Plumage iridescence is associated with distinct feather microbiota in a tropical passerine

Veronika Gvoždíková Javůrková,Jakub Kreisinger,Erik D Enbody,Jordan Karubian,Jakub Mrázek,Kryštof Chmel

doi:10.1038/s41598-019-49220-y

Abstract

Birds present a stunning diversity of plumage colors that have long fascinated evolutionary ecologists. Although plumage coloration is often linked to sexual selection, it may impact a number of physiological processes, including microbial resistance. At present, the degree to which differences between pigment-based vs. structural plumage coloration may affect the feather microbiota remains unanswered. Using quantitative PCR and DGGE profiling, we investigated feather microbial load, diversity and community structure among two allopatric subspecies of White-shouldered Fairywren, Malurus alboscapulatus that vary in expression of melanin-based vs. structural plumage coloration. We found that microbial load tended to be lower and feather microbial diversity was significantly higher in the plumage of black iridescent males, compared to black matte females and brown individuals. Moreover, black iridescent males had distinct feather microbial communities compared to black matte females and brown individuals. We suggest that distinctive nanostructure properties of iridescent male feathers or different investment in preening influence feather microbiota community composition and load. This study is the first to point to structural plumage coloration as a factor that may significantly regulate feather microbiota. Future work might explore fitness consequences and the role of microorganisms in the evolution of avian sexual dichromatism, with particular reference to iridescence.

Highlights

Avian plumage is a unique integumentary structure that is critical for multiple functions including flight[1,2,3], thermoregulation[4,5,6], and socio-sexual communication[7,8]
Iridescent feathers have decreased hydrophobicity[53] and are more sensitive to bacterial degradation[54], which provide a potential mechanism for honest signaling of individual quality
We found sex nested within plumage phenotype as significant predictor of Whiteshouldered Fairywren microbial load (ANOVA: F(2,21) = 3.856, p = 0.038), with iridescent black males tended to have lower feather microbial loads than did matte black females (Tukey’s HSD test: p = 0.053; Table S1, Fig. 2)

Summary

Introduction

Avian plumage is a unique integumentary structure that is critical for multiple functions including flight[1,2,3], thermoregulation[4,5,6], and socio-sexual communication[7,8]. Feathers are subject to exposure to the external environment and host diverse microbial communities[28,29,30,31] including antibiotic compounds-producing microorganisms[31], pathogens[32] or feather-degrading bacteria[29,33] The latter can deteriorate feather structure[34,35] and negatively affect signaling function of both pigment based and structural plumage coloration[36,37,38]. Iridescent plumage phenotypes show greater diversity in tropical and sub-tropical species[12,49,55,56,57,58] that are exposed to higher and more diversified microbial loads[59,60] It follows, that apart from a protective role of feather pigments, birds may have developed other defense mechanisms for preventing detrimental effects of external parasites including microorganisms on feather wear[61]. We leverage this unique variation to ask how feather microbial load and diversity varies between plumage phenotypes and discuss mechanistic underpinnings and consequences for plumage signaling and evolution

Methods

Results

Conclusion