Three Tertiary Euphorbia species persisted in the forests of the Balkan Peninsula

Danka Caković,Božo Frajman

doi:10.1007/s00606-020-01672-w

Danka Caković, Božo Frajman

Open Access

https://doi.org/10.1007/s00606-020-01672-w

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Abstract

The Balkan Peninsula is renowned as a refugium of forest species, which were more widespread in the Tertiary. We here investigated three species from one of the largest genera of flowering plants, Euphorbia, which survived the Pleistocene glaciations in the Balkan Peninsula, but responded differently to Holocene warming. Using ITS sequences, multivariate morphometrics and relative genome size (RGS) measurements, we explored relationships among E. amygdaloides, E. heldreichii and E. orjeni, for which different taxonomic treatments have been proposed. The ITS-inferred phylogenies indicate that all three species form independent evolutionary lineages, which have similar RGS, but differ morphologically, and should thus be treated as independent species. The most enigmatic of them, E. orjeni, was found for the first time after 100 years at its type locality in Montenegro, and, based on herbarium revision, was discovered also in the surroundings of Belgrade. Euphorbia heldreichii is more widespread, distributed in the southern Balkan Peninsula, whereas E. amygdaloides occurs in forests throughout Europe, North Africa and Western Asia. Our study emphasises the importance of further botanical exploration of the Balkan Peninsula, a hotspot of European biotic diversity.

Highlights

The current distribution of biota throughout the Northern Hemisphere has been greatly affected by the climatic fluctuations and changing geography of the last 65 million years, i.e. during the Tertiary and Quaternary periods (Wolfe 1975; Milne and Abbott 2002)
15 million years drastically changed the vegetation of Europe, where species of previously widespread Tertiary humidtemperate forests found their refugia in the Balkan Peninsula, Carpathians and adjacent Anatolia (Milne and Abbott 2002; Lendvay et al 2016)
Many Tertiary species found a shelter in the Mediterranean Basin that is recognised as one of the most important refugia for species of this ancient flora (Thompson et al 2005) and as a biodiversity hotspot with an exceptional role in the preservation of unique species and genetic diversity (Myers et al 2000; Nieto Feliner 2014)

Summary

Introduction

The current distribution of biota throughout the Northern Hemisphere has been greatly affected by the climatic fluctuations and changing geography of the last 65 million years, i.e. during the Tertiary and Quaternary periods (Wolfe 1975; Milne and Abbott 2002). 15 million years drastically changed the vegetation of Europe, where species of previously widespread Tertiary humidtemperate forests found their refugia in the Balkan Peninsula, Carpathians and adjacent Anatolia (Milne and Abbott 2002; Lendvay et al 2016). The Balkan Peninsula is renowned as a refugium of several, previously more widespread, tree and shrub species. Many other tree species that in the Holocene expanded their ranges north of the Alps, had their glacial refugia on the Balkan Peninsula

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