Observations on the Anopheles gambiae complex in the Senegal River Basin, West Africa

1. Three sibling species of mosquitoes of the Anopheles gambiae complex are found in the Senegal River Basin: An. melas Theobald, An. gambiae Giles and An. arabiensis Patton. 2. An. melas is restricted to the river delta and environs where saltwater breeding places are present. 3. An. gambiae and An. arabiensis are sympatric in the study area; An. arabiensis predominates in coastal zones where it breeds also during the dry season; An. gambiae predominates in inland areas where breeding is mostly restricted to the rainy season (July-September). 4. An. arabiensis is chromosomally polymorphic all over the study area, with much variation of inversion frequencies, particularly for the 2Ra arrangement. 5. An. gambiae is characterized by a very high frequency of the 2Rb-2La inversion arrangement which is typical of the Savanna chromosomal form.     

A comparison of the Caulobacter NA1000 and K31 genomes reveals extensive genome rearrangements and differences in metabolic potential

The genus Caulobacter is found in a variety of habitats and is known for its ability to thrive in low-nutrient conditions. K31 is a novel Caulobacter isolate that has the ability to tolerate copper and chlorophenols, and can grow at 4°C with a doubling time of 40 h. K31 contains a 5.5 Mb chromosome that codes for more than 5500 proteins and two large plasmids (234 and 178 kb) that code for 438 additional proteins. A comparison of the K31 and the Caulobacter crescentus NA1000 genomes revealed extensive rearrangements of gene order, suggesting that the genomes had been randomly scrambled. However, a careful analysis revealed that the distance from the origin of replication was conserved for the majority of the genes and that many of the rearrangements involved inversions that included the origin of replication. On a finer scale, numerous small indels were observed. K31 proteins involved in essential functions shared 80–95% amino acid sequence identity with their C. crescentus homologues, while other homologue pairs tended to have lower levels of identity. In addition, the K31 chromosome contains more than 1600 genes with no homologue in NA1000.     

Genome-wide evolutionary response to a heat wave in Drosophila

Extreme climatic events can substantially affect organismal performance and Darwinian fitness. In April 2011, a strong heat wave struck extensive geographical areas of the world, including Western Europe. At that time, we happened to resume and extend a long-term time series of seasonal genetic data in the widespread fly Drosophila subobscura, which provided a unique opportunity to quantify the intensity of the genetic perturbation caused by the heat wave. We show that the spring 2011 genetic constitution of the populations transiently shifted to summer-like frequencies, and that the magnitude of the genetic anomaly quantitatively matched the temperature anomaly. The results provide compelling evidence that direct effects of rising temperature are driving adaptive evolutionary shifts, and also suggest a strong genetic resilience in this species.     

Prezygotic isolation,mating preferences,and the evolution of chromosomal inversions

Chromosomal inversions are frequently implicated in isolating species. Models have shown how inversions can evolve in the context of postmating isolation. Inversions are also frequently associated with mating preferences, a topic that has not been studied theoretically. Here, we show how inversions can spread by capturing a mating preference locus and one or more loci involved with epistatic incompatibilities. Inversions can be established under broad conditions ranging from near panmixis to nearly complete speciation. These results provide a hypothesis to explain the growing number of examples of inversions associated with premating isolating mechanisms.     

Homozygous-viable pericentric inversions for genetic control of Lucilia Cuprina

Summary The isolation of homozygous-viable pericentric inversions for inclusion in field-female killing (FK) systems in Lucilia cuprina is described. From 7,236 irradiated chromosomes screened, 16 pericentric inversions were isolated. Four of these were viable as homozygotes. One of these, In (3LR) 14, possesses the properties required for inclusion in FK systems (tight linkage of one inversion break-point to the white-eye gene and substantial genetic exchange within the inversion in heterozygous females).     

Adaptation,ancestral variation and gene flow in a ‘Sky Island’ Drosophila species

Over time, populations of species can expand, contract, fragment and become isolated, creating subpopulations that must adapt to local conditions. Understanding how species maintain variation after divergence as well as adapt to these changes in the face of gene flow is of great interest, especially as the current climate crisis has caused range shifts and frequent migrations for many species. Here, we characterize how a mycophageous fly species, Drosophila innubila, came to inhabit and adapt to its current range which includes mountain forests in south‐western USA separated by large expanses of desert. Using population genomic data from more than 300 wild‐caught individuals, we examine four populations to determine their population history in these mountain forests, looking for signatures of local adaptation. In this first extensive study, establishing D. innubila as a key genomic "Sky Island" model, we find D. innubila spread northwards during the previous glaciation period (30–100 KYA) and have recently expanded even further (0.2–2 KYA). D. innubila shows little evidence of population structure, consistent with a recent establishment and genetic variation maintained since before geographic stratification. We also find some signatures of recent selective sweeps in chorion proteins and population differentiation in antifungal immune genes suggesting differences in the environments to which flies are adapting. However, we find little support for long‐term recurrent selection in these genes. In contrast, we find evidence of long‐term recurrent positive selection in immune pathways such as the Toll signalling system and the Toll‐regulated antimicrobial peptides.