Hedbergia decurva

Hedbergia decurva
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Lamiales
Family:	Orobanchaceae
Tribe:	Rhinantheae
Genus:	Hedbergia
Species:	H. decurva
Binomial name
Hedbergia decurva A. Fleischm. & Heubl [1]
Synonyms
Bartsia decurva Hochst. ex Benth.

Hedbergia decurva, formerly Bartsia decurva, is a hemiparasitic species of flowering plants in the family Orobanchaceae.[2][1]

Description

Hedbergia decurva is a shrub covered in sticky glandular hairs and few non-glandular hairs. It reaches 50–200 cm (20–79 in) in height, having thin, woody, upright, sparsely branching stems. The mostly upright, narrowly ovate seated leaves of 8–36 mm (0.31–1.42 in) long, have rounded teeth along the margins that are mostly rolled downwards, and are set in opposite pairs. The shortly stalked flowers are set in a raceme towards the tip of the stems in the axils of leaflike bracts. The sepals are merged into a calyx with 4 lobes with deeper incisions on the midline and shallower incisions left and right. The yellow to yellowish brown petals are merged into a stongly mirror-symmetric corolla, with a long, in the upper part distinctly curved tube, topped by a helmet-shaped upper lip that encloses the anthers and a spreading, three-lobed lower lip that has two bulges in front of the throat of the tube. The filaments of the 4 stamens have largely merged with the upper lip of the corolla and are topped by shaggy anthers that each have 2 district spines at their lower end. The style is on top of a shaggy ovary and tipped by a club-shaped stigma. The narrowly elliptical seeds are 0.6–1.9 mm (0.024–0.075 in) long, with several ribs along their length. The species probably has 14 pairs of homologous chromosomes (2n=28).[3]

Differences with related species

Hedbergia decurva can be distinguished in having a curved upper corolla tube and spines on the lower end of the anthers, whereas Hedbergia longiflora has a straight corolla tube and acute but not spined anthers.[3]

Distribution

Hedbergia decurva occurs in the high mountains of Ethiopia, eastern Uganda, Kenya and Tanzania, above approximately 2,500 m (1.6 mi) where it grows in ericaceous and alpine vegetations.[3]

Phylogeny

The phylogeny of the genera of Rhinantheae has been explored using molecular characters.[1][4][5][6][7] Hedbergia decurva groups with Hedbergia longiflora and Hedbergia abyssinica into a Hedbergia clade nested within the core Rhinantheae. These three taxa share evolutionary affinities with genera Tozzia, Bellardia, Neobartsia, Parentucellia, and Odontites.

Genus-level cladogram of tribe Rhinantheae.

Rhinantheae               Melampyrum               Rhynchocorys               Lathraea   Rhinanthus   Core Rhinantheae               Bartsia sensu stricto (Bartsia alpina)             Euphrasia             Hedbergia   (including Bartsia decurva + B. longiflora)   Tozzia   Odontites sensu lato   (including Bartsiella   and Bornmuellerantha)             Bellardia             Neobartsia (New World Bartsia)   Parentucellia

The cladogram has been reconstructed from nuclear DNA (ribosomal ITS) and plastid DNA (rps16 intron, trnK, and other regions) molecular characters.[5][7][1][4][6]

References

1. Scheunert, Agnes; Fleischmann, Andreas; Olano-Marín, Catalina; Bräuchler, Christian; Heubl, Günther (2012-12-14). "Phylogeny of tribe Rhinantheae (Orobanchaceae) with a focus on biogeography, cytology and re-examination of generic concepts". Taxon. 61 (6): 1269–1285. doi:10.1002/tax.616008.
2. "Hedbergia decurva | International Plant Names Index". www.ipni.org. Retrieved 2020-05-09.
3. Olof Hedberg, Björn Ericson, Anna Grill-Willén, Asfaw Hunde, Leif Källston, Ola Löfgren, Thomas Rooth, Olaf Ryding (1979). "The yellow-flowered species of Bartsia (Scrophulariaceae) in Tropical Africa". Norwegian Journal of Botany. 26: 1–9.
4. Těšitel, Jakub; Říha, Pavel; Svobodová, Šárka; Malinová, Tamara; Štech, Milan (2010-10-28). "Phylogeny, Life History Evolution and Biogeography of the Rhinanthoid Orobanchaceae". Folia Geobotanica. 45 (4): 347–367. doi:10.1007/s12224-010-9089-y. ISSN 1211-9520. S2CID 39873516.
5. McNeal, J. R.; Bennett, J. R.; Wolfe, A. D.; Mathews, S. (2013-05-01). "Phylogeny and origins of holoparasitism in Orobanchaceae". American Journal of Botany. 100 (5): 971–983. doi:10.3732/ajb.1200448. ISSN 0002-9122. PMID 23608647.
6. Uribe-Convers, Simon; Tank, David C. (2016-09-01). "Phylogenetic Revision of the Genus Bartsia (Orobanchaceae): Disjunct Distributions Correlate to Independent Lineages". Systematic Botany. 41 (3): 672–684. doi:10.1600/036364416X692299. S2CID 88752480.
7. Pinto-Carrasco, Daniel; Scheunert, Agnes; Heubl, Günther; Rico, Enrique; Martínez-Ortegai, M. Montserrat (2017). "Unravelling the phylogeny of the root-hemiparasitic genus Odontites (tribe Rhinantheae, Orobanchaceae): Evidence for five main lineages". Taxon. 66 (4): 886–908. doi:10.12705/664.6. hdl:10366/141004. ISSN 1996-8175.