Mendel's reaction to Darwin's provisional hypothesis of pangenesis and the experiment that could not wait.
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ABSTRACT:
SUBMITTER: van Dijk PJ
PROVIDER: S-EPMC9273598 | biostudies-literature | 2022 Jul
REPOSITORIES: biostudies-literature
Publications
Mendel's reaction to Darwin's provisional hypothesis of pangenesis and the experiment that could not wait.
van Dijk Peter J PJ Ellis T H Noel THN
Heredity 20220527 1
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Project description:Darwin proposed two seemingly contradictory hypotheses for a better understanding of biological invasions. Strong relatedness of invaders to native communities as an indication of niche overlap could promote naturalization because of appropriate niche adaptation, but could also hamper naturalization because of negative interactions with native species ('Darwin's naturalization hypothesis'). Although these hypotheses provide clear and opposing predictions for expected patterns of species relatedness in invaded communities, so far no study has been able to clearly disentangle the underlying mechanisms. We hypothesize that conflicting past results are mainly due to the neglected role of spatial resolution of the community sampling. In this study, we corroborate both of Darwin's expectations by using phylogenetic relatedness as a measure of niche overlap and by testing the effects of sampling resolution in highly invaded coastal plant communities. At spatial resolutions fine enough to detect signatures of biotic interactions, we find that most invaders are less related to their nearest relative in invaded plant communities than expected by chance (phylogenetic overdispersion). Yet at coarser spatial resolutions, native assemblages become more invasible for closely-related species as a consequence of habitat filtering (phylogenetic clustering). Recognition of the importance of the spatial resolution at which communities are studied allows apparently contrasting theoretical and empirical results to be reconciled. Our study opens new perspectives on how to better detect, differentiate and understand the impact of negative biotic interactions and habitat filtering on the ability of invaders to establish in native communities.
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Project description:A number of theories about the origins of musicality have incorporated biological and social perspectives. Darwin argued that musicality evolved by sexual selection, functioning as a courtship display in reproductive partner choice. Darwin did not regard musicality as a sexually dimorphic trait, paralleling evidence that both sexes produce and enjoy music. A novel research strand examines the effect of musicality on sexual attraction by acknowledging the importance of facial attractiveness. We previously demonstrated that music varying in emotional content increases the perceived attractiveness and dating desirability of opposite-sex faces only in females, compared to a silent control condition. Here, we built upon this approach by presenting the person depicted (target) as the performer of the music (prime), thus establishing a direct link. We hypothesized that musical priming would increase sexual attraction, with high-arousing music inducing the largest effect. Musical primes (25 s, piano solo music) varied in arousal and pleasantness, and targets were photos of other-sex faces of average attractiveness and with neutral expressions (2 s). Participants were 35 females and 23 males (heterosexual psychology students, single, and no hormonal contraception use) matched for musical background, mood, and liking for the music used in the experiment. After musical priming, females' ratings of attractiveness and dating desirability increased significantly. In males, only dating desirability was significantly increased by musical priming. No specific effects of music-induced pleasantness and arousal were observed. Our results, together with other recent empirical evidence, corroborate the sexual selection hypothesis for the evolution of human musicality.
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Project description:The floral phenotype plays a main role in the attraction and fit of pollinators. Both perianth traits and the positioning of sex organs can be subjected to natural selection and determine nonrandom mating patterns in populations. In stylar-polymorphic species, the Darwinian hypothesis predicts increased mating success between individuals with sex organs at equivalent heights (i.e. with higher reciprocity). We used paternity analyses in experimental populations of a stylar-dimorphic species. By comparing the observed mating patterns with those expected under random mating, we tested the effects of sex organ reciprocity and perianth traits on mating success. We also analysed phenotypic selection on perianth traits through female and male functions. The (dis)similarity of parental perianth traits had no direct effects on the mating patterns. Sex organ reciprocity had a positive effect on mating success. Narrow floral tubes increased this effect in upper sex organs. Perianth traits showed little signs of phenotypic selection. Female and absolute fitness measures resulted in different patterns of phenotypic selection. We provide precise empirical evidence of the Darwinian hypothesis about the functioning of stylar polymorphisms, demonstrating that mating patterns are determined by sex organ reciprocity and only those perianth traits which are critical to pollinator fit.
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Project description:The sit-and-wait hypothesis predicts that bacteria can become more virulent when they survive and transmit outside of their hosts due to circumventing the costs of host mortality. While this hypothesis is largely supported theoretically and through comparative analysis, experimental validation is limited. Here we test this hypothesis in Streptococcus suis, an opportunistic zoonotic pig pathogen, where a pathogenic ecotype proliferated during the change to intensive pig farming that amplifies opportunities for fomite transmission. We show in an in vitro environmental survival experiment that pathogenic ecotypes survive for longer than commensal ecotypes, despite similar rates of decline. The presence of a polysaccharide capsule has no consistent effect on survival. Our findings suggest that extended survival in the food chain may augment the zoonotic capability of S. suis. Moreover, eliminating the long-term environmental survival of bacteria could be a strategy that will both enhance infection control and curtail the evolution of virulence.
| S-EPMC11407517 | biostudies-literature
Project description:Heteranthery, the presence of two or more anther types in the same flower, is taxonomically widespread among bee-pollinated angiosperms, yet has puzzled botanists since Darwin. We test two competing hypotheses for its evolution: the long-standing 'division of labour' hypothesis, which posits that some anthers are specialized as food rewards for bees whereas others are specialized for surreptitious pollination, and our new hypothesis that heteranthery is a way to gradually release pollen that maximizes pollen delivery. We examine the evolution of heteranthery and associated traits across the genus Clarkia (Onagraceae) and study plant-pollinator interactions in two heterantherous Clarkia species. Across species, heteranthery is associated with bee pollination, delayed dehiscence and colour crypsis of one anther whorl, and movement of that anther whorl upon dehiscence. Our mechanistic studies in heterantherous species show that bees notice, forage on and export pollen from each anther whorl when it is dehiscing, and that heteranthery promotes pollen export. We find no support for division of labour, but multifarious evidence that heteranthery is a mechanism for gradual pollen presentation that probably evolved through indirect male-male competition for siring success.
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Project description:Darwin's naturalization hypothesis (DNH) proposes that colonization is less likely when the colonizing species is related to members of the invaded community, because evolutionary closeness intensifies competition among species that share similar resources. Studies that have evaluated DNH from correlational evidence have yielded controversial results with respect to its occurrence and generality. In the present study we carried out a set of manipulative experiments in which we controlled the phylogenetic relatedness of one colonizing species (Lactuca sativa) with five assemblages of plants (the recipient communities), and evaluated the colonizing success using five indicators (germination, growth, flowering, survival, and recruitment). The evolutionary relatedness was calculated as the mean phylogenetic distance between Lactuca and the members of each assemblage (MPD) and by the mean phylogenetic distance to the nearest neighbor (MNND). The results showed that the colonization success of Lactuca was not affected by MPD or MNND values, findings that do not support DNH. These results disagree with experimental studies made with communities of microorganisms, which show an inverse relation between colonization success and phylogenetic distances. We suggest that these discrepancies may be due to the high phylogenetic distance used, since in our experiments the colonizing species (Lactuca) was a distant relative of the assemblage members, while in the other studies the colonizing taxa have been related at the congeneric and conspecific levels. We suggest that under field conditions the phylogenetic distance is a weak predictor of competition, and it has a limited role in determining colonization success, contrary to prediction of the DNH. More experimental studies are needed to establish the importance of phylogenetic distance between colonizing species and invaded community on colonization success.
| S-EPMC4139339 | biostudies-literature
Project description:Background:Despite numerous tests of Darwin's naturalization hypothesis (DNH) evidence for its support or rejection is still contradictory. We tested a DNH derived prediction stating that nonnative species (NNS) without native congeneric relatives (NCR) will spread to a greater number of localities than species with close relatives in the new range. This test controlled the effect of residence time (Rt) on the spread of NNS and used naturalized species beyond their lag phase to avoid the effect of stochastic events in the establishment and the lag phases that could obscure the NCR effects on NNS. Methods:We compared the number of localities (spread) occupied by NNS with and without NCR using 13,977 herbarium records for 305 NNS of weeds. We regressed the number of localities occupied by NNS versus Rt to determine the effect of time on the spread of NNS. Then, we selected the species with Rt greater than the expected span of the lag phase, whose residuals were above and below the regression confidence limits; these NNS were classified as widespread (those occupying more localities than expected by Rt) and limited-spread (those occupying fewer localities than expected). These sets were again subclassified into two groups: NNS with and without NCR at the genus level. The number of NNS with and without NCR was compared using ?2 tests and Spearman correlations between the residuals and the number of relatives. Then, we grouped the NNS using 34 biological attributes and five usages to identify the groups' possible associations with spread and to test DNH. To identify species groups, we performed a nonmetric multidimensional scaling (NMDS) analysis and evaluated the influences of the number of relatives, localities, herbarium specimens, Rt, and residuals of regression. The Spearman correlation and the Mann-Whitney U test were used to determine if the DNH prediction was met. Additionally, we used the clustering objects on subsets of attributes (COSA) method to identify possible syndromes (sets of biological attributes and usages) associated to four groups of NNS useful to test DNH (those with and without NCR and those in more and fewer localities than expected by Rt). Results:Residence time explained 33% of the variation in localities occupied by nonnative trees and shrubs and 46% of the variation for herbs and subshrubs. The residuals of the regression for NNS were not associated with the number or presence of NCR. In each of the NMDS groups, the number of localities occupied by NNS with and without NCR did not significantly differ. The COSA analysis detected that only NNS with NCR in more and fewer localities than expected share biological attributes and usages, but they differ in their relative importance. Discussion:Our results suggest that DNH does not explain the spread of naturalized species in a highly heterogeneous country. Thus, the presence of NCR is not a useful characteristic in risk analyses for naturalized NNS.
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Project description:An organic chemistry experiment is described that is based on recent research to elucidate a novel cation-π interaction between tetraalkammonium cations and propargyl hydrazines. This non-bonded interaction is a key component of the mechanism of ammonium-catalyzed intramolecular cycloaddition of nitrogen to the terminal carbon of a C-C triple bond of the propargyl substrate. In this teaching experiment, reactions and control experiments are employed to demonstrate the testing of two alternative mechanistic hypotheses. Specifically, cyclization reactions are performed with a soluble base (sodium phenoxide) with and without tetrabutylammonium bromide under homogeneous conditions. Students observe that the added ammonium salt accelerates the reaction. They are then encouraged to develop a testable hypothesis for the role of the ammonium salt in the cyclization mechanism: typical phase transfer or other. IR spectroscopy is then used to directly observe a dose dependent shift of the alkyne stretching mode due to a cation-π interaction. In this experiment, undergraduate "researchers" were able to practice the scientific method on a contemporary system and see how data are generated and interpreted to adjudicate between rival hypotheses in a way that emulates authentic and current research in a lab setting. This experimental design was tested on students enrolled in the introductory undergraduate Organic Chemistry Lab.
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Project description:Invasive species have great ecological and economic impacts and are difficult to control once established, making the ability to understand and predict invasive behavior highly desirable. Preemptive measures to prevent potential invasive species from reaching new habitats are the most economically and environmentally efficient form of management. Darwin's naturalization hypothesis predicts that invaders less related to native flora are more likely to be successful than those that are closely related to natives. Here we test this hypothesis, using the weed-rich thistle tribe, Cardueae, in the California Floristic Province, a biodiversity hotspot, as our study system. An exhaustive molecular phylogenetic approach was used, generating and examining more than 100,000 likely phylogenies of the tribe based on nuclear and chloroplast DNA markers, representing the most in-depth reconstruction of the clade to date. Branch lengths separating invasive and noninvasive introduced taxa from native California taxa were used to represent phylogenetic distances between these groups and were compared at multiple biogeographical scales to ascertain whether invasive thistles are more or less closely related to natives than noninvasive introduced thistles are. Patterns within this highly supported clade show that not only are introduced thistles more closely related to natives more likely to be invasive, but these invasive species are also evolutionarily closer to native flora than by chance. This suggests that preadaptive traits are important in determining an invader's success. Such rigorous molecular phylogenetic analyses may prove a fruitful means for furthering our understanding of biological invasions and developing predictive frameworks for screening potential invasive taxa.
| S-EPMC3816436 | biostudies-literature