Bemisia tabaci (Genn.) represents a complex of cryptic species that causes losses of many valuable crops. Even though there are differences in their ability to colonize hosts, transmit phytovirus and develop resistance to insecticides, the genetic differentiation of the insect populations is important for the adoption of control measures. Therefore, the genetic diversity

Innovative approaches used to combat Chagas disease transmission tend to combine a set of comprehensive efforts to understand the ecology of local vectors. In this work we identified molecularly the blood meal of 181 Triatoma brasiliensis, distributed in 18 populations (8 sylvatic and 10 peridomestic), which were collected across a range of 240 km (East-West) and 95 km (North-South) in the semi-arid region of northeastern, Brazil. We used the vertebrate mitochondrial gene (cytochrome B) sequencing applied to DNA isolated from bug midgut to identify the insect blood meal sources via the BLAST procedure. The peridomestic populations were classified according to two main hypotheses of site-occupancy for T. brasiliensis: the first says that the infestation is mainly driven by structures that resemble its natural habitat (stony-like ecotopes) and the second assumes that it is associated with key-hosts (rodents and goats). Rodents of the Caviidae family (Galea spixii and Kerodon rupestris) were identified as the key-host of T. brasiliensis, but also the potential Trypanosoma cruzi reservoir-able to connect the sylvatic and domestic T. cruzi cycle. Cats also deserve to be studied better, as potential T. cruzi reservoirs. By modeling the food sources + site-occupancy + T. cruzi natural infection, we identified man-made ecotopes suitable for forming dense triatomine infestations with high rates of T. cruzi natural infection, which may be taken into account for vector control measures.

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-Knowledge on the genetic variation of populations of Bemisia tabaci (Genn.) can improve the understanding of genetic diversity found in their biotypes and, consequently, offer guidelines for its management. In this study, the molecular characterization was performed and genetic diversity data were obtained for this insect from three regions of Brazil on different crops [cotton and soybean (Mato Grosso -MT); cabbage (Distrito Federal -DF); soybean and potato (São Paulo -SP)], using RAPD markers. RAPD analysis indicated 80.6% polymorphic loci and the average genetic similarity obtained by the Jaccard coeffi cient was 0.67. The whitefl y populations collected on potato (SP) and soybean (MT) had higher genetic diversity values (0.75 and 0.72, respectively). Shannon's index (Ho) showed higher values for potato and soybean (SP e MT), and a smaller value for cabbage (DF). A high genetic divergence within and among the collected populations occurred, structured according to the regions of collection. Moreover, the great genetic similarity observed between potato (SP) and soybean (SP) populations suggested that both belong to the same biotype B and reinforces the polyphagous behavior of the species.KEY WORDS: Silverleaf whitefl y, RAPD-PCR, biotype, genetic diversity, squash silvering No Brasil, o primeiro relato de Bemisia tabaci (Genn.) data da década de 20, na Bahia, sendo citada a ocorrência do inseto em baixos níveis de infestação (Bondar 1928). Décadas mais tarde, ocorreram surtos populacionais no Norte do Paraná e na região de Ourinhos (SP) (Costa et al 1973). Após essas constatações, surtos populacionais de mosca-branca no Brasil deram-se apenas no início dos anos 90 em plantas ornamentais e em lavouras de tomate e abóbora, no estado de São Paulo. De acordo com Lourenção & Nagai (1994), os insetos ocorrendo nessas culturas pertenciam ao biótipo B, que se caracteriza, entre outros fatores, por possuir maior quantidade de plantas hospedeiras, resistência a diversos inseticidas e capacidade de induzir desordens fi siológicas a certos tipos de hospedeiros, como o prateamento da folha da aboboreira e o amadurecimento irregular dos frutos do tomateiro (Costa & Brown 1991, Brown 2000. Posteriormente, a praga disseminou-se pelas principais áreas agrícolas do país (Haji et al 1996, França et al 1996, e há relatos da sua ocorrência em muitos estados brasileiros, levando a perdas estimadas que atingem até 100% em algumas culturas e cujos prejuízos somam alguns bilhões de dólares (Ferreira & Avidos 1998).As espécies de mosca-branca são identificadas pela taxonomia convencional ou clássica, a qual tem se mostrado inefi caz para a separação dos diferentes biótipos reconhecidos para esse inseto, uma vez que dentro do complexo B. tabaci as estruturas morfológicas são muito semelhantes. Técnicas moleculares têm sido desenvolvidas e utilizadas no mundo todo, facilitando a separação dos biótipos de forma rápida e segura. Atualmente, há registros de mais de 24 biótipos no mundo, sendo que essa grande variabilidade sugere q...

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Aim Amazonia and Atlantic Rain Forests share a common biogeographical origin and have an interconnected history that includes the drier biomes between them. It is not clear if the establishment of the South American Dry Diagonal promoted isolation between these forests or if connections between them have occurred after this event. We sought to investigate biotic diversification and geographical evolution in these biomes with a phylogeographical study of Nephila clavipes, a rain forest dwelling spider. Location South America. Methods We collected 320 individuals from 49 sites and sequenced one mitochondrial and two nuclear DNA regions. We analysed the genetic diversity, structure and demography, did phylogenetic inferences, estimated divergence times, inferred ancestral areas and applied a model‐based approach to test competitive hypotheses on the species’ evolution. Results An ancient split, coincident with the Central Cordillera final uplift, segregated a Trans‐Andean Colombian lineage from the others. Four lineages occur in Brazil, with a Pleistocene divergence: one in Amazonia, one in the northern and southern Atlantic Forest and two associated with the Dry Diagonal, but also reaching the Southern Atlantic Forest and Amazonia. The biogeographical analysis indicated that some lineages have expanded their ranges along the Pleistocene. Main conclusions Pleistocene connections of Amazonia and Atlantic rain forests through the central part of the Cerrado were supported. No phylogeographical break was detected along the Atlantic Forest. Geological and climatic events contributed to lineage diversification in N. clavipes. Studying widely distributed species is primary in unveiling evolutionary patterns in highly complex regions.

Aim The Neotropical Dry Diagonal (DD) is a corridor of distinct dry environments in central South America. The main hypotheses suggest that these environments may have expanded during the glacial cycles together with a retraction of rainforests, and then shrank when the climate became wetter and warmer. However, few studies have explicitly tested the hypotheses on DD evolution. We conducted a phylogeographical study on Nephila sexpunctata, a spider endemic to Neotropical dry habitats, to enrich the understanding of DD evolutionary history. Location South‐western portion of the DD (Cerrado and Chaco). Methods We sequenced two mitochondrial regions and one nuclear DNA region of 65 individuals from 10 locations across the species’ range. We conducted analyses of genetic structure, variability, demography and inferred divergence times. We used an ecological niche modelling framework to generate hypotheses on the species’ distribution along the last glacial cycle and a model‐based approach to test the demographical scenarios that might explain the genetic patterns. Results Both markers presented low genetic diversity. Mitochondrial markers had high genetic structure, with specific geographical lineages within each biome, while the nuclear marker presented low genetic structure. Phylogeographical and demographical events encompass the last glacial cycle, with a strong post‐Last Glacial Maximum (LGM) population and spatial expansion. Model testing corroborated the recent demographical expansion of N. sexpunctata. Main Conclusions Our data suggest that Quaternary climate cycles, when moist forests periodically expanded towards the dry vegetation, influenced the diversification of DD organisms by promoting demographical events. These events might explain the genetic structure observed in N. sexpunctata; differently from what was expected by the Pleistocene refugia model, some DD species may have experienced post‐LGM expansion. Climate and geological events have both affected DD‐endemic organisms’ diversification.

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