Chloroplast DNA sequences are a primary source of data for plant molecular systematic studies. A few key papers have provided the molecular systematics community with universal primer pairs for noncoding regions that have dominated the field, namely trnL-trnF and trnK/matK. These two regions have provided adequate information to resolve species relationships in some taxa, but often provide little resolution at low taxonomic levels. To obtain better phylogenetic resolution, sequence data from these regions are often coupled with other sequence data. Choosing an appropriate cpDNA region for phylogenetic investigation is difficult because of the scarcity of information about the tempo of evolutionary rates among different noncoding cpDNA regions. The focus of this investigation was to determine whether there is any predictable rate heterogeneity among 21 noncoding cpDNA regions identified as phylogenetically useful at low levels. To test for rate heterogeneity among the different cpDNA regions, we used three species from each of 10 groups representing eight major phylogenetic lineages of phanerogams. The results of this study clearly show that a survey using as few as three representative taxa can be predictive of the amount of phylogenetic information offered by a cpDNA region and that rate heterogeneity exists among noncoding cpDNA regions.

The tortoise and the hare II: relative utility of 21 noncoding chloroplast DNA sequences for phylogenetic analysis

Methods for identifying species by using short orthologous DNA sequences, known as “DNA barcodes,” have been proposed and initiated to facilitate biodiversity studies, identify juveniles, associate sexes, and enhance forensic analyses. The cytochrome c oxidase 1 sequence, which has been found to be widely applicable in animal barcoding, is not appropriate for most species of plants because of a much slower rate of cytochrome c oxidase 1 gene evolution in higher plants than in animals. We therefore propose the nuclear internal transcribed spacer region and the plastid trnH-psbA intergenic spacer as potentially usable DNA regions for applying barcoding to flowering plants. The internal transcribed spacer is the most commonly sequenced locus used in plant phylogenetic investigations at the species level and shows high levels of interspecific divergence. The trnH-psbA spacer, although short (≈450-bp), is the most variable plastid region in angiosperms and is easily amplified across a broad range of land plants. Comparison of the total plastid genomes of tobacco and deadly nightshade enhanced with trials on widely divergent angiosperm taxa, including closely related species in seven plant families and a group of species sampled from a local flora encompassing 50 plant families (for a total of 99 species, 80 genera, and 53 families), suggest that the sequences in this pair of loci have the potential to discriminate among the largest number of plant species for barcoding purposes.

https://www.pnas.org/content/pnas/102/23/8369.full.pdf

Use of DNA barcodes to identify flowering plants

A list of 1719 chemical compounds identified from headspace samples of floral scent is presented. The list has been compiled from some 270 published papers, including analyses of 991 species of flowering plants and a few gymnosperms, a sample including seed plants from 90 families and 38 orders. The compounds belong to seven major compound classes, of which the aliphatics, the benzenoids and phenylpropanoids, and, among the terpenes, the mono- and sesquiterpenes, occur in most orders of seeds plants. C5-branched compounds, irregular terpenes, nitrogen-containing compounds, and a class of miscellaneous cyclic compounds have been recorded in about two-thirds of the orders. Sulfur-containing compounds occur in a third of the orders, whereas diterpenes have been reported from three orders only. The most common single compounds in floral scent are the monoterpenes limonene, (E)-β-ocimene, myrcene, linalool, α- and β-pinene, and the benzenoids benzaldehyde, methyl 2-hydroxybenzoate (methyl salicylate), benzyl alcohol, and 2-phenyl ethanol, which occur in 54–71% of the families investigated so far. The sesquiterpene caryophyllene and the irregular terpene 6-methyl-5-hepten-2-one are also common and occur in more than 50% of the families. Orchidaceae are by far the best investigated family, followed by several families known to have many species with strongly scented flowers, such as Araceae, Arecaceae, Magnoliaceae, and Rosaceae. However, the majority of angiosperm families are still poorly investigated. Relationships between floral scent and pollination, chemistry, evolution, and phylogeny are briefly discussed. It is concluded that floral scent chemistry is of little use for phylogenetic estimates above the genus level, whereas the distribution and combinations of floral scent compounds at species and subspecific levels is a promising field of investigation for the understanding of adaptations and evolutionary processes in angiosperms.

/pdf/diversity-and-distribution-of-floral-scent-3kpxfsqrud.pdf

Diversity and Distribution of Floral Scent

We present a quantitative synthesis of trophic cascades in terrestrial systems using data from 41 studies, reporting 60 independent tests. The studies covered a wide range of taxa in various terrestrial systems with varying degrees of species diversity. We quantified the average magnitude of direct effects of carnivores on herbivore prey and indirect effects of carnivores on plants. We examined how the effect magnitudes varied with type of carnivores in the study system, food web diversity, and experimental protocol. A metaanalysis of the data revealed that trophic cascades were common among the studies. Exceptions to this general trend did arise. In some cases, trophic cascades were expected not to occur, and they did not. In other cases, the direct effects of carnivores on herbivores were stronger than the indirect effects of carnivores on plants, indicating that top‐down effects attenuated. Top‐down effects usually attenuated whenever plants contained antiherbivore defenses or when herbivore ...

https://www.jstor.org/stable/10.1086/303311

Trophic cascades in terrestrial systems: a review of the effects of carnivore removals on plants.

Floral scents-a checklist of volatile compounds isolated by head-space techniques

The boreotropical flora concept suggests that relictual tropical disjunctions between Asia and the Americas are a result of the expansion of the circumboreal tropical flora from the middle to the close of the Eocene. Subsequently, temperate species diverged at high latitudes and migrated to other continents. To test this concept, we conducted a molecular phylogenetic analysis (using cpDNA) of the Magnoliaceae, a former boreotropical element that currently contains both tropical and temperate disjuncts. Divergence times of the clades were estimated using sequences of matK and two intergenic regions consisting of psbA-trnH and atpB-rbcL. Results indicate the tropical American section Talauma branched first, followed by the tropical Asian clade and the West Indies clade. Within the remaining taxa, two temperate disjunctions were formed. Assuming the temperate disjunction of Magnolia acuminata and Asian relatives occurred 25 mya (late Oligocene; based on seed fossil records), section Talauma diverged 42 mya (mid-Eocene), and tropical Asian and the West Indies clades 36 mya (late Eocene). These events correlate with cooling temperatures during the middle to late Eocene and probably caused the tropical disjunctions.

Molecular phylogeny of the Magnoliaceae: the biogeography of tropical and temperate disjunctions.

Coleoptera and Diptera are the primary pollinators of extant basal angiosperms (wind pollination is rare); lineages of these insects were established by the Late Jurassic. Contemporary examples of insect pollination of nonangiosperm plants are present in Gnetales (flies, moths) and Cycadales (beetles). The breeding systems of extant basal angiosperms are dominated by bisexual, protogynous, fragrant flowers that may form chambers in the female phase. Floral thermogenesis is widely distributed throughout the extant basal angiosperms (Nymphaeaceae, Illiciaceae, Aristolochiaceae, Magnoliaceae, and Annonaceae), into the basal monocots (Araceae) and extends into the advanced monocots (Arecaceae and Cyclanthaceae) and eudicots (only one family, Nelumbonaceae). The cycads are the only other plant group with heat‐producing reproductive structures (male and female cones). Flower temperatures of thermogenic plants are in the range required by endothermic insects for purposes of mating and flight, and it is hypothesi...

https://www.jstor.org/stable/10.1086/317575

New Perspectives on the Pollination Biology of Basal Angiosperms

The fi rst three branches of the angiosperm phylogenetic tree consist of eight families with ~201 species of plants (the ANITA grade). The oldest fl ower fossil for the group is dated to the Early Cretaceous (115 - 125 Mya) and identifi ed to the Nymphaeales. The fl owers of extant plants in the ANITA grade are small, and pollen is the edible reward (rarely nectar or starch bodies). Unlike many gymnosperms that secrete " pollination drops, " ANITA-grade members examined thus far have a dry-type stigma. Copious secretions of stigmatic fl uid are restricted to the Nymphaeales, but this is not nectar. Floral odors, fl oral thermogenesis (a re- source), and colored tepals attract insects in deceit-based pollination syndromes throughout the fi rst three branches of the phylo- genetic tree. Self-incompatibility and an extragynoecial compitum occur in some species in the Austrobaileyales. Flies are primary pollinators in six families (10 genera). Beetles are pollinators in fi families varying in importance as primary (exclusive) to secondary vectors of pollen. Bees are major pollinators only in the Nymphaeaceae. It is hypothesized that large fl owers in Nympha- eaceae are the result of the interaction of heat, fl oral odors, and colored tepals to trap insects to increase fi tness.

/pdf/pollination-biology-of-basal-angiosperms-anita-grade-3desogsol5.pdf

Pollination biology of basal angiosperms (ANITA Grade)

The floral biology of eight species of Magniolia native to the United States is described. The flowers are protogynous. They are pollinated by several species of beetles that enter buds as well as closed and open flowers to feed on nectar, stigmas, pollen, and secretions of the petals. Individual flowers persist from two to four days and undergo a series of petal, stigma, and stamen movements that assure pollination by beetles. It is suggested that the flowers of Magnolia are highly specialized for exclusive pollination by beetles. These specialization mechanisms produce large quantities of food for the beetles and deny other types of insects (bees, moths, etc.) access to the flowers at critical stages in the pollination process, i.e., when stigmas are mature and pollen is shed.

Floral biology of magnolia

Net primary production and decomposition of the 4 dominant salt marsh plants found in Louisiana were determined. Live and dead standing crops were calculated by the harvest method over an annual cycle. Litterbags were used to estimate loss rates of vegetation from the marsh. Peak standing crops were: 1164 g/m2 for Distichlis spicata, 2194 g/m2 for Spartina patens, 1959 g/m2 for Juncus roemerianus and 1473 g/m2 for Spartina alterniflora. Net production estimates using the Smalley (1958) method were from 1291 g.m(—2). yr(—1) for D. spicata, 1342 g.m(—2).yr(—1) for S. patens. 1740 g.m(—2).yr(—1) for J. roemerianus and 1527 g.m(—2).yr(—1) for S. alterniflora. Using the Wiegert and Evans' (1964) method net production for the 4 species was: 1162 g.m(—2).yr(—1), D. spicata; 1428 g.m(—2).yr(—1), S. patens; 1806 g.m(—2).yr(—1), J. roemerianus and 2895 g.m(—2)°yr(—1) for S. alterniflora. It is estimated that these 4 species of Louisiana marshland plants produce 146 x 105 metric tons/yr of plant material. This accou...

Leonard B. Thien

Papers

Molecular phylogeny of the Magnoliaceae: the biogeography of tropical and temperate disjunctions.

New Perspectives on the Pollination Biology of Basal Angiosperms

Pollination biology of basal angiosperms (ANITA Grade)

Floral biology of magnolia

Productivity and Decomposition of the Dominant Salt Marsh Plants in Louisiana