Abstract:Mutualistic symbiosis in general implies that both species can receive survival and reproductive benefits through the interaction each other, which usually increases the species fitness of both species. Mutualistic symbiosis plays an indispensable role in maintaining biodiversity and ecosystem functioning, and the loss of such interactions has the potential to lead to the collapse of entire local ecosystems, thus exacerbating the impact of global changes on biodiversity loss and ecosystem destruction. Therefore, it is essential to investigate the mechanisms that maintain the stability of the reciprocal relationship. The interaction between fig trees and their pollinating wasps is a typical example of mutualism in nature. Due to their close obligate mutualism, the system of fig trees and fig wasps is an ideal model system for studying mutualistic symbiosis. This reciprocal relationship occurs in the syconia, meaning that syconia are the site of interspecific interactions in which fig wasps pollinate flowers and lay eggs. Thus, we could consider syconia as habitat patches for fig wasps, and utilized the framework of metapopulation theory to construct dynamical model of the reciprocal relationship between fig tree and fig wasp species, and studied the stability and conditions for the persistence of this mutualistic system. Since the habitat patches (i.e., syconia) here are dynamic and changing (due to the production and loss of syconia in a fig tree), our models differ from the traditional metapopulation model (the total number of habitat patches is fixed) by adding dimensions that describe the dynamics of the habitats. The models showed that: (1) a sufficiently large production rate of syconia (greater than a threshold) was a necessary condition for the reciprocal mutualism between fig trees and fig wasps to persist. (2) Theoretical analysis revealed the existence of bi-stability property (i.e., the Allee effect) in the mutualistic system of fig trees and fig wasps, whereby the persistence of the mutualistic system depended on the initial size of the population exceeding a threshold. In other words, the system was destined to become extinct when the size of the population fell below the threshold. (3) The increase in the production rate of syconia led to a corresponding rise in the population of fig wasps, but had no effect on the abundance of syconia unoccupied by fig wasps. In conclusion, our models could not only facilitate the investigation of the dynamical properties of the mutualistic system between fig trees and fig wasps, but also contributed to the development for the dynamics of patches in the metapopulation theory.