TY - JOUR AB - Humans conceptualize the diversity of life by classifying individuals into types we call ‘species’1. The species we recognize influence political and financial decisions and guide our understanding of how units of diversity evolve and interact. Although the idea of species may seem intuitive, a debate about the best way to define them has raged even before Darwin2. So much energy has been devoted to the so-called ‘species problem’ that no amount of discourse will ever likely solve it2,3. Dozens of species concepts are currently recognized3, but we lack a concrete understanding of how much researchers actually disagree and the factors that cause them to think differently1,2. To address this, we used a survey to quantify the species problem for the first time. The results indicate that the disagreement is extensive: two randomly chosen respondents will most likely disagree on the nature of species. The probability of disagreement is not predicted by researcher experience or broad study system, but tended to be lower among researchers with similar focus, training and who study the same organism. Should we see this diversity of perspectives as a problem? We argue that we should not. AU - Stankowski, Sean AU - Ravinet, Mark ID - 9392 IS - 9 JF - Current Biology SN - 09609822 TI - Quantifying the use of species concepts VL - 31 ER - TY - JOUR AB - We report the complete analysis of a deterministic model of deleterious mutations and negative selection against them at two haploid loci without recombination. As long as mutation is a weaker force than selection, mutant alleles remain rare at the only stable equilibrium, and otherwise, a variety of dynamics are possible. If the mutation-free genotype is absent, generally the only stable equilibrium is the one that corresponds to fixation of the mutant allele at the locus where it is less deleterious. This result suggests that fixation of a deleterious allele that follows a click of the Muller’s ratchet is governed by natural selection, instead of random drift. AU - Khudiakova, Kseniia AU - Neretina, Tatiana Yu. AU - Kondrashov, Alexey S. ID - 9387 JF - Journal of Theoretical Biology KW - General Biochemistry KW - Genetics and Molecular Biology KW - Modelling and Simulation KW - Statistics and Probability KW - General Immunology and Microbiology KW - Applied Mathematics KW - General Agricultural and Biological Sciences KW - General Medicine SN - 0022-5193 TI - Two linked loci under mutation-selection balance and Muller’s ratchet VL - 524 ER - TY - GEN AB - Chromosomal inversion polymorphisms, segments of chromosomes that are flipped in orientation and occur in reversed order in some individuals, have long been recognized to play an important role in local adaptation. They can reduce recombination in heterozygous individuals and thus help to maintain sets of locally adapted alleles. In a wide range of organisms, populations adapted to different habitats differ in frequency of inversion arrangements. However, getting a full understanding of the importance of inversions for adaptation requires confirmation of their influence on traits under divergent selection. Here, we studied a marine snail, Littorina saxatilis, that has evolved ecotypes adapted to wave exposure or crab predation. These two types occur in close proximity on different parts of the shore. Gene flow between them exists in contact zones. However, they exhibit strong phenotypic divergence in several traits under habitat-specific selection, including size, shape and behaviour. We used crosses between these ecotypes to identify genomic regions that explain variation in these traits by using QTL analysis and variance partitioning across linkage groups. We could show that previously detected inversion regions contribute to adaptive divergence. Some inversions influenced multiple traits suggesting that they contain sets of locally adaptive alleles. Our study also identified regions without known inversions that are important for phenotypic divergence. Thus, we provide a more complete overview of the importance of inversions in relation to the remaining genome. AU - Koch, Eva AU - Morales, Hernán E. AU - Larsson, Jenny AU - Westram, Anja M AU - Faria, Rui AU - Lemmon, Alan R. AU - Lemmon, E. Moriarty AU - Johannesson, Kerstin AU - Butlin, Roger K. ID - 12987 TI - Data from: Genetic variation for adaptive traits is associated with polymorphic inversions in Littorina saxatilis ER - TY - JOUR AB - We present a computational design system that assists users to model, optimize, and fabricate quad-robots with soft skins. Our system addresses the challenging task of predicting their physical behavior by fully integrating the multibody dynamics of the mechanical skeleton and the elastic behavior of the soft skin. The developed motion control strategy uses an alternating optimization scheme to avoid expensive full space time-optimization, interleaving space-time optimization for the skeleton, and frame-by-frame optimization for the full dynamics. The output are motor torques to drive the robot to achieve a user prescribed motion trajectory. We also provide a collection of convenient engineering tools and empirical manufacturing guidance to support the fabrication of the designed quad-robot. We validate the feasibility of designs generated with our system through physics simulations and with a physically-fabricated prototype. AU - Feng, Xudong AU - Liu, Jiafeng AU - Wang, Huamin AU - Yang, Yin AU - Bao, Hujun AU - Bickel, Bernd AU - Xu, Weiwei ID - 9408 IS - 6 JF - IEEE Transactions on Visualization and Computer Graphics SN - 19410506 TI - Computational design of skinned Quad-Robots VL - 27 ER - TY - JOUR AB - Antibiotic concentrations vary dramatically in the body and the environment. Hence, understanding the dynamics of resistance evolution along antibiotic concentration gradients is critical for predicting and slowing the emergence and spread of resistance. While it has been shown that increasing the concentration of an antibiotic slows resistance evolution, how adaptation to one antibiotic concentration correlates with fitness at other points along the gradient has not received much attention. Here, we selected populations of Escherichia coli at several points along a concentration gradient for three different antibiotics, asking how rapidly resistance evolved and whether populations became specialized to the antibiotic concentration they were selected on. Populations selected at higher concentrations evolved resistance more slowly but exhibited equal or higher fitness across the whole gradient. Populations selected at lower concentrations evolved resistance rapidly, but overall fitness in the presence of antibiotics was lower. However, these populations readily adapted to higher concentrations upon subsequent selection. Our results indicate that resistance management strategies must account not only for the rates of resistance evolution but also for the fitness of evolved strains. AU - Lagator, Mato AU - Uecker, Hildegard AU - Neve, Paul ID - 9410 IS - 5 JF - Biology letters TI - Adaptation at different points along antibiotic concentration gradients VL - 17 ER -