Ecol. This evolve-and-resequence experiment shows that rapid ecological differentiation can arise even under high rates of gene flow. 2.5 How do we know evolution has occurred? Genetic drift occurs when a population experiences random fluctuations in frequencies of genetic traits. Boxplots as in Extended Data Fig. B. W. Widespread evidence for incipient ecological speciation: a meta-analysis of isolation-by-ecology. Menu. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (, GUID:B935DC4D-C797-4205-801D-F9942303416C. By definition, such populations are not evolving. Caruso C.M., Case A.L. 2.4 How do we know evolution has occurred? Further investigation into mechanisms that create or maintain the spatial structure of sex ratios in gynodioecious species will provide much needed insight. Li, H. & Durbin, R. Fast and accurate short read alignment with BurrowsWheeler transform. Yeast 35, 253260 (2018). S.T. Populations with extremely high female frequencies contained rare mitochondrial haplotypes, suggesting elevated rates of CMS origin and turnover and the absence of balancing selection. 2.7 How do we know evolution has occurred? 20, 12971303 (2010). PLoS Biol. Case A.L., Finseth F.R., Barr C.M., Fishman L. Selfish evolution of cytonuclear hybrid incompatibility in. Missing data rates for Lob6, Lob9, and Lobtri1 were 1.4%, 1.1%, and 2.0%, respectively. Biol. 4 Forces of Evolution Andrea J. Alveshere, Ph.D., Western Illinois University Learning Objectives Describe the history and contributions of the Modern Synthesis. & Nguyen, A. Q. Antagonistic pleiotropy as a widespread mechanism for the maintenance of polymorphic disease alleles. ; writingreview and editing, H.J.A.-M., E.B.K., C.M.C. When a small number of parents produce just a few offspring, allele frequencies in the offspring may differ, by chance, from allele frequencies in the parents. Abbreviations of migration treatments as in the main manuscript. 85, 419445 (2010). Ecol. Individual plants rarely produce flowers of both sexes (i.e., a gynomonoecious phenotype). Maintained gene flow between two populations can also lead to a combination of the two gene pools, reducing the genetic variation between the two groups. Offspring sex ratio under inbreeding and outbreeding in a gynodioecious plant. For example, if a species of grass grows on both sides of a highway, pollen is likely to be transported from one side to the other and vice versa. 10.10 Whats up with the human female orgasm? Constraints on phenotypic evolution. and A.L.C. J. Evol. Franssen, S. U., Kofler, R. & Schltterer, C. Uncovering the genetic signature of quantitative trait evolution with replicated time series data. If any heritable variation leads to genetic changes in a population, natural selection has occurred. 1. These variations are determined by different alleles. In: Silvertown J., Antonovics J., editors. Dxy values were calculated using all genetic variants (left) or only standing genetic variation (right). Biogeography. Reproductive success of the gynodioecious, Cuguen J., Wattier R., Saumitou-Laprade P., Forcioli D., Mrchen M., Van Dijk H., Vernet P. Gynodioecy and mitochondrial DNA polymorphism in natural populations of. In these species, female plants carry male-sterility genes in their mitochondrial genomes (i.e., cytoplasmic male sterility, or CMS) [8,9], whereas hermaphrodites either do not carry CMS or carry CMS plus one or more nuclear male-fertility restorer (Rf) alleles, allowing them to produce pollen despite carrying CMS [10,11,12,13]. The remaining seven haplogroups were restricted, each occurring in fewer than four individuals in our sample. Specific details about PCR amplification conditions and genotyping are presented in Supplemental Information. Nat. These factors are the "forces of evolution." 31, 32283239 (2014). However, we did not detect any spatial structuring in population size nor metrics of genetic diversity, suggesting that extreme variation in female frequency is not strongly affected by drift or gene flow. Our results are consistent with a high degree of population genetic differentiation but low rates of contemporary gene flow. Nature 447, 585588 (2007). This variable flow of individuals in and out of the group not only changes the gene structure of the population, but can also introduce new genetic variation to populations in different geological locations and habitats. Boxplots description: center line, median; box limits, upper and lower quartiles; whiskers, 1.5x interquartile range; points, outliers. Schluter, D.Adaptive radiation along genetic lines of least resistance. Evolution 62, 24512461 (2008). When one or more of these forces are acting in a population, the. The significant geographic structure of individual pt haplogroups that we observed here is potentially consistent with the legacy of post-glacial migration/dispersal, although there was no clear correspondence of pt haplogroup structure and population sex ratios. One form of drift is the founder effect, which results when a small part of a population (the founders) moves to a new location, and the small variety of genes of the founders mean that the new population is different from the original population. Gene flow can take place between two populations of the same species through migration, and is mediated by reproduction and vertical gene transfer from parent to offspring. 8.9 What about hermaphrodites and why arent they more common? In total, we haplotyped 246 individuals (mean = 6.98) from each of 83 L. siphilitica populations (total n = 579 individuals; Table S1); 142 of these haplotypes were based on complete psbKrps16 sequences and 438 on only the minisatellite motifs (see: Supplemental Information). B. W. & Ellegren, H. Making sense of genomic islands of differentiation in light of speciation. Plastid haplogroup diversity (h) ranged from 0 to 0.81 (mean = 0.187) across populations. In two-thirds (67%) of our sampled populations, we found only one haplogroup represented and the maximum number in a single population was 4 (mean = 1.106; Figure 2, Table S1). Fig. In this way, they changed the allele frequencies in the Vietnamese gene pool. To estimate population differentiation based on the distribution of alleles among populations, we calculated FST for both pt haplogroups using Arlequin 3.5 [57] and nuclear microsatellite genotypes using GenAlEx [56]. When a small number of parents produce just a few offspring, allele frequencies in the offspring may differ, just by chance, from allele frequencies in . Curr. Flow cytometry was performed at the Core Facility Flow Cytometry at LMU. The genome sequence of Schizosaccharomyces pombe. Yet, while gene flow inhibited genetic divergence, it did not exclude evolution per se. This lack of correspondence in spatial structure suggests that, like contemporary drift and gene flow, historical migration/dispersal has not strongly affected the present-day distribution of female plants. We conservatively considered populations in these two ecoregions to be central and those outside it peripheral (Figure 1). Phillips, P. C. Epistasisthe essential role of gene interactions in the structure and evolution of genetic systems. This lack of consensus has yet to be explained. However, >90% of published studies reviewed here showed an association of urbanization with genetic drift or gene flow, highlighting the strong impact of urbanization on nonadaptive evolution. We detected 12, 17, and 21 alleles for our three nuclear microsatellite loci (Lob6, Lob9, and Lobtri1), respectively, for a total of 50 unique alleles (Table S2) and 4.25.8 alleles per population (Na in Table S3). Roux, C. et al. For nuclear microsatellites, Na and Ne were slightly higher in large vs. small populations (1-tailed t-tests, t = 2.103.89, df = 88, p < 0.019), but other groupings (including population sex ratio) showed no significant variation in any metric of nuclear genetic diversity. [(accessed on 1 July 2020)]. The analysis was conducted including all genetic variants (upper graphs) or using only variants present at the beginning of the experiment (standing genetic variation; lower graphs). Article Testing models of sex ratio evolution in a gynodioecious plant: Female frequency covaries with the cost of male fertility restoration. PomBase 2018: user-driven reimplementation of the fission yeast database provides rapid and intuitive access to diverse, interconnected information. Protoc. 87, 331333 (1953). Eckert C.G., Samis K.E., Lougheed S.C. Genetic variation across species geographical ranges: The central-marginal hypothesis and beyond. Sergio Tusso or Jochen B. W. Wolf. To look for evidence of gene flow, we used Mantel correlations to examine isolation by distance in GenAlEx [56]. 16, 940950 (2013). They result from natural selection, sexual selection, or even genetic drift: The evolution of different mating location, mating time, or mating rituals: Genetically-based changes to these aspects of mating could complete the process of reproductive isolation and . Yet, the conditions under which it can arise in the presence of gene flow remain contentious. Arnold, S. J. 10.9 What is the evidence for sexual selection in humans? Identify the forces of evolution and become familiar with examples of each. & Mitchell-Olds, T. Genetic trade-offs and conditional neutrality contribute to local adaptation: genetic basis of local adaptation. We also used 1-tailed t-tests to test the a priori expectation that h, Ho, and the total number of alleles would be higher in central vs. peripheral populations. and JavaScript. Overall, contrary to our hypothesis, we found that neither genetic drift nor gene flow have likely contributed to the extreme sex-ratio variation within this species. We also used AMOVAs to see how well categorical population size explained population diversity and among-population differentiation (Arlequin 3.5 [57]). Tusso, S., Nieuwenhuis, B.P.S., Weissensteiner, B. et al. Mol. There are two special conditions under which genetic drift occurs. government site. This change is due to four different processes: mutation, selection (natural and artificial), gene flow and genetic drift.This change happens over a relatively short (in evolutionary terms) amount of time compared to the changes termed macroevolution.. Population genetics is the branch of biology that . Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). siphilitica (Campanulaceae) is a perennial wildflower that occurs throughout northeastern North America (Figure 1, grey shading) [30]. The allele frequencies of both the population they leave and the population they enter may change. 157180 (Allen & Unwin, 1954). Fly 6, 8092 (2012). All of the data generated for this study are archived in the Sequence Read Archive (under BioProject ID PRJNA604890) at the National Centre for Biotechnology Information (www.ncbi.nlm.nih.gov/sra). Genet. Was the gene pool of the American population also affected? Bioinformatics 30, 28432851 (2014). Female and hermaphrodite flowers of L. siphilitica are easily distinguishable (photo inset; photo credit Maia F. Bailey, used with permission). Natl Acad. Garant, D., Forde, S. E. & Hendry, A. P.The multifarious effects of dispersal and gene flow on contemporary adaptation. While we observed strong centralperipheral structuring of female frequencies, none of the other predictions of the abundant-center hypotheses were supported by our data. A geographical context for the evolution of plant reproductive systems. Martin, M. Cutadapt removes adapter sequences from high-throughput sequencing reads. The Scale of Evolution We now know that variations of traits are heritable. Female frequency varied between 0 and 1 (mean = 0.218; n = 92 populations; Figure 1; Table S1). 14, e2000234 (2016). Distribution of 13 plastid haplogroups within and among populations of Lobelia siphilitica from 2009 and 2011. 13, 434445 (2000). Microevolution describes the evolution of small organisms, such as insects, while macroevolution describes the evolution of large organisms, like people and elephants. The appearance of new mutations is the most common way to introduce novel genotypic and phenotypic variance. We manually confirmed all peaks and bins for these data using Genemapper (Applied Biosystems, Carlsbad, CA, USA). & Wolf, J. Out of 142 complete sequences of the psbKrps16 region, we identified 120 unique pt haplotypes. Even a population that may initially appear to be stable, such as a pride of lions, can receive new genetic variation as developing males leave their mothers to form new prides with genetically-unrelated females. Nat. To test the hypothesis that genetic drift and/or gene flow have contributed to demographic and geographic structuring of high female frequencies in L. siphilitica, we used plastid (pt) and neutral nuclear genetic markers. R package version 1.52.1 (2019). 14, 26212635 (2005). Distribution and population sex ratios of 92 eastern North American Lobelia siphilitica populations sampled in 2009 and 2011. One common type of within-species phenotypic diversity is variation in population sex ratio [1,2,3,4,5]. 4 are here summarized to show the general trend. Levene, H. Genetic equilibrium when more than one ecological niche is available. They are called bottleneck effect and founder effect. Describe how natural selection, mutation, genetic drift, and gene flow lead to evolution Differentiate between divergent evolution and convergent evolution Describe the definition of species and how species are identified as being different Explain the difference between allopatric and sympatric speciation Natural Selection The relative contribution to variance in PC1 and PC2 is symbolized by length of the arrow. The Amish population in the U.S. and Canada had a small number of founders. 21, 434443 (2006). All of the code used for the analyses, fitness data and a list of genetic variants (in .vcf format) are available at https://github.com/EvoBioWolf/SchPom_Exp_AdaptDiv and Zenodo (https://doi.org/10.5281/zenodo.4133489)89. Soltis D.E., Morris A.B., McLachlan J.S., Manos P.S., Soltis P.S. Biol. b. Boxplot of Euclidian distance between pairs of connected population pairs per treatment and genetic background. Although populations that contained C23 had significantly lower female frequencies than those without C23 (3.9% vs. 26.7%; 2-tailed t-test, t = 5.58, df = 81, p = 0.0001), these sites are likely low female because they are almost exclusively peripheral, not because they harbor haplogroup C23. To characterize patterns of nuclear genetic diversity, we screened 1713 individuals from 90 populations, with an average of 18.67 plants per population. Gene flow is also called gene migration. Founder effects and sex ratio in the gynodioecious, Murayama K., Yahara T., Terachi T. Variation of female frequency and cytoplasmic male-sterility gene frequency among natural gynodioecious populations of wild radish (, Nilsson E., gren J. Haselhorst, M. S. H., Edwards, C. E., Rubin, M. J. CAS Boxplots as in Extended Data Fig. Abstract The role of natural selection in speciation, first described by Darwin, has finally been widely accepted. Likewise, h did not differ significantly between central and peripheral populations (1-tailed t-test, t = 0.24, df = 81, p = 0.59), nor with population size (linear regression, r2 = 0.00003, df = 81, p = 0.96). Biol. performed the experiments. 15, 176192 (2014). Natural selection, genetic drift, and gene flow are the mechanisms that cause changes in allele frequencies over time. 6, 39123922 (2016). Grouping populations by sex ratio or population size in the AMOVAs did not account for any pt molecular variation, and sex ratio alone accounted for a statistically but not biologically significant portion of nuclear diversity (~1%), reflecting populations without female plants having slightly fewer alleles than populations with female plants (ANOVA, F3,85 = 3.044.77, p < 0.033). Use this resource to answer the questions that follow. Extremely high female frequencies in gynodioecious populations cannot be readily explained by selective forces alone. Licensee MDPI, Basel, Switzerland. EMBnet. B. S. A mathematical theory of natural and artificial selection. Significant Morans I tests were followed by linear and non-linear regressions against latitude and longitude on quantitative metrics and with 2-tailed t-tests on presence of particular haplogroups. 20, 40424058 (2011). 10 Candidate genetic variants under disruptive selection per genetic background. Peer review information Nature Ecology & Evolution thanks the anonymous reviewers for their contribution to the peer review of this work. 2 Principle component analyses of z-score standardized log transformed relative fitness values across fitness components. Lowry, D. B., Rockwood, R. C. & Willis, J. H. Ecological reproductive isolation of coast and inland races of Mimulus guttatus. Ecol. Barr C.M. Which mechanism(s) is/are the most important influences on evolution? We used the plotrix package [52] in R [51] to visualize population locations as pie charts showing sex ratio (Figure 1) or haplogroup composition (Figure 2). Thus, insights into this system are key to understanding the evolution of sexual systems in flowering plants and the mechanisms that create and maintain variation in population sex ratio [6]. Founder Effect in the Amish Population. We tested for statistical associations between population sex ratio, population size (a proxy for genetic drift), and neutral genetic diversity, as well as estimated rates of gene flow. Press, 1937). Spatial patterns of demography and genetic processes across the species range: Null hypotheses for landscape conservation genetics. Ellis-van Creveld Syndrome (a form of dwarfism that involves short stature, extra fingers or toes, and possible heart defects) and several other genetic conditions that are typically rare in large populations, are common in the Pennsylvania Amish population in the United States because of driftspecifically, because of the founder effect. Others are beneficial and will spread through the population. Am. Am. Average pairwise FST for nuclear microsatellites, which should reflect more recent gene flow, indicates moderately strong population differentiation (nuclear FST = 0.222) and low rates of migration (Nem = 0.884; Table S3). ludoviciana plastids from C1 into L. siphilitica var. For parapatric populations, Dxy was additionally calculated between connected population pairs (Para_Pairs). In the genetic background genetic divergence was higher for Sympatric populations compared with Local Mating populations, which is consistent with phenotypic data. where pi is the frequency of a haplogroup, and n is sample size per population [55]. Hendry, A. P., Bolnick, D. I., Berner, D. & Peichel, C. L. Along the speciation continuum in sticklebacks. Details about PCR amplification and sequencing conditions are presented in Supplemental Information. Kartesz J.T. Distribution of values were divided per genetic background ( and ). Population genetic software for teaching and research. Genet. the spread of genetic material from one population to another; random change in the frequency of alleles Who was the geneticist who studied the workings of fruit flies' chromosomes? S.T., B.P.S.N. [14]). Beyond balancing selection: Frequent mitochondrial recombination contributes to high-female frequencies in gynodioecious. The maintenance (or not) of polygenic variation by soft selection in heterogeneous environments. Google Scholar. Haldane, J. 144, 210228 (1994). Correspondence to We ran ANOVAs to examine the a priori expectation that h, Ho, and the total number of alleles would be higher in populations with more female plants. The population has grown, but has not been subject to the diversifying effects of gene flow (that is, individuals rarely enter the population from another population). We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Two previous censuses of L. siphilitica populations documented sex ratios ranging from 0 to 100% female, with higher female frequencies at lower latitudes [14,31]. We used a 1:10 dilution of the isolated DNA for all subsequent molecular work. Macnair, M. R. Why the evolution of resistance to anthropogenic toxins normally involves major gene changes: the limits to natural selection. An angiosperm-wide analysis of the correlates of gynodioecy. Ecoregions of the conterminous United States. Each point represents a Dxy value for a single pair of populations. 12, 160 (2011). 2a). However, for five of the six common haplogroups, the presence vs. absence of each haplogroup was not associated with differences in sex ratio between populations, suggesting no relationship between specific pt haplogroups and female frequency (2-tailed t-tests, t = 0.841.83, df = 81, p > 0.07). Pairs of parapatric and local mating population are more similar in fitness than allopatric, randomized parapatric or sympatric populations. 8 Summary statistics of allele frequency change between subpopulations. 138, 7179 (2013). USA 76, 52695273 (1979). Dried buds (when possible) or leaf tissue samples were transferred to 80 C for at least one week before DNA isolation. Funding was provided to J.B.W.W. Each point represents an Fst value for a single pair of populations. Syst. Six common haplogroups accounted for 95% of sequenced individuals (Figure 2). Rev. Dbarre, F. & Gandon, S. Evolution in heterogeneous environments: between soft and hard selection. 2. and A.L.C. Why or why not? Based on Morans I, female frequency was highly spatially structured (Morans I = 0.289, p < 0.00001; Figure 1). Very few sites were ambiguous in terms of delimiting clusters of L. siphilitica plants as populations; in this analysis, we considered plants to be in separate populations when one patch was not visible from another. Accessibility StatementFor more information contact us atinfo@libretexts.org. B. Each point represents one population or subpopulation subjected to the top (blue) or bottom (red) selection regime. 11 (Columbia Univ. Whether or not a mutation is beneficial or harmful is determined by whether it helps an organism survive to sexual maturity and reproduce. Cuevas E., Lpez S. Sex ratio and sex-specific latitudinal variation in floral characteristics of gynodioecious, Ruffatto D.M., Zaya D.N., Molano-Flores B. Genetic drift is at the core of the shifting-balance theory of evolution coined by Sewall Wright where it is part of a two-phase process of adaptation of a subdivided population. R Foundation for Statistical Computing, Vienna, Austria. and J.B.W.W. Careers, Unable to load your collection due to an error. We detected no spatial structure in pt haplogroup diversity (h; Morans I = 0.055, p = 0.44), nor in microsatellite diversity (Ho, Na, or Ne; Morans I = 0.0040.08, p > 0.09). In this example, the brown coat color allele (B) is dominant over the white coat color allele (b). These five spatially clustered haplogroups were either predominantly eastern or predominantly western (relative to the midpoint of the sampled range at 85.45 longitude; 2-tailed t-tests comparing the mean longitude of populations with and without each haplogroup, t = 5.264.47, df = 81, all p < 0.0245). Upper and lower panels are differentiated by genetic background ( and populations) and include all variants (left) or only variants already present in the respective ancestral population (standing genetic variation, right). In the background, showed a similar trend, but the difference between treatments was lower, which is consistent with no observed divergence in the phenotypic data. Consequently, mean female frequency was more than 7-fold higher in central populations (38.4% female, n = 46) than peripheral populations (5.3% female, n = 46; 2-tailed t-test, t = 7.1, df = 90, p < 0.0001), and populations with >50% female plants (n = 20) were exclusively central. Therefore, we subsequently screened the minisatellite motifs for additional samples and obtained complete psbKrps16 sequences under three circumstances: when an additional, novel minisatellite was encountered; when one of the independently derived minisatellites was encountered; and as random checks for the uniqueness of minisatellite motifs that were assumed to be unique. & Mundt, F. factoextra: Extract and visualize the results of multivariate data analyses. This is a preview of subscription content, access via your institution, Access Nature and 54 other Nature Portfolio journals, Get Nature+, our best-value online-access subscription, Receive 12 digital issues and online access to articles, Prices may be subject to local taxes which are calculated during checkout. Press, 2012). Dieckmann, U., Doebeli, M., Metz, J. The sex morphs are easily identified in the field: hermaphrodite anther cylinders are dark gray-purple, while female anther cylinders are papery white and lack pollen (Figure 1, inset). Inset shows the phylogram for the 13 pt haplogroups (see: Figure S2). flowCore: flowCore: Basic structures for flow cytometry data. Shaded US counties show the known distribution of L. siphilitica based on online specimen collection databases (see text for details). the contents by NLM or the National Institutes of Health. Thank you for visiting nature.com. The genome analysis toolkit: a MapReduce framework for analyzing next-generation DNA sequencing data. Nat. 47, D821D827 (2019). The .gov means its official. Genetics 16, 97159 (1931). Plant populations experience gene flow by spreading their pollen long distances. Central vs. peripheral groupings explained ~10% of pt molecular variance; while peripheral populations contained a greater number of unique haplogroups, the haplogroups present in central populations were more divergent from each other in sequence (Figure 2). earthquakes, fire). maritima [37]). The tree used here is not the same tree as used in Adhikari et al. & Hughes, K. A. in Evolutionary Genetics: from Molecules to Morphology Vol. Other mutations are beneficial and can increase in a population if they help organisms reach sexual maturity and reproduce. Define populations and population genetics as well as the methods used to study them. Most of the servicemen returned to the United States after the war. Boxplots as in Extended Data Fig. In sexually reproducing species, the mutations that matter for evolution are those that occur in gametes. Dobzhansky, T. Genetics and the Origin of Species Vol. P-value < 0.001 (***), < 0.01 (**), or < 0.05 (*). Environmental stressors affect sex ratios in sexually dimorphic plant sexual systems. Sinclair J.P., Emlen J., Freeman D.C. Eigenvectors are indicated by arrows for each fitness component. Extended Data Fig. contracts here, Sign up for Nature Briefing: Translational Research. While theoretical models predict that higher pleiotropic costs of Rf should result in more female plants [33], there is yet little understanding of what causes variation among populations in the magnitude of cost. Genetic drift can also be magnified by natural or human-caused events, such as a disaster that randomly kills a large portion of the population, which is known as the bottleneck effect that results in a large portion of the gene pool suddenly being wiped out (Figure 11.8).In one fell swoop, the genetic structure of the survivors becomes the genetic structure of the entire population, which may . Genet. Mutation creates new genetic variation in a gene pool. Which mechanism(s) is/are the source of variation within a population? Rsnen, K. & Hendry, A. P. Disentangling interactions between adaptive divergence and gene flow when ecology drives diversification. Ratcliff, W. C., Denison, R. F., Borrello, M. & Travisano, M. Experimental evolution of multicellularity. Because we found 120 unique pt haplotypes (see: Results), all pt genetic analyses were carried out using 13 inferred phylogenetic haplogroups based on the topology of the maximum parsimony tree (Figure S2). & Tautz, D. Adaptive Speciation (Cambridge Univ. From DNA to Protein, Chapter 6: Life Cycles, Cell Division, and Inheritance, Chapter 10: Sexual Selection (contributed by Rachel Olzer), Chapter 12: Sexual Orientation and the Evolution of Homosexuality, Chapter 13: Sex Machine: Reproductive Anatomy and Physiology, Chapter 14: Copulation and Fertilization (Baby-making 101), Next: 2.11 Mechanisms of Evolution: Natural Selection, Creative Commons Attribution-NonCommercial 4.0 International License. 10.6 Unconventional ways of finding a mate. 9.3 An Introduction to Operational Sex Ratios, 9.5 The puzzle of skewed sex ratios at birth, 9.6 The Trivers-Willard hypothesis of sex allocation, 9.9 Testing Trivers-Willard in spider monkeys, 9.13 Wrapping Up: Understanding human sex ratios. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. The authors declare no conflict of interest. While our results show that population sex ratios in gynodioecious L. siphilitica are geographically clustered, we found little evidence that non-selective forces have significantly contributed to this clustering.

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