Comunidades de besouros rola-bostas (coleoptera: Scarabaeinae): do macro a ecologia de indivíduos
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2019-03-26
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Universidade Federal de Goiás
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The study of diversity patterns has generated many hypotheses, which have been often seen as rivals. However, biodiversity is a complex phenomenon and the result of the effects of multiple drivers acting at the same time, effects that may vary in space. The variance of the complex array of drivers that explain local diversity is important to understand the geographic differences in the effects of land use changes. These drivers act as different filters to the establishment and survival of species populations, changing the composition and structure of the community. They may also filter different individual traits, thus altering the functional structure of the community. We defined three main questions: (1) which are the main drivers of local dung beetle species richness in the Neotropics; (2) whether the relative importance of these drivers varies geographically; (3) and how does the time since land use change affect the functional aspects of the community.
For the first question, we constructed a database with published literature on dung beetle communities, to extract information on species richness, abundance, type of bait, type of habitat and sampling effort (as hours/pitfall). We used a multi-hypothesis approach to understand which set of hypotheses better-explained dung beetle species richness at a local scale. Specifically, we used environmental variables to account for six hypotheses: productivity, water–energy, ambient energy, habitat heterogeneity, climatic heterogeneity, and resource heterogeneity, plus a seventh neutral hypothesis described using only spatial data. For the second question, we compiled data from standardized surveys based on pitfall traps, and estimated species richness at each locality using sample coverage estimators. We assessed the relationhips between several predictors (including climate, habitat and mammal diversity) and species richness, and also between them, by means of geographically weighted structural equation mixed models. And for the third question, we conducted standardized surveys of dung beetle communities in seven forest fragments and adjacent pastures at two different regions pertaining to the Atlantic forest (Itajaí Valley) and the Cerrado (Goiânia region) biomes, using pitfall traps baited with human and cow dung, and rotten liver. We measured fourteen traits in individuals collected in each type of habitat at each particular site. And then we calculated the functional richness, functional evenness, functional divergence and community-weighted mean of traits for each area, and analyzed the individual variation through Trait Statistics.
We found that Dung Beetle local richness is a result of productivity (by energy and water) and Heterogeneity (both habitat and resource). The analysis of the variables allows to interpret that the “more-individuals hypothesis” is the main mechanism driving dung beetle diversity, through the importance of abundance. This importance is common to all the Neotropics, but the factors that affect abundance vary between regions. Dung beetle diversity presents geographical heterogeneity in the responses to the factors where we can observe three regions: Mesoamerica, Amazonian, and Subtropical South America. Also, Mammal diversity had contributed to dung beetle diversity and abundance differently, mainly as a consequence of the conversion of forest to pastures. The forest–pasture conversion affected dung beetle functional diversity, where the pasture presented lower functional richness in both regions. But the species pool had a greater effect than time for the reduction of the effect of this conversion. The difference in the species pool also reflects in the trait’s individual variance. While in the Atlantic Forest the filtering occurs at the species level, in the Cerrado it occurs at the individual level in some traits.
Understanding that biodiversity is a complex phenomenon, we suggest to take this in account and use not only a multi-hypothesis approach to study its drivers, but also to consider the spatial variance of this relations. For future works with dung beetles would be interesting to understand the historical and evolutionary events that not only shape species diversity, but also filter dung beetle traits at the species or individual level.
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PESSÔA, M. B. Comunidades de besouros rola-bostas (coleoptera: Scarabaeinae): do macro a ecologia de indivíduos. 2019. 253 f. Tese (Dourado em Ecologia e Evolução) - Universidade Federal de Goiás, Goiânia, 2019.