Invasibility of nectarless flowers in plant-pollinator systems

This paper considers plant-pollinator systems in which plants are divided into two categories: The plants that secret a substantial volume of nectar in their flowers are called secretors, while those without secreting nectar are called nonsecretors (cheaters). The interaction between pollinators and secretors is mutualistic, while the interaction between pollinators and nonsecretors is parasitic. Both interactions can be described by Beddington-DeAngelis functional responses. Using dynamical systems theory, we show global dynamics of a pollinator-secretor-cheater model and demonstrate mechanisms by which nectarless flowers/nonsecretors can invade the pollinator-secretor system and by which the three species could coexist. We define a threshold in the nonsecretors' efficiency in translating pollinator-cheater interaction into fitness, which is determined by parameters (factors) in the systems. When their efficiency is above the threshold, non-secretors can invade the pollinator-secretor system. While the nonsecretors' invasion often leads to their persistence in pollinator-secretor systems, the model demonstrates situations in which the non-secretors' invasion can drive secretors into extinction, which consequently leads to extinction of the nonsecretors themselves.