Abstract
Phtheirospermum (Orobanchaceae), a hemiparasitic genus of Eastern Asia, is characterized by having long and viscous glandular hairs on stems and leaves. Despite this unifying character, previous phylogenetic analyses indicate that Phtheirospermum is polyphyletic, with Phtheirospermum japonicum allied with tribe Pedicularideae and members of the Ph. tenuisectum complex allied with members of tribe Rhinantheae. However, no analyses to date have included broad phylogenetic sampling necessary to test the monophyly of Phtheirospermum species, and to place these species into the existing subfamiliar taxonomic organization of Orobanchaceae. Two other genera of uncertain phylogenetic placement are Brandisia and Pterygiella, also both of Eastern Asia. In this study, broadly sampled phylogenetic analyses of nrITS and plastid DNA revealed hard incongruence between these datasets in the placement of Brandisia. However, both nrITS and the plastid datasets supported the placement of Ph. japonicum within tribe Pedicularideae, and a separate clade consisting of the Ph. tenuisectum complex and a monophyletic Pterygiella. Analyses were largely in agreement that Pterygiella, the Ptheirospermum complex, and Xizangia form a clade not nested within any of the monophyletic tribes of Orobanchaceae recognized to date. Ph. japonicum, a model species for parasitic plant research, is widely distributed in Eastern Asia. Despite this broad distribution, both nrITS and plastid DNA regions from a wide sampling of this species showed high genetic identity, suggesting that the wide species range is likely due to a recent population expansion. The Ph. tenuisectum complex is mainly distributed in the Hengduan Mountains region. Two cryptic species were identified by both phylogenetic analyses and morphological characters. Relationships among species of the Ph. tenuisectum complex and Pterygiella remain uncertain. Estimated divergence ages of the Ph. tenuisectum complex corresponding to the last two uplifts of the Qinghai–Tibet Plateau at around 8.0–7.0 Mya and 3.6–1.5 Mya indicated that the development of a hot-dry valley climate during these uplifts may have driven species diversification in the Ph. tenuisectum complex.
Highlights
Mountain ranges often support a high diversity of plant life (Favre et al, 2015; Hughes and Atchison, 2015)
Based on examination of herbarium specimens, we found that Ph. tenuisectum varied extensively in habit, leaf morphology, calyx form, and corolla shape
To evaluate sequence matrix characteristics, we classified the samples of Phtheirospermum spp. and Pterygiella spp. in several groups
Summary
Mountain ranges often support a high diversity of plant life (Favre et al, 2015; Hughes and Atchison, 2015). The Hengduan Mountains region is the core of the Mountains of Southwest China Biodiversity Hotspot (Zhang et al, 2009; Boufford, 2014). This region is characterized by extremely complex topography, with altitudes ranging from less than 2,000 meters in some valley floors to 7,558 meters at the summit of Gongga Mountain. Species richness and diversity in the Hengduan Mountains region have been ascribed to the accumulation of migrants and in situ diversification accelerated by the uplift of the mountains (Wen et al, 2014; Xing and Ree, 2017). This uplift event may have contributed to recent diversification of species in Phtheirospermum Bunge (Orobanchaceae), most of which can be found in the Hengduan Mountains region
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
