Variação fenotípica e estrutura da comunidade de califorídeos (Diptera: Calliphoridae) necrófagos : perspectivas ecológicas e considerações para prática forense

Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-Graduação em Ecologia, 2019.A entomologia forense consiste na interpretação de vestígios entomológicos em casos criminais. Infere-se o intervalo pós-morte com base em características invividuais ou da comunidade de insetos. É importante que os profissionais conheçam o grau de variação dos fenótipos avaliados, bem como os fatores que levam a variação fenotípica e como eles operam. Fatores bióticos e abióticos interferem nos indivíduos levando à variabilidade de tamanhos e formas em insetos e que essas influências estão desigualmente distribuídas entre as espécies e os sexos. Este trabalho investigou como (1) a variação de tamanho e sua resposta à densidade estão estruturadas entre os sexos em três espécies de califorídeos necrófagos; (2) a morfologia alar dessas espécies de califorídeos reage a situações de competição intra- e interespecífica; (3) a comunidade de califorídeos necrófagos e suas variações fenotípicas estão temporalmente e espacialmente estruturadas em uma área ambientalmente protegida no Distrito Federal; e (4) a morfologia alar de duas espécies de califorídeos necrófagos (nativa X exótica) respondem à variação temporal (estação seca x chuvosa) e vegetacional (mata de galeria x campo sujo). O tamanho e a forma das asas de machos e fêmeas são diferentes e reagem de forma diversa ao aumento de densidade, e as três espécies analisadas reagem distintamente à competição interespecífica. A composição da comunidade de califorídeos necrófagos varia em função do tempo e das vegetação, com diferenças nas abundâncias e dominância de espécies em função do tempo e da cobertura vegetal, Algumas espécies têm potencial promissor como indicadores de ambientes. As duas espécies examinadas no Cerrado se comportaram de forma independente entre seca e chuva, porém não apresentaram níveis diferentes de assimetria flutuante em suas asas. Necessita-se de abordagens específicas para cada indicador forense e em função das suas respectivas trajetórias ecológicas e evolutivas para reduzir os graus de incerteza na prática forense.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).Forensic entomology consists in the interpretation of entomological evidence in criminal investigations. Forensic entomologists’ aim is to infer the postmortem interval based on individual or communitarian features of the specimens. For accurate prediction, it is important that entomologists know the degree of phenotypic variation and what factors influence it. Biotic and abiotic factor interfere in individuals, leading to morphological variation in insects, and this influence yield different results in males and females. The present work investigated (1) Sexual size dimorphism in three species of necrophagous calliphorids in response to density; (2) how those three species respond in wing morphology to intra and interspecific competition; (3) the temporal and spatial structure of necrophagous calliphorids community in an environmentally protected area in the Federal District and the morphological variation of two species (a native and an exotic) in different seasons and vegetation covers, and; (4) how these two species alter their wing morphology in response to temporal (dry and rainy season) and spatial (grassland and forest) heterogeneity. The results show that wing morphology in males and females of three species of necrophagous calliphorids display different responses to density, as well as interspecific competition. We also showed that community composition changes in response to time e vegetation cover, with abundance and dominance differences regarding both seasons and vegetation types, and some species have potential as indicators of environments. Furthermore, the two species examined in the Cerrado behave differently between the months of the dry and the rainy season, but display no differences in fluctuating asymmetry levels in their wing structures These results point to the necessity of individual approaches, specific for each forensic indicator due to its ecological and evolutionary trajectories. Only through a systematic analysis and clear delimitation of population it is going to be possible to reduce uncertainty in forensic practice

Wing symmetry in wild drosophilids (Insecta, Diptera) is not affected by season in the Brazilian Cerrado

The development of an organism is a controlled process, which can be disrupted by genetic or environmental stress. Although fluctuating asymmetry is widely used as an indicator of developmental instability, its effectiveness has been questioned due to the contradictory results produced by this technique which, at least in part, probably reflects methodological inappropriateness. Here, we investigated if wing asymmetry of drosophilids increases when they develop during the dry season in the Brazilian savanna, considered a stressful season for these insects. Using protocols designed to avoid methodological problems, we analysed the wings of Zaprionus indianus and three species of the genus Drosophila (D. mercatorum, D. simulans, and D. sturtevanti). There was no significative difference in wing asymmetry in any of the four species between the dry and rainy seasons. The similar wing asymmetry levels between seasons may mean that during the dry season drosophilids are submitted to strong natural selection and the asymmetric individuals have less chance of surviving. Alternatively, environmental drought may not affect the wing symmetry. Although our study added more data to the relationship between asymmetry and stress, this discussion seems to be far from being solved

A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect?

Two principal methods are commonly employed for the estimation of developmental instability at the population level. Some studies use variances of morphological traits (σ2p), while others use fluctuating asymmetry (FA). In both cases, differences in the degree of developmental instability can be tested with an F-test, which is the most common way to compare variances. However, the variance is expected to scale proportionally to the square of the mean as there is a tendency in biological data for σ2p to scale proportionally to the square of the mean ( ): σ2p = Z ξ, where ξ is the scaling exponent, which is expected to be two for pure statistical reasons,  is the mean of the trait and Z is a measure of individual-level variability. Because of this scaling effect, the fluctuating asymmetry will be affected, FA is estimated as the variance between the right and the left sides of a trait (σ2r − l = σ2r + σ2l − 2rσrσl), where σ2r and σ2l are the variances of the right and the left trait values, respectively. In this paper, we propose a novel method that allows an exact correction of the scaling effect, which will enable a proper comparison of the degree of fluctuating asymmetry for a trait. The problem of the scaling of the FA with the trait size is quite crucial if FA is to be considered an indicator of fitness or an indicator of environmental or genetic stress, as different stresses or fitness levels are typically accompanied by a change of the traits’