First detection of chromosomal inversions in a natural population of the invasive pest species Drosophila suzukii

Drosophila suzukii is native to East and Southeast Asia and spread very fast around the world being considered an invasive pest species. Many demographic, population genetics and genomic studies have been recently developed, but so far no analysis has been carried out regarding the presence of chromosomal inversions in D. suzukii natural populations. In this research, we studied polytene chromosomes of flies collected from the Font Groga (Barcelona) population. The chromosomes and many of their segments were characterized for their similarity with those from D. melanogaster. This is the report of one paracentric inversion (in heterozygous condition) in the right arm of the third chromosome (3R). As far as we know, it is the first time that an inversion has been observed in a D. suzukii natural population. Finally, the evolutionary significance of the finding of inversions in this species is discussed.

Changes in chromosomal polymorphism and global warming: the case of Drosophila subobscura from Apatin (Serbia)

In this study, chromosomal inversion polymorphism data for a natural population of Drosophila subobscura from a swampy region near the town of Apatin (Serbia) were compared with data for the same population collected approximately 15 years earlier. The pattern of chromosomal inversion polymorphism changed over time. There were significant increases in the frequency of characteristic southern latitude ("warm" adapted) chromosomal arrangements and significant decreases in the frequency of characteristic northern latitude ("cold" adapted) chromosomal arrangements in the O and U chromosomes. The chromosomal arrangements O3+4 and O3+4+22 (derived from the O3+4 arrangement) showed significant increases in 2008 and 2009 with regard to the 1994 sample. There was also a significant increase (~50 percent) in the U1+2 arrangement, while U1+8+2 (a typical southern arrangement) was detected for the first time. Since the Apatin swampy population of D. subobscura has existed for a long time in a stable habitat with high humidity that has not been changed by man our results indicate that natural selection has produced chromosomal changes in response to the increase in temperature that has occurred in the Balkan Peninsula of central southeastern European.

A cytological study of the O5 chromosomal inversion of Drosophila subobscura (Diptera, Drosophilidae)

The O5 chromosomal inversion has been a cornerstone for understanding different aspects of the American colonization by Drosophila subobscura. To obtain more information of this evolutionary event it is important to know the pattern of bands of this inversion in detail. Comparing this pattern with that of D. melanogaster it is possible to predict which genes are located inside or close to the O5 inversion and use them as genetic markers. In this study, the complete band pattern of the O5 inversion is presented. Furthermore, the most important genes located inside it have been predicted. Finally, a constriction located close to the proximal breakage point of the O5 inversion has been observed many times and its possible genetic significance is discussed

Phenotypic plasticity in colonizing populations of Drosophila subobscura

A plasticidade fenotípica de alguns caracteres quantitativos foi estudada em duas populaçöes colonizadoras de Drosophila subobscura (Davis e Eureka, Califórnia). Analisaram-se tanto o efeito da temperatura como o da criaçäo em laboratório. A criaçäo em laboratório durante quatro geraçöes a 18ºC aumentou significativamente o comprimento da asa e da tíbia. Este incremento foi semelhante ao obtido quando as moscas foram cultivadas a 13ºC durante duas geraçöes. O ambiente de temperatura baixa pode ser considerado mais estressante para as fêmeas, pois elas apresentaram um aumento na variância fenotípica. As duas populaçöes analisadas apresentaram uma grande plasticidade fenotípica, apesar do "gargalo" genético produzido durante o processo colonizador. Nossos estudos mostram que a manutençäo das moscas no laboratório por um período de tempo relativamente curto é capaz de mudar significativamente alguns caracteres quantitativos, sendo fundamental analisar as moscas imediatamente após capturá-las, para se obterem estimativas confiáveis na análise de tais caracteres nas populaçöes naturais.