Origin of Mediterranean insular endemics in the Boraginales: integrative evidence from molecular dating and ancestral area reconstruction

Abstract

Aim The presence of numerous reliable fossils and the occurrence of many endemic island species make the Boraginales particularly suitable for integrative biogeographical studies. In this paper we aim to elucidate the time frame and events associated with the origin of selected borages endemic to the Mediterranean climate zone. More specifically, we describe and examine the alternative palaeo‐ and neoendemic hypotheses for their origin. Location Corsica and Sardinia (continental fragment islands) and the Canary Islands (an oceanic island archipelago). Methods Eighty‐nine accessions, representing 30 genera from five families ascribed to the Boraginales, were examined for six chloroplast DNA regions. We used an integrative approach including phylogenetic analyses (MrBayes), Bayesian molecular dating (T3 package) with four fossil constraints on nodes, and biogeographical reconstructions (diva) to elucidate the temporal and spatial origins of the Corso‐Sardinian and Canary Island endemics. Results Species of Echium endemic to the Canary Islands diverged from their continental sister clade during the Miocene (15.3 ± 5.4 Ma), probably after the rise of the oldest islands (c. 20 Ma). Corso‐Sardinian endemics of Borago diverged from their primarily North African sister clade during the late Miocene‐Pliocene (c. 6.9 ± 3.6 Ma), well after the initial fragmentation of the islands (c. 30 Ma). Similarly, Corso‐Sardinian endemics of Anchusa diverged from the South African Anchusa capensis during the Pliocene–Pleistocene (c. 2.7 ± 2.1 Ma). Main conclusions The present study reveals an Anatolian origin for Anchusa, Borago and Echium and underlines the importance of the Eastern Mediterranean region as a possible reservoir for plant evolution in the Mediterranean Basin. For Anchusa and Borago, the divergence from their respective sister clades on the two types of islands post‐dated the formation of the islands, thus supporting the neo‐endemic hypothesis, whereas the dating results for the origin of Echium endemics were less conclusive.

Associations between sex‐organ deployment and morph bias in related heterostylous taxa with different stylar polymorphisms

“…Th e primary rationale for the use of phylogenetically based statistical methods was the expected nonindependence among species trait values due to their phylogenetic relatedness ( Felsenstein, 1985 ). Th e branching pattern and estimated times of divergence in our Bayesian analysis based on six DNA regions was largely consistent with previous work, although here we obtained stronger support for most clades ( Ferrero et al, 2009 ;Mansion et al, 2009 ). We found a phylogenetic signal when analyzing the infl uence of the type of polymorphism on morph-ratio bias.…”

“…Most taxa in our trees belonged to Boraginaceae. Outgroup taxa consisted of members of Hydrophyllaceae, Heliotropiaceae, Cordiaceae, and Ehretiaceae ( Mansion et al, 2009 ). Th e six DNA regions used to infer the trees were: trn L intron, trn L -trn F intergenic spacer, ndh F gene, the rbc L gene, part of the trn K intron, and the mat K gene (both coded as the mat K region).…”

The borage family (Boraginaceae s.str.): A revised infrafamilial classification based on new phylogenetic evidence, with emphasis on the placement of some enigmatic genera

“…In order to address these topics, a phylogenetic analysis based on maximum likelihood and Bayesian methods, using the chloroplast markers trnL-trnF, rps16, and trnS-G, and the internal transcribed spacer of nuclear ribosomal DNA (ITS), was performed. These markers have been used successfully to study the phylogeny and evolution of the Boraginales (Mansion & al., 2009;Weigend & al., 2009Weigend & al., , 2013Weigend & al., , 2014Luebert & al., 2011; and therefore are suitable markers to address the goals of this study.…”

A reappraisal of the genus Megacaryon (Boraginaceae, Lithospermeae) based on molecular, morphological, and karyological evidence

“…Habit, life cycle and other vegetative characters are widely variable. The herbaceous habit is exclusive in the primary diversity centre in the west Mediterranean, continental Europe, and western Asia, while the woody, shrubby habit is characteristic of most Macaronesian endemic species that originated from mainland ancestors through a massive radiation in the Canary, Cape Verde, and Madeira islands (B€ ohle, Hilger, & Martin, 1996;Mansion, Selvi, Guggisberg, & Conti, 2009).…”