Niche Restriction and Mate Finding in Vertebrate Hosts

Niche Restriction and Mate 9

Finding in Vertebrate Hosts

Klaus Rohde

School of Biological Sciences, University of New England,

Armidale, NSW 2351, Australia

Introduction

Niche restriction is universal among parasites, and it has been suggested

that it is at least partly the result of selection which favours mate finding

and thus cross-fertilization, leading to greater genetic diversity (‘mating

hypothesis’). In this chapter, I review evidence for niche restriction at the

level of hosts (host range and host specificity), populations (aggregation)

and host individuals (microhabitat specificity). I also discuss mating

behaviour and particularly mate finding, the morphological basis of

mating, using some recent light- and electron-microscopic studies,

evidence for the role of niche restriction in facilitating mating, and the

relative importance of niche segregation and differences in copulatory

organs for reinforcing reproductive barriers. No attempt is made to

discuss all these aspects for each of the parasite groups in detail. Instead, I

select examples from those groups that have been examined best, in order

to clarify patterns and to test the mating hypothesis of niche restriction

and segregation. It is emphasized that only a holistic approach can clarify

the significance of mating in niche restriction, i.e. an approach that

considers all evidence jointly.

Niche Restriction

Restriction to host species (host specificity and host range)

There is no ‘universal’ parasite, i.e. a parasite that infects all species,

although the number of hosts used varies among parasite species. It is

useful to distinguish host range and host specificity. Host range is defined

as the number of host species used by a parasite, irrespective of how

CABInternational2002.The Behavioural Ecology of Parasites
(eds E.E. Lewis, J.F. Campbell and M.V.K. Sukhdeo) 171