selective pressures
Recently Published Documents





2022 ◽  
Viola Introini ◽  
Alejandro Marin-Menendez ◽  
Guilherme Nettesheim ◽  
Yen-Chun Lin ◽  
Silvia N Kariuki ◽  

Malaria parasites such as Plasmodium falciparum have exerted formidable selective pressures on the human genome. Of the human genetic variants associated with malaria protection, beta thalassaemia (a haemoglobinopathy) was the earliest to be associated with malaria prevalence. However, the malaria protective properties of beta thalassaemic erythrocytes remain unclear. Here we studied the mechanics and surface protein expression of beta thalassaemia heterozygous erythrocytes, measured their susceptibility to P. falciparum invasion, and calculated the energy required for merozoites to invade them. We found invasion-relevant differences in beta thalassaemic cells versus matched controls, specifically: elevated membrane tension, reduced bending modulus, and higher levels of expression of the major invasion receptor basigin. However, these differences acted in opposition to each other with respect to their likely impact on invasion, and overall we did not observe beta thalassaemic cells to have lower P. falciparum invasion efficiency for any of the strains tested.

2022 ◽  

Cancer develops through the evolution of somatic cells in multicellular bodies. The familiar dynamics of organismal evolution, including mutations, natural selection, genetic drift, and migration, also occur among the cells of multicellular organisms. In some cases, but not all, these evolutionary processes lead to cancer. This has profound implications for both our understanding of cancer and our treatment of the disease, as well as its prevention. All of our medical interventions impose selective pressures on the heterogeneous populations of billions of cells in tumors, and tend to select for mutant cells that are resistant to the intervention, regardless of whether the intervention is a drug, radiation, the immune system, or anything else that has been tried. We will likely need evolutionary and ecological approaches to cancer to manage its evolution in response to our interventions. The field of the evolutionary biology and ecology of cancer is still young and relatively small. We are in the early stages of translating ideas and tools from evolutionary biology and ecology to study and manage cancers. There is a desperate need for more researchers with expertise in evolutionary biology and ecology to apply their skills and ideas to cancer. Currently, there are far more important questions that need to be addressed than there are people to address them.

Mammalia ◽  
2022 ◽  
Vol 0 (0) ◽  
Ari A. Rice ◽  
Madison T. Nadler ◽  
Isaac T. Grosner ◽  
Moed Gerveni ◽  
Logan K. Parr ◽  

Abstract Cases of albinism have been reported in less than 2% of living rodent species. Here, we report the first description of complete albinism in Baiomys taylori along with photographic evidence. This adult female was captured on three occasions as part of a long-term small mammal study on rangelands of extreme southern Texas. The individual was developing teats upon the third capture, an early sign of pregnancy. Despite selective pressures against albino phenotypes, this animal was able to survive to adulthood and potentially pass its albino alleles to offspring.

Justin Boyles ◽  
Emily Johnson ◽  
Nathan W. Fuller ◽  
Kirk Silas ◽  
Lily Hou ◽  

Hibernators adjust the expression of torpor behaviourally and physiologically to balance the benefits of energy conservation in hibernation against the physiological and ecological costs. Small fat-storing species, like many cave-hibernating bats, have long been thought to be highly constrained in their expression of hibernation because they must survive winter relying only on endogenous energy stores. We evaluated behavioural microclimate selection in tri-colored bats (Perimyotis subflavus (Cuvier, 1832)) across a three-month hibernation experiment under laboratory conditions. We also opportunistically tested for evidence of acclimatization in torpid metabolic rate (TMR). When given access to gradients in microclimate, bats tended to choose the warmest temperature available (11°C) while almost completely avoiding the driest condition available (85% relative humidity at 8°C). Further, bats held at different temperatures over the course of the hibernation showed no differences in TMR when measured under common conditions at the end of hibernation. Taken together, our results suggest selective pressures to conserve energy during hibernation are not overwhelmingly strong and further support the proposition that optimal expression of hibernation is something less than the maximal expression of hibernation unless the animal is nearing starvation.

2022 ◽  
Yongsen Ruan ◽  
Mei Hou ◽  
Xiaolu Tang ◽  
Xionglei He ◽  
Xuemei Lu ◽  

In new epidemics after the host shift, the pathogens may experience accelerated evolution driven by novel selective pressures. When the accelerated evolution enters a positive feedback loop with the expanding epidemics, the pathogen's runaway evolution may be triggered. To test this possibility in COVID-19, we analyze the extensive databases and identify 5 major waves of strains, one replacing the previous one in 2020-2021. The mutations differ entirely between waves and the number of mutations continues to increase, from 3-4 to 21-31. The latest wave is the Delta strain which accrues 31 new mutations to become highly prevalent. Interestingly, these new mutations in Delta strain emerge in multiple stages with each stage driven by 6-12 coding mutations that form a fitness group. In short, the evolution of SARS-CoV-2 from the oldest to the youngest wave, and from the earlier to the later stages of the Delta wave, is a process of acceleration with more and more mutations. The global increase in the viral population size (M(t), at time t) and the mutation accumulation (R(t)) may have indeed triggered the runaway evolution in late 2020, leading to the highly evolved Alpha and then Delta strain. To suppress the pandemic, it is crucial to break the positive feedback loop between M(t) and R(t), neither of which has yet to be effectively dampened by late 2021. New waves beyond Delta, hence, should not be surprising.

Maarten J. Wensink ◽  
Alan A. Cohen

The classical evolutionary theories of aging suggest that aging evolves due to insufficient selective pressure against it. In these theories, declining selection pressure with age leads to aging through genes or resource allocations, implying that aging could potentially be stalled were genes, resource allocation, or selection pressure somewhat different. While these classical evolutionary theories are undeniably part of a description of the evolution of aging, they do not explain the diversity of aging patterns, and they do not constitute the only possible evolutionary explanation. Without denying selection pressure a role in the evolution of aging, we argue that the origin and diversity of aging should also be sought in the nature and evolution of organisms that are, from their very physiological make up, unmaintainable. Drawing on advances in developmental biology, genetics, biochemistry, and complex systems theory since the classical theories emerged, we propose a fresh evolutionary-mechanistic theory of aging, the Danaid theory. We argue that, in complex forms of life like humans, various restrictions on maintenance and repair may be inherent, and we show how such restrictions are laid out during development. We further argue that there is systematic variation in these constraints across taxa, and that this is a crucial factor determining variation in aging and lifespan across the tree of life. Accordingly, the core challenge for the field going forward is to map and understand the mosaic of constraints, trade-offs, chance events, and selective pressures that shape aging in diverse ways across diverse taxa.

2022 ◽  
pp. 128201
Chenchen Peng ◽  
Xuehua Wan ◽  
Jingjing Zhang ◽  
Bingling Zhang ◽  
Shuo Wang ◽  

Antibiotics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 50
Mathilde Lescat ◽  
Mélanie Magnan ◽  
Sonia Kenmoe ◽  
Patrice Nordmann ◽  
Laurent Poirel

Bacterial adaptation to antiseptic selective pressure might be associated with decreased susceptibility to antibiotics. In Gram-negative bacteria, some correlations between reduced susceptibility to chlorhexidine (CHX) and polymyxins have been recently evidenced in Klebsiella pneumoniae. In the present study, four isolates belonging to distinct enterobacterial species, namely K. pneumoniae, Escherichia coli, Klebsiella oxytoca and Enterobacter cloacae, were submitted to in-vitro selective adaptation to two antiseptics, namely CHX and octenidine (OCT), and to the antibiotic colistin (COL). Using COL as selective agent, mutants showing high MICs for that molecule were recovered for E. cloacae, K. pneumoniae and K. oxytoca, exhibiting a moderate decreased susceptibility to CHX, whereas OCT susceptibility remained unchanged. Using CHX as selective agent, mutants with high MICs for that molecule were recovered for all four species, with a cross-resistance observed for COL, while OCT susceptibility remained unaffected. Finally, selection of mutants using OCT as selective molecule allowed recovery of K. pneumoniae, K. oxytoca and E. cloacae strains showing only slightly increased MICs for that molecule, without any cross-elevated MICs for the two other molecules tested. No E. coli mutant with reduced susceptibility to OCT could be obtained. It was therefore demonstrated that in-vitro mutants with decreased susceptibility to CHX and COL may be selected in E. coli, K. pneumoniae, K. oxytoca and E. cloacae, showing cross-decreased susceptibility to COL and CHX, but no significant impact on OCT efficacy. On the other hand, mutants were difficult to obtain with OCT, being obtained for K. pneumoniae and E. cloacae only, showing only very limited decreased susceptibility in those cases, and with no cross effect on other molecules. Whole genome sequencing enabled deciphering of the molecular basis of adaptation of these isolates under the respective selective pressures, with efflux pumps or lipopolysaccharide biosynthesis being the main mechanisms of adaptation.

2021 ◽  
Kai R Caspar ◽  
Fabian Pallasdies ◽  
Larissa Mader ◽  
Heitor Sartorelli ◽  
Sabine Begall

The evolution of human right-handedness has been intensively debated for decades. Manual lateralization patterns in non-human primates have the potential to elucidate evolutionary determinants of human handedness. However, restricted species samples and inconsistent methodologies are limiting comparative phylogenetic studies. By combining original data with published literature reports, we assembled data on hand preferences for standardized object manipulation in 1,806 individuals from 38 species of anthropoid primates, including monkeys, apes, and humans. Based on that, we employ quantitative phylogenetic methods to test prevalent hypotheses on the roles of ecology, brain size and tool use in primate handedness evolution. We confirm that human right-handedness represents an unparalleled extreme among anthropoids and found taxa displaying significant population-level handedness to be notably rare. Species-level direction of manual lateralization was largely uniform among non-human primates and neither correlated with phylogeny nor with any of the selected biological predictors. In contrast, we recovered highly variable patterns of hand preference strength, which show signatures of both ecology and phylogeny. In particular, terrestrial primates tend to display weaker hand preferences than arboreal species. These results challenge popular ideas on primate handedness evolution, especially the postural origins hypothesis. Furthermore, they point to a potential adaptive benefit of disparate lateralization strength in primates, a measure of hand preference that has often been overlooked in the past. Finally, our data show that human lateralization patterns do not align with trends found among other anthropoids, suggesting that unique selective pressures gave rise to the unusual hand preferences displayed by our species.

2021 ◽  
Tara M Mandalaywala

Status is a complex, but crucially important, aspect of life across species. In recent decades, researchers have made significant contributions to our understanding of both the pathways by which status can be attained, as well as our underlying capacities for reasoning about these pathways. In 2001, Henrich & Gil-White proposed a prestige-based pathway to status where low status actors willingly defer to competent or knowledgeable high status actors, as a means of facilitating social learning and cultural transmission. Although this type of status hierarchy, and the capacity to reason about it, was hypothesized to be unique to humans, here I argue that there are several reasons why we might observe prestige-based status, and the capacity for reasoning about this pathway to status, in some nonhuman species as well. These reasons focus on the prevalence, importance, and sophistication of social learning in certain taxa, as well as the marked variation in hierarchy characteristics and structure across species. I point out places where our current methodologies encounter difficulties distinguishing whether a hierarchy in the wild is based on dominance or prestige, where our experimental methods leave us unable to assess whether an individual is reasoning about a high status actor as being prestigious or formidable, and provide suggestions for addressing these limitations. Adopting a comparative approach will clarify whether prestige-based status truly is unique to humans, and—if not—precisely what selective pressures facilitate the emergence of prestige-based status and the capacity for reasoning about it.

Sign in / Sign up

Export Citation Format

Share Document