On Tuesday night, I headed down to the beautiful Bell House, in the Gowanus section of Brooklyn, for this month's Secret Science Club lecture, featuring Dr Jessica Ware, entomologist and evolutionary biologist at Rutgers University, who earlier this year received the Presidential Early Career Award for Scientists and Engineers. The official title of Dr Ware's presentation was 'Insect Divergence: The Evolution of Termite, Dragonflies, and Damselflies.
Dr Ware began her lecture with an autobiographical note, joking that she and her twin sister, a performance artist, diverged early on. Her interest in science was sparked by her grandparents, residents of Northern Ontario, who 'tossed snakes and frogs' at their granddaughters. As a child, she engaged in the activities she now performs as a field biologist: hiking, collecting, asking questions, and indulging her natural curiosity. She decided to study insects because of sheer numbers... she can catch ten dragonflies in a shorter period of time than it would take to see one whale.
Dr Ware noted that there are approximately 5,500 mammal species on Earth, about 391,000 plant species, and approximately one million insect species. Insects are incredibly diverse- they run the gamut from herbivores to predators. Dr Ware said that, whatever humans have done, insects have done it before them. Insects wage war, take slaves, farm, and developed flight. One of Dr Ware's areas of research is determining how the various insect orders are related, and when they diversified. She is specifically interested in termites (which she described as 'fancy social cockroaches') and the dragonflies and their sister group the damselflies. She contrasted the key innovations of the termites (being sociality) and the dragon-and-damselflies (flight).
Before tackling insect diversity, Dr Ware gave us an overview of systematics, describing the 'family trees' of Earth's organisms. Using a familiar example, she noted that cats and dogs form a sister group while sheep are more distantly related. Dr Ware is a member of 1KITE, the One Thousand Insect Transcriptome Evolution project, which studies insect phylogenetics, how the different insect orders are related, and when they diversified.
The Odonata are basal insects, they are probably the earliest winged insects to evolve. There are approximately three thousand dragonfly species and about three thousand damselfly species... there is also an intermediate group, the Anisozygoptera, represented by a single genus found in Nepal, China, and Japan.
Dr Ware described the Odonata as pretty and showy, and have been used as decorative motifs by Tiffany and other designers. She launched into a very funny tangent, "Is your tattoo a dragonfly or an ant lion?" She conceded that the Neuroptera are also cool before noting that dragonflies have no antennae while ant lions have big antennae. She then joked that nobody has a tattoo of an aquatic dragonfly baby unless they are a top level entomologist. She noted that the aquatic dragonfly nymphs are voracious predators.
Dr Ware posed the question, who flew first? Was it the Odonata, the mayflies, or another insect lineage? What was flying around in the early days of insect evolution? What were the reasons why dragonflies evolved flight early on? Perhaps it was due to sexual selection- dragonfly mating involves indirect sperm transfer. Females mate with multiple males, and the males have a secondary 'penis'- they scrape the sperm of other males out of the female with which they are mating and use a 'secondary penis' in which sperm is stored to transfer the sperm after rivals' sperm is scraped out. Other basal insects use sperm packets to inseminate their mates.
Most Odonata systematics, Dr Ware explained, is based on wing venation- the degree of venation in an insect's wing (sparse vs high) is strongly correlated with flight syles, with the amout of veins determining the stiffness of a wing.
In the Carboniferous period, about 350 million years ago, a sister group to the Odonata, colloquially know as griffinflies, attained giant sizes, with wingspans up to two feet (Dr Ware quipped that, as a Canadian and a scientist, converting from metric units didn't come naturally to her). True Odonata appeared in the Permian, about 250 million years ago. The earliest branching lineage of the extant Odonata is the critically endangered Tasmanian damselfly Hemiphlebia mirabilis. Dr Ware somberly noted, "They may be extinct by the time you get home." The females use their abdomens to fling eggs haphazardly across the bogs which form their dwindling habitat. DNA sequencing revealed that they are a sister group to all other Odonata.
Dr Ware paused to inform us that she prefers dragonflies to damselflies before continuing with the lecture. She then went on to note that most of the organisms which prey on Odonata evolved after the Odonata did- frogs evolved in the Jurassic period, modern birds evolved in the Cretaceous period. She took a moment to joke: "Predators are jerks!"
Odonata have two egg-laying strategies: exophytic species lay their eggs outside of plants while endophytic species lay their eggs inside plants. Dr Ware amusingly described exophytic species as 'squirting their eggs out like ketchup', noting that they sometimes lay their eggs on cars, mistaking their reflective surfaces for bodies of water. The endophytic strategy may have been ancestral- in a case of convergent evolution, the Gomphidae (clubtails) and Libellulidae (skimmers) employ an exophytic strategy. They are not very closely related, so 'egg squirting' evolved twice, probably as a means to avoid predators.
Despite her preference for dragonflies, Dr Ware singled out a specific damselfly species for special consideration- the giant helicopter damselfly (Megaloprepus caerulatus) has evolved to eat spiders, plucking them right out of their webs. Some of the males have white, waxy patches on their wings, which are probably used in territorial displays to warn other males away from the water-filled tree holes which are necessary for mating. There is a geographical distribution between white patch dominant and no patch dominant populations.
Getting the coolest damselfly out of the way, Dr Ware then proceeded to her preferred Odonata, the dragonflies. The Aeshnidae (darners) are represented by 453 species of large, colorful dragonflies. Some of them can change color as the temperature changes, with pigment particles migrating to and from the surface of the abdomen, changing from blue to purple. Some of the darners are migratory- in one experiment, researchers glued tiny radio transmitters to the dragonflies with eyelash adhesive, but the transmitters interfered with the insects' flight, and most of the overburdened insects were eaten by predators.
The next family of dragonflies introduced by Dr Ware were the Petaluridae (petaltails), which are large dragonflies. Dr Ware then recounted the bizarre tale of one Perry Turner (PDF link), a student at Berkeley University who had borrowed a large collection of Petaluridae from various museums, including several type specimens. Turner was also a big believer in Sasquatch, and believed that Sasquatch ate Petaluridae. Turner disappeared without paying the rent on a storage locker, and his purloined Petaluridae ended up in an antiques shop.
Dr Ware then returned to the GomphidaeGomphidae (clubtails). which are exophytic egg-layers, their eggs being coated and weighted to they sink quickly to reduce predation by fish. There are over 900 species in the Gomphidae.
The Libellulidae (skimmers) are exophytic egg layers and some of the species are migratory. Dr Ware singled out the genus Pantala, which includes two species- Pantala hymenaea is a migratory species which ranges throughout the New World, and Pantala flavescens, which has a global (excepting Antarctica) distribution. Dr Ware joked that Pantala flavescens was her first dragonfly catch in Canada, Africa, and Australia. Pantala can thrive in areas which aren't hospitable to other dragonflies because their nymphs can develop in five weeks, which means that they can survive in temporary or transient bodies of water. Most dragonfly nymphs take one to five years to develop. Pantala also has a morphology conducive to gliding, with banded wing bases which can catch the wind. Pantala flavescens can be found also exhibits adaptive behaviors on windy islands, such as Easter Island, 'crouching' to avoid high winds so they aren't blown out to sea.
Dr Ware described a project in which the genomes of 700 Pantala flavescens specimens were sequenced to find shared genetic patterns, and to note where genetic outliers were found. A colleague of hers collected a Pantala flavescens while on a cruise, another colleague encountered a Pantala flavescens while on conducting research 100 miles out to sea. The origin of a particular Pantala flavescens can be determined through isotope analysis- since the nymphs develop in the water, they pick up the isotopes found in their native waters, which gets deposited in their wing chitin. Pantala flavescens in the Andes tended to have a local origin, while Pantala flavescens populations in Queensland and West Africa tended to have hydrogen signatures indicating that they originated elsewhere.
Dr Ware then shifted the focus of her lecture to termites (which I doubt anybody has a tattoo of). She described termites as fancy, myopic, dark-dwelling social roaches. They were formerly classified in their own order, the Isoptera, but they have recently been reclassified as Blattodea, along with the cockroaches. There are are approximately 4,500 species of roach and 3,100 species of termites. Most termite species are not pests, nor are all termites wood eaters- many termites consume fungi or grasses. Termite sociality probably evolved because termites need symbiotic bacteria to help them digest cellulose. These gut bacteria are lost as individual termites molt, and must be replenished by termites consuming probiotic anal secretions from other termites. Most termite studies involve the approximately 2% of termite species which are pests, though Dr Ware singled out termites which explode to defend their nest (if my beery brain recalls correctly, she recounted the discovery with a colleague, of an Amitermes species that "explodes like Mr Creosote" to defend the colony).
Dr Ware indicated that termite evolution is probably tied to the evolution of the flowering plants, the angiosperms, in the Cretaceous period. Determining the age at which insect lineages evolved can be complicated by flaws in molecular data and the difficulty of non-paleontologists in calibrating the age of fossils. It's generally believed that the first insects may have evolved around 450 million years ago, with roaches evolving around 250 million years ago. Piecing together the divergence of insect life does involve some cautious optimism.
Dr Ware ended her talk by discussing the future of entomology, stressing the need for public outreach, especially the need to get children involved. She discussed the role that her two children play in her fieldwork, displaying a picture with the funny caption: "Relax, my mom is an entomologist!" She talked about her early career, when women were often derided as 'net-holders', and said that she was the only woman in her entomological group in 2003. She disavowed the notion that women had to choose between fieldwork and child-rearing, noting that children are extremely good at collecting insects. She finished her lecture by stating the New Jersey has a particularly rich and diverse Odonata population, with 188 species inhabiting the Garden State.
The lecture was followed by a Q&A session. The first question involved dragonfly mortality- while predators take their toll on dragonflies, there are other dangers... dragonflies store fat in their tails, and there is a danger that they might run out of energy reserves. Another danger is that their wings get to wet to sustain lift, so they might drown. Mating is dangerous for dragonflies, the males have claspers on their tails with which they grasp females (or, by mistake, other males). The claspers can hurt the other dragonflies, and mating can be a violent affair. Dragonflies also eat other dragonflies. Another question involved polluted waters- dragonflies can sequester pollutants such as mercury and other heavy metals. The relative hardiness of dragonfly nymphs can be used to determine water quality. Another question involved dragonfly hunting strategies- dragonflies have spines on their tibia with which they catch prey on the wing (this is commonly known as 'hawking'), much of their food can be likened to 'aerial plankton'.
Some Bastard in the audience asked about the evolution of aquatic development in the Odonata. Aquatic development has evolved in numerous insect lineages, but the ancestral condition was terrestrial. Griffinfly nymphs are unknown, and there are some Odonata nymphs which aren't aquatic, with some species even found in trees.
A question involving the diet of early fliers elicited a grimly funny response from Dr Ware... "They probably ate each other." High atmospheric oxygen content allowed some griffinflies to reach their huge size. During the Jurassic period, an adaptation allowing twisting and bending of the wings evolved, which resulted in improved flight. During the Jurassic, though, there were more predators. Regarding Pantela flavescens, the species is a young one, perhaps a million years old, and small nucleotide differences among populations suggest numerous repeated colonization events on islands.
Regarding climate change, temperature in lab settings does effect viability, with many species operating optimally at a temperature of 25C. At 30C, mortality sets in, with temperature particularly effecting the behavior of aquatic juveniles.
Dr Ware was asked about the possibility of an impending Insect Apocalypse- yearly collections are used to determine biomass. There has been no difference in dragonfly biomass, but there is a difference in species distribution. Dragonflies are highly mobile, they can leave areas when conditions change for the worse. In one particular case, a dragonfly formerly limited in northerly range to North Africa can now be found in Sweden, and Arctic dragonflies now range above the treeline.
Another attendee asked about dragonfly longevity- the adults last for one hot summer, they have two to three months to 'get their business done'. Nymphs can range in lifespan from five weeks to five years, depending on the species.
Regarding the skinny abdomens of damselflies, Dr Ware noted that all damselflies are endophytic, and narrow abdomens are probably a result of this egg-laying strategy. Dragonflies, being more active, have invested more resources in a muscular thorax and a fat-storing abdomen. The need for heat dispersal might also affect abdomen size. Another question involved edibility- there are no venomous or poisonous dragonflies, and the thorax, being muscle, is pure protein.
There was a question regarding fear of insects. Dr Ware stated that it is learned behavior- her older child accompanied her in the lab much of the time, and has no fear of insects. Her younger child spent time in daycare with entomophobes while she was working on her doctorate, and is less comfortable with insects. She quipped that this was only a sample size of two.
Regarding aggregating behavior, aggregations occur around suitable mating sites, and sites where food is plentiful. Exophytic dragonflies produce large egg masses, which is good for the first nymphs to hatch, because they can eat their smaller siblings.
The final question of the night involved the exploding termites, about which not a lot is known. Dr Ware was collecting termites with a colleague using aspirators. While collecting termites from a strange-looking mound, they noticed that the aspirator was getting clogged with 'gooey' termites. Closer observation revealed that some of the termites had ruptured abdomens, but they noted that this might have been a result of collection methods. They didn't think it was enough to change the focus of their research, so they put the specimens in ethanol, and brought them back to New Jersey. They noted the explosions, which probably evolved to seal colony walls, later.
There's a concept which I call the 'Secret Science Sweet Spot', that particular combination of hard science fact, entertainment factor, and advocacy. I'm an entomophile, as longtime readers will know, and this has been a BIG BUG SUMMER for me, so this was a paricularly fantastic lecture. Dr Ware knocked it out of the park, with fascinating information, gorgeous photographs, engaging autobiography, and earnest advocacy for education, inclusion, and environmentalism. I only had one beef with her... I am firmly on team damselfly (I mean, I've never had a dragonfly interact with me like this), and jocularly chided her for her damselfly deprecation. All was well when she revealed her first Odonata tattoo, a male ebony jewelwing like the one that so patiently allowed me to relocate- she didn't want to subject the tattoo artist to having to depict wing venation, so she chose the Odonate with opaque wings. All is forgiven, good doctor! There were some other highlights- one of Dr Ware's old mentors brought a bunch of live insects to the beautiful Bell House, including Madagascar hissing roaches, a leaf-mimicking mantis, and a grasshopper-ish critter that was about four inches long. Also in attendance was entomophagy advocate chef Joseph Yoon. NJIT sent a contingent, notably Dr Phil Barden, who indicated that having a damselfly land on your fishing pole is good luck.
Kudos to Dr Ware, Margaret (who has pulling solo duty as Dorian was out of town being awesome elsewhere), and the staff of the beautiful Bell House. While I enjoy all of the lectures, I have to confess my bio-bias, and this month's lecture was TOP TIER. High fives all around! Here's a video of Dr Ware leading some students in fieldwork in a park in Newark, New Jersey:
Pour yourself a nice beverage and soak in that SCIENCE!
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment