Endemism in Neotropical Podostemaceae¹

Abstract

Descripción de la familia por A. Novelo R., C.T. Philbrick y G.E. Crow.Annual or perennial herbs, firmly attached to rocks and other solid substrata of waterfalls and rivers and streams with seasonally strong current. Roots linear, prostrate and flattened, green, branched or not. Stems arising along the flanks of roots, opposite or sub-opposite, disk-shaped (holdfast-like) or upright, attached firmly to the substratum. Leaves distichous or tristichous, clustered and rosette-like or projecting from an upright stem, petiolate or sessile; petioles terete to flattened, sometimes winged, mono-or dithecous; blades variable, simple, lobed, repeatedly pinnately or dichotomously compound or ensiform, when divided, the ultimate divisions hairlike or flattened, blunt or acute at the apex. Flowers solitary or fascicled, pedunculate or not, actinomorphic or zygomorphic, enclosed in bud by a sac-like spathella or a spathella lacking; tepals 3-9, scale-like, free or fused basally, linear or triangular; stamens 2-11, free or fused basally, in a complete whorl , or confined to one side of flower, the filaments elongating during anthesis, the anthers basifixed, dehiscing introrsely or latrorsely; pollen in monads or dyads; ovary 2-3-locular, superior, the placenta fleshy; stigmas 2-3, apically free or fused basally. Capsules 2-3-locular, 2-3-valved, longitudinally ribed, both valves persistent or one deciduous, the suture margins often thickened or not; seeds tiny, numerous, becoming sticky upon wetting. 47 gen., approx. 270 spp. Pantropical, a few species extending into temperate eastern Asia and eastern North America.Plants grow attached tightly to rocks or other solid substrata in strong currents of riverrapids and waterfall habitats. Flowering and seed production occurs when plants become exposed during seasonally low water levels.Bibliografía [matted]. Leaves scale-like, arranged in ramuli, generally tristichous, sessile, membranous, nerveless or 1-nerved. Flowers solitary, bisexual, enclosed by 2 bracts in bud; pedicellate; tepals 3, persistent, usually united at the base; stamens 1(2), the filaments slender, the anthers basifixed, dehiscing introrsely or latrorsely; pollen in monads; ovary 3-locular; stigmas 3, free, cylindrical; ovules numerous, the placenta axile. Capsules with 3 equal valves, persistent, each valve 3-ribbed, the suture margins not thickened and rib-like; seeds numerous, dust-like. Perennials. Roots 0.3-1.2 mm wide, prostrate, linear. Stems 1-11 cm, ascending to procumbent, branched or simple. Leaves 0.6-7 × 0.4-0.9 mm, 3-ranked (tristichous), scale-like, the apex acute to rounded. Pedicels 0.15-1.5 cm; lowest floral bract at pedicel base 1.1-2.8 mm, the adjacent upper bract 1-2.6 mm. Tepals 3-lobed, 1.3-2 mm, united at the base; stamens 1(2), the filaments 0.8-1.9 mm, the anthers 0.3-0.9 mm; stigmas 0.2-0.7 mm. Capsules 1-2 × 0.7-1. Tristicha trifaria is the most common member of the family in the Americas, and appears to be fairly tolerant of stream pollution. Its moss-like appearance, however, contri...

Systematics and Phylogeny of Neotropical Riverweeds (Podostemaceae: Podostemoideae)

“…transfer to another genus or recognition of a new genus) is deferred, pending the outcome of expanded phylogenetic analyses that include the remaining species of Marathrum from South America, along with broader taxonomic sampling from Apinagia and Jenmaniella . Royen 1951 ;Philbrick et al 2010 ), many of which were placed originally among three genera that no longer are recognized (i.e. Ligea Poit.…”

Historical biogeography of river-weeds (Podostemaceae)

“…The habitats are not restricted to any particular type of rock Cook and Rutishauser, 2007;Ameka et al, 2010). Some of the American species are reported to grow on igneous rocks, and the major distributional areas in Central and South America correspond roughly with areas of igneous and metamorphic rocks (Royen, 1951(Royen, , 1953(Royen, , 1954Cusset, 1972;Novelo and Philbrick, 1993;Novelo, 1994, 1995;Philbrick et al, 2009Philbrick et al, , 2010 Table S1). In Japan, five of six species occur exclusively in areas of welded tuff produced in pyroclastic flows in the Pleistocene, and one species occurs on granitic rocks on Yakushima (Supplementary Table S2 1989;Deckart et al, 1998;Segev, 2002 (Bell et al, 2010;Wikström et al, 2001).…”

A New Genus of Podostemaceae from Venezuela

“…Velásquez (1994) recognized eight genera and 22 species in the country. Philbrick et al (2010) listed the same genera, but somewhat more (28) species. Berry (2004) reported 26 species for the Venezuelan Guayana alone.…”

“…The species is categorized as Vulnerable (VUA1cB1), using the IUCN Red List criteria (IUCN, 2009). Factors that make species of Podostemaceae particularly vulnerable to human impacts are discussed in Philbrick et al (2010). Additional observations.…”