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A new species of sundew (Drosera, Droseraceae) with water-dispersed seed, from the floodplains of the northern Amazon Basin, Brazil.

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13
INTRODUCTION
The c. 200 species of sundews (Drosera, Droseraceae)
are distributed worldwide, occurring mostly in open
boggy or wet sandy habitats. In tropical and subtrop-
ical climates, Drosera species are especially abundant
in highlands where open habitats with low vegetation
are more common. In Brazil, the few Drosera species
that occur in lowlands are mostly found in sandy
coastal habitats known as restingas and only a few of
them occur in inland lowland habitats, including D.
capillaris Poir. in northern Brazil (the authors regard
D. biflora Willd. ex Roem. & Schult. as conspecific
with D. capillaris), D. cayennensis Sagot ex Diels in
western and northern Brazil, and D. sessilifolia A.
St.-Hil. which is abundant in central, western, north-
eastern, and the northernmost tip of Brazil (F. Riva-
davia, pers. obs.).
In late 1998, herbarium specimens of an uniden-
tified Drosera species were found and studied at the
Instituto Nacional de Pesquisas da Amazônia in
Manaus (INPA). In the attempts to determine the
exact location of origin of these specimens collected
between 1961 and 1992, the area was revisited in
late 2006 (F. Rivadavia) and two sites were found
around 500 m apart. An additional new collection
of this species was made in late 2006 in the State of
Roraima and studied at INPA in 2008 (A. Vicentini).
Based on studies carried out in the field and with
herbarium specimens, this new species of Drosera is
described below.
SPECIES DESCRIPTION
Drosera amazonica Rivadavia, A. Fleischm. & Vicent.
sp. nov.
Affin. Drosera felix Steyerm. & L.B. Sm. et similis
D. roraimae (Klotzsch ex Diels) Maguire & J. R.
Laundon sed scapis defectis, floribus solitariis brevipe-
dicellatis et semina ovoideo-globosa foveata differt.
Typus: Brazil, Amazonas, Rio Cuieiras, igarapé da
Cachoeira, 15 Nov. 1964, Rodrigues 6042 (Holoty-
pus, INPA).
ECOTROPICA 15: 13–21, 2009
© Society for Tropical Ecology
A NEW SPECIES OF SUNDEW (drosera, DROSERACEAE),
WITH WATER-DISPERSED SEED, FROM THE FLOODPLAINS OF
THE NORTHERN AMAZON BASIN, BRAZIL
Fernando Rivadavia1, Alberto Vicentini2 & Andreas Fleischmann3*
1Daniel Burnham Ct., San Francisco, 94109, USA
2Center for Tropical Forest Science, Smithsonian Tropical Research Institute, Apdo 0843-03092, Panama,
Panama
3LMU Munich, Systematic Botany, Menzinger Strasse 67, D-80638 Munich, Germany
Abstract. Drosera amazonica Rivadavia, A. Fleischm. & Vicent. (Droseraceae) is described from the northern Amazon
Basin in northeastern Amazonas State and central Roraima State, Brazil. The morphological characteristics which distinguish
this new species are discussed, together with its distribution and ecology. Hydrochory is assumed for this new species,
which would be the first record in the genus Drosera.
Key words: Brazil, Amazon, new species, sundews, Droseraceae, Drosera, hydrochory, flower scent.
Resumo. Drosera amazonica Rivadavia, A. Fleischm. & Vicent. (Droseraceae) é descrita da bacia norte do Rio Amazonas
do nordeste do estado do Amazonas e do centro do estado de Roraima, Brasil. As características morfológicas que distinguem
esta espécie nova são discutidas, junto com sua distribuição e ecologia. Presume-se que esta espécie nova possui hidrocoria,
sendo este o primeiro registro para o gênero Drosera. Accepted 26 March 2009.
Palavras chaves: Brasil, Amazonas, espécie nova, Droseraceae, Drosera, hidrocoria, odor da flor.
* e-mail: fleischmann@lrz.uni-muenchen.de
14
RIVADAVIA ET AL.
FIG. 1. Drosera amazonica. A. Habit of plant. B. Above view of ovary with style-arms and one anther. C.
Leaf lower surface, stipule bent backwards. D. Leaf upper surface. E. detached sepal. F. detached petal. G.
Seed. A drawn from photographs, B–G from dried material (Rivadavia & Azevedo 2460, 2461 (SPF)).
Drawings by Andreas Fleischmann.
15
Water-diSperSed SundeW
Stem-forming perennial. Stems short, up to 10 cm
long, unbranched, covered by dried leaves. Inter-
nodes barely visible in smaller specimens and up to
0.5–1 mm in larger specimens. Leaves rosulate, gla-
brous, only in young developing leaves lower surface
sparsely covered by sessile translucent glands or by
short, appressed white or red hairs of c. 0.5 mm
length; stipules papery, lacerate, divided to the base
into 5 fimbriate segments, segments c. 0.1 mm wide
at the base, outer segments slightly longer, c. 1.5–2
mm long, the 3 inner segments c. 1 mm long; pe tiole
plane, 5–10 mm long, 1–2 mm wide, slightly broader
at the base and tapering gradually to the apex,
glabrous, margins minutely reflexed; lamina spatu late
to obovate, 2.5–5 mm long, 1–3 mm wide. Flowers
solitary, depauperated, almost sessile or short pedun-
culate, bracteate; peduncle, bract, pedicel, and sepals
covered by short, appressed, white or red hairs c. 0.5
mm long; pedicel and lower part of sepals additio-
nally covered by yellowish translucent short stalked
glands; peduncle short, upright at anthesis but bent
down in fruit, 1–3.5 mm long, c. 0.5 mm thick; bract
subulate or filiform, with acute apex, 1–2 mm long,
0.1–0.5 mm wide; pedicel 0.5–1 mm long, c. 0.5
mm thick; sepals 5, subulate, acute, 2.5–4 mm long,
up to 1 mm wide in the middle of their length; calyx
campanulate at anthesis but sepals spreading in fruit;
petals 5, oblong with apex acute to rotundate, 5–6
mm long, c. 0.5 mm wide at the base and at the tip,
1.5–2 mm wide at broadest, white; styles 3, dissected
to the base, style arms 2 mm long; ovary subglobose,
c. 1 mm in diameter; stamens 5, anthers white, fila-
ments 2–2.5 mm long, 0.1 mm wide, pollen yellow.
Peduncle bent downwards in fruit and covered by
subsequent leaves, capsule subglobose, c. 2 mm in
diameter, loculicidal. Seed ovoid to subglobose,
0.2–0.5 mm long, 0.2–0.3 mm wide, black, foveate
(Figure 1).
Distribution. Drosera amazonica is known from a few
collections along the Igarapé Cachoeira, a small
tributary of the Cuieiras River, which empties into
the Rio Negro around 100 km upriver from Manaus,
northeastern Amazonas State. When visiting this site
in 2006, one of us (F. Rivadavia) found two extensive
populations c. 500 m apart on opposite sides of the
small river. These populations are located in the
Parque Estadual do Rio Negro Setor Sul, a protected
area relatively safe from deforestation.
Another population was discovered c. 450 km
north of this area in the Viruá National Park in the
central part of Roraima State, where it is sympatric
with D. capillaris (Vicentini 1477 at INPA). Thus,
according to these known populations, D. amazo nica
distribution may be limited by the Amazon River in
the south and the Rio Negro in the west. This species
is apparently not found on the western margins of
the Rio Negro in nearby locations such as the Jaú
National Park where D. capillaris has been collected
(Vicentini 1371 at INPA). The Rio Branco might
also be the limit of its distribution to the north and
the west, although the extensive white-sand flooded
savanas on both sides of this river, partially included
in the Viruá National Park, are potentially a core area
for D. amazonica (Figure 2).
Etymology. The epithet “amazonica” refers to the
biogeographic region this species is endemic to: the
northern Amazon Basin in Amazonas and Roraima
States of Brazil.
Taxonomic affinities. Drosera amazonica belongs to
Drosera subgenus Drosera sect. Drosera (sensu Seine
& Barthlott 1994). Its closest relative seems to be D.
felix Steyerm. & L.B. Sm., a species with which it
shares generative characters, such as a few- or single-
flowered inflorescence on a short scape, a calyx
covered with non-glandular hairs, a sweet flower
fragrance, and ovoid to subglobose seeds. However,
Drosera felix differs from D. amazonica in having flat
leafy rosettes, a suborbicular lamina, petioles that are
transversely elliptic in cross section, up to 3 flowers
per scape, and seed capsules that open cup-like.
Sterile plants of D. amazonica are reminescent of
D. roraimae (Klotzsch ex Diels) Maguire & Laundon
or even large specimens of D. communis A. St.-Hil.,
as both these species are stem-forming perennials
with a broadly linear plane petiole and a spatulate to
obovate lamina. However, flowering specimens of D.
roraimae and D. communis can easily be distinguished
from D. amazonica in having ascending multi- flow-
ered racemose inflorescences on well-developed sca-
pes up to 30 cm long. Drosera amazonica is unlikely
to be confused with D. meristocaulis Maguire &
Wurdack, a species native to the plateaus on the
Neblina Massif of the Brazil-Venezuela border. Al-
though D. meristocaulis also forms compact rosettes
with similarly shaped leaves and has single flowers on
nearly sessile scapes, it has pink petals that are broadly
oblanceolate, much larger stipules and stems, and is
unique among New World Drosera species in having
3 undivided styles.
16
RIVADAVIA ET AL.
Material examined. BRAZIL. Amazonas: Manaus,
Rio Cuieiras, Igarapé Cachoeira, 19 Dec 1961, Ro-
drigues & Wilson 3996 (INPA); Novo Airão, Igarapé
Cachoeira, Rio Cuieiras 16 Dec 2006, Rivadavia &
Azevedo 2458, 2460, 2461 (SPF); Rio Cuieiras,
Igarapé da Cachoeira, 15 Nov 1964, Rodrigues 6042
(holotype, INPA); Rio Negro, Rio Cuieiras, Igarapé
da Cachoeira, 22 Jun 1992, Mori & Gracie 22444
(INPA, NY). Roraima: Caracaraí, Parque Nacional
do Viruá, 5 Dec 2006, Carvalho & Nascimento 1129
(INPA).
ECOLOGICAL NOTES
Drosera amazonica, like other Drosera species in the
Amazonian area, is found on white quartz sand sa-
vannas that are seasonally flooded or that become
flooded during heavy rains. The soil is highly acidic
and extremely poor in nutrients, consisting either of
deep sand sediment or shallow soils associated with
sandstone outcrops. This type of vegetation is part of
an ecological gradient defined by these soil charac-
teristics and different flooding regimes, which deter-
mine vegetation structure. Forests, scrublands, and
FIG. 2. Map showing the two known locations where D. amazonica occurs.
17
Water-diSperSed SundeW
savannas occur along this gradient and correspond
to the vegetation types known in the lowlands of
Brazilian Amazon as campina, igapó, chavascal, and
campinarana. These ecological conditions are found
both in the lowlands and the highlands of the Guay-
ana Shield, and these areas share many genera of
plants that have adapted to and diversified in these
conditions. The patchy, island-like distribution of
these vegetation types (particularly the savannas)
creates heterogeneity in species composition on a
local scale, with the relative abundance of species
varying greatly between neighboring sites (A. Vicen-
tini, pers. obs.), and with many species that are en-
demic to certain regions (Vicentini 2004, and re-
ferences therein; Oliveira et al. 2001).
The areas inhabited by Drosera amazonica are
usually open and dominated by grasses and/or sedges
with scattered trees and shrubs that sometimes form
small “islands” within the open grassland. Herba-
ceous plants common in these areas are members of
the genera Alboboda (Xyridaceae), Syngonanthus
(Eriocaulaceae), Utricularia (Lentibulariaceae), Epi-
stephium and Duckeella (Orchidaceae), Panicum
(Poaceae), Lagenocarpus (Cyperaceae), Cephalostemon
(Rapateaceae), Lycopodiella (Lycopodiaceae), and
Schizaea (Schizaeaceae). Shrubs and trees frequently
found in these areas belong to the genera Humiria
(Humiriaceae), Platycarpum, Pagamea and Retinhi-
phyllum (Rubiaceae), Cyrilla (Cyrillaceae), Pachyloma
and Macairea (Melastomataceae), Gongylolepis (Aste-
ra ceae), Ternstroemia (Ternstroemiaceae), Ilex (Aqui-
foliaceae), and Rhodognaphalopsis (Malvaceae), and a
few palms (Arecaceae) like Bactris campestris Poepp.
and Mauritiella aculeata (H.B. & K.) Burret. Most
members of these taxa are endemic to this type of
vegetation on oligotrophic soils (Vicentini 2004).
Drosera amazonica occurs in large populations,
the individuals often growing very close together
FIG. 3. Dense stand of Drosera amazonica in open sand vegetation at the Igarapé Cachoeira, Rio Cuieiras,
northeastern Amazonas. Accompanying plants are Lycopodiella sp. and species of Cyperaceae.
18
RIVADAVIA ET AL.
(Figures 3 & 4). It has been collected in flower in the
months of January, December, and June, suggesting
that this species does not have a specific flowering
period.
The flowers of D. amazonica (Figure 5) are
sweetly perfumed, a character this species shares with
at least four more New World species of Drosera: D.
arenicola Steyerm., D. felix, D. kaieteurensis Brumm.-
Ding., and D. solaris A. Fleischm., Wistuba & S.
McPherson, all of which are highland species from
the Guayana Shield north of the Amazon. These
species have in common a rather short and stiff flower
scape, and flowers of D. amazonica, D. solaris, D. felix
(frequently) and D. arenicola (occasionally) are borne
solitary on very short peduncles and pedicels, so that
they are nested almost sessile within the rosette of the
plant. Flower odor may have evolved among these
species in order to attract pollinators to the nearly
sessile flowers, thus keeping them away from the
surrounding visually attractive sticky carnivorous
leaves. The white flowers of D. amazonica, D. areni-
cola, D. felix, D. kaieteurensis, and D. solaris close
early in the afternoon, therefore olfactory-oriented
nocturnal pollinators can be excluded.
As is common for all species of Drosera sect.
Drosera, each flower of D. amazonica only opens for
one day, usually only in the morning, after which the
corolla and calyx lobes close. After anthesis, the pe-
dicels of D. amazonica bend downwards and the
scape is additionally pressed further down by conse-
cutively produced leaves, so that the ripe seed cap sule
is eventually on its side or facing downwards (Figure
6). The seed is therefore shed on the soil underneath
the mother plant, and as the flowers are almost sessile
the seed grains are likely to be deposited very close
to the stem of the same fruiting plant.
FIG. 4. Habit of Drosera
amazonica at Igarapé Ca-
choeira. The tall stems and
long internodes may re-
present an adaptation to
occasional flooding. The
small green subulate leaves
on the ground around the
Drosera belong to the car-
nivorous plant Utricularia
subulata L. (Lentibularia-
ceae).
19
Water-diSperSed SundeW
However, the foveate seed surface (Figure 7) may
represent a specialized strategy to help disperse the
seed a greater distance. Our ontogenetic studies re-
veal that the pitted testa sculpture of D. amazonica
develops from papilliate testa outgrowths that col-
lapse when the seed matures. In water, air bubbles
are captured in the pits of the testa by capillary effects
(Figure 8), giving additional buoyancy to the seed
grains so that these are able to float and thus can be
carried for a certain distance by flowing water. Thus
the seed of D. amazonica is probably water-dispersed
either by flowing ground water of the open seepage
habitats or by the heavy tropical rainfalls common to
that area (hydrochory: nautochory). If true, this
dispersal mechanism would be unique among New
World Drosera.
Interestingly, Selenicereus wittii (Schum.) R.D.
Rowley, an epiphytic cactus endemic to the Rio
Negro of Amazonian Brazil, which grows in the same
area as D. amazonica, also has a water-dispersed seed,
a feature unique in Cactaceae (Barthlott et al. 1997).
FIG. 5. Flower of Drosera amazonica at the Viruá National Park, Roraima. (Photograph by Fernanda Antunes
Carvalho, used with permission).
FIG. 6. Fruiting capsule of Drosera amazonica. Note
the tip of the capsule pointing to the side, as the short
pedicel bends downwards after anthesis.
20
RIVADAVIA ET AL.
The remaining South American Drosera taxa with
short scapes also seem to rely heavily on water as a
vector for seed dispersal (whereas wind dispersal can
be assumed for the majority of other Drosera species).
Drosera felix, D. kaieteurensis, and D. solaris have
short, stiff and upright pedicels, in combination with
ovoid seeds, and cup-like seed capsules, which act as
“splash-cups” for seed dispersal by the impact of ra-
indrops (hydrochory: ombrochory). (Rivadavia 1999,
Fleischmann et al. 2007).
ACKNOWLEDGMENTS
We would like to thank Paulo Gonella, São Paulo,
for helping with measurements from herbarium
specimens; Fernanda Antunes Carvalho, Manaus, for
helping with information regarding the D. amazo nica
population in Roraima; and Dr. Eva Facher, Munich,
for assistance with SEM photography. Dr. John
Conran and an anonymous reviewer are thanked for
useful suggestions on the manuscript.
FIG. 7. The foveate seed of
Drosera amazonica (SEM).
FIG. 8. Seed of Drosera ama-
zonica buoyant on the water
surface by the aid of capillary
air bubbles adhering to the
pits of the testa.
21
Water-diSperSed SundeW
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diversidade na Amazônia. Fundação Vitória Amazônica
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... Corky or spongy tissue of low density Increases propagule buoyancy van der Pijl (1972) Waxy, cuticularized epidermis Prevents imbibition and sinking of propagules Sculthorpe (1967) Surface with furrows, pits or hairs Traps air bubbles, which increases the buoyancy of propagules Rivadavia et al. (2009) ...
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As florestas do Rio Negro
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Vegetação sobre solos arenosos. Pp. 179–219 in Oliveira, A.A., & D. Daly (eds.). As florestas do Rio Negro. Companhia das Letras, São Paulo.
Neblina expedition part 5. Listserve Archives of the Carnivorous Plant Discussion Group Mailing List
  • F Rivadavia
Rivadavia, F., 1999. Neblina expedition part 5. Listserve Archives of the Carnivorous Plant Discussion Group Mailing List; http://www.omnisterra.com/botany/cp/ list/cp99all.d/0609.htm