Gino Brignoli

What is the cause of the Zika outbreak in the Americas?

I recently read an article by Claire Bernish¹that said that the release of GM mosquitoes was the cause of the Zika virus outbreak in Brazil – this immediately set alarm bells ringing. As it turns out, any real evidence to support these claims was lacking and Christie Wilcox, writing for Discover magazine,²has done a fantastic job in demolishing this argument by showing the inaccuracy of the dates and the distances involved. The GMM release site was 300 km away from the epicentre of the Zika outbreak and the release was in 2011-12, not 2015 as was stated in a similar article by Oliver Tickell in The Ecologist.³

“The Earth is round, not flat (and it’s definitely not hollow). Last year was the hottest year on record, and climate change is really happening … And FFS, genetically modified mosquitoes didn’t start the Zika outbreak.” – Christie Wilcox

Although I have my own concerns regarding the control of mosquitoes by means of genetic modification, I think that the scare-mongering surrounding GMMs and the Zika virus does more harm than good – especially when the scientific data is at best deficient and at worst entirely fabricated. Amongst the inevitable conspiracy theories that have surfaced the “best” argument that has been put forward seems to be that “Nature will find a way”. On another note, I also find the seeming disdain of laboratory scientists towards ecologists to be somewhat worrying and rather baffling. These fields have so much potential crossover that I hope any enmity can be set aside so that robust scientific research and enquiry can be conducted in a collaborative way.

image-20160126-19651-1eko782 — Aedes aegypti. Emil August Goeldi (1859-1917). Source: Wikimedia Commons.

This brings me to Amy Vittor’s excellent and comprehensive assessment of the potential sources of Zika in the Americas and her highly plausible proposition for why we are seeing such high infection rates.⁴ The Zika virus was first recorded in a rhesus monkey in the Zika forest in Uganda in 1947, then in the Aedes africanus mosquito the following year. The virus is now also found to be transmitted by Ae. albopictus and Ae. aegypti mosquitoes. These species are now found throughout the tropics and subtropics and as their ranges have expanded, so too has the possible reach of Zika and other mosquito-borne diseases associated with them. It wasn’t until 2007 that a large-scale outbreak of Zika infecting humans first occurred, infecting 75% of the population of the island of Yap in Micronesia.^{4, 5}

The spread of the virus is in all likelihood the result of human-aided dispersal of both the virus and Aedes mosquitoes. As the virus may not be detected by infected humans (up to 80% of infected people do not show any symptoms)^4,5 and there is currently no cure, it is possible for an infected person to travel to an area where the virus has not been recorded and to spread it to previously unexposed mosquito populations there, so creating new vectors.

zika-virus-epidemiology — Source: Laboratoryinfo.com ⁶

But what has changed to bring about this rapid spread of the disease in the Americas? If we accept that international travel by humans and the worldwide transportation of goods have enabled the means to transport the disease and its vectors, why are we only seeing these effects in the Americas now? There are a combination of further factors that have, as Vittor points out, come together to create the perfect environment for Zika to take hold and spread, including: the creation of more suitable mosquito habitat as a result of deforestation and planting arable crops or urbanisation; climate-change linked increases in temperature and/or humidity in areas that were previously too cold or dry to support mosquito populations; the failure of previous Aedes aegypti population control programmes; and the large pool of susceptible human hosts living in close proximity to each other and to these mosquito-favourable habitats.⁴

Mark Lynas, writing in The Guardian newspaper, also very effectively takes on the various GM mosquito conspiracy theories and then goes on to conclude that innocent lives will be lost if we do not embrace this technology.⁷ Although there is no doubt that mosquitoes are responsible for spreading an array of terrible diseases; the fact that we have created the conditions and opportunities for the mosquitoes and these diseases to extend beyond their historical ranges and infect many more people must surely be accepted as our own responsibility. I think it is a sad indictment of our scientists and ecologists if they cannot (or will not) work together towards an overarching framework to protect people from the effects of our own actions. We need to promote and encourage the use of ‘good science’ to inform our decisions and ultimately our actions.

Further research into and analysis of mosquito ecology is urgently required so that we can more fully understand the implications of mosquito eradication (by genetic or conventional controls) on the various associated ecosystems and diseases. If we do not ask questions about the potential impacts of our proposed actions, we are destined to repeat the same mistakes that have led us to this point. Perhaps, we should also examine the implications of increased habitat loss, climate change and urbanisation, and consider whether we are prepared to live with the consequences or take action to limit the most deleterious effects.

References:

1. Bernish, C. (2016) Zika Outbreak Epicenter in Same Area Where GM Mosquitoes Were Released in 2015 http://theantimedia.org/zika-outbreak-epicenter-in-same-area-where-gm-mosquitoes-were-released-in-2015/

2. Wilcox, C. (2016) No, GM Mosquitoes Didn’t Start The Zika Outbreak. http://blogs.discovermagazine.com/science-sushi/2016/01/31/genetically-modified-mosquitoes-didnt-start-zika-ourbreak/#.VrXcU8eExo4

3. Tickell, O. (2016) Pandora’s box: how GM mosquitos could have caused Brazil’s microcephaly disaster http://www.theecologist.org/News/news_analysis/2987024/pandoras_box_how_gm_mosquitos_could_have_caused_brazils_microcephaly_diasaster.html

4. Vittor, A. (2016) Explainer: where did Zika virus come from and why is it a problem in Brazil? https://theconversation.com/explainer-where-did-zika-virus-come-from-and-why-is-it-a-problem-in-brazil-53425

5. Duffy, R. et al. (2009) Zika virus outbreak on Yap Island, Federated States of Micronesia. New England Journal of Medicine. 360(24):2536-43 http://www.nejm.org/doi/full/10.1056/NEJMoa0805715#t=articleTop

6. Giri, D. (2016) Zika Virus : Structure, Epidemiology, Pathogenesis, Symptoms, Laboratory Diagnosis and Prevention http://laboratoryinfo.com/zika-virus-structure-epidemiology-pathogenesis-symptoms-laboratory-diagnosis-and-prevention/#sthash.BYXGYuyI.dpuf

7. Lynas, M. (2016) Alert! There’s a dangerous new viral outbreak: Zika conspiracy theories http://www.theguardian.com/world/2016/feb/04/alert-theres-a-dangerous-new-viral-outbreak-zika-conspiracy-theories

Genetically modified insects and the precautionary principle

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Last week the Guardian newspaper reported on the findings from the UK House of Lords’ science and technology committee into the development and use of GM insects. According to the committee’s chairman, Lord Selborne:

“GM insect technologies have the potential not only to save countless lives worldwide, but also to generate significant economic benefits for UK plc, where we are an acknowledged world leader.”

No surprises there. The case for GM insects to be developed as a form of vector control has many proponents and seizing an economic opportunity is to be expected from the Lords. Apart from a cursory explanation of the means of developing GM insects, and a mention of the fact that the committee would like to see a reform of European Union regulation around GMOs (more on this later), the reporter fails to consider any environmental issues that may arise from the release of transgenic insects, in what seems to me to be a failure of research and the rehashing of the committee’s summary report.

Thankfully, in an attempt to provide a balanced argument the Guardian also published a piece that was more critical of the report, describing it as “an unsophisticated form of moral blackmail” and laying out the possible extinction risks associated with gene drive systems. The scientific knowledge gap is highlighted by these authors, who write:

“We are not against GM insects. Our point is that we do not know enough. Nobody knows enough.”

Though I commend these authors for responding to the Lords’report in a more critical way, there are still a couple of findings in the report that hadn’t been directly addressed and which I think need exploring further.

The first is the issue of EU regulations of GMOs that the Lords describe as “failing lamentably” and would like to see amended. This critique is aimed at EU Directive 2001/18/EC which states that “due attention be given to controlling risks from the deliberate release into the environment of genetically modified organisms”. This is to be conducted through case-by-case environmental risk assessments, public consultation, a requirement to consult all relevant scientific and ethical committees, and development of “a mechanism allowing the release of the GMOs to be modified, suspended or terminated where new information becomes available on the risks of such release” before consent will be granted. It is a very robust piece of legislation which, when linked with Regulation (EC) No 1946/2003 that restricts the release and transboundary movement of any GMO within EU member states, makes this not “lamentable” as the Lords would have us think, but sound legislation based on the Cartagena Protocol which states that products from new technologies must be based on the precautionary principle and allow nations to balance public health against economic benefits. And which allows countries to ban imports of a genetically modified organisms if they feel there is not enough scientific evidence that the product is safe. It seems to me that an attack on the governing EU legislation is also an attack on the Cartagena Protocol which environmentalists need to be aware of.

The international consensus of the definition of the Precautionary Principle is:

“When human activities may lead to morally unacceptable harm that is scientifically plausible but uncertain, actions shall be taken to avoid or diminish that harm.”

And this brings me to my second concern about the House of Lords report, wherein Professor Rosemary Hails states that:

“the Precautionary Principle properly applied would also take into account the risks of not developing a particular technology and the benefits forgone. It is a misuse of the Precautionary Principle that has led us to this place.”

This reconstitution of the Precautionary Principle is a matter of great concern and has already been discussed at some length by the House of Commons Science and Technology Committee in their Fifth Report: Advanced Genetic Techniques for Crop Improvement: Regulation, Risk and Precaution wherein Sir Mark Walport framed the precautionary principle not as a response to scientific uncertainty, but as a guide to evidence-based decision-making. He said:

“Decisions must be informed by the best evidence and expert advice. The application of the ‘precautionary principle’ can help to guide this. This simple idea just means working out and balancing in advance all the risks and benefits of action or inaction, and to make a proportionate response. All too often, people citing this principle simply overreact: if there is any potential hazard associated with an activity, then it should not be done, or, if it is already being done, it should be stopped.”

By removing the imperative for evidence and advice that is provided to governments to be based on the principles and rigour of scientific enquiry, the report is effectively providing ministers with a means of bypassing environmental legislation. A recent example of this is when George Eustice MP recently cited food security as a reason to maintain the use of neonicotinoid pesticides under this bastardised definition of the Precautionary Principle.

If it were as simple as Sir Mark maintains to identify and stop hazardous activities we would not be facing some of the world’s current health and environmental catastrophes. That is why we must legislate against them and that is why scientific evidence needs to be the basis for that legislation. And when that evidence is lacking or inconclusive, aren’t we safer not taking the risk in the first instance? If, as Prof. Hails maintains we need to consider the risks of not using certain technologies for their potential benefits we have to ask ourselves whose benefits are we talking about.

The Great Pottery Throw Down

The title of this blogpost is taken from the latest BBC television series that has just finished screening in the UK. The premise for this series is based on the model developed for the hugely successful The Great British Bake Off, in which contestants compete against each other day-after-day to produce a variety of baked goods that are then judged by experts. Replace baked goods for ceramics and you will have grasped the intricacies of The Great Pottery Throw Down in its entirety. But what, if anything, is the significance of this to the study of invertebrates?

Well, having recently read Animal Architecture by Ingo Arndt and marvelled at the complexity and ingenuity of animals to create structures such as the heaped nests of wood ants, the towering cathedrals of termites and the delicately partitioned nests of paper wasps; I was rather taken with the notion of insects as ‘makers’. Serendipitously, I stumbled across the website of naturalist and artist, John Walters – specifically across his marvellous illustrations and accounts of Heath Potter Wasps, Eumenes coarctatus.

wasp_november_2009-1 — Eumenes coarctatus. Source: Wikipedia

Potter wasps, Eumeninae, are the most diverse group of Vespidae, with over 3,500 species in 210 genera found throughout the world. Of these, 23 species in 9 genera are found in the UK. They derive their common name of potter (or mason) wasps from the fact that the females tend to construct nests from mud and clay. These nests can take multiple forms, but one of the most elegant (in my view) is the vase-shaped nest of Eumenes coarctatus, the solitary Heath Potter Wasp.

Using heather, gorse or dead grass stems as nesting sites, the female will build her clay vessel over the course of two to three hours. During this time she will repeatedly fly from a water source to a quarry site, where she will form a ball of mud in her jaws, which is then transported to the construction site where she builds the nest. Once she has shaped the neck and lip of the nest she lays a single egg in the chamber suspended on a strand of silk. She will then search for, sting and collect a number of small caterpillars, especially pug and horse chestnut moth larvae, from the heathland vegetation and then fills the pot with them. A final trip to the water source and quarry then provides enough clay to seal the pot with between 9 and 38 paralysed caterpillars trapped inside. A female heath potter wasp may produce up to 25 pots in her lifetime (2 to 3 months) and occasionally she will cluster pots as shown in the series of photographs below. It is possible that these clusters prefigure the development of eusocial colonies as seen in some other vespids.

index.php — Development of a cluster of clay nest cells built by a single Eumenes coarctatus. Bovey Heath, Devon. Photos by John Walters.

When the wasp larva hatches from its suspended egg it drops onto the paralysed prey on which it feeds for about a week before pupating. The emergence of the adult depends on the timing of the building of the pot. If the pot was built before the end of June, the adult wasp will emerge 2 to 3 weeks later; if the pot is built in early July, the adult will still emerge in the same year; however, if the pot is built after this date emergence will be delayed until the following April or May.

potterwasps19july2012boveyheath — Illustration of Heath Potter Wasps taken from the field notes of artist and naturalist John Walters.

Though the E. coarctatus larvae are predatory, the adults feed on the nectar of heathland plants such as gorse, heather, bramble, angelica and alder buckthorn.

nhmsys0000875934-1 — Distribution map of Eumenes coarctatus in the UK. Source: NBN

Found on lowland heaths in England (from South Devon to East Sussex, and north to Buckinghamshire) the Heath Potter Wasp is classified as nationally scarce, though not designated a BAP species.

I also love Jean-Henri Fabre’s description of Eumenes taken from The Wonders of Instinct:

“A wasp-like garb of motley black and yellow; a slender and graceful figure; wings not spread out flat, when resting, but folded lengthwise in two; the abdomen a sort of chemist’s retort, which swells into a gourd and is fastened to the thorax by a long neck, first distending into a pear, then shrinking to a thread; a leisurely and silent flight; lonely habits.”

John Walters has also made a video of a wasp building a nest.

Michael Archer’s Key to British Potter and Mason Wasps is a very useful resource for identifying the various UK species.

The Little Bombardier

Best stay out of the way.

There are more than 500 species of Bombardier beetle (a form of ground beetle – Carbidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini all displaying the highly effective defence mechanism of releasing a superheated pulsing jet of noxious chemicals sprayed directly at would-be predators. I have always been fascinated by the ammunition of Bombardier beetles – their highly accurate and violent chemical attack brought on whenever you touch them – but it was only on reading Eisner’s essay that I started to fully grasp the incredible complexity of these beetles.

These diagrams are reproduced from Thomas Eisner’s fascinating book For Love of Insects which explores the variety of ways in which insects use chemicals for defence, signalling and prey capture. I cannot recommend this book highly enough for anyone interested in the pursuit of entomology or study of chemical ecology.

Screen Shot 2015-12-04 at 07.33.26 — Diagram of a bombardier beetle with its 2 glands in place. R = reservoir; r.ch = reaction chamber; gl = glandular tissue; dt = duct

Screen Shot 2015-12-04 at 07.38.01 — The mechanism of operation of the bombardier glands. E = enzymes in the reaction chamber; R indicates that either a hydrogen (H) atom or a methyl group (CH3) can occur at that site on the hydroquinone or quinone molecule.

The chemical process involves hydrogen peroxide rapidly decomposing into oxygen and boiling water, while the hydroquinones oxidize into benzoquinone in the beetle’s reaction chambers. This mix explodes out of the beetle with an audible popping sound, in a volley of rapid-fire blasts – in a manner likened to the pulsing propulsion system of Germany’s V-1 “buzz bomb” in WWII. The consequent foul chemical burn (at 100°C) incapacitates smaller attackers like ants, and deters larger predators such as the unfortunate frogs in one of Eisner’s experiments.

By examining the propulsion mechanism using high-speed synchrotron X-ray imaging Eric Arndt from MIT confirmed Eisman and his colleagues’ qualitative passive ‘pulse jet’ model. This research shows that a flexible membrane and a valve passively control the spray pulsation – as pressure increases in the reaction chamber because of the chemical explosion, the membrane stretches and the valve closes. The membrane then relaxes and the valve reopens once the pressure has been reduced following the ejection of the liquid, and so the process repeats.

The only UK resident species of bombardiers are Brachinus sclopeta, the streaked bombardier beetle, and Brachinus crepitans, the common bombardier beetle, and both are rarely seen. B. sclopeta is so rare that it has only recently been accepted as a native species (past records were thought to be of rare migrants) and prior to 2005 had been presumed extinct since 1928. Because the beetles prefer habitats with thin soil, rubble and bare ground they tend to favour brownfield sites and have been found in east London; but with the continuous and unrelenting development of this area, these beetles’ futures are very precarious despite being listed as UK BAP priority species, and considered critically endangered by the IUCN. However, insect charity Buglife worked with developers to secure a site near London City Airport that is now the only known intact colony of the species in the UK. You can read Richard Jones highly informative blog about the relocation and conservation of this species.

Brachinus crepitans, though more common than B. sclopeta, is restricted to Southern England and Wales and especially the coastal areas of the South-East where it is considered nationally scarce. It is more commonly found in continental Europe, central Asia, the Middle East and North Africa, with central Sweden being the northernmost extreme of its range.

Brachinus crepitans. Image source: Wikipedia

Distribution of Brachinus crepitans. Source: NBN Gateway

Usually seen in May and June, the beetle favours calcareous grasslands, arable field margins and chalk quarries. It is usually found in dry, sunny areas – typically under stones. Little is known about its life-cycle, but it is thought that the larvae are external parasites on the pupae of other species of beetle, particularly those of the ground beetle Amara convexiuscula and a staphylinid beetle, Ocypus ater.

I think these gorgeous and enthralling beetles definitely warrant being surveyed for this coming Summer.

References:

Eisner, T. (2003) For Love of Insects. Harvard University Press, Cambridge Ma.
Lyneborg, L. (1976) Beetles in colour. Blandford Press, Dorset.
Bombardier beetle found near Honeybourne. Worcestershire Biological Records Centre (December 2015): http://www.wbrc.org.uk/WorcRecd/Issue11/BombBtle.htm
Isaak, M. 1997. Bombardier Beetles and the Argument of Design (December 2015):
http://www.talkorigins.org/faqs/bombardier.html
Streaked Bombardier Beetle. Buglife (December 2015) https://www.buglife.org.uk/campaigns-and-our-work/streaked-bombardier-beetle
Brachinus sclopeta UK Priority Species Data Collation. Joint Nature Conservation Committee. http://jncc.defra.gov.uk/_speciespages/2093.pdf

Deep-sea biodiversity. A taster.

I want to share an amazing experience with you and to start to think about some of the issues raised in thinking about deep-sea biodiversity.

Back in 2012 I was incredibly fortunate to join an artist, Michelle Atherton, on a 4-hour-long submarine dive off the coast of Roatán, Honduras. We travelled up to 2,000 feet (610 metres) below sea level into the mesopelagic zone. All of the images in this blogpost are stills taken from the artist’s video during this trip.

go-deeper — The submarine, *Idabel*, that would take us on our exciting adventure 2,000 feet into the ocean depths.

Marine ecosystems support approximately half of global primary productivity and a range of ecosystem services operating from local to global scales. It is widely acknowledged that deep-sea ecosystems are the most extensive on Earth, represent the largest reservoir of biomass, and host a large proportion of undiscovered biodiversity (Ramirez-Llodra et al. 2011; Snelgrove et al. 2014; Tyler, 2003).

As sampling techniques and underwater exploration have improved, so the identification of new deep-sea species has grown year-on-year (Levin and Dayton 2009; Miloslavich and Klein, 2009; Ausubel et al. 2010; Danovaro, Snelgrove and Tyler, 2014). There is, however, still a lack of data for the middle waters and deep-sea ecosystems.

Screen Shot 2015-12-03 at 17.11.14 — On a cross-section of the global oceans, the spectrum from red to blue extends from many to few or no records. The records are concentrated near the shores and in shallow waters, while the largest habitat on Earth, the vast middle waters, is largely unexplored. Ausubel et al (2010)

Deep-sea megafauna have evolved a variety of adaptations to deal with the unique circumstances associated with the depths, such as: darkness, cold, high atmospheric pressure, ocean currents and unreliable food sources. This has resulted in peculiar morphological traits such as dark or red-colouration or even translucence to avoid detection; bioluminescence to attract prey often on a ‘lure’ or as a flash to serve as a warning or create confusion. The fauna are also quite often soft-bodied, small in size and sedentary or carried by the motion of the water.

Acanthacaris caeca

Squat lobster

Grimpoteuthis sp.

Bathypterois phenax

Chaunaax suttkusi

Leptostomias sp.

Polyp of a solitary octocoral

Chaunax stigmaeus

Mnemiopsis leidyi

Featured: Chaunax stigmaeus, the redeye gaper anglerfish; Leptostomias sp. dragon fish with bioluminescent chin barbel lure; unidentified polyp of a solitary octocoral; Dumbo octopod Grimpoteuthis sp.; squat lobster surrounded by snake stars Asteroschema sp. entwined with wire coral Cirrhipathes leutkeni; Acanthacaris caeca deep-sea lobster; bioluminescent comb jelly Mnemiopsis leidyi; Suttkus Sea Toad Chaunax suttkusi; and Bathypterois phenax tripod fish resting on the ocean floor.

With the recent discovery of Jurassic deep-sea fossils of extant families in the Austrian Alps providing evidence of colonisation of shallow waters from the deep (Thuy et al. 2014), the deep sea should be considered a biodiversity refugium.

Anthropogenic impacts such as bottom trawling and deep sea gas and oil extraction do, however, pose a significant threat to this biodiversity and ecosystem functioning (Costello et al. 2010; Baker, Ramirez-Llodra and Billet 2013; Ramirez-Llodra et al. 2011). It is imperative that an international conservation framework be agreed and implemented in order to preserve this ecosystem that we are only now beginning to explore.

tumblr_nfstu2PU4C1qbsotxo4_r1_1280 — A group of stalked sea lilies, Endoxocrinus parre carolinae, and three yellow featherstars, Crinometra brevipinna on a glass sponge with anemones on either side.

References:

Ausubel, J.H., Crist, D.T., Waggoner, P.E. eds. (2010). First Census of Marine Life 2010: Highlights of a Decade of Discovery. New York, Census of Marine Life.

Baker, M., Ramirez-Llodra, E., Billett, D. (2013). Preface [in special issue: Deep-Sea Biodiversity and Life History Processes] Deep Sea Research Part II: Topical Studies in Oceanography, 92. 1-8. DOI: 10.1016/j.dsr2.2013.03.040

Costello, M., Coll, M., Danovaro, R., Halpin, P., Ojaveer, H., & Miloslavich, P. (2010). A Census of Marine Biodiversity Knowledge, Resources, and Future Challenges. PLoS ONE, 5 (8) DOI: 10.1371/journal.pone.0012110

Danovaro, R., Snelgrove, P.V., Tyler, P. (2014). Challenging the paradigms of deep-sea ecology. Trends in Ecology and Evolution. 8:465-75. DOI: 10.1016/j.tree.2014.06.002

Levin, L.A. and Dayton, P.K. (2009). Ecological theory and continental margins: where shallow meets deep. Trends in Ecology and Evolution. 24: 606-627.

Miloslavich, P. and Klein, E. (2009). The world conference on marine biodiversity: Current global trends in marine biodiversity research. Marine Biodiversity. 39(2):147-152

Ramirez-Llodra, E., Tyler, P.A., Baker, M.C., Bergstad, O.A., Clark, M.R., Escobar, E., Levin, L.A., Menot, L., Rowden, A.A., Smith, C.R., Van Dover, C.L. (2011). Man and the Last Great Wilderness: Human Impact on the Deep Sea. PLoS ONE 6(8): e22588. DOI: 10.1371/journal.pone.0022588

Thuy, B., Kiel, S. Dulai, A., Gale, A.S., Kroh, A., Lord, A.R., Numberger-Thuy, L.D., Stöhr, S., Bisshack, M. (2014). First glimpse into Lower Jurassic deep-sea biodiversity: in situ diversification and resilience against extinction. Proceedings B of The Royal Society. DOI: 10.1098/rspb.2013.2624

What’s (not just) brown and sticky? Adaptive radiation in Stick and Leaf Insects in the order Phasmatodea.

The Indian or laboratory stick insect, *Carausius* *morosus*, a common pet.

The order Phasmatodea contains more than 3,000 extant species of insect found throughout the world, especially the warmer zones. These herbivorous (mostly arboreal) insects are most well-known for their crypsis, or camouflage, where their colour, shape and behaviour enable them to masquerade as twigs or leaves (hence their common names of stick and leaf insects).

Though there is still uncertainty about a definitive phylogeny, phasmids are considered one of 11 orthopteroid insect orders within the assemblage known as Polyneoptera. Phasmatodea are found alongside the modern orders: Blattodea (cockroaches), Dermaptera (earwigs), Embioptera (web-spinners), Grylloblattodea (ice crawlers), Mantodea (praying mantises), Mantophasmatodea (heel-walkers) and, of course, Orthoptera (crickets, grasshoppers, and katydids). According to phylogenomic analyses of nucleotide and amino acid sequences, some of these Polyneopteran lineages are thought to have emerged ~302 million years ago, with phasmids evolving after the Permian mass extinction.¹

Fossil Evidence

Fossil evidence of phasmids is, however, extremely rare. Specimens have been recovered in amber, most notably representatives of Euphasmatodea and Timematodea, with the oldest well-documented fossils being found in Cretaceous Burmese amber. Recent discoveries of the oldest-known fossilised leaf mimics (Phylliinae) from Messel, Germany in 2006 of Eophyllium messelensis date this foliacious mimicry to the Eocene.²

Although the fossil evidence is patchy, it is thought that traits relating to morphological plant masquerade within Phasmatodea first developed with stick mimicry in the Permian, followed by leaf mimesis developing in the Eocene when angiosperms largely replaced conifers as dominant trees.²

phasmid fossils — Simplified cladogram with a partial geochronologic scale showing the phylogenetic position of *E. messelensis* and the temporal sequence of character evolution. Insert; Photo (A) of holotype of fossil leaf insect *E. messelensis*, from the Eocene Messel Pit, Germany and Photo (B) *Cretophasmomina melanogramma* from 126 mya from the Yixian formation in Inner Mongolia [2, 3]

Fossils of Cretophasmomima melannogramma discovered in Yixian, China in 2006 from the Cretaceous Jehol biota (approximately 129 mya), however, provides evidence of phasmid crypsis relating to a Gingkophyte, Membranifolia admirabilis, which displayed leaf-shaped plant organs.³ It is therefore thought that leaf mimesis may well have developed far earlier than previously thought.

Crypsis, Camouflage, and Masquerade

In order to avoid visual detection by predatory mammals, birds, reptiles and other invertebrates, many insects evolved morphological characteristics that enabled them to blend in to their surrounding environment. Specifically in the case of phasmids, these evolutionary adaptations have been very closely linked to the insects’ host and food plants leading to a coupling of ecological and evolutionary dynamics.^4,5,6

Cryptic colouration, elongation of the body and legs, or, alternatively, broadening and flattening of the body to resemble leaves are all forms of masquerade adopted by phasmids to avoid detection by predators. This has led some researchers to conclude that predation may be an important driver of speciation in this order. Successful adaptation, through camouflage, may therefore lead to divergence in adaptive radiation. ^4,5,6

The basal-most extant recorded clade of Phasmatodea is the sub-order Timematodea, within which is found the genus Timema whose species are found throughout southwestern North America on a variety of host-plant species.⁷Experimental studies have been conducted into the influence of ecological factors with regards adaptive radiation in Timema cristinae with particular emphasis on host plants and cryptic colouration.^4,5,6,7

Timema cristinae, endemic to California has repeatedly evolved ecotypes adapted to different host plant species. One phenotype has no stripe and feeds on Ceanothus (left).

One ecotype features a distinct white stripe on its back and feeds on the thin, needle-like leaves of a shrub called Adenastoma.

cladogram — Above: *Timema cristinae*, endemic to California has repeatedly evolved ecotypes adapted to different host plant species. One ecotype features a distinct white stripe (right photo) on its back and feeds on the thin, needle-like leaves of a shrub called *Adenastoma*. The other phenotype has no stripe and feeds on *Ceanothus* (left). Below: Phylogeny of *Timema* species.

It was found that two distinct T. cristinae morphs had developed on two morphologically dissimilar plant species distributed in parapatric mosaics. The first plant, Adenostoma fasciculatum, has needle-like leaves, while the other, Caenothos spinosus, has broad, ovate leaves. Each T. cristinae morph (or ecotype) was found to be more cryptic on one of the two plant species depending on whether they displayed a heritable white dorsal stripe or not. One of the experiments found that bird predation significantly lowered numbers of T. cristinae that were maladapted to the host plant.⁴ Further studies concluded that through predator pressure, partial (but incomplete) ecological speciation has occurred in T. cristinae as the morphs still successfully interbred.^5,6,7

This partial speciation may, however, form only one dimension of selective pressures that constitute adaptive radiation events. It was also shown that by comparing different Timema species that share the same host plant, that sexual isolation was not as marked as with between species on different plants (when compared with T. podura and T. chumash)⁷ lending credence to the notion of ecological speciation. It is therefore apparent that predators apply selective pressure leading to morphological crypsis and divergence, but that this does not necessarily directly lead to speciation, but is more likely an intermediate stage in adaptive radiation.

Flying, Jumping, and Holding Still

In the case of the Phasmatodea, it has been discovered that diversification occurred in a wingless state and that wings were subsequently derived on a number of occasions.

Of the 3,000 species of phasmids, only 40% are fully winged, while the remainder are partially winged or entirely wingless. While being fully winged conveys advantages of dispersal, escape and finding resources, it has been claimed that increased female fecundity and crypsis may have served as a selective advantage in early phasmid evolution in a shift to winglessness. Apart from flight, wings and partial wings can also be used in threat or startle responses to deter would-be predators. By examining DNA sequence data and applying parsimony optimisation it was found that the ancestral condition of Phasmatodea is wingless.⁸

It was also found that certain phasmid lineages had “re-evolved” wings prompting suggestions that this reacquisition may confer adaptive advantages of being both winged and wingless as conditions necessitate over ecological time leading to further speciation.⁸

phylogeny

Timema chumash is unusual in phasmids in that it has been found to jump away from potential threats. Although it can only jump relatively short distances by extending the hind tibia, it can reach take-off velocities comparable to some larger European flea beetles. The leg positions and hind-leg length of T. chumash contrast with the morphology of other stick insects; its legs emerge ventrally from the thorax and its hind legs are proportionately longer than those of other phasmids. As T. chumash is wingless, it jumping is suggestive that it would enable a rapid fall from the plant it was perching on taking it out of the visual field of predators and providing it with another opportunity to camouflage itself nearby.⁹ These morphological and behavioural traits may present opportunities for further adaptive evolution.

crypsis

A well-documented behaviour in many phasmids is that of catalepsy whereby the insect is able to remain motionless or produce extremely slow movement as a form of twig or leaf mimesis to aid with predator evasion. The mechanism by which this is achieved, is via the high gain of the femur-tibia joint control system,¹⁰ and has been recorded in fossil specimens.² A key difference between phasmids and other orthopteroids is this significant coevolution of the mimetic body shape with catalepsy.¹⁰

Parthenogenesis, Hybridogenesis and Androgenesis

Phasmids experience a wide array of reproductive modes with about 10% of the phasmid taxa being parthenogenetic and producing all-female offspring (thelytoky).¹¹Although parthenogenesis reduces genetic variability, it does not wholly suppress it. Furthermore autopolyploids and allopolyploids can take advantage of higher mutational rates to increase heterozygosity. Androgenesis is also common and has been proposed as a likely pathway to cladogenesis in the genus Clonopsis¹¹ and has already been recorded in Pijnackeria where tetraploid hybrids lacking maternal genes, but keeping the maternal mitochondrial DNA, speciated.¹² The discovery of interracial and interspecific hybridogenesis in the genus Bacillus added further weight to the notion of maintaining (or even increasing) genetic diversity within phasmid lineages and creating opportunities for further speciation. ¹²

No one reproductive mechanism is exclusively used, so that complete reversion from thelytoky to amphimixis is possible. These “tangled interactions” allow for genetic diversity to persist within and between populations. When considered as part of a series of repeated and complex reproductive strategies including sexual reproduction, parthenogenesis, androgenesis and hybridogenesis, it must be concluded that evolutionary pathways for phasmids are far from dead-ends.^{11, 12}

Following divergence from other orthopteroids, phasmids took advantage of the new food sources and flourished following the angiosperm revolution and have continued to adapt in relation to predatory pressures, host-plant availability, behaviours, and complex reproductive strategies. Clearly, apart from the opportunities presented in the Eocene for cladogenesis and speciation, there continues to be further evolutionary opportunities relating specifically to morphology and sexual isolation in adaptive radiation of phasmids.

Black beauty stick insect shutterstock_51123130-1 — The Black Beauty stick insect, *Peruphasma schultei*, is known to exist only in a tiny area of 5ha (12 acres) in the Cordillera del Condor region of northern Peru, at altitudes between 1200-1800m.

References:

^1.Misof, B. et al. (2014), Phylogenomics resolves the timing and pattern of insect evolution. Science. 346 (610), 763-767.

^2. Wedmann, S., Bradler, S., and Rust, J. (2006), The first fossil leaf insect: 47 million years of specialized cryptic morphology and behavior. Proceedings of the National Academy of Sciences. 104 (2), 565-569.

^3.Wang, M., Be´thou, O., Bradler, S., Jacques, FMB., Cui, Y., and Ren, D. (2014), Under Cover at Pre-Angiosperm Times: A Cloaked Phasmatodean Insect from the Early Cretaceous Jehol Biota. PLoS One, 9 (3), e91290

^4. Farkas, TE., Mononen, T., Comeault, AA., Hanski, I. and Nosil, P. (2013) Evolution of Camouflage Drives Rapid Ecological Change in an Insect Community. Current Biology. 23, 1835-1843.

^5. Nosil, P., Crespi, BJ., and Sandoval, CP. (2002) Host-plant adaptation drives the parallel evolution of reproductive isolation. Nature. 417, 440-443.

^6. Nosil, P. and Crespi, BJ. (2006) Experimental evidence that predation promotes divergence in adaptive radiation. Proceedings of the National Academy of Sciences. 103 (24), 9090-9095.

^7. Nosil, P. and Sandoval, CP. (2008) Ecological Niche Dimensionality and the Evolutionary Diversification of Stick Insects. PLoS One. 3(4), e1907

^8. Whiting, MF., Bradler, S. and Maxwell, T. (2003) Loss and recovery of wings in stick insects. Nature. 421, 264-267.

^9. Burrows, M. (2008) Jumping in a wingless stick insect, Timema chumash (Phasmatodea, Timematodea, Timematidae). The Journal of Experimental Biology. 211, 1021-1028.

^10. Wolf, H., Bässler, U., Spieß, R. and Kittman, R. (2001) The femur–tibia control system in a proscopiid (Caelifera, Orthoptera): a test for assumptions on the functional basis and evolution of twig mimesis in stick insects. The Journal of Experimental Biology. 204, 3815-3822.

^11.Scali, V. (2009) Stick insects: parthenogenesis, polyploidy and beyond. In: Life and Time: The Evolution of Life and its History. Cleup, Padova. 171-192

Mosquito extinction. Is it really a good thing?

A few years ago I read an op-ed piece in the journal Nature that celebrated the potential demise of mosquitoes as scientists prepared to release genetically modified mosquitoes in Brazil in an attempt to eradicate populations carrying malaria. What most struck me about the piece was that the author concluded that mosquitoes performed no ecological function and that the world would be a better place without these pestiferous nuisances. This statement left me feeling a little uneasy. How certain could we actually be that mosquitoes performed absolutely no ecological function?

“Eradicating any organism would have serious consequences for ecosystems — wouldn’t it? Not when it comes to mosquitoes…”

In 2014 I listened to a podcast produced by Radiolab that reiterated the pointlessness of mosquitoes and again I wondered whether this could really hold entirely true. Apart from David Quammen’s valiant effort to convince us of the mosquito’s general innocence (it is after all only the females that bite, and even this is only in order to produce young). He also asks us to imagine just how quickly deforestation and exploitation of the tropics would have progressed without the relative protection afforded by the mosquito and all of it’s diseases.

According to the World Health Organisation (WHO) 17% of the global estimate of all infectious diseases are vector-borne. Of these, mosquito-borne diseases constitute the majority, with malaria causing an estimated 627,000 deaths in 2012 and infecting 1.5 to 2.7 million people a year. Some of the other mosquito-borne diseases that affect humans are Dengue fever, West Nile virus, Yellow fever, Lymphatic filariasis, Japanese encephalitis, Rift Valley fever, and Chikungunya; causing death, suffering and both social and economic hardship.

There are approximately 3,500 named mosquito species in the world. They are found in a variety of habitats in every biogeographic region apart from the Antarctic. Of these, only 40 Anopheles species are known to be effective transmitters of human malarial infection and only around 350 species are regarded as effective in all mosquito-borne human disease transmission. The catholic nature of mosquitoes in relation to habitat selectivity is best illustrated in the breadth of the geographic area covered by dominant malarial Anopheles mosquitoes. Mosquitoes are highly speciose, with the greatest species diversity being found in the Neotropical regions as shown in the map below.

This preponderance of mosquitoes to cause such human hardship has led to a variety of campaigns designed to control and eradicate them; from the use of DDT in the 1940s to attempts to sterilise males through exposure to radiation. Though there has been some success with these methods in the past, elimination of mosquitoes in the tropics has always proven difficult due to mosquito resistance, pathogen resistance to treatments, the lack of infrastructure and financial support. Conventional means of avoiding infection from mosquito-borne diseases have been to prevent being bitten through the use of mosquito nets and chemical repellents. I was therefore rather intrigued to hear about the work of Oxitec, the Alphey Lab and others in relation to developing genetic controls to exterminate this “winged scourge”.

The ecological niche filled by mosquitoes is little understood and has been poorly studied. In 2010, at the British Ecological Society’s annual meeting, the chair, Professor Charles Godfray said:

“We know very little about the [mosquito] community ecology… and this is significant because if you were to knock it out then you want to know what would take its place. […] And we don’t know enough, not for the want of trying, about the dispersal of the mosquitoes; how they move from one place to another.”

I simply couldn’t believe that such a large knowledge-gap existed with regards such an ubiquitous insect, so I decided to survey the scientific literature to figure out what is currently understood to be the ecological function performed by mosquitoes. I found that a very small number of papers actually concerned themselves with this topic directly and those that did were generally in relation to highly specific niches like larval processing of detritus chain interactions within pitcher-plants, the pollination of orchids, or focused on other species entirely, such as reindeer and caribou whose migration behaviour is influenced by the predation of mosquitoes and other biting flies. Understandably, most papers concentrated on the mosquito as disease vector – especially in relation to humans – but, apart from noting that mosquitoes constitute an enormous biomass, are found in both freshwater and terrestrial ecosystems at different life stages, and that they are highly speciose; there has been little scientific research into their ecological significance. We can extrapolate that they must be an important food source for a number of other insects, birds, reptiles, fish, amphibians and even mammals, but the data is lacking to support this – we need more research to be conducted to be certain. There is also a possibility that mosquitoes contribute to a disease dilution effect, but further study would be required to support any such claim.

So, is it a good idea to locally exterminate mosquitoes if we really don’t have any idea what will happen to their ecosystems? I would suggest that it probably isn’t the greatest idea. Possible scenarios are a reduction in available food for predators that will cause greater predation on other food sources thereby decreasing these at a faster rate and increasing competition. Increased competition can in turn lead to lower reproductive success and in the worst-case scenarios population collapse of apex predators. At least, I think it would be safe to assume that those ecosystems would no longer operate in the same way – their species composition would shift to a greater or lesser degree and with that the functional ecology.

And what about the disease dilution effect? Well, if it holds true in the case of mosquitoes then we may witness an intensification of disease virulence and higher infection rates. An alternative hypothesis is that the pathogens might move into other host species and we would be left scrabbling for new control mechanisms.

As someone with a desire to understand the intricately interlinked nature of our world and all the living creatures in it, I couldn’t support the deliberate extinction of any species (despite the detrimental effects it can have on humanity) without first knowing what the knock-on effects of that extinction would be. In doing something that we hope would benefit humanity, we may in fact be creating new and more complex problems.

An American entomologist, Jeremy Lockwood, wrote of the need to establish an ethical basis of “philosophically sound, scientifically consistent” considerations with regards our relationship to insects. He proposed that we refrain from taking actions that would kill or cause nontrivial pain to insects, but not if by avoiding those actions there would be nontrivial costs to human welfare. Genetically modified mosquitoes, and by association other mosquito control mechanisms, would presumably be considered acceptable to most people within this anthropocentric ethical framework. The irony of this position however is, as Lockwood points out, that a person considered a humanitarian is often referred to as, “one who wouldn’t hurt a fly”.

This blogpost is based on my final-year research paper. For those of you wanting a bit more in-depth information, you can read the full paper here.

References:

Alphey, L. (2014). Genetic Control of Mosquitoes. Annual Review of Entomology, 59(1), 205–224. doi:10.1146/annurev-ento-011613-162002

Fang, J. (2010) Ecology: A world without mosquitoes. Nature News, 466(7305), 432–434. doi:10.1038/466432a

Godfray, H. C. J. (2013). Mosquito ecology and control of malaria. Journal of Animal Ecology, 82(1), 15–25. doi:10.1111/1365-2656.12003

Lockwood, J. A. (1987). The Moral Standing of Insects and the Ethics of Extinction. Florida Entomologist, 70(1), 70 – 89.

Sinka et al. (2012). A global map of dominant malaria vectors. Parasites & Vectors, 5(69). doi:10.1186/1756-3305-5-69

World Health Organisation http://www.who.int/whr/1996/media_centre/executive_summary1/en/index9.html.

Hawk moths and evolutionary predictions

tumblr_nyja9lfDoo1qbsotxo1_1280 — A selection of Sphingidae moths photographed from the collection at London’s Natural History Museum.

Commonly known as Hawk Moths, Sphinx Moths and Hornworms, these moths are important pollinators of orchids and other flowers.

Nectar tubes and hawk moth tongue lengths are often associated; Xanthopan morganii praedicta (centre) was famously predicted to exist by Charles Darwin and Alfred Russel Wallace based on the length of the nectar spur of the Madagascan Christmas star orchid (Angraecum sesquipedale). Note the length of the moth’s uncoiled proboscis in the photo above.

In a letter to Joseph Hooker in 1862, Darwin wrote:

“I have just received such a Box full […] with the astounding Angraecum sesquipedalia [sic] with a nectary a foot long. Good Heavens what insect can suck it.”

KPPCONT_047171 — A hand-coloured lithograph of *Angraceum sesquipedale* by W.H. Fitch (1859) taken from *Curtis’s Botanical Magazine.*

A few days later, Darwin wrote a second letter in which he postulated that this insect must be a moth, and in 1867 Wallace published an article in which he supported Darwin’s suggestion, remarking that the African hawkmoth Xanthopan morganii (then known as Macrosila morganii) had a proboscis almost long enough to reach the bottom of the spur. In a footnote to this article Wallace wrote:

“That such a moth exists in Madagascar may be safely predicted; and naturalists who visit that island should search for it with as much confidence as astronomers searched for the planet Neptune,–and they will be equally successful!”

In 1903 (41 years after Darwin’s observation) this moth was discovered and named by Rothschild & Jordan after Wallace’s prediction that the moth would in fact be a hawkmoth. However, it was not before 1997 that it was finally confirmed that the Madagascan Christmas star orchid is actually pollinated by Xanthopan morganii praedicta.

Further reading:
Darwin and Wallace’s Predictions Come True

Angraecum sesquipedale

Miller, W. E. (1997) ‘Diversity and evolution of tongue lengths in Hawkmoths (Sphingidae)’. Journal of the Lepidopterists’ Society. 51(1), 9-31

Wasserthal, L. T. (1997) ‘The pollinators of the Malagasy star orchids Angraecum sesquipedale, A. sororium and A. compactum and the evolution of extremely long spurs by pollinator shift’. Bot. Acta 110: 343-359

Author: Gino Brignoli

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