Taxon Details: Physeterostemon thomasii Amorim, Michelang. & Goldenb.
Taxon Profile:
 | The Plant List |
 | International Plant Name Index |
 | Tropicos |
 | Catalogue of Life |
 | Global Biodiversity Information Facility |
 | JSTOR Types |
| JSTOR |
 | BHL |
 | Encyclopedia of Life |
 | WikiSpecies |
 | Google Scholar |
 | PubMed |
 | Morphbank |
 | IUCN |
 | National Center for Biotechnology Information |
 | Barcode of Life |
Narratives:
Family:
Melastomataceae (Magnoliophyta)
Melastomataceae (Magnoliophyta)
Scientific Name:
Physeterostemon thomasii Amorim, Michelang. & Goldenb.
Physeterostemon thomasii Amorim, Michelang. & Goldenb.
Accepted Name:
This name is currently accepted.
This name is currently accepted.
Description:
Description Author and Date: André M. Amorim, Renato Goldenberg, and Fabián A. Michelangeli, based on A New Species of Physeterostemon (Melastomataceae) from Bahia, Brazil, with Notes on the Phylogeny of the Genus. Amorim, A.M., Goldenberg R., and Michelangeli F.A., Systematic Botany 34(2): 324-329. 2009.
Type: BRAZIL. Bahia: Mun. Tancredo Neves, estrada para Água Branca e Julião, ca. 14 km de Tancredo Neves, 13° 26' 36.3” S, 39° 30' 40.6” W, 11 Dec 2005 (fl, fr), A. M. Amorim ( with J. G. Jardim, L. C. J. Gomes & S. C. Sant’Ana ) 5470 (holotype: CEPEC!; isotypes: G!, NY!, RB!, UPCB!).
Description: Rhizomatous subshrub 15–25 cm tall. Young stems terete, densely strigose to hispidous, with two types of trichomes, some 1.5–2.5 mm long and ochraceous, others 3–4.5 mm long, paleaceous and canescent, the paleaceous trichomes denser at the nodal regions. Leaves opposite, slightly anisophyllous to isophyllous in each pair, petiole 0.5–6.3 cm long, the trichomes the same as on the branches, but with larger ones denser, leaf blade 6–23 × 4–11.5 cm, elliptic, ovate, elliptic-ovate to elliptic-lanceolate, base cordulate to cordate, seldom obtuse to rounded, apex shortly acuminate to acute, margins irregularly dentate to serrate, 5-plinerved (the inner pair joining the mdrib 2–8 mm above the base) with an inconspicuous additional submarginal pair, adaxially densely bullate-strigose, trichomes 1–2.8 mm long, main nerves dense hirtellous, abaxially strongly foveolate, moderately hispid, sometimes with larger, paleaceous trichomes on the base of the main nerves. Inflorescence terminal, sometimes with a pair of small leaves at its base, corymbose, with 5–20 flowers, 3.0–6.5 × 2.3–5.3 cm (larger measurements represent fruiting material), vinaceous, with trichomes similar to those on young stems; bracts 4.5–4.7 × 0.9–1.5 mm, narrowly triangular, apex subulate, glabrous, margin ciliate; bracteoles 2.2–4.3 × 0.5–1.4 mm, narrowly triangular, glabrous, margin ciliate. Flowers 6-merous, on true pedicels 2.3–3.1 mm long. Hypanthium 2.7–3.2 × ca. 2.9 mm, campanulate, outer surface densely hispid, trichomes 1–2.6 mm long, vinaceous, inner surface and the torus glabrous. Calyx persistent, abaxially hispid, adaxial surface glabrous; the tube 0.3–0.4 mm; inner lobes 1.8–2.5 mm, triangular, apex rounded, margin very sparsely short-ciliate; outer lobes 4.7–5.8 mm long, subulate, setose-tipped. Petals 6.8–7.2 × 5.5–5.8 mm, white, glabrous on both surfaces, obovate, apex truncate to emarginate, margin entire. Stamens 12, isomorphic, all grouped in a cluster at one side of the flower at anthesis; filaments 2–2.5 mm long; connective unappendaged, dorsally thickened; anthers 1.3–1.5 mm long, yellow, oblong and with a rounded apex in ventral view, slightly projecting backwards over the connective in lateral view, but with a single ventral pore, anthers ventro-basally with two short lobes below the filament insertion. Ovary half-inferior, the free portion ca. 2 mm long,4-locular, apex glabrous; ovules many, on large, globose, axial placentae; style curved, stigma punctiform. Capsules 3–3.3 × 3.5–4.3 mm, tearing longitudinally, with pericarp and adnate hypanthium persistent, placentae not seen in fruits. Seeds ca. 0.4 × 0.4 mm, cuneate, testa smooth.
Habitat and Distribution: Physeterostemon thomasii has been found only in a small fragment of Atlantic wet forest. The plants grow on clay soils and in shaded places, near a river bank. The fragment where these plants were found does not belong to any conservation unit, but it is near the Wenceslau Guimarães State Park. Since the plants werecollected in only one patch of unprotected forest, and since the forests in this region have been heavily destroyed and fragmented during the last years, this species can be considered endemic and highly endangered.
Etymology: The new species is named after Dr. Wm. Wayt Thomas, from the New York Botanical Garden, for his important work on the Southern Bahian flora.
Taxonomy and Systematics: The phylogenetic analysis of ndhF and rbcL sequence data is consistent with the hypothesis of Goldenberg and Amorim (2006) that Physeterostemon probably had a phylogenetic position near the Merianieae and the Miconieae. Physeterostemon shares with both tribes the stamens lacking pedoconectives, and cuneate to straight seeds. With Merianieae Physeterostemon shares the dry fruits with a thick and persistent placenta; it differs, however, in having 6-merous flowers with unappendaged anther connectives and superior ovaries. With Miconieae, Physeterostemon shares the toothed calyx, the short and straight, subisomorphic stamens with unappendaged or minutely ventro-bituberculate appendages, and an inferior ovary. The dry and dehiscent fruits characteristic of Physeterostemon are absent from this tribe, except for four genera (see below). Eriocnema Naudin is a small genus with two species endemic to a specific region in the state of Minas Gerais, growing in seasonal forests on granitic outcrops ( Andrade et al. 2007 ). It was traditionally assigned to Microlicieae, but recent analyses showed that it does not have any relation to this group, being instead sister to Miconieae ( Fritsch et al. 2004 ; Martin et al. 2008 ; Goldenberg et al. 2008 ). It shares with Physeterostemon the toothed calyx with long outer lobes, the subisomorphic, unappendaged stamens lacking pedoconnectives and the capsular fruit, but differs in its 4–5-merous flowers and superior ovaries ( Cogniaux 1891 ; Fritsch et al. 2004 ; Goldenberg and Amorim 2006 ). The seeds of Eriocnema seem to differ from all related groups on having a cuneateclavate shape, with a translucent structure resembling an air pocket ( Andrade et al. 2007 ), apparently on the end opposite the raphal region. It should be emphasized that both Eriocnema and Physeterostemon have capsular fruits, but differ in the position of the ovary. In the Melastomataceae there is a strong correlation between ovary position and fruit type. Most species with superior ovaries (free from the hypanthium wall) have dehiscent fruits, as in Eriocnema and in most Merianieae. Likewise, most species with partially or completely inferior ovaries have indehiscent and usually fleshy fruits ( Clausing et al. 2000 ), as in the Miconieae. Physeterostemon , with capsular fruits derived from inferior ovaries is a relatively rare case. Capsular fruits derived from at least partially inferior ovaries are found only in a few groups in the family; in three genera of Merianieae ( Merianthera Kuhlm., Tateanthus Gleason and some species of Tessmanianthus Markgraf) and three genera putatively placed in the Miconieae ( Allomaieta Glea son, Alloneuron Pilg., and Wurdastom B. Walln.; Renner 1993 ), which have also been placed in their own tribe, Cyphostyleae Gleason ( Gleason 1929 ; Lozano and Becerra- Lozano 1999 ). Altogether, these six genera represent fewer than 30 species. Information about the phylogenetic position of the last five genera is still lacking or somewhat unclear. Our understanding of the evolution of fleshy fruits in the large tribe Miconieae will certainly be improved by comparing its fruit morphology and development to that found in Eriocnema , Physeterostemon and the Cyphostyleae. The origins of Miconieae and its relations to Eriocnema + Physeterostemon and the Cyphostyleae pose an interesting question regarding biogeography: while the Miconieae are a large group found throughout tropical America, the sister group is endemic to the Atlantic Forest in Eastern Brazil, and the Cyphostyleae, whose phylogenetic position is still unknown, are from the Northern Andes. These two areas are actually some of the most Miconieae- (and Melastomataceae-) rich places in the Americas.
Description Author and Date: André M. Amorim, Renato Goldenberg, and Fabián A. Michelangeli, based on A New Species of Physeterostemon (Melastomataceae) from Bahia, Brazil, with Notes on the Phylogeny of the Genus. Amorim, A.M., Goldenberg R., and Michelangeli F.A., Systematic Botany 34(2): 324-329. 2009.
Type: BRAZIL. Bahia: Mun. Tancredo Neves, estrada para Água Branca e Julião, ca. 14 km de Tancredo Neves, 13° 26' 36.3” S, 39° 30' 40.6” W, 11 Dec 2005 (fl, fr), A. M. Amorim ( with J. G. Jardim, L. C. J. Gomes & S. C. Sant’Ana ) 5470 (holotype: CEPEC!; isotypes: G!, NY!, RB!, UPCB!).
Description: Rhizomatous subshrub 15–25 cm tall. Young stems terete, densely strigose to hispidous, with two types of trichomes, some 1.5–2.5 mm long and ochraceous, others 3–4.5 mm long, paleaceous and canescent, the paleaceous trichomes denser at the nodal regions. Leaves opposite, slightly anisophyllous to isophyllous in each pair, petiole 0.5–6.3 cm long, the trichomes the same as on the branches, but with larger ones denser, leaf blade 6–23 × 4–11.5 cm, elliptic, ovate, elliptic-ovate to elliptic-lanceolate, base cordulate to cordate, seldom obtuse to rounded, apex shortly acuminate to acute, margins irregularly dentate to serrate, 5-plinerved (the inner pair joining the mdrib 2–8 mm above the base) with an inconspicuous additional submarginal pair, adaxially densely bullate-strigose, trichomes 1–2.8 mm long, main nerves dense hirtellous, abaxially strongly foveolate, moderately hispid, sometimes with larger, paleaceous trichomes on the base of the main nerves. Inflorescence terminal, sometimes with a pair of small leaves at its base, corymbose, with 5–20 flowers, 3.0–6.5 × 2.3–5.3 cm (larger measurements represent fruiting material), vinaceous, with trichomes similar to those on young stems; bracts 4.5–4.7 × 0.9–1.5 mm, narrowly triangular, apex subulate, glabrous, margin ciliate; bracteoles 2.2–4.3 × 0.5–1.4 mm, narrowly triangular, glabrous, margin ciliate. Flowers 6-merous, on true pedicels 2.3–3.1 mm long. Hypanthium 2.7–3.2 × ca. 2.9 mm, campanulate, outer surface densely hispid, trichomes 1–2.6 mm long, vinaceous, inner surface and the torus glabrous. Calyx persistent, abaxially hispid, adaxial surface glabrous; the tube 0.3–0.4 mm; inner lobes 1.8–2.5 mm, triangular, apex rounded, margin very sparsely short-ciliate; outer lobes 4.7–5.8 mm long, subulate, setose-tipped. Petals 6.8–7.2 × 5.5–5.8 mm, white, glabrous on both surfaces, obovate, apex truncate to emarginate, margin entire. Stamens 12, isomorphic, all grouped in a cluster at one side of the flower at anthesis; filaments 2–2.5 mm long; connective unappendaged, dorsally thickened; anthers 1.3–1.5 mm long, yellow, oblong and with a rounded apex in ventral view, slightly projecting backwards over the connective in lateral view, but with a single ventral pore, anthers ventro-basally with two short lobes below the filament insertion. Ovary half-inferior, the free portion ca. 2 mm long,4-locular, apex glabrous; ovules many, on large, globose, axial placentae; style curved, stigma punctiform. Capsules 3–3.3 × 3.5–4.3 mm, tearing longitudinally, with pericarp and adnate hypanthium persistent, placentae not seen in fruits. Seeds ca. 0.4 × 0.4 mm, cuneate, testa smooth.
Habitat and Distribution: Physeterostemon thomasii has been found only in a small fragment of Atlantic wet forest. The plants grow on clay soils and in shaded places, near a river bank. The fragment where these plants were found does not belong to any conservation unit, but it is near the Wenceslau Guimarães State Park. Since the plants werecollected in only one patch of unprotected forest, and since the forests in this region have been heavily destroyed and fragmented during the last years, this species can be considered endemic and highly endangered.
Etymology: The new species is named after Dr. Wm. Wayt Thomas, from the New York Botanical Garden, for his important work on the Southern Bahian flora.
Taxonomy and Systematics: The phylogenetic analysis of ndhF and rbcL sequence data is consistent with the hypothesis of Goldenberg and Amorim (2006) that Physeterostemon probably had a phylogenetic position near the Merianieae and the Miconieae. Physeterostemon shares with both tribes the stamens lacking pedoconectives, and cuneate to straight seeds. With Merianieae Physeterostemon shares the dry fruits with a thick and persistent placenta; it differs, however, in having 6-merous flowers with unappendaged anther connectives and superior ovaries. With Miconieae, Physeterostemon shares the toothed calyx, the short and straight, subisomorphic stamens with unappendaged or minutely ventro-bituberculate appendages, and an inferior ovary. The dry and dehiscent fruits characteristic of Physeterostemon are absent from this tribe, except for four genera (see below). Eriocnema Naudin is a small genus with two species endemic to a specific region in the state of Minas Gerais, growing in seasonal forests on granitic outcrops ( Andrade et al. 2007 ). It was traditionally assigned to Microlicieae, but recent analyses showed that it does not have any relation to this group, being instead sister to Miconieae ( Fritsch et al. 2004 ; Martin et al. 2008 ; Goldenberg et al. 2008 ). It shares with Physeterostemon the toothed calyx with long outer lobes, the subisomorphic, unappendaged stamens lacking pedoconnectives and the capsular fruit, but differs in its 4–5-merous flowers and superior ovaries ( Cogniaux 1891 ; Fritsch et al. 2004 ; Goldenberg and Amorim 2006 ). The seeds of Eriocnema seem to differ from all related groups on having a cuneateclavate shape, with a translucent structure resembling an air pocket ( Andrade et al. 2007 ), apparently on the end opposite the raphal region. It should be emphasized that both Eriocnema and Physeterostemon have capsular fruits, but differ in the position of the ovary. In the Melastomataceae there is a strong correlation between ovary position and fruit type. Most species with superior ovaries (free from the hypanthium wall) have dehiscent fruits, as in Eriocnema and in most Merianieae. Likewise, most species with partially or completely inferior ovaries have indehiscent and usually fleshy fruits ( Clausing et al. 2000 ), as in the Miconieae. Physeterostemon , with capsular fruits derived from inferior ovaries is a relatively rare case. Capsular fruits derived from at least partially inferior ovaries are found only in a few groups in the family; in three genera of Merianieae ( Merianthera Kuhlm., Tateanthus Gleason and some species of Tessmanianthus Markgraf) and three genera putatively placed in the Miconieae ( Allomaieta Glea son, Alloneuron Pilg., and Wurdastom B. Walln.; Renner 1993 ), which have also been placed in their own tribe, Cyphostyleae Gleason ( Gleason 1929 ; Lozano and Becerra- Lozano 1999 ). Altogether, these six genera represent fewer than 30 species. Information about the phylogenetic position of the last five genera is still lacking or somewhat unclear. Our understanding of the evolution of fleshy fruits in the large tribe Miconieae will certainly be improved by comparing its fruit morphology and development to that found in Eriocnema , Physeterostemon and the Cyphostyleae. The origins of Miconieae and its relations to Eriocnema + Physeterostemon and the Cyphostyleae pose an interesting question regarding biogeography: while the Miconieae are a large group found throughout tropical America, the sister group is endemic to the Atlantic Forest in Eastern Brazil, and the Cyphostyleae, whose phylogenetic position is still unknown, are from the Northern Andes. These two areas are actually some of the most Miconieae- (and Melastomataceae-) rich places in the Americas.