Natural variation in plumage bacterial assemblages in two wild breeding passerines
Date
2012-03-23
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Abstract
Mikrorganismid mängivad loomade elukäigu kujundamisel olulist rolli ja hiljuti on välja tuldud ideega, et sulgi lagundavad bakterid võivad mõjutada lindude sigimispingutuse ja sulestiku puhastamise vahel olevat lõivsuhet, mõjutades seeläbi ka pesitsusedukust. Selleks, et planeerida lindude edukuse ja nende sulestikku asustavate bakterite vaheliste põhjuslike seoste kindlakstegemiseks katseid, tuleb esmalt õppida paremini mõistma sulestiku bakterikoosluste looduslikku varieeruvust.
Töös uuriti rasvatihase (Parus major) ja must-kärbsenäpi (Ficedula hypoleuca) populatsioone, kirjeldamaks sulgi asustavaid bakterikooslusi ja uurida nende seoseid keskkonna ja elukäigu parameetritega. Bakterite arvukuse ja mitmekesisuse määramiseks kasutati vastavalt läbivoolu tsütomeetriat ja ribosomaalse geenidevahelise speisserjärjestuse analüüsi (RISA).
Bakterite arvukus ja mitmekesisus leiti sõltuvat linnuliigist ja pesitsusbiotoobist. Bakterite arvukus oli oluliselt erinev paariliste, kehaosade ja aastate vahel, olles samaaegselt ühe isendi (ja pesitsuspaari) piires, võrrelduna teiste isenditega (ja pesitsuspaaridega), siiski tugevas seoses. Mõlemal linnuliigil leiti emastel bakterite arvukus kõrgem olevat kui isastel, mis koos varasemate andmetega viitab selle mustri üldkehtivusele. Pesitsushooaja jooksul bakterite arvukus muutus tugevasti: järsk tõus pesaehituse ajal, sellele järgnev langus esimese kurna ajal ning uus tõus enne teise pesakonna lennuvõimestumist. Bakterite arvukus oli seotud emaste kehamassi ja pesitsusedukusega (lennuvõimestunud poegade hulk), aga mitmekesisus oli negatiivses seoses hoopiski sulestiku eredusega (mida samuti peetakse isendi kvaliteedi näitajaks). Veelgi enam, bakterite arvukuse muutus pesitsushooajal oli negatiivses seoses sulestiku ereduse muutusega samal perioodil.
Seega, käesolev uurimus kinnitab, et pesitsevate lindude sulgedel elavad bakterikooslused on mõjutatud nii lindude elukäigust kui ka ökoloogilistest parameetritest ja on seoses kehakonditsiooniga. Pesaehituseaegne kiire bakterite arvukuse kasv viitab ühele võimalikule pesaehituse hinnale. Siiski, kõigi leitud seoste põhjuslikkus vajab veel eksperimentaalset testimist.
Microorganisms have been shown to play an important role in shaping the life- histories of animals, and it has recently been suggested that feather-degrading bacteria influence the trade-off between parental effort and self-preening behavior in birds, therefore affecting breeding success. However, to design suitable experiments to examine causal relationships between plumage bacteria and the fitness of host birds, natural variation in plumage bacterial communities needs to be better understood. Wild breeding populations of great tits (Parus major) and Pied Flycatchers (Ficedula hypoleuca) were studied in purpose to explore bacterial assemblages inhabiting the feathers and to investigate associations with ecological and life-history parameters. The density and species richness of bacterial assemblages were studied using flow cytometry and ribosomal intergenic spacer analysis (RISA) respectively. Bacterial load and assemblage richness were found to associate with species and habitat. Bacterial load was significantly different between pairmates, body parts of the same bird and different years, same time there were strong intra-individual (and intrapair) correlations of mentioned factors. In both species bacterial load was higher in females than in males, which along with earlier studies, indicates the generality of this sex pattern. There were significant seasonal changes in bacterial abundance on feathers: increase during nest-building, decline between the nest-building period and fledging of the first brood and increase again before fledging of the second brood. Bacterial abundance was associated with female body mass and breeding success (number of fledglings), but feather-degrading bacterial phylotypic richness was negatively related to female feather chroma (which is also considered to show individual quality). Also, seasonal change in the density of attached bacteria associating with individual birds was negatively associated with change in chroma over the same period. Thus, this study revealed that bacterial assemblages on the feathers of breeding birds are affected both by life history and ecological factors and are related to body condition. Rapid change of bacterial abundance during nest-building may provide one potential cost of nest-building for individual birds. However, the causality of these associations remains to be tested experimentally.
Microorganisms have been shown to play an important role in shaping the life- histories of animals, and it has recently been suggested that feather-degrading bacteria influence the trade-off between parental effort and self-preening behavior in birds, therefore affecting breeding success. However, to design suitable experiments to examine causal relationships between plumage bacteria and the fitness of host birds, natural variation in plumage bacterial communities needs to be better understood. Wild breeding populations of great tits (Parus major) and Pied Flycatchers (Ficedula hypoleuca) were studied in purpose to explore bacterial assemblages inhabiting the feathers and to investigate associations with ecological and life-history parameters. The density and species richness of bacterial assemblages were studied using flow cytometry and ribosomal intergenic spacer analysis (RISA) respectively. Bacterial load and assemblage richness were found to associate with species and habitat. Bacterial load was significantly different between pairmates, body parts of the same bird and different years, same time there were strong intra-individual (and intrapair) correlations of mentioned factors. In both species bacterial load was higher in females than in males, which along with earlier studies, indicates the generality of this sex pattern. There were significant seasonal changes in bacterial abundance on feathers: increase during nest-building, decline between the nest-building period and fledging of the first brood and increase again before fledging of the second brood. Bacterial abundance was associated with female body mass and breeding success (number of fledglings), but feather-degrading bacterial phylotypic richness was negatively related to female feather chroma (which is also considered to show individual quality). Also, seasonal change in the density of attached bacteria associating with individual birds was negatively associated with change in chroma over the same period. Thus, this study revealed that bacterial assemblages on the feathers of breeding birds are affected both by life history and ecological factors and are related to body condition. Rapid change of bacterial abundance during nest-building may provide one potential cost of nest-building for individual birds. However, the causality of these associations remains to be tested experimentally.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
värvulised, sulestik, mikroobikooslused, sigimisedukus, ökoloogilised parameetrid, passerines, plumage, microbial communities, reproductive success, ecological parameters