Macrophytes in the Upper Paraná River floodplain: checklist and comparison with other large South American wetlands

Abstract

Neotropical aquatic ecosystems have a rich aquatic flora. In this report, we have listed the aquatic flora of various habitats of the upper Paraná River floodplain by compiling data from literature and records of our own continuous collections conducted during the period 2007-2009. Our main purposes were to assess the macrophyte richness in the Paraná floodplain, to compare it with other South American wetlands and to assess whether the number of species recorded in South American inventories has already reached an asymptote. We recorded a total of 153 species of macrophytes in the Upper Paraná River floodplain, belonging to 100 genera and 47 families. In our comparative analysis, a clear floristic split from other South American wetlands was shown, except for the Pantanal, which is the closest wetland to the Paraná floodplain and, therefore, could be considered a floristic extension of the Pantanal. The species accumulation curve provides evidence that sampling efforts should be reinforced in order to compile a macrophyte flora census for South America. The high dissimilarity among South American wetlands, together with the lack of an asymptote in our species accumulation curve, indicates that the sampling effort needs to be increased to account for the actual species richness of macrophytes in this region.

Full text

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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 59 (2): 541-556, June 2011
Macrophytes in the upper Paraná river floodplain: checklist and
comparison with other large South American wetlands
Fernando Alves Ferreira1, Roger Paulo Mormul1, Sidinei Magela Thomaz2*, Arnildo Pott3
& Vali Joana Pott3
1. Postgraduate Program in Ecology of Continental Aquatic Environments, Universidade Estadual de Maringá- UEM,
Av. Colombo 5790, bloco H-90, CEP 87020-900, Maringá, Paraná, Brazil; ferreirabot@gmail.com,
roger.mormul@gmail.com
2. Research Group in Limnology, Ichthyology and Aquaculture-Nupelia, Biological Science Department, Universidade
Estadual de Maringá-UEM, Av. Colombo 5790, bloco H-90, CEP 87020-900, Maringá, Paraná, Brazil;
smthomaz@nupelia.uem.br
3. Biological Science Department, Universidade Federal do Mato Grosso do Sul - UFMS CEP 79.070-900, Caixa -
Postal 549, Campo Grande, MS, Brazil; arnildo.pott@gmail.com, vali.pott@gmail.com
* Corresponding author
Received 04-VI-2010. Corrected 30-XI-2010. Accepted 07-I-2011.
Abstract: Neotropical aquatic ecosystems have a rich aquatic flora. In this report, we have listed the aquatic
flora of various habitats of the upper Paraná River floodplain by compiling data from literature and records of
our own continuous collections conducted during the period 2007-2009. Our main purposes were to assess the
macrophyte richness in the Paraná floodplain, to compare it with other South American wetlands and to assess
whether the number of species recorded in South American inventories has already reached an asymptote. We
recorded a total of 153 species of macrophytes in the Upper Paraná River floodplain, belonging to 100 genera
and 47 families. In our comparative analysis, a clear floristic split from other South American wetlands was
shown, except for the Pantanal, which is the closest wetland to the Paraná floodplain and, therefore, could be
considered a floristic extension of the Pantanal. The species accumulation curve provides evidence that sam-
pling efforts should be reinforced in order to compile a macrophyte flora census for South America. The high
dissimilarity among South American wetlands, together with the lack of an asymptote in our species accumula-
tion curve, indicates that the sampling effort needs to be increased to account for the actual species richness of
macrophytes in this region. Rev. Biol. Trop. 59 (2): 541-556. Epub 2011 June 01.
Key words: floristic survey, plant diversity, aquatic plants, Brazil.
Wetlands are important sites for biological
conservation because they support rich biodi-
versity and present high productivity (Mitsch &
Gosselink 2000). The study of wetland plants
has been of interest to botanists for many years,
but the effort to identify and understand these
plants has increased dramatically since the
1970s, when ecologists began to emphasize the
vital role that wetlands play in our landscapes
(Cronk & Fennessy 2001).
One of the main ecological characteristics
of South America is the existence of large
wetlands (Neiff 2001). Inventories of wetlands
provide an indication of the sites with the
highest biological diversity and productiv-
ity (Taylor et al. 1995), and the information
collected through inventories is a necessary
prerequisite for conservation policies (Pressey
& Adam 1995).
Approximately 50% of the inventoried
wetlands in South America are located in Brazil
(Naranjo 1995). However, specific information
related to aquatic macrophytes is extremely
scarce. Diegues (1994) performed the first

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inventory of wetlands in Brazil, and his work
provided valuable data for evaluating eco-
logical and economic aspects of these regions.
According to Neiff (1978, 1986), aquatic mac-
rophytes are important in shallow ecosystems,
such as river-floodplain ecosystems, where
they colonize extensive areas and exhibit high
rates of primary productivity. In addition,
macrophytes are a key component of river-
floodplain ecosystems because they enhance
nutrient cycling, increase habitat heterogeneity
and provide food for a variety of organisms
(Esteves 1998).
Floodplains are known as ecosystems with
a high diversity of habitats and aquatic and
terrestrial species (Junk et al. 2000). Due to
their high complexity and seasonal changes in
physico-chemistry, these ecosystems are char-
acterized by a variety of assemblages, which
differ in richness and composition accord-
ing to the water level. In the Upper Paraná
River floodplain, for example, the vegeta-
tion is highly conditioned by geomorphology
(Souza-Filho 1993); trees dominate the more
elevated areas (levees), and shrubs colonize
less elevated areas that remain flood-free most
of the year, while aquatic macrophytes grow in
permanently inundated areas of the wetlands.
Despite the importance of these macro-
phytes in the Upper Paraná River floodplain, a
stretch of this river that is key in maintaining
the biodiversity of Brazilian inland waters,
information about the aquatic vegetation in
this region is scattered among several different
papers and reports (Bini 1996, Kita & Souza
2003, Thomaz et al. 2004, Thomaz et al. 2009);
most of these studies emphasized that the flood
pulse and changes in water physico-chemistry
are important factors controlling macrophyte
populations and communities.
In the present study, we first addressed the
number of macrophyte species in the main hab-
itats of the Upper Paraná River and its flood-
plain (herein only Paraná floodplain), using
records gathered since 1997 and intensive
collections performed between 2007 and 2009.
Secondly, we used this dataset to compare the
species richness and similarity of this area with
other South American wetlands. Finally, using
species accumulation curves, we examined
whether the number of species described in
South America is reaching an asymptote, or
if more sampling efforts are still necessary to
accomplish a comprehensive inventory of the
rich aquatic flora of this area.
To accomplish these objectives, we adopt-
ed the conceptualization of aquatic macro-
phytes proposed by Cook (1996), in which the
author includes plants which photosyntheti-
cally active organs are either permanently, or
for several months of the year, total or partially
submersed in freshwater or floating in aquatic
habitats. More recently, Chambers et al. (2008)
also included Charophytes within the defini-
tion of macrophytes. To avoid any confusion,
we did not use in any part of our text the term
“vascular plants” but, instead, consistently used
the term “aquatic macrophytes”.
MATERIALS AND METHODS
Study area: The floodplain of the Paraná
River is located downstream from the Porto
Primavera Reservoir. This stretch has a length
of 160km and is the last region of the river
that remains not dammed in Brazilian territory.
Thus, it is of key importance to the conserva-
tion of the aquatic biodiversity of the Paraná
Basin (Agostinho & Zalewiski 1995).
According to the Köppen system, the
climate in this region is classified as tropical
and sub-tropical, with warm summers (mean
annual temperature 22oC) and a mean annual
rainfall of 1 500mm (Maack 2002).
The compiled list of taxa was based on
records of samplings conducted in the flood-
plain since 1997. In addition, we utilized sev-
eral other studies (published and unpublished)
that had been conducted in the floodplain.
Macrophytes were collected in a variety of
habitats, such as the river main channel, lateral
channels (anabranches), temporary and perma-
nent lakes, and in the aquatic-terrestrial transi-
tion zone (ATTZ, sensu Junk et al. 1989). We
also analyzed and revised specimens depos-
ited in the Laboratory of Macrophytes and in

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the Herbarium (HUEM) of the University of
Maringá. To complement the list of species
recorded in previous investigations, we carried
out additional samplings between 2007 and
2009 in six habitats that are being monitored in
the Brazilian Long Term Ecological Research
Program (site 6; Thomaz et al. 2009).
In each lake, the aquatic macrophytes
were analyzed by boat at a slow speed along
the entire shoreline. In the ATTZ, samplings
were carried out on foot. We used a grapple
attached to a line to record submersed species.
Because ponds and lakes have small areas
(from 0.006 to 113.8ha) and samplings were
carried out on the entire shores, we considered
the recorded species as the actual richness of
these habitats, and did not correct the results to
account for sampling effort (rarefaction curves,
for example).
Identification followed comparative mor-
phology and a specialized bibliography (e.g.,
Hoehne 1948, Cook 1996, Pott & Pott 2000,
Amaral et al. 2008, Bove & Paz 2009). The list
of taxa contains families and genera according
to the “Angiosperm Phylogeny Group-APG
II” (2003) for Magnoliophyta (Angiospermae),
Willis (1973) for Pteridophyta, and Crandall-
Stotler (1980) for Hepatophyta.
Plant life forms were chosen according to
Pedralli (1990), and we followed Tur (1972)
for epiphytic forms. Plants growing in wet
soils (marshes locally known as “varjão” or
“várzea”) were included in the category of
amphibious (Irgang & Gastal 1996).
In order to make comparisons among
South American wetlands, we used the follow-
ing lists of macrophytes obtained in long-term
surveys (Table 1).
All of the investigations and the lists of spe-
cies that we used were carried out by specialists
and included several types of habitats (Fig. 1).
Although there are several other papers describ-
ing single habitats, we did not use these studies.
It is difficult to guarantee that all studies follow
the same methodology, but we believe that they
are similar enough to at least contribute a first
tentative of comparison of Neotropical wetlands
to make inferences about the richness of macro-
phytes in this region.
To find similarity among these surveys, we
first converted all data into a large matrix con-
taining species occurrence presence/absence. A
matrix of similarity was built using the Bray-
Curtis distance coefficient (Krebs 1999). To
compare all surveys, we used the method of
complete linkage (Sneath & Sokal 1973). A
dendrogram of similarities was built using the
PRIMER v. 6 software, Plymouth Routines in
Multivariate Ecological Research (Clarke &
Gorley 2006).
Using the entire dataset, which included
all wetlands, we assessed whether the richness
of macrophytes in South America reaches an
asymptote, or if there are many species yet to
be found. The expected species accumulation
curve was calculated according to a Mao Tau
function. Using an accumulative curve with
“studies” as units of sampling effort, an asymp-
tote would indicate whether almost all species
Fig. 1. Regions of South America included in the
sampling sites.
South America
Colombia
Ecuador
Brazil
Peru
Bolivia
Sampling sites
Argentina
0 10 20 30 40 100 km
Scale

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TABLE 1
List of reports used to compare South American wetlands. The terms in bold represent the corresponding analysis cluster
Author(s) Study region Type of environment
1 Thomaz et al. (2009) Upper Paraná River floodplain, Brazil
(PR)
River channels, secondary channels,
lagoons, swamps
2Irgang & Gastal (1996) Coastal plain of Rio Grande do Sul,
Brazil (CP)
Swamps, saltmarshes, rivers, lakes,
temporary ponds
3Pott & Pott (2000) Pantanal Matogrossense, Brazil (Pan)Shallow lakes, rivers, swamps,
floodplains, meandering ponds meander,
“corixos”, “vazantes”, borrow pits,
temporary ponds, permanent ponds
4 Bove et al. (2003) State of Rio de Janeiro, Brazil (RJ)Coastal lagoons, lakes, permanent and
temporary swamps, floodplains
5 França et al. (2003) Brazilian semiarid Northeast region (SA)Artificial ponds
6 Thomaz et al. (2003) State of Amapá, Brazil (AMA)“Ressaca”, environments influenced by
tidal water regimes
7Kahn & Leon (1993) Peru (Pe)Brackish ponds, mangroves, rivers, lakes,
wetlands
8Crow (1993) Ecuador (Ec)Lacustric systems
9Terneus (2007) The Amazon basin of Ecuador (AmEc)Lakes, streams, rivers
10 Scremin-Dias et al. (1999) Bodoquena in the State of Mato Grosso
do Sul, Central-West, Brazil (Bo)
Limestone springs and streams
11 Junk & Piedade (1993) Amazon River near Manaus, Brazil (Am)Floodplain, “várzea” lakes, floating
islands, low-lying flats, low-lying swales,
river shores, lake shores
12 Neiff (1986) Middle Paraná River floodplain,
Argentina (PRA)
Rivers, swamps, washways, permanent
ponds, flooded ponds
have already been recorded; however, the lack
of an asymptote would indicate that the number
of aquatic macrophyte species found until now
is still far from the real total of these species.
We also estimated the richness of macrophytes
using a first-order Jacknife estimator (Jack1)
with the objective to assess the extent to which
the number of macrophyte species in South
America remains underestimated. Accumula-
tion and estimation curves were constructed
using the EstimateS program (Colwell 2009).
RESULTS
A total of 153 species of macrophytes was
recorded in the Upper Paraná River floodplain.
These species were distributed in 100 genera
and 37 families (Appendix 1), representing
a variety of taxonomic groups (Charophyta,
Bryophyta, Pteridophyta, Basal Angiospermae
and Angiospermae).
Sixteen of the recorded species are cryp-
togams and are classified as follows: two
charophytes, two hepatophytes and 12 pterido-
phytes. Of the Angiospermae, Poales exhibited
the highest number of taxa (40), followed by
Alismatales (17), Myrtales and Lamiales (12
species each). The families with the high-
est numbers of species were Poaceae (21),
Cyperaceae (17), Pontederiaceae (8), Hydro-
charitaceae (7), Polygonaceae and Onagraceae
(6) and Fabaceae (5). Araceae, Alismataceae,
Commelinaceae, Amaranthaceae and Plantag-
inaceae were represented by four species each
and the other families by three or fewer species.
All life forms were found in the area, and
emergent and amphibious types were the most
representative macrophytes, contributing 45%
and 26% of the species, respectively (Fig. 2).

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Rooted submersed (11%) and free-floating spe-
cies (9%) were also important, while the low-
est numbers of species were found for rooted
floating and free-submersed types (2%) and
epiphytes (1%).
The number of species recorded in the
Paraná River and its floodplain consistently
increased over time (Fig. 3). The greatest
increase occurred between 2007 and 2009, due
to intensified sampling efforts and refined taxo-
nomic identification, which led to the addition
of 105 species to the recorded flora of the
Upper Paraná River floodplain.
The Paraná floodplain exhibits the third
highest richness of macrophytes (153 species)
of the 12 areas for which we have data in South
America. The coastal area of the State of Rio
Grande do Sul (Brazil) ranked first (321 spe-
cies), and the Pantanal Matogrossense, one of
the largest wetlands in the world, ranked sec-
ond (247 species).
A dendrogram built using the Bray-Cur-
tis coefficient of distance showed that South
American wetlands are dissimilar with respect
to macrophyte assemblages (Fig. 4). We can
roughly recognize three groups of wetlands.
The first includes the seasonal ponds (North-
east Brazil), coastal lagoons of the State of Rio
de Janeiro, Pantanal, Paraná floodplain in Bra-
zil, the coastal plain in the State of Rio Grande
do Sul and the Paraná floodplain in Argentina,
with a similarity of 11.7% (Fig. 4). These areas
share only two species in common, Polygonum
ferrugineum and Nymphoides indica, both of
which are widespread hydrophytes. In this first
group, the most similar areas were the Paraná
floodplain and the Pantanal Matogrossense
with 40.2% similarity and 79 species in com-
mon (9% of the total species)
The second group included the Amazon
basin of Ecuador, Amazon River floodplain
and Amapá wetlands, with a similarity of
13% and sharing four species, Eichhornia
azurea, Hymenachne amplexicaulis, Salvinia
auriculata and Utricularia foliosa. Within this
group, the aquatic flora of the Amazon River
floodplain and the Amazon Basin of Ecuador
share 13 species (2% of the total species) and
exhibit 35.1% similarity. Finally, group three
was formed by Peru, Ecuador and Bodoquena
(Mato Grosso do Sul), with a similarity of 18%
and sharing 11 species; within this group, Peru
and Ecuador had the highest similarity of 33.6%
and sharing 35 species (4% of all species).
Considering all of the surveys that we
found for South America together with the
survey we conducted in the Paraná floodplain,
a total of 854 species of macrophytes was
compiled. However, the species accumulation
Number and % of species
80
70
60
50
40
30
20
10
0
Species number
Speces percentage (%)
Life Form
Am Em Ep Rf Ff Rs Fs
Fig. 2. Number of species and percentage of each life form
recorded in the Paraná floodplain. (Am - amphibious; Em
- emergent; Ep - epiphyte; Rf - rooted floating; Ff - free-
floating; Rs - rooted submersed; Fs - free submersed).
Fig. 3. Cumulative number of recorded species in the
Paraná River floodplain between the years 1997 and 2009.
The arrow indicates instances when plant taxonomic
identification was improved.
Cumulative number of species
160
140
120
100
80
60
40
20
0
Years
1997 2003 2005 2007 2008 2009

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curve produced using these studies as a sur-
rogate of sampling effort, did not reach an
asymptote (Fig. 5). In fact, the number of
species estimated through Jack1 was 1 388,
indicating an approximate underestimation of
534 species.
DISCUSSION
According to Chambers et al. (2008), the
Neotropical region has the highest number of
macrophyte species in the world (984 spe-
cies). The number of species of macrophytes
recorded in the Upper Paraná River and its
floodplain (153 species; 16% of the Neo-
tropical region) can be considered high due
to the small relative area of this ecosystem
(2 500km2) compared to other aquatic areas
from this region, such as the Amazon and the
Pantanal. Even considering the higher species
richness found in the Pantanal Matogros-
sensse (247 species), our survey still indicates
that the Paraná floodplain is highly diverse
because the Pantanal is 55 times larger in area,
extending over approximately 138 183km2.
Thus, the conservation units contained inside
this stretch of the Paraná River can be consid-
ered important for the conservation of aquatic
macrophyte diversity. Again, we emphasize
that the number of species we recorded does
not represent the real species richness because
Fig. 4. Cluster showing the Bray-Curtis similarity of the different wetlands in South America. SA - Semi-arid region in
the State of Bahia; RJ - Coastal lagoons of the State of Rio de Janeiro; Pan - Pantanal; PR - Paraná floodplain in Brazil;
CP - Coastal plain in the State of Rio Grande do Sul; PRA - Paraná floodplain in Argentina; AmEc - Amazon basin of
Ecuador; Am - Amazonas River Floodplain; AMA - Amapá wetlands; Pe - Peru; Ec - Ecuador; and Bo - Bodoquena (Mato
Grosso do Sul).
0 20 40 60 80 100
SA
RJ
Pan
PR
CP
PRA
AmEc
Am
AMA
Pe
Ec
Bo
1
2
3
Similarity Bray-Curtis (%)
Fig. 5. Species accumulation curve derived from studies as
a surrogate of sampling effort.
Number of species
Number of studies
1600
1400
1200
1000
800
600
400
200
0
1 2 3 4 5 6 7 8 9 10 11 12
Estimated (Jack 1)
Observed

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there are a number of habitats not yet investi-
gated in this stretch.
The comparison of the region investigated
in this study with other dammed stretches sug-
gests the importance of the Paraná floodplain
as a hotspot of macrophyte species diversity in
this basin. In a survey of 18 reservoirs of the
Paraná River and some of its main tributaries,
Martins et al. (2008) found only 39 species
of macrophytes. Even in the Itaipu Reservoir,
which is dendritic (and thus, favorable for
macrophyte colonization), a long-term data-
set showed a total of 110 species (Mormul et
al. 2010). The same conclusion can be made
when we compare our data with reservoirs
from other basins; for example, only 23 spe-
cies of macrophytes were recorded in the
Guri Reservoir, Venezuela (Vilarrubia & Cova
1993). The great variety of habitats found in
the Paraná floodplain, together with the natural
disturbance caused by seasonal oscillations in
the water level, might explain these differences
in relation to different reservoirs. On the other
hand, the sampling effort was not controlled
in these different surveys, and thus the results
should be viewed with caution. However, this
pitfall might be minimized because all of the
investigations that we included in this report
were floristic surveys, which tend to maximize
the sampling within a region. In addition, there
may be differences in the definition of mac-
rophytes used in different surveys. Consider-
ing species composition, the assemblages of
the Paraná floodplain can be considered as a
sample of the aquatic flora from the Pantanal,
as was previously pointed out by Thomaz et al.
(2009). In fact, the most representative families
in number of species are largely the same for
both ecosystems (Poaceae and Cyperaceae,
Onagraceae, Pontederiaceae, Plantaginaceae
and Fabaceae). The families with few species in
both ecosystems are also the same (Typhaceae,
Cucurbitaceae, Maranthaceae, Haloragaceae,
Solanaceae and Orchidaceae). Our cluster anal-
ysis also indicated that these three wetlands are
the most similar amongst all ecosystems in our
dataset, which could be due to their geographi-
cal proximity and to hydrological similarities
(all areas are subjected to seasonal variation in
the water level and also include a great variety
of habitats). Furthermore, both wetlands belong
to the same larger Paraná basin.
However, some families differ consider-
ably in the number of species between these
two wetlands. For example, there are only two
species of Nymphaeaceae in the Paraná flood-
plain, whereas there are eight in the Pantanal
that occur mainly in rain-fed shallow ponds
and seasonal standing or slow flowing water
in addition to in the river floodplain, except
for Victoria amazonica, which grows in oxbow
lakes. Similarly, 10 species of Characeae were
found in the Pantanal, which is attributed to the
alkaline and brackish waters in the Southwest-
ern Pantanal (Bueno 1993, Pott & Pott 1997),
but only two were identified in the Paraná
floodplain, where acid soils predominate and
charophytes do not thrive. The importance of
the type of habitat in determining species com-
position can also be observed if we compare a
survey carried out on lakes, reservoirs and wet-
lands in the Southern Paraná State (Cervi et al.
2009), only 200km away, that shares only 23%
of macrophytes with the Paraná floodplain.
The low richness of aquatic epiphytes
reported in the Paraná floodplain is related to
the small sampling effort that has been carried
out on floating meadows. Epiphytes usually
colonize advanced stages of aquatic succes-
sion (Pott & Pott 2003). For example, surveys
carried out by Tur (1972) and Neiff (1982) in
the Middle Paraná (Argentina) identified 70
species of epiphytes. Even though both regions
are on the Paraná River, the flood pulses dif-
fer between the Middle and the Upper Paraná
basins, which may influence the accumulation
of organic matter and, thus, the formation of
floating-substrates, as well as the displacement
of these islands, and this may explain the dif-
ferences in the richness of epiphytes found in
these wetlands.
The species number increase over time
reported for the Paraná floodplain can be
mainly attributed to the refinement of the taxo-
nomic searches and identification carried out.
In addition to this effect, we also considered a

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higher sampling effort in the Paraná floodplain,
with collections made in habitats not previ-
ously investigated (e.g., rocks in the Paraná
channel) and the arrival of new species (e.g.
Hydrilla verticillata). The high level of species
richness that we found indicates that the Paraná
floodplain is still in a good conservation state,
despite the strong anthropogenic pressures in
the region related to changes in hydrometric
levels, nutrient cycling and suspended solid
loadings (Souza-Filho 2009).
However, despite the good status of con-
servation with respect to the aquatic flora, we
contend that there is a concern related to the
presence of two invasive species, H. verticil-
lata and Urochloa subquadripara. The first is a
submersed species native to Asia and the North
of Africa, that colonizes the Paraná main chan-
nel and has a high competitive ability, threaten-
ing native species due its rapid regeneration
following hydrological disturbances (Sousa
et al. 2009, Thomaz et al. 2009). Its success
in the Paraná main channel is associated with
the same effect leading to an increase in the
colonization by submersed species, i.e., the
increase in water transparency and propagule
pressures originating in the upstream reservoirs
(Thomaz et al. 2009). Hydrilla verticillata has
not yet colonized lakes in either the Baía or
Ivinhema river habitats (Sousa et al. 2009).
The second species, U. subquadripara, belongs
to the family Poaceae, which contributes with
several invasive species (Petenon & Pivello
2008). Although U. subquadripara has been
rarely recorded in the Paraná floodplain, it
reduced significantly the diversity of macro-
phytes in a lake close to the Baía River, the
only place where it occurs with high biomass in
this floodplain (Michelan et al. 2010). Distur-
bances associated with the oscillation in water
levels may explain why this species is so rare
in most habitats in the floodplain, but in light
of its severe threat to macrophyte diversity, its
monitoring is a priority, especially in the best
preserved areas of this region.
The results of our cluster analysis indi-
cate that Neotropical wetlands are different
regarding macrophyte composition. Thus, we
infer that such differences may be due to mul-
tiple factors, such as climate, flood regime
and geography.
In fact, the most similar areas (Pantanal
and Paraná floodplain) share many similarities:
they are both large floodplains located from
80-160 m.a.s.l., have a great variety of habitats
and are subjected to seasonal water level fluc-
tuations (Agostinho & Zalewiski 1995, Vila
da Silva 1995). However, the cluster analysis
also shows that South American wetlands are
diverse regarding macrophyte assemblages,
and even ecosystems located in the same basin
may differ considerably (e.g., the upper and
middle/lower Paraná floodplains). The dif-
ferences observed for these two floodplains
may be accounted for by differences in their
nutrient regimes (the Argentinean floodplains
receive high phosphorus inputs from the Andes
tributaries) and also to the types of habi-
tats investigated (e.g., the widespread occur-
rence of floating meadows in Argentina with
a high richness of epiphytes). As previously
mentioned, the groups formed by the cluster
analysis suggest that, though they represent
geographically distant environments, such as
the Amazonian floodplains and the Argentina
plain, the sampled landscapes are determinant
in forming groupings.
The accumulation curve reflects the dif-
ferences found in the cluster analysis. In other
words, the great differences among the South
American surveys included in the cluster analy-
sis indicate a high beta-diversity, leading to a
lack of an asymptote in the accumulation curve.
The total number of species found in all 12
surveys represents 87% of the number found
by Chambers et al. (2008) for the Neotropical
region. Despite the fact that our findings are
close to the total number of Neotropical mac-
rophytes, the lack of an asymptote, together
with the high underestimation of true richness
suggested by the Jack1 estimator, indicates
that we are still far from describing the actual
richness for this region. The number of plants
to be described in Brazil, what may reflect
the situation of South America, is considered
very high (Pimm et al. 2010). In fact, there has

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been a clear lack of investigations conducted in
pristine habitats in South America, such as in
parts of the Amazon and the Andes, which are
areas of high biodiversity. Future investigations
at these sites, together with the description of
new species (e.g., Bove et al. 2006, Amaral
& Bittrich 2008), will certainly increase the
number of species of Neotropical macrophytes
recorded and give a better idea of the biodiver-
sity provided by the great variety of ecosystems
of this biogeographical region.
Our results reinforce the hypothesis of
Irgang & Gastal (1996) that Uruguay, North
Argentina, Paraguay and South Brazil form a
phytogeographic unit, and therefore, the sam-
pled number of species does not closely correlate
with other evaluated areas. There are many other
large wetlands in South America that should
be included in this analysis but that were not
included because of insufficient floristic inven-
tories, such as Guaporé and Ilha do Bananal.
In summary, this report highlights the
flora of different wetlands of South America
and indicates that the actual species richness of
macrophytes of this continent is far from being
well understood. Our hypothesis sustains that
macrophyte records, together with existing sur-
veys, indicate a continuous need for carrying
out increasing numbers of collections in new
areas in the upper Paraná river-floodplain sys-
tem and in other South American wetlands, as
the number of species so far reported remains
far from the predicted total. The checklist
generated in this study is intended to support
other research in wetlands and, in particular,
to assure the continuity of ongoing long-term
ecological programs, and it reveals a rich
flora that is practically unknown to botanists
and ecologists.
ACKNOWLEDGMENTS
This study was funded by the Brazilian
Council of Research (CNPq) through a Long
Term Ecological Program (site number 6).
S. M. Thomaz received a CNPq Productivity
Research Grant and acknowledges this agency
for long-term funding. A. Pott received a CNPq
and CAPES Productivity Research. Addition-
ally, F. A. Ferreira and R. P. Mormul acknowl-
edge CNPq and CAPES (Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior)
for furnishing Ph.D. fellowships, respectively.
RESUMEN
Los ecosistemas acuáticos neotropicales tienen una
rica flora acuática. En este informe, hemos hecho una lista
de la flora acuática de diversos hábitats de la alta planicie
de inundación del río Paraná mediante la compilación de
datos de la literatura y los registros de nuestras colecciones
propias realizadas durante el período 2007-2009. Nuestros
principales objetivos fueron evaluar la riqueza de macró-
fitos en la llanura aluvial del Paraná, para compararlo con
otros humedales de América del Sur y evaluar si el número
de especies registradas en los inventarios suramericanos
ya han alcanzado una asíntota. Se registraron un total de
153 especies de macrófitas en la llanura de inundación
del Río Alto Paraná, pertenecientes a 100 géneros y 47
familias. En nuestro análisis comparativo, se mostró una
clara división florística de otros humedales de América del
Sur, con excepción del Pantanal, que es el más cercano a
los humedales de la planicie de inundación del Paraná y,
por tanto, podría considerarse una extensión florística del
Pantanal. La curva de acumulación de especies demuestra
que los esfuerzos de muestreo deben ser reforzados con
el fin de elaborar un censo de la flora de macrófitos para
América del Sur. La alta disimilitud entre los humedales
de América del Sur, junto con la falta de una asíntota en
nuestra curva de acumulación de especies, indica que el
esfuerzo de muestreo debe ser mayor para dar cuenta de la
riqueza real de las especies de macrófitos en esta región.
Palabras clave: Inventario florístico, diversidad de plan-
tas, plantas acuáticas, Brasil.
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APPENDIX I
List of taxa recorded in the Paraná River floodplain between the years 1996 and 2009
TAXA L.F.
Characeae - Charophyta
Chara guairensis R. Bicudo Rs
Nitella furcata (Roxb. ex Bruz.) Ag. emend. R.D. Wood Rs
Ricciaceae - Hepatophyta (Bryophyta)
Riccia sp. Em
Ricciocarpus natans L. (Corda) Ff
Azollaceae - Pteridophyta
Azolla filiculoides Lam. Ff
A. microphylla Kaulf. Ff
Blechnaceae - Pteridophyta
Blechnum brasiliense Desv. Em
B. serrulatum Rich. Em
Pteridaceae - Pteridophyta
Ceratopteris pteridoides (Hook.) Hieron. Ff
Pityrogramma calomelanos (L.) Link var. calomelanus Em
P. trifoliata (L.) R. Tryon Em
Salviniaceae - Pteridophyta
Salvinia auriculata Aubl. Ff
S. biloba Raddi emend de la Sota Ff
S. minima Baker Ff
Thelypteridaceae - Pteridophyta
Thelypteris interrupta (Willd.) K. Iwats. Em
T. serrata (Cav.) Alston Em
Nymphaeaceae – Basal Angiospermae
Cabomba furcata Schult. & Schult. f. Rs
Nymphaea amazonum Mart. ex Zucc. subsp. amazonum Rf
Alismatales - Monocots
Araceae
Lemna valdiviana Phil. Ff
Pistia stratiotes L. Ff
Wolffiella lingulata (Hegelm.) Hegelm. Ff
W. oblonga (Phil.) Hegelm. Ff
Hydrocharitaceae
Egeria densa Planch. Rs
E. najas Planch. Rs
Hydrilla verticillata (L.f.) Royle Rs
Limnobium laevigatum (Humb. & Blonpl. ex Willd.) Heine Ff
Najas conferta (A. Braun) A. Braun Rs
N. microcarpa K. Schum. Rs
Alismataceae
Echinodorus grandiflorus (Cham. & Schltdl) Micheli Em
E. tenellus (Mart. ex Schult. & Schult. f.) Buchenau Rs
Sagittaria montevidensis Cham. & Schltdl. Em
S. rhombifolia Cham. Em

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APPENDIX I (Continued)
List of taxa recorded in the Paraná River floodplain between the years 1996 and 2009
TAXA L.F.
Limnocharitaceae
Hydrocleys nymphoides (Willd.) Buchenau Rf
Potamogetonaceae
Potamogeton pusillus L. ssp. pusillus Rs
Asparagales
Orchidaceae
Habenaria repens Nutt. Ep
Habenaria sp. Ep
Poales
Typhaceae
Typha domingensis Pers. Em
Xyridaceae
Xyris jupicai Rich. Em
Cyperaceae
Cyperus diffusus Vahl Em
C. digitatus Roxb. Am
C. ferax Benth. Em
C. giganteus Vahl Em
C. haspan L. Em
C. surinamensis Rottb. Em
Cyperus sp. Am
Eleocharis elegans (Kunth) Roem. & Schult. Em
E. filiculmis Kunth Em
E. geniculata (L.) Roem. & Schult. Em
E. minima Kunth Em
E. montana (Kunth) Roem. & Schult. Em
Frimbristylis autumnalis L. Am
Oxycaryum cubense (Poepp. & Kunth) Palla Ep
Rhynchospora corymbosa (L.) Britton Am
Scleria melaleuca Rchb. ex Schltr. & Cham. Am
S. pterota C. Presl Am
Poaceae
Acroceras zizanioides (Kunth) Dandy Am
Echinochloa polystachya (Kunth) Hitchc. Am
E. crus-pavonis (Kunth) Schult. Em
Eragrostis bahiensis (Schrad. ex Schult.) Schult. Am
Eragrostis hypnoides (Lam.) Britton, Sterns & Poggenb. Em
Hymenachne amplexicaulis (Rudge) Nees Em
Leersia hexandra Sw. Am
Megathyrsus maximus (Jacq.) B. K. Simon & S. W. L. Jacobs. Am
Panicum dichotomiflorum Michx. Em
P. mertensii Roth Am
P. pernambuncense (Spreng.) Mez ex Pilg. Em
P. prionitis Nees Am
P. rivulare Trin. Am

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APPENDIX I (Continued)
List of taxa recorded in the Paraná River floodplain between the years 1996 and 2009
TAXA L.F.
P. sabulorum Lam. Am
Paspalum conspersum Schrad. Am
P. millegrana Schrad. Em
P. repens P.J. Bergius Em
Setaria pauciflora Linden ex Herrm Am
Steinchisma laxa (Sw.) Zuloaga Am
Urochloa humidicola (Rendle) Morrone & Zuloaga Am
Urochloa subquadripara (Trin.) R.D. Webster Em
Commelinales
Commelinaceae
Commelina diffusa Burm. f. Am
C. nudiflora L. Em
C. schomburgkiana var. brasiliensis Seub. Em
Floscopa glabrata (Kunth) Hassk. Em
Pontederiaceae
Eichhornia azurea (Sw.) Kunth Rf
E. crassipes (Mart.) Solms Ff
Heteranthera reniformis Ruiz & Pav. Em
H. seubertiana Solms Em
Heteranthera sp. Em
Pontederia cordata L. Em
P. parviflora Alexander Em
P. triflora (Seub.) G. Agostini, D. Velásquez & Velásquez Em
Zingiberales
Maranthaceae
Thalia geniculata L. Em
Ceratophyllales – Eudicotyledoneae
Ceratophyllaceae
Ceratophyllum demersum L. Fs
Caryophyllales - Core Eudicotyledoneae
Polygonaceae
Polygonum acuminatum Kunth Em
P. ferrugineum Wedd. Em
P. hydropiperoides Michx. Em
P. meisnerianum Cham. & Schltdl. Em
P. punctatum Elliot Em
P. stelligerum Cham. Em
Amaranthaceae
Alternanthera philoxeroides (Mart.) Griseb. Am
Gomphrena elegans Mart. Em
Pfaffia glomerata (Spreng.) Pedersen Am
P. iresinoides (Kunth) Spreng. Am
Haloragaceae
Myriophyllum aquaticum (Vell.) Verdc. Rs

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APPENDIX I (Continued)
List of taxa recorded in the Paraná River floodplain between the years 1996 and 2009
TAXA L.F.
Myrtales - Rosidea
Onagraceae
Ludwigia grandiflora (Michx.) Greuter & Burdet Em
L. helminthorrhiza (Mart.) H. Hara Rf
L. lagunae (Morong) H. Hara Em
L. leptocarpa (Nutt.) H. Hara Em
L. octovalvis (Jacq.) P.H. Raven Am
L. peruviana (L.) H. Hara Em
Lythraceae
Cuphea melvilla Lindl. Em
C. sessiliflora A. St.-Hil. Am
Rotala mexicana Schltdl. & Cham. Rs
Melastomataceae
Acisanthera sp. Em
Malpighiales – Eurosideae I
Podostemaceae
Crenias sp. Rs
Podostemum rutifoliumWarming var. rutifolium Rs
Euphorbiaceae
Caperonia castaneifolia (L.) A. St.-Hil. Em
Phyllanthaceae
Phyllanthus niruri L. Am
Fabales
Fabaceae
Aeschynomene montevidensis Vogel Em
A. sensitiva Sw. Em
A. virginica (L.) Britton, Sterns & Poggenb. Am
Sesbania cf. exasperata Kunth Am
Fabaceae
Vigna lasiocarpa (Mart.ex Benth.) Verdc. Em
Cucurbitales
Cucurbitaceae
Cyclanthera hystrix (Gillies) Arn. Am
Begoniaceae
Begonia cucullata Willd. Am
Malvales - Eurosideae II
Malvaceae
Byttneria scabra L. Am
Hibiscus sororius L. Em
Melochia arenosa Benth. Am
Gentianales - Euasterideae I
Rubiaceae
Diodia brasiliensis Spreng. Am
Apocynaceae
Oxypetalum sp. 1 Am

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APPENDIX I (Continued)
List of taxa recorded in the Paraná River floodplain between the years 1996 and 2009
TAXA L.F.
Oxypetalum sp. 2 Am
Rhabdanenia pohlii Mull. Arg. Em
Lamiales
Plantaginaceae
Bacopa salzmannii Wettst. ex Edwall Rs
Mecardonia procumbens (Mill.) Small Em
Scoparia dulcis L. Em
S. montevidensis (Kuntze) R.E. Fr. Em
Linderniaceae
Lindernia sp. 1 Rs
Lindernia sp. 2 Rs
Acanthaceae
Hygrophila costata Nees Em
H. guianensis Nees Em
Justicia comata (L.) Lam. Am
Lentibulariaceae
Utricularia foliosa L. Fs
U. gibba L. Fs
U. nigrescens Sylvén Fs
Solanales
Solanaceae
Schwenckia americana L. Am
Solanum glaucophyllum Desf. Am
Convolvulaceae
Ipomoea alba L. Em
Hydroleaceae
Hydrolea spinosa L. Em
Apiales - Euasterideae II
Apiaceae
Eryngium ebracteatum Lam. Em
E. ekmanii H. Wolff Em
Hydrocotyle ranunculoides L.f. Rf
Asterales
Menyanthaceae
Nymphoides indica (L.) Kuntze Rf
Asteraceae
Eclipta prostrata (L.) L. (=alba) (L.) Hassk.) Am
Mikania cordifolia (L. f.) Willd. Am
Pluchea sagittalis (Lam.) Cabrera Em
(L.F.=life forms; Em=emergent, Rs=rooted submerged, Ff=free-floating, Am=amphibious, Rf=rooted floating, Fs=free
submerged and Ep=epiphyte).