Checklist of vascular plants of the Department of Ñeembucú, Paraguay

Abstract The Department of Ñeembucú is one of the least well-documented areas of eastern Paraguay, and the flora is composed of a mixture of forest and Chaco elements. Regions like Ñeembucú are often considered of lower diversity and interest that more forested regions; this results from both actual species richness figures and from under-collecting due to perception as uninteresting. We present here a checklist of the vascular plants of Ñeembucú, which includes 676 taxa (including infraspecific taxa and collections identified only to genus) in 100 families and 374 genera. Four hundred and thirty nine (439) of these are new records for Ñeembucú and of these, 4 are new published records for Paraguay. Synonyms, distribution details within Paraguay and a voucher specimen or literature record are provided for each taxon, and a brief analysis of the diversity and importance of the flora is presented.


Introduction
Paraguay is a land-locked country between 19° and 28° south latitude and 54° and 63° west longitude at the heart of the South American continent, and lies entirely within the Río de la Plata drainage system, second only in size to the Amazon basin. Th e country is divided by the Río Paraguay into the Oriental, or eastern, region, also known as the Paraná region; and the Occidental, or western, region, also known as the Chaco, part of the Gran Chaco Americano that is shared by Argentina, Bolivia and Paraguay. Paraguay is divided into 17 departments, 14 of which are to the east of the Río Paraguay.
Th e department of Ñeembucú is the southernmost tip of Paraguay and is located in the south-western corner of the Oriental region, between 57°35' -57°55' W latitude and 25°50' -27°19' S longitude (Fig. 1). Ñeembucú covers an approximate area of 12,147 square kilometres (SINASIP 2009). Th e average annual temperature is between 22° and 23°C, and average annual rainfall is around 1500 mm (Acevedo et al. 1990). Most of this area is made up of a plain comprised of alluvial sediments from the Quaternary period, with hydromorphic soils formed from the transport of sediment by rivers and streams, and dominated by shallow hydromorphic and alluvial gley types, planosols or gley humic acids with high organic matter content (Tortorelli 1966).
Ñeembucú is partially surrounded by both the Paraguay and Parana rivers and has a number of extensive wetlands, the largest of these being the Ñeembucú and the Cambá marshes. Th e area is low elevation and relatively fl at; altitudinal range is between 50 and 124 metres above sea level. As a result of these particular topographic and hydrographic features, Ñeembucú is usually described as one extensive fl oodplain; over 85% of this area is wetlands (Fogel 2000), where water is the primary factor that regulates seasonal variation and biological and ecological characteristics of the vegetation composition. Th e wetlands of Ñeembucú are the largest in the Oriental region and are very rich in terms of alpha and beta diversity, particularly when it comes to species of fl ora and fauna closely linked to water (Vogt and Mereles 2005).
Th e wetlands of the Oriental region were studied by Mereles and Aquino-Shuster (1990), Mereles et al. (1992), and Mereles (1993;2004). Vegetation of the Ñeembucú stream basin, which can be considered as representative of the department, was described in detail by Vogt and Mereles (2005), who identifi ed two principal vegetation types; 1) those subject to permanent fl ooding, and 2) those linked to periodic fl ooding.
Vegetation that remains fl ooded throughout the year can be characterised as lotic or lentic. Lotic environments are typical of the extensive network of fl owing waterways distributed throughout the department; common species include Nymphoides indica (L.) Kuntze, Myriophyllum aquaticum (Vell.) Verdc., Eichhornia crassipes (Mart.) Solms, Sagittaria montevidensis Cham. & Schltdl., and several species of Persicaria. Lentic environments occur in areas where water stagnates and does not fl ow, or does so very poorly, as a result of geomorphological conditions. Th ese include the lagoons and estuaries or areas of permanent inundation which harbour diff erent types of plant communities; free-fl oating vegetation (with species such as Eichhornia crassipes, E. azurea (Sw.) Kunth, Pontederia rotundifolia L.f., Pistia stratiotes L., Azolla spp., Salvinia spp.); half-submerged vegetation with plants that are submerged but not rooted and whose leaves and fl owers are emergent (Myriophyllum aquaticum and Utricularia spp.); and half-submerged, rooted vegetation, with vegetative and reproductive parts of plants primarily above the water surface (Nymphaea spp., Nymphoides indica, Eleocharis spp., Typha domingensis Pers., Th alia geniculata L., Rhynchospora corymbosa (L.) Britton, Schoenoplectus californicus and Cyperus giganteus Vahl). In extreme cases masses of fl oat- ing vegetation in still waters become impounded, forming fl oating islands of aquatic species associations which go through various stages of evolution, depending on the amount of substrate they retain. Th us, in the more advanced stages, rooted species can be found in a thick fl oating substrate that resembles soil.
Vegetation subject to periodic fl ooding includes hydromorphic savannahs and hygrophilous (riparian) forests. Th e vascular plant species composition of hydromorphic savannahs varies according to soil type. Palm savannahs are found on soils with a high content of clay (up to 30%) and salts, especially chlorides; the dominant species is the palm Copernicia alba Morong, sometimes associated with scattered trees of Aspidosperma quebracho-blanco Schltdl. and Astronium balansae Engl., while the understory is dominated by marshy species; common plants include various grasses and sedges, Ludwigia, Persicaria and Ruellia. In the palaeobasins of the Río Parana, where the soils are sandy, the landscape is dominated by grasslands of Elionurus muticus and Schizachyrium spp., sometimes with the presence of scattered woody species such as Cecropia pachystachya Trécul and Enterolobium contortisiliquum (Vell.) Morong.
Riparian forests are directly or indirectly associated with water, as they are subjected to periodic fl ooding or waterlogging at certain times of year; these can be found along the edges of rivers, streams and lakes, or forming islands of forests surrounded by wetlands and fl oodplains. Th e edges of these forests include hygrophilous species such as Croton urucurana Baill., Microlobius foetidus (Jacq.) M.Sousa & G.Andrade subsp. paraguensis (Benth.) M.Sousa & G.Andrade, Sapium haematospermum Müll. Arg., Sebastiania brasiliensis Spreng., Guadua sp., Chusquea ramossisima Lindm., Inga vera Willd. and Enterolobium contortisiliquum. Th e understory is dominated by Bromelia balansae Mez and there are a number of epiphytic ferns and fl owering plants. As soil depth increases, the forests change from purely riparian to humid semi-deciduous, characterized by 2 to 4 layers of vegetatio n and a maximum canopy height of about 25 m. Th e dominant species in the tree layer are Handroanthus heptaphyllus (Vell.) Mattos, Peltophorum dubium (Spreng.) Taub., Syagrus romanzoffi ana (Cham.) Glassman, Gleditsia amorphoides (Griseb.) Taub., Luehea divaricata Mart., Holocalyx balansae Micheli and species of fi gs and Lauraceae (Acevedo et al. 1990;Vogt and Mereles 2005). Th ese patches of forest are similar to more extensive interior Atlantic forest found in the Oriental region, now very limited in extent (Huang et al. 2009).
Although the wetlands and forests of Ñeembucú comprise physical features and species composition that are similar to the humid Chaco, such that they are regarded as intrusions of Chaco vegetation in the Oriental region (Mereles 1993(Mereles , 2004, the sandy layer which emerges in many parts of the department results in the development of more diverse and transitional habitats; consequently, the vegetation Ñeembucú is a mosaic of species typical of both the Eastern and Western (Chaco) regions (Mereles 2004). Spichiger et al. (1995) described the tree fl ora of Ñeembucú as "a most interesting boundary zone between the Chaquenian, the Palm-Savannas, the Residual Pleistocenic Dry Seasonal, and the Paranean Floras", i.e., an ecotone between dry forests, wet forests and savannah. those genera recorded as sp. here) prior to our studies. Our collecting in the region (see below) resulted in signifi cant novelty, and the checklist presented here is a fi rst step in documenting the relatively understudied plant diversity of Ñeembucú.

Materials and methods
In assembling the checklist we revised and re-determined all historical and recent collections from Ñeembucú held in the Natural History Museum (BM) and the Facultad de Ciencias Químicas of the Universidad Nacional de Asunción (FCQ). We also reviewed the recent monographic literature for collection records from Ñeembucú, and where we have not seen a specimen of a taxon cited in these sources we include the relevant literature citation, including the page. We also include identifi ed specimens from Ñeembucú cited in TROPICOS (http://www.tropicos.org/) and in the database of the Botanical Garden of Geneva (http://www.ville-ge.ch/musinfo/bd/cjb/fdp/). For those records for which we have examined a specimen we only cite a single voucher, other specimens seen and additional literature citations are not included here.
Flowering plant family circumscription follows APG III (Chase et al. 2009) and the pteridophyte classifi cation follows Smith et al. (2006) as modifi ed by Christenhusz et al. (2011). Families are sorted alphabetically and genera are sorted alphabetically within families. For each taxon found in the Department, we present the accepted name, synonyms, habit, introduced status (all species are native except where indicated), general distribution in Paraguay and one voucher specimen (if available). We use infraspecifi c names only in the cases where taxa other than or additional to the typical occur. Th ose taxa cited to the level of genus only may represent new species or new records for the department, but we were unable to identify them to the specifi c level. Synonymy follows Zuloaga et al. (2008) and TROPICOS (http:// www.tropicos.org/) except for Myrtaceae, where we followed the World Checklist of Myrtaceae ) and for Inga (Fabaceae) where we followed Pennington (1997). For some very common weedy species with extensive worldwide synonymy we have not cited all synonyms; these can be found in Zuloaga et al. (2008) and TROPICOS (http://www.tropicos.org/). We also cite commonly encountered illegitimate names and names not validly published in the synonymy, with indications as to their status. Herbarium acronyms used in the list follow Index Herbariorum (Holmgren et al. 1990, available on-line at http://sciweb.nybg.org/science2/ IndexHerbariorum.asp).
New reports of taxa for the department of Ñeembucú are marked with an arrowhead (►), those taxa not cited in Zuloaga et al. (2008) or the on-line updated version of the Southern Cone checklist (Flora del Conosur 2009) for Ñeembucú but recorded in other publications or databases (the URL or bibliographic reference of each source given with the voucher specimen cited) are marked with an asterisk (*) and those that have not been cited previously as occurring in Paraguay are indicated with a circle (•).

Data resources
Th e occurrence data underpinning the analysis have been uploaded as a Darwin Core Archive (DwC-A), to the Global Biodiversity Information Facility (GBIF) via the Pensoft Data Hosting Center at the GBIF's Integrated Publishing Toolkit (IPT) (http:// ipt.pensoft.net/ipt/resource.do?r=neembucu).
In addition, three Excel spreadsheets containing the taxon checklist, the habitat description and the departmental distribution in Paraguay, generated from the original MS Word manuscript fi le (Remsen et al. 2012), are published as Appendix to the present paper and are available under doi: 10.3897/phytokeys.9.2279.app.

Results and discussion
Our checklist for Ñeembucú records 676 taxa in 374 genera in 100 families (8 families of ferns and fern allies). A total of 439 taxa not previously recorded for the department are included here; 254 of these are new additions for the department resulting from our studies (marked ►), 171 (marked *) have been cited in other sources but not in Zuloaga et al. (2008), and 4 taxa (marked •) have not been cited previously as occurring in Paraguay. In total this represents a more than tripling (676 versus 254, >300%) in vascular plant records for Ñeembucú over the most recent complete published compilation of distributional records for the department , including updates online in Flora del Conosur 2009).
Nine families have more than 20 taxa in Ñeembucú (Table 1). As one might expect for an area that is in part dominated by wetlands and grasslands, Poaceae and Cyperaceae feature prominently. Legumes (Fabaceae), composites (Asteraceae) and Malvaceae are the most taxon-rich families of eudicots and are represented by a large number of herbaceous taxa common to open habitats in the region. Herbs (including aquatic herbs) are the commonest habit class (Table 2) and are the most common new Table 1. Taxon-rich families in the fl ora of Ñeembucú. Poaceae  59  Fabaceae  50  Asteraceae  37  Cyperaceae  36  Malvaceae  28  Euphorbiaceae  24  Solanaceae  24  Verbenaceae  22  Rubiaceae  20  Myrtaceae  19 records for Ñeembucú recorded here. We suggest this is a result of the emphasis on trees in general collections for evaluation of habitats for conservation priorities (with the exception of Vogt and Mereles 2005). Future collecting in Ñeembucú should concentrate on all habit categories as all are represented by signifi cant novelty with half or more than half of the records being new to the department; herbaceous plants, including epiphytes and aquatics will be particularly promising (e.g., see Table 2). Priority setting in global biodiversity conservation is one way to target eff orts to safeguard habitats, species and genes, all tasks required of countries signatory to the Convention on Biological Diversity (CBD). Approaches to priority setting are quite variable -ranging from just personal interest, to taxon based approaches such as the Important Bird Areas (IBAs; ) and Endemic Bird Areas (EBAs; Stattersfi eld et al. 1998) or the Centres of Plant Diversity (Davis et al. 1995), to "hotspot" approaches (Myers et al. 2000), "megadiversity-country" approaches (Mittermeier and Werner 1990), ecoregional priority setting techniques (Dinerstein et al. 1995) and complementaritybased approaches (Margules et al. 2002). Species richness and endemism have been considered important by some, while others have focused more on the conservation of representative habitats or ecosystems. It is clear that multiple indices are more appropriate than a one-size-fi ts-all approach (Orme et al. 2005).

Family Number of taxa
Th e mosaic of wetland and shrubland habitats of Ñeembucú do not feature as a "hotspot" in analyses using the combined richness and endemism criteria of Myers et al. (2000), nor is the area designated a priority using the ecosystems approach of Dinerstein et al. (1995). Th e status of the adjacent humid Chaco in the latter publication is "locally outstanding"; does this mean then that these regions are thus not important for conservation at a regional or global scale? Although part of the Oriental region of Paraguay, Ñeembucú combines many diff erent fl oristic elements (Mereles 1993(Mereles , 2004, making it of interest for analysis of relationships between habitat types in southern South America. Th e wetlands of Ñeembucú can be seen as the southernmost extension of the Pantanal, as they are connected along the drainage basin of the Río Paraguay (see Swarts 2000). Drainage of land for soybean production has not yet been an important factor in Ñeembucú, but the importance of ranching cannot be  Spichiger et al. 5215 (cited in Ramella 2008: 56). Kunth, Nov. Gen. Sp. (quarto ed.) Ezcurra, 1993: 834).      Peña-Chocarro et al. 2283 (BM, CTES, FCQ, G, MO, PY, SI). Note: Th is taxon is treated as Sebastiania by Melo (2006) and Athiê de Souza (2011), but the combination has not yet been published; it was treated as Sebastiania brasiliensis by Zuloaga et al. (2008), but that species is confi ned to coastal Brazil (Athiê de Souza, pers. comm Epling and Játiva 1966: 258). Briq., Bull. Herb. Boissier sér. 2, 7: 606. 1907 Paraguay: Central, Cordillera, Guairá, Ñeembucú, Paraguarí, Presidente Hayes. Voucher: M. Peña-Chocarro et al. 2236 (BM, FCQ). Cristóbal, Opera Lilloana 4: 126. 1960 funded our initial studies (Information incentives for CBD implementation in private reserves in Argentina and Paraguay, ref. 12011 -2003Paraguay, ref. 12011 - -2006 in the humid Chaco region of Paraguay, the National Science Foundation's Planetary Biodiversity Inventory program funded SK's work on Solanaceae (PBI Solanum: a worldwide treatment, DEB-0316614), SK's editing of the manuscript for the parsing process was partially funded by the FP7 project ViBRANT (Virtual Biodiversity Research and Access Network for Taxonomy, http://vbrant.eu).