American Journal of Botany current issue

Isolation and characterization of novel microsatellite markers for Arctium minus (Compositae) [AJB Primer Notes & Protocols in the Plant Sciences]

Wed, 03 Feb 2010 09:07:36 PST

• Premise of the study: Microsatellite primers were developed for the invasive plant Arctium minus to investigate the effects of facultative self-pollination and the biannual habit on population genetic structure, as well as the colonization of the Americas by this Eurasian species.

• Methods and Results: Sixteen di- and trinucleotide microsatellite loci were identified in six populations. The number of alleles per locus ranged from one to 10, observed heterozygosities ranged from 0.000 to 0.897, and the mean value of F_IS was 0.316.

• Conclusions: These results indicate the utility of these loci in future studies of population genetics in A. minus.

Flower and fruit characters in the early-divergent lamiid family Metteniusaceae, with particular reference to the evolution of pseudomonomery [Anatomy and Morphology]

Gonzalez, F. A., Rudall, P. J. — Wed, 03 Feb 2010 09:07:35 PST

Evaluating the morphological relationships of angiosperm families that still remain unplaced in the current systems of classification is challenging because it requires comparative data across a broad phylogenetic range. The small neotropical family Metteniusaceae was recently placed within the lamiids, as sister to either the enigmatic Oncothecaceae or the clade (Boraginaceae + Gentianales + Lamiales + Solanales + Vahliaceae). We examined the development of two of the primary diagnostic traits of Metteniusaceae, the moniliform anthers and the unilocular gynoecium. The gynoecium is 5-carpellate, and contains two ovules with a massive, vascularized integument. Late sympetaly and unitegmic ovules support placement of...

Angiosperm wood structure: Global patterns in vessel anatomy and their relation to wood density and potential conductivity [Anatomy and Morphology]

Wed, 03 Feb 2010 09:07:35 PST

Woody stems comprise a large biological carbon fraction and determine water transport between roots and leaves; their structure and function can influence both carbon and hydrological cycles. While angiosperm wood anatomy and density determine hydraulic conductivity and mechanical strength, little is known about interrelations across many species. We compiled a global data set comprising two anatomical traits for 3005 woody angiosperms: mean vessel lumen area (A) and number per unit area (N). From these, we calculated vessel lumen fraction (F = AN) and size to number ratio (S = A/N), a new vessel composition index. We examined the extent to...

Phylogeography and divergence date estimates of a lichen species complex with a disjunct distribution pattern [Bryology and Lichenology]

Otalora, M. A. G., Martinez, I., Aragon, G., Molina, M. C. — Wed, 03 Feb 2010 09:07:35 PST

Disjunct species distributions may result from a combination of geologic events and long-distance dispersal. The foliose lichen species complex Leptogium furfuraceum-L. pseudofurfuraceum has an intercontinental disjunction pattern. Populations of this species complex are found in western North America, southern South America, Africa, and southern Europe. We conducted a phylogenetic study to reconstruct the biogeographic history of this species complex using two ribosomal genes (ITS and LSU) and a protein-coding gene (partial RPB2). Results indicated that the complex comprises four geographically restricted genetic lineages. A sister relationship was found between populations from the same hemispheres, incongruent with previous data derived from...

A role for leaf epidermis in the control of leaf size and the rate and extent of mesophyll cell division [Developmental Biology and Developmental Genetics]

Marcotrigiano, M. — Wed, 03 Feb 2010 09:07:35 PST

Little is known about the control of leaf size in plants, yet there must be mechanisms by which organ size is measured. Because the control of leaf size extends beyond the action of individual genes or cells, an understanding of the role of leaf cell layers in the determination of leaf size is warranted. Following the construction of graft chimeras composed of small- and large-leaf genotypes of Nicotiana, bilateral leaf blade asymmetry was observed on leaves possessing either a genetically larger or smaller epidermis on one side of the midrib. Although cell size was unaffected by the genotype of the...

Clonal structure and genetic diversity of three desert phreatophytes [Ecology]

Vonlanthen, B., Zhang, X., Bruelheide, H. — Wed, 03 Feb 2010 09:07:35 PST

The objective of this paper was to assess clone sizes of three perennial desert plant species with AFLP markers and to relate them to clonal and genetic diversity and to hydroecology. The study was carried out at the southern rim of the Taklamakan Desert, where sexual regeneration is only possible shortly after rare flooding events, resulting in rarely established cohorts with subsequent extensive vertical growth and horizontal clonal spread. In this environment, repeated seedling establishment is excluded. We expected decreasing clonal and genetic diversity with increasing clone size and increasing distance to the groundwater table and a common response pattern...

Desert wildfire and severe drought diminish survivorship of the long-lived Joshua tree (Yucca brevifolia; Agavaceae) [Ecology]

DeFalco, L. A., Esque, T. C., Scoles-Sciulla, S. J., Rodgers, J. — Wed, 03 Feb 2010 09:07:35 PST

Extreme climate events are transforming plant communities in the desert Southwest of the United States. Abundant precipitation in 1998 associated with El Niño Southern Oscillation (ENSO) stimulated exceptional alien annual plant production in the Mojave Desert that fueled wildfires in 1999. Exacerbated by protracted drought, 80% of the burned Yucca brevifolia, a long-lived arborescent monocot, and 26% of unburned plants died at Joshua Tree National Park by 2004. Many burned plants <1 m tall died immediately, and survival of all but the tallest, oldest plants declined to the same low level by 2004. Postfire sprouting prolonged survival, but only at...

Does polyembryony confer a competitive advantage to the invasive perennial vine Vincetoxicum rossicum (Apocynaceae)? [Ecology]

Blanchard, M. L., Barney, J. N., Averill, K. M., Mohler, C. L., DiTommaso, A. — Wed, 03 Feb 2010 09:07:35 PST

Determining which traits may allow some introduced plant species to become invasive in their new environment continues to be a key question in invasion biology. Vincetoxicum rossicum is an invasive, perennial vine colonizing natural and seminatural habitats primarily in the northeastern United States and southeastern Canada. More than half its seeds exhibit polyembryony, a relatively uncommon condition in which a single seed produces multiple seedlings. For evaluating the potential consequences of polyembryony on invasiveness, V. rossicum plants derived from seeds of three embryonic classes—singlets, doublets, and triplets (one, two, and three seedlings per seed, respectively)—were paired in all combinations intraspecifically...

Variation of flower opening and closing times in F1 and F2 hybrids of daylily (Hemerocallis fulva; Hemerocallidaceae) and nightlily (H. citrina) [Genetics]

Nitta, K., Yasumoto, A. A., Yahara, T. — Wed, 03 Feb 2010 09:07:35 PST

In flowering plants, pollination success is strongly dependent on the timing of when flowers start to bloom and when they start to close. To elucidate the genetic mechanism influencing the timing of flower opening and closing, we obtained F1 and F2 hybrids of Hemerocallis fulva (a diurnally blooming species, pollinated by swallowtail butterflies) and H. citrina (a nocturnally blooming species, pollinated by nocturnal hawkmoths) and observed their flowering behavior from blooming to closing with the use of digital cameras. For flower opening times, F1 hybrids were highly variable, and F2 hybrids showed a bimodal distribution of flower opening times with...

Structural, physiological, and stable carbon isotopic evidence that the enigmatic Paleozoic fossil Prototaxites formed from rolled liverwort mats [Paleobotany]

Graham, L. E., Cook, M. E., Hanson, D. T., Pigg, K. B., Graham, J. M. — Wed, 03 Feb 2010 09:07:35 PST

New structural, nutritional, and stable carbon isotope data may resolve a long-standing mystery—the biological affinities of the fossil Prototaxites, the largest organism on land during the Late Silurian to Late Devonian (420–370 Ma). The tree trunk-shaped specimens, of varying dimensions but consistent tubular anatomy, first formed prior to vascular plant dominance. Hence, Prototaxites has been proposed to represent giant algae, fungi, or lichens, despite incompatible biochemical and anatomical observations. Our comparative analyses instead indicate that Prototaxites formed from partially degraded, wind-, gravity-, or water-rolled mats of mixotrophic liverworts having fungal and cyanobacterial associates, much like the modern liverwort genus Marchantia....

Episodic migration of oaks to Iceland: Evidence for a North Atlantic "land bridge" in the latest Miocene [Paleobotany]

Denk, T., Grimsson, F., Zetter, R. — Wed, 03 Feb 2010 09:07:35 PST

Dating the subsidence history of the North Atlantic Land Bridge (NALB) is crucial for understanding intercontinental disjunctions of northern temperate trees. Traditionally, the NALB has been assumed to have functioned as a corridor for plant migration only during the early Cenozoic, but recent findings of plant fossils and inferences from molecular studies are challenging this view. Here, we report dispersed pollen of Quercus from Late Miocene sediments in Iceland that shows affinities with extant northern hemispheric white oaks and North American red oaks. Older (15 to 10 Ma) sediments do not contain pollen of Quercus suggesting it arrived after that...

Leaf fossils of Banksia (Proteaceae) from New Zealand: An Australian abroad [Paleobotany]

Carpenter, R. J., Jordan, G. J., Lee, D. E., Hill, R. S. — Wed, 03 Feb 2010 09:07:36 PST

Fossils can shed new light on plant biogeography and phylogeny. Pinnately lobed leaves from the Oligo-Miocene Newvale lignite mine, South Island, New Zealand are the first extra-Australian leaf fossils of the charismatic genus Banksia (Proteaceae), and they are assigned to a new species, B. novae-zelandiae. Comparison with extant taxa shows that the fossils are best regarded as an extinct stem relative of Banksia because their available features are either plesiomorphic for the genus (notably, the stomata are superficially placed, not sunken in balloon-like pits as in many extant species) or lack evidence of synapomorphies that would enable them to be...

Does selfing or outcrossing promote local adaptation? [Population Biology]

Hereford, J. — Wed, 03 Feb 2010 09:07:36 PST

The degree to which plants self-fertilize may impact their potential for genetic adaptation. Given that the mating system influences genetic processes within and among populations, the mating system could limit or promote local adaptation. I conducted a literature survey of published reciprocal transplant experiments in plant populations to quantify the effect of mating system on the magnitude of local adaptation. Mating system had no effect on local adaptation. I detected no effect when species were categorized as either self-compatible or self-incompatible or when accounting for environmental differences between source populations. The results suggest that, despite limited genetic variation in selfing...

Genetic effects of chronic habitat fragmentation revisited: Strong genetic structure in a temperate tree, Taxus baccata (Taxaceae), with great dispersal capability [Population Biology]

Wed, 03 Feb 2010 09:07:36 PST

Tree species are thought to be relatively resistant to habitat fragmentation because of their longevity and their aptitude for extensive gene flow, although recent empirical studies have reported negative genetic consequences, in particular after long-term habitat fragmentation in European temperate regions. Yet the response of each species to habitat loss may differ greatly depending on their biological attributes, in particular seed dispersal ability. In this study, we used demographic and molecular data to investigate the genetic consequences of chronic habitat fragmentation in remnant populations of Taxus baccata in the Montseny Mountains, northeast Spain. The age structure of populations revealed demographic...

Twin oil sacs facilitate the evolution of a novel type of pollination unit (meranthium) in a South African orchid [Reproductive Biology]

Steiner, K. E. — Wed, 03 Feb 2010 09:07:36 PST

The unique floral morphology of the South African orchid H. pulchra, with its twin meranthia, is best explained as an adaptation to pollination by oil-collecting bees. Flowers consisting of meranthia (floral parts that function as single pollination units; commonly observed in garden Iris) are extremely rare among the angiosperms and their significance poorly understood. Unlike all other known examples of meranthia, the novel type described for H. pulchra is not bilabiate. All Huttonaea species are unique in having twin petal sacs with glandular verrucae that secrete oil and are pollinated by Rediviva (Melittidae) oil-collecting bees. But only Huttonaea pulchra has...

Evolution and polyploid origins in North American Arctic Puccinellia (Poaceae) based on nuclear ribosomal spacer and chloroplast DNA sequences [Systematics and Phytogeography]

Consaul, L. L., Gillespie, L. J., Waterway, M. J. — Wed, 03 Feb 2010 09:07:36 PST

The proportion of polyploid plant species increases at higher latitudes, and it has been suggested that original postglacial Arctic immigrants of some large groups, including grasses, were polyploid. We analyzed noncoding nuclear and chloroplast DNA of all North American diploid Puccinellia (Poaceae) and a subset of arctic polyploids to hypothesize evolutionary relationships among diploids and to evaluate the parentage of polyploids. Diploids formed three lineages: one uniting arctic species P. arctica and P. banksiensis; a second comprising arctic species P. tenella, P. alaskana, P. vahliana, and P. wrightii; and a third uniting the two temperate species P. lemmonii and P....

Phylogenetics of Puya (Bromeliaceae): Placement, major lineages, and evolution of Chilean species [Systematics and Phytogeography]

Jabaily, R. S., Sytsma, K. J. — Wed, 03 Feb 2010 09:07:36 PST

Puya (Bromeliaceae), a large genus of terrestrial bromeliads found throughout a range of elevations in the Andes and central Chile, is of great systematic, evolutionary, and biogeographical interest. This first molecular phylogenetic study of Puya and related bromeliads employs matK, trnS-trnG, rps16, and PHYC sequences. Chloroplast DNA, nuclear DNA, and combined DNA data all place Puya closest to subfamily Bromelioideae. Nuclear and combined data support Puya as monophyletic, and the two subgenera are nonmonophyletic. All data indicate that the Chilean species of Puya are early diverging within the genus, consistent with Chilean genera as the first-diverging members of subfamily Bromelioideae....

Genetic analyses of cell death in maize (Zea mays, Poaceae) leaves reveal a distinct pathway operating in the camouflage1 mutant [Brief Communication]

Huang, M., Braun, D. M. — Wed, 03 Feb 2010 09:07:36 PST

Controlled cell death is vital for many physiological processes in plants, such as xylem development, the hypersensitive response (HR), and senescence; however, the pathways governing cell death are incompletely understood. Studies of mutants that display a cell-death phenotype have greatly contributed to our knowledge of how this process is regulated. The maize camouflage1 (cf1) mutant displays the novel phenotype of cell-specific death of bundle sheath (BS) cells in discrete yellow leaf tissues. To investigate the BS cell death in cf1 mutants, we characterized potential underlying factors. Hydrogen peroxide (H₂O₂) is known to be involved in many cell-death events in plants,...

Formation and function of a new pollen aperture pattern in angiosperms: The proximal sulcus of Tillandsia leiboldiana (Bromeliaceae) [Brief Communication]

Albert, B., Matamoro-Vidal, A., Raquin, C., Nadot, S. — Wed, 03 Feb 2010 09:07:36 PST

Pollen grains are generally surrounded by an extremely resistant wall interrupted in places by apertures that play a key role in reproduction; pollen tube growth is initiated at these sites. The shift from a proximal to distal aperture location is a striking innovation in seed plant reproduction. Reversals to proximal aperture position have only very rarely been described in angiosperms. The genus Tillandsia belongs to the Bromeliaceae family, and its aperture pattern has been described as distal monosulcate, the most widespread aperture patterns recorded in monocots and basal angiosperms. Here we report developmental and functional elements to demonstrate that the...