Landscapes within landscapes: A parasite utilizes different ecological niches on the host landscapes of two host species.

Parasites are distributed across populations of hosts, but also across microhabitats on or inside hosts: together the host population distribution and "host landscape" distribution comprise a part of the ecological niche of a parasite. In this paper we examine how a generalist parasite, the tick Ixodes holocyclus, is distributed at both the host population and host landscape scales in two species of host (Perameles nasuta and Rattus rattus) that co-occur. We anaesthetized wildlife to locate ticks from five generalized host body regions; we then analysed the distribution of ticks among the populations of hosts (aggregation) and the distribution of ticks among the available host body regions as niches. Ixodes holocyclus is more aggregated in the R. rattus population. At the host landscape scale, I. holocyclus's utilized niche includes the entire surface of P. nasuta equally, while the niche on R. rattus is focused on the head. Differences in tick aggregation between host species may reflect tick habitat suitability at the host landscape scale, as well as differences in ecological and evolutionary histories. By exploring the distribution of parasites at multiple scales, including host landscapes, we can better understand the complex ecology of parasites.