title: Contrasting parasite communities among allopatric colour morphs of the Lake Tanganyika cichlid Tropheus.
abstract: BACKGROUND
  Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs.
  
  
  RESULTS
  Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic differentiation were not significant, suggesting that host dispersal does not influence parasite community diversification.
  
  
  CONCLUSIONS
  Subject to alternating episodes of isolation and secondary contact because of lake level fluctuations, Tropheus colour morphs are believed to accumulate and maintain genetic differentiation through a combination of vicariance, philopatric behaviour and mate discrimination. Provided that the observed contrasts in parasitism facilitate adaptive divergence among populations in allopatry (which is the current situation), and promote the evolution of reproductive isolation during episodes of sympatry, parasites might facilitate speciation in this genus.
authors: Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Ch, Deberiotstraat, 32, Leuven, B-3000, Belgium. joost.raeymaekers@unibas.ch
authors: Joost A M
authors: JA
authors: Raeymaekers
authors: Pascal I
authors: PI
authors: Hablützel
authors: Arnout F
authors: AF
authors: Grégoir
authors: Jolien
authors: J
authors: Bamps
authors: Anna K
authors: AK
authors: Roose
authors: Maarten P M
authors: MP
authors: Vanhove
authors: Maarten
authors: M
authors: Van Steenberge
authors: Antoine
authors: A
authors: Pariselle
authors: Tine
authors: T
authors: Huyse
authors: Jos
authors: J
authors: Snoeks
authors: Filip A M
authors: FA
authors: Volckaert
mesh_terms: D000350:Africa, Central; D000818:Animals; D023681:Cichlids / Q000235:genetics* / Q000469:parasitology*; D049810:Genetic Speciation; D005828:Genetics, Population; D060106:Lakes; D018895:Microsatellite Repeats; D017422:Sequence Analysis, DNA