Towards revealing the biogeography of belowground diversity
Date
2022-07-07
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Abstract
Mullamikroobide ja -loomade rühmad reguleerivad maapealset elurikkust ja ökosüsteemide toimimist. Ülevaatelisi ja vaatlustel põhinevaid uuringuid tehes tuvastasin, kuidas ruumi, keskkonna ja taimeliikide muutused mõjutavad mullaorganismide kooslusi ja elurikkust ning millised ökoloogilised protsessid on peamiste organismirühmade koosluse varieeruvuse aluseks. Võtsin kasutusele taimede mükoriisa niširuumi (PMNS – plant mycorrhizal niche space) mõiste, mis tähistab taimede võimet kasutada ja kujundada mükoriissete seente kogumit. Selle väärtus sõltub taime mükoriissetest seostest ja funktsionaalsetest tunnustest. Lõin mudeli, et jaotada taimeliike erinevatesse PMNS-idesse, mis võimaldab ennustada mullas leiduvate mükoriissete seente kooslust konkreetses elupaigas. Lisaks määrasin taimeperekonna lepp (Alnus) liikide ja nendega seotud mükoriissete seente, ruumiliste, edaafiliste ja klimaatiliste tegurite suhtelise panuse mükoriissete juurtega seotud bakterikoosluste struktuuri. Leidsin, et mõned arvukad bakterite taksonid on liigispetsiifilised teatud lepaliikidele. Valikuprotsesside olulisus oli suurem väikesemate ja laiema nišiulatusega organismide kooslustes. Globaalse mullauuringu põhjal tuvastasin, et mulla pH ja aasta keskmine sademete hulk olid vastavalt eukarüootsete mikroobide ja loomade koosluste struktuuri peamised määrajad. Eukarüootide rühmadel esinesid vastandlikud elurikkuse mustrid laiuskraadi gradiendil. Minu doktoritöö viitab taimede funktsionaalsete tunnuste suurele tähtsusele mulla mükoriissete seenekoosluste struktureerimisel. Seened vahendavad taimedevahelist konkurentsi nii, sarnase PMNS-iga taimedel on negatiivne seos. Doktoritöö rõhutab ka biootiliste muutujate olulisust juurtega seotud bakterikoosluste kujundamisel ja näitab, et globaalses mastaabis on juurtega seotud ja mullabakterite koosluste aluseks erinevad bioloogilised protsessid. Mulla eukarüootidel esineb positiivne seos keha (raku) suuruse ja niši laiuse vahel ning nende biogeograafilisi mustreid juhtivate ökoloogiliste protsesside ja keskkonnategurite suhtelise mõju vahel.
Belowground microbial and animal organism groups significantly regulate aboveground biodiversity and the functioning of terrestrial ecosystems. By conducting review and research studies, we examined how spatial, environmental, and plant species changes affect the belowground composition and diversity and what ecological processes underlie the community variations in association with organism functional groups. We introduced plant mycorrhizal niche space (PMNS) as a plant’s ability to exploit and shape the mycorrhizal fungal pool depending on its dependency on mycorrhizal status and plant functional traits. We provide a model to classify plant species into different PMNS, helping to predict soil mycorrhizal fungi community in a particular habitat by comparing PMNS distance between plant species. Further, we found that the Alnus species phylogeny was the primary determinant for the composition of root-associated bacterial communities, followed by edaphic, spatial and climate variables. In addition, we found Alnus species-specificity for some highly abundant bacterial phylotypes. Our analysis also showed that the importance of selection processes was higher in the community assemblage of smaller-bodied and wider niche breadth organisms. Soil pH and mean annual precipitation were the primary determinants of the community structure of eukaryotic microbes and animals, respectively. We further found contrasting latitudinal diversity patterns and strengths for soil eukaryotic microbes and animals. Taken together, this thesis shows the role of plant functional traits in structuring soil mycorrhizal communities mediating plant-to-plant competition such that there is a negative relation between the similarity of PMNS and the role of mycorrhizal fungi in plant invasion and alteration of mycorrhizal fungi following invasion. It also highlights the importance of biotic variables in shaping root-associated bacterial communities and shows that different processes underlie root-associated and soil bacterial communities on a global scale. Finally, our results point to a potential link between body size and niche breadth in soil eukaryotes and the relative effect of ecological processes and environmental factors in driving their biogeographic patterns.
Belowground microbial and animal organism groups significantly regulate aboveground biodiversity and the functioning of terrestrial ecosystems. By conducting review and research studies, we examined how spatial, environmental, and plant species changes affect the belowground composition and diversity and what ecological processes underlie the community variations in association with organism functional groups. We introduced plant mycorrhizal niche space (PMNS) as a plant’s ability to exploit and shape the mycorrhizal fungal pool depending on its dependency on mycorrhizal status and plant functional traits. We provide a model to classify plant species into different PMNS, helping to predict soil mycorrhizal fungi community in a particular habitat by comparing PMNS distance between plant species. Further, we found that the Alnus species phylogeny was the primary determinant for the composition of root-associated bacterial communities, followed by edaphic, spatial and climate variables. In addition, we found Alnus species-specificity for some highly abundant bacterial phylotypes. Our analysis also showed that the importance of selection processes was higher in the community assemblage of smaller-bodied and wider niche breadth organisms. Soil pH and mean annual precipitation were the primary determinants of the community structure of eukaryotic microbes and animals, respectively. We further found contrasting latitudinal diversity patterns and strengths for soil eukaryotic microbes and animals. Taken together, this thesis shows the role of plant functional traits in structuring soil mycorrhizal communities mediating plant-to-plant competition such that there is a negative relation between the similarity of PMNS and the role of mycorrhizal fungi in plant invasion and alteration of mycorrhizal fungi following invasion. It also highlights the importance of biotic variables in shaping root-associated bacterial communities and shows that different processes underlie root-associated and soil bacterial communities on a global scale. Finally, our results point to a potential link between body size and niche breadth in soil eukaryotes and the relative effect of ecological processes and environmental factors in driving their biogeographic patterns.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
soils, biodiversity, mycorrhiza, biotic components, abiotic factors, community (biology), biogeography