Phylogeny and Biogeography of Ivies (Hedera spp., Araliaceae), a Polyploid Complex of Woody Vines

Abstract

Ivy (Hederá spp., Araliaceae) is a polyploid complex of woody vines. Native to Eurasia and northern Africa, ivy is cultivated worldwide and has become an aggressive invader of North American forests. Despite its ecological impacts and economic significance to the horticultural industry, the taxonomy of Hederá is controversial and historical relationships are poorly defined. Here we characterize the phylogeny of Hederá based on the low-copy nuclear locus Granule-bound starch synthase I (GBSSI) and twelve non-coding cpDNA regions. Maximum parsimony and Bayesian analyses of both data sets identified Hederá as monophyletic. For GBSSI, we isolated eighteen haplotypes that were widely shared across species. There was no evidence of fixed heterozygosity or haplotype additivity in polyploids, suggesting possible autopolyploid origins. For cpDNA, we isolated sixteen haplotypes that were highly structured by geography. Haplotype diversity and phylogenetic structure were greatest in northern Africa and southern Europe. Thus, while most members of the Araliaceae reside in tropical and subtropical Asia, the early diversification of Udcm probably occurred in the Mediterranean Basin. Geographically-structured clades included diploid and polyploid species, suggesting that genome duplication has occurred repeatedly in the genus. Closely-related ivies often differed in leaf size and trichome morphology, indicating evolutionary lability of traits traditionally used for classification. Nonetheless, we recovered similar or identical DNA sequences within morphologically-defined species. Notable exceptions included southern populations of H. helix (H. helix subsp. caucasigena and H. helix subsp. rhizomatifera) that had cpDNA haplotypes distinct from those of central and northern Europe (H. helix subsp. helix).

Status clarification and disposal of Carrière’s ivy names

“…Carrière describing these ivies fell into oblivion, largely because most of them have always been considered, as he supposed, varieties and forms of H. helix. Nevertheless, in recent years his work has been claimed to name the ivy from Azores Islands, as most authors (McAllister & Rutherford, 1997;López González, 2001;Schäfer, 2002Schäfer, , 2003Valcárcel & al., 2003;Green & al., 2011;Schäfer & al., 2011) consider it as a new species: H. azorica Carrière, Rev. Hort.…”

“…Some of these names have recently been used as names of accepted species in the genus Hedera L. (Araliaceae). Such is the case of Hedera azorica Carrière, a name that many authors (McAllister & Rutherford, 1997;López González, 2001;Schäfer, 2002Schäfer, , 2003Valcárcel & al., 2003;Green & al., 2011;Schäfer & al., 2011) used for the plant growing on the Atlantic islands indicated by its specific epithet, and indeed attributed the name to E.A. Carrière ("Elie Abel Carrière 1818-1896.…”

Hedera crebrescens (Araliaceae) a newly identifi ed diploid taxon and triploid ivies from Hungary

“…Geographical groups of taxa can include diff erent ploidy levels, diploids, and polyploids. Th ese studies also revealed that formerly used morphological traits such as trichome morphology are not considered evolutionarily stable in ivies (Green et al 2011, Vargas et al 1999.…”

“…In the last decades several morphological (Ackerfield and Wen 2002, Kost et al 2003, Sulgrove 2004, Valcárcel and Vargas 2010) and molecular studies (Vargas et al 1999, Grivet and Petit 2002, Green et al 2011 were performed on Hedera taxa with the aim of revealing phylogenetic relationships and evolution. However, molecular studies followed by cytometric measurements revealed that polyploidy was the major phenomena in the evolution of Hedera species, and might have taken place several times independently in diff erent lineages (Green et al 2011).…”

“…However, molecular studies followed by cytometric measurements revealed that polyploidy was the major phenomena in the evolution of Hedera species, and might have taken place several times independently in diff erent lineages (Green et al 2011). Geographical groups of taxa can include diff erent ploidy levels, diploids, and polyploids.…”