Divergent Mating Systems and Parental Conflict as a Barrier to Hybridization in Flowering Plants

Parental conflicts can lead to antagonistic coevolution of the sexes and of parental genomes. Within a population, the resulting antagonistic effects should balance, but crosses between populations can reveal conflict. Parental conflict is less intense in self‐pollinating plants than in outcrossers because outcrossing plants are pollinated by multiple pollen donors unrelated to the seed parent, while a self‐pollinating plant is primarily pollinated by one individual (itself). Therefore, in crosses between plants with differing mating systems, outcrossing parents are expected to “overpower” selfing parents. We call this the weak inbreeder/strong outbreeder (WISO) hypothesis. Prezygotically, such overpowering can alter pollination success, and we argue that our hypothesis explains a common pattern of unilateral incompatibility, in which pollen from self‐incompatible populations fertilizes ovules of self‐compatible individuals but the reciprocal cross fails. A postzygotic manifestation of overpowering is aberrant seed development due to parent‐of‐origin effects such as genomic imprinting. We evaluate evidence for the WISO hypothesis by reviewing published accounts of crosses between plants of different mating systems. Many, but not all, of such reports support our hypothesis. Since parental conflicts can perturb fertilization and development, such conflicts may strengthen reproductive barriers between populations, contributing to speciation.Organismic and Evolutionary Biolog

The evolution of competition and policing: opposing selection within and among groups

<p>Abstract</p> <p>Background</p> <p>Although selection favors exploitative competition within groups, a group of hypercompetitive individuals may be less productive than a cooperative group. When competition is costly for group fitness, among-group selection can favor groups with 'policing' individuals who reduce within-group competition at a cost to their own fitness, or groups of individuals who restrain their competitive intensity ('self policing'). We examine these possibilities in a series of explicit population-genetic models.</p> <p>Results</p> <p>By comparing results from models of half and full sib structured populations, we find that increased relatedness increases the strength of among-group selection against competition genotypes, and increases the strength of among group selection favoring policing genotypes. However, the strength of selection favoring costly policing behavior also increases with increased levels of competition. When levels of competition and policing feedback on one another, groups with lower levels of relatedness can favor higher levels of costly policing.</p> <p>Conclusion</p> <p>The result of the joint selection on policing and competition leads to results different from those based on the evolution of policing alone. Our model makes 'long term' predictions equivalent to those of optimization models, but we also show the existence of protected polymorphisms of police and civilians, as well as competitors and non-competitors.</p

Patterns of genetic variation in a prairie wildflower, Silphium integrifolium, suggest a non-prairie origin and locally adaptive variation

PREMISE: Understanding the relationship between genetic structure and geography provides information about a species’ history and can be used for breeding and conservation goals. The North American prairie is interesting because of its recent origin and subsequent fragmentation. Silphium integrifolium, an iconic perennial American prairie wildflower, is targeted for domestication, having undergone a few generations of improvement. We present the first application of population genetic data in this species to address the following goals: (1) improve breeding by characterizing genetic structure and (2) identify the species geographic origin and potential targets and drivers of selection during range expansion. METHODS: We developed a reference transcriptome as a genotyping reference for samples from throughout the species range. Population genetic analyses were used to describe patterns of genetic variation, and demographic modeling was used to characterize potential processes that shaped variation. Outlier scans for selection and associations with environmental variables were used to identify loci linked to putative targets and drivers of selection. RESULTS: Genetic variation partitioned samples into three geographic clusters. Patterns of variation and demographic modeling suggest that the species origin is in the American Southeast. Breeding program accessions are from the region with lowest observed genetic variation. CONCLUSIONS: This prairie species did not originate within the prairie. Breeding may be improved by including accessions from outside of the germplasm founding region. The geographic structuring and the identified targets and drivers of adaptation can guide collecting efforts toward populations with beneficial agronomic traits

Mating system variation in hybrid zones: Facilitation, barriers and asymmetries to gene flow

Plant mating systems play a key role in structuring genetic variation both within and between species. In hybrid zones, the outcomes and dynamics of hybridization are usually interpreted as the balance between gene flow and selection against hybrids. Yet, mating systems can introduce selective forces that alter these expectations; with diverse outcomes for the level and direction of gene flow depending on variation in outcrossing and whether the mating systems of the species pair are the same or divergent. We present a survey of hybridization in 133 species pairs from 41 plant families and examine how patterns of hybridization vary with mating system. We examine if hybrid zone mode, level of gene flow, asymmetries in gene flow and the frequency of reproductive isolating barriers vary in relation to mating system/s of the species pair. We combine these results with a simulation model and examples from the literature to address two general themes: (i) the two‐way interaction between introgression and the evolution of reproductive systems, and (ii) how mating system can facilitate or restrict interspecific gene flow. We conclude that examining mating system with hybridization provides unique opportunities to understand divergence and the processes underlying reproductive isolation

Mating system variation in hybrid zones: Facilitation, barriers and asymmetries to gene flow

Plant mating systems play a key role in structuring genetic variation both within and between species. In hybrid zones, the outcomes and dynamics of hybridization are usually interpreted as the balance between gene flow and selection against hybrids. Yet, mating systems can introduce selective forces that alter these expectations; with diverse outcomes for the level and direction of gene flow depending on variation in outcrossing and whether the mating systems of the species pair are the same or divergent. We present a survey of hybridization in 133 species pairs from 41 plant families and examine how patterns of hybridization vary with mating system. We examine if hybrid zone mode, level of gene flow, asymmetries in gene flow and the frequency of reproductive isolating barriers vary in relation to mating system/s of the species pair. We combine these results with a simulation model and examples from the literature to address two general themes: (1) the two-way interaction between introgression and the evolution of reproductive systems, and (2) how mating system can facilitate or restrict interspecific gene flow. We conclude that examining mating system with hybridization provides unique opportunities to understand divergence and the processes underlying reproductive isolation

Not Just a Theory--The Utility of Mathematical Models in Evolutionary Biology

Progress in science often begins with verbal hypotheses meant to explain why certain biological phenomena exist. An important purpose of mathematical models in evolutionary research, as in many other fields, is to act as “proof-of-concept” tests of the logic in verbal explanations, paralleling the way in which empirical data are used to test hypotheses. Because not all subfields of biology use mathematics for this purpose, misunderstandings of the function of proof-of-concept modeling are common. In the hope of facilitating communication, we discuss the role of proof-of-concept modeling in evolutionary biology

PENINGKATAN KETERAMPILAN MENULIS TEKS EKSPOSISI MELALUI PENGGUNAAN STRATEGI PEMBELAJARAN THINK TALK WRITE DAN MEDIA AUDIO VISUAL ( Penelitian Tindakan Kelas pada Siswa Kelas X IPS 2 SMA N 1 Surakarta Tahun Pelajaran 2017/2018)

Yustina Dwinuryati.2017. Peningkatan Keterampilan menulis Teks Eksposisi melalui Penggunaan Strategi Pembelajaran Think, Talk, Write dan Media Audio Visual (Penelitian Tindakan Kelas pada Siswa Kelas X IPS 2 SMA N 1 Surakarta Tahun Pelajaran 2017/2018). Tesis. Pembimbing: Prof. Dr. Andayani, M.Pd. Kopembimbing: Prof. Dr. Retno Winarni, M.Pd. Program Studi Magister Pendidikan Bahasa Indonesia, Fakultas Keguruan dan Ilmu Pendidikan, Universitas Sebelas Maret Surakarta. ABSTRAK Keterampilan menulis merupakan keterampilan berbahasa tingkat tinggi dan harus diajarkan kepada siswa di Sekolah Menengah Atas. Salah satu keterampilan menulis yang harus diajarkan kepada siswa kelas X sesuai Kurikulum 2013 Revisi adalah menulis teks eksposisi. Pembelajaran keterampilan menulis teks eksposisi di kelas X IPS2 SMA N 1 Surakarta mengalami permasalahan baik dari sisi motivasi belajar maupun keterampilan menulis siswa. Penelitian ini bertujuan untuk meningkatkan: (1) motivasi belajar menulis teks eksposisi siswa kelas X IPS 2 SMA Negeri 1 Surakarta dengan strategi pembelajaran think talk write dan penggunaan media audio visual dan (2) keterampilan menulis teks eksposisi siswa kelas X IPS 2 SMA Negeri 1 Surakarta dengan strategi pembelajaran think talk write dan media audio visual. Strategi penelitian berupa Penelitian Tindakan Kelas. Data penelitian bersumber dari proses pembelajaran, informan, hasil tes menulis teks eksposisi, dan dokumen. Teknik pengumpulan data dengan pengamatan, kajian dokumen, wawancara, dan tes. Uji validitas data menggunakan teknik triangulasi sumber data dan triangulasi metode. Teknik analisis data menggunakan teknik deskriptif komparatif dan analisis kritis. Hasil penelitian menunjukkan bahwa penerapan strategi pembelajaran think, talk, write dan penggunaan media audio visual pada siswa kelas X IPS2 SMA N I Surakarta dapat meningkatkan motivasi belajar dan keterampilan menulis teks eksposisi dari siklus 1 ke siklus 2. Hal itu dibuktikan adanya perubahan dan peningkatan motivasi belajar dan keterampilan menulis teks eksposisi siswa: (1) motivasi siswa meningkat dari siklus 1 sebesar 68% menjadi 82% pada siklus 2 dan (2) keterampilan menulis teks eksposisi meningkat dari siklus 1 sebesar 76% meningkat menjadi 88% pada siklus 2. Kata kunci: teks eksposisi, motivasi, strategi think talk write, audio visua

Analysis of ancestry heterozygosity suggests that hybrid incompatibilities in threespine stickleback are environment dependent

Hybrid incompatibilities occur when interactions between opposite ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are “intrinsic,” meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis using sequence data are scarce. In this article, we compiled genetic data for F(2) hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (seminatural experimental ponds) or the laboratory (aquaria). Because selection against incompatibilities results in elevated ancestry heterozygosity, we tested the prediction that ancestry heterozygosity will be higher in pond-raised fish compared to those raised in aquaria. We found that ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria. Additional analyses support a phenotypic basis for incompatibility and suggest that environment-specific single-locus heterozygote advantage is not the cause of selection on ancestry heterozygosity. Our study provides evidence that, in stickleback, a coarse—albeit indirect—signal of environment-dependent hybrid incompatibility is reliably detectable and suggests that extrinsic incompatibilities can evolve before intrinsic incompatibilities