Ecología y perspectivas evolutivas de la coexistencia de los ácaros de las plumas en la curruca capirotada "Sylvia atricapilla"

Laburpena

In nature there exists a wide variety of symbionts with similar ecological requirements that occupy the same host. However, the host is a limited habitat, so the coexistence of symbiont species may get complicated. The main goal of this thesis is to summarize which factors have a strong influence in the coexistence of ecologically similar symbionts in the same host species at different scales. In order to accomplish this goal we chose the blackcap Sylvia atricapilla as host species because it (1) is widely distributed among a broad range of environments, (2) normally harbours two feather dwelling mite species, Proctophyllodes sylviae and Trouessartia bifurcata (which are potential competitors), and (3) possesses different migratory behaviours that may create variation in individual host quality for such symbionts. At the within-host scale, both mite species are differently distributed on the wing: P. sylviae preferentially occupies medial-outer regions of the feather while T. bifurcata appears in medial-inner sections. Despite niche partitioning, when both species coincide in the same wing area, they experience a reduction in numbers. However, T. bifurcata seems to play a dominant role when both mite species coexist on the same host individual, given that the presence of that mite is associated with lower numbers of P. sylviae. Nevertheless, P. sylviae is able to colonise migratory and sedentary hosts alike, and reaches much higher numbers than T. bifurcata (both within hosts and at higher scales). At a regional scale, P. sylviae is more tolerant to environmental conditions than T. bifurcata, which is absent from some localities. This suggests that P. sylviae is a more generalist mite than T. bifurcata, which seems to suffer greater constraints associated with host attributes and environmental conditions. In summary, feather mite coexistence might be explained by the advantages one species has over the other at different scales.