Monday, May 21, 2018

[Botany • 2018] Phyllanthus rufuschaneyi (Phyllanthaceae) • A New Nickel Hyperaccumulator from Sabah (Borneo Island) with Potential for Tropical Agromining

Phyllanthus rufuschaneyi Welzen, R.W.Bouman & Ent

in Bouman, van Welzen, Sumail, et al., 2018.

Background: Nickel hyperaccumulator plants are of much interest for their evolution and unique ecophysiology, and also for potential applications in agromining—a novel technology that uses plants to extract valuable metals from soil. The majority of nickel hyperaccumulators are known from ultramafc soils in tropical regions (Cuba, New Caledonia and Southeast Asia), and one genus, Phyllanthus (Phyllanthaceae), is globally the most represented taxonomic entity. A number of tropical Phyllanthus-species have the potential to be used as ‘metal crops’ in agromining operations mainly because of their ease in cultivation and their ability to attain high nickel concentrations and biomass yields. 

Results: One of the most promising species globally for agromining, is the here newly described species Phyllanthus rufuschaneyi. This species can be classifed in subgenus Gomphidium on account of its staminate nectar disc and pistillate entire style and represents the most western species of this diverse group. The fower structure indicates that this species is probably pollinated by Epicephala moths. 

Conclusions: Phyllanthus rufuschaneyi is an extremely rare taxon in the wild, restricted to Lompoyou Hill near Kinabalu Park in Sabah, Malaysia. Its utilization in agromining will be a mechanism for conservation of the taxon, and highlights the importance of habitat and germplasm preservation if rare species are to be used in novel green technologies. 

Keywords: Epicephala pollination, Nickel hyperaccumulation, Phyllanthaceae, Phyllanthus subgenus Gomphidium, Sabah

Fig. 2 Detail of Phyllanthus rufuschaneyi plants.
a Inflorescences of P. rufuschaneyi, note the difference between main stem and side stem with at the base small structures that signal phyllanthoid branching; b fruit capsules of P. rufuschaneyi. Images by A. van der Ent

Fig. 3 Phyllanthus rufuschaneyi Welzen, R.W.Bouman & Ent:
a a branch with only scars of cataphylls and cataphyllary stipules present at the base of branchlets as these are caducous (drawn from herbarium specimen with leaves glued sideways and staminate flowers sometimes upright instead of hanging); b detail of sidebranch with leaves and staminate flowers in natural position; c staminate flower; d staminate flower with part of sepals removed showing disc glands and androecium; e pistillate flower; f pistillate flower with part of sepals removed showing disc glands and ovary; g fruit

(a, c, d Daim Endau 225; b Lomudin Tadon g257; e, f SNP 32987; g Lomudin Tadon 257; all SNP). Drawing by Esmée Winkel (2017)

Phyllanthus rufuschaneyi Welzen, R.W.Bouman and Ent, sp. nov.

—TYPE: MALAYSIA. Sabah, near Kampong Nalumad, eastern boundary Kinabalu Park, Lompoyou Hill, Antony Van der Ent et al. SNP 32987! (holo SNP; iso L). 
Paratype: SNP 22039!, Lompoyou Hill, Sabah, Malaysia (Figs. 2, 3, 4). 

This species is most similar to P. securinegoides from the Philippines, from which it can be distinguished by its smaller leaves, staminate fowers with connate flaments and pistillate fowers with connate tubular stigmas

Etymology: The specific epithet “rufuschaneyi” honours Dr. Rufus L. Chaney (b. 1942), an agronomist who is widely credited for inventing phytomining (agromining) (Chaney 1983), leading to the technology being patented (Chaney et al. 1998). Dr. Chaney has worked for 47 years at the USDA Agricultural Research Service (USA) on risk assessment for metals in soils and crops, and the food-chain transfer and bioavailability of soil and crop metals to humans. He published over 490 publications and won the Gordon Award for Lifetime Achievement and Excellence in Phytoremediation Research. The fact that P. rufuschaneyi is the most promising tropical Ni ‘metal crop’ presently known, makes this recognition fitting.

Distribution, habitat and ecology: Phyllanthus rufuschaneyi is known only from two populations; one (very small) population at the foot of Bukit Hampuan, and another larger population on Lompoyou Hill approximately 5 km from the first population. The habitat in both localities is open secondary scrub that has been affected by recurring forest fires (Fig. 1). Lompoyou Hill is close to the villages of Nalumad and Pahu. The hill (400 m asl) has been burnt at least once as a result of an uncontrolled forest fire in 1998. Prior to burning, the site was already disturbed by logging. The area has a short and open scrub community (dominated by shrubs 1–3 m tall) with pioneer species such as Macaranga kinabaluensis Airy Shaw (Euphorbiaceae). In this habitat type several other Ni hyperaccumulator plant species occur, including Phyllanthus balgooyi, Actephila alanbakeri, Mischocarpus sundaicus Blume (Sapindaceae), and Xylosma luzonensis Clos (Salicaceae). The local conditions are xeric, and the soils are shallow and heavily eroded with limited amounts of organic matter. In pot experiments P. rufuschaneyi responded negatively to increasing organic matter amendments (Nkrumah et al. 2017). Phyllanthus rufuschaneyi occurs exclusively on these young eroded soils (hypermagnesian Cambisols) that occur at low elevation (700 m asl) on strongly serpentinised bedrock. These soils have extremely high magnesium (Mg) to calcium (Ca), circum-neutral pH, and high available Ni as a result of the disintegration of phyllosilicates and re-sorption onto secondary iron (Fe)-oxides or high-charge clays (Echevarria 2018). In Sabah, Ni hyperaccumulator plant species are restricted to these soils with a pH > 6.3 and relatively high total soil Ni concentrations > 630 μg g−1 (Van der Ent et al. 2016b).

Roderick Bouman, Peter van Welzen, Sukaibin Sumail , Guillaume Echevarria, Peter D. Erskine and Antony van der Ent. 2018. Phyllanthus rufuschaneyi: A New Nickel Hyperaccumulator from Sabah (Borneo Island) with Potential for Tropical Agromining.  Botanical Studies: An International Journal. 59:9.  DOI: 10.1186/s40529-018-0225-y

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