Brazilian Tropical Dry Forest Research Articles

Insect Herbivores and Leaf Damage along Successional and Vertical Gradients in a Tropical Dry Forest

AbstractThe availability and quality of resources for herbivores in tropical dry forests (TDFs) vary in time and space, affecting herbivore guilds differently across spatial scales (both horizontally and vertically), with consequences to the distribution of leaf damage in these forests. We attempted to elucidate the distribution patterns of herbivorous insect guilds and leaf damage throughout the secondary succession and vertical stratification along the rainy season in a Brazilian TDF. With the advance of the succession, a greater richness and abundance of herbivorous insects were found, resulting in higher leaf damage in intermediate and late stages. This pattern, however, was not observed for the frequency of leaf miners. At a smaller spatial scale, the host tree height positively affected the richness and abundance of insects. The higher leaf damage was found in canopy, which also harbored a greater richness and abundance of chewing herbivores compared to the understory at both the beginning and the end of the rainy season. Although for sap‐sucking insects, this was only true at the beginning of the season. We detected a decrease in insect richness and abundance at the end of the rainy season, probably due to a synchronization of insect activity with the availability of young, highly nutritious plant tissues. These results are consistent with other studies that found a general trend of increasing richness and abundance of herbivorous insects and leaf damage throughout the secondary succession (early to late stages) and between vertical strata (understory to canopy), suggesting that forest complexity positively affects herbivores.

Fungal endophytes from cactus Cereus jamacaru in Brazilian tropical dry forest: a first study

Endophytic fungi live within the healthy tissues of plants and can promote host species tolerance to different environmental stresses. However, most studies have been of plants in humid environments, and there are few reports of the benefits of such associations for plants of extreme environments. Our aims were to identify endophytic fungi using morphological taxonomy, to explore richness and estimate species frequency in a cactus, C. jamacaru, in Brazilian tropical dry forest (Caatinga). We thus identified 59 taxa, corresponding to 69.7 % of the total number of isolates; the other 30.3 % were sterile mycelia. Cladosporium cladosporioides and Fusarium oxysporum were the species most commonly isolated, followed by Acremonium implicatum, Aureobasidium pullulans, Trichoderma viride, Chrysonilia sitophila, and Aspergillus flavus. Forty-seven species are recorded for the first time as endophytic fungi of cacti, and 18 others as endophytes for Brazil; this suggests that C. jamacaru harbors a highly diverse fungal community as measured by a diversity index. However, species accumulation curves suggest that our study still underestimates endophyte diversity because it does not provide an exhaustive sample. To our knowledge, this is the first report of endophytic fungi from C. jamacaru in tropical dry forests.

Remarks about biology of Canthon rutilans Laporte, 1840 (Coleoptera: Scarabaeidae) with the first report of perching in a Brazilian Tropical Dry Forest

Remarks about biology of Canthon rutilans Laporte, 1840 (Coleoptera: Scarabaeidae) with the first report of perching in a Brazilian Tropical Dry Forest

Does the edge effect influence plant community structure in a tropical dry forest?

Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m) were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges.

Successional and Seasonal Changes in a Community of Dung Beetles (Coleoptera: Scarabaeinae) in a Brazilian Tropical Dry Forest

We tested the following hypotheses on the dynamics of a dung beetle community in a Brazilian Seasonally Dry Tropical Forest: (1) successional changes of dung beetle community, with species composition, richness and overall abundance increasing with the successional stages; (2) dung beetle community changes between dry and wet seasons, with species composition, richness and abundance decreasing in the dry season. Dung beetles were sampled in 15 plots from three different successional stages in both wet and dry seasons. We sampled a total of 2,752 individuals, representing 38 beetle species and 14 genera. The composition, richness, and abundance of dung beetles changed along the successional gradient and was strongly related to seasonal variation. The highest diversity of dung beetles was found in the intermediate aged forest fragments. These findings highlight the importance of secondary forests to biodiversity conservation and restoration programs in seasonally dry tropical

Sustainability of tropical dry forests: Two case studies in southeastern and central Brazil

In this study, we review the current available information on the social–ecological context of Brazilian tropical dry forests (TDFs), a vegetation type that covers approximately 3% of the country territory. For this purpose, we conducted a comparative analysis of two case studies, one study in the north of Minas Gerais state and the other in Paranã River Basin, situated in southeastern and central Brazil, respectively. We compiled published bibliographical and census-based data for the two regions, concerning the historical human occupation and land use and the environmental and development policies affecting TDF management and sustainable use. Brazilian TDFs usually occur in semi-arid climates, and have been intensely converted mainly to extensive pasturelands in large farms, thus leading to high income concentration in those areas. Our case studies involve less-developed regions that support populations with very low human development indices, which is the norm for Brazilian TDFs. Many of these are traditional populations, such as indigenous and slave descendents, with peculiar cultural practices only recently considered in government policies proposed for the forest management. Though the two regions have similar land use histories, current social–ecological scenarios are very different. In the north of Minas Gerais, TDF conversion policies were debated intensely for the last 15 years, recently resulting in a state law specifically generated to regulate TDF use. Also, this region has 20 conservation units (CUs), some of them delimited inside the territories of the several traditional populations that inhabit TDF areas. This process caused enduring conflicts that can affect both CUs’ effectiveness and the sustenance of these populations. In the Paranã River Basin, there is no specific policy towards TDFs, whose use is regulated by the 43-year-old Brazilian Federal Forest Code. There are only four CUs in this region, and most traditional populations were expelled from their original territories and consequently lost their cultural identity. Government sustainability strategies are limited to the establishment of CUs, a response that may disregard social demands and cultural practices, depending on the local context. Given the uniqueness and threat level to TDFs, specific and more diversified policies towards land use should be established for these ecosystems in order to stimulate low-impact activities that maintain ecosystem services and improve the livelihoods of TDF inhabitants.

A scientific note on the occurrence of Euglossini bees in the Caatinga, a Brazilian tropical dry forest

Euglossini bees (Apidae) are an exclusively Neotropical monophyletic group of five genera (Aglae, Eufriesea, Euglossa, Eulaema, and Exaerete) with 190 species, (Rebelo, 2001; Ramirez, 2005). In Brazil, the second most diverse country in Euglossini species (Ramirez et al., 2002), 80 species are referred for the Amazon, 57 for the Atlantic forest, and 23 for the Cerrado (Rebelo, 2001). Despite this high richness, new species continue to be described (Ramirez, 2005) and known species are still being recorded from new locations (Nemesio and Silveira, 2004). The Caatinga, a semi-arid ecosystem unique from Brazil, is a deciduous forest with scrub vegetation. It occurs in areas of low and highly seasonal rainfall (500–700 mm/year), and covers 800 000 km2 of Brazil’s territory (ca. 8.6%) in the northeastern region (Leal et al., 2003). It was estimated that more than 40% of its plant species relies on bees for pollination (Machado and Lopes, 2004). However, the Caatinga apifauna is still poorly known (Zanella, 2000; Zanella and Martins, 2003). The aim of this paper is to review and report new records of Euglossini bees for the Caatinga region. We inventoried five sites located in the states of Pernambuco (PE) and Ceara (CE), Brazil (see material online) by attracting Euglossini males using odour

Plant Sexual Systems and a Review of the Breeding System Studies in the Caatinga, a Brazilian Tropical Dry Forest

The reproductive biology of a community can provide answers to questions related to the maintenance of the intraspecific pollen flow and reproductive success of populations, sharing and competition for pollinators and also questions on conservation of natural habitats affected by fragmentation processes. This work presents, for the first time, data on the occurrence and frequency of plant sexual systems for Caatinga communities, and a review of the breeding system studies of Caatinga species. The sexual systems of 147 species from 34 families and 91 genera occurring in three Caatinga areas in north-eastern Brazil were analysed and compared with worldwide studies focusing on reproductive biology of different tropical communities. The frequency of hermaphrodite species was 83.0 % (122 species), seven of these (or 4.8 % of the total) being heterostylous. Monoecy occurred in 9.5 % (14) of the species, and andromonoecy in 4.8 % (seven). Only 2.7 % (four) of the species were dioecious. A high percentage of hermaphrodite species was expected and has been reported for other tropical ecosystems. With respect to the breeding system studies with species of the Caatinga, the authors' data for 21 species and an additional 18 species studied by others (n = 39) revealed a high percentage (61.5 %) of obligatory self-incompatibility. Agamospermy was not recorded among the Caatinga studied species. The plant sexual systems in the Caatinga, despite the semi-arid climate, are similar to other tropical dry and wet forest communities, including those with high rainfall levels, except for the much lower percentage of dioecious species. The high frequency of self-incompatible species is similar to that reported for Savanna areas in Brazil, and also for dry (deciduous and semideciduous) and humid tropical forest communities.