Phenotypic and genetic differentiation in the hybridizing species pair Carex flava and C. viridula in geographically different regions
Date
2018-10-26
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Abstract
Taimed varieeruvad üle terve oma levila silmapaistvalt morfoloogiliselt, geneetiliselt ning kohastumuste poolest. Esiteks seab populatsioonidevaheline geograafiline kaugus füüsilised piirangud geenide vahetamiseks ja teisalt mõjutavad populatsioone eri piirkondades erinevad ökoloogilised tegurid ning keskkonnatingimused, mis võivad viia liigisisese geograafilise eristumiseni. Teisalt on nad võimelised omavahel ristuma (hübridiseeruma), mis ulatusliku geenivahetuse tagajärjel võib viia regionaalse sarnasuseni. Doktoritöös uurisime lähedaselt suguluses olevate kollase tarna (Carex flava) ja ojatarna (C. viridula) morfoloogilist ja geneetilist eristumist kolmes klimaatiliselt erinevas regioonis: Eestis, Šveitsi lauskmaal ja Šveitsi Alpides. Uuritud tarnad erinevad populatsioonide suuruse ja levila ulatuse poolest, mis teoorias põhjustab erinevat regionaalse eristumise mustrit. Sellest tulenevalt, oli minu doktoritöö peamiseks eesmärgiks tuvastada, kas ojatarn oma katkendliku leviku ja väikeste populatsioonidega on regioonide vahel rohkem eristunud kui kollane tarn, kes on laialdasema levikuga ja suuremate populatsioonidega. Teisalt on võimalik, et ristumine mõjutab nende liikide evolutsiooni. Uuringu eesmärkide täitmiseks, teostasime morfoloogilise ja geneetilise analüüsi ning ümberistutuskatse kolme eelpool mainitud regiooni vahel. Tulemused näitavad, et plastilisus, geneetiline varieeruvus ja genotüübi-keskkonna koosmõju on oluliselt mõjutanud mõlema tarna ja nende hübriidi regionaalset eristumist, kuid eristumine on mõnevõrra tugevam ojatarnal. Leidsime, et nii looduslikes populatsioonides kui ka ühisaedades erinesid kollane ja ojatarn üksteisest suurema osa morfoloogiliste tunnuste poolest oluliselt. Geneetiline analüüs toetas tarnadevahelist erinevust, kuid näitas ka geenivahetust. Seega ei ole liikidevaheline hübridiseerumine ei ole nii ulatuslik, et takistada ojatarna regionaalset eristumist. Kollase tarna ja ojatarna morfoloogilise ja geneetilise varieeruvuse kombineeritud uuring ning vastastikune ümberistutuskatse võimaldas teha mitmeid olulisi järeldusi uuritud taksonite morfoloogilise varieeruvuse, geneetilise mitmekesisuse, geneetilise eristumise ja kohastumuse kohta ning hinnata hübridiseerumise mõju laialdasema ja katkendlikuma levikuga taksonitel. See doktoritöö on oluline panus hübridiseeruvate liikide geograafilise eristumise mõistmiseks, mis on eriti tähtis globaalsete muutuste uuringutes ja looduskaitses.
Plants experience different climatic and environmental conditions in different locations of their distribution areas. This can lead to different growth between populations. Moreover, populations may adapt to their local conditions. Plants of closely related plant species may also hybridize, i.e. cross between species, which may result in increased similarity. Less common species are expected to show stronger differences between regions and populations than more common species because random processes are more likely to affect the smaller populations of less common species. On the other hand, if two species hybridize with each other, they may also show similar differences between regions. We asked whether regional differences were larger in the less common sedge species Carex viridula than in the more common C. flava. We also tested whether regional differences between Estonia and lowland and highland Switzerland are mainly environmentally determined or also have a genetic basis. We assessed regional differences in morphological, size-related and floral traits in 43 populations in the field, and we studied molecular genetic differentiation. Moreover, we grew plants of all populations in three common gardens, one in each study region, which enabled us to test whether differences between species and regions are genetic, and whether plants are adapted to the environmental conditions of the home region. We found clear morphological and genetic differences between the two hybridizing species indicating that C. flava and C. viridula are indeed separate species. Nevertheless, we also found hybridization between the two and backcrossing of hybrids with the two species, which may contribute to their considerable morphological similarity. We further found that environmental effects, genetic differences and genetic differences in the expression of environmental effects all contributed to regional differences and that these differences were more pronounced in the less common C. viridula than in C. flava. This thesis contributes to understanding geographic differences in hybridizing species. This is an understudied field, which is important, however, for understanding species responses to global change and for plant conservation.
Plants experience different climatic and environmental conditions in different locations of their distribution areas. This can lead to different growth between populations. Moreover, populations may adapt to their local conditions. Plants of closely related plant species may also hybridize, i.e. cross between species, which may result in increased similarity. Less common species are expected to show stronger differences between regions and populations than more common species because random processes are more likely to affect the smaller populations of less common species. On the other hand, if two species hybridize with each other, they may also show similar differences between regions. We asked whether regional differences were larger in the less common sedge species Carex viridula than in the more common C. flava. We also tested whether regional differences between Estonia and lowland and highland Switzerland are mainly environmentally determined or also have a genetic basis. We assessed regional differences in morphological, size-related and floral traits in 43 populations in the field, and we studied molecular genetic differentiation. Moreover, we grew plants of all populations in three common gardens, one in each study region, which enabled us to test whether differences between species and regions are genetic, and whether plants are adapted to the environmental conditions of the home region. We found clear morphological and genetic differences between the two hybridizing species indicating that C. flava and C. viridula are indeed separate species. Nevertheless, we also found hybridization between the two and backcrossing of hybrids with the two species, which may contribute to their considerable morphological similarity. We further found that environmental effects, genetic differences and genetic differences in the expression of environmental effects all contributed to regional differences and that these differences were more pronounced in the less common C. viridula than in C. flava. This thesis contributes to understanding geographic differences in hybridizing species. This is an understudied field, which is important, however, for understanding species responses to global change and for plant conservation.
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Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
sedge, hybrids, genetic variability, phenotypic variation, Estonia, Suisse