The controlled assembly of microcosmic communities: the selective extinction hypothesis

Area of Science:

• Ecological dynamics
• Microcosm experiments
• Community assembly

Background:

• Understanding species richness and extinction is crucial for ecological theory.
• Microcosm experiments provide controlled environments to study ecological processes.
• The MacArthur-Wilson equilibrium model describes factors influencing species diversity.

Purpose of the Study:

• To investigate the impact of introduction schedules and microcosm size on species richness and extinction rates.
• To test the applicability of the MacArthur-Wilson equilibrium model in controlled aquatic communities.

Main Methods:

• Forty aquatic communities were established with algae, protozoans, and rotifers.
• Two distinct introduction schedules (6-week and 8-week intervals) were employed.
• Two microcosm volumes (100 ml and 300 ml) were used, with varying invasion rates.

Main Results:

• Species richness increased over time in low invasion rate microcosms.
• Species richness declined in high invasion rate microcosms after an initial increase.
• Extinction rates were disproportionately higher for larger organisms in smaller microcosms.

Conclusions:

• Introduction rates significantly influence species richness dynamics in ecological communities.
• Microcosm size affects extinction patterns, demonstrating selective extinction.
• Observed selective extinction supports predictions of the MacArthur-Wilson equilibrium model.