Passive sampling hypothesis did not shape microbial species–area relationships in open microcosm systems

Abstract

The passive sampling hypothesis is one of the most important hypotheses used to explain the mechanism of species–area relationships (SAR) formation. This hypothesis has not yet been experimentally validated due to the confusion between passive sampling (a larger area may support more colonists when fully sampled) and sampling effects (more sampling effort will result in increased species richness when sampling is partial). In this study, we created an open microcosm system with homogeneous habitat, consistent total resources, and biodiversity background using Chinese paocai soup, a fermented vegetable, as a substrate. We made efforts to entirely exclude the influence of sampling effects and to exclusively obtain microorganisms from dispersal using microcosm and high‐throughput sequencing techniques. However, in this study, passive sampling based on dispersal failed to shape SAR, and community differences were predominantly caused by species replacement, with only minor contributions from richness differences. Ecological processes including extinction and competitive exclusion, as well as underlying factors like temporal scales and the small island effects, are very likely to have been involved in the studied system. To elucidate the mechanism of SAR development, future studies should design experiments to validate the involvement of dispersal independently.

Extinction drives a discontinuous temporal pattern of species–area relationships in a microbial microcosm system

“…Therefore, studies of SAR formation mechanisms should use controlled experiments to explore the independent mechanisms of action of the three critical processes of speciation, dispersal, and extinction one by one. Along this line, we have successfully revealed the role of dispersal in shaping SAR and confirmed the passive sampling hypothesis 19 , 20 . These research examples confirm the feasibility of the above research idea and are expected to elucidate the mechanism of SAR formation further.…”

Testing the passive sampling hypothesis: The role of dispersal in shaping microbial species-area relationship

“…Previously, we conducted experiments in the open microcosm system to test the passive sampling hypothesis. However, the 15-day experimental period allowed the change of the experimental system to undergo an extinction process after the area effect of dispersion occurred ( Deng et al, 2022a ). Dispersal and extinction play opposite roles in determining the biodiversity of an area.…”

“…(2) Pure sampling effects often mask dispersal. When conducted based on successively nested regions, the increase in species richness over the area due to incomplete sampling (i.e., pure sampling effect) is confused with dispersal, making the passive sampling hypothesis appear invalid ( Hill et al, 1995 ; Deng et al, 2022a ). (3) The role of dispersal is difficult to disentangle from the not mutually exclusive mechanisms that shape SAR.…”

Revived Amplicon Sequence Variants Monitoring in Closed Systems Identifies More Dormant Microorganisms

“…First, 35 kg of white radish ( Raphanus sativus ), 35 kg of cabbage ( Brassica oleracea ), 2 kg of chili pepper ( Capsicum frutescens ), 1 kg of ginger ( Zingiber officinale ), 1 kg of peppercorns ( Zanthoxylum bungeanum ), 2.5 kg of rock sugar, and 210 kg of cold boiled water (containing 6% salt) were packed into a ceramic jar. After 7 days of natural fermentation at room temperature, the pao cai was filtered out with sterile gauze to obtain 200 kg of pao cai soup [ 18 ]. To ensure an even distribution of microorganisms in the soup, the soup was mixed well and then left to rest for 12 h; the supernatant was taken, and the soup was left to rest for 12 h again.…”