THE IMPORTANCE OF FOSSILS IN INTEGRATIVE PARASITOLOGY

Understanding the origins, evolution and radiation of parasites through time relies heavily on assembling robust phylogenies of parasites, their vectors and hosts. Given the nature of parasites, often cryptic, small, seemingly simple or morphologically modified/reduced to extremes and prone to converge on similar forms, molecular-based phylogenies using extant taxa are fundamental in providing an evolutionary framework. Character traits from extant taxa are subsequently used to infer evolutionary transitions from free-living to parasitic life styles, to estimate ancestral morphologies, the development of life cycles and the pattern of host use or host switching through time. As a result, numerous hypotheses concerning historical associations and life history habits arise from such studies but rely almost entirely on our knowledge of extant forms. Fossils provide vital evidence for validating phylogeny-derived hypotheses, for calibrating phylogenies (essential in understanding when and where events took place), and for revealing direct evidence of parasite morphology and the nature of ancient host-parasite interactions. Looking for and making use of fossil parasites requires a mix of serendipity and awareness of what to look for. Rarity usually means such finds are rich in information. Modern techniques (CT-scanning, aDNA, biomolecular prospecting) provide an increasing array of tools that affirm the role of palaeontology in the field of parasitology beyond ‘palaeoparasitology’ as originally envisaged by (palaeo)anthropologists.