The anatomy of petal drop in sunflowers

Study finds cell division at abscission zone of short-lived cultivar occurs earlier than in long-lived variety

ITHACA, NY - Despite their consumer popularity as cut flowers, some sunflowers are difficult to market because of their tendency to lose petals soon after their flowers open. This characteristic, "petal drop", which in some varieties can occur within a day of the flowers' opening, ruins the appearance of sunflowers and damages their market value. Sunflower growers interested in finding cultivars that are less prone to this condition have had limited information about petal drop, but a new study in the Journal of the American Society for Horticultural Science contains findings can inform both sunflower breeding programs and consumers' choices.

Joyous Suiyigheh Tata and Hans Christian Wien from the Department of Horticulture at Cornell University studied the abscission zone, a differentiated region where petal drop initiates, at the base of petals of sunflower florets in two different cultivars. "We wanted to determine if differences in the abscission zone among sunflower cultivars were correlated with differences in timing of petal drop," the authors said. Two pollen-free hybrid sunflower cultivars were selected for evaluation: Procut Bicolor, which loses its petals easily, and Procut Yellow Lite, which holds its petals much longer.

For the first experiment, the researchers measured separation force for the two sunflower cultivars using a modified soil cone micropenetrometer, an apparatus that measures separation forces in the opposite direction. "The separation force experiments showed that detachment forces switched from an initial high to low in both cultivars because of the maturation of the separation layer. This maturation occurred earlier in the cultivar that is first to lose its petals (Procut Bicolor)," the authors said. They noted that there were no force readings for the short-lived cultivar on day 9 and day 12 because the flower had already wilted.

"In the second experiment, we studied the changes in the anatomy of the petal-achene juncture of the two cultivars," the scientists explained. Three stages from Procut Bicolor (PBC) and four stages from Procut Yellow Lite (PYL) were studied. These stages represent a time course with physiological relevance; when the flower just opens (anthesis), 8 days (the end of flower life for PBC), and 12 days (the end of flower life for PYL). The study also included analyses of petal anatomy at 4 days after harvest. The "end of flower life" was defined as the time when detachment force equals zero; when simply touching the petals caused them to fall off easily. Results of the analyses showed that cell division at the abscission zone of the short-lived cultivar occurred earlier than in the long-lived cultivar. "These results reveal that there was a difference in timing in the formation and maturation of the separation layer between the two cultivars," the authors said.

Interestingly, analyses showed that the mean "break strength" of cultivars in the yellow group was higher and significantly different from cultivars in the orange and bicolor groups, which were in turn higher than cultivars in the red group. Mean vase life (12 days) of the sunflowers in the yellow group was longer than cultivars in the orange group (10 days), while the vase life of the orange group was longer than cultivars in the bicolor group (9 days). The vase life of the red cultivars was shortest at 8 days. "We found that vase life has a strong relationship with flower color; the darker cultivars in the study had a shorter vase life compared with the lighter cultivars," the scientists remarked.

"The anatomy of petal drop in sunflower is similar to the majority of established descriptions in other species; the process involves the separation of four to five rows of smaller transversely oriented cells that lay horizontally across the diameter at the juncture between the petal and the achene, the separation layer," the authors said. "The concept that the timing of the maturation of the separation layer in the abscission zone helps determine the timing of petal drop is strongly supported by both the physical and anatomical investigations."

The authors concluded that the regression equation and results from the petal detachment force experiments can be used to screen sunflower cultivars in order to determine groupings of short-lived vs. long-lived cultivars. They said that the study contains beneficial information for sunflower breeding programs working to improve the breed's longevity, which can ultimately lead to increased sunflower sales.

Source: ASHS

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Native fungus suggested as another tool for restoring ghostly whitebark pine forests

Siberian slippery jack is a native fungus that may help in the effort to restore whitebark pine forests.
Credit: Cathy Cripps

Cathy Cripps doesn't seem to worry about the grizzly bears and black bears that watch her work, but she is concerned about the ghosts and skeletons she encounters.

The ghosts are whitebark pine forests that have been devastated by mountain pine beetles and white pine blister rust, said the Montana State University scientist who studies fungi that grow in extreme environments. The skeletons are dead trees that no longer shade snow or produce pine cones. The round purple pine cones hold the seeds that feed bears, red squirrels and Clark's nutcracker birds. Shade at the top of watersheds keeps snow from melting too fast in the spring, preventing trout streams from drying up too early in the summer.

Fortunately, she has found hope in a native fungus called Siberian slippery jack, or Suillus sibiricus, said Cripps, a mycologist in MSU's Department of Plant Sciences and Plant Pathology.

Cripps conducted a three-year study in collaboration with Waterton Lakes National Park in Canada that showed a 10 to 15 percent increase in the survival rate of whitebark pine seedlings when Siberian slippery jack spores are injected into the soil around them. The injection takes place in nurseries before the seedlings are transplanted in the mountains.

That increase is significant and good news for those trying to reinstate whitebark pine trees to the north-central Rocky Mountains and Pacific Northwest, Cripps said. The whitebark pine is a keystone species that grows at high elevations where other trees cannot, but it has been declared an endangered species in Canada and awaits the designation in the United States.

"That (jump in survival rates) might not sound like a big difference, but a small amount is a big deal considering the labor-intensive process," Cripps said.

Cyndi Smith, scientist emeritus at Waterton, said "The positive results have encouraged Waterton Lakes National Park to continue inoculating both whitebark and limber pine seedlings, to give them the best opportunity we can to establish and survive to maturity."

Participants in the research project, in addition to Cripps' and Smith's teams, were the U.S. Forest Service, National Park Service and volunteers from the United States and Canada.

Explaining how the collaboration began, Smith said, "Cathy gave a presentation on some of her Yellowstone work at the annual science meeting of the Whitebark Pine Ecosystem Foundation in Hailey, Idaho, in 2006. I was really taken with the idea that the ecosystem may have lost the beneficial fungi because our forests have been dead and dying for so long and that perhaps there was a way to reverse that trend so I approached Cathy with the idea.

"I'm a big believer in collaboration, whether locally or internationally, but certainly working with someone of Cathy's academic stature has been very helpful when I have applied for funding for whitebark and limber pine projects," Smith said, adding that, "Cathy's enthusiasm is very infectious, and it is a delight to work with her."

To carry out the research project, the participants placed cages around whitebark pine trees to collect pine cones without interference from wildlife. Then they tested the cones to see if they were resistant to white pine blister rust, removed seeds by hand from the resistant cones, grew the seeds into seedlings and shipped them to the nursery in Glacier National Park.

Cripps and former graduate student Erin Lonergan drove to Waterton Lakes 

National Park and throughout the Greater Yellowstone area, hiked to the tops of mountains and collected the Siberian slippery jack and other fungi from whitebark pine forests. Then they returned to MSU where they used a coffee grinder to process the spongy outer layer of the fungi. They added water to create a spore slurry, stored the mixture at MSU and later injected about 3 million spores into the soil around each seedling temporarily housed at the Glacier National Park nursery.

A few months later, volunteers planted more than 1,000 seedlings into MSU's test plots. Most of those test plots were located in Waterton, while others were in the neighboring Glacier National Park. The two parks together comprise Waterton-Glacier International Peace Park.

Two years into the study, Lonergan, Cripps and Smith reported success in the journal, American Forests. One year later, they announced their final results in the spring/summer 2014 issue of Nutcracker Notes, a small journal hosted by the Whitebark Pine Ecosystem Foundation.

"We wanted to get the word out that results after three years showed that inoculation with these native fungi significantly improved the survival of rust resistant seedlings, especially when inoculated seedlings were planted in burned areas near shelter objects such as stumps and logs," Cripps said.

High nitrogen fertilizations and fungicides prevent the inoculations from working, Cripps said. The age of the seedlings is important because they need to grow plenty of side roots before being inoculated.

When successful, the injected fungi slip like tiny socks over the ends of every root of the whitebark pine seedling and form a relationship that benefits both the tree and the fungi, Cripps said. The fungi help the seedling take in more nutrients and water from the soil. The tree produces the sugars that feed the fungi.

"Instead of being bad guys, these fungi are beneficial," Cripps said of the Siberian slippery jack. "They help plants take up nitrogen and phosphorus from the soil. That's a big deal."

Her study is one of many research projects involving whitebark pine forests, but it's unique because it focuses on beneficial native fungi, Cripps said. She added that land managers might want to incorporate MSU's findings into their overall strategy for restoring whitebark pine forests. She noted that large-scale inoculations are already planned for nurseries in Canada. She said inoculating beneficial fungi into nursery stock is common in Europe.

"As we work to save the vital whitebark pine from disappearing from the landscape, it is essential to use all available tools," Cripps said. "Ectomycorrhizal fungi are an integral part of forest integrity, ecology and health. Showing respect for these mighty microbes might just mean the difference between the restoration and death of a forest."

"Ectomycorrhizal fungi" refers to beneficial fungi that form a symbiotic relationship with the roots of trees. Siberian slippery jack is one of those fungi, and it only associates with five-needle pines. White pine blister rust is another type of fungus, one of the "bad guys."

Source: Montana State University

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Primates indispensable for regeneration of tropical forests

Moustached tamarins (Saguinus mystax) contribute crucially to the seed dispersal of the neotropical tree Parkia panurensis. Credit: Julia Diegmann

Primatologist and plant geneticists have studied the dispersal of tree seeds by New World primates.

Primates can influence seed dispersal and spatial genetic kinship structure of plants that serve as their food source. This is the result of a cooperation project of behavioral ecologist Eckhard W. Heymann from the German Primate Center (DPZ) with plant geneticists Birgit Ziegenhagen and Ronald Bialozyt from the Philipps-University Marburg. This study was funded by the German Research Foundation.

At the DPZ-field station Estación Biológica Quebrada Blanco in the Peruvian Amazonian lowlands, scientists studied how feeding, sleeping, and ranging habits of two species of New World monkeys affect the dispersal of the neotropical legume tree Parkia panurensis. For this, the researchers observed a group of Brown-mantled tamarins (Saguinus nigrifrons) and Moustached tamarins (Saguinus mystax), who jointly moved through home ranges in search of edible plants which included Parkia trees.

Fruits from these trees are pods that contain 16 to 23 seeds, each of which is surrounded by edible gum. The monkeys feed on the gum content of the pods and at the same time swallow the Parkia seeds which are later defecated intact in a different area.

During behavioral observations, researchers recorded the food intake of tamarins as well as the location of the Parkia trees that they visited. In addition, they collected faecal samples of the tamarins that contained seeds. "With the help of genetic analyses of the DNA found in the seed coat, which is of maternal origin, we could make an exact assignment of the corresponding "mother tree" for the seeds," says Eckhard W. Heymann from the DPZ. "This allowed us to determine how far Parkia seeds were dispersed by the monkeys."

In order to analyze the effect of seed dispersal by monkeys on a spatial genetic level, the scientists examined three different developmental stages of the trees. In addition to the seeds that contain the plant embryo, they collected leaves from young and mature Parkia trees in the home range of tamarins. "With the help of analysis from microsatellites, short repeated DNA sequences, we were able to identify genetic similarities of individual trees," says Heymann.

The analysis of the spatial genetic structure of the Parkia population revealed a significant genetic relationship of the plant embryos and young trees within a radius of 300 meters, which coincides with the distance within which most seeds are dispersed by the tamarins. For mature trees, the relationship was reduced to a radius of only up to 100 meters.

"In tropical rain forests, the seeds of 80 to 90 percent of trees and lianas are dispersed by animals. In addition to primates, birds and bats are the major animal groups that are responsible for seed dispersal," says behavioral ecologist Heymann. "For the plants, transport of their seeds is extremely important. As sedentary organisms, this is the only way that their offspring -- the embryos contained in the seeds -- can reach appropriate sites for germination and growth. Furthermore, this reduces the density-dependent mortality which occurs when the seeds fall under the mother plants," says Eckhard W. Heymann. Fruit-eating primates such as tamarins are therefore invaluable to the natural regeneration and diversity of ecosystems in which they live.

Source: German Primate Center

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Birth of four foals from genotyped, cryopreserved embryos: A first in Europe

Genotyping allows scientists to choose the embryos they want to use based on different criteria: sex, like in this experiment, the absence of known genetic disorders, or, perhaps in the future, other traits that are tied to behavior, such as emotivity or sociability. Credit: INRA/C. Maitre

IFCE and INRA announced that, for the first time ever in Europe, four foals were successfully born as the result of the transfer of genotyped and cryopreserved embryos. The goal of this work is to better understand embryonic development, control livestock reproduction, and maintain breed genetic diversity. Furthermore, it is advantageous for the horse industry to be able to determine the traits of a future foal.

The INRA Val de Loire center at Nouzilly is where the technology to maintain embryo viability following genotyping and cryopreservation was honed, and then, last summer, the transfer of several embryos took place at the IFCE Haras du Pin Stud Farm, located in the French department of Orne. The partnership between the two institutions has now been cemented by the birth of the healthy foals.

What were the steps leading up to the birth of these foals?

Seven days after fertilization, embryos were collected from Welsh B ponies that are part of INRA's livestock. The embryos were genotyped: scientists sampled some of the embryos' cells to analyze their genomes. In this experiment, embryos were selected based on sex, the idea being to use sex-based selection to test the technique's feasibility. The embryos were then cryopreserved in liquid nitrogen (at -196°). Last summer, they were transferred into saddlebred mares at the Haras du Pin center. After an 11-month gestation period, the foals were born in May. They were of the expected sex: two females and two males. This is the first time that such an event has taken place in Europe, and it is the product of more than 10 years of various types of embryonic research carried out by INRA and IFCE scientists.

What made it so difficult to apply this technique to horses?

Although embryo preservation techniques are already well developed for bovines, small ruminant species, and even humans, preserving horse embryos is a very complex process. For instance, horse embryos vary greatly in size: 7-day-old embryos range in diameter from 200 to 700 micrometers. It is very difficult to cryopreserve the largest embryos because the liquid inside them forms ice crystals when the embryos are frozen at very cold temperatures. What's more, horse embryos are surrounded by a capsule that interferes with successful cryopreservation.

What is the significance of this event, which is the first of its kind in Europe?

There are several reasons why being able to successfully cryopreserve embryos is important. For example, it allows us to maintain breed genetic diversity, particularly that of breeds with small population sizes, such as the Landais or the Poitevin Mulassier. Furthermore, the factor that currently limits the use of embryo transfer is its cost: the transfer center has to maintain a team of recipient mares that are reproductively synchronized with the donor mares. Cryopreservation means that the transfer doesn't have to take place immediately; it can wait until a recipient mare becomes available to receive the embryo. Finally, it may now be possible to directly repopulate horse herds that have experienced losses as a result of various issues, such as disease-related problems, instead of having to use the indirect technique of crossbreeding.

Why genotype the embryos?

Genotyping allows us to choose the embryos we want to use based on different criteria: sex, like in this experiment, the absence of known genetic disorders, or, perhaps in the future, other traits that are tied to behavior, such as emotivity or sociability. It is advantageous for the horse industry to be able to determine the traits of a future foal. We will next aim to simplify the process -- to make this technology more accessible and user friendly for those in the horse industry.

Source: INRA-France

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Father-son research team discovers cheatgrass seeds survive wash cycle

Professor Hugh Lefcort and son Caleb examine the cheatgrass in Spokane, Washington. Credit: Gonzaga University

Not many sixth-graders can say they have been published in an academic journal, but Caleb Lefcort can cross that distinction off his list. Caleb got into a discussion with his father, Hugh Lefcort, professor of biology at Gonzaga University, as to whether the seed burrs from cheatgrass would survive the laundry cycle. Hugh believed the seeds would not survive. Instead of simply taking his father's word for it, Caleb -- who was in fourth grade at the time -- suggested the scientific method: an experiment.

The father and son duo set out to determine whether the seeds would survive the wash.
The experiment

Finding cheatgrass seeds was easy. Bromus tectorum (the scientific name for cheatgrass) is nearly ubiquitous in the Inland Northwest and has become an increasing concern throughout North America -- spreading rapidly through the western United States both through natural means and unintended ways, like getting stuck in people's socks and shoes.

"We hypothesized that laundering would impact water potential, and we, therefore, predicted that seeds would exhibit poorer germination and emergence after being laundered," said Hugh. "We also predicted that the effect of laundering would be stronger if bleach was used."

To collect the cheatgrass seeds, Hugh and Caleb walked through a nearby field wearing only socks on their feet. They divided the socks into three different treatments: 1. Not washed or dried; 2. Washed with detergent but not bleach and subsequently dried; and 3. Washed with detergent and bleach and then dried.

The socks that were to be laundered were divided into three different washing machines/detergent/dryer combinations:
1. A Whirlpool washing machine using All brand detergent and Whirlpool dryer;
2. A Samsung washer using Tide brand detergent and a General Electric dryer; and
3. A Maytag machine using Era brand detergent and a Maytag dryer.

Findings

The results of the experiment surprised both Hugh and Caleb.

"There was no significant effect of the different washing machines and their associated laundry detergents and dryers on the number of seeds that sprouted, nor did we find a significant effect of laundry treatments in the number of seeds that germinated," said Hugh.

There was, however, an effect on the seeds that were treated with bleach; they germinated at a slightly slower rate than the other seeds that were tested without bleach. The height of the plants that sprouted from these bleached seeds differed from the height of the plants that experienced the no-bleach-wash treatment.

The research that Hugh and Caleb conducted revealed that cheatgrass seeds and their germination processes are sturdy enough to survive the soaking, soap and agitation of washing machines, the heat of dryers, and often even bleach. Though they designed the study to make it difficult for cheatgrass seeds to germinate, they were surprised at how easily the treated seeds sprouted into plants. Government agencies may consider adding these findings to their public service announcements.

Caleb Lefcort is now a sixth-grader Moran Prairie Elementary School.

Source: Gonzaga University

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'Probiotics' for plants boost detox abilities; untreated plants overdose and die

The Doty lab conducts work to see how plants treated with naturally occurring endophytes might handle soils contaminated with a variety of pollutants. Graduate student Robert Tournay, for example, is interested in how the plants handle arsenic. Credit: M Levin/U of Washington

Scientists using a microbe that occurs naturally in eastern cottonwood trees have boosted the ability of two other plants -- willow and lawn grass -- to withstand the withering effects of the nasty industrial pollutant phenanthrene and take up 25 to 40 percent more of the pollutant than untreated plants.

The approach could avoid the regulatory hurdles imposed on transgenic plants -- plants with genes inserted from or exchanged with other plant or animal species -- that have shown promise in phytoremediation, the process of using plants to remove toxins from contaminated sites, according to Sharon Doty, associate professor of environmental and forestry sciences and corresponding author on a paper about the new work in Environmental Science & Technology.

"Our approach is much like when humans take probiotic pills or eat yogurt with probiotics to supplement the 'good' microbes in their guts," she said.

The microbe from the cottonwood was encouraged to colonize the roots of willows simply by dipping rooted and trimmed cuttings in solutions with the microbe. Grasses were treated with microbes in solution as seeds sprouted in soil. Once integrated into the plants, the microbe supplemented their own microbial defenses.

Microbes that take up residence in the inner tissue of plants and don't cause negative symptoms are called endophytes. In nature, endophytes have a welcomed, symbiotic relationship with plants. In polluted soil, for instance, if the right endophytes are present they consume toxins coming up through plant roots. The endophytes get fed and the plant gets help neutralizing pollutants that could kill it.

That's been one challenge of phytoremediation: plants removing pollutants can, all too quickly, succumb to the toxins.

"When the endophyte in these experiments was given to willow and grasses, it reduced the phytotoxic effects of phenanthrene compared to the control plants that did not receive the endophyte and died," said lead author Zareen Khan, a UW research scientist in environmental and forest sciences.

Phenanthrene is carcinogenic, on the Environmental Protection Agency's priority pollutants list and belongs to a class of polycyclic aromatic hydrocarbons that get deposited into the environment via fossil fuel combustion, waste incineration or as byproducts of industrial processes. Soils that become contaminated can be capped with layers of uncontaminated soil or dug up and removed for cleaning at soil remediation facilities or storage at waste disposal facilities.

In their search, UW researchers tested six different endophytes from cottonwood and willow varieties and found one -- lab name PD1 -- from the eastern cottonwood to be superior at breaking down phenanthrene.

They introduced this endophyte into willow cuttings and lawn grass. Willows were chosen because some varieties have already proven adept at removing toxins and the shrubs have extensive root systems, take up a lot of water and grow rapidly. Lawn grass was included because it also grows fast and could be useful in parks and open-space areas.

In lab experiments, the willow cuttings with added endophyte protection continued to grow, kept their leaves and had denser root systems. Untreated plants wilted, lost leaves and their roots turned brown. When soils were analyzed, the treated willows took up 65 percent of the phenanthrene compared with untreated plants that removed 40 percent, an improvement of 25 percent.

Grass seed planted in contaminated soils and watered with solutions containing the PD1 endophyte germinated five days quicker, grew taller and had 100 more tillers, or new offshoots, after 13 days. Treated grass removed 50 percent of the phenanthrene from the soil, compared with untreated grass that removed 10 percent, an improvement of 40 percent.

In phytoremediation, plants that take up pollutants but don't degrade them have to be removed and treated as hazardous waste or otherwise disposed of safely. The willows treated in the UW experiment appear to have degraded some 90 percent of the phenanthrene to harmless components. The researchers said they'd like to determine if that promising finding holds up in mass-balance studies and want to examine the possible effects on bugs or animals that might bite the plants processing the toxins and other environmental considerations. Interestingly, other studies have shown that bugs can smell similar semi-volatile pollutants and avoid eating the plants containing them, Doty said.

The work was funded by a Small Business Innovation Research grant from the National Institute of Environmental Health Sciences and by funds provided through the Byron and Alice Lockwood Endowed Professorship that Doty holds. The other four co-authors on the paper were undergraduate volunteers: David Roman and Trent Kintz have since graduated while May delas Alas and Raymond Yap are still working on their bachelor's degrees.
Just down the road from UW is Seattle's Gas Works Park, a site Doty thinks is a prime candidate for the approach her lab reported. Contaminants in the soil, including phenanthrene, are from a now-dismantled gasification plant. Soils have been covered with uncontaminated soil.

"The idea of leaving a known carcinogen in a public place is not right," she said. "What about problems of erosion? We should do what we can to remove it. We spend so much money treating cancer, I'd like us to take steps to prevent it instead."

Source: University of Washington

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Lemurs: Gardeners of Madagascar rainforest at risk

Onja Razafindratsima, a graduate student at Rice University, observes a lemur in a Madagascar rainforest. Razafindratsima led a three-year study to explore the relationship between lemurs and trees. Lemurs eat the fruit and spread its seeds far from the parent tree to help ensure its survival. Credit: Photo courtesy of Onja Razafindratsima/Rice University

A majority of Madagascar's 101 species of lemurs are threatened with extinction, and that could have serious consequences for the rainforests they call home. A new study by Rice University researchers shows the positive impacts lemurs can have on rainforest tree populations, which raises concerns about the potential impact their disappearance could have on the region's rich biodiversity.

A large proportion of trees in Madagascar's rainforest have fruits eaten by lemurs. Lemurs in turn disperse the seeds of their fruit trees throughout the forest with their scat. Such dispersal can play a crucial role for a tree species' ability to regenerate, but effects are poorly understood, especially when there are multiple dispersers.

For the tree, the evolutionary advantage of having animal-dispersed seeds may be that the seeds land well away from their parent trees where survival is low or that seeds are directed into spots where they are the most likely to sprout and survive.

Amy Dunham, an assistant professor of biosciences, and graduate student Onja Razafindratsima set out to detail the symbiotic relationship between fruit-eating lemurs and the trees that feed them through a three-year study in a rainforest in southeastern Madagascar.

Their data from observations, experiments and mathematical models demonstrate that seeds of a common canopy tree have a 300 percent higher chance of sprouting and becoming a sapling when dispersed by lemurs versus simply falling to the ground. One of the three lemur species is particularly good at dropping seeds in spots that are most advantageous for sprouting and survival. Other lemurs are not so selective, but still benefit the tree by moving seeds away from the parent tree. By acting as forest gardeners, these animals give the tree's population a boost.

The study appeared online in the Ecological Society of America journal Ecology.

As part of the study, the researchers followed the seed-dispersal patterns of three of Madagascar's lemur species: the red-fronted brown lemur, the red-bellied lemur and the southern black-and-white ruffed lemur. That meant tracking and observing groups of lemurs as the animals leaped from tree to tree through the forest, dined in the 65-foot-high canopies and dropped their undigested seeds at ground level.

Razafindratsima led the study as part of a thesis project she expects to complete early next year. She built a team of local researchers near Ranomafana National Park, the home of Centre ValBio, a research station founded by Dunham's former Ph.D. adviser, primatologist Patricia Wright.

"We have a team of up to 10 local villagers who are trained to do research," said Razafindratsima, a native of Madagascar. "Their exceptional knowledge of the forest is very important to us when we're trying to track lemurs and identify seeds and seedlings in a forest with over 300 species of trees."

The research team tracked 24 groups of lemurs over a year without the benefit of radio collars, said Razafindratsima, who keeps in touch with her team via phone and Skype when she's at Rice. She said the study sites were as close as a short hike from Centre ValBio and as far as a two-day trek through steep terrain that entailed camping overnight.

In addition to tracking lemurs and their dispersed seeds, the research team spent three years carrying out experiments on seed sprouting and survival. They found that dispersal by lemurs dramatically increased the odds that seeds would take root and survive. In particular, the red-fronted brown lemurs tended to drop seeds away from their parent trees and in places where there were gaps in the canopy. This gave individual seeds the best shot at taking root.

Dunham said trees benefit from the wide dispersal of their seeds, and for some species in Madagascar, lemurs are the primary or only animal that can distribute those seeds. As the largest fruit-eaters in the system, these lemurs swallow seeds that may be too large for other fruit-eating animals, such as birds or bats.

"Seeds away from the parent tree survive better because there's less competition among seedlings," Razafindratsima said. "If they're close by the parent, they may also share the same natural enemies, like soil pathogens and seed predators, so there's higher mortality."

Trees that lose their dispersers will simply drop their seeds to the ground beneath their canopies, where chances of survival are slim, Dunham said. "Lemurs fill an important role as the gardeners for these trees. By ensuring that some seeds land in spots suitable for germination and survival, they increase the ability of these trees to replace themselves"

Dunham hopes the study will contribute to growing efforts to protect lemurs, and therefore the rainforest, which has been impacted in recent years by economic and political instability.

She noted grassroots efforts within Madagascar led to the first World Lemur Festival in late October to celebrate and protect the animals and their habitats in Madagascar.

"What got us interested is that frugivorous lemur populations are declining across the island, and we know very little about how these seed dispersers actually affect tree populations," she said. "Once we understand that better, maybe we'll have a better idea of how the community might change if the lemurs disappear.

"If some species suddenly lose their dispersers, but others dispersed by birds or the wind are doing fine, it may change population trajectories and alter which tree species are dominant in a community. To understand what happens when these species are lost, we need to understand their role in the ecosystem," she said.

Source: Rice University

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