Diversity and ecological role of pathogenic fungi in insect populations
Date
2023-10-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Putukate arvukust hoiab kontrolli all nende suur suremus, mida looduses põhjustavad putukate vaenlased: kiskjad (nii selgroogsed kui selgrootutud), parasitoidid ja patogeenid. Neist kõige eriilmelisemad ja samas ka vähem uuritud on patogeenid, kelle hulka kuuluvad nii viirused, bakterid, nematoodid kui ka seened. Just seentel on suurim potentsiaal olla pestitsiidide alternatiiviks tänu nende võimele nakatada putukaid läbi füüsilise kontakti. Minu doktoritöö eesmärgiks oli uurida patogeensete seente mitmekesisust putukate looduslikes populatsioonides ning kirjeldada nende poolt põhjustatud suremuse mustreid populatsioonidünaamika ja evolutsioonilise ökoloogia kontekstis. Selleks tegin katseid poollooduslikes tingimustes Eestis ja Argentiinas, seirates looduslikke populatsioone ning analüüsisin olemasolevat kirjandust, mis päädis 4 avaldatud teaduspublikatsiooni ja ühe käsikirjaga. Leidsime, et patogeensete seente liigirikkus on suur: lisaks katsetest leitud 38 seeneliigile näitas kirjanduse analüüs, et looduses on dokumenteeritud putukate nakatumist kokku 122 liiki seenega. Teisalt leidsime aga, et ainult 10% igast putuka populatsioonist sureb seennakkuse tagajärjel. Selline madal suremus ei luba väita, et seentel on oluline roll putukate arvukuse määrajana. Kuna aga seened on keskkonnas alati olemas, siis midagi peab määrama, kas putukas nakatub või mitte. Oma töös leidsin, et seenega nakatumist mõjutab putuka toidutaim. See toetab nn. turvamehe hüpoteesi, kus taimed pakuvad oma kudedes elupaika seentele, kes pakuvad neile kaitset taimtoiduliste putukate vastu. Lisaks tuvastasime entomopatogeenseid võimeid hõimkonnas kõduhallikseened ja mitmetel seeneliikidel, mille puhul see varem teada ei olnud.
The number of insects is primarily regulated by their mortality, which is mostly attributable to the natural enemies of insects: predators, parasitoids and pathogens. Among those, pathogens are the most diverse and understudied group of insect mortality agents, belonging to groups like viruses, bacteria, fungi and nematodes. Due to the ability to infect insects through physical contact, fungi have the biggest potential for application in biocontrol. The aims of my thesis project were to evaluate the diversity of entomopathogenic fungi in natural populations of insects, and to describe the resulting patterns of insect mortality, discussed in the context of population dynamics and evolutionary ecology. For this purpose we conducted experiments in semi-natural conditions in Estonia and Argentina, surveyed natural populations and analysed literature, which resulted in four research papers and a manuscript. We found high diversity of fungal species (38) infecting Lepidoptera. Furthermore, an analysis of papers reporting observations from natural populations yielded data on 122 fungal species infecting insects. However, fungal infections cause only about 10% of insect population mortality that is likely not sufficient to facilitate a major role in regulating insect populations. Nevertheless, as fungi are always present in the environment, there should be some factors influencing which insect gets infected and which does not. In my thesis project, I found that the fungal infection with fungus may depend on the plant the insect is feeding on. This is in concordance with the bodyguard hypothesis, which states that plants support the growth of fungi in their tissues while gaining defense against herbivores. Additionally, my work revealed species from phylum Mortierellomycota and other taxa previously not known to act as entomopathogens.
The number of insects is primarily regulated by their mortality, which is mostly attributable to the natural enemies of insects: predators, parasitoids and pathogens. Among those, pathogens are the most diverse and understudied group of insect mortality agents, belonging to groups like viruses, bacteria, fungi and nematodes. Due to the ability to infect insects through physical contact, fungi have the biggest potential for application in biocontrol. The aims of my thesis project were to evaluate the diversity of entomopathogenic fungi in natural populations of insects, and to describe the resulting patterns of insect mortality, discussed in the context of population dynamics and evolutionary ecology. For this purpose we conducted experiments in semi-natural conditions in Estonia and Argentina, surveyed natural populations and analysed literature, which resulted in four research papers and a manuscript. We found high diversity of fungal species (38) infecting Lepidoptera. Furthermore, an analysis of papers reporting observations from natural populations yielded data on 122 fungal species infecting insects. However, fungal infections cause only about 10% of insect population mortality that is likely not sufficient to facilitate a major role in regulating insect populations. Nevertheless, as fungi are always present in the environment, there should be some factors influencing which insect gets infected and which does not. In my thesis project, I found that the fungal infection with fungus may depend on the plant the insect is feeding on. This is in concordance with the bodyguard hypothesis, which states that plants support the growth of fungi in their tissues while gaining defense against herbivores. Additionally, my work revealed species from phylum Mortierellomycota and other taxa previously not known to act as entomopathogens.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
pathogenic microbes, fungal diseases, insects, population dynamics