Vascular Flora of a Cerrado sensu stricto remnant in Pratânia, state of São Paulo, southeastern Brazil

: The Cerrado (Brazilian savanna) has suffered massive destruction in recent years, mainly due to the expansion of agricultural areas. Many remnants of this vegetation are still poorly studied. Therefore, the purpose of this study was to carry out a floristic survey in a remnant of Cerrado in the municipality of Pratânia, central-west region of state of São Paulo, southeastern Brazil. In total, 120 species (38 families, 88 genera) were registered. The families with greater richness were: Fabaceae (23 species), Asteraceae (15), Myrtaceae (10), Malpighiaceae and Rubiaceae (seven each) and Bignoniaceae (five). The shrub component was predominant in the study area representing 37.5 % of the recorded species. A comparison among eight Cerrado areas showed greater similarity between areas with similar altitude.

. Location of study area in Pratânia, state of São Paulo, southeastern Brazil.
mm (Déstro and Campos 2006). The soils are classified as Latosol and Argisol (according to the Brazilian System of Soil Classification, EMBRAPA 1999).
The floristic survey was carried from January to October 2008, on a weekly basis. Approximately 1 ha of the Cerrado sensu stricto area was inventoried and all species in reproductive phase were collected and identified. Voucher specimens were deposited in the Herbarium BOTU (Herbário "Irina Delanova Gemtchújnicov", Instituto de Biociências de Botucatu, UNESP). The floristic similarity was estimated using the Jaccard Index (Mueller-Dombois and Ellenberg 1974) and included the present study and other seven previously published studies on Cerrado sensu lato vegetation performed in São Paulo state. Species with incomplete identification (only genus, aff. or cf.) were excluded as well as those whose occurrence was reported in just one area, according to methodology adopted by Ratter et al. (2003). Only floristic surveys which included all plant habits were compared. A cluster analysis among these eight areas was also performed using the Jaccard Index of Similarity and the UPGMA algorithm for the dendrogram elaboration (Sneath and Sokal 1973).
In the center of the sampled area a 5 x 30 m transect was delimited and every woody plant with stem basal diameter equal or superior to 3 cm was recorded and drawn, in order to make a profile diagram, according to Albuquerque and Rodrigues (2000).

Results and Discussion
A total of 119 species of Angiosperms (37 families, 87 genera) and one pteridophyte were registered (Table 1). Although this number may seem small compared to core Cerrado (see Gottsberger and Silberbauer-Gottsberger 2006), many São Paulo state Cerrado areas have similar species number (see references in Table 2). Gottsberger and Silberbauer-Gottsberger (2006) also quoted these regional variations and provided an extensive discussion about this matter, pointing out that local edaphic condition and climate characteristics may interfere on the floristic composition, contributing to the extreme Cerrado flora heterogeneity.
The most species-rich families were Fabaceae with 23 species in total (10 species on Faboideae, seven on Mimosoideae and 6 on Caesalpinoideae), Asteraceae (15 species), Myrtaceae (10), Malpighiaceae and Rubiaceae (seven species each) and Bignoniaceae (five). These families account for 56 % of the surveyed species. The richest genera were Eugenia (five species), Byrsonima, Miconia, Mimosa and Vernonia (four species each). Among the angiosperms, 20 families and 69 genera had one single species.
Shrubs make up 37.5 % of the inventoried flora, followed by herbs (27.5 %), trees (23 %), and vines (12 %). Among the shrub species, the richest families were Asteraceae and Myrtaceae (seven species each) and Fabaceae (five). Apocynaceae, Dilleniaceae, Erytroxylaceae, Euphorbiaceae, Lamiaceae and Proteaceae showed only one shrub species each. Among the herbs the richest families were: Fabaceae (nine species), Asteraceae (seven) and Rubiaceae (three). Acanthaceae, Amaranthaceae, Commelinaceae, Convolvulaceae, Euphorbiaceae, Lythraceae, Polypodiaceae and Sapotaceae had only one herbaceous species each. The arboreal component had Fabaceae (seven species), Malpighiaceae and Myrtaceae (three species each) as the richest families. Araliaceae, Chrysobalanaceae, Ebenaceae, Malvaceae, Ochnaceae, Salicaceae and Vochysiaceae had only one tree species each. The families with the highest number of vines were Apocynaceae and Bignoniaceae, both with three species each, and Fabaceae with two species. The other families where vines were represented had only one species each (see Table 1). Machado et al. (2005), in an inventory of all Cerrado physiognomies in the same fragment quoted 168 species in total, but there was no indication of the class or classes of physiognomy where the plant species were found. This makes the comparisons difficult. However, it was possible to observe that 66 species were common to our inventory and that 54 species that we found were not collected by Machado et al. (2005), while they quote 102 other species that were not observed by us. These conflicting results are possibly due to the fact that our research was limited to the Cerrado sensu stricto area, while Machado et al. (2005) inventoried all the Cerrado physiognomies. On the other hand, the results highlight the fact that even in a restrict area more species can be found depending on the inventory effort.
The profile diagram of the vegetation (Figure 2) shows the occurrence of a dense woody layer, consisting of trees of small to medium size (three to six m tall), shrubs and sub-shrubs with multiple stems. A low, almost continuous canopy was observed, characterizing a dense Cerrado.
The overall number of species sampled in the eight localities chosen to be compared in relation to floristic similarity (Table 2) was 752. From this total, 431 species were discarded because they occurred in just one location.  The highest similarity index (54 %) was found between the Cerrado areas located in Botucatu Municipality, at altitudes around 500 m ( Table 3). The similarity among the other sites was lower, but there was a trend leading to higher similarity between neighboring areas or between areas with similar altitude. In this category lies the Cerrado of Pratânia (720 m altitude) which was more similar to another Botucatu Cerrado (830 m altitude).
The cluster analysis (Figure 3) show the segregation of three major groups, one including areas of Assis, one including only the area of Pratânia and one area of Botucatu, both with higher altitudes (720 and 830 m, respectively) and other group joined areas with elevations ranging from 500 to 600 m. The higher similarity was observed between Cerrado areas within the same municipality or neighbor  areas (Table 3). These results support the statement that the Cerrado vegetation is extremely variable even in very close locations, as noted before in other Cerrado biome areas (Bridgewater et al. 2004).
The species-richness and the peculiarities of the Cerrado of Pratânia indicate the importance of this fragment as a remnant of the original Cerrado vegetation in the area and may possibly serve as a floristic reference for future conservation measures.