BPotD Archives being removed

Results tagged “ubc research week”

Mar 12, 2012: Heterosigma akashiwo

Heterosigma akashiwo

We'll conclude the UBC Celebrate Research Week series a bit belatedly -- I was hoping to receive higher resolution images, but people get busy, so we'll make do. Katherine introduces today's researcher:

Richard White is a PhD student of Dr. Curtis Suttle, Professor and Associate Dean, Research (Faculty of Science) (Suttle lab). Today's entry is about an algae-infecting virus. The left image is of the HaNIV virus (from Lawrence, J et al. 2001. A novel virus (HaNIV) causes lysis of the toxic bloom-forming alga Heterosigma akashiwo (Raphidophyceae). J. Phycol. 37:216-222), and the second two images are of the alga Heterosigma akashiwo.

Richard writes about "Unraveling the viral diversity amongst marine phytoplankton":

Heterosigma akashiwo (pictured centre and right) is responsible for toxic blooms that cause mass economic impacts to marine fish population's worldwide. The name akashiwo itself comes from Japanese meaning "red tide", which is a phenomenon that this organism causes in marine ecosystems. The toxicity of blooms caused by Heterosigma akashiwo can affect all trophic levels of the marine environment from copepods, fish, echinoderms and mollusks, but the toxin is unknown.

Heterosigma akashiwo has a true adversary that regulates its population and helps safeguard Earth's ocean from its devastating bloom effects. A wide range of viruses infect Heterosigma akashiwo (pictured above left is an ssDNA virus - HaNIV), and these can be involved in the termination of blooms. Understanding these viruses provides insight into the natural control mechanisms that regulate red tides in nature.

Katherine adds: For those who are interested, you can see more about harmful algal blooms. A British Columbian resource also outlines their effect on people (Paralytic Shellfish Poisoning), as well as local beach closures.

Mar 8, 2012: Cyclobalanopsis glaucoides

Organized once again by Katherine, here's today's entry with an introduction from her:

Continuing the series for UBC's Celebrate Research Week">UBC Celebrate Research Week is another entry thanks to Dr. Roy Turkington, this time from his research undertaken in collaboration with Professor Zhou Zhe-khun. Dr. Turkington informed me that the first image is a general view of the canopy at the Ailaoshan Reserve. The second image shows one of three treatment plots of research being conducted by M.Sc student, Jessica Lu, where they are testing the effects of litter on soil nutrients, soil invertebrates, and germination & establishment of seedlings. The final image is from Jin Jin Hu (PhD student), showing his enclosures for testing the effects of rodents (and other seed predators) on germination and establishment of seedlings. Dr. Turkington writes:

Yunnan Province in southwestern China is a biodiversity hotspot containing more than 20000 species of higher plants (6% of the world's total). The biodiversity of this region is under threat from loss of habitat due to logging and the planting of economic plants. Fifteen to twenty percent of higher plant varieties are endangered, threatening the existence of 40,000 species of organisms related with them. One-third of all species of oak (approximately 150 species, Quercus plus Cyclobalanopsis) in these Asian evergreen broad-leaved forests belong to the genus Cyclobalanopsis and one of the dominant species in this genus is Cyclobalanopsis glaucoides. As a dominant species, it provides a major structural component of these diverse forests, yet seedlings of Cyclobalanopsis glaucoides are rarely observed, and even in years of higher acorn production, the number of oak seedlings is not significantly increased. Thus, an understanding of the factors that influence the long-term survival of Cyclobalanopsis glaucoides is critical to the maintenance of these forests.

These studies began in 2006 and are on-going. Specifically, we are testing if there is a relationship between large weather cells, such as the Pacific Decadal Oscillation and the Southern Oscillation Index, with acorn production, and if acorn germination & seedling establishment is affected by weevils, small mammals, birds, or the quality and quantity of litter in the understorey of these forests.

Mar 7, 2012: Effects of Nutrient Changes on Plant Communities

Katherine continues with another entry she's organized for UBC's Celebrate Research Week series. She introduces Dr. Roy Turkington:

Dr. Roy Turkington is a professor of plant ecology at UBC based under the Department of Botany and the Biodiversity Research Centre. The Turkington lab is currently undergoing research in collaboration with Dr. Lauchlan Fraser from Thompson Rivers University, BC and Professor Zhou Zhe-khun at the Xishuangbanna Tropical Botanical Garden and the Kunming Institute of Botany, Yunnan Province in China. Dr. Roy Turkington has been kind enough to share with us two entries regarding his research, first from the Kluane region in the Yukon, Canada, and in an upcoming entry, the Ailaoshan sites in Yunnan, China.

Today's entry, from Dr. Turkington, has photographs from the Yukon Kluane region, more of which are available on the Turkington lab website. The images are of Linnaea borealis (twinflower), Chamerion angustifolium (fireweed) and a study plot. Dr. Turkington writes:

It has been suggested that the application of nutrients to northern communities may simulate some of the same effects in the plant community that might be produced by global environmental change. Global changes such as increasing CO2 concentrations, increasing deposition of nitrogen and sulphur pollutants, and rising temperatures will have crucial impacts on nutrient cycles consequently leading to changes in primary production and species composition. Climate change will increase the supply of nutrients, by stimulating decomposition processes, and increase the rate of soil carbon accumulation. These changes will of course be modified by the interactions between plants and their environment. In the Kluane region we might initially expect that bryophytes, lichens, prostrate growth forms (e.g., Arctostaphylos uva-ursi/ and Linnaea borealis), and low nutrient-requiring species will be suppressed or eliminated by faster-growing, more upright clonal species such as the forbs, Chamerion angustifolium (syn. Epilobium angustifolium) and Mertensia paniculata.

As species composition changes in our plots we inevitably lose a number of species and raises the question if species-impoverished systems will perform less well or less efficiently than their counterpart systems with a full complement of species. To investigate these questions we used a removal experiment called "a functional group knock-out". This was achieved by removing plant functional groups (graminoids, leguminous forbs and non-leguminous forbs) individually and observing changes in community dynamics and ecosystem function. Response variables measured include both community dynamics (species frequency measures and leaf area index) and ecosystem function (above-ground biomass, above and below-ground decomposition rates [using litter bags], nutrient supply rates [using ion exchange membranes], light interception and soil water content). And yes, loss of species does lead to a loss of ecosystem function.

Mar 6, 2012: Mimulus spp.

Today's entry is again organized by Katherine for the UBC Celebrate Research Week series. She introduces Seema Sheth:

Seema Sheth is a Ph.D. student (Colorado State University) with the recently-appointed-to-UBC Dr. Amy Angert (Assistant Professor in the UBC Department of Botany (lab web page)). The lab studies the processes of adaptation in plants. Today's entry is from their work on species of Mimulus. The photographs, Seema informs me, are of Mimulus angustatus (purple/pink flowers) from Grass Valley, California, and Mimulus guttatus (yellow flowers) from the Red Hills Area of Critical Environmental Concern, California.

Seema (with input from Dr. Angert) writes about the evolutionary ecology of rarity in western North American Mimulus:

Most species are geographically rare, and all species occupy a limited number of areas, yet the causes of variation in the sizes and limits of species' geographic distributions are poorly understood. Identifying causes of rarity provides important insights into ecological and evolutionary processes such as dispersal, speciation, extinction, and adaptation. Understanding the factors that shape species' distributions also can improve our ability to prioritize species and areas of conservation concern, forecast changes in species' distributions in response to climate change, and predict the rate and spread of invasive species.

Properties of species' ecological niches, defined here as the set of environmental conditions under which births exceed deaths, may explain differences in geographic range size among species. For example, if a species can persist under a broader range of environmental conditions, then it should be able to occupy a greater geographic area than a species with a narrower environmental tolerance. This hypothesis predicts a positive relationship between niche breadth and range size. On the other hand, rare species may be more dispersal-limited, either because of intrinsically low dispersal ability or because they are younger and have had less time to expand across the landscape.

We are testing the niche breadth hypothesis within western North American monkeyflowers (genus: Mimulus, family: Phrymaceae), a diverse group of wildflowers that occupies a wide variety of habitats, including aquatic, alpine, grassland, and desert environments, and contains several species that specialize on microhabitats such as serpentine soils, copper mine tailings, geysers, and marble cliff walls. Due to their short generation times (6-12 weeks), ease of propagation, high seed production, and genomic resources, species in the genus Mimulus have become an emerging model in evolutionary ecology (Wu, CA et al. 2008. Mimulus is an emerging model system for the integration of ecological and genomic studies. Heredity 100:220-230). Further, the geographic distributions of Mimulus species vary markedly in size, are well-described, and largely encompassed within federally protected lands in western North America (Beardsley, PM et al. 2004. Patterns of evolution in Western North American Mimulus (Phrymaceae). American Journal Of Botany 91:474-489), thus representing an ideal group for testing hypotheses to explain variation in the size and limits of species' ranges.

To test the hypothesis that species with broader environmental niches occupy larger geographic areas than species with narrow environmental tolerances, we are using comparative and experimental studies. First, we compiled ~17,000 georeferenced occurrence records for Mimulus species that occur in western North America. We used these locality data along with climatic variables (such as annual mean temperature and precipitation seasonality) to model the climatic niche of each species and to quantify range size in multiple ways. Regardless of how range size is quantified, our results strongly support the prediction that range size increases with climatic niche breadth across species (see figure below ). To experimentally test these results, we are now quantifying niche breadth in terms of survival and growth of individuals across a range of temperature and soil moisture levels for six pairs of closely related Mimulus species that differ in range size. This will allow for a more comprehensive understanding of how broader niches may lead to larger ranges. Species with restricted distributions are thought to be more prone to chance extinctions than widely distributed species. Further, species with small ranges and/or narrow niche breadth may be more sensitive to climate change. Thus, understanding the relationship between physiology, niche characteristics, and range size will allow for better predictions of species' responses to changing climate.

Mimulus spp. - Niche Breadth Figure

Key to the figure (please note: not yet published formally and still requires peer review): Support for the hypothesis that niche breadth explains variation in geographic range size among species (N = 72). Raw species' data are shown here (transformed to meet assumption of normality), but results support predictions even after correcting for phylogenetic non-independence and sampling effort. Two closely related species that vary drastically in range size (see inset panel) and climatic niche breadth are highlighted here, and are part of an ongoing experimental study testing whether geographically restricted species have lower thermal niche breadth than their widely distributed close relatives.

Mar 5, 2012: Chlamydomonas reinhardtii

Chlamydomonas reinhardtii

Katherine has been busy assembling this year's UBC Celebrate Research Week series, starting with today's entry:

Dr. Jae-Hyeok Lee is an Assistant Professor with the UBC Department of Botany. He describes the research currently being undertaken by the Lee Lab as work in the hope of "understanding the ancestral conditions prior to the origin(s) of plant development".

Dr. Lee continues: In order to do this, the lab studies cellular mechanisms that orchestrate zygote development in Chlamydomonas, a green alga genus. Systematic approaches, including molecular genetics, comparative genomics and live cell imaging, have so far yielded a grand hypothesis that the green algal zygote is functionally and evolutionarily related to the plant sporophyte where most plant-specific structures such as leaf, seed, and flower have evolved. We believe that deeper understanding of green algal zygotes will guide us to follow individual evolutionary steps in the preceding billions of years from unicellular green algae to flowering plants.

The picture above was taken by a phase-contrast microscope and captures the most exciting and fierce moment of a green alga, Chlamydomonas reinhardtii during its sexual mating. Oval shaped, and averaging 5 micrometers in length, a Chlamydomonas cell (in the lower right corner) is a very good swimmer, utilizing two flagella on its apical side to move as it looks for either sunlight or a mating partner. Nutrient starvation induces cells to become gametes that participate in mating reaction. They are either of two sexual types, plus or minus, each reacting to its opposite sex as their flagella adhere only to the flagella of the other sex (red arrow). Upon flagellar adhesion, two gametes shed their cell walls (yellow arrow) and proceed through a cellular fusion process which takes only a couple of minutes (blue arrow). The union of cells initiates dramatic restructuring to differentiate as a dormant zygote that can endures a cold and dry winter.

Mar 14, 2011: Botanical Insecticides and Antifeedants

Key to Figures / Image Credits

Figure 1. The photograph of Mentha spicata was shared by Doug (shyzaboy@Flickr) of Troutville, VA via the Botany Photo of the Day Flickr Pool). Thank you for the contribution, Doug!

Figure 2. The illustration of Cinnamomum zeylanicum is from Köhler's Medizinal-Pflanzen (Band I), via Wikimedia Commons.

Figure 3. The photograph of the larva of Trichoplusia ni is courtesy of Alton N. Sparks, Jr., University of Georgia, Bugwood.org, Wikimedia Commons.


 

A belated ending to the Celebrate Research Week @ UBC series, due to a little bit of miscommunication. Here is the last entry for the series this year, organized by Claire. Claire introduces today's UBC researcher:

Yasmin Akhtar is a research associate in the insect toxicology lab with Dr. Murray B. Isman and lectures in the Faculty of Land and Food Systems. She works with botanical insecticides and antifeedants.

Yasmin writes: Culinary herbs including mint (Mentha spicata) (Figure 1) and spices such as cinnamon (Cinnamomum zeylanicum) (Figure 2) are used as insect control agents. Figure 3 shows a cabbage looper (Trichoplusia ni) larva, considered to be an agricultural pest.

Plants are sources of a bewildering array of natural products including terpenoids, phenolic and alkaloids, likely exceeding 100,000 chemical structures. Many of these chemicals provide defensive functions for the plants protecting them against herbivores and pathogens. Based on their defensive chemistry complex, vascular plants have been considered a valuable resource of natural insecticides, insect growth regulators, and behaviour modifying agents. Behaviour modifying agents may influence the feeding and oviposition (egg-laying) behavior of insects and may also serve as repellents.

The main focus of research in our lab is the development of botanical insecticides and antifeedants. We are exploring the potential use of natural pesticides based on plant essential oils. Some of these oils and their constituent chemicals are widely used as flavoring agents in foods and beverages and are even exempt from pesticide registration in the United States. Plant essential oils meet the criteria of reduced risk pesticides (Isman, 2008).

Plants producing essential oils that have been exploited for insect control include a number of herbs, most notably from the mint family (Lamiaceae), such as garden thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), and various species of mint (Mentha spp.). Other important sources are tropical trees, notably clove (Syzygium aromaticum) and cinnamon (Cinnamomum zeylanicum). Many of the essential oils have shown insecticidal, repellent, feeding deterrent (Jiang et al., 2010) and antimicrobial effects against a number of pests. Some of these oils or their constituents serve as active ingredients in commercially available insecticides, herbicides or repellents. Thymol, for example, a key essential oil constituent of garden thyme, is registered in Europe for the control of two important parasitic mites of the honey bee (Apis mellifera). Eugenol, a primary constituent of clove oil, is an active ingredient of a broad-spectrum insecticide (EcoPCO® D) sold by EcoSMART Technologies. Essential oil of rosemary is the active ingredient in two botanical insecticides currently used in the United States (HexacideTM and EcotrolTM).

We are also looking at the development of non-toxic crop protection chemicals that mimic naturally occurring bioactive odorants and tastants, and that are relatively easily prepared from commodity chemicals (Akhtar et al., 2010). We also look at the role of experience on the feeding behavior of larvae and oviposition choices of the subsequent moths with emphasis on habituation and dishabituation as well as learning and memory in insects (Akhtar et al., 2009). Cabbage looper (Trichoplusia ni), green peach aphids (Myzus persicae), confused flour beetles (Tribolium confusum), rust red flour beetle (Tribolium castaneum), and fruit flies (Drosophila melanogaster) are the major research insects. We also work with two-spotted spider mite (Tetranychus urticae). Bioassays are conducted to determine the feeding and oviposition deterrent effects of an essential oil. Feeding deterrent substances deter feeding in insects. Similarly, oviposition deterrent substances deter insects from laying eggs on the plants. Since insect damage to plants may result from feeding/oviposition or from transmission of pathogens during feeding, the chemicals that reduce pest injury by rendering plants unattractive or unpalatable may serve as potential substitutes for conventional insecticides.

References:

Akhtar, Y., Yu, Y., Isman, M.B., and Plettner, E. (2010). Dialkoxybenzene and dialkoxyallylbenzene feeding and oviposition deterrents against the cabbage looper, Trichoplusia ni: potential insect behavior control agents. Journal of Agricultural and Food Chemistry. 58: 4983-4991. DOI: 10.1021/jf9045123

Jiang, Z.L., Akhtar, Y., Zhang, X., Bradbury, R. and Isman, M.B. (2010). Insecticidal and feeding deterrent activities of essential oils in the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae). Journal of Applied Entomology. DOI: 10.1111/j.1439-0418.2010.01587.x

Akhtar, Y., Shikano, I., and Isman, M.B. (2009). Topical application of a plant extract to different life stages of Trichoplusia ni fails to influence feeding or oviposition behaviour. Entomologia experimentalis et applicata. 132: 275-282.

Isman, M.B. (2008). Botanical insecticides: for richer for poorer. Pest Management Science 64:8-11.

Mar 11, 2011: Bromelia hieronymi

Bromelia hieronymi

Continuing with UBC Celebrate Research Week series, Claire introduces today's UBC researcher:

Dr. Felice Wyndham is in UBC's Department of Anthropology and specializes as an ecological anthropologist. She researches ethnobotany, with a focus on Latin America. This particular article concerns a species of Bromelia and its uses by the Ayoreo people.

Dr. Wyndham writes:

Known as caraguatá by Guaraní-Spanish speakers, the Ayoreo of the Paraguayan Chaco call Bromelia hieronymi dajuá when it is alive and growing. After extracting and processing the fibres, it is called dajú. A closely related species, Bromelia balansae, or doría, is less valued for its fibres than for its starchy leaf base which can be roasted and eaten (as can dajuá, but it is more bitter and strong-smelling, thus not a preferred food). The soft (untwined) dajú fibres are also used as bandages, tied around a wound. The fibres can also be smoked in a cactus-wood pipe. This ground-cover bromeliad, though very common in most of the Central Chaco, has been depleted in the immediate vicinity of many communities due to increased harvesting for craft products. Women, the primary harvesters of the plant, must now travel up to 15km to find plants of suitable size and quality for fibre processing. Dajuá is best harvested in the rainy seasons, as the fibre becomes dry and brittle during the winter dry season (around July-September). The plant and its products are central players in many Ayoreo myths, stories and beliefs.

The Chaco is one of few neotropical dry ecosystems world-wide, an area of significant biological and cultural diversity. The region is characterized by alluvial plains, low annual rainfall (790mm mean) and xerophytic forests. The Ayoreo, whose language, Ayoreode dūwode, is of the Zamuco linguistic family, are among the groups in Paraguay that have recently made (and continue to make) transitions from primarily mobile/seasonal hunting and gathering to living at least part of the year in settled communities. The Ayoreo have extensive traditional territories in the Paraguayan and Bolivian Chaco. Recently, our 2010 UBC class in ecological anthropology explored the issues around Ayoreo land sovereignty and resource rights in a class blog, EcoAnth in Action.

Mar 9, 2011: Populus balsamifera

Key to Figures

Figure 1. Rooted cuttings of balsam poplar grown for 10 weeks under different photoperiods. Cuttings under a 16 hour day set bud after ~5 weeks growth, whereas those in the other two treatments did not. This genotype is from Minnedosa, MB (50.3°N).

Figure 2. Balsam poplar shoot tips showing (a) a dormant terminal bud, (b) the opening of a terminal bud in the year of its formation (a second flush), and (c) active growth.

Figure 3. Two subarctic genotypes of balsam poplar at Totem Field. The photo on the left (a) was taken May 11th 2010, while the photo on the right (b), of the same two plants, was taken July 8th 2010. The plant in the foreground is from Fairbanks, AK (65°N), whereas the plant in the background is from Labrador City, NL (53°N). Both trees set bud prematurely in late spring, but the Fairbanks genotype also drops its leaves, whereas the Labrador City genotype retains them until autumn. [courtesy Raju Soolanayakanahally, AESB-AAFC]


 

The University of British Columbia's Celebrate Research Week series continues today with another entry organized by Claire. Claire introduces today's UBC researcher:

Dr. Rob Guy is a Professor and Department Head in the Department of Forest Sciences. He specializes in the ecophysiology of trees and other plants, with emphasis on the use of stable isotopes (C, H, O & N) at natural abundance levels to field and laboratory problems in plant physiology and ecology. Members of the Tree Physiology Lab focus on material and energy exchange across the plant-environment interface, resource-use efficiencies and environmental stress. Special interests include plant carbon balance, water relations, nitrogen assimilation, temperature acclimation and climate adaptation.This particular write-up discusses how climate and photoperiod interact to control the growth phenology of balsam poplar (Populus balsamifera L.).

Dr. Guy writes:

Balsam poplar (Populus balsamifera L.) is a forest tree with a wide range across the boreal zone of North America, from Colorado to Nunavut, and from Alaska to Newfoundland. To study adaptive variation in this species, and to support tree selection and breeding programs, the AESB-AAFC (Agri-Environment Services Branch - Agriculture Agri-Food Canada) has in recent years established the AgCanBaP collection of 930 native balsam poplar genotypes from 62 locations (provenances) in North America. Just over half of this collection is planted into a common garden at Totem Field, on the UBC campus.

Species with large ranges can exhibit large intra-specific variation in morphology and physiology. For example, in balsam poplar, rates of photosynthesis and peak season shoot growth extension increase with latitude of origin. This is true in outdoor common garden conditions or in the greenhouse. However, when grown outdoors in southern latitudes and particularly at Totem Field, northern trees accomplish much less growth than southern ones, and many end up severely stunted.

It seems paradoxical that northern trees would have higher rates of photosynthesis and shoot extension than southern trees, yet not get nearly as large as southern trees, but this is true only in the field. If the days are kept long in the greenhouse (22 hours long!), the growth of the northern provenances continues to outstrip the south. Through these and other studies, we have established that growth of trees at high latitudes is not limited by intrinsic growth rate or photosynthesis but by day-length, which assures timely growth cessation and eventually leaf senescence and frost hardiness development. In most boreal trees, spring phenology (leaf flush) is controlled by temperature, but autumn phenology is controlled by photoperiod. Bud set for northern provenances is in response to different photoperiods than in southern provenances. This is called "photoperiodic adaptation" and it results in some odd behaviour at Totem Field.

It's not actually the length of day that plants respond to, but the length of night. Figure 1 replicates a classic growth chamber experiment showing how a light break in the middle of the night can maintain height growth in a mid-latitude balsam poplar. In this photo, an 8 hour night (left) has induced growth cessation whereas a 4 hour night (right) permits maximum growth. The tree in the middle received a 15 hour "day" plus a 1 hour light break in the middle of a 9 hour "night". It, too, continues to grow (but not as much the rightmost tree because it receives less light overall). Even just a very short night (<4 hours) will cause northern trees to cease growth and begin getting ready for winter. Within a few days their shoots will set a terminal bud (Figure 2a).

At Totem Field, the mid-latitude and near-arctic trees from northern Canada set bud in response to the longer nights that occur before the summer solstice. In other words, they begin preparations for winter before summer even starts! This explains why they fail to thrive in Vancouver. Spring does not arrive until late May or even June in their native environments, when photoperiods are long. In Vancouver, however, shoots flush and become sensitive to photoperiod long before the solstice. In fact the day-length is never long enough at Totem Field (16¼ hours in Vancouver on June 21) to maintain the growth of the northernmost trees. Mid-latitude trees, if they don't set bud much before June 21, tend not to become fully dormant and can recover with a second flush that occurs near or around this time (Figure 2b). Southern trees do what they're supposed to do and continue to grow steadily until August (Figure 2c).

Like bud set, leaf senescence also occurs earlier in northern provenances, but is separately controlled. This separation is of great adaptive importance to wide-ranging, north-temperate or boreal tree species. Because the climate of North America permits forest growth at a much higher latitude in the west than in the east, quite different photoperiods are needed to trigger events that occur closer to the summer solstice (bud set) than to the autumn equinox (leaf drop). The differences in the latter are nonetheless evident at Totem Field, where in years with an early spring, as in 2010, autumn leaf senescence occurs in May in provenances from the extreme northwest of the continent (Figure 3). In years with later springs, leaf senescence in these genotypes occurs closer to its normal time in late summer.

It is interesting to speculate how climate warming might affect tree phenology in native poplar stands and whether premature bud set may become a problem for our northern trees. Fortunately, there is always the possibility of a second flush. These observations remind us that the natural and/or artificial adaptation of forests to future climate is not just about changes in temperature. It is also about the changing relationships between temperature and the year-to-year constancy of local photoperiodic regime.

Mar 8, 2011: Crepis barbigera

Key to Figures

Photo 1 shows the long, yellow/green bristles on the involucral bracts of Crepis barbigera s.s. and a bee visiting a flower head in full bloom. Of course, the visiting bee is of little concern to the plant given that its seeds are clonal and don't require fertilization. The picture was taken on June 6th, 2007. This population is located south of Chelan (47.806000, -120.136000), Chelan County, Washington. Octoploid (8n) Crepis barbigera s.s. were found only on south facing slopes while diploid Crepis atribarba occurred only on north facing slopes at this site.

Photo 2 is of another Crepis barbigera s.s. and was taken on June 21st, 2007. This individual has the largest genome reported in the sunflower family. The population is located at the Tom McCall Preserve, west of Rowena, Wasco County, Oregon (45.668600, -121.304000). The mountain in the background is Mount Hood.

Figure 3 is a distribution map of Crepis barbigera s.s. and closely related Crepis atribarba.


 

We continue today with the University of British Columbia's Celebrate Research Week series, as organized by Claire. Claire introduces today's UBC researcher:

Chris Sears is currently working on his Ph.D. in Dr. Jeannette Whitton's lab for systematics, taxonomy and population genetics of the North America Crepis agamic complex and is working on reclassification of certain Crepis species. Chris Sears has been a T.A. of mine for two of my botany classes here at UBC (one of them being seed plant taxonomy) and I'm excited to have him share his taxonomic work with us for research week. Thank you Chris!

Chris writes:

Crepis is a genus of ca. 200 species in the Cichoriodideae subfamily of Asteraceae. As such, like dandelions, they have yellow ligulate flowers and exude white milky latex when injured. There are ten species of Crepis native to North America. Two other North American species traditionally placed in Crepis, Crepis nana and Crepis elegans, have been transferred to the genus Askellia based on morphological and DNA sequence data.

Crepis barbigera is a member of the North American Crepis agamic complex. An agamic complex comprises sexual diploids (2n) and closely related apomictic polyploidy (3n,4n, etc) derivatives. Apomixis is the production of seeds which are clones of the mother plant. This western North American group is well known amongst plant evolutionary biologist because one of the fathers of the modern evolutionary synthesis, Ledyard Stebbins, co-authored a monograph of the group with E.B Babcock entitled American species of Crepis. Published in 1938 this was one of the first monographical works of the biosystematics era. It established the North American Crepis agamic complex as an early plant model system for the taxonomic treatment of agamic complexes, and gave critical insight into evolutionary processes of such groups.

Babcock and Stebbins recognized nine species in the North American Crepis agamic complex. Seven of the nine species consist of diploid and polyploid individuals while the remaining two consist of only polyploid individuals. For example, Crepis atribarba and Crepis acuminata are made up of diploid and polyploid individuals but Crepis barbigera consists only of polyploids. In Dr. Jeannette Whitton's lab at the University of British Columbia, I am in the process of updating the taxonomy of the North American Crepis agamic complex to reflect new data gleaned from ploidy analysis, morphology, distribution, ecology, and DNA sequence data. As circumscribed by Babcock and Stebbins, DNA sequence data indicates that most individuals of Crepis barbigera are closely related to Crepis atribarba but a few are more closely related to Crepis acuminata. Those individuals that are closely related to Crepis atribarba have the largest known genome in Asteraceae. They are also morphologically similar to the nomenclatural type of Crepis barbigera, but also share qualitative morphological characters with Crepis atribarba. These individuals will be called Crepis barbigera sensu stricto (s.s., or in the strictest sense) below. Those plants that are closely related to Crepis acuminata share qualitative morphological characters with that species, and have much smaller genomes compared to Crepis barbigera s.s.

Whitton and I are currently preparing a paper to be submitted to a scientific journal that will recommend reducing Crepis barbigera s.s. to a subspecies of Crepis atribarba, and expanding the circumscription of Crepis acuminata to include those individuals formally placed in Crepis barbigera that are closely related to Crepis acuminata. This recircumscribed Crepis barbigera s.s. can be recognized by conspicuous, yellow/green, long, curved bristles on the involucral bracts of the flower heads. Crepis atribarba sometimes has bristles on their involucral bracts but they are not as long and are usually black and straight. Crepis barbigera s.s. is narrowly distributed from central Washington to the Columbia River Gorge, and extends eastward into northern Idaho (see map). Like other members of the North American Crepis agamic complex it can be found on the sagebrush steppes and in the lower margins of ponderosa pine forests. Based on historic records it is apparent that the distribution of this taxon has been reduced because much of the Columbia Plateau has been converted to agriculture.

Claire has organized this week's Botany Photo of the Day series as part of the University of British Columbia's Celebrate Research Week. Claire introduces today's UBC researcher:

Dr. Michael Blake is in the Department of Anthropology and Laboratory of Archaeology at UBC and studies the ancient distribution and movement of Zea mays in the Americas.

Dr. Michael Blake writes:

Maize (Zea mays subsp. mays L.), or corn as it is more commonly known in North America, has a remarkable history. This domesticated tropical grass, that today forms one of the world's most important staple crops, descended from the wild grass, teosinte (Zea mays subsp. parviglumis H.H. Iltis & Doebley), which grows naturally in west central Mexico. (Daniel adds: the photograph above is a comparison of Zea mays subsp. parviglumis and maize, photographed by Hugh Iltis, and courtesy of the Doebley lab at the University of Wisconsin). In the past ten years, plant geneticists have made several important discoveries about the history of Zea mays based on the genetic similarities and differences among all the modern varieties that people grow throughout the Americas. One of these discoveries is that Zea mays was most likely domesticated in only one region of Mexico--by indigenous peoples who lived in the Rio Balsas region--and from only one subspecies of teosinte and its close relatives. What is so interesting, and puzzling, about the earliest human use of teosinte, perhaps some 9,000 years ago, is that the seeds of the plant are very tiny, don't grow in cobs, and are surrounded by an exceedingly tough glume (bract). Why were early farmers interested in this plant? Archaeologists, beginning in the 1950s, have excavated many dry cave sites in Mexico but have yet to find the smoking gun indicating the earliest use of teosinte for food. In fact, despite more than a century of archaeological investigations in Mexico, we have yet to find any convincing evidence that people actually ate teosinte (or used it for any purpose for that matter).

In the late 1930s, George Beadle, a Nobel Prize-winning geneticist and former president of the University of Chicago, argued that teosinte must be the wild ancestor of Zea mays and, furthermore, that it likely underwent just a few genetic mutations (as few as five or six) that transformed it into early corn. The earliest Zea mays fragments we know of come from a cave in the state of Oaxaca in southern Mexico--not too far south of the present-day range of Zea mays subsp. parviglumis. These two fragments date to about 6200 years ago and show that one of the genetic changes was the development of the cob, along with the softening and retracting of the hard glumes. This made corn much more desirable to ancient Americans because not only were the nutritious kernels now easier to access, but they were all together on a four-rowed rachis, or cob, that didn't break apart when it ripened. This, and a handful of other genetic transformations set Zea mays and humans on a path of mutual dependence that has only increased over the succeeding millennia.

The map shows the earliest archaeological sites in each region of Mesoamerica (Mexico and Central America) and North America which have directly-dated maize remains (from Ancient Maize Map). It is the result of my research team's efforts to gather together all the known examples of maize that have been recovered and that have been dated using radiocarbon dating (14C).

When we compiled all of the dated fragments on our on-line database Ancient Maize Map, it was possible to see clear patterns of dispersal, much as we might expect if modern day corn descended from Zea mays subsp. parviglumis (teosinte) in west-central Mexico and was spread outwards from there. Perhaps most intriguing discovery is of many sites in Arizona and New Mexico, where corn was being grown by at least 4,000 years ago. The material collected is most often a cob or cob fragment, but some material includes kernels, leaves, stalks, even roots and preserved coprolites--much of it found in caves. Other small particles we collect of Zea mays preserve in the form of phytoliths, starch granules, and pollen. While these microscopic particles can't yet be dated themselves, some get trapped in datable residues left behind on pottery, milling stones, and even in dental callus. Where the residues have been directly dated, they show very early evidence of maize having reached Ecuador in South America by about 5,000 years ago. This suggests that Zea mays must have been of great interest to the earliest farmers from South America to North America and all points in between. It is the small particles of maize starch found on pottery fragments that have revealed an unexpectedly early movement of maize northwards across the Great Plains and into the south Prairies of Alberta and Manitoba. The map shows maize made its way into the economies of people in southern Alberta by between about 750 to 950 years ago. Charred maize kernels have been just north of Winnipeg dating to 550 years ago. Likewise, Zea mays has been found as far south as Chile and Argentina by about 2000 years ago.

Explore the UBC archaeological maize database and interactive mapping program at Ancient Maize Map. Make your own maps showing the distribution of maize in the Americas and zoom right into the regions and sites where the earliest remains of maize have been found. As more discoveries are made and as new radiocarbon dates come in, we will continue to update the database and track the history of maize--one of the world's most economically important crops.

Mar 10, 2009: Calliarthron sp.

Calliarthron sp.

Ruth continues with the UBC Research Week series:

Patrick Martone is a UBC Assistant Professor. His laboratory studies the biomechanics, evolution and functional morphology of marine algae.

Patrick writes: "One central research theme in my lab is to understand how intertidal seaweeds resist the relentless barrage of waves breaking on shore. Past studies have shown that, by being flexible, seaweeds reconfigure and reorient in flow to reduce drag. This paradigm holds even for many erect calcified algae, which locally decalcify to form flexible joints between calcified segments. Recent studies in my lab have investigated the biomechanical properties and chemical composition of the joints in the articulated coralline Calliarthron, which often dominates wave-exposed coastlines in California. We discovered that the joints in this red alga contain lignin, a primary component of wood in terrestrial plants, and are stronger, stiffer, and tougher than other algal tissues."

Daniel adds: Monterey Bay Aquarium has more details about this genus of algae and a few others.

Apr 16, 2008: Arabidopsis thaliana

Here's an entry assembled by Connor Fitzpatrick that was originally intended for UBC Research week:

Lacy Samuels, Geoffrey Wasteneys, and Heather McFarlane share their research on plant cell wall development.

Heather McFarlane, an undergraduate honours student, with Lacey Samuels and Geoffrey Wasteneys (UBC Botany), are researching the formation of cell walls in the plant, Arabidopsis thaliana. Specifically they are looking at the mechanisms by which pectin is secreted to a particular domain within the seed coat cells of Arabidopsis.

The first photo (bar=10 µm) shows the 5-6 sided mature seed coat cells and the second photo (bar=2µm) shows a cross section of a developing seed coat cell at 7 days post-anthesis (anthesis occurs when the anthers dehisce and is the only reliable point from which to measure time since fertilization). In the middle of each mature cell is a deposit of secondary cell wall surrounded by a ring of mucilage. In the developing cell, the central column is not yet secondary wall material but instead cytoplasm (c), containing amyloplasts (a), surrounded by the mucilage (mu), and just below the cytoplasm, the vacuole (v).

Pectin, a polysaccharide essential for the formation of primary cell walls in plants, is an important constituent of mucilage. In the area of the cell membrane that is most active in pectin deposition, there are abundant cortical microtubules. The third photo (bar=300 nm) shows these microtubules (mt) where the plasma membrane (pm) meets the mucilage pocket (mu). Cortical microtubules are required for deposition of cellulose microfibrils in the cell wall their function in this secretory system is unknown.

Samuels and Wasteneys hypothesized that these microtubules are important for the proper placement of pectin secretions. To test this hypothesis, they looked at the sites of pectin secretion in the seed coat cells of a temperature-sensitive mutant Arabidopsis that contained disorganized microtubules. However, secretion was not disrupted in the the mutant seed coat cells. This observation suggests that the cortical microtubules fulfill a role other than guiding pectin secretion during seed coat development.

The first image was taken using scanning electron microscopy; the second and third were taken using cryofixed cells and transmission electron microscopy.

Mar 11, 2008: Chytriomyces sp.

Chytriomyces sp.

The series for UBC Research Week continues. Today's write-up and photos are courtesy of Toko Mori. Toko writes:

My name is Toko Mori, a first-year graduate student in the Berbee Lab at the University of British Columbia. I study chytrid fungi, microscopic fungi that mainly live in freshwater. I especially focus on the local chytrids that parasitize freshwater microscopic algae. My long-term research goal is to create a tree of life of chytrids that parasitize algae and to see if there is any coevolutionary relationship between the species of parasitic chytrids and those of their host algae. I collected this chytrid on an alga, Vaucheria, from Burnaby Lake (Burnaby, BC) in August 2007. I have cultured it on agar and also co-cultured it with Vaucheria since then.

Since it seems that this is the first entry of chytrids in the Botany Photo of the Day, let me explain what they are. Chytrids are fungi, although they look quite different from mushrooms and molds, which we often think of as fungi. There are about one thousand species of chytrids which form the Phylum Chytridiomycota. Being the only group of fungi which reproduce by motile cells called zoospores (shown in picture 4), chytrids are considered to have diverged from the other fungi very early in their evolutionary history. Having motile spores gives them reproductive advantage in water. However, this is a double-edged sword; chytrids are unable to reproduce without moisture and thus bound to aquatic habitats.

Chytrids have recently attracted public attention as a cause for the population decline of amphibians. However, not all the chytrids are amphibian pathogens. To the contrary, many chytrid species are decomposers of organic matter in ponds and lakes, or parasites of microscopic invertebrates or algae, as in this case. Not much is known about their ecological roles.

Now let me explain these pictures. You are witnessing the moment of zoospore release, the highlight of their life history. The small round structure on the algal filament in picture 1 is a mature sporangium, where zoospores are produced. (The big bulge at the right end is a part of the alga, which I will explain later.) You can see the sporangium filled with small dots, each representing a zoospore. Five minutes later, the zoospores start to leave the sporangium, probably triggered by the sudden change in temperature caused by the intense light from the microscope. The change in pH of the surrounding water (when transferred from culture to a drop of distilled water on a slide) may also be the trigger. For a few minutes after the release, zoospores swarm just outside of the sporangium, until they start to swim away as in picture 3. As you may see in picture 4, the zoospores (ca. 4µm in diameter) have a flagellum like that of animal sperm. Eventually these zoospores stop swimming, retract their flagellum and encyst on a suitable substratum if they find one. Then they themselves will grow into a new sporangium, produce zoospores inside by mitosis, and start a new cycle of asexual reproduction.

A note for this alga. To co-culture this chytrid with its host, I received the culture of the host algal species, Vaucheria sessilis, from the Canadian Center for the Culture of Microorganisms at UBC. Vaucheria is unusual in that it lacks cell walls except when making reproductive structures; this entire filament seen here is one cell. The bulging end was formerly a spore, from which this algal filament grew.

Species identification is an important part of my research. Correct identification is the first step to making a tree of life. However, species identification of chytrids can be often difficult due to their simple body structure - there are not many morphological characters to study, at least on the light microscopy level. These days researchers combine molecular data and electron microscopy, together with traditional morphology. I have identified this chytrid down to the genus Chytriomyces, based on the light microscopic level morphology and molecular data.

1

a place of mind, The University of British Columbia

 
UBC Botanical Garden and Centre for Plant Research
6804 SW Marine Drive, Vancouver, B.C., V6T 1Z4
Tel: 604.822.3928
Fax: 604.822.2016 Email: garden.info@ubc.ca

Emergency Procedures | Accessibility | Contact UBC | © Copyright The University of British Columbia