Biogeographic analysis and key to the genera of ferns and lycophytes of Mburucuyá National Park , Corrientes , Argentina

The diversity of ferns and lycophytes of Corrientes province, Argentina is not well understood. Our fi eld work in the Mburucuyá National Park in Corrientes province as well as a literature review fi nds 29 genera and 48 infrageneric taxa of ferns and lycophytes for this Park. A comparison of the Park’s species diversity with other protected areas in northeastern Argentina using Jaccard’s similarity coeffi cient and the infrageneric taxa biodiversity index proposed by Squeo et al. (1998) are analized. A key to the Park’s ferns and lycophytes genera is provided.


INTRODUCTION
In tropical woodlands, ferns are often present at or above eye level.In arid areas or on newly exposed surfaces such as burns, clearcuts or landslides, fer ns can be present and sometimes are the dominant vegetation (Sharpe et al. 2010).Some species possess high reproductive and dispersal capacities; if appropriate conditions are present, they may become invasive (Caluff & Fiallo 2008).
Ther e ar e few studies of the fer n (monilophytes, sensu Pr yer et al. 2004), and lycophyte flora of nor theastern Argentina.The synopsis of these groups for the Cuña Pirú Reser ve from the province of Misiones (Márquez et al. 2006) is the only study available for this part of Argentina.There are few other fern and lycophyte inventories for Misiones ( The Mburucuyá National Park (N.P.) in Cor rientes, Argentina, was established on June 27 th , 2001, by an Argentinian National Law 25447.This Park, with an area of 176.80 km 2 , was originally two ranches, Santa Teresa and Santa María; whose owner, Troels Myndel Pedersen, donated them to the Argentinian government in 1991, with the explicit objective of establishing a national park.Pedersen (1992) compiled a fl oristic inventory of the park based on more than 40 years of botanical collections.This inventor y included 28 genera and 43 infrageneric taxa of ferns and lycophytes, two were exotic and only one species was considered endemic.Novelties to this fern fl ora have been documented in Macluf et al. (2010), Meza-Torres et al. (2006,2008), and Meza-Torres (2011).
According to Cabrera (1971), the area is an ecotone with elements from Paranaense, Chaco and Espinal phytogeographical provinces.Saibene & Montanelli (1997) mapped the park's woody plant communities, and recognized the following units: hygrophilous forest; subxerophytic forest; Guadua chacoensis bamboo for est, "Tacuaral"; C o p e r n i c i a alba palm forest ("Caranday" palm forest); Schinopsis balansae forest; Prosopis af finis forest, "Espinillo" forest; and the Yatay palm grove.The presence of marshes and ponds contribute to the area's diverse wetland vegetation.This array of plant communities explains the region's fl oristic richness, with 1383 species; of which 933 are Dicotyledons and 407 are Monocotyledons (Arbo 2004), this represents over half of the species recorded for the entire province (Zuloaga et al. 1999).In the Copernicia alba palm forest, Schinopsis balansae forest, Prosopis affi nis forest, and Yatay palm grove, periodic controlled burning is conducted to reduce fuel build-up, which decreases the likelihood of serious wildfi res, and curbs the proliferation of shrubs in grasslands.
In 2003, researchers from the Instituto de Botánica del Nordeste initiated a project to study the Flora of Mburucuyá N. P. because Corrientes province's ferns and lycophytes were not well studied, one of the aims of the project was to sur vey the area's ferns and lycophytes, as well as develop descriptions and keys for the genera.
The aims of this paper are: 1) to provide a key of the fern and lycophyte genera growing in Mburucuyá N. P.; 2) to estimate the diversity of these plant groups and, 3) to compare species diversity of the park with other near by protected areas (Iberá macrosystem in Corrientes, the Valle del Arroyo Cuñá Pirú Reserve, Guaraní Multiple Uses Reserve, and Teyú Cuaré Provincial Park, from the province of Misiones).These protected areas were selected because they are the ones closest to Mburucuyá N. P. for which there are studies available.

Study area
Mburucuyá N. P. is 176.80 km 2 in area, located in the province of Corrientes (27º58'-26º05'S, 57º59'-58º08'W), about 150 km SE of Corrientes city (Fig. 1).The land is in the NE part of Mburucuyá Department, delineated by Santa Lucía wetlands to the south and Fragosa Ravine to the north.The park is crossed by the westeast running Nº 86 road, which connects Mburucuyá and Palmar Grande.The climate in Mburucuyá N. P. is warm subtropical, with a low annual thermal amplitude.Average annual rainfall is 1300 mm, decreasing from northeast to southwest, and is almost evenly distributed throughout the year; although with a low decrease in summer and a more marked decrease in winter.Fall and winter are the wettest and driest seasons.Mean annual temperature in the period from 1961-1990 was between 21°-23°C (Pedersen, ined.).Between 1980 and 1981, mean annual humidity was 75.9 % (http://www.patrimonionatural.com).

Systematic assignment
We analyzed the historical specimens of the Pedersen herbarium, which are deposited in the CTES Herbarium, as well as the most recent collections of E.I. Meza-Torres from the study area.As there is no consensus among taxonomists in delimitation of ferns and lycophyte families, the present contribution provides results only at the genus level, and does not include family treatment (Keller et al. 2011).Genera nomenclature follows Smith et al. (2006).

Analysis of fl oristic diversity
Nomenclature of biogeographic areas follows Cabrera (1971) and Cabrera & Willink (1980).We constructed a presence (1) -absence (0) qualitative matrix of infrageneric taxa for the biogeographic areas (Appendix 2).According to Squeo et al. (1998), the number of taxa depends logarithmically on the sampling area and taxonomic biodiversity (B) is calculated as B = n i /ln A i, where n i is the number of taxa (species = Bsp) and ln is the natural logarithm of the sampling unit area in km 2

RESULTS
Twenty nine genera and 48 infrageneric taxa were recorded in the Park, from which 53 % of species were found in the hygrophilous forest (Fig. 2).Amphibious vegetation represents 25 % of the species.The Yatay palm grove has 14 % of the species.The lower numbers of species occupy Subxerophytic forest (4 %), Schinopsis balansae forest (2 %), and Prosopis affi nis forest (2 %).
A key to the genera of ferns and lycophytes is shown in Appendix 1.
Regarding to habitat substrate preferences, 52 % of the species have a terrestrial habit (Fig. 3), whereas only 23 % of the species are aquatic.Epiphytic ferns are an important group within the park, as they represent the 19 % of the species, to this value 6 % must be added for the facultative epiphytic species, Phlebodium aureum (L.)J. Sm. and Psilotum nudum (L) P.Beauv.

Biodiversity and similarity indices
Except for Iberá (Bsp = 4.7), the Biodiversity Index of N. Mburucuyá (Bsp = 9.1) was lower than other surrounding protected areas (Table 1).
The results of the Jaccard's similarity index (Table 2) for the different areas showed that the Mburucuya N. P. shares the most similarity with Iberá R. (I j = 0.44), while the lowest similarity occurs with Teyú Cuaré P. P. (I j = 0.20).Comparison of the number of genera, number of infrageneric taxa, indexes of diversity (biodiversity of infrageneric taxa = Bsp) and area of the protected areas studied in the northeast Argentina.

DISCUSSION
The genus Thelypteris Schmidel with five species (10.41 % of the park's fer n and lycophyte flora) is most species rich genus in the Park, followed by Pecluma M.G.Price, with four species (8.33 %), and Doryopteris J. Sm. and Ophioglossum L. with three species each (6.25 %), whereas two infrageneric taxa were recorded for Adiantopsis Fée, Anemia Sw., Asplenium L., Azolla Lam., Pityrogramma L., Pleopeltis Willd., and Salvinia Ség.(4.16 %) (Fig. 4).The other genera are represented by only one species each (2.08 %).Among the 48 species, only two are exotic, Macrothelypteris torresiana (Gaudich.)Ching and Thelypteris dentata (Forssk.)E.P. St. John (Ponce 1987); these fer ns are considered weeds by Caluf f & Fuentes Fiallo (2008).Pedersen (1992) reported the presence of M. torresiana at only two sites within the park, and one site for T. dentata, these three sites are about 4 km northwest of the Santa Teresa Ranch.recent collections, (2007), T. dentata expanded its distribution southward, up to 2 km south of Santa Teresa Ranch.Macrothelypteris torresiana grows within the Santa Maria Ranch, to 9 km west of the sites previously reported by Pedersen (1992).Was obser ved that T. dentata invaded old abandoned houses that were absorbed by the forest.Macrothelypteris torresiana has invaded artifi cial streams and moved into the forest.Fortunately, both species are not as highly invasive, as was obser ved (Keller pers. com. 2008)  Compared with nearby protected areas (Table 1), Mburucuyá N. P. (with 29 genera) has a higher genera richness than Cuña Pirú Reserve (28 genera) and Teyú Cuaré Provincial Park (25 genera).However, Guaraní Multiple Use Reser ve exhibits the highest species richness, with 80 infrageneric taxa of ferns and lychophytes grouped into 38 genera.As it was expected, the three protected areas of Misiones presented the highest biodiversity indices at genus and species levels; these results agree with fi ndings of Cabrera (1971), since the entire Misiones province is infl uenced by the Amazon phytogeographic domain, characterized by a high species richness of ferns.Indeed, Teyú Cuaré Provincial Park is a particular biogeographic area, with Amazonian elements of the Paranaense and Cer rado phytogeographic provinces, represented by species such as Trichomanes pilosum Raddi and Elaphoglossum pachydermum (Fée) T. Moore (Biganzoli & Múlgura de Romero 2004).Another Matrix representing the similarity (I J ) of the composition of infrageneric taxa of ferns and lycophytes between the different protected areas.

Mburucuyá
Cuñá Iberá Natural Reserve is also situated in an ecotone, but has relatively low diversity (Bsp = 4.7), probably because most of the reserve area is covered by water and harbours hydrophytic vegetation.For this reason, endemic species are not present in the Mburucuyá N. P. and the Iberá region.
Mburucuyá N. P. has seven species that are not known from the other study areas (Asplenium sellowianum Hieron., Doryopteris lorentzii (Hieron.)Diels, Isoetes pedersenii, Phlebodium aureum, Rumohra adiantiformis (G.Forst.)Ching, Salvinia auriculata Aubl., and Vittaria graminifolia Kaulf.)(Appendix 2).The matrix calculated using Jaccard's similarity indices (Table 2) reveals that Mbur ucuyá N. P. and Iberá Macrosystem show great the number of infrageneric taxa of ferns and lychophytes in the province of Cor rientes amounts to 103.Notably, Mburucuyá N. P., with an area of 176.80 km 2 (about 0.2 % of the area of Corrientes province), harbours about 43.7 % of the fern and lychophyte species known for this political province.Thus, this National Park is critical for the conservation of the provinces fern and lycophyte fl ora.
Further fl oristic studies in Copo National Park, located in the Chaco phytogeographic province, are necessary in order to exclusively Chacoan species can be compared with the areas analyzed in this study.APPENDIX 2 Matrix of taxa used to obtain the similarity index of the fl oristic composition of ferns and lycophytes among the different protected areas from northeast Argentina.Presence (1) -absence (0).Matriz de taxa usada para obtener el índice de similitud de la composición fl orística de helechos y licofi tos entre las diferentes áreas protegidas del nordeste de Argentina.Presencia (1) -ausencia (0).
. The diversity of ferns and lycophytes Mburucuya N. P. were compared with the protected areas in the Iberá macrosystem in Corrientes Province, Valle del Arroyo Cuñá Pirú Reserve, Guaraní Multiple Uses Reserve, Teyú Cuaré Provincial Park, and surrounding areas from the province of Misiones.These protected areas were selected because they are closest to Mburucuyá N. P. for which studies are available.Due to constant transfers genus of the species by advances in taxonomic studies, diversity indices were evaluated only at the species level.The number of taxa and the area of each sampling unit were taken from Arbo & Tressens (2002), Biganzoli & Múlgura de Romero (2004), Márquez et al. (2006), and Tressens et al. (2008).Floristic similarity of infrageneric taxa among the protected areas was estimated with the Jaccard's similarity index (I J ) with the software PAST version 1.75b (Hammer et al. 2001).

TABLE 1
in Misiones province, where M. torresiana colonizes and invades the planted Araucaria angustifolia forest.Controlled burning is periodically conducted in the Copernicia alba palm forest, Schinopsis balansae forest, Prosopis af finis forest, and Yatay palm grove.Native species inhabiting these environments survive the burns because many of these species have rhizomes that help make them fi re resistant (e.g.Adiantopsis chlorophylla (Sw.)Fée, A. tweedieana (Hook.)Link-Pérez & Hickey, Blechnum serrulatum Rich., Pityrogramma trifoliata (L.) R.M. Tryon, Pteridium arachnoideum (Kaulf.)Maxon).An impor tant point to note is that the Mburucuyá N. P. is the type locality for Isoetes pedersenii E.I. Meza & Macluf; there are only two known localities for this species, one into the Park (Macluf et al. 2010), and the other in the Brazilian Pantanal (Pott & Pott 1997).