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

Soler JJ, Vivaldi MM, Møller AP - BMC Evol. Biol. (2009)

Bottom Line: 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.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.These results are consistent with the hypothesis that resource (i.e., host) predictability explains the evolution of host races and species of parasites.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Aridas (CSIC), General Segura 1, Almería E-04001, Spain. jsoler@eeza.csic.es

ABSTRACT

Background: 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.

Results: 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.

Conclusion: 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.

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Phylogenetic relationships between suitable hosts of the European cuckoo. See Material and methods for sources. Species with species-specific cuckoo egg morphs are shown with two asterisks after the species names, while those with specialized cuckoo eggs for the entire genus are shown with + symbol before the species names.
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Figure 3: Phylogenetic relationships between suitable hosts of the European cuckoo. See Material and methods for sources. Species with species-specific cuckoo egg morphs are shown with two asterisks after the species names, while those with specialized cuckoo eggs for the entire genus are shown with + symbol before the species names.

Mentions: Phylogenetic relationships among different species were based on recent publications [40-42] (Fig. 3). We assumed all polytomies (N = 14) to be unresolved. Branch lengths were assigned using three different methodologies: (i) all were set equal to one; (ii) by arbitrarily assigning all inter-node branch segments equal to one, but constraining tips to be contemporaneous [43]; and (iii) by tips being contemporaneous, the depth of each node being arbitrarily set to one less the number of tip species that descended from it [44].


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

Soler JJ, Vivaldi MM, Møller AP - BMC Evol. Biol. (2009)

Phylogenetic relationships between suitable hosts of the European cuckoo. See Material and methods for sources. Species with species-specific cuckoo egg morphs are shown with two asterisks after the species names, while those with specialized cuckoo eggs for the entire genus are shown with + symbol before the species names.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2683792&req=5

Figure 3: Phylogenetic relationships between suitable hosts of the European cuckoo. See Material and methods for sources. Species with species-specific cuckoo egg morphs are shown with two asterisks after the species names, while those with specialized cuckoo eggs for the entire genus are shown with + symbol before the species names.
Mentions: Phylogenetic relationships among different species were based on recent publications [40-42] (Fig. 3). We assumed all polytomies (N = 14) to be unresolved. Branch lengths were assigned using three different methodologies: (i) all were set equal to one; (ii) by arbitrarily assigning all inter-node branch segments equal to one, but constraining tips to be contemporaneous [43]; and (iii) by tips being contemporaneous, the depth of each node being arbitrarily set to one less the number of tip species that descended from it [44].

Bottom Line: 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.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.These results are consistent with the hypothesis that resource (i.e., host) predictability explains the evolution of host races and species of parasites.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Aridas (CSIC), General Segura 1, Almería E-04001, Spain. jsoler@eeza.csic.es

ABSTRACT

Background: 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.

Results: 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.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus