The Aquatic Macrophyte Flora of the Pandeiros River Wildlife Sanctuary , Minas Gerais , Brazil

forests, and several aquatic macrophyte environments, associated with watercourses (Barbosa and Maillard 2010). Even though the need for special attention to preserve the biodiversity in northern Minas Gerais is strongly felt, very few efforts focusing on documenting its floristic diversity have been made so far. The present study aims to contribute to the knowledge of its regional flora, and more specifically, to the study of aquatic macrophytes of the Pandeiros River Wildlife Sanctuary.


Introduction
Aquatic environments correspond to approximately 11% of the continental area of tropical regions (Rebouças et al. 1999).Brazil, with its largest hydrographic network in the world, has a high degree of habitat diversification, representing ecosystems that make up its natural landscape (Bove et al. 2003).However, several aquatic environments have been drained or eliminated in the last decades as a result of the expansion of agricultural activities, industrial development, urbanization, establishment of hydroelectric power reservoirs, and by attempts to eliminate breeding sites of disease vectors (Esteves 1988).These factors have been responsible for the disappearance of numerous habitats and, therefore, the plant diversity associated with them, potentially influencing fundamental ecologic processes, such as the nutrient cycling and primary productivity of water bodies.
The São Francisco forms one of the main Brazilian hydrographic basins with ca.645,000 km2 (7,5% of the country's area), of great social, economic, cultural, and biological relevance (Kohler 2003).Severe anthropic pressure of the last decades, such as the elimination of riparian forests and the transposition of its waters (a project carried out by the National Integration Ministry of the Brazilian Government) have had a negative impact on its biota that can be readily observed at several of its stretches.
The São Francisco rises in Minas Gerais, where several of its medium to large tributaries are found, accounting for more than 70% of its water (Kohler 2003).Some of those are located in the northern part of the state, an ecotonal area between the two important Brazilian biogeographic domains, the Caatinga and the Cerrado.A mosaic of different phyto-physiognomies is found in the region (Lombardi et al. 2005), composed of savannas, deciduous forests (associated with limestone outcrops), riparian Abstract: The São Francisco River forms one of the main Brazilian hydrographic basins of ca.645,000 km2.The Pandeiros River is a tributary situated on the left margin of the São Francisco and is considered a strategic component for conservation of biodiversity of that hydrographic basin.An inventory of the aquatic macrophyte flora of the Pandeiros River Wildlife Sanctuary was carried out, using collections of botanical samples and examination of specimens at the BHCB Herbarium.Aquatic environments in the study area were classified as follows: the Pandeiros riverbed, floodplains, oxbow lakes, and swamps.A total of 101 species was inventoried, distributed in 37 families (1 charophytes, 1 liverworts, 3 ferns and 32 angiosperms) and 71 genera.The species were classified into seven life forms, with the amphibian and rafted plants the more representative.The area shows a high diversity in its aquatic macrophytes and has an important role in the conservation of biodiversity of the region.
The Aquatic Macrophyte Flora of the Pandeiros River Wildlife Sanctuary, Minas Gerais, Brazil range from 16°C to 34°C (with the annual mean around 24°C), while precipitation varies from 850 to 950 mm, with occasional long dry periods (Ratter et al. 1978).The aquatic environments in the study area can be classified as: the Pandeiros riverbed (PAN), floodplains (FLP), oxbow lakes (OXL), and swamps (SWP).Table 1 summarizes some features of these environments.

Data collection
The inventory of aquatic macrophytes of the Pandeiros River Wildlife Sanctuary was carried out during the beginning of the rainy season (September 2007) and the dry season (June 2008) in the area.Transportation for the collection of samples in the environments cited in Table 1 was done by motorboat.Fertile material was prepared in accordance with the usual techniques for collecting aquatic macrophytes (Haynes 1984;Ceska et al. 1986) and the specimens were deposited at the BHCB herbarium (acronym follows Thiers 2012).Additional specimens from the study area previously deposited at the BHCB were also included in the compilation.
For species identification, pertinent literature was studied, including taxonomic treatments and guides, as well as comparison with the BHCB herbarium specimens previously determined by experts.Additionally, duplicates were sent to experts for confirmation and/or identification of some species.The classification of the angiosperm families follows APG III (2009); for ferns, Kramer and Green's (1990) classification is adopted; and for charophytes and liverworts, Raven et al. (1990) is followed.Nomenclatural terminology and author abbreviations are according to Brummit and Powell (1992).The life forms names were adopted in accordance with the classification proposed by Irgang et al. (1984), except for plants growing on organic soil (histosoil) of floating meadows, which are classified as rafted plants, as suggested by Pivari et al. (2011).Data for the type of habitat for each species were obtained from exsiccate labels.
The inventoried species were classified into seven life forms (Table 2), with the prevalence of the amphibians (42 spp.) and rafted plants (27 spp.).The amphibian species were mostly associated with floodplains and borders of oxbow lakes, where the soil is transitional from dry to flooded during the annual hydrological cycle.The species classified as rafted plants were recorded exclusively in oxbow lakes, environments that gather adequate conditions for the establishment of floating meadows (Duzer 2004) as a result of succession of aquatic plants (Pivari et al. 2008) that accumulate large amounts of floating mulch and culminating in the histosoil formation.Such substrate accounts for the occurrence of several aquatic macrophyte species (Pivari et al. 2008;Pivari et al. 2011).Other life forms sampled in the study were characterized as emerging (12 spp.), fixed submerged (7 spp.), free floating (6 spp.), fixed floating (5 spp.) and free submerged (2 spp., each), as in other Brazilian wetlands (Pott and Pott 2000;Pivari et al. 2011).
In the swamps of the Pandeiros River Wildlife Sanctuary were recorded 14 species distributed into all life forms (except rafted plants, since no floating meadows are found in that environment).Some species, such as Azolla filiculoides, Ceratophyllum demersum, Egeria najas, Ludwigia inclinata, and Nymphaea rudgeana, were observed exclusively in the swamps.Different life forms provide for higher heterogeneity of niches in the establishment and maintenance of aquatic fauna by creating refuges for spawning, nesting, and other specific conditions.The floodplains, on the other hand, accounted for 42% of the inventoried aquatic macrophyte species.Parts of these areas are significantly affected by cattle grazing, a common farming activity in the region.Therefore, some typical species of disturbed areas were also sampled, such as Eclipta prostrata, Fuirena umbellata and Ludwigia octovalvis (Lorenzi 2000).

Table 1 .
Aquatic environments of the Pandeiros River Wildlife Sanctuary and their principal features.