Hedyotis hamiguitanensis (Rubiaceae: Spermacoceae), a new species from Mt. Hamiguitan, Davao Oriental, Philippines and its systematic position in Hedyotis

Propa Joy R. Santor, College of Science, University of Santo Tomas

Duane Dominic B. Santiago, College of Science, University of Santo Tomas

Conrado Joshua V. Mataga, College of Science, University of Santo Tomas

Elyjha S. Gabriel, College of Science, University of Santo Tomas

Grecebio Jonathan D. Alejandro, The Graduate School, University of Santo Tomas

Hedyotis Linnaeus (1753: 101) is part of the Hedyotis-Oldenlandia complex, a taxonomically confusing group that was formerly placed in the tribe Hedyotideae, which is now part of tribe Spermacoceae (Bremer 1996; Andersson and Rova 1999; Bremer and Manen 2000).

The genus has long been controversial because of the lack of taxonomic delimitation and molecular data (Terrell and Robinson 2003). Recent phylogenetic analyses based on nuclear and plastid sequences of Asian-Pacific taxa from this group have identified 13 well-supported monophyletic genera (Neupane et al., 2015). Diagnostic characters such as habit, fruit type, seed form, and pollen type were compared to the phylogeny for characterizing the clades (Kårehed et al 2008; Groeninckx et al. 2009; Guo et al. B 2013; Wikström et al. 2013; Neupane et al. 2015). In the latest revision (Neupane et al. 2015), members of Hedyotis s.str. included species from Sri Lanka, India, SE China, Indo-Chi-na, Malesia, Papuasia, Northwest Pacific, and Australia. The recent studies lack Hedyotis species occurring in the Philippines .

Hedyotis is characterized by its habit –suffrutescent herbs, shrubs, or small trees –, its capsules with apex not protruding beyond the calyx lobes, the septicidal dehiscence usually followed by a partial api-cal loculicidal dehiscence that sometimes results in two semi-split valves and, the dorsiventrally compressed seeds (Wikström et al. 2013). The flowers have a pubes-cent corolla tube and pollen with 3 -4 ectoapertures, endoapertures shaped as an endocingulum and a tectum with a double reticulum pattern (Neupane et al. 2015). There are approximately 180 species in Hedyotis (Neu-pane et al. 2015),36 of which occur in the Philippines (Pelser et al. 2011). During fieldwork of the Thomasian Angiosperm Phylogeny and Barcoding Group (TAPBG) on Mt.Hamiguitan, Davao Oriental, Philippines, an interesting taxon was discovered. Two populations were observed, one in mossy forests and the other in pygmy forests on the same mountain. The collected material is morphologically similar to Hedyotis whiteheadii Merrill (1907: 303) and H. schlechteri Merrill & Perry (1945: 1), but detailed comparison showed that these two species dif-fer from the newly collected material by their vegetative and inflorescence morphology. Therefore, a new Hedyotis species is here described and illustrated. We also includ-ed the new species in a maximum likelihood and Bayes-ian phylogenetic analysis of Hedyotis s.str. (sensu Neupane et al. 2015) based on chloroplast (rps16, petD) and nuclear ribosomal (ITS, ETS) nucleotide sequence data to elucidate its position within the genus.

DOI: https://doi.org/10.36253/jopt-10651

Read Full Text: https://oaj.fupress.net/index.php/webbia/article/view/10651

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