Filogenetski odnosi, poliploidnost in morfološka diverzifikacija znotraj vrste sladki mleček (Euphorbia dulcis, Euphorbiaceae)

Kravanja, Marija (author), Frajman, Božo (mentor)

Poliploidizacija je za evolucijo cvetnic pomemben evolucijski mehanizem. Poliploidi lahko izkoristijo nove niše in postanejo kompetitivno uspešnejši kot njihovi diploidni predniki, zato imajo v primerjavi z njimi pogosto večje areale. Zaradi večje sposobnosti prilagajanja na ekstremne podnebne razmere naj bi bili pogostejši na višjih zemljepisnih širinah in nadmorskih višinah. Sladki mleček (Euphorbia dulcis) je srednjeevropsko razširjena vrsta, ki uspeva v podrasti listnatih in mešanih gozdov. Morfološko je zelo variabilna vrsta, znotraj katere so znana tudi različna kromosomska števila (2n = 12, 18, 24), ki ustrezajo di-, tri- in tetraploidom. Raziskali smo razširjenost populacij različnih ploidnih stopenj na večjem delu areala vrste; tri- in tetraploidi imajo večja območja razširjenosti v primerjavi z diploidnimi (izvornimi) populacijami, v smislu širjenja na večje nadmorske višine pa niso uspešnejši. Poliploidizaciji je pri sladkem mlečku sledilo zmanjšanje monoploidne velikosti genoma. Raziskali smo morfološko diferenciacijo med populacijami različnih ploidnih stopenj ter evolucijski izvor sladkega mlečka z uporabo jedrne regije ITS in plastidne regije ndhF–trnL. Euphorbia dulcis je monofiletska vrsta, sestrska E. duvalii, ki je endemit Francije. Cepitev njunih predniških linij je datirana v srednji pliocen, divergenca znotraj E. dulcis pa je pleistocenska. Diploidne populacije E. dulcis so omejene na območje med zahodnimi obronki Alp in severnimi Apenini, kjer je vrsta verjetno nastala. Največjo znotrajvrstno genetsko raznolikost smo zaznali na območju Alp, zlasti kjer se pojavljajo vse tri ploidne stopnje. Znotrajvrstna morfološka pestrost le delno sovpada z razlikami v ploidnih nivojih. Podvrsti E. dulcis subsp. purpurata in E. d. subsp. incompta gotovo nista sinonima. Njun taksonomski status je vprašljiv, sladki mleček gre obravnavati kot morfološko in citogenetsko variabilno vrsto.

• Language: Slovenian
• Keywords: sladki mleček, poliploidizacija, filogenetske analize, relativna velikost genoma, morfometrične analize
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [M. Kravanja]
• Year: 2023
• PID: 20.500.12556/RUL-148457
• UDC: 631.528.2(043.2)
• COBISS.SI-ID: 162245635
• Publication date in RUL: 24.08.2023

Secondary language

• Language: English
• Title: Phylogenetic relationships, polyploidy and morphological diversification within Euphorbia dulcis (Euphorbiaceae)

Abstract

Polyploidy is one of the most important evolutionary mechanisms in flowering plants. Polyploids can exploit new niches and become more competitively successful than their diploid progenitors, often resulting in larger distribution ranges. Due to their greater ability to adapt to extreme climatic conditions, they are believed to be more common at higher latitudes and altitudes. Sweet spurge (Euphorbia dulcis) is an understory species of deciduous and mixed forests widely distributed in Central Europe. It exhibits significant morphological variability, and different chromosome numbers (2n = 12, 18, 24), corresponding to di-, tri-, and tetraploids, have been reported within the species. We investigated the distribution of populations of different ploidy levels across a large part of the species' range and found out that triploids and tetraploids have larger distribution ranges compared to (ancestral) diploid populations, but they are not more successful in expanding to higher altitudes. Polyploidization in E. dulcis was followed by genome downsizing. We examined morphological differentiation among populations of different ploidy levels and the evolutionary origin of E. dulcis using the nuclear ITS and plastid ndhF–trnL regions. Euphorbia dulcis is a monophyletic species and its sister species turned out to be E. duvalii, an endemic species of France which has never been included in phylogenetic analyses before. The split of their ancestral lineages occurred in the middle Pliocene, while divergence within E. dulcis dates to the Pleistocene. Diploid populations of E. dulcis are limited to the area between the western Alps and the northern Apennines where the species likely originated. The highest intraspecific genetic diversity was detected in the Alpine region, especially where all three ploidy levels cooccur. Intraspecific morphological diversity only partly coincides with differences in ploidy levels. E. dulcis subsp. purpurata and E. d. subsp. incompta are certainly not synonyms, their taxonomic status is questionable. E. dulcis should be considered a morphologically and cytogenetically variable species.

• Keywords: sweet spurge, polyploidization, phylogenetic analyses, relative genome size, morphometirc analyses