Beetles in the Brazilian Semi-arid: Remarkable, but Almost Unknown

Priscila Paixão Lopes

The presence of endangered species, high biodiversity, high rate of endemism or a set of these factors are criteria for the selection of conservation areas. The employment of these criteria frequently results in the protection of a high number of species. Even with the protection of an umbrella species (a target species), many others that inhabit the same area are equally benefited. Whatever criteria are used to select conservation areas, the knowledge of biodiversity is essential. The best way to obtain this knowledge is through systematic surveys of flora and fauna.

Among Brazilian biomes, moist forests, such as the Amazon and the Atlantic Forest , have their biodiversity better known. In general, the knowledge of the fauna in the Semi-arid is very little for both vertebrates (i.e. birds and mammals), which have a higher conservationist appeal, and several groups of invertebrates. Such little understanding has made the delimitation of conservation areas difficult. At first, the main reason to protect areas of caatinga was the need to search for information about its flora and fauna before they were totally destroyed.

The most frequently faunistic inventories used to support the creation of conservation areas are those dealing with diversity of vertebrates. Birds and mammals are often used for both the establishment of target species and as indicator of hotspot areas. Although extremely relevant, the survey of these organisms is expensive and estimates of diversity usually take longer. The survey of insects would be an alternative to assess biodiversity. Insects amount to almost half of the total number of species currently described and are noticeable for their multiple ecological activities in many ecosystems. Thus, insect surveys would provide a more realistic assessment of biodiversity.

Importance of the Coleoptera

Among the insects, the beetles (Order Coleoptera) are the largest group (around 40% of the insects). Concerning the total species of plants and animals, they amount to around 20% of the described species. Considering such a huge diversity, these insects are thought to be the most successful in nature. They present sizes that vary from 1 mm to giants of 15 cm. They are also very important ecologically , having different roles in the environment, acting as pollinators, herbivorous, scavenger, necrophagous or predators.

Present in almost all environments (except sea environments), beetles are different from one another in amazing ways. They are important contributors for the biodiversity of moist forests, arid or semi-arid areas, streams and lakes. It can be said that while the fauna of beetles is not known, the biodiversity of that area is certainly underestimated.

The knowledge of the fauna in the Northeast Brazil is focused on its coastal areas; there are few studies on the Semi-arid. A survey on the current situation of biological research on biodiversity in Brazil has shown a huge absence of studies in the region, mainly in areas of caatinga. Considering taxonomic groups studied, it is clear that the beetles are very little known; no survey work was published for fifteen years. One reason for this gap is the small number of researchers and taxonomists of beetles in the region. Considering the great contribution of these insects to the world biodiversity, this gap needs to be fulfilled as soon as possible. In order to do this, it is necessary to perform surveys of insects, as well as interchange and hosting of taxonomist in the NE Brazil.

Number of publications on several groups of organisms surveyed in Brazil and in the NE Brazil until 2002; numbers above columns are works based on inventories carried out in Brazil (and those in the NE Brazil). Note the scarcity of publications on beetles, particularly in the NE.

Arthropods are excellent indicators when estimating the local diversity . Whereas the survey of vertebrates is expensive and time consuming, the survey of insects is relatively fast and cheaper. Beetles sampled with fly interception and pitfall traps generally present high correlation with the total diversity of the sampled areas, providing a shortcut for biodiversity estimates, and so increasing efficiency in the selection of conservation areas.

Most of the State of Bahia is included in the Semi-arid, which do lack survey of insects (Chapter 15). Such problem was mainly linked to the small number of taxonomists in the NE Brazil , perhaps to the small aesthetic appeal of the regional formations (e.g. physiognomies characterized by dense thorny trees) when compared to the luxuriant humid formations, besides the logistic difficulties to develop studies in this area. The misconception of low diversity of species in the Caatinga has started to be gradually undone from an increasing gathering of scientific information that has revealed high levels of endemism in the caatinga. Knowledge on the insect diversity, however, is still little. From every new sample, new species are discovered. Most of them, however, continue hiding in piles of sample pots due to the lack of specialists able to describe or identify them correctly.

Studies on Beetles in the Brazilian Semi-arid

Recent surveys of insects are being carried out in the Semi-arid. Two studies were carried out in the hydroelectric building of Xingo (states of Alagoas and Sergipe). One explored the abundance of families of Coleoptera and the other the richness of species of Cerambycidae. Ongoing surveys in the Semi-arid of Bahia comprises areas, such as the Chapada Diamantina and the Northwest of the State, linked with PROBIO (MMA) and PPBio of the Semi-arid (MCT, Chapter 2), respectively, and include several physiognomies of caatinga, semideciduous forests, cerrados and campos rupestres. Beetles have been sampled mainly in decomposing medium (carrion and feces); a few generalist species were observed. Among the sampled beetles, the Scarabaeidae (more than 30 species of “rola-bosta”, dung beetles), Nitidulidae, Scolytidae (mostly scavengers), Histeridae (more than 10 species) and Staphylinidae (predators of fly larvae and other little insects, more than 10 species), besides Carabidae, Curculionidae, Tenebrionidae and others are present.

Samples were carried out exclusively through traps with baits. Few traps used only few times a year and for short periods in the field were enough to show that every kind of vegetation presents an important component of habitat specialist species. Vegetations are frequently shaped in a mosaic, following environment nuances. As the vegetation is modified due to variations of the physical environment (humidity, intensity, distribution and seasonal regime of rain; medium and maximum temperatures and kind of soil), the same happens with beetles communities. Such exclusivity of species that end up forming a mosaic of compositions suggests that, in order to optimize the conservation of biodiversity, the protection of a set of environments with complementary biodiversity would be ideal.

Surveys, although restricted in time and space, suggest that the diversification of methods and intensification of sampling will increase significantly the species diversity recorded in the Semi-arid. This information will be able to help on the delimitation of priority areas for conservation and for the comprehension of the features which determine the spatial patterns of diversity, also helping elaborate management plans for these areas.

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