Genetic variation of grassland plants in changing landscapes
Date
2024-05-16
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Abstract
Hiljutised maakasutuse muutused on toonud kaasa ulatusliku looduslike ja poollooduslike koosluste killustumise. Paljud poollooduslikud rohumaad ehk pärandniidud on kinni kasvanud või muudetud intensiivselt majandatavaks põllumaaks, mis on halvendanud niidutaimede kasvukohatingimusi. Selle tulemusena on elurikkus, sealhulgas geneetiline mitmekesisus (liigi- või populatsioonisisene mitmekesisus) märkimisväärselt kahanenud. Kuna geneetiline mitmekesisus tagab organismide võime keskkonnamuutustega kohastuda, on selle kaitsmine ja säilitamine ülioluline. Doktoritöö eesmärk oli hinnata maastiku struktuuri ja maakasutuse muutuse mõju rohumaade taimede geneetilisele mitmekesisusele ja geenivoolule. Töös kasutasin uurimisliikidena mägiristikut (Trifolium montanum) ja harilikku nurmenukku (Primula veris). Leidsin, et poollooduslikud niidukooslused, eriti kõrgema servatihedusega pärandniidud populatsioonide ümbruses, toetavad niidutaimede geneetilist mitmekesisust, kuid metsa mõju geneetilisele mitmekesisusele oli muutlik. Uurisin ka taimepopulatsioonide vahelise maastiku mõju geenivoolule (geneetilise info vahetus populatsioonide ja isendite vahel õietolmu või seemnete leviku teel) nende vahel. Leidsin, et tavaliselt eeldatav muster, kus geograafiliselt kaugemal asuvad populatsioonid on ka geneetiliselt erinevamad, kehtib vaid teatud olukordades. Suurem niidukoosluste osakaal populatsioonide vahel hõlbustas geenivoolu. Avatud ning kinnikasvanud pärandniitudel läbiviidud uuringus leidsin, et adaptiivne geneetiline mitmekesisus oli kinnikasvanud loopealsetel kõrgem kui avatud loopealsetel, neutraalne geneetiline mitmekesisus püsis aga muutumatuna, viidates sellele, et taimepopulatsioonid on uute keskkonnatingimustega kohastumas. Üldiselt leidsime, et kuigi rohumaataimede geneetilist mitmekesisust mõjutab kinnikasvamine ning tuleks püüelda heterogeensete rohumaade poole, tuleb looduskaitseliste tegevuste plaanimisel arvestada skaalade, viibinud vastuste ja maakasutuse ajalooga.
Recent land use changes have transformed natural ecosystems, leading to the fragmentation of natural and semi-natural habitats. Many semi-natural grasslands are overgrown or turned into intensively managed agricultural land, significantly altering habitat conditions for grassland plants. Not all organisms can adapt to these changes, resulting in biodiversity loss, including genetic diversity – the diversity within species or populations. As genetic diversity ensures the organisms’ ability to adapt to changes, it is vital to protect and preserve it. This thesis aimed to study the effect of landscape structure and land use change on the genetic diversity of insect-pollinated grassland plants using Trifolium montanum and Primula veris as study species. We found that a higher proportion of grasslands in the surroundings of the study populations, particularly those with higher edge density, support the genetic diversity of grassland plants. Forest, however, had a variable effect on genetic diversity. We also studied how the landscape between plant populations affects the gene flow (exchange of genetic information through pollen or seed flow) between plant populations. The commonly expected pattern of populations geographically further apart being also more different genetically held true only in some situations. A higher historical proportion of grasslands between study populations facilitated gene flow. A comparison of genetic diversity in open and overgrown grasslands revealed higher genetic diversity assessed at putatively adaptive loci in overgrown habitats, whereas neutral genetic diversity remained unaffected by the overgrowth. This indicates to the process of plant populations adapting to the new environmental conditions. Overall, I found that while overgrowth affects the genetic diversity of grassland plants and heterogeneous grassland is desirable, scales, delayed responses, and land use history must be considered when planning conservation activities.
Recent land use changes have transformed natural ecosystems, leading to the fragmentation of natural and semi-natural habitats. Many semi-natural grasslands are overgrown or turned into intensively managed agricultural land, significantly altering habitat conditions for grassland plants. Not all organisms can adapt to these changes, resulting in biodiversity loss, including genetic diversity – the diversity within species or populations. As genetic diversity ensures the organisms’ ability to adapt to changes, it is vital to protect and preserve it. This thesis aimed to study the effect of landscape structure and land use change on the genetic diversity of insect-pollinated grassland plants using Trifolium montanum and Primula veris as study species. We found that a higher proportion of grasslands in the surroundings of the study populations, particularly those with higher edge density, support the genetic diversity of grassland plants. Forest, however, had a variable effect on genetic diversity. We also studied how the landscape between plant populations affects the gene flow (exchange of genetic information through pollen or seed flow) between plant populations. The commonly expected pattern of populations geographically further apart being also more different genetically held true only in some situations. A higher historical proportion of grasslands between study populations facilitated gene flow. A comparison of genetic diversity in open and overgrown grasslands revealed higher genetic diversity assessed at putatively adaptive loci in overgrown habitats, whereas neutral genetic diversity remained unaffected by the overgrowth. This indicates to the process of plant populations adapting to the new environmental conditions. Overall, I found that while overgrowth affects the genetic diversity of grassland plants and heterogeneous grassland is desirable, scales, delayed responses, and land use history must be considered when planning conservation activities.
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