scholarly journals Host defense triggers rapid adaptive radiation in experimentally evolving parasites

2018 ◽  
Author(s):  
Sarah E. Bush ◽  
Scott M. Villa ◽  
Juan C. Altuna ◽  
Kevin P. Johnson ◽  
Michael D. Shapiro ◽  
...  
Keyword(s):  
Host Defense ◽  
Adaptive Radiation ◽  
Phenotypic Selection ◽  
Columba Livia ◽  
Adaptive Divergence ◽  
Major Mechanism ◽  
Color Differences ◽  
Main Host ◽  
Feather Lice ◽  
Rapid Divergence

ABSTRACTAdaptive radiation occurs when the members of a single lineage evolve different adaptive forms in response to selection imposed by competitors or predators. Iconic examples include Darwin’s finches, Caribbean anoles, and Hawaiian silverswords, all of which live on islands. Parasites, which live on host “islands,” show macroevolutionary patterns consistent with adaptive radiation in response to host-imposed selection. Here we show rapid adaptive divergence of experimentally evolving feather lice in response to preening, the main host defense. We demonstrate that host defense exerts strong phenotypic selection for crypsis in lice transferred to different colored rock pigeons (Columba livia). During four years of experimental evolution (∼60 generations), the lice evolved heritable differences in color. The color differences spanned the phenotypic distribution of congeneric species of lice adapted to other species of pigeons. Our results indicate that host-mediated selection triggers rapid divergence in the adaptive radiation of parasites, which are among the most diverse organisms on earth. Our research suggests that host defense should be included with competition and predation as a major mechanism driving the evolution of biodiversity by adaptive radiation.

scholarly journals Evolution of genetic variance during adaptive radiation

2017 ◽  
Author(s):  
Greg M. Walter ◽  
J. David Aguirre ◽  
Mark W. Blows ◽  
Daniel Ortiz-Barrientos
Keyword(s):  
Natural Selection ◽  
Adaptive Radiation ◽  
Genetic Variance ◽  
Allelic Variation ◽  
Genetic Correlations ◽  
Leaf Traits ◽  
Adaptive Divergence ◽  
Ecotypic Differentiation ◽  
Divergent Natural Selection ◽  
Rapid Divergence

AbstractGenetic correlations between traits can bias adaptation away from optimal phenotypes and constrain the rate of evolution. If genetic correlations between traits limit adaptation to contrasting environments, rapid adaptive divergence across a heterogeneous landscape may be difficult. However, if genetic variance can evolve and align with the direction of natural selection, then abundant allelic variation can promote rapid divergence during adaptive radiation. Here, we explored adaptive divergence among ecotypes of an Australian native wildflower by quantifying divergence in multivariate phenotypes of populations that occupy four contrasting environments. We investigated differences in multivariate genetic variance underlying morphological traits and examined the alignment between divergence in phenotype and divergence in genetic variance. We found that divergence in mean multivariate phenotype has occurred along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits, and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with most of the divergence in phenotype among ecotypes associated with a change in trait combinations that had substantial levels of genetic variance in each ecotype. Overall, our results suggest that divergent natural selection acting on high levels of standing genetic variation might fuel ecotypic differentiation during the early stages of adaptive radiation.

scholarly journals Host defense triggers rapid adaptive radiation in experimentally evolving parasites

2019 ◽  
Vol 3 (2) ◽  
pp. 120-128 ◽  
Author(s):  
Sarah E. Bush ◽  
Scott M. Villa ◽  
Juan C. Altuna ◽  
Kevin P. Johnson ◽  
Michael D. Shapiro ◽  
...  
Keyword(s):  
Host Defense ◽  
Adaptive Radiation

scholarly journals Adaptive Divergence in Experimental Populations of Pseudomonas fluorescens. IV. Genetic Constraints Guide Evolutionary Trajectories in a Parallel Adaptive Radiation

Genetics ◽  
2009 ◽  
Vol 183 (3) ◽  
pp. 1041-1053 ◽  
Author(s):  
Michael J. McDonald ◽  
Stefanie M. Gehrig ◽  
Peter L. Meintjes ◽  
Xue-Xian Zhang ◽  
Paul B. Rainey
Keyword(s):  
Adaptive Radiation ◽  
Parallel Evolution ◽  
Adaptive Divergence ◽  
Genetic Constraints ◽  
Regulatory Modules ◽  
Fitness Effects ◽  
Evolutionary Trajectories ◽  
Adaptive Radiations ◽  
Encoding Gene ◽  
Do So

The capacity for phenotypic evolution is dependent upon complex webs of functional interactions that connect genotype and phenotype. Wrinkly spreader (WS) genotypes arise repeatedly during the course of a model Pseudomonas adaptive radiation. Previous work showed that the evolution of WS variation was explained in part by spontaneous mutations in wspF, a component of the Wsp-signaling module, but also drew attention to the existence of unknown mutational causes. Here, we identify two new mutational pathways (Aws and Mws) that allow realization of the WS phenotype: in common with the Wsp module these pathways contain a di-guanylate cyclase-encoding gene subject to negative regulation. Together, mutations in the Wsp, Aws, and Mws regulatory modules account for the spectrum of WS phenotype-generating mutations found among a collection of 26 spontaneously arising WS genotypes obtained from independent adaptive radiations. Despite a large number of potential mutational pathways, the repeated discovery of mutations in a small number of loci (parallel evolution) prompted the construction of an ancestral genotype devoid of known (Wsp, Aws, and Mws) regulatory modules to see whether the types derived from this genotype could converge upon the WS phenotype via a novel route. Such types—with equivalent fitness effects—did emerge, although they took significantly longer to do so. Together our data provide an explanation for why WS evolution follows a limited number of mutational pathways and show how genetic architecture can bias the molecular variation presented to selection.

scholarly journals Phylo-comparative analyses reveal the dual role of drift and selection in reproductive character displacement

2019 ◽  
Author(s):  
İsmail K. Sağlam ◽  
Michael R. Miller ◽  
Sean O’Rourke ◽  
Selim S. Çağlar
Keyword(s):  
Comparative Method ◽  
Reproductive Traits ◽  
Population Level ◽  
Character Displacement ◽  
Secondary Contact ◽  
Adaptive Divergence ◽  
Reproductive Character Displacement ◽  
Reproductive Character ◽  
Rapid Divergence

AbstractWhen incipient species meet in secondary contact, natural selection can rapidly reduce costly reproductive interactions by directly targeting reproductive traits. This process, called reproductive character displacement (RCD), leaves a characteristic pattern of geographic variation where divergence of traits between species is greater in sympatry than allopatry. However, because other forces can also cause similar patterns, care must be given in separating pattern from process. Here we show how the phylo-comparative method together with genomic data can be used to evaluate evolutionary processes at the population level in closely related species. Using this framework, we test the role of RCD in speciation of two cricket species endemic to Anatolian mountains by quantifying patterns of character displacement, rates of evolution and adaptive divergence. Our results show differing patterns of character displacement between species for reproductive vs. non-reproductive characters and strong patterns of asymmetric divergence. We demonstrate diversification results from rapid divergence of reproductive traits towards multiple optima under the dual influence of strong drift and selection. These results present the first solid evidence for RCD in Anatolian mountains, quantify the amount of drift and selection necessary for RCD to lead to speciation, and demonstrate the utility of phylo-comparative methods for quantifying evolutionary parameters at the population level.

The role of scratching in the control of ectoparasites on birds

The Auk ◽  
2020 ◽  
Vol 137 (2) ◽  
Author(s):  
Graham B Goodman ◽  
Margaux C Klingensmith ◽  
Sarah E Bush ◽  
Dale H Clayton
Keyword(s):  
Head And Neck ◽  
Bird Species ◽  
Parasite Load ◽  
Columba Livia ◽  
The Body ◽  
Body Regions ◽  
Feather Lice ◽  
Series Of Experiments

Abstract Grooming by birds is thought to serve essential anti-parasite functions. While preening has been well studied, little is known about the function of scratching in birds. We conducted a series of experiments to determine the effectiveness of scratching for controlling feather lice (Columbicola columbae) on Rock Pigeons (Columba livia). First, we used a hobbling technique to impair scratching. After 6 mo, hobbled birds had significantly more lice than controls that could scratch. In addition, lice on hobbled birds were concentrated on the birds’ heads and necks (i.e. the regions that birds scratch). Secondly, we tested the role the claw plays in scratching by declawing nestlings. Once mature, declawed pigeons had significantly more lice than control birds with claws. Moreover, lice on declawed birds were concentrated on the head and neck. Next, we tested whether the flange found on the middle claw of many bird species enhances scratching. We experimentally manipulated the flange; however, the number and location of lice on birds without flanges was not significantly different than that on control birds with intact flanges. Finally, we tested whether scratching removes parasites directly or indirectly by “flushing” them onto body regions where they can be preened. When we impaired scratching (with hobbles) and preening (with “bits”) we found that scratching no longer reduced the number of lice on birds. Our results indicated that scratching and preening work synergistically; scratching reduces parasite load by flushing lice onto regions of the body where they can be eliminated by preening.

scholarly journals Is Melanin a Defense Against Feather-Feeding Lice?

The Auk ◽  
2006 ◽  
Vol 123 (1) ◽  
pp. 153-161 ◽  
Author(s):  
Sarah E. Bush ◽  
Dukgun Kim ◽  
Brett R. Moyer ◽  
Jackson Lever ◽  
Dale H. Clayton
Keyword(s):  
Columba Livia ◽  
Plumage Color ◽  
Feeding Preferences ◽  
Color Morphs ◽  
Extreme Variation ◽  
Wear And Tear ◽  
Feather Lice ◽  
Different Color ◽  
Free Ranging

Abstract The adaptive basis of plumage color has received much attention, including the finding that color can reveal information about parasite loads to potential mates. A related possibility, that color may be a direct defense against parasites, has received less attention. Melanin makes feathers tough and more resistant to wear and tear. Melanin may also make feathers more difficult for feather-feeding parasites to eat. We explored the role of melanin as a possible ectoparasite defense using Rock Pigeons (Columba livia) and their feather-feeding lice (Insecta: Phthiraptera). Rock Pigeons are an ideal species for such work because of the extreme variation in the feathers of different color morphs, ranging from melanin-rich black to melanin-free white individuals. We tested the effect of melanin on lice in several ways. First, we compared the natural louse loads of free-ranging pigeons to see whether the more melanistic color morphs had fewer lice. We also did laboratory assays in which we measured the survival and reproductive success of pigeon lice forced to feed on feathers with different amounts of melanin, and we compared the quantities of feather material consumed by these lice. Finally, we tested the habitat and feeding preferences of lice exposed to feathers with different amounts of melanin. None of our tests revealed any effect of melanin on lice. We conclude that melanin is not, at least in Rock Pigeons, a defense against feather lice. ¿Es la Melanina una Defensa Contra los Piojos que se Alimentan de Plumas?

scholarly journals LL-37 Opsonizes and Inhibits Biofilm Formation of Aggregatibacter actinomycetemcomitans at Subbactericidal Concentrations

2013 ◽  
Vol 81 (10) ◽  
pp. 3577-3585 ◽  
Author(s):  
Asaf Sol ◽  
Ofir Ginesin ◽  
Stella Chaushu ◽  
Laila Karra ◽  
Shunit Coppenhagen-Glazer ◽  
...  
Keyword(s):  
Host Defense ◽  
Biofilm Formation ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Bactericidal Effect ◽  
Raw 264.7 Cells ◽  
Gingival Tissue ◽  
Host Defense Peptides ◽  
Content Type ◽  
Major Mechanism ◽  
Defense Peptides

ABSTRACTHost defense peptides are immediate responders of the innate immunity that express antimicrobial, immunoregulatory, and wound-healing activities. Neutrophils are a major source for oral host defense peptides, and phagocytosis by neutrophils is a major mechanism for bacterial clearance in the gingival tissue. Dysfunction of or reduction in the numbers of neutrophils or deficiency in the LL-37 host defense peptide was each previously linked with proliferation of oralAggregatibacter actinomycetemcomitanswhich resulted in an aggressive periodontal disease. Surprisingly,A. actinomycetemcomitansshows resistance to high concentrations of LL-37. In this study, we demonstrated that submicrocidal concentrations of LL-37 inhibit biofilm formation byA. actinomycetemcomitansand act as opsonins and agglutinins that greatly enhance its clearance by neutrophils and macrophages. Improved uptake ofA. actinomycetemcomitansby neutrophils was mediated by their opsonization with LL-37. Enhanced phagocytosis and killing ofA. actinomycetemcomitansby murine macrophage-like RAW 264.7 cells were dependent on their preagglutination by LL-37. AlthoughA. actinomycetemcomitansis resistant to the bactericidal effect of LL-37, our results offer a rationale for the epidemiological association between LL-37 deficiency and the expansion of oralA. actinomycetemcomitansand indicate a possible therapeutic use of cationic peptides for host defense.

scholarly journals Repeated adaptive divergence of microhabitat specialization in avian feather lice

BMC Biology ◽  
2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Kevin P Johnson ◽  
Scott M Shreve ◽  
Vincent S Smith
Keyword(s):  
Adaptive Divergence ◽  
Feather Lice ◽  
Microhabitat Specialization

scholarly journals A vertebrate adaptive radiation is assembled from an ancient and disjunct spatiotemporal landscape

2021 ◽  
Vol 118 (20) ◽  
pp. e2011811118
Author(s):  
Emilie J. Richards ◽  
Joseph A. McGirr ◽  
Jeremy R. Wang ◽  
Michelle E. St. John ◽  
Jelmer W. Poelstra ◽  
...  
Keyword(s):  
Adaptive Radiation ◽  
Population Genomics ◽  
De Novo ◽  
Nonsynonymous Substitution ◽  
Adaptive Divergence ◽  
Hybrid Swarm ◽  
Regulatory Variation ◽  
San Salvador ◽  
Standing Variation ◽  
San Salvador Island

To investigate the origins and stages of vertebrate adaptive radiation, we reconstructed the spatial and temporal histories of adaptive alleles underlying major phenotypic axes of diversification from the genomes of 202 Caribbean pupfishes. On a single Bahamian island, ancient standing variation from disjunct geographic sources was reassembled into new combinations under strong directional selection for adaptation to the novel trophic niches of scale-eating and molluscivory. We found evidence for two longstanding hypotheses of adaptive radiation: hybrid swarm origins and temporal stages of adaptation. Using a combination of population genomics, transcriptomics, and genome-wide association mapping, we demonstrate that this microendemic adaptive radiation of novel trophic specialists on San Salvador Island, Bahamas experienced twice as much adaptive introgression as generalist populations on neighboring islands and that adaptive divergence occurred in stages. First, standing regulatory variation in genes associated with feeding behavior (prlh, cfap20, and rmi1) were swept to fixation by selection, then standing regulatory variation in genes associated with craniofacial and muscular development (itga5, ext1, cyp26b1, and galr2) and finally the only de novo nonsynonymous substitution in an osteogenic transcription factor and oncogene (twist1) swept to fixation most recently. Our results demonstrate how ancient alleles maintained in distinct environmental refugia can be assembled into new adaptive combinations and provide a framework for reconstructing the spatiotemporal landscape of adaptation and speciation.

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