Diversity, dynamics, direction, and magnitude of high-altitude migrating insects in the Sahel

Long-distance migration of insects impacts food security, public health, and conservation–issues that are especially significant in Africa. Windborne migration is a key strategy enabling exploitation of ephemeral havens such as the Sahel, however, its knowledge remains sparse. In this first cross-season investigation (3 years) of the aerial fauna over Africa, we sampled insects flying 40–290 m above ground in Mali, using nets mounted on tethered helium-filled balloons. Nearly half a million insects were caught, representing at least 100 families from thirteen orders. Control nets confirmed that the insects were captured at altitude. Thirteen ecologically and phylogenetically diverse species were studied in detail. Migration of all species peaked during the wet season every year across localities, suggesting regular migrations. Species differed in flight altitude, seasonality, and associated weather conditions. All taxa exhibited frequent flights on southerly winds, accounting for the recolonization of the Sahel from southern source populations. “Return” southward movement occurred in most taxa. Estimates of the seasonal number of migrants per species crossing Mali at latitude 14°N were in the trillions, and the nightly distances traversed reached hundreds of kilometers. The magnitude and diversity of windborne insect migration highlight its importance and impacts on Sahelian and neighboring ecosystems

Windborne long-distance migration of malaria mosquitoes in the Sahel

Over the past two decades efforts to control malaria have halved the number of cases globally, yet burdens remain high in much of Africa and the elimination of malaria has not been achieved even in areas where extreme reductions have been sustained, such as South Africa1,2. Studies seeking to understand the paradoxical persistence of malaria in areas in which surface water is absent for 3–8 months of the year have suggested that some species of Anopheles mosquito use long-distance migration3. Here we confirm this hypothesis through aerial sampling of mosquitoes at 40–290 m above ground level and provide—to our knowledge—the first evidence of windborne migration of African malaria vectors, and consequently of the pathogens that they transmit. Ten species, including the primary malaria vector Anopheles coluzzii, were identified among 235 anopheline mosquitoes that were captured during 617 nocturnal aerial collections in the Sahel of Mali. Notably, females accounted for more than 80% of all of the mosquitoes that we collected. Of these, 90% had taken a blood meal before their migration, which implies that pathogens are probably transported over long distances by migrating females. The likelihood of capturing Anopheles species increased with altitude (the height of the sampling panel above ground level) and during the wet seasons, but variation between years and localities was minimal. Simulated trajectories of mosquito flights indicated that there would be mean nightly displacements of up to 300 km for 9-h flight durations. Annually, the estimated numbers of mosquitoes at altitude that cross a 100-km line perpendicular to the prevailing wind direction included 81,000 Anopheles gambiae sensu stricto, 6 million A. coluzzii and 44 million Anopheles squamosus. These results provide compelling evidence that millions of malaria vectors that have previously fed on blood frequently migrate over hundreds of kilometres, and thus almost certainly spread malaria over these distances. The successful elimination of malaria may therefore depend on whether the sources of migrant vectors can be identified and controlled

DNA barcoding Brooklyn (New York): A first assessment of biodiversity in Marine Park by citizen scientists

<div><p>DNA barcoding is both an important research and science education tool. The technique allows for quick and accurate species identification using only minimal amounts of tissue samples taken from any organism at any developmental phase. DNA barcoding has many practical applications including furthering the study of taxonomy and monitoring biodiversity. In addition to these uses, DNA barcoding is a powerful tool to empower, engage, and educate students in the scientific method while conducting productive and creative research. The study presented here provides the first assessment of Marine Park (Brooklyn, New York, USA) biodiversity using DNA barcoding. New York City citizen scientists (high school students and their teachers) were trained to identify species using DNA barcoding during a two–week long institute. By performing NCBI GenBank BLAST searches, students taxonomically identified 187 samples (1 fungus, 70 animals and 116 plants) and also published 12 novel DNA barcodes on GenBank. Students also identified 7 ant species and demonstrated the potential of DNA barcoding for identification of this especially diverse group when coupled with traditional taxonomy using morphology. Here we outline how DNA barcoding allows citizen scientists to make preliminary taxonomic identifications and contribute to modern biodiversity research.</p></div

Overview of plants identified by this project, organized by taxonomic level.

<p>Of the 116 collected and identified plants the majority were in the Asterales (n = 32; 27.6% of total plants) and Poales (n = 28; 24.1% of total plants) orders, with the highest number of species within each order falling in the Asteraceae (n = 32; 27.6% of total plants) and Poaceae families (n = 28; 24.1%). Taxonomic groups in legends are organized from largest to smallest.</p

Sampling sites for this study.

<p>Samples were obtained at Marine Park (Brooklyn, New York, USA) in two localities: at a restored, more natural habitat (# 1 above) and an unrestored, disturbed habitat (#2 above). The figure was prepared based on data available from the U.S. Geological Survey Department of the Interior (USGS) public domain (USGS-viewer.nationalmap.gov) and edited by Chun-hua Yang, DNALC.</p

Overview of the twelve novel DNA barcodes generated by the participants of the Urban Barcoding Project Institute at GESC in the summers of 2014 and 2015.

<p>Overview of the twelve novel DNA barcodes generated by the participants of the Urban Barcoding Project Institute at GESC in the summers of 2014 and 2015.</p

The DNA barcoding workflow.

<p>Biochemical protocols at the website <i>DNA Barcoding 101</i> (<a href="http://www.dnabarcoding101.org/" target="_blank">www.dnabarcoding101.org</a>) and bioinformatics tools at <i>DNA Subway</i> (<a href="http://www.dnasubway.org/" target="_blank">www.dnasubway.org</a>) support all parts of the workflow. (A) Participants collected samples and extracted genomic DNA, generated DNA barcodes using PCR, verified the correct size by gel electrophoresis and sent amplicons for automated sequencing. Sequence data was uploaded to the internet-based DNA barcoding bioinformatics pipeline <i>DNA Subway</i>, and participants assembled contigs, compared them to additional sequences and analyzed sequence data for potential export to GenBank. (B) Trace file of a DNA sequence from a local ant sample. (C) DNA reads are paired and manually edited to create consensus sequence. (D) Top BLAST hits for an ant consensus sequence identifying it as <i>Tetramorium caespitum</i>. (E) <i>DNA Subway</i> integrated export function for novel DNA barcodes to GenBank. (F) User-friendly <i>DNA Subway</i> interface. (G) <i>DNA Subway’s</i> “Blue Line” for DNA barcoding and phylogenetics allows for sequence editing, performing a BLAST search, and phylogenetic tree building on an intuitive, open-source platform.</p

List of ant samples, and their corresponding morphological and DNA barcoding identifications.

<p>List of ant samples, and their corresponding morphological and DNA barcoding identifications.</p