The question of how biodiversity affects the stability of ecosystems has been intensively debated among ecologists, due to the rapidly growing concerns for the worldwide loss of biodiversity and its potential disastrous effects on various aspects of ecosystems. While much research has focused on the effects of species diversity on community stability and evidence for the positive relationship between diversity and stability is substantial, little attention has been paid to phylogenetic diversity. Here we examined the effects of phylogenetic diversity on community resistance and resilience, using protist microcosms subjected to environmental warming. We monitored the dynamics of protist communities each containing three species but differing in the level of phylogenetic diversity (PD). Protist communities were subject to warming for three different durations (12, 24, and 36 hours), which resembled stochastic disturbance events that shift communities away from their stable state. We also set up monocultures of each species to evaluate individual species’ response to the same perturbation.
Our results showed that different protist species differed in their resistance to disturbance and their resilience from disturbance. The biovolume of populations significantly decreased in monocultures after disturbance. Species extinction occurred in monocultures of Glaucoma scintillans and Colpidium striatum in the 12-hour warming treatment, and Colpidium kleini went extinct after 24 hours of warming. Populations in monocultures exhibit significant phylogenetic signals in resilience according to Blomberg’s K test. The Paramecium spp. tended to exhibit higher resilience that the biovolume of each population recovered to pre-disturbance biovolume. Species with large body sizes were not affected by disturbance. Communities that differed in the level of phylogenetic diversity did not differ significantly in resistance; however, communities with higher phylogenetic diversity tended to exhibit a significant positive diversity-resilience relationship. This result arose because more diverse communities have higher likelihood of containing species with high resilience (phylogenetic sampling effect). Our results demonstrate that phylogenetic diversity, as an important component of biodiversity, influences the stability properties of ecosystems.