American Journal of Botany

PREMISE: Phylogeographical studies are fundamental for understanding factors that influence the spatial distribution of genetic lineages within species. Population expansions and contractions, distribution shifts, and climate changes are among the most important factors shaping the genetic compositions of populations. METHODS: We investigated the phylogeography of an endemic oak, Quercus mexicana (Fagaceae), which has a restricted distribution in northeastern Mexico along the Sierra Madre Oriental and adjacent areas...

PREMISE: In 1879, Dr. William Beal buried 20 glass bottles filled with seeds and sand at a single site at Michigan State University. The goal of the experiment was to understand seed longevity in the soil, a topic of general importance in ecology, restoration, conservation, and agriculture, by periodically assaying germinability of these seeds over 100 years. The interval between germination assays has been extended and the experiment will now end after 221 years, in 2100. METHODS: We dug up the 16th bottle in April 2021 and attempted to germinate the 141-year-old seeds it contained...

PREMISE: The evolution of carnivorous pitcher traps across multiple angiosperm lineages represents a classic example of morphological convergence. Nevertheless, no comparative study to-date has examined pitcher evolution from a quantitative morphometric perspective. METHODS: In the present study, we used comparative morphometric approaches to quantify the shape space occupied by Heliamphora pitchers and to trace evolutionary trajectories through this space to examine patterns of divergence and convergence within the genus...

PREMISE OF THE STUDY: There is mounting evidence that age matters in plant demography, but also indications that relationships between age and demographic rates may vary significantly among species. Age-based plant demographic data, however, is time-consuming to collect, and still lacking for most species, and little is known about general patterns across species or what may drive differences. METHODS: We used individual birth and death records for twelve Rhododendron species from botanical gardens and conducted Bayesian survival trajectory analyses to assess how mortality changed with age...

PREMISE: Bryophytes form a major component of terrestrial plant biomass, structuring ecological communities in all biomes. Our understanding of the evolutionary history of hornworts, liverworts and mosses has been significantly reshaped by inferences from molecular data, which have highlighted extensive homoplasy in various traits and repeated bursts of diversification. However, the timing of key events in the phylogeny, patterns and processes of diversification across bryophytes remain unclear...

PREMISE: Leaf subepidermal secretory cavities are a notable trait in Myrtaceae. The formation of these secretory structures is still controversial because of the lack of consensus on their ontogeny among authors. The knowledge about the nature of the compounds present in these cavities has grown over the last few years, demonstrating that terpenoid-rich oils are not their unique content. These two points are the focus of this study, which investigates the ontogeny, structure and the contents of secretory cavities in Neotropical Myrtaceae...

PREMISE: The interaction between ecological and evolutionary processes has been recognized as an important factor shaping the evolutionary history of species. Some authors have proposed different ecological and evolutionary hypotheses concerning the relationships between plants and their pollinators; a special case is the interaction and suspected coevolution among Agave spp. and their main pollinators, the Leptonycteris bats. Agave spp. have, in general, a pollination syndrome compatible with chiropterophily including floral shape and size, nocturnal nectar production, and nectar quality and sugar concentration...

PREMISE: Dominant in many ecosystems around the world, clonal plants can reach considerable ages and sizes. Due to their modular growth patterns, individual clonal plants (genets) can consist of many subunits (ramets). Since single ramets do not reflect the actual age of genets, the ratio between genet size (radius) and longitudinal annual growth rate (LAGR) of living ramets is often used to approximate the age of clonal plants. However, information on how the LAGR changes along ramets and how LAGR variability may affect age estimates of genets is still limited...

One of the most remarkable innovations in the evolution of vascular plants is secondary growth: the developmental process by which plants grow thicker. The textbook illustration of secondary growth--a core of secondary xylem surrounded by a sheath of secondary phloem--is generated through a cylindrical meristem called the vascular cambium (Fig. 1A). This modality is conserved across thousands of species, providing mechanical support for ever-elongating shoots, and a regenerative source of vascular tissues to feed the ever-expanding crown of branches and leaves This article is protected by copyright...

PREMISE: Species delimitation is an integral part of evolution and ecology and is vital in conservation science. However, in some groups species delimitation is difficult, especially where ancestral relationships inferred from morphological or genetic characters are discordant, possibly due to a complicated demographic history (e.g., recent divergences between lineages). Modern genetic techniques can take account of complex histories to distinguish species at a reasonable cost and are increasingly used in numerous applications...

One of the most fascinating phenomena in evolutionary biology is the rapid evolution of genes with conserved functions across the tree of life. Because the cellular and organismal development processes are highly conserved across eukaryotes, a naive evolutionary expectation is that the genes involved in those processes would also be under high selective constraint and evolve extremely slowly. However, we now know that evolutionarily young genes can rapidly acquire crucial viability functions and even evolutionarily old genes can have unexpected levels of rapid evolution within specific lineages (Talbert et al...

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PREMISE OF THE STUDY: Cultivated species and their wild relatives often hybridize in the wild and crop-wild hybrids can survive and reproduce in some environments. However, it is unclear whether cultivar alleles are permanently incorporated into the wild genomes or whether they are purged by natural selection. This question is key to accurately assessing the risk of escape and spread of cultivar genes into wild populations. METHODS: We used genomic data and population genomic methods to study hybridization and introgression between cultivated and wild carrot (Daucus carota L...

PREMISE OF THE STUDY: Paubrasilia echinata (Lam.) Gagnon, H. C. Lima & G. P. Lewis ("Pau Brasil") is the national tree of Brazil, an endangered species endemic to the Brazilian Atlantic Forest. The wide distribution, spanning over 2000 km, matches extensive plasticity in leaf morphology. Three morphotypes are commonly identified based on leaf size but it is unclear if they represent distinct taxa or a single polymorphic species. This study aims to clarify the taxonomic position of the three morphotypes to inform conservation decisions...

PREMISE: What maintains mixed mating is an evolutionary enigma. Cleistogamy, the production of both potentially outcrossing chasmogamous, and obligately selfing cleistogamous flowers on the same individual plant, is an excellent system to study the costs of selfing. Inbreeding depression can prevent the evolution of greater selfing within populations, and heterosis in crosses between populations may further tip the balance in favor of outcrossing. Few empirical estimates of inbreeding depression and heterosis in the same system exist for cleistogamous species...

PREMISE: Under uncertain pollinator visit conditions, plants often exhibit long flowering periods and generalized pollination systems. Flowering of the gynodioecious shrub Daphne jezoensis occurs early in spring in cool temperate forests. Pollination by nocturnal moths is expected due to tubular-shaped flowers with sweet fragrance and nectar. However, the effectiveness of nocturnal moths under cool conditions remains unknown. In this study, we evaluated the relative importance of diurnal and nocturnal visitors as pollinators in early spring...

PREMISE: Cacti are characteristic elements of the Neotropical flora and of major interest for biogeographic, evolutionary, and ecological studies. Here we test global biogeographic boundaries for Neotropical Cactaceae using specimen-based occurrences coupled with data from visual observations, as a means to tackle the known collection biases in the family. METHODS: Species richness and record density were assessed for preserved specimens and human observations and a bioregional scheme tailored to Cactaceae was produced using the interactive web application Infomap Bioregions based on data from 261,272 point records cleaned through automated and manual steps...

PREMISE OF THE STUDY: Chaetopeltidales is a small understudied order in the OCC clade of the green algal class Chlorophyceae, slowly expanding by occasional discoveries of novel algae. Here we demonstrate that hitherto unrecognized chaetopeltidaleans exist also among previously described but neglected and misclassified species. METHODS: The strain Characium acuminatum SAG 40.91, with previous preliminary evidence for its affinities to the OCC clade, was investigated with light and electron microscopy to characterize its morphology and ultrastructure...

PREMISE OF THE STUDY: Floral scent, usually consisting of multiple compounds, is a complex trait and its role in pollinator attraction has received increasing attention. However, it is difficult to disentangle the effect of individual floral scent compounds due to the complexity of isolating the effect of single compounds by traditional methods. METHODS: Using available quasi-isogenic lines (qILs) generated as part of the original mapping of two floral scent volatile-related loci, CNL1 (benzaldehyde) and TPS2 (β-ocimene), in Capsella, we have generated four genotypes that should only systematically differ in these two compounds...

PREMISE: Generalized mutualisms have diverse outcomes influenced by partner traits. Although less studied, intraspecific variation of bee traits can be crucial for pollination. We investigated the role of intraspecific body size and behavioral trait variations of bumblebee Bombus morio on the pollination of a buzz-pollinated legume species, Chamaecrista latistipula. METHODS: To explore the impact of traits in B. morio (body size and behavior) on C. latistipula pollination, we conducted focused observations of visits to virgin flowers and quantified the removal and deposition of pollen (pollination performance), in addition to fruit and seed formation (reproductive fitness)...