Adam C Schneider1, Alison E L Colwell2, Gerald M Schneeweiss3, Bruce G Baldwin4. 1. Department of Integrative Biology, 1005 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA Jepson Herbarium, 1001 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA acschneider@berkeley.edu. 2. Jepson Herbarium, 1001 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA. 3. Department of Botany and Biodiversity Research, University of Vienna, 1030 Vienna, Austria. 4. Department of Integrative Biology, 1005 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA Jepson Herbarium, 1001 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA.
Abstract
BACKGROUND AND AIMS: The broomrapes, Orobanche sensu lato (Orobanchaceae), are common root parasites found across Eurasia, Africa and the Americas. All species native to the western hemisphere, recognized as Orobanche sections Gymnocaulis and Nothaphyllon, form a clade that has a centre of diversity in western North America, but also includes four disjunct species in central and southern South America. The wide ecological distribution coupled with moderate taxonomic diversity make this clade a valuable model system for studying the role, if any, of host-switching in driving the diversification of plant parasites. METHODS: Two spacer regions of ribosomal nuclear DNA (ITS + ETS), three plastid regions and one low-copy nuclear gene were sampled from 163 exemplars of Orobanche from across the native geographic range in order to infer a detailed phylogeny. Together with comprehensive data on the parasites' native host ranges, associations between phylogenetic lineages and host specificity are tested. KEY RESULTS: Within the two currently recognized species of O. sect. Gymnocaulis, seven strongly supported clades were found. While commonly sympatric, members of these clades each had unique host associations. Strong support for cryptic host-specific diversity was also found in sect. Nothaphyllon, while other taxonomic species were well supported. We also find strong evidence for multiple amphitropical dispersals from central North America into South America. CONCLUSIONS: Host-switching is an important driver of diversification in western hemisphere broomrapes, where host specificity has been grossly underestimated. More broadly, host specificity and host-switching probably play fundamental roles in the speciation of parasitic plants.
BACKGROUND AND AIMS: The broomrapes, Orobanche sensu lato (Orobanchaceae), are common root parasites found across Eurasia, Africa and the Americas. All species native to the western hemisphere, recognized as Orobanche sections Gymnocaulis and Nothaphyllon, form a clade that has a centre of diversity in western North America, but also includes four disjunct species in central and southern South America. The wide ecological distribution coupled with moderate taxonomic diversity make this clade a valuable model system for studying the role, if any, of host-switching in driving the diversification of plant parasites. METHODS: Two spacer regions of ribosomal nuclear DNA (ITS + ETS), three plastid regions and one low-copy nuclear gene were sampled from 163 exemplars of Orobanche from across the native geographic range in order to infer a detailed phylogeny. Together with comprehensive data on the parasites' native host ranges, associations between phylogenetic lineages and host specificity are tested. KEY RESULTS: Within the two currently recognized species of O. sect. Gymnocaulis, seven strongly supported clades were found. While commonly sympatric, members of these clades each had unique host associations. Strong support for cryptic host-specific diversity was also found in sect. Nothaphyllon, while other taxonomic species were well supported. We also find strong evidence for multiple amphitropical dispersals from central North America into South America. CONCLUSIONS: Host-switching is an important driver of diversification in western hemisphere broomrapes, where host specificity has been grossly underestimated. More broadly, host specificity and host-switching probably play fundamental roles in the speciation of parasitic plants.
Authors: Susann Wicke; Kai F Müller; Claude W de Pamphilis; Dietmar Quandt; Norman J Wickett; Yan Zhang; Susanne S Renner; Gerald M Schneeweiss Journal: Plant Cell Date: 2013-10-18 Impact factor: 11.277
Authors: Fredrik Ronquist; Maxim Teslenko; Paul van der Mark; Daniel L Ayres; Aaron Darling; Sebastian Höhna; Bret Larget; Liang Liu; Marc A Suchard; John P Huelsenbeck Journal: Syst Biol Date: 2012-02-22 Impact factor: 15.683