Table 1 Definition of terms

Ecosystem engineer

Concept coined by [62] that refers to organisms that directly or indirectly alter the environment in which they occur. Their action may modify or create new habitats through their own physical structures (autogenic engineers) or through their activities (allogenic engineers).

Functional response

Differences in tissue preferences or resources used by a species in response to interspecific competition [26]. It is an indicator that different parasite species are interacting.

Infracommunity

Includes all the infrapopulations that colonise a single host or an organ and interact with each other for space and resources [40].

Microhabitat

Small-scale environment where an organism or an assemblage of organisms naturally occur and interact, both directly and indirectly, with the biotic and abiotic elements.

Numerical response

Positive or negative variation of a particular infrapopulation size when facing the presence of another species [26]. It is an indicator that different parasite species are interacting.

Virulence

Effects of an infection in host fitness, i.e. severity of the disease caused by a particular organism (damage-related concept [63]). It could also express the transmissibility of an organism, i.e. its capacity to grow and proliferate within a host [64].