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Brazilian Journal of Biology

Print version ISSN 1519-6984

Braz. J. Biol. vol.71 no.2 São Carlos May 2011

 

Beetles diversity as a function of different environments

 

 

The authors related the diversity of the families and morph-species of beetles (Coleoptera) in environments of greater diversity of plants. The study was realized between October 2004 and October 2005, at the Centro de Pesquisas de Florestas e Conservação do Solo da Fundação Estadual de Pesquisa Agropecuária (FEPAGRO), Santa Maria, RS, which was published in Brazilian Journal of Biology, in june 2011.

Five quarterly collections were made in five different environments:  native grassland, degraded area (reject) with almost none vegetation, a 15-years-old Pinus elliottii plantation, a 30-years-old Eucalyptus saligna plantation and native forest. The beetles were collected with "pitfall traps". In all environments it was sampled eight collect points. The traps were installed in straight line with 15 m of distance from each other and 15 m of distance from the fragment border. The insects were separated and quantified at the family level and morph-species level. The diversity analysis among the ecosystems were evaluated by the Shannon-Wiener and Simpson indexes.

A total of 1812 individuals were collected, attributed to 45 morph-species and 14 families. The higher richness and abundance were observed in the environment with greater diversity of plants, the native forest (31 species and 782 individuals) and the lower richness and abundance in degraded area (14 species, 86 individuals). Considering all environments, Nitidulidae was the most abundant family and Scarabaeidae was the richest one. However, in native forest, Scarabaeidae and Carabidae had the same number of morph-species than Nitidulidae and in native grassland, Scarabaeidae was the richer family and Staphylinidae was the most abundant family.

At the 14 sampled families, four have an exclusively carnivorous habit, three are herbivores, two are herbivores or detritivore, one is fungivores or detritivore, one is fungivores or herbivore and three possess varied habits. There was a decrease in the number of the new species of beetles captured in each sample period.

According to Shannon-Wiener index, the degraded area had smaller diversity in relation to the native forest, E. saligna and P. elliotii plantations. None difference in diversity between evaluated areas were found to the Simpson diversity index. The most dominance was in the degraded area. The correlation between the total number of morph-species captured was not different to the degraded area and the P. elliottii monoculture and the correlation between the total individuals number was not significant between native forest and native grassland and between degraded area and other sites. The greatest similarity to the organism composition occurred between P. elliottii plantation and E. saligna plantation, presenting 74% of overlap.

The greater coleopterans richness and coleopterans abundance in forest is related to the benefits obtained by these organisms from the soil moisture and microclimate stability offered by forests. This environment provides to the beetles greater diversity of food, more stable microclimate, higher humidity and greater quantity of refuges against predators. The low availability of food resources and to the decrease of soil moisture in degraded area may have contributed to reduce the richness and abundance in this site. The high dominance of beetle species in degraded area can be related to the lower diversity of plants and the high compression of the first centimeters of soil in that area, damaging the animals that move among its particles.

The abundance of Nitidulidae on study areas is due to its distribution in diverse ecosystems. Scarabaeidae are important in organic matter recycling and in the seed dispersals. The morph-species composition and dominance among the sites changed and these differences reflect the different environmental requirements of the group based in the ecosystem structure and plant composition. The results show that the abundance and richness of beetles in the studied environments seems to depend not only on the composition and on plant structure, but on the quantity of plant product in each ecosystem.

The similarity in the composition of Coleoptera species between E. saligna and P. elliottii plantations can be related to its vegetable physiognomies characterized by structural homogeneity. Moreover, the smaller similarity between native grassland and native forest should reflect differences in floristic composition and vertical structure of these ecosystems. The abundance of beetles found in E. saligna plantation may be associated to the ecological plasticity of some species (Butterfield et al 1995) and to the amount of litter in this area, originated from the great sub-forest presence. However, the richness in E. saligna plantation is lower that native area and native grassland. This result may have reflected the low nutritional quality of soil and a discontinuous canopy in E. saligna plantation, besides the high concentration of essential oils in its leaves.

The structural diversity of the vegetation is highly correlated to the diversity of arthropods, and it is used in the understanding of the disturbances caused by the simplifications of the natural ecosystems. Generally, the changes in abundance, diversity and composition of indicative species that depend on particular resources of the system may evaluate and explain the results of disturbance. Biological diversity, in particular, is one of the most important tools in monitoring of health and functioning of ecosystems.

 

 

Contato: Camila Kurzmann Fagundes
e-mail:  milakurzmann@yahoo.com.br

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