Maesa prolatifructa Sumanon & Utteridge, 2021

Sumanon, Pirada, Eiserhardt, Wolf L., Balslev, Henrik & Utteridge, Timothy M. A., 2021, Six new species of Maesa (Primulaceae) from Papua New Guinea, Phytotaxa 505 (3), pp. 245-261 : 256-259

publication ID

http://doi.org/ 10.11646/phytotaxa.505.3.1

persistent identifier

http://treatment.plazi.org/id/03EF8799-2920-FFBB-20FF-E1EF97B190DD

treatment provided by

Marcus

scientific name

Maesa prolatifructa Sumanon & Utteridge
status

sp. nov.

Maesa prolatifructa Sumanon & Utteridge   , sp. nov. ( Fig. 6 View FIGURE 6 )

Recognised in the genus Maesa   by the combination of the following characters: comparatively long petioles up to 4 cm long, lanceolate leaves with a coriaceous lamina, and the leaves drying olive-green with a reddish brown abaxial midrib.

Type:— PAPUA NEW GUINEA. East New Britain District: Pomio Subdistrict, lower slopes of Mt Lululua , 5°43’S, 151°2’E, elev. 1250 m, 6 May 1973 (fr.), P. F GoogleMaps   . Stevens & Y   . Lelean LAE 58298 View Materials (holotype K!; isotypes BISH!, CANB!, L image!, M!)   .

Tree or shrub to 18 m. Indumentum: all parts lacking hairs, scaly on lamina surfaces; scales peltate, up to 0.9 mm in diameter, reddish brown or ginger brown with a central dark spot, ± sessile, circular. Branches drying dark reddish brown with scattered lenticels, glabrous. Leaves: lamina lanceolate, 7.3–11.7 cm long, 2.4–4.2 cm wide, coriaceous, adaxial surface glabrous, abaxial surface scaly, base attenuate or cuneate, margins entire and distinctly marginate on drying (i.e. with the marginal tissue raised and distinct), apex acute; midrib glabrous, distinctly raised abaxially, drying olive-green adaxially and reddish brown abaxially, secondary veins 5–8 pairs, craspedodromous; petiole 1.8–4.0 cm long, glabrous. Staminate inflorescences and flowers not seen. Pistillate inflorescences lateral (axillary), racemes, solitary or fasciculate with up to 3 inflorescences per axil, 2–3 cm long at anthesis, 3–7 cm long in fruit, axis densely scaly; pedicels 1.2–1.7 mm long, densely scaly distally; bracts triangular, 1.2–1.5 mm long, scaly, margins entire to ciliate, apex acute; bracteoles ±opposite, inserted at the base of the hypanthium, shape as bracts, 0.9–1.2 mm long, 0.75–0.90 mm wide. Pistillate flowers pentamerous; calyx lobes ovate, 0.75 mm long, 0.75–0.85 mm wide, glabrous, margins entire, apex acute; corolla not seen; hypanthium 1.5–2 mm long, scaly to sparsely scaly; style not seen. Fruits ellipsoid, prolate at the poles, reddish brown, 6.0–10.0 mm long, 4.0– 5.7 mm diameter, scaly; pedicels in fruit 3.0–6.0 mm long; bracteoles remaining ±opposite each other at the base of the fruit; calyx lobes overlapping, persistent.

Distribution and ecology:— The species is found at an elevation of 1250–1500 m in montane forests of New Ireland and New Britain in Papua New Guinea.

Etymology:— The specific epithet refers to the prolate, ellipsoid fruit of this new species, a feature found in this taxon and in M. sayersii Sleumer.  

Additional material examined:— PAPUA NEW GUINEA. East New Britain District: Pomio Subdistrict, Mt Sule , about 25 miles NNE of Fulleborn Harbour, 5°50’S, 150°50’E, elev. 1500 m, 7 May 1973 (fr.), J. R. Croft & P. Katik NGF 41940 View Materials (distributed partly as 14940) ( BISH!, CANB!, E!, K!, L image!) GoogleMaps   ; New Ireland Province: Namatanai Sub-province, Hans Meyer Range, on steep ridge near camp, c. 8 km W. N. W. of Taron on east coast, 4°24’S, 152°58’E, elev. 1350 m, 23 October 1975 (fl. & fr.), M. J. S. Sands 2329 ( K!, L image!) GoogleMaps   .

Notes:— Maesa prolatifructa   is unique in the genus in having lanceolate leaves with a reddish-brown raised midrib on the abaxial side. It is unlikely to be confused with any other species in New Guinea and can be easily distinguished from its most similar species, M. sayersii   , by leaf characters, viz: coriaceous texture (chartaceous to sub-coriaceous in M. sayersii   ), shape (lanceolate vs elliptic in M. sayersii   ), length and width ratio (2.1–4.3 vs 1.7–3.2 in M. sayersii   ), size (7.3–11.7 cm long by 2.4–4.2 cm wide vs 11.5–28.8 cm long by 4.0– 15.5 cm wide in M. sayersii   , Fig. 7 View FIGURE 7 ), and venation (5–8 secondary vein pairs per leaf vs 6–10 in M. sayersii   ). The distribution of M. prolatifructa   , as currently known, is limited to East New Britain and New Ireland Provinces of Papua New Guinea, while M. sayersii   is distributed in West New Britain, New Hanover, New Ireland and Manus Island. Maesa prolatifructa   is also found at higher elevations around 1250–1500 m, while M. sayersii   is at lower elevations around 30– 900 m.

Several previous studies have pointed out the effect of elevation gradients on morphological and anatomical variation within species. Most studies showed a decrease in leaf size and an increase in leaf thickness of plants growing at high elevations as a modification to the environment (e.g., Scheepens et al. 2010, Bresson et al. 2011), posing the question: is this new species an altitudinal variant of M. sayersii? To   test this, a correlation test was performed to see if there is any correlation between elevation and leaf length or leaf width. Although the sample size was small, there is no significant correlation between elevation and leaf size in both species, and mean length and width of both species are significantly different ( Fig. 7 View FIGURE 7 and Table 1); this evidence further supports recognition of M.prolatifructa   as a distinct species. Further studies using population genetic methods could clarify and confirm the taxonomic status of these two species.

P

Museum National d' Histoire Naturelle, Paris (MNHN) - Vascular Plants

F

Field Museum of Natural History, Botany Department

Y

Yale University

LAE

Papua New Guinea Forest Research Institute

K

Royal Botanic Gardens

BISH

Bishop Museum, Botany Division

CANB

Australian National Botanic Gardens

L

Nationaal Herbarium Nederland, Leiden University branch

M

Botanische Staatssammlung München

J

University of the Witwatersrand

R

Departamento de Geologia, Universidad de Chile

E

Royal Botanic Garden Edinburgh

W

Naturhistorisches Museum Wien

N

Nanjing University

S

Department of Botany, Swedish Museum of Natural History