Phyllanthus balgooyi (EuPhorbiacEaE s.l.), a nEw nickEl-hyPEraccumulating sPEciEs from Palawan and sabah

In the course of studies of ultramafic vegetation in the Philippines (Baker et al., 1992; Proctor et al., 1997, 2000a, b) it was noted that several collections identified as Phyllanthus lamprophyllus müll.arg. differed markedly from material collected on non-ultramafic sites and other ultramafic sites in the Malay Archipelago, which all had low nickel concentrations. leaf dry matter nickel concentrations in excess of 1.6% were subsequently measured in these plants, confirming a strong nickel hyperaccumulator status. When the stem or main root is slashed this Phyllanthus exudes a jade-green sap as a consequence of the extremely high ni concentrations in the phloem tissues, which contain 9% nickel on a dry weight basis. the only other instance of a plant with such a visibly apparent nickel accumulation in an exudate is the New Caledonian tree Sebertia acuminata (Sapotaceae), where the blue latex contains 25% nickel (Jaffré et al., 1976). the hyperaccumulating Phyllanthus specimens display a number of morphological differences to P. lamprophyllus. therefore, the new species P. balgooyi is described here. Phyllanthus balgooyi occurs in ultramafic sites in Palawan (Philippines) and Sabah (Malaysian Borneo). At least 17 specimens of this new species have been collected and deposited in the herbaria of kew and leiden alone since 1947. the earliest specimen known to us, however, was collected in 1886 by Vidal in Palawan. All of these were previously filed under P. lamprophyllus, or occasionally under P. buxifolius (Blume) müll.arg.

In the course of studies of ultramafic vegetation in the Philippines (Baker et al., 1992;Proctor et al., 1997Proctor et al., , 2000a it was noted that several collections identified as Phyllanthus lamprophyllus müll.arg. differed markedly from material collected on non-ultramafic sites and other ultramafic sites in the Malay Archipelago, which all had low nickel concentrations. leaf dry matter nickel concentrations in excess of 1.6% were subsequently measured in these plants, confirming a strong nickel hyperaccumulator status. When the stem or main root is slashed this Phyllanthus exudes a jade-green sap as a consequence of the extremely high ni concentrations in the phloem tissues, which contain 9% nickel on a dry weight basis. the only other instance of a plant with such a visibly apparent nickel accumulation in an exudate is the New Caledonian tree Sebertia acuminata (Sapotaceae), where the blue latex contains 25% nickel (Jaffré et al., 1976). the hyperaccumulating Phyllanthus specimens display a number of morphological differences to P. lamprophyllus. therefore, the new species P. balgooyi is described here. Phyllanthus balgooyi occurs in ultramafic sites in Palawan (Philippines) and Sabah (Malaysian Borneo). At least 17 specimens of this new species have been collected and deposited in the herbaria of kew and leiden alone since 1947. the earliest specimen known to us, however, was collected in 1886 by Vidal in Palawan. All of these were previously filed under P. lamprophyllus, or occasionally under P. buxifolius (Blume) müll.arg.
Phyllanthus lamprophyllus is the type of the initially monotypic section Emblicastrum first described by Müller (1866: 324) from Java. The species also occurs in Sulawesi, the Lesser Sunda Islands and the Moluccas (Airy Shaw, 1982: 32), The Philippines (Airy Shaw, 1983: 41), New Guinea (Airy Shaw, 1980a: 189) and Australia (Airy Shaw, 1980b: 666). The New Guinean and Australian specimens were first described as P. hellwigii Warb. Webster & airy Shaw (1971: 109) noted that the Philippine material of P. lamprophyllus should be referred to this species. later (airy Shaw, 1976: 361), the floral characters of sect. Emblicastrum müll.arg. that had been obscured by a rare mistake in Müller (1866) were clarified, and P. hellwigii was synonymized with P. lamprophyllus.
In his enumeration of Philippine Euphorbiaceae, Airy Shaw (1983) listed three specimens of the true P. lamprophyllus but did not remark on aberrant specimens from ultramafic sites. He had, however, wrapped the specimen PNH (Edaño) 178 which had been identified as 'Phyllanthus palawanensis merr. & Quisumb., n.sp.' in a type folder at kew, and noted on the leiden duplicate that he considered it to be a separate species. Phyllanthus palawanensis has never been validly described. We are designating this kew specimen as the holotype of our new species, but feel that the epithet suggested by merrill does not reflect the true distribution of the taxon. therefore, we name it after the eminent Malesian botanist M.M.J. van Balgooy.
We have been unable to find a Phyllanthus in the malay archipelago that resembles our new species more than P. lamprophyllus. Phyllanthus curranii c.B. rob. from the Philippines (Luzon) is very similar to P. lamprophyllus, and may be conspecific. Robinson (1909: 77) placed it in section Emblicastrum with P. lamprophyllus, but did not discuss the differences that led him to distinguish a new species. Phyllanthus curranii agrees in all points listed below with P. lamprophyllus. as far as can be ascertained from the collections held at the kew Herbarium, it seems to differ in the slightly smaller leaves and longer pistillate pedicels.
Another very similar plant is Phyllanthus robinsonii merr., known only from the type specimen from cebu (Philippines). merrill (1912: 405) placed it in section Emblicastrum with a question mark because the type bears only pistillate flowers. Distinguishing infrageneric characters of the staminate flowers remain unknown. Phyllanthus robinsonii was described as a separate taxon on account of its indistinct secondary leaf venation. otherwise, the type BS (Ramos) 11058 at Kew is very similar to P. lamprophyllus and P. curranii.
the main characters of the monoecious section Emblicastrum are staminate flowers with four sepals and discrete disc segments, two connate stamens with horizontally dehiscing anthers, and pistillate flowers with entire, more or less connate styles. Section Emblicastrum was placed in subgenus Eriococcus (Hassk.) croiz. & metc. by Webster (1957: 359) who suspected that the then monospecific sections Emblicastrum, Eriococcodes müll.arg. and Scepasma (Blume) Müll.Arg. "represent merely individual species with striking 'key' characters; a recasting of subg. Eriococcus along phylogenetic lines may result in radical changes in the circumscription of the constituent taxa". the clear physiological difference between P. balgooyi and P. lamprophyllus is visually expressed in the green exudate from the stem and root of the former species. a much more accessible character in which the new species differs from P. lamprophyllus is its conspicuous leaf venation (Fig. 1a). This type of venation seems to be unique among the Phyllanthus species in the malay archipelago, and resembles that of species of the Chamaecrista mimosoides (l.) greene-group in the leguminosae. in contrast, P. lamprophyllus has often indistinct, numerous (8-12) pairs of secondary veins that are much thinner and shorter than the midvein, branch off evenly over the length of the leaf, and run straight to the midvein in an angle of c. 45° (Fig. 1m).