- Evolutionary ecology of parasites
- Biological invasions
- Cryptic diversity
- Ecosystem structure and functioning
- Host manipulation by parasites
Google scholar profile (https://scholar.google.fr/citations?hl=fr&user=q3aNzb8AAAAJ)
ORCID Id (https://orcid.org/0000-0003-3347-6497)
1/ Host manipulation by parasites
Parasitism is one of the three central ecological interactions with competition and predation, and arguably the most common form of biological interaction on Earth; half of species are parasitic, the rest all harbor parasites. Some are notorious for manipulating host phenotype (behavior, morphology, etc.). From the first reports in the early seventies of infected crustaceans displaying aberrant behavior and morphology, host manipulation has been recorded in hundreds of host-parasite associations, but we still do not understand the underlying mechanisms. In essence, host manipulation includes any modification in host phenotype that has fitness benefits for the parasite; parasite fitness is increased when the host’s altered phenotype facilitates completion of the parasite life cycle. However, as mentioned above, for a trait to be adaptive, it has to actually confer fitness benefits. Showing that host manipulation indeed increases parasite transmission in natura is the strongest evidence of its adaptive value and yet very challenging.
Furthermore, parasitic manipulation is often characterized on a single or limited range of host traits. However, the full extent of the manipulation can only be grasped through the analyses of multiple traits. Evaluating the independent and combined effects (i.e. multidimensionality) of altered host traits on parasite transmission, and quantifying correlations among traits should also reveal details about their underlying mechanisms.
2/ Cryptic diversity within morphological species: evolutionary and ecological implications
Most biologists estimate diversity as the number of species present at any one place/time and recognize species using morphological characters. However, speciation processes do not necessarily imply morphological changes. New genetic techniques have identified numerous cryptic species (i.e. morphologically similar but genetically divergent units) in many taxa. DNA barcoding is revolutionizing our perception of biodiversity as numerous new cryptic species are continuously discovered. Implications of cryptic diversity for evolution, ecology, conservation and even disease control are now well recognized, but the drivers of this diversity are challenging to study.
Data collected both in New Zealand and France show that cryptic diversity in freshwater crustacean amphipods in very high, with high levels of genetic divergence among lineages, and these cryptic lineages can co-occur in sympatry. Some lineages avoid inter-breeding, even when co-occurring in sympatry, suggesting that they may be separated into (sub)species. Such cryptic diversity can have unexpected consequences on well-documented and long recognized ecological patterns like size-assortative pairing and apparent host-parasite specificity. Canadian amphipods also display cryptic diversity and are good models to test hypotheses around the causes and consequences of cryptic diversity.
3/ Division of labour and social evolution in parasites
Division of labour is a cornerstone of all complex modular systems, and the key to their efficiency and resilience. Among living organisms, division of labour is epitomized by social insects like ants and termites, which consist of a reproductive caste and other castes performing different functions. Yet relationships between colony fitness, functional specialization and the evolution of sociality are still unresolved. Division of labour has recently been discovered in parasitic flatworms, which form clonal colonies within their hosts comprising distinct reproductive and soldier castes. These colonies face intense competition from other parasite species for control of host resources. Using these social parasites as a simple model system, I am testing fundamental hypotheses regarding the evolution of complex, multi-caste societies. With in-vivo and in-vitro experiments, I am exploring kin and enemy recognition, communication between castes, behavioural plasticity within castes, and the factors driving shifts in caste ratios within colonies. Research on these new systems, aim at elucidating key evolutionary forces shaping social structure and division of labour.
4/Parasitism in sea otters
My PhD student, Kyle Shanebeck is studying the infection patterns, pathological effects and life cycle of Corynosoma enhydri in sea otters. A major part of his work is to elucidate the actual life cycle of the parasite in California, Canada and Alaska. As all acanthocephalans, C. enhydri has a two-host life cycle where sea otters are the definitive hosts in which the parasite reaches maturity and reproduces. Sea otters acquire the parasite when they ingest prey infected with the larval stage (i.e. the intermediate host). However, the identity of this intermediate host is unknown in C. enhydri infecting sea otters. Once the life cycle is documented, Kyle will be looking at the ecosystem wide effects of the parasite.