Nav: Home

Sequencing pollen DNA to discover insect migratory routes

November 09, 2018

Metabarcoding, a technique of mass DNA sequencing, allows for tracing migratory routes of insects, an understudied subject due to technical limitations. A small DNA fragment of the pollen that insects transport is used as a barcode to identify the plant species they visited previously.

This British Ecological Society funded study shows that transcontinental pollination mediated by migrating insects is possible and, therefore, various plants located very far apart can mix.

The migration of insects is a natural phenomenon as important as it is unknown. In fact, it has only been studied in depth in some emblematic species, such as the migratory locust and the monarch butterfly. The reasons, in short, are the technical limitations to study this behaviour.

Now, in a study published in the journal Molecular Ecology Resources, researchers from Institut de Biologia Evolutiva (IBE: CSIC - Universitat Pompeu Fabra), Institute of Botany of the Polish Academy of Sciences and Universitat Autònoma de Barcelona (UAB), have developed a technique that eludes these limitations and therefore allows to easily study the migratory movements of insects: the DNA metabarcoding analysis of the pollen transported by insects.

By means of this technique, a small DNA fragment can identify the plant species to which the pollen belongs to, analogously to a barcode. By knowing the geographic distribution of the plant species detected, we can infer the place where the insect was feeding and, therefore, its migratory route.

Previously, long-distance migrations were studied either by capture-mark-recapture experiments, or through telemetry using radio trackers. These two methods, however, have great disadvantages: the recapture rate of marked individuals is extremely low; as for telemetry, it is only feasible to track the largest insects over short distances, given the weight of the transmitters and their short battery life.

Another method to study long-distance migrations involves analysing hydrogen or carbon isotopes present in organic tissues, because they provide information about where the insects were born. However, the resolution of isotope analyses is low and this method is only useful for insects that migrate on very large distances.

Tell me what flowers you have visited, and I'll tell you where you are from

When insects feed on the flowers, pollen is deposited on their bodies and can be transported over long distances. Taxonomical classification of the pollen grains using optical and electron microscopy, however, is often impossible at species level. In addition, it requires a great investment of time and having specialized knowledge in taxonomy, which is why this is an unsuitable tool for large-scale studies.

However, as explained by Roger Vila, one of the authors of the study and principal investigator at IBE, «the development of next-generation sequencing technologies has made it possible to massively sequence the genetic material present in a sample of pollen from various individuals».

This is the metabarcoding technique, in which the species are identified from a small region of the DNA that performs a function analogous to that of a barcode.

The researchers used the metabarcoding technique to study the pollen from 47 specimens of migrating painted lady butterflies (Vanessa cardui), which have been captured on the Spanish Mediterranean coast during spring. The objective was to test if the sequences obtained were from endemic African plant species and to shed light on the migratory circuits of these butterflies.

The analysis revealed pollen of 157 species of plants of 23 different orders; the vast majority were, indeed, African and not present in Europe.

The painted lady has recently been shown to be the butterfly species that performs the longest migrations in the world, traveling every year between tropical Africa and Europe (back and forth, crossing the Sahara desert) in successive generations, although the precise routes are still unknown.

Transcontinental pollination

The results of this study represent an important discovery from the point of view of the plants, because it demonstrates, for the first time that the transcontinental pollination by migratory insects is possible. It is a phenomenon to be taken into account both in wild and in cultivated plants because it enables plants from very distant locations to mix.

«We hope that the technique opens a new line of research that helps to clarify which insects migrate, which routes they follow and when, as we still do not know much about the impact of insect migration for ecosystems and the transmission of diseases», says Gerard Talavera, co-author of the article, researcher at IBE and National Geographic Explorer.
-end-
The project was funded by the National Geographic Society, the British Ecological Society, the European Community and the Spanish Ministerio de Ciencia, Innovación y Universidades.

British Ecological Society

Related Dna Articles:

Penn State DNA ladders: Inexpensive molecular rulers for DNA research
New license-free tools will allow researchers to estimate the size of DNA fragments for a fraction of the cost of currently available methods.
It is easier for a DNA knot...
How can long DNA filaments, which have convoluted and highly knotted structure, manage to pass through the tiny pores of biological systems?
How do metals interact with DNA?
Since a couple of decades, metal-containing drugs have been successfully used to fight against certain types of cancer.
Electrons use DNA like a wire for signaling DNA replication
A Caltech-led study has shown that the electrical wire-like behavior of DNA is involved in the molecule's replication.
Switched-on DNA
DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices.
Researchers are first to see DNA 'blink'
Northwestern University biomedical engineers have developed imaging technology that is the first to see DNA 'blink,' or fluoresce.
Finding our way around DNA
A Salk team developed a tool that maps functional areas of the genome to better understand disease.
A 'strand' of DNA as never before
In a carefully designed polymer, researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences have imprinted a sequence of a single strand of DNA.
Doubling down on DNA
The African clawed frog X. laevis genome contains two full sets of chromosomes from two extinct ancestors.
'Poring over' DNA
Church's team at Harvard's Wyss Institute for Biologically Inspired Engineering and the Harvard Medical School developed a new electronic DNA sequencing platform based on biologically engineered nanopores that could help overcome present limitations.

Related Dna Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Setbacks
Failure can feel lonely and final. But can we learn from failure, even reframe it, to feel more like a temporary setback? This hour, TED speakers on changing a crushing defeat into a stepping stone. Guests include entrepreneur Leticia Gasca, psychology professor Alison Ledgerwood, astronomer Phil Plait, former professional athlete Charly Haversat, and UPS training manager Jon Bowers.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".