Parasitic arthropods often depend on symbiotic microbes to supplement their narrow diets. Facultative parasites exhibit variation in their parasitic activity and diet, and thus, might be expected to have greater variation in their microbial communities. Further, individuals that engage in more parasitic activity may have different microbial communities from those less parasitic within the same population, but this remains unexplored. Here, we compared the microbial communities of individuals exhibiting parasitic (n = 30) and nonparasitic (n = 29) tendencies from two populations (one originating from Tampa, FL and the other Gainesville, FL) of facultatively ectoparasitic mites (Macrocheles muscaedomesticae). Microbial alpha diversity was similar across mites, regardless of parasitic activity or population. Using ANOSIM, we found that our dataset clustered into four groups. The composition of microbial communities of non-parasitic M. muscaedomesticae mites originating from Tampa and Gainesville was distinct from each other, whereas the parasitic mites had a much greater degree of overlap. We hypothesize that the association of parasitic individuals with fly hosts drove the observed overlap in their microbial communities.

The hypothesis that ornaments can honestly signal quality only if their expression is condition-dependent has dominated the study of the evolution and function of colour traits. Much less interest has been devoted to the adaptive function of colour traits for which the expression is not, or is to a low extent, sensitive to body condition and the environment in which individuals live. The aim of the present paper is to review the current theoretical and empirical knowledge of the evolution, maintenance and adaptive function of colour plumage traits for which the expression is mainly under genetic control. The finding that in many bird species the inheritance of colour morphs follows the laws of Mendel indicates that genetic colour polymorphism is frequent. Polymorphism may have evolved or be maintained because each colour morph facilitates the exploitation of alternative ecological niches as suggested by the observation that individuals are not randomly distributed among habitats with respect to coloration. Consistent with the hypothesis that different colour morphs are linked to alternative strategies is the finding that in a majority of species polymorphism is associated with reproductive parameters, and behavioural, life-history and physiological traits. Experimental studies showed that such covariations can have a genetic basis. These observations suggest that colour polymorphism has an adaptive function. Aviary and field experiments demonstrated that colour polymorphism is used as a criterion in mate-choice decisions and dominance interactions confirming the claim that conspecifics assess each other's colour morphs. The factors favouring the evolution and maintenance of genetic variation in coloration are reviewed, but empirical data are virtually lacking to assess their importance. Although current theory predicts that only condition-dependent traits can signal quality, the present review shows that genetically inherited morphs can reveal the same qualities. The study of genetic colour polymorphism will provide important and original insights on the adaptive function of conspicuous traits.