The genetic architecture of traits associated with the evolution of self-pollination in Mimulus.

Quantitative trait locus (QTL) mapping is a first step toward understanding the genetic basis of adaptive evolution and may also reveal reproductive incompatibilities unique to hybrids. In plants, the shift from outcrossing to self-pollination is common, providing the opportunity for comparisons of QTL architecture among parallel evolutionary transitions. We used QTL mapping in hybrids between the bee-pollinated monkeyflower Mimulus lewisii and the closely related selfer Mimulus parishii to determine the genetic basis of divergence in floral traits and flowering time associated with mating-system evolution, and to characterize hybrid anther sterility. We found a moderately polygenic and highly directional basis for floral size evolution, suggesting adaptation from standing variation or in pursuit of a moving optimum, whereas only a few major loci accounted for substantial flowering-time divergence. Cytonuclear incompatibilities caused hybrid anther sterility, confounding estimation of reproductive organ QTLs. The genetic architecture of floral traits associated with selfing in M. parishii was primarily polygenic, as in other QTL studies of this transition, but in contrast to the previously characterized oligogenic basis of a pollinator shift in close relatives. Hybrid anther sterility appeared parallel at the molecular level to previously characterized incompatibilities, but also raised new questions about cytonuclear co-evolution in plants.

Design principles for effective video-based professional development.

BACKGROUND: Most studies of teacher professional development (PD) do not rigorously test impact on teaching practice and student learning. This makes it difficult to define what is truly "effective." The Science Teachers Learning from Lesson Analysis (STeLLA) PD program, in contrast, was studied in a cluster randomized experimental design that examined impact on teaching practice and student learning. The STeLLA video-based PD (VbPD) program demonstrated significant impact, with high effect sizes, on elementary teachers' science teaching practice and their students' learning. Previously published reports provide details about research methods and findings but only broad sketches of the STeLLA program design and implementation. Deeper explorations of the STeLLA design principles can contribute evidence-based knowledge about the features of effective PD and enrich the existing but limited consensus model of effective PD. This article addresses the following questions:What design principles guided the development, implementation, leadership, and scaling up of a video-based PD program that had significant impact on student learning?What do the STeLLA design principles contribute to the existing knowledge base about effective video-based PD? RESULTS: Results from rigorous studies of the STeLLA program are summarized in this paper; details are reported elsewhere and included here as supplementary materials. This article is not a standard research results paper but instead describes the design principles guiding the development, implementation, leadership, and scaling up of the STeLLA VbPD program. CONCLUSIONS: The authors argue that this set of design principles is powerful for four reasons: 1) its demonstrated impact on teaching practice and student learning, 2) its strong theoretical and research foundations, 3) the stability and usefulness of the design principles as implemented in changing contexts over a 10-year period, and 4) the coherence and interconnectedness of the principles. The STeLLA VbPD design principles contribute to the field by empirically supporting and advancing the existing consensus model of effective PD. Further study can build on this effort to strengthen our understanding of effective PD based on evidence of impact on teaching practice and student learning.

AFLP phylogeny of Mimulus section Erythranthe and the evolution of hummingbird pollination.

Species in Mimulus section Erythranthe (monkeyflowers) have become model systems for the study of the genetic basis of ecological adaptations. In this study, we pursued two goals. First, we reconstructed the phylogeny of species in Erythranthe using both DNA sequences from the ribosomal DNA ITS and ETS and AFLPs. Data from rDNA sequences support the monophyly of the section, including M. parishii, but provide little support for relationships within it. Analyses using AFLP data resulted in a well-supported hypothesis of relationships among all Erythranthe species. Our second goal was to reconstruct ancestral pollination syndromes and ancestral states of individual characters associated with hummingbird-pollinated flowers. Both parsimony and likelihood approaches indicate that hummingbird pollination evolved twice in Erythranthe from insect-pollinated ancestors. Our reconstruction of individual characters indicates that corolla color and some aspects of corolla shape change states at the same point on the phylogenetic tree as the switch to hummingbird pollination; however, a switch to secretion of high amounts of nectar does not. Floral trait transformation may have been more punctuational than gradual.

Chromosomal rearrangements and the genetics of reproductive barriers in mimulus (monkey flowers).

Chromosomal rearrangements may directly cause hybrid sterility and can facilitate speciation by preserving local adaptation in the face of gene flow. We used comparative linkage mapping with shared gene-based markers to identify potential chromosomal rearrangements between the sister monkeyflowers Mimulus lewisii and Mimulus cardinalis, which are textbook examples of ecological speciation. We then remapped quantitative trait loci (QTLs) for floral traits and flowering time (premating isolation) and hybrid sterility (postzygotic isolation). We identified three major regions of recombination suppression in the M. lewisii × M. cardinalis hybrid map compared to a relatively collinear Mimulus parishii × M. lewisii map, consistent with a reciprocal translocation and two inversions specific to M. cardinalis. These inferences were supported by targeted intraspecific mapping, which also implied a M. lewisii-specific reciprocal translocation causing chromosomal pseudo-linkage in both hybrid mapping populations. Floral QTLs mapped in this study, along with previously mapped adaptive QTLs, were clustered in putatively rearranged regions. All QTLs for male sterility, including two underdominant loci, mapped to regions of recombination suppression. We argue that chromosomal rearrangements may have played an important role in generating and consolidating barriers to gene flow as natural selection drove the dramatic ecological and morphological divergence of these species.

Evolution of biogeographic disjunction between eastern Asia and eastern North America in Phryma (Phrymaceae).

This study examines molecular and morphological differentiation in Phryma L., which has only one species with a well-known classic intercontinental disjunct distribution between eastern Asia (EA) and eastern North America (ENA). Phylogenetic analysis of nuclear ribosomal ITS and chloroplast rps16 and trnL-F sequences revealed two highly distinct clades corresponding to EA and ENA. The divergence time between the intercontinental populations was estimated to be 3.68 ± 2.25 to 5.23 ± 1.37 million years ago (mya) based on combined chloroplast data using Bayesian and penalized likelihood methods. Phylogeographic and dispersal-vicariance (DIVA) analysis suggest a North American origin of Phryma and its migration into EA via the Bering land bridge. Multivariate analysis based on 23 quantitative morphological characters detected no geographic groups at the intercontinental level. The intercontinental populations of Phryma thus show distinct molecular divergence with little morphological differentiation. The discordance of the molecular and morphological patterns may be explained by morphological stasis due to ecological similarity in both continents. The divergence of Phryma from its close relatives in the Phrymaceae was estimated to be at least 32.32 ± 4.46 to 49.35 ± 3.18 mya.

Redefining Phrymaceae: the placement of Mimulus, tribe Mimuleae, and Phryma.

Chloroplast trnL/F and nuclear ribosomal ITS and ETS sequence data were used to analyze phylogenetic relationships among members of tribe Mimuleae (Scrophulariaceae) and other closely related families in Lamiales. The results of these analyses led to the following conclusions. (1) The Australian genera Glossostigma and Peplidium and the taxonomically isolated Phryma join four genera of tribe Mimuleae to form a well-supported clade that is distinct from other families in the Lamiales. We refer to that clade as the subfamily Phrymoideae. (2) The genera Mazus and Lancea (tribe Mimuleae) together form a well-supported clade that we recognize as the subfamily Mazoideae. Mazoideae is weakly supported as sister to Phrymoideae. We assign Mazoideae and Phrymoideae to a redefined family Phrymaceae. (3) Mimulus is not monophyletic, because members of at least six other genera have been derived from within it. In light of the molecular evidence, it is clear that species of Phrymaceae (about 190 species) have undergone two geographically distinct radiations; one in western North America (about 130 species) and another in Australia (about 30 species). Phylogenetic interpretations of morphological evolution and biogeographical patterns are discussed.

Patterns of evolution in western North American Mimulus (Phrymaceae).

A well-supported phylogeny is presented from both chloroplast DNA (the trnL/F region) and two regions of nuclear rDNA (ITS [internal transcribed spacer] and ETS [external transcribed spacer]) with nearly complete sampling for Mimulus (Phrymaceae) in western North America. Three separate genera are derived from within the clade that contains all the Mimulus species in western North America. The taxonomic status of the proposed sections of Mimulus and the relationships of many taxonomically difficult species are considered with observations on morphological evolution. Discordance between data sources provides support for the hypothesis that M. evanescens is a hybrid between M. latidens and M. breviflorus. In two major clades (Eunanus and Diplacus), patterns of genetic variation do not match the current taxonomy. The clustering of taxa in Eunanus is strongly associated with geographic distributions. Mimulus aurantiacus sensu Thompson, M. nanus, and M. floribundus are found to be progenitor species to other species that appear to be derived from within them. Polyploidy and aneuploidy events are clustered near the tips of the phylogeny. Thus, these two mechanisms are concluded to have played a relatively small role in the evolution of persistent lineages in Mimulus. The phylogenetic distribution of rare taxa is also examined.