Phylogeny and historical biogeography analysis support Caucasian and Mediterranean centres of origin of key holoparasitic Orobancheae (Orobanchaceae) lineages.

Renata Piwowarczyk,Grzegorz Góralski,Adam C Schneider,Magdalena Denysenko-Bennett,Anna Burda,Andrzej J Joachimiak,Óscar Sánchez Pedraja,Dagmara Kwolek,Karolina Ruraż

doi:10.3897/phytokeys.174.62524

Abstract

The extensive diversity of the tribe Orobancheae, the most species-rich lineage of holoparasitic Orobanchaceae, is concentrated in the Caucasus and Mediterranean regions of the Old World. This extant diversity has inspired hypotheses that these regions are also centres of origin of its key lineages, however the ability to test hypotheses has been limited by a lack of sampling and phylogenetic information about the species, especially in the Caucasus region. First, we assessed the phylogenetic relationships of several poorly known, problematic, or newly described species and host-races of four genera of Orobancheae occurring in the Caucasus region–Cistanche, Phelypaea, Phelipanche and Orobanche–using nuclear ribosomal (ITS) and plastid (trnL–trnF) sequence data. Then we applied a probablistic dispersal-extinction-cladogenesis model of historical biogeography across a more inclusive clade of holoparasites, to explicitly test hypotheses of Orobancheae diversification and historical biogeography shifts. In sum, we sampled 548 sequences (including 196 newly generated) from 13 genera, 140 species, and 175 taxa across 44 countries. We find that the Western Asia (particularly the Caucasus) and the Mediterranean are the centre of origin for large clades of holoparasitic Orobancheae within the last 6 million years. In the Caucasus, the centres of diversity are composed both of long-branch taxa and shallow, recently diversified clades, while Orobancheae diversity in the Mediterranean appears to represent mainly recent diversification.

Highlights

The tribe Orobancheae is the oldest and most species-rich of the three lineages of holoparasites comprising the cosmopolitan family Orobanchaceae, with a crown age dating to the mid-Miocene (McNeal et al 2013; Schneider and Moore 2017)
The Mediterranean and the Caucasus have been hypothesised as refugia for both plant and animal lineages during the Pleistocene ice ages (Taberlet et al 1998; Hewitt 1999; Lumibao et al 2017), and some authors even propose the Caucasus together with the Middle East and Central Asian high mountains as the main area of origin of Old World broomrapes (Orobanche and Phelipanche, Rätzel and Uhlich 2004)
For the initial phylogenetic analysis, we studied Caucasian species of Cistanche, Phelypaea, Phelipanche and Orobanche, mainly collected from Georgia, Armenia, Azerbaijan and Russia between 2014 and 2019

Summary

Introduction

The tribe Orobancheae is the oldest and most species-rich of the three lineages of holoparasites comprising the cosmopolitan family Orobanchaceae, with a crown age dating to the mid-Miocene (McNeal et al 2013; Schneider and Moore 2017). Str., and hemiparasites traditionally included in Scrophulariaceae (Olmstead et al 2001; McNeal et al 2013). This is the largest parasitic plant family with 102 genera and over 2,100 species (Nickrent 2020) which together with its variety of trophic modes makes it a valuable model for studying the evolution and physiology of parasitism (Westwood et al 2010). The Mediterranean Basin and Caucasus region of western Asia are centres of extant diversity for the two most diverse genera in the Orobancheae, Orobanche L. and Phelipanche Pomel The Mediterranean and the Caucasus have been hypothesised as refugia for both plant and animal lineages during the Pleistocene ice ages (Taberlet et al 1998; Hewitt 1999; Lumibao et al 2017), and some authors even propose the Caucasus together with the Middle East and Central Asian high mountains as the main area of origin of Old World broomrapes (Orobanche and Phelipanche, Rätzel and Uhlich 2004)

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