horticulture

Scientists forecast where is the highly invasive fall armyworm to strike next

*The fall armyworm is the larvae of the fall armyworm moth species Spodoptera frugiperda. Photo by Centre for Agriculture and Bioscience International (CABI).*

Staple and economically important crops throughout the world could be at serious risk if efficient measures are not taken soon

Known to be feeding on many economically important crops cultured across the world, including maize, rice, sugarcane, sorghum, beet, tomato, potato, cotton and pasture grasses, the larvae of the native to the Americas fall armyworm moth seem to have already found a successful survival strategy in a diverse and changing world.

Furthermore, having taken no longer than 2 years to invade and spread throughout most of sub-Saharan Africa, the pest has already demonstrated its huge potential in severely affecting livelihoods around the globe.

A recent study in the open-access journal NeoBiota, conducted by Dr Regan Early of Exeter University, United Kingdom and her colleagues at the Centre for Agriculture and Bioscience International: Dr Pablo González-Moreno, Sean T. Murphy and Roger Day, looks into the factors and likelihood for the fall armyworm (Spodoptera frugiperda) to spread to other regions and continents.

Invasion progress

The alarming reports started in January 2016 when major outbreaks of fall armyworms were registered in Nigeria and Ghana, preceding signals from Benin, Sao Tomé and Togo shortly after. By September 2017, the pest had already been confirmed in 28 sub-Saharan African countries, with nine states expected to follow suit.

While unaided dispersal of the species in Africa is considered unlikely, it is speculated that the pest had arrived on a passenger flight from America. To back this theory, the researchers point out that the first countries to house the invader are also the major air transportation hubs in Africa and have warm, moist climate similar to those in the pest’s natural habitat.

In the aftermath, recent estimates point to up to 50% maize yield loss in Africa attributed to the fall armyworm. However, scientists believe that the species is far from finished spreading and is highly likely to invade new continents.

Who’s next?

To find what makes a region an inviting new habitat for the fall armyworm, hence which countries face the highest threat of future invasions, the researchers looked into both the native and African distributions of the species, and the effects different temperatures and precipitation levels have on it.

Having concluded that the lowest temperatures and the maximum amount of rain play the main role in determining whether the fall armyworm is to establish in a certain region, the scientists concluded that South and Southeast Asia, as well as Australia face the most serious risk, since their climate is very similar to the one preferred by the pest.

However, the authors of the study remind that this forecast shall in no way be taken with a sigh of relief by countries with milder climatic conditions. While the moth needs particular temperature and precipitation amplitudes at its year-round habitat, it could easily travel back and forth up to several hundred kilometres during its seasonal migrations. Therefore, if the fall armyworm establishes in North Africa, it could migrate to Europe during the warmer months, just like it has already been observed to travel from its year-round localities in Argentina, Texas and Florida all the way to Canada’s Québec and Ontario in the north.

The increasing transportation and international trade are also likely to facilitate the further spread of the fall armyworm outside Africa. The scientists conclude that, given the current travel air routes, it is Australia, China, India, Indonesia, Malaysia, Philippines and Thailand which are at high risk of becoming the pest’s new habitat.

*The map illustrates the likelihood of the establishment of the fall armyworm if introduced at different parts of the world. Image by Regan Early.*

What’s next?

Having concluded that there is a considerable potential for near global invasion and seasonal migration of fall armyworm, the scientists call for vigilance from farmers and programme managers alike. They remind that early detection of small larvae is crucial, since it is only at this stage that chemical insecticides would work effectively.

“As fall armyworm has huge potential to affect staple and economic crops globally, we urgently need information on the pest’s potential distribution and environmental limitations,” comment the researchers.

“Management decisions would be improved by further research on fall armyworm’s seasonal migration and population dynamics and the environmental dependency of interactions with other species.”

###

Original source:

Early R, González-Moreno P, Murphy ST, Day R (2018) Forecasting the global extent of invasion of the cereal pest Spodoptera frugiperda, the fall armyworm. NeoBiota 40: 25-50. https://doi.org/10.3897/neobiota.40.28165

A preprint of the study was published earlier on bioRxiv.

Cage the fly: Walk-in field cages to assess mating compatibility in pest fruit flies

Fruit flies mating compatibility studies have been examined by an international team of researchers to assess the usefulness of walk-in field cages in studying the sexual behavior within fruit fly species complexes and recognition of taxonomically misplaced flies. In addition, they have also evaluated the relevant chemical signals during pheromone emission for species discrimination. The experimental part was conducted with the support of Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture in Seibersdorf, Austria. Their findings are published in the open-access journal ZooKeys.

Evolution has led to divergence in some groups, which sometimes results in new, yet very similar species. Hence, they might successfully confuse taxonomists, making them coin terms like ‘cryptic’ species, or in other words, distinct species misplaced under the same name.

However, these species are kept isolated from each other via reproductive barriers. Preventing interbreeding and hybridization, they can be ecological and mechanical, but also behavioral (i.e. sexual). The latter are behaviors or signals that affect recognition within a species, as well as attractiveness and mate choice. They affect their evolution and therefore, are key elements in species differentiation.

The authors of the present paper have found that the walk-in field cages methodology provides an appropriate ground to study these issues. By applying it, researchers around the world are able to detect pest species among others when occurring in the same populations.

Apart from taxonomic value, the scientists also point out the significance of these findings to pest management. As the studied pest fruit fly species are agricultural pests of major economic importance, assessing their mating behaviour, including the pheromones the males emit when attracting partners, can be utilised in the development of highly specific control methods. For instance, there is the sterile insect technique that involves releasing males reproductively sterilised via ionizing radiation into a wild population, where they inseminate the pest females with sterile sperm so that they end up with unviable offspring.

The main advantage of using walk-in field cages, rather than small laboratory-based ones, is that they provide semi-natural conditions under which they are “reliable and powerful tools to measure the level of mating compatibility among different species and populations of a putative single species.”

However, the present paper highlights that such an approach is only to be applied as a part of integrative taxonomic analyses, together with molecular, physiological and morphological approaches when assessing to which species a particular pest population belongs.

###

Original source:

Juarez ML, Devescovi F, Brizova R, Bachmann G, Segura DF, Kalinova B, Fernandez P, Ruiz MJ, Yang J, Teal PEA, Caceres C,, Vreysen MJB, Hendrichs J, Vera MT (2015) Evaluating mating compatibility within fruit fly cryptic species complexes and the potential role of sex pheromones in pre-mating isolation. In: De Meyer M, Clarke AR, Vera MT, Hendrichs J (Eds) Resolution of Cryptic Species Complexes of Tephritid Pests to Enhance SIT Application and Facilitate International Trade. ZooKeys 540: 125-155. doi: 10.3897/zookeys.540.6133

Known from flower stalls as ‘Big Pink’ orchid proved to be an undescribed wild species

As easy as it might seem, seeking new species among cultivated plants could be actually quite tricky. While looking into the undescribed orchid, known at the market as ‘Big Pink’, Bobby Sulistyo and his team were likely to find yet another man-made hybrid. In reality, they are now describing as ‘new’ a wild orchid species that has been sitting at the flower stalls since 2013. The story behind their discovery is published in the open access journal PhytoKeys.

While studying a cultivated plant might be quite a motivator and serve as a starting point for scientific quests around the world, the assumptions that one has found a new species at the florist’s could easily be wrong. Not only is the place of origin, written on the label, often doubtful, but there is always the chance of accidentally describing a man-made hybrid as a new species.

Such could have been the case of Bobby Sulistyo and his team when they discovered that although previously assumed impossible, the relatives of ‘Big Pink’, they were surveying, could also make human-assisted hybrids. Moreover, both of the specimens they have had at hand had come from uncertain place of origin.

However, the scientists conducted a series of sophisticated DNA analyses to conclude that firstly, ‘Big Pink’ is a separate species within its genus and then, that there is no evidence for it being an artificial hybrid. Eventually, the species was found in the wild as well. As a result, the orchid species was given the official name Dendrochilum hampelii.

In the wild, ‘Big Pink’ is found at around 1,200 m above sea level in the Philippines, where it harmlessly plants its roots on tree trunks and branches among mosses.

So far, little is known about the orchid’s distribution in nature, so the researchers suggest its conservation status to be considered as Data Deficient according to the IUCN Red List of Threatened Species (IUCN 2012).

###

Original source:

Sulistyo B, Boos R, Cootes J, Gravendeel B (2015) Dendrochilum hampelii (Coelogyninae, Epidendroideae, Orchidaceae) traded as ‘Big Pink’ is a new species, not a hybrid: evidence from nrITS, matK and ycf1 sequence data. PhytoKeys 56: 83-97. doi:10.3897/phytokeys.56.5432

World-famous, yet nameless: Hybrid flowering dogwoods named by Rutgers scientists

Garden lovers and horticulturalists now have two new species names to add to their vocabulary and memory. The world’s most commercially successful dogwood garden trees have finally received proper scientific names decades after their introduction into horticulture. The big-bracted, or flowering, dogwoods are beloved trees with cloud-like branches blossoming in early spring in white, sometimes red or pink. The new scientific names are published by a team of American scientists in the open-access journal PhytoKeys.

The two hybrid species were artificially hybridized at Rutgers University by renowned ornamental tree breeder Dr. Elwin R. Orton decades ago and are now commonly grown across the United States, Europe and Japan. These two hybrids were developed from Florida, Kousa and Pacific dogwoods (Cornus spp.), all well known ornamental trees. The breeding program, which started in 1965, had the aim to create garden dogwoods with better aesthetic qualities, such as larger pink or red floral bracts, unique growth habits and better disease-resistance.

So, why do we need formal names? “Crucial to communication in all parts of our lives is the naming of objects and phenomena,” explains Mr. Mattera, a Rutgers University graduate student in the School of Environmental and Biological Sciences. “Humanity needs words to tell other people what we are talking about, and the words need to have uniform and clear meanings,” he adds. Before their publication these horticultural plants largely lived in a taxonomic no-man’s land and could not easily be placed into horticultural databases.

Co-author Dr. Lena Struwe, a botanist also at Rutgers University, explains that “Even artificial hybrids created by the fusion of species from separate pieces of the Earth are living, evolving things that need scientific names so they fit into our encyclopedias of life.” She continues, “even if these are mostly sterile, but stable, hybrids they are now widespread components of worldwide garden biodiversity that get pollinated by native insects and interact with other local native and non-native species.”

Common garden plant hybrids, even if artificially produced from wild species, need formal species names to promote international communication and further scientific understanding. “If you can’t put a name on something, you can’t explain what you see, own, or remember,” Dr. Lena Struwe explains and adds: “Names and words are the basis for the transfer of all knowledge”.

The new hybrid species Cornus × rutgersensis was created by the hand-crossing of a an Asian species, the Kousa dogwood, with the common Florida dogwood. Most gardeners and horticulturist will recognize the pink-bracted cultivar Stellar Pink®, the most successful Cornus × rutgersensis hybrid. The crosses made by Dr. Orton were the world’s first known hybrid crosses between these two species. Many familiar with this hybrid may recall hearing this name before, and they probably have. Cornus × rutgersensis and similar names had been used informally by those in the horticultural trade before, but now the authors hope to provide clarity by formally publishing the name in the present paper. The researchers suggest Rutgers’ dogwood as the common-name for this hybrid.

The second hybrid, Cornus × elwinortonii, honors career-long ornamental plant breeder Dr. Orton from Rutgers University in New Brunswick, NJ (United States). This cross produced a hybrid with larger white petal-like bracts around each flower head and resistance to the dogwood-killing fungal disease, dogwood anthracnose, that affects the native Pacific and Florida dogwoods. The cultivar Venus® is the most prominent example of this hybrid. The researchers have proposed the common name Orton’s dogwood for horticultural usage.

Both hybrid species represent long-distance artificial crosses of wild species that would never meet in nature, which were further developed into beloved commercial garden plants. Despite their parents being quite different in their flowers and fruits, the two new hybrid species are a clear combination of their ancestors.

“Such intermixing of parental characters is the key to successful plant breeding and artificial selection of new horticultural and agricultural varieties that can provide new forms of beauty, as well as new disease- and stress-resistant plants,” explains Rutgers University plant breeder Dr. Thomas Molnar, in Department of Plant Biology and Pathology.

According to the International Code of Nomenclature for algae, fungi, and plants (ICN), all proposed scientific names, including hybrid names, require that they are formally published and described in a scientific publication, as well as represented by a type specimen in a scientific collection. The formal types of these new hybrids will be deposited in several herbaria, and are also represented by living trees at Rutgers University in New Jersey (USA).

###

Original source:

Mattera R, Molnar T, Struwe L (2015) Cornus × elwinortonii and Cornus × rutgersensis(Cornaceae), new names for two artificially produced hybrids of big-bracted dogwoods.PhytoKeys 55: 93-111. doi: 10.3897/phytokeys.55.9112