Two New, Glaucous-Leaved Species of Isopogon (Proteaceae: Proteoideae: Leucadendreae) from South-Western Australia
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M.Nuytsia Hislop 20: & 169–181 B.L.Rye, (2010) Two new, glaucous-leaved species of Isopogon 169 Two new, glaucous-leaved species of Isopogon (Proteaceae: Proteoideae: Leucadendreae) from south-western Australia Michael Hislop and Barbara L. Rye Western Australian Herbarium, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, Western Australia 6983 Abstract Hislop, M. & Rye, B.L. Two new, glaucous-leaved species of Isopogon (Proteaceae: Proteoideae: Leucadendreae) from south-western Australia. Nuytsia 20: 169–181 (2010). Two new species and two new subspecies with simple, flat, glaucous leaves are described:Isopogon panduratus Hislop & Rye, I. panduratus subsp. palustris Hislop & Rye, I. pruinosus Hislop & Rye and I. pruinosus subsp. glabellus Hislop & Rye. Their distributions are mapped and the first three are illustrated. The four new taxa belong in a species group that includes Isopogon axillaris R.Br. and I. buxifolius R.Br. s. lat. Isopogon panduratus subsp. palustris has conservation priority. Introduction Isopogon R.Br. ex J. Knight is a moderately large genus belonging to the subfamily Proteoideae and occurring in southern mainland Australia and on islands in the Bass Strait. The genus was until recently included in the tribe Conospermeae, but as a result of a comprehensive molecular analysis of the family, utilizing published and unpublished DNA sequence data from several genomic regions, it has been transferred to a newly described tribe, Leucadendreae (Weston & Barker 2006). Foreman’s treatment (1995) of Isopogon in Volume 16 of Flora of Australia was curtailed by ill health caused in part by an allergic reaction to contact with the two proteaceous genera, Isopogon and Petrophile, that were then the subject of his research (Alex George, pers. com.). It is probable that he would have recognised additional species had he been able to complete his revision of the genus prior to publication of the flora treatment. As it was however he retained the pre-existing, taxonomic status quo in the most complex group of western species, those with simple, thick, flat leaves allied to Isopogon buxifolius. This did not adequately reflect the group’s diversity and led him to circumscribe some species, especially I. buxifolius very broadly, while at the same time leaving numerous specimens largely unresolved. Foreman was clearly unsure what to do with the glaucous-leaved specimens now attributable to the two species described below. He annotated these in a variety of ways, sometimes identifying them as named species such as I. axillaris or I. polycephalus, at other times using informal names or indicating affinities only, e.g. ‘Isopogon sp. 2’, ‘I. attenuatus complex’ or ‘I. polycephalus variant’. Bentham (1870) included the simple, flat-leaved species in sectionHypsanthus (Endl.)Benth, however it is clear that this subgeneric grouping, at least as applied by Bentham, is an artificial one. hislop 591.indd 169 22/06/2010 9:39:25 AM 170 Nuytsia Vol. 20 (2010) It was not long after the flora treatment ofIsopogon appeared that its limitations became apparent. Even before its publication, the name Isopogon sp. Watheroo (D. Foreman 477) had been added to the Census of Western Australian Plants by ecologist E.A. (Ted) Griffin for a species with glaucous leaves that he had observed while working on vegetation surveys of the Geraldton sandplains. In its original application that name was restricted to populations occurring north of Perth and included collections of a second taxon that was later segregated as I. sp. Badgingarra (A.S. George 14200). These northern taxa are described here as the two subspecies of Isopogon panduratus Hislop & Rye. The concept of I. sp. Watheroo was later expanded to include plants with a generally similar morphology from the central and south-eastern wheatbelt which are described below as I. pruinosus Hislop & Rye. Apart from the taxa treated in this paper, an additional five informal names have been allocated to new Western Australian members of the genus, four of which apply to other species from the Isopogon buxifolius group. These will be described in a separate paper. Methods This study was based on an examination of collections housed at PERTH. All measurements were obtained from dried specimens. Although the leaves of members of the simple, flat-leaved group are often distinctly narrowed towards the base, there is no corresponding change in tissue type that would indicate the presence of a petiole. They are therefore considered here to be essentially sessile, and the leaf length was therefore measured from the apex to the point of attachment. The inflorescence- subtending leaves grade into involucral bracts across several very short, spirally-arranged nodes. There are several whorls of involucral bracts and the outer was considered to begin with the first bract lacking any terminal herbaceous appendage (i.e. vestigial leaf lamina). Measurements were taken, and observations made, of the outer and innermost whorls. The tepal limb was measured from the point of insertion of the filament to the tepal apex, excluding the hair tuft. Most species in the simple, flat-leaved group (including the two described here) have the distinctively shaped pollen presenter which is characteristic of the genus. This comprises four, more or less, well-defined zones. The style expands gradually into the usually, narrowly obovoid, basal portion of the pollen presenter, which terminates abruptly in a narrow constriction. Above the constriction is a short bulge, and above that a tapering, usually longitudinally grooved and viscid, portion referred to here as the receptor. It is to the receptor that most of the pollen adheres in newly opened flowers. At the apex of the receptor is the rather dilated stigma. Four separate measurements of the pollen presenter were included in the descriptions below: the length of basal portion (from the point at which the style expands to the base of the constriction), the length of the receptor (from the top of the bulge to the stigma inclusive), the length of the pollen presenter in its entirety and the width at its widest point (which is either at the top of the basal portion or the bulge). The distribution maps were compiled using DIVA-GIS Version 5.2.0.2 and based on PERTH specimen data. Taxonomy Isopogon panduratus Hislop & Rye, sp. nov. Isopogon axillari affinis sed inflorescentiis grandioribus floribus numerosis, pollinis praebitoris longioribus, pilis tepalorum longioribus densioribus differt. hislop 591.indd 170 22/06/2010 9:39:25 AM M. Hislop & B.L.Rye, Two new, glaucous-leaved species of Isopogon 171 Typus: Garabaldi Willis Rd, [Tathra National Park], 1.6 km S of Eneabba–Carnamah Rd, [E of Eneabba], Western Australia, 16 July 2000, M. Hislop 2041 (holo: PERTH 05815266 (sheet 1), PERTH 05815274 (sheet 2); iso: CANB, MEL). Robust, spreading shrubs to c. 2.0 m high and 1.5 m wide, with a fire-sensitive rootstock. Young branchlets distinctly ribbed to almost smooth, pale brown to reddish-brown, the older wood grey, with a sparse to moderately dense indumentum of soft, variously orientated, straight or ± curled, tubercle-based hairs often of mixed lengths, the longest to c. 1.2 mm long. Leaves simple, entire, usually glaucous at least when fresh, variously orientated between patent and steeply antrorse; apex mucronate; lamina narrowly obovate in the upper 2/3–3/4 of its length, above a long attenuate, petiole-like portion which gradually expands again towards the base, 35–125(–150) mm long, 3–19 mm wide, ± flat to shallowly or deeply concave adaxially, straight to prominently incurved along the longitudinal axis, thick, with indistinct venation, apart sometimes from the midrib, ± hairy when young with a similar tubercle-based indumentum to that of the branchlets, but soon glabrescent, leaving the surfaces finely tuberculate. Inflorescence globose or depressed-globose, 18–30 mm diam., (30–)40–70(–105)-flowered, terminal or axillary, sessile, subtended by, and the basal portion partially obscured by, the expanded leaf bases, solitary or several grouped together in clusters. Involucral bracts in 3–5 whorls; the outer bracts broadly ovate, ovate or obovate, 6.8–12.5 mm long, 3.3–6.7 mm wide, abaxial surface appressed-hairy throughout or at least in upper half, whitish if densely hairy but otherwise often purple-tinted, the colour fading to brown in old dried specimens, adaxial surface with a zone of appressed hairs towards the apex, otherwise glabrous, apex mucronate or obtuse, margins ciliate; the inner bracts narrowly obovate or narrowly panduriform, 9.1–13.5 mm long, 1.3–2.3 mm wide, abaxial surface densely appressed-hairy in upper 1/2–2/3, either glabrous below or with a few coarse crinkled hairs, adaxial surface with a zone of appressed hairs towards the apex, glabrous below, apex acute, margins ciliate, usually throughout, but sometimes only in the upper half. Cone scales very narrowly panduriform, usually wider towards the apex, 9.4–13.9 mm long, 0.7–1.3 mm wide, abaxial surface with a strongly dimorphic indumentum, densely appressed-hairy on the expanded upper portion, much less hairy to ± glabrous on the narrower, central portion, with a zone of coarser, more spreading, crinkled hairs towards the base, adaxial surface densely appressed-hairy on the upper portion, ± glabrous, or with just a few hairs below, apex acute, margins usually ciliate throughout with straight, fine hairs above and crinkled, coarse ones below. Perianth tube slightly expanded about the ovary, otherwise filiform, glabrous, pale pink, 18–27 mm long; lobes pale pink, 4.4–6.1 mm long, the limb slightly darker, 2.3–3.1 mm long, with a tuft of straight, white hairs at the apex, 0.5–1.1 mm long, from which a row of marginal hairs usually extend to a point at least a third the way down the limb.