Pterolepis glomerata
(false meadowbeauty)

Preferred Scientific Name

• Pterolepis glomerata (Rottb.) Miq.

Preferred Common Name

• false meadowbeauty

Other Scientific Names

• Arthrostemma angusturense (Rich.) Naudin
• Arthrostemma angusturense DC.
• Arthrostemma brachyandrum Cham.
• Arthrostemma capitatum (Rich.) Naudin
• Arthrostemma glomeratum (Rottb.) Cham.
• Arthrostemma salzmannii Naudin
• Chaetogastra callichaeta Benth.
• Chaetogastra glomerata (Rottb.) Benth.
• Chaetogastra sherardioides DC.
• Osbeckia glomerata (Rottb.) DC.
• Osbeckia glomerata var. albiflora DC.
• Osbeckia maritima A. St.-Hil.
• Osbeckia sipaneoides DC.
• Pterolepis capitata (Rich.) Miq.
• Pterolepis hostmannii Steud.
• Pterolepis maritima (A. St.-Hil.) Cogn.
• Pterolepis paludosa Cogn.
• Pterolepis salzmanii (Naudin) Cogn.
• Pterolepis sipaneoides (DC.) Cogn.
• Rhexia angusturensis Rich.
• Rhexia capitata Rich.
• Rhexia glomerata Rottb.

Local Common Names

• Caribbean: balier blan; balye blam; herbe sure

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Myrtales
•                         Family: Melastomataceae
•                             Genus: Pterolepis
•                                 Species: Pterolepis glomerata

Pterolepis belongs to the Melastomeae, a large pantropical tribe. Melastomataceae comprise approximately 4,500 species and 150 genera from tropical and subtropical areas (Renner, 1993).

There have been some taxonomic revisions in the past for P. glomerata. P. glomerata was first collected between June 1755 and January 1756 by D. Rolander in Surinam. He described P. glomerata as new species of Rhexia. A. P. de Candolle (1828a,b) assigned new species for Pterolepis so as to reflect natural affinities, placing P. glomerata in Osbeckia L. De Candolle named this new section of Osbeckia ‘Pterolepis’ (Greek: with winged scales). Nowadays, Osbeckia is considered to be restricted to the paleotropics, while Pterolepis occurs in the neotropics.

Chamisso (1835) placed the 5-merous species of Pterolepis in Chaetogastra, while the 4-merous ones preferably should go in Arthrostemma. A dwarf form of P. glomerata thus was described as A. brachyandrum Cham. Bentham (1840), by contrast, disregarded floral mery and put P. glomerata (4-merous) into Chaetogastra. At the same time, Miquel (1840) decided that de Candolle’s section Pterolepis deserved generic rank in spite of the heterogeneity in habit and flower mery of the genus. Though he was only concerned with the Surinamese species, among them P. glomerata (Renner, 1994).

Macromorphologically Pterolepis closely resembles species in the African and Asian genera Antherotoma, Dissotis, Melastoma, and Osbeckia. The widespread species Osbeckia chinensis L.and O. cochinchinensis Cogn. for example, appear to be counterparts to P. glomerata, morphologically as well as ecologically (Renner, 1994).

Saint-Hilaire, one of the early collectors of Pterolepis in Brazil, described a littoral form of P. glomerata as Osbeckia maritima (Renner, 1994).

There are ten named varieties of P. glomerata, indicating significant variation. These are: angustifolia, angusturensis, brachyandra, glaziovii, longifolia, martiana, microphylla, peruviana, saldanhaei and sherarioides (The Plant List, 2013).

The following is adapted from Renner (1994), Gordon (1998), Broome et al. (2007) and PIER (2015):

Profusely branched, erect, suffrutescent herb or subshrub up to 0.5 m tall. Stem and distal branchlets obscurely quadrangular, moderately strigose.

Leaves are regularly distributed along the stem, spreading, often with a second, precocious pair in the axils of the first. Leaves are ovate to oblong-ovate or elliptic, 1.4-4.5 cm long, 0.6-1.6 cm wide, 3-nerved, both surfaces sparsely to moderately strigose, margins entire or obscurely serrulate, apex acute, base obtuse to rounded, petioles 1-5 mm long.

Flowers can be pink, purple or white. Plants from the Guianas and eastern Venezuela frequently have white petals. Usually 3-5 flowers up to 10 inch bracteate, terminal glomerules, bracts and bracteoles ovate to lanceolate, 3.5-6 mm long, 1-2.5 mm wide at base, persistent, cilate; hypanthium covered with simple and stalked-stellate or branched hairs; calyx lobes triangular or oblong-ovate, 4-7.5 mm long, ca. 2 mm wide at base, ciliolate; petals obovate, ± obliquely truncate, 10-15 mm long, 10-14 mm wide; larger anthers pink, 3-4 mm long, connective prolonged 0.25-0.5 mm, with a 2-lobed appendage ca. 0.5 mm long, smaller anthers yellow, 2.5-3.5 mm long, with connective and appendage somewhat shorter but otherwise as in larger anthers.

Fruiting hypanthium is 4-6 mm long, 2-5 mm wide. Seeds are ca. 0.5 mm long and width is ca. 0.35 mm, weight of seed is 19 μmg.

Soil drainage

• impeded
• seasonally waterlogged

Soil reaction

• acid
• very acid

Special soil tolerances

• infertile
• other

Natural Dispersal

Propagules are dispersed by water (PIER, 2015). According to Gerrish (1978) the seeds have a great dispersability.

Vector Transmission (Biotic)

Propagules are dispersed by birds. Propagules are also likely to be dispersed unintentionally, because plants grows in heavily trafficked areas (PIER, 2015). Occasionally seeds can also be spread in mud on birds' feet (Renner, 1994).

Impact on Habitats

P. glomerata is known as an environmental weed in Hawaii, USA (PIER, 2015). If no measures are taken against invasive species like P. glomerata, then these species will alter and eventually destroy the natural composition of the ecosystems in Hawaii and will seriously limit the functionality of the watershed (Wood, 2000).

Impact on Biodiversity

Viola kauaensis var. wahiawaensis is known only from the Wahiawa Mountains of Kauai Island, Hawaii. This species is not known to have occurred beyond its current range. Fewer than 100 individuals are known to remain in Kanaele Swamp (often referred to as Wahiawa Bog), an open bog surrounded by low shrubs at an altitude of 640 m. P. glomerata competes with V. kauaensis var. wahiawaensis and is a current threat to this species (US Fish and Wildlife Service, 1998). V. kauaensis var. wahiawaensis is listed as Endangered under the US Endangered Species Act (ESA).

Also Viola helenae is only growing in the Wahiawa Mountains of Kauai Island. Its habitat is also affected by P. glomerata and the species is also listed as endangered under the US ESA (U.S. Fish and Wildlife Service, 2006).

Other species that are affected by P. glomerata and listed as endangered under the US Endangered Species Act are Pteris lidgatei and Sanicula purpurea on Oahu Island, Hawaii (US Fish and Wildlife Service, 2007; 2009).

• Proved invasive outside its native range
• Fast growing
• Has high reproductive potential
• Reproduces asexually

• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Competition - monopolizing resources
• Rapid growth