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Study recommends improvements to how impacts of Non-Native Species are assessed

By | News

CABI has led an international team of Non-Native Species (NNS) specialists who have compiled a list of recommendations to improve the way in which the impact of a range of invasive pests – such as the tomato leaf miner Tuta absoluta – are assessed, potentially helping towards ensuring greater global food security.

Lead authors Dr Pablo González-Moreno and Dr Marc Kenis, Senior Researchers at CABI are two of 89 NNS experts from around the world who have collaborated on the paper, published in NeoBiota, that calls for ‘more robust and user-friendly’ impact assessment protocols to predict the impacts of new or likely invaders as well as to assess the actual impact of established species.

The manuscript is the outcome of an enormous collective effort using 11 different protocols to assess the potential impact of 57 NNS to Europe yielding a total of 2614 separate assessments. This unique dataset has allowed the authors to identify which are the main factors increasing the robustness of protocols and provide recommendations on how the robustness and applicability of protocols could be enhanced for assessing NNS impacts.

As reported in the study, entitled ‘Consistency of impact assessment protocols for Non-Native Species’, Dr González-Moreno and fellow scientists – from 80 institutions including the UK-based Centre for Ecology & Hydrology (CEH), University of Milan, University of Bern and Queens University Belfast – argue that ‘assessment of the realised or potential impacts of NNS is particularly important for the prioritization of management actions.’

Millions of the world’s most vulnerable people face problems with invasive weeds, insects and plant diseases, which are out of control and have a major impact on global prosperity, communities and the environment. Developing countries are disproportionately affected.

The global cost of the world’s 1.2 million invasive species is estimated at $1.4 trillion per year – close to 5 percent of global gross domestic product. In East Africa, five major invasive species alone cause $1 billion in economic losses to smallholder farmers each year.

The scientists believe that, currently, the large variety of metrics adopted to measure the impacts of invasive species undermines direct comparison of impacts across species, groups of taxa, localities or regions. They go on to argue that in general we have ‘little understanding of the patterns in consistency of impact scores across assessors and protocols, and more importantly, which factors contribute to high levels of consistency.’

Dr González-Moreno said, “There is an increasing demand for robust and user-friendly impact assessment protocols to be used by professionals with different levels of expertise and knowledge.

“Robust NNS impact protocols should ideally result in accurate and consistent impact scores for a species even if applied by different assessors, as long as they have the adequate expertise in the assessed species and context.

“Several key factors should be taken into account when selecting or designing an NNS risk assessment protocol, such as the aim, the scope, the consistency and the accuracy of the outcomes, and the resources available to perform the assessment – for example time or information available.”

In compiling a list of recommendations for improved NNS impact protocols, Dr González-Moreno and the team of researchers used 11 different protocols to assess the potential impact of 57 species not native to Europe and belonging to a very large array of taxonomic groups (plants, animals, pathogens) from terrestrial to freshwater and marine environments.

They agree that using a ‘5-level scoring, maximum aggregation method and the moderation of expertise requirements’ offers a good compromise to reducing inconsistencies in research findings without losing discriminatory power or usability.

Dr González-Moreno added, “In general, we also advise protocol developers to perform sensibility tests of consistency before final release or adoption. This is crucial as if a protocol yields inconsistent outcomes when used by different assessors, then it is likely that decisions taken based on the results could be variable and disproportionate to the actual impacts.”

Read the paper: NeoBiota

Article source: CABI

Image: CCO Public domain

Rice Cultivation: Balance of Phosphorus and Nitrogen Determines Growth and Yield

By | CEPLAS, News

Cluster of Excellence on Plant Sciences CEPLAS cooperates with partners from Beijing to develop new basic knowledge on nutrient signalling pathways

In the future, a newly discovered mechanism in control of plant nutrition could help to achieve higher harvests in a sustainable way. Scientists from Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing (China) discovered this mechanism in their research on Asian rice in collaboration with Professor Dr Stanislav Kopriva from the University of Cologne’s Botanical Institute and the Cluster of Excellence CEPLAS. The balance between nitrogen (N) and phosphorus (P) is decisive for crop yield. Both nutrients, which the plant absorbs from the soil through its roots, interact more strongly with each other than previously known. The study ‘Nitrate-NRT1.1B-SPX4 cascade integrates nitrogen and phosphorus signalling networks in plants’ has now appeared in the journal ‘Nature Plants’.

Kopriva said: ‘For healthy and optimal growth, all living beings need a good balance of minerals. However, we know very little about how plants achieve this balance.’ His colleagues in Beijing had observed that the addition of phosphate only had a positive effect on plant growth and yield if a sufficient amount of nitrogen was also available in the soil. ‘Together, we have now discovered the mechanism by which nitrogen controls the absorption of phosphate’, Kopriva remarked.

A detailed analysis at the molecular level revealed an entire signalling chain that the plant sets in motion – from the sensor that recognizes nitrate quantities to factors that enable the synthesis of the so-called transporters that carry the phosphate into the plant. Kopriva explained: ‘Although most of the components were already known individually, it was only through this work that they were brought together into a signalling pathway. This gives us a completely new understanding of how to control plant nutrition. In addition, it enables specific manipulations to either couple the uptake of both nutrients more closely or to separate them from each other – depending on how nutrient-rich the soil on which the rice grows is.’

Professor Dr Stanislav Kopriva from the Botanical Institute of the University of Cologne is co-speaker of the Cluster of Excellence on Plant Sciences CEPLAS at the Universities of Düsseldorf and Cologne. CEPLAS wants to develop basic knowledge about ‘SMART Plants for Tomorrow’s Needs’.

Read the paper: Nature Plants

Article source: University of Cologne

Image: Mufid Majnun / Pixabay

Okinawan Sea Grapes Reveal Secrets of Plant Evolution

By | News

If you’ve ever dined on the tropical island of Okinawa, Japan, your plate may have been graced by a remarkable pile of seaweed, each strand adorned with tiny green bubbles. Known as umi-budo or sea grapes, the salty snack pairs well with rice, sashimi and a tall glass of beer. But umi-budo is more than an iconic side dish; it’s a staple crop for Okinawan farmers. Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) recently decoded the sea grape genome to learn about the plant’s unique morphology and assist farmers in proper cultivation of the succulent seaweed.

“Many farmers face problems with sea grapes growing poorly. Today, they don’t know why such problems occur,” said Dr. Asuka Arimoto, first author of the study and a postdoctoral scholar in the OIST Marine Genomics Unit, led by Prof. Noriyuki Satoh. “Our genomic data can show them which genes are causing such trouble.” With a catalog of all the genes controlling sea grape growth, said Arimoto, the researchers may be able to help farmers diagnose deficient plants when they crop up. The research could also help curb the spread of closely-related green seaweeds, which harm the environment by pushing out local plant varieties in the Mediterranean Sea and Pan-Pacific.

The study, in DNA Research, utilized sample sea grapes from the Onna Village Fishery Cooperative, whose greenhouses are located just around the corner from OIST campus. The scientists deciphered the full sea grape genome and compared it to 15 published plant genomes, collected from unicellular algae, a type of moss, rice and thale cress. The research revealed key genes that allow sea grapes, a unicellular organism, to don its complex shape, and demonstrated the utility of using the algae to explore evolutionary processes in green plants.

“Recently, other countries have started cultivating this and related species of green seaweed,” said Arimoto. “I think this genomic information could help their future development, as well as Okinawa prefecture.”

Collection of Genes Creates “Puchi Puchi”

Tiny green balls branch off the central stem of the umi-budo plant, and when chewed, these teeny orbs burst in a pop of salty goodness. In Japanese, this sensational texture is known as “puchi puchi,” an onomatopoeia mimicking the sound of puny pops. The Marine Genomics Unit was curious as to how a plant made up of just one cell could grow into such a fantastical shape, thus granting sea grapes their singular texture.

“When we started the project, there were no [decoded] green seaweed genomes,” said Arimoto. “It was completely unknown how many genes are present in green seaweed, and which plant hormones are present to drive development.” The researchers succeeded in deciphering a high-quality genome from an umi-budo plant and compared it to known plant genomes to see whether certain genes appeared in different quantities between them.

The results suggest that the sea grapes contain an expanded set of genes thought to be descended from a core gene set found in a common ancestor of green plants. Among these genes are those that code for nuclear transport regulators—proteins that help control how information moves between the nuclei and the cytosol, the liquid in which a cell’s organelles float. In multicellular organisms, transport regulators tune whole cells to only receive certain signals, like a dial on a radio. In umi-budo, a unicellular organism, the proteins do the same for individual nuclei in the cell.

The mechanism allows single cells to take on complex shapes despite lacking cell membranes to separate one region from the next. Without nuclear transport regulators, sea grapes couldn’t grow in their signature clusters.

Compared to other green algae, sea grapes also have extra genes to code for homeobox proteins, which help to regulate the physical development of plants. Homeobox proteins flip switches on critical genes to turn them “on” or “off,” said Arimoto, which triggers cellular processes and shapes an organism’s anatomical structure down the line.

Helping Sea Grape Farmers in Okinawa and Beyond

In the future, the Marine Genomics Unit hopes to analyze gene expression as it occurs throughout the sea grape life cycle. For instance, evidence suggests that specific homeobox genes are highly expressed in the pollens and eggs of land plants. They may hold similar importance in the early life stages of umi-budo. As sea grape cultivation takes root beyond Okinawa and across the Pacific, this genomic data could help farmers establish more effective growing strategies.

While OIST researchers work with umi-budo in the lab, food-lovers can continue to order the delectable seaweed in restaurants across Japan, likely topped with a light dressing of vinegar, mirin and soy sauce. Oishi!

Read the paper: DNA Research

Article source: Okinawa Institute of Science and Technology Graduate University (OIST)

Image: Ken Maeda (OIST)

Harnessing plant hormones for food security in Africa

By | News

Striga hermonthica, also known as purple witchweed, is an invasive parasitic plant that threatens food production in sub-Saharan Africa. It is estimated to ruin up to 40 per cent of the region’s staple crops, the equivalent of $7-10 billion, putting the livelihoods and food supplies of 300 million people in danger.

Striga has an Achilles’ heel: it’s a parasite that attaches to the roots of other plants. If it can’t find a host plant to attach to, it dies. Scientists have found a way to exploit Striga’s Achilles’ heel to eradicate it from farmers’ fields.

Salim Al-Babili, associate professor of plant science at the King Abdullah University of Science and Technology, and colleagues found that they could trick Striga seeds that a host plant was growing nearby. When conditions are right, the Striga seeds germinate, but without a host plant to attach to, they cannot survive.

The scientists take advantage of plant hormones called strigolactones, which are exuded by plant roots. It is these hormones that trigger Striga seeds to germinate. By treating bare crop fields in Burkina Faso with artificial strigolactones, the scientists found that they were able to reduce the number of Striga plants by more than half.

The scientists’ solution can be applied to crop fields over the course of a crop rotation, and doesn’t require additional water – the treatment begins to work when the rains fall. This has obvious advantages in a region where water is scarce. Al-Babili has been awarded a $5 million grant by the Bill & Melinda Gates Foundation to continue developing real-world solutions to the Striga problem.

This new method will allow farmers and scientists to work together to combat the spread of the invasive Striga plant and help protect the food security of 300 million people in sub-Saharan Africa.

Read the paper: Plants People Planet

Image Credit: Wikimedia

Duckweed: The low-down on a tiny plant

By | News

Duckweeds – for many aquatic animals like ducks and snails, a treat, but for pond owners, sometimes a thorn in the side. The tiny and fast-growing plants are of great interest to researchers, and not at least because of their industrial applications – for example, to purify wastewater or generate energy. An international research team from Münster, Jena (both Germany), Zurich (Switzerland) and Kerala (India) have recently studied the genomics of the giant duckweed. They discovered that genetic diversity, i.e. the total number of genetic characteristics that are different among individuals, is very low. “This is remarkable given that their population size is very large – there can, for example, be millions of individuals in a single pond”, says Shuqing Xu, professor for plant evolutionary ecology at the University of Münster and lead author of the study.

To understand the reason behind this mystery, a team of plant researchers headed by Dr. Meret Huber from the Max Planck Institute for Chemical Ecology in Jena and the University of Münster measured the mutation rate of this duckweed under outdoor conditions, i.e. how many mutations accumulate per generation. The result: low genetic diversity in this plant was accompanied by an extremely low mutation rate. “Our study emphasizes that accurate estimates of mutation rates are important for explaining patterns of genetic diversity among species”, says Meret Huber. The results are not only relevant for future studies on the evolution of plants, including many crops that have similar reproductive strategies like duckweeds, they will also accelerate the use of duckweeds both for basic research and industrial applications. The study was published in the journal “Nature Communication”.

Background

Although mutations are the raw materials for evolutionary changes, they are often accompanied by fitness impairments. Evolutionary researchers have hypothesized that natural selection in species with large populations drives the mutation rate to as low as possible. According to this hypothesis, a species with a very large population size may under certain conditions evolve an extremely low mutation rate – which in turn can result in a very low genetic diversity. Until now, however, scientists had not been able to show this connection in eukaryotes, i.e. organisms whose cells have a nucleus. One reason for this is that mutation rates are difficult to measure experimentally.

The researchers took samples of the giant duckweed (Spirodela polyrhiza) from 68 waterbodies distributed all over the world and read the DNA sequences of their entire genomes. They found that in congruence with their geographic origin the samples fall into four genetic clusters: America, Europe, India and Southeast Asia. Based on the genome sequence information, they found that the genetic diversity of the species is among the lowest values reported in multicellular eukaryotes.

Because genetic diversity is determined by mutation rate and effective population size, the scientists then experimentally estimated the mutation rates and calculated effective population size. Since external conditions can influence the mutation rate, they performed the experiments under outdoor conditions. The result: by sequencing genomes, they found that the mutation rate in the giant duckweed was the lowest ever determined for multicellular eukaryotes. The estimated effective population size, as expected, is rather large.

The researchers suspect that the enormous population size of the giant duckweed, and therefore the large possibilities of selection in the course of evolution, has led to the reduction of mutations to a minimum. This in turn can explain the low genetic diversity. “Our study provides new insights into why and how genetic diversity differs among different species”, says Shuqing Xu.

Together with their collaborators, the scientists are currently working on analyzing genomes of even more duckweed samples and plan to carry out outdoor selection experiments. They wish to discover which other factors might have played roles in shaping the evolution of this plant.

Read the paper: Nature Communication

Article source: University of Münster

Image: Close-up of the giant duckweed. Credit: Klaus J. Appenroth

Are no-fun fungi keeping fertilizer from plants?

By | News

Crops just can’t do without phosphorus.

Globally, more than 45 million tons of phosphorus fertilizer are expected to be used in 2019. But only a fraction of the added phosphorus will end up being available to crops.

The impact is two-fold: financial and environmental. “Fertilizer costs are significant for farmers in south Florida,” says Tiedeman. “And phosphorus rock, the most widely used source of phosphorus fertilizer, is in low supply across the globe. It is thought that phosphorus rock resources will only be available for the next 50 to 200 years.”

Tiedeman is exploring whether a rarely-studied process involving soil fungi could contribute to low phosphorus availability to plants in south Florida. This research could also help unravel how land use influences fungal communities in soil. It may also help us better understand vital soil-phosphorus dynamics.

“In general, fungi play a tremendous role in cycling phosphorus within soils,” Tiedeman says. “They can release phosphorus from mineral (rock) and organic (decaying matter) sources. From there, plants take up the released phosphorus.”

But under specific environmental conditions, like those found in south Florida soils, fungi may be contributing to the problem of phosphorus unavailability. Some fungi are capable of making minerals out of elements dissolved in soil water. This process is called “bioprecipitation”. Tiedeman wonders if fungi can take dissolved (plant-available) phosphorus and convert it to less available mineral forms.

The soils of south Florida add another layer to the puzzle. “Agricultural soils in south Florida are quite unique,” says Tiedeman. “They were created by pulverizing limestone bedrock to create rocky calcareous soil.”

“Over time, this coating can become a ‘seed’ for more stable, less available forms of phosphorus.” says Tiedeman.

Without freed-up phosphorus, crops can’t grow successfully. So many farmers in south Florida have kept adding phosphorus to soils. In a continuing cycle, most of this phosphorus becomes unavailable to plants. Over time, large amounts of unavailable phosphorus have collected in these soils. “Some agricultural soils in the area have 100-200 times more phosphorus than what was naturally present. Along with high concentrations of P, the types of P compounds present in these soils are perplexing. Recent studies have documented the presence of apatite – a phosphorus crystal that generally requires intense heat and pressure in order to form. One hypothesis, which is driving Tiedeman’s research, is that microorganisms in the soil are creating stable phosphorus minerals.

To investigate whether fungi are able to create phosphorus minerals, Tiedeman is bringing the fungi into the lab. This allows her to explore several questions: How do local soil fungi respond to doses of available phosphorus while living in limestone soils? Do fungi contribute to the crystallization of phosphorus?

“We plan to analyze fungal samples and any biproducts of their growth using a scanning electron microscope,” says Tiedeman. “That would allow us to actually look for crystal forms of phosphorus. It may also help us better understand how fungi get crystals to form.”

“Investigating south Florida’s limestone soils may have implications beyond a regional scale,” says Tiedeman. “Identifying all processes involved in phosphorus unavailability in calcareous soils will be useful in developing strategies to improve fertilizer use efficiency. This could be of great benefit to producers and the environment.”

Tiedeman presented her research at the International Meeting of the Soil Science Society of America, Jan. 6-9, San Diego.

Article source: American Society of Agronomy

Image credit: Mary Tiedeman.

Not All Carrot Germplasm is the Same—In Terms of Salinity Tolerance

By | News

Salinity stress is considered one of the most important abiotic factors that limits the productivity of crop plants, and the estimated global cost due to salinity is more than $12 billion annually. This is due to the extensive use of irrigation and high rates of evapotranspiration, which result in increased salt accumulation in the soil.

A study out of The USDA Agricultural Research Service at the University of Wisconsin has evaluated the response of diverse carrot germplasm to salinity stress, identified salt-tolerant carrot germplasm that may be used by breeders, and defined appropriate screening criteria for assessing salt tolerance in germinating carrot seed.

Adam Bolton and Philipp Simon focused on carrots in their research of glycophytic plants. Most crops, including cultivated carrots, are categorized as glycophytic plants. The growth of glycophytes is greatly reduced in saline soils because they lack physiological mechanisms such as the salt glands and bladders that allow halophytes, or salt-loving plants, to thrive in high salinity.

Bolton and Simon postulate that this type of extensive evaluation is needed to develop varieties that are considered fully salt-tolerant at each developmental stage for carrots.

Their research is explained in the article “Variation for Salinity Tolerance During Seed Germination in Diverse Carrot Germplasm”, found in HortScience, published by The American Society for Horticultural Science.

Bolton and Simon note that one approach to combating the negative effects of salinity stress in glycophytic crops is identifying new genetic sources of tolerance and efficient phenotypic methods to develop salinity-tolerant cultivars.

Data collected from many crop species suggest that the level of salinity tolerance is highly dependent on the developmental stage of the plant. This life stage-specific tolerance means that a genotype that has tolerance at one life stage may not be tolerant at any other of its life stages. Therefore, to more efficiently identify tolerant genotypes, their evaluations needed to continue throughout the varying stages of ontogeny of the plant, from germination through the reproductive phase.

Screening for salt tolerance at the germination stage is the first step in identifying tolerant genotypes because it is a critical stage for plant development. Fortunately, the researchers discovered, screening at this stage is among the most rapid and economical stages of development to evaluate a large number of diverse germplasm accessions.

Bolton and Simon used multiple criteria for quantifying salt tolerance. This broad approach demonstrated wide phenotypic variations during the seed germination stage among diverse carrot accessions. Significant differences in the percent of seed germination under nonstress conditions and for all salt tolerance germination measurements were observed among the 14 different regions of carrot accession origin.

Ultimately, this study identified a wide range of phenotypic variations for salt tolerance during the germination stage in a collection of diverse carrot accessions. These accessions could serve as potential parents for creating mapping populations to identify the specific genotype associated with salt tolerance. This discovery is promising for breeders as it suggests a route for them to move toward generating healthy plant crop cultivars with additional tools for growing on salt-affected soil.

Simon adds, “In previous studies, carrots have been characterized as a crop that is sensitive to salinity. This study evaluated a large collection of wild and cultivated carrot germplasm and confirmed that, in fact, many carrot cultivars are saline-sensitive during seed germination, but that many germplasm accessions evaluated were quite saline-tolerant. Interestingly, many of the more saline-tolerant carrots evaluated were cultivated carrots, perhaps reflecting unintentional selection by farmers that have been growing the crop with saline irrigation water. This study provides an optimistic outlook for breeding carrots with improved salinity tolerance during germination. Tolerance during seeding and later plant development will also be needed as salinity becomes a more serious challenge for farmers.”

Read the paper: HortScience

Article source: American Society for Horticultural Science

Image credit: Markus Spiske / Pixabay

Deciphering the Walnut Genome

By | News

California produces 99 percent of the walnuts grown in the United States. New research could provide a major boost to the state’s growing $1.6 billion walnut industry by making it easier to breed walnut trees better equipped to combat the soil-borne pathogens that now plague many of California’s 4,800 growers.

In a new study, a team of scientists at the University of California, Davis, and USDA’s Agricultural Research Service, ARS used a unique approach to sequence the genomes of the English walnut and its wild North American relative by tapping into the capabilities of two state-of-the-art technologies: long-read DNA sequencing and optical genome mapping. The resulting genome sequences are believed to be of the highest quality ever assembled of any woody perennial.

“By sequencing the genome of a walnut hybrid, we produced complete genome sequences for both parents in the time normally required to produce the sequence of one genome,” said Ming-Cheng Luo, leading genomics investigator on the project and a research geneticist in the Department of Plant Sciences at UC Davis.

This approach could be applied to genome sequencing of trees and many other woody perennials, opening the door to a better understanding of the genetic blueprints of almonds, pecans, pistachios and grapes.

“Like walnut, these other crops naturally cross-pollinate and are therefore highly variable,” said Jan Dvorak, co-principle investigator and genetics professor at the Department of Plant Sciences at UC Davis. “Variability has always greatly complicated our ability to produce a high-quality genome sequence for such crops, but these new technologies now make it possible,” Dvorak added.

In California, walnuts are grown commercially using rootstocks chosen specifically for their ability to tolerate various soil-borne diseases.

“We chose to cross the widely used English walnut specifically with the wild Texas Black walnut because of its native resistance to several soil-borne diseases and root nematodes, which are serious pests of walnut in California,” said Dan Kluepfel,a USDA-ARS scientist and principal investigator of the walnut-rootstock development project.

The assembled genome sequences of the two walnut species also will now help researchers identify genetic markers that breeders can use to develop new varieties with improved pathogen and pest resistance.

Major contributors to the project included UC Davis scientists Tingting Zhu, Le Wang, and Agriculture and Agri-Food Canada scientist Frank You.

Read the paper: Horticulture Research

Article source: USDA’s Agricultural Research Service (ARS)

Image credit: Suju/ Pixabay

How Tree Diversity Regulates Invading Forest Pests

By | News

A national-scale study of U.S. forests found strong relationships between the diversity of native tree species and the number of nonnative pests that pose economic and ecological threats to the nation’s forests.

“Every few years we get a new exotic insect or disease that comes in and is able to do a number on our native forests,” says Kevin Potter, a North Carolina State University research associate professor in the Department of Forestry and Environmental Resources and co-author of an article about the research in Proceedings of the National Academy of Sciences.

“Emerald ash borer is clobbering a number of ash species in the Midwest and increasingly in the South. The chestnut, a magnificent tree that had immense ecosystem value as well as economic value in the South and North, is pretty much gone because of a pathogen. And hemlocks are under attack by the hemlock woolly adelgid from the Northeast along the Appalachian Mountains into the South.”

To better understand how nonnative insects and diseases invade U.S. forests, researchers tested conflicting ideas about biodiversity. The first is that having more tree species can facilitate the diversity of pests by providing more places for them to gain a toehold. Another possibility is that tree biodiversity can have protective effects for forests, such as by diluting the pool of host trees and making it harder for pests to become established.

“We found that both facilitation and dilution seem to be happening at the same time,” Potter says. “What we found is that native tree biodiversity really is important, but it’s important in different ways at different times.”

Combining two national county-level data sets, researchers found that relationships between tree diversity and pest diversity follow a hump-shaped curve.

“As you have an increasing number of tree species, you have an increasing number of pest species, up to an inflection point where that relationship changes,” Potter says. “Then you have a decreasing number of pest species as the number of host tree species increases.”

Overall, counties where forests have 30 to 40 different host tree species tend to have the most nonnative pests. But the effects depend on whether the invader is a specialist that can infest only a single tree species or whether it’s a generalist, like the gypsy moth, which can spread to more than 60 different hosts.

“What we see is that forests in the Midwest and up into New England are at the middle part of that hump-shaped curve in terms of the number of host tree species, and those are places where there have been a lot of insect and disease problems,” Potter says.

“Out West we have fewer insect and disease pests, but in some cases they still do a lot of damage because the forests are not diverse. If you have a specialist pest come in and knock back one of the major components of your biodiversity, then that can have a greater impact. An example of how that works would be Sudden Oak Death, a disease in California that’s affecting oaks there.”

Researchers with the U.S. Forest Service, Purdue, NC State, Czech University of Life Sciences and Duke collaborated on the study, which used two large datasets. The U.S. Forest Inventory and Analysis, a national forest census, contains information from 135,000 forested plots across the U.S. where crews regularly measure trees and check environmental conditions. For this study, the FIA data were used to compile counts of tree species for each of 2,098 counties. The Alien Forest Pest Explorer database offers a county-level record of the presence or absence of nonnative insects and diseases, including 66 used for this study.

Researchers also examined other factors that could affect pest invasions, such as human population density and environmental conditions, including precipitation, elevation and average temperature. Tree biodiversity was a better predictor of nonnative pests, Potter says.

Results could help prioritize monitoring efforts for forests most at risk for future pest invasions, he says.

“The unfortunate reality is that a lot of times we don’t notice these exotic pests and diseases until they’ve gotten established and start having an impact on our native species, when it’s almost too late.”

Read the paper: PNAS

Article source: NC State University

Image credit: Kevin M. Potter, NC State University