Long-term effects of forest fragmentation on Amazonian ant communities

Aim: To analyse the effects of forest fragmentation on ant communities in an Amazonian landscape that has been fragmented for over a century. Location: The region surrounding the village of Alter do Chão in the Brazilian Amazonian state of Pará (2°30' S, 54°57' W). Methods: Collection of ants and measurements of tree density were performed along transects established in eight sites in continuous forest and in 24 forest fragments surrounded by savanna vegetation. Data on size, perimeter, and degree of isolation (distance to continuous forest and distance to nearest area of forest > 5 ha) of each fragment were obtained from a georeferenced Landsat image of the study area. Results: There were significant differences in species richness and composition between fragments and continuous forest, and these differences were not related to intersite variation in vegetation structure (tree density). Fragments supported fewer ant species per plot, and these species tended to represent a nested subset of those found in continuous forests. Fragments had significantly fewer rare species and fewer ant genera. However, fragments and continuous forest had similar numbers of species that also occur in the savanna matrix (i.e. that are not forest specialists). Multiple linear regression analyses indicated that species richness and composition in the fragments are significantly affected by fragment area, but not by fragment shape and degree of isolation. More species were found in larger fragments. Main conclusions: Forest fragmentation influences the organization of ant communities in Amazonian savanna/forest landscapes. Forest fragments harboured, on average, 85% of the species found in continuous forest. That these fragments, despite their long history of isolation, support a relatively large complement of the species found in continuous forest is surprising, especially given that in some recently fragmented landscapes the proportion of species surviving in the fragments is lower. Differences in inter-fragment distance and type of matrix between Alter do Chão and these other landscapes may be involved. The fact that fragments at Alter do Chão are surrounded by a natural (rather than an anthropogenic) habitat, and that most of them are less than 300 m from another forest area, may have helped to ameliorate the adverse effects of forest fragmentation. Keywords Amazon forest, ants, area effects, distance effects, habitat fragmentation, shape effects. © 2006 The Authors

Seletividade dos herbicidas setoxidim, isoxaflutol e bentazon a espécies arbóreas nativas Selectivity of the herbicides sethoxydim, isoxaflutole and bentazon on native tree species

O objetivo deste trabalho foi avaliar a sensibilidade de espécies nativas usadas em recuperação de áreas degradadas aos herbicidas setoxidim, isoxaflutol e bentazon. As espécies estudadas foram Senna multijuga, Guazuma ulmifolia e Croton urucurana. Os tratamentos de herbicida consistiram de uma testemunha (sem aplicação) e aplicação de um quarto, metade, uma vez, duas vezes e quatro vezes a dose recomendada. As doses recomendadas são 184 g ha-1 de setoxidim, 37,5 g ha-1 de isoxaflutol e 720 g ha-1 de bentazon. Avaliaram-se os sintomas de fitotoxicidade, crescimento em altura, acréscimo no número de folhas e massa de matéria seca de folhas. Em outros experimentos, as doses recomendadas dos mesmos herbicidas foram aplicadas em outras 22 espécies arbóreas nativas, nas quais avaliou-se a massa de matéria seca de folhas. O delineamento experimental dos experimentos foi o inteiramente casualizado, com quatro repetições. Cada parcela experimental se constituiu de uma muda em estádio inicial de desenvolvimento. Os herbicidas não provocaram a morte das mudas, embora todas tenham apresentado sintomas de fitotoxicidade. A aplicação de isoxaflutol reduziu a massa de matéria seca das folhas em 20% das espécies, a aplicação de bentazon, em uma espécie, e a aplicação de setoxidim não reduziu a massa de matéria seca das folhas de nenhuma espécie.<br>The objective of this work was to evaluate the sensitivity of native tree species used in the recovery of degraded land to the herbicides sethoxydim, isoxaflutole and bentazon. The species studied were Senna multijuga, Guazuma ulmifolia and Croton urucurana, and the treatment applied comprised one control sample (no herbicides were applied) and the application of the herbicides at one fourth, half, one, two and fourfold the recommended dose (sethoxydim: 184 g ha-1, isoxaflutole: 37.5 g ha-1, bentazon: 720 g ha-1). Phytotoxicity symptoms, growth in length, increase in leaf number, and leaf dry mass were evaluated. In another experiments, the recommended doses of the same herbicides were applied to other 22 native tree species, for which the leaf dry mass was evaluated. The experiments were carried out in completely randomized design with four replicates. Each experimental plot comprised one sapling in initial developmental stage. The herbicides did not cause saplings death, even though all of them showed phytotoxicity symptoms. Herbicide application reduced the leaf dry mass as follows: isoxaflutole, 20% of the species; bentazon, one of the species; and sethoxydim did not reduce leaf dry mass in any of the species

Haematological characteristics of Brazilian Teleosts: III. Parameters of the hybrid tambacu (Piaractus mesopotamicus Holmberg x Colossoma macropomum Cuvier) (Osteichthyes, Characidae)

Fifty six specimens of the hybrid "tambacu" (Piaractus mesopotamicus Holmberg, 1887 male x Colossoma macropomum Cuvier, 1818 female) were collected from fishfarm of Guariba, São Paulo, to evaluate their haematology. Fishes presented 400.0 to 3,100.0 g total weight and 20.0 to 52.0 cm total length. Haemoglobin, haematocrit, mean corpuscular haemoglobin content (MCHC) and percentage of defense blood cells including leucocytes and thrombocytes, were studied. Statistical analysis showed positive correlation (P<0.01) between haematocrit, MCHC and haemoglobin rate. Nevertheless, thrombocytes and lymphocytes showed negative correlation (P<0.01)