Exclusion and spatial segregation in the apparent competition between two hosts sharing macroparasites

Area of Science:

• Ecology
• Mathematical Biology
• Parasitology

Background:

• Apparent competition, where species indirectly interact via a shared resource or enemy, is a key ecological process.
• The spatial dynamics and mechanisms of apparent competition, particularly in structured environments, remain underexplored.
• Macroparasites can mediate apparent competition, influencing host population dynamics and coexistence.

Purpose of the Study:

• To investigate the spatial dynamics of apparent competition between two host species mediated by macroparasites.
• To understand the role of spatial structure, host diffusion, and parasite-induced mortality in host coexistence.
• To analyze the mechanisms underlying apparent competition in spatially structured environments.

Main Methods:

• Analysis of a single-host macroparasite partial differential equation (PDE) model with uniform and spatially-dependent vital rates.
• Development and analysis of a two-host PDE model incorporating spatial diffusion and apparent competition.
• Investigation of parasite persistence, host abundance, and species coexistence under varying diffusion coefficients and mortality rates.

Main Results:

• A threshold condition for parasite persistence was established.
• For spatially-dependent vital rates, increased host diffusion enhanced overall host population, contrary to isolated population models.
• Shared parasites, influenced by diffusion and mortality differences, reduced realized habitat and could cause extinction of less tolerant species.

Conclusions:

• Dispersal effects on population dynamics are complicated by the presence of regulating parasites.
• Spatially-independent models are insufficient for understanding the dynamics of apparent competition.
• Spatial heterogeneity plays a critical role in host coexistence when mediated by shared parasites.