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Open Access Highly Accessed Research article

Geographic distribution of suitable hosts explains the evolution of specialized gentes in the European cuckoo Cuculus canorus

Juan J Soler1*, Manuel Martín Vivaldi2 and Anders Pape Møller3

Author Affiliations

1 Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (CSIC), General Segura 1, E-04001 Almería, Spain

2 Departamento de Biología Animal, Universidad de Granada, E-18071 Granada, Spain

3 Laboratoire d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, Bâtiment 362, F-91405 Orsay Cedex, France

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BMC Evolutionary Biology 2009, 9:88  doi:10.1186/1471-2148-9-88

Published: 30 April 2009



Several types of selective forces can act to promote parasite specialization. Parasites might specialize on some suitable hosts at the cost of decreasing effectiveness when exploiting other species of hosts, and specialization can be more easily selected for in hosts that the parasites will easily find. Thus demographic characteristics of suitable hosts such as population density and its spatial consistency could be key factors predicting probability of parasite specialization and speciation. Here, we explore this hypothesis by studying the relationship between occurence of specialized races of the European cuckoo (Cuculus canorus) (i.e. gentes) and mean and coefficient of variation in population density estimated for 12 different European regions.


The results were in accordance with the hypothesis because specialized cuckoo egg morphs were more common in suitable hosts with high population density and low variation in population density at the level of host species or genera.


We have presented evidence suggesting that population density and homogeneity of geographic distribution of hosts explain, at least partly, the evolution of specialized egg-morphs of the European cuckoo. These results are consistent with the hypothesis that resource (i.e., host) predictability explains the evolution of host races and species of parasites.