Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Flight speed is positively correlated with body size in animals<jats:sup>1</jats:sup>. However, miniature featherwing beetles can fly at speeds and accelerations of insects three times their size<jats:sup>2</jats:sup>. Here we show that this performance results from a reduced wing mass and a previously unknown type of wing-motion cycle. Our experiment combines three-dimensional reconstructions of morphology and kinematics in one of the smallest insects, the beetle <jats:italic>Paratuposa placentis</jats:italic> (body length 395 μm). The flapping bristled wings follow a pronounced figure-of-eight loop that consists of subperpendicular up and down strokes followed by claps at stroke reversals above and below the body. The elytra act as inertial brakes that prevent excessive body oscillation. Computational analyses suggest functional decomposition of the wingbeat cycle into two power half strokes, which produce a large upward force, and two down-dragging recovery half strokes. In contrast to heavier membranous wings, the motion of bristled wings of the same size requires little inertial power. Muscle mechanical power requirements thus remain positive throughout the wingbeat cycle, making elastic energy storage obsolete. These adaptations help to explain how extremely small insects have preserved good aerial performance during miniaturization, one of the factors of their evolutionary success.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Since the first half of the twentieth century, evolutionary theory has been dominated by the idea that mutations occur randomly with respect to their consequences<jats:sup>1</jats:sup>. Here we test this assumption with large surveys of de novo mutations in the plant <jats:italic>Arabidopsis thaliana</jats:italic>. In contrast to expectations, we find that mutations occur less often in functionally constrained regions of the genome—mutation frequency is reduced by half inside gene bodies and by two-thirds in essential genes. With independent genomic mutation datasets, including from the largest <jats:italic>Arabidopsis</jats:italic> mutation accumulation experiment conducted to date, we demonstrate that epigenomic and physical features explain over 90% of variance in the genome-wide pattern of mutation bias surrounding genes. Observed mutation frequencies around genes in turn accurately predict patterns of genetic polymorphisms in natural <jats:italic>Arabidopsis</jats:italic> accessions (<jats:italic>r</jats:italic> = 0.96). That mutation bias is the primary force behind patterns of sequence evolution around genes in natural accessions is supported by analyses of allele frequencies. Finally, we find that genes subject to stronger purifying selection have a lower mutation rate. We conclude that epigenome-associated mutation bias<jats:sup>2</jats:sup> reduces the occurrence of deleterious mutations in <jats:italic>Arabidopsis</jats:italic>, challenging the prevailing paradigm that mutation is a directionless force in evolution.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Host genetic factors can confer resistance against malaria<jats:sup>1</jats:sup>, raising the question of whether this has led to evolutionary adaptation of parasite populations. Here we searched for association between candidate host and parasite genetic variants in 3,346 Gambian and Kenyan children with severe malaria caused by <jats:italic>Plasmodium falciparum</jats:italic>. We identified a strong association between sickle haemoglobin (HbS) in the host and three regions of the parasite genome, which is not explained by population structure or other covariates, and which is replicated in additional samples. The HbS-associated alleles include nonsynonymous variants in the gene for the acyl-CoA synthetase family member<jats:sup>2–4</jats:sup><jats:italic>PfACS8</jats:italic> on chromosome 2, in a second region of chromosome 2, and in a region containing structural variation on chromosome 11. The alleles are in strong linkage disequilibrium and have frequencies that covary with the frequency of HbS across populations, in particular being much more common in Africa than other parts of the world. The estimated protective effect of HbS against severe malaria, as determined by comparison of cases with population controls, varies greatly according to the parasite genotype at these three loci. These findings open up a new avenue of enquiry into the biological and epidemiological significance of the HbS-associated polymorphisms in the parasite genome and the evolutionary forces that have led to their high frequency and strong linkage disequilibrium in African <jats:italic>P. falciparum</jats:italic> populations.</jats:p>