The evolution of self-compatibility and its genetic consequences in Leavenworthia alabamica (Brassicaceae)

Thesis (PhD) - Indiana University, Ecology & Evolutionary Biology, 2005The evolution of self-fertilization from the outcrossing condition is a common transition in flowering plants which strongly alters the genetic structure of populations. In general, it is thought that self-fertilization may evolve in response to its innate transmission advantage or pollen limitation, and that this mating system may endanger the long-term viability of populations through mutation accumulation. The purpose of this dissertation was to evaluate the costs and benefits of self-fertilization in the species Leavenworthia alabamica, which exhibits variation among populations in the presence or absence of self-incompatibility. This variation in mating-system made it possible to directly answer the following questions: 1) what are the agents of selection driving the fixation of self-compatibility alleles in populations?; 2) does inbreeding depression selectively maintain self-incompatibility in nature, and if so, what happens to these deleterious alleles following the transition to self-compatibility?; and 3) does a history of self-fertilization cause populations to accumulate deleterious mutations and potentially experience extinction? In L. alabamica, self-incompatibility predominates in large, stable and geographically central populations. In contrast, self-compatibility and adaptations for self-fertilization evolve in the small, disturbed, and geographically peripheral populations of this species. A field experiment shows that self-compatible genotypes are selectively favored in all environments, but that reductions in mate availability likely favor their spread and fixation in the smallest of populations. This model of mating-system evolution is supported by the nearly complete or complete loss of sequence diversity in all of the independently derived self-compatible taxa of Leavenworthia. Inbreeding depression plays a role in the maintenance of self-incompatibility in L. alabamica, and the spread and fixation of self-compatibility alleles purge populations of these strongly deleterious mutations. Nearly all of the populations of this species do not suffer from a substantial local drift load caused by the fixation of mildly deleleterious mutations. That being said, the oldest and most isolated self-fertilizing population showed a dramatic increase in fitness following crosses between populations. Overall, these results suggests that mutation accumulation may eliminate highly inbreeding plant populations as the stochastic fixation of mildly deleterious mutations depresses fitness over many generations

Tawuran antar pelajar: penelitian di SMK Diponegoro Kecamatan Ploso dan SMK Dwijaya Bhakti Jombang

Ada dua persoalan yang dikaji dalam penelitian ini, yaitu: (1) Faktor apa saja yang menyebabkan terjadinya aksi tawuran antar pelajar di SMK Diponegoro Kecamatan Ploso dan SMK Dwijaya Bhakti Jombang; (2) Faktor apa yang paling dominan yang meyebabkan terjadinya tawuran antar pelajar. Adapun tujuan dari penelitian ini adalah untuk mengetahui apa saja faktor-faktor penyebab terjadinya tawuran antar pelajar dan faktor yang paing dominan penyebab terjadinya tawuran antar pelajar. Untuk mengungkap persoalan tersebut secara menyeluruh dan mendalam maka dalam penelitian ini menggunakan metode analisis deskriptif yang bersifat kualitatif dalam menganalisis data-data yang diperoleh dilapangan melalui observasi, interview dan dokumentasi. Kemudian data tersebut dianalisis dengan dasar teori Konflik Lewis A. Coser tentang adanya konflik yang dapat menimbulkan dampak positif terhadap kelompok dalam. Hal ini dimaksudkan adanya konflik yang dapat meningkatkan rasa solidaritas clan kebersamaan antara satu dengan yang lain karena faktor lingkungan keseharian mereka yang mengharuskan untuk ikut terlibat kedalam aksi tawuran antar pelajar, mereka bersatu untuk melindungi kelompok mereka dari siapapun yang mengganggu dan menyakiti anggota dalam kelompok yang sudah mereka bentuk. Dari hasil penelitian ini ditemukan bahwa (I) Faktor penyebab terjadinya tawuran antar pelajar adalah faktor lingkungan dan pergaulan, faktor membela teman, faktor balas dendam, faktor keluarga serta pengaruh perubahan zaman (2) Dari beberapa faktor yang telah dikemukakan faktor lingkungan merupakan faktor yang paling dominan dan paling berpangaruh terhadap terjadinya tawuran antar pelajar, karena baik dan buruknya tingkah laku remaja semua itu tidak akan lepas dari lingkungan tempat mereka beradaptasi dan menghabiskan waktu kesehariannya dengan teman-teman mereka

Negotiating the modern cross-class ‘model home’:domestic experiences in Basil Spence’s Claremont Court

This article investigates the spatial articulation of architecture and home through the exploration of current domestic experiences in Basil Spence’s Claremont Court housing scheme (1959-1962), Edinburgh. How architecture and home are both idealized and lived is the backdrop for a discussion that draws on the concept of “model home,” or physical representation of a domestic ideal. The article reads Claremont Court as an architectural prototype of the modern domestic ideal, before exploring its reception by five of its households through the use of visual methods and semistructured interviews. Receiving the model home involves negotiating between ideal and lived homes. Building on this idea, the article contributes with a focus on the spatiality of such reception, showing how it is modulated according to the architectural affordances that the “model home” represents. The article expands on scholarship on architecture and home with empirical evidence that argues the reciprocal spatiality of home

The evolution of dominance in sporophytic self-incompatibility systems. II. Mate availability and recombination

Sporophytic self-incompatibility (SSI) is a self-pollen recognition system that enforces outcrossing in plants. Recognition in SSI systems is typically controlled by a complex locus (S-locus) with separate genes that determine pollen and stigma specificity. Experimental studies show that S-alleles can be dominant, recessive, or codominant, and that the dominance level of a given S-allele can depend upon whether pollen or stigma specificity is examined. Here and in the companion paper by Llaurens and colleagues, the evolution of dominance in single-locus SSI is explored using numerical models and simulation. Particular attention is directed at factors that can cause S-allele dominance to differ in pollen versus stigma. The effect of recombination between the S-locus and modifier locus is also examined. The models predict that limitation in the number of compatible mates is required for the evolution of S-allele dominance in the stigma but not in the pollen. Tight linkage between the S-locus and modifier promotes the evolution of S-allele dominance hierarchies. Model results are interpreted with respect to published information on the molecular basis of dominance in SSI systems, and reported S-allele dominance relationships in a variety of species. These studies show that dominant S-alleles are more common in the pollen than in the stigma, a pattern that when interpreted in light of model predictions, suggests that mate limitation may be relatively infrequent in natural populations with SSI

data for: Hybrid breakdown is elevated near the historical cores of a species\u27 range

Data and code for the manuscript: Accumulation of hybrid incompatibilities reflects neutral genetic structure more strongly than climatic differentiation F1 and F2 fitness data from within and between population crosses of Campanula americana are in F1_fitness.xls and F2_fitness.xls files, respectively. Data used for multiple linear regression testing the effects of neutral genetic and climatic differentiation on hybrid breakdown are in multipleReg_input.xls. Prism climatic data used to calculate Mahalonobis environmental distances are in prism_annual.xls. Code for resampling fitness data to calculate standard deviation of hybrid breakdown within hybrid crosses is provided in \u27resample_fitness.R\u27. Code for the mutliple linear regression is provided in \u27multipleReg_code.R\u27 and code to calculate Mahalanobis D are in \u27Mahalanobis_Env_D.R\u27

Model source code

Contains C++ files used to model inbreeding depression in autotetraploid

Data from: Bottlenecks and inbreeding depression in autotetraploids

Inbreeding depression is dependent on the ploidy of populations and can inhibit the evolution of selfing. While polyploids should generally harbor less inbreeding depression than diploids at equilibrium, it has been unclear whether this pattern holds in non-equilibrium conditions following bottlenecks. We use stochastic individual based simulations to determine the effects of population bottlenecks on inbreeding depression in diploids and autotetraploids, in addition to cases where neo-autotetraploids form from the union of unreduced gametes. With a ploidy-independent dominance function based on enzyme kinetics, inbreeding depression is generally lower in autotetraploids for fully and partially recessive mutations. Due to the sampling of more chromosomes during reproduction, bottlenecks generally reduce inbreeding depression to a lesser extent in autotetraploids. All else being equal, population bottlenecks may have ploidy dependent effects for another reason – in some cases mating between close relatives temporarily increases inbreeding depression in autotetraploids by increasing the frequency of the heterozygous genotype harboring the most harmful mutations. When neo-autotetraploids are formed by few individuals, inbreeding depression is dramatically reduced, given extensive masking of harmful mutations following whole genome duplication. This effect persists as nascent tetraploids reach mutation-selection-drift balance, providing a transient period of permissive conditions favoring the evolution of selfing

Demographic signatures accompanying the evolution of selfing in Leavenworthia alabamica

The evolution of selfing from outcrossing is a common transition, yet little is known about the mutations and selective factors that promote this shift. In the mustard family, single-locus self-incompatibility (SI) enforces outcrossing. In this study, we test whether mutations causing self-compatibility (SC) are linked to the self-incompatibility locus (S-locus) in Leavenworthia alabamica, a species where two selfing races (a2 and a4) co-occur with outcrossing populations. We also infer the ecological circumstances associated with origins of selfing using molecular sequence data. Genealogical reconstruction of the Lal2 locus, the putative ortholog of the SRK locus, showed that both selfing races are fixed for one of two different S-linked Lal2 sequences, whereas outcrossing populations harbor many S-alleles. Hybrid crosses demonstrated that S-linked mutations cause SC in each selfing race. These results strongly suggest two origins of selfing in this species, a result supported by population admixture analysis of 16 microsatellite loci and by a population tree built from eight nuclear loci. One selfing race (a4) shows signs of a severe population bottleneck, suggesting that reproductive assurance might have caused the evolution of selfing in this case. In contrast, the population size of race a2 cannot be distinguished from that of outcrossing populations after correcting for differences in selfing rates. Coalescent-based analyses suggest a relatively old origin of selfing in the a4 race (∼150 ka ago), whereas selfing evolved recently in the a2 race (∼12-48 ka ago). These results imply that S-locus mutations have triggered two recent shifts to selfing in L. alabamica, but that these transitions are not always associated with a severe population bottleneck, suggesting that factors other than reproductive assurance may play a role in its evolution