation in Determining Stream Periphyton Metacommunity Assemblages

Area of Science:

• Ecology
• Freshwater Biology
• Community Ecology

Background:

• Stream periphyton is a key model for studying how dispersal influences community patterns.
• Research on periphyton metacommunities at the reach scale is limited, particularly studies comparing local versus upstream propagule sources.

Purpose of the Study:

• To investigate periphyton community assembly by disentangling environmental constraints and dispersal sources at the reach scale.
• To test dispersal hypotheses related to periphyton functional guilds.

Main Methods:

• Experimental setup using plastic silage cover sheets to differentiate between upstream and local propagule sources in three New Zealand streams.
• Collection of periphyton samples after 7, 14, and 25 days to assess biomass, community structure, and functional guild abundance.

Main Results:

• Control samples (local and upstream sources) exhibited 1.5–6 times higher cell densities than plastic-cover samples (upstream only), highlighting the importance of local colonization for biomass.
• Periphyton communities on both sample types converged over time, indicating environmental filters overriding colonization source effects.
• Motile and flagellated taxa successfully reached preferred microhabitats, but other functional guilds did not conform to expected dispersal patterns.

Conclusions:

• Periphyton community assembly at the reach scale is strongly influenced by connectivity, leading to increased biomass and altered community structure.
• The mass effect paradigm is likely the dominant metacommunity process structuring stream periphyton communities at the reach scale.