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Phylogenies are a ubiquitous visual representation of core concepts in evolutionary biology and it is important that students develop an ability to read and correctly interpret these diagrams. However, as with any representation of complex disciplinary information, learning to correctly interpret phylogenies can be challenging, requiring that a diversity of educational strategies be deployed. Representational competence is the ability to develop and effectively use abstract representations. Accurately interpreting a phylogenetic tree as a presentation of evolutionary relationships requires that students develop general representational competence as well as knowledge of specific technical aspects of tree interpretation, such as knowing the graphical components of trees and what they represent. Here, we report on the development of a basic diagnostic tool of students' representational competence and technical skills with phylogenies, the Basic Evolutionary Tree-Thinking Skills Instrument (BETTSI). This short, multiple-choice instrument was designed to provide instructors with a quick diagnostic of students' ability to read and interpret phylogenies. It has been checked for reliability and validity and provides a convenient formative and summative assessment of students' understanding of evolutionary trees.

Students often have limited understanding of the major innovations in plant evolution. We developed a card sorting activity based on tree thinking that is suitable for students with a wide range of abilities and experience. Through this activity, students learn how scientists organize taxa into biologically meaningful, natural groups that illustrate important events in terrestrial plant evolution. The activity corresponds to several NGSS standards and is suitable for use in classroom or laboratory settings and as a public educational outreach activity. The Botanical Phylo-Card Game addresses several components of Next Generation Science Standards (NGSS Lead States, 2013) such as Inheritance/Variation in Traits (3-LS3-1, HS-LS3-1, HS-LS4-2) and Natural Selection/Evolution (MS-LS4-2, HS-LS4-1). The game involves disciplinary core ideas about biodiversity, evolution, and common ancestry; crosscutting concepts regarding identification and interpretation of patterns; and scientific practices of constructing explanations and engaging in arguments from evidence that can guide individualized implementation and assessment of the activity by different instructors.

PREMISE OF THE STUDY Bet-hedging strategies maximize long-term geometric fitness at the cost of reduced arithmetic fitness by offsetting different mortality risks. Heterocarpic systems accomplish bet-hedging through the production of two or more fruit types that vary in dormancy and dispersal ability. It is unknown whether heterocarpy also offsets predispersal mortality risks. To address this question, we investigated whether heterocarpy in Grindelia ciliata (Asteraceae) also offsets mortality risks posed by a seed predator Schinia mortua (Noctuidae) to increase plant fitness. METHODS We conducted two manipulative experiments to quantify critical life history components of this plant-insect interaction. We measured predispersal achene mortality from herbivory, postdispersal achene mortality in the seed bank, and seedling emergence. These measurements were then used in deterministic models to evaluate evolutionary consequences of predispersal seed mortality in G. ciliata. KEY RESULTS Dormant achene types were less vulnerable to herbivory but more susceptible to mortality in the seed bank due to delayed seed emergence. Nondormant achene types experienced high predispersal mortality but low seed bank mortality due to rapid germination. Our herbivore-dependent model improved fit between observed and expected proportions of dormant and nondormant G. ciliata achenes and showed that heterocarpy could evolve in the absence of postgermination mortality. CONCLUSIONS Our study provides empirical support of how predispersal herbivory can be equally important to postdispersal seed mortality risks in the evolution and maintenance of a heterocarpic reproductive system and expands understanding of how bet-hedging theory can be used to understand this unique reproductive strategy.

Seed mortality due to low winter temperatures has been proposed as an explanation for the lack of seedling recruitment in natural populations of the rare riparian species Alnus maritima, but other factors such as the absence of essential root symbionts or canopy clearing disturbances could also limit establishment of new individuals. We investigated whether any of these factors could be identified as preventing recruitment into existing seaside alder populations. Stratification studies showed that not only can seeds withstand low temperatures, longer periods of cold stratification promote earlier seed germination and expand the temperature range for germination. Root microbiome studies unexpectedly found that seedlings inoculated with the native microbiome prior to planting had lower survival compared to uninoculated individuals, and uninoculated individuals declined in survivorship after natural inoculation in the field. Canopy disturbance by burning or clipping vegetation promoted neither seedling growth nor survival initially, with seedling survival lower in burned plots due to the release of an aggressively growing competitor. Our results show that physiological stress by microbial symbionts and competition with other species are likely primary limiting factors—more so than seed mortality from low temperatures—and should be the focus of future conservation efforts.

Effective conservation requires an understanding of the genetic interactions among populations and individuals of a species, particularly those with fragmented, isolated distributions. Alnus maritima (seaside alder) is a rare tree species with an extremely fragmented distribution of highly isolated populations in the Delmarva Peninsula, Georgia, and Oklahoma. We conducted a mating system study to estimate the outcrossing rate, inbreeding coefficient, biparental inbreeding rate, and correlation of paternity in progeny from a Georgia and an Oklahoma population to investigate the effects of isolation on the A. maritima mating system. Data from nine microsatellite loci showed similarly high multilocus outcrossing rates in both populations (tm = 0.94). Individual tree outcrossing rates were also high (tm = 0.873–1.047). There was no significant biparental inbreeding in either population, but there was significantly higher correlated paternity in the Oklahoma population. Results showed the high out...

Small, isolated populations are prone to genetic drift and high levels of inbreeding that can threaten their long-term survival. Alnus maritima persists exclusively in three groups of small, highly disjunct, regional populations in the Delmarva Peninsula, Georgia, and Oklahoma. Trees in the three regions are recognized as separate subspecies. Microsatellite markers were used to measure fine-scale population genetic diversity and structure (1) within and among regions and (2) within and among populations in each region. Compared to a previous study utilizing allozymes, microsatellite data show higher levels of variation, lower levels of inbreeding, but similar levels of genetic differentiation among regions. Significant genetic differentiation was detected among regions and among distinct populations within regions. Genetic differentiation was significantly correlated with geographic distance among regional populations, but not among populations within regions. Populations, therefore, likely represent fragments of formerly extensive networks of populations that have decayed and retracted due to competition with other species better adapted to the shadier habitats of late-succession environments. The unique genetic features of populations within different regions should be considered as part of future conservation efforts.

We isolated and characterized 19 microsatellite loci from the endangered seaside alder, Alnus maritima. Loci were screened in 24 individuals of A. maritima and four individuals of its congener the hazel alder, A. serrulata. The number of alleles per locus ranged from 2 to 6, observed heterozygosity ranged from 0 to 0.952, and the probability of identity values ranged from 0.126 to 0.850. These new loci provide tools for characterizing the population genetics of this rare tree.

Alnus maritima and Alnus serrulata are riparian shrubs that occur in similar habitats in the southern and eastern United States. Alnus serrulata is abundant throughout this range, but A. maritima is rare, occurring only in small populations in Oklahoma and Georgia and on the Delmarva Peninsula. Alnus maritima is more resistant than A. serrulata to water and temperature stresses, but the degree to which insolation influences the restricted distribution of A. maritima is unknown. Our goals were to characterize the shade tolerance of A. maritima and A. serrulata and determine whether differences in shade tolerance could help explain the differing ecological success of the two species. Measurements in nature showed that leaves of A. serrulata have greater concentrations of chlorophyll than do leaves of A. maritima, and a greater percentage of A. serrulata inhabit shaded sites. Two experiments evaluating the resistance of seedlings to light‐deficit stress revealed that A. maritima had a greater photosynthetic ...

We conducted a population genetic analysis of the heterocarpic species Heterotheca subaxillaris (Asteraceae, camphorweed) to determine whether there are mating system and, consequently, genotypic differences between ray and disc achene pools that correspond to ecological differences between achene morphs. No significant differences in levels of genetic diversity were detected between ray and disc achene pools of H. subaxillaris. A mixed mating system was measured overall ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $tm_{\mat...

Dimorphic ray and disc achenes of Prionopsis ciliata (Asteraceae) were compared to determine whether ecological and genetic differences exist that correspond to structural differences between achene morphs. Ray achenes were significantly heavier and took a significantly longer time to germinate than disc achenes, which is indicative of differing dispersal and demographic functions between achene morphs. Significant heterozygote deficiency was detected in ray and disc achene seed pools. Mean observed heterozygosity across all populations and within two populations was significantly greater in the disc achene pool than in the ray achene pool. FIT and FIS were significantly higher and GST was significantly lower in the ray achene pool than the disc achene pool. Overall, ray and disc florets were predominantly self‐fertilized. Significant differences in outcrossing rates were detected between ray and disc florets within five populations. The results do not indicate a clear relationship between ecological func...

Androecium development and gynoecium development were compared among hermaphroditic flowers from nonfruiting (NF) and low-fruiting (LF) trees and female flowers from high-fruiting (HF) trees of gynodioecious Ocotea tenera Mez & J.D. Smith ex Mez. Dramatic qualitative differences in androecium development were identified between gender classes. Anthers in all flowers initiated microsporogenesis, with flowers from NF and LF trees eventually producing pollen, although some pollen from LF trees was slightly malformed. In anthers from HF trees, pollen development terminated after microspore tetrads developed, and the immature pollen grains eventually degenerated. Allometric relationships between flower growth and gynoecium growth differed among gender classes, with flowers from HF trees having a significantly greater slope. Allometric relationships between androecium and whole-flower growth were not different, but androecium size was reduced in female flowers. We argue that the gene, or genes, causing abortion...

The variant simian immunodeficiency virus termed SIVsmmPBj14 induces a rapidly fatal disease in pig-tailed macaques. The acute pathogenic effects of this virus appear to be associated with at least twoin vitrocharacteristics: the ability to induce lymphocyte proliferation; and the ability to replicate in unstimulated PBMC. Two of the amino acids in Nef of PBj14 (the No. 17 residue, tyrosine, and the No. 18 residue, glutamic acid) appear to be linked to the virus' ability to induce lymphocyte activation. To further study the effects of these amino acids on PBj14-induced pathogenesis, we generated two mutant viruses from our molecular clone, PBj6.6, containing either changes in both the No. 17 and No. 18 residues (termed PBj6.6YE-RQ), or a single change in the No. 17 residue (termed PBj6.6Y-R).In vitroanalyses of these viruses showed that while their replicative abilities in stimulated peripheral blood mononuclear cells (PBMC) were altered, they still maintained the ability to replicate in unstimulated PBMC. Replication of these viruses in macrophage populations was impaired relative to the wild-type virus. Both mutant viruses were unable to induce proliferation of macaque PBMCin vitro.Virus derived from PBj6.6Y-R was unable to induce acute disease in macaques, but did maintain the ability to induce lymphopenia and intestinal lymphoid hyperplasia. These results show that the tyrosine-17 residue of Nef is linked to lymphocyte proliferation and disease development, but also suggest that the pathogenic characteristics of SIVsmmPBj14 are dependent upon multiple genetic determinants.

Progeny arrays of Ocotea tenera (Lauraceae), a gynodioecious tree endemic to Costa Rica, were electrophoretically surveyed for allozyme variation to estimate the outcrossing rate in the overall population and to test for differences in outcrossing rates between hermaphroditic and female trees. Multilocus outcrossing rate estimates across 3 yr indicated O. tenera predominantly outcrosses. However, significant heterogeneity in single-locus outcrossing rates was found among loci. Two loci (FeZ, Fe2) gave high outcrossing estimates, and a third locus (Gdh) gave much lower outcrossing estimates. Heterogeneity in Gdh pollen allele frequencies, consanguineous matings, and selection against homozygous zygote genotypes at the FeZ and Fe2 loci are factors contributing to the discrepancy in outcrossing rate estimates among loci. There were no differences in the mating systems of hermaphroditic and female trees, which suggests that factors beyond prevention of selffertilization may have also promoted the evolution of gynodioecy in O. tenera.

We studied the influence of avian seed dispersal on the structuring of genetic diversity in a population of a tropical tree, Ocotea tenera (Lauraceae). The seeds of O. tenera are principally dispersed by four, relatively specialized, fruit-eating bird species (emerald toucanets, keel-billed toucans, resplendent quetzals, and three-wattled bellbirds). We found high genetic diversity within the overall population and significant, nonrandom structuring of that diversity among subpopulations. Subpopulations contained members of several sibling groups, and most saplings within subpopulations were shown not to be the progeny of adult trees within the same subpopulation. Our data indicate that O. tenera subpopulations are founded with several seeds from few maternal families, and that this mode of establishment is an important determinant of population genetic architecture.

Comparisons of population genetic diversity between related rare and widespread species provide valuable insights to the consequences of rarity and are critical for conservation planning. Population genetic diversity of A. maritima, a rare species, was compared with its common, widespread congener A. serrulata to evaluate the impacts of small population size and high isolation on genetic diversity in A. maritima and to provide population genetic data to be used in conservation planning for A. maritima. Genetic data were also used to evaluate whether the disjunct distribution of A. maritima was due to range reduction or anthropogenic dispersal. Genetic diversity was lower in A. maritima (H(e) = 0.217) than in A. serrulata (H(e) = 0.268), and there is also higher inbreeding within A. maritima populations (f = 0.483) than A. serrulata populations (f = 0.269). The partitioning of genetic variation was also higher among A. maritima populations (Θ = 0.278), but not significantly different from that of A. serrulata (Θ = 0.197). Significant genetic differences among A. maritima populations support using local populations as seed sources for regional conservation efforts. The results also indicate that the highly disjunct distribution of A. maritima is due to natural range reduction in the past and not anthropogenic establishment of Oklahoma and Georgia populations.

We compared phloem characteristics of individual Pinus ponderosa attacked by the dwarf-mistletoe Arceuthobium vaginatum (Viscaceae) or by the beetle Dendroctonus ponderosae (Scolytidae) or by neither species. We quantified total nonstructural carbohydrates and a broad range of chemical elements for these three categories of trees. There were significant differences between trees parasitized by Arceuthobium, trees parasitized by Dendroctonus, and non-infected trees. Discriminant function analysis of trees attacked by either Arceuthobium or Dendroctonus correctly predicted group membership for 59 of 60 trees tested. Some of the differences detected may be induced, but many probably are not. Given that the accumulation of certain elements and compounds is under genetic control, and that both parasites often cause severe reductions in fitness, including death of their host, our results suggest that the two parasites may generate diversifying selection in ponderosa pine populations.

Genetic diversity in three species of Rhus was investigated using starch gel electro- phoresis. Rhus michauxii is a rare species endemic to North Carolina, whereas R. glabra and R. copallina are widespread. All three species are clonal, typically dioecious, woody shrubs. Forty-seven percent of the loci examined for R. michauxii were polymorphic, compared to 88% of the loci examined for both R. glabra and R. copallina. Mean genetic diversity (He) within populations of R. michauxii (0.05) was lower than the genetic diversity within populations of R. glabra and R. copallina (0.15 for both species). Mean number of multilocus genotypes per population was lower for R. michauxii, 4.1, versus the other two species, R. glabra, 27.5 and R. copallina, 26.6. Genotypic diversity indices (DG) were 0.41, 0.95 and 0.95 for R. michauxii, R. glabra and R. copallina, respectively. The proportion of genetic diversity among populations (GST) was higher in R. michauxii (0.335) and R. copallina (0.301) than in R. glabra (0.198). Genetic identity values among the species ranged from 0.52-0.96, and grouped R. michauxii closely with R. glabra. Rhus glabra and R. copallina have levels of genetic diversity similar to wide ranging plant species with the same suite of life history characteristics. The lower level of genetic diversity in R. michauxii is characteristic of species with limited geographic distributions. The relatively high levels of genetic diversity seen among populations indicates that clonal repro- duction may play an important role in the genetic structuring of these species.

Tree thinking refers to an approach to evolution education that emphasizes reading and interpreting phylogenetic trees. We studied the relationship between introductory biology students’ tree-thinking ability and their acceptance of evolutionary theory. Comparisons between a semester in which interpretation of phylogenetic trees and related concepts were taught as stand-alone topics versus one in which tree thinking was used as an organizing framework for the course curriculum found significant increases in students’ ability to read and interpret trees in both semesters, but only in the tree thinking semester was there a significant increase in students’ scores on the Measure of the Acceptance of the Theory of Evolution (MATE) instrument. Over four additional semesters, the Tree Thinking Concept Inventory (TTCI) was used to assess students’ tree-thinking abilities before and after the course. We found that MATE posttest scores correlated with gains in tree-thinking ability. These increases in MATE posttest scores were predominantly due to students’ reporting greater acceptance of the scientific evidence supporting evolutionary theory. Increased acceptance of evolution in a tree-thinking versus non-tree-thinking semester and significant positive correlations between TTCI and MATE scores indicate there is a relationship between tree-thinking ability and acceptance of evolution. This result suggests that, as a framework to connect different forms of data and investigate a variety of biological phenomena, tree thinking can promote greater acceptance of the evidence and scientific validity of evolutionary theory in introductory biology students.