Dispersal & Reid’s Paradox

The distribution of organisms in the environment is a particularly interesting subject.  We know that individual  representatives of the different kingdoms have specific requirements for establishment and growth.  We know this at an almost intuitive level and we apply this knowledge daily when we amend soils for our gardens, move houseplants into or out of the sun, and make sure our pets are fed and watered.  If we need more tomato plants, we go to the store and buy young ones or seeds and plant them, likewise we buy puppies, kittens, or fish for our homes, taking them with us when we move from place to place.  We rarely ask the question of how living creatures move about in the absence of humans.  How they disperse.

Fleabane species – note the dandelion-like seed heads

This is a problem all living things face, and they all solve it in slightly different ways.  Obviously, for mobile creatures, birds, reptiles, fish, mammals, insects, and all their cousins, this can be handled in a relatively straightforward fashion by simply getting up and going somewhere else.  Clearly there are particular variations on the theme.  Red Efts in New England are born in the water, stay there for a time, move onto land as non-breeding adolescents, then return to the water as breeding adults.  The majority of them don’t travel far, but a few adults find themselves in a different body of water than they started in, thus slowly expanding the range of the species.  Yes, legs are helpful.

Red Eft (Notophthalmus viridescens) in its adolescent dispersal stage

In earlier posts I have mentioned how some insects spend most of their life hidden from us, entering their highly visible state only to breed and find new territories.

It has long been recognized that our understanding of how plants, fungus, and all the traditionally non-mobile creatures disperse is poorly understood and very, very important.  In 1899 Clement Reid introduced what is now known as Reid’s Paradox in his marvelous book, The Origin of the British Flora.  Reid’s Paradox is more formally known as “Reid’s Paradox of Rapid Plant Migration”, an unwieldy, if accurate title.  Simply put, the paradox is that every measurement we take of plant seed dispersal indicates that range expansions and colonization of new areas should take place extremely slowly, but everywhere we look plants have colonized new areas far, far faster than all predictions indicate is possible.  By orders of magnitude in some cases.

Reid recognized this problem when trying to calculate how long it would take oak trees to colonize Britain once the glaciers left.  There was a tremendous mismatch in where oaks were and where they should have been.  In modern times this mismatch has been expanded to a wide variety of other species and, despite advances in dispersal calculations, we don’t really have a good answer for it even now.  We lump it under the heading “long distance dispersal” and leave it at that.  I will return to this.

With fungus the dispersal question is a bit easier to understand.

Reishi (Ganoderma lucidum) fruiting bodies on a Hemlock tree

Two fungi of the same species meet and produce mushrooms (the sexual reproductive organ), scattering billions of spores smaller than dust particles that drift on the wind or in the water.  Except that fungi are really strange and ancient and have developed some special techniques for dispersal (EDIT:  Slime Molds have been removed from the fungal kingdom.  Now they are considered to be a polyphyletic group of protists representing convergent evolution from several origins.  A large branch of the slime mold group is closely related to amoeba).

Setting aside mobile slime-molds as a special case, the solution to dispersal that fungus use is one of numbers, astounding numbers, unbelievable numbers.  Only a very small portion of the released spores will disperse any great distance and an even smaller portion of the spores will germinate, but when you are dealing in the tens of billions even a small percentage can be a large number.

This, with some variation is the same answer to dispersal plants use, it’s a numbers game.  If a tree has a seed producing lifespan of 90 years and produces thousands of seeds each year and only 99.9% of the seeds never travel more than 100 feet from the tree that’s ok.  If the tree is living there, conditions are likely good, so it makes sense for most of the seeds to stay near home.  That 0.1%, well, who knows what odd event will carry the seed beyond that 100 foot (or whatever is is for that species) radius?  Storms and animals are common agents of long distance dispersal, as are humans now.

Plants are crafty though, they weigh the odds.  They may time the release of seeds to favorable environmental conditions.

Hop Hornbeam (Ostrya virginiana) seeds in their hollow sheaths

Hop Hornbeam (Ostrya virginiana) produces a dangling cluster of separate seeds, each individually packaged in its own balloon-like capsule.  Over time these seeds break loose and fall to the ground, similar to how grass seeds break from the rachis and fall to the ground when disturbed.  These seeds fall during winter, landing on the snow and blowing across the landscape, coming to rest in small hollows that also trap water and nutritious debris during spring melt.  Birch trees use this technique as well, blowing across the snow like grains of sand in a storm, as, to a lesser degree, does American Basswood (Tilia americana).

American Basswood (Tilia americana) seeds on snow

Another crafty plant technique to aid in dispersal is to hijack animals.  This is not much of a stretch for them, they already hijack animals for reproduction via pollination, but the ingenuity and range of techniques by which plants co-opt animals is truly astounding.  It is the kind of thing that really should, if you think about it, make you question who or what is actually in charge.

Phoresy is when one organism uses another to disperse.  Hitching rides on animals is a common version of phoresy plants employ.  It  is an extremely selfish and cheap way for plants to hijack animal legs or wings.  Seeds may have hooks, barbs, or be sticky, and the animals get no reward for helping the plant.  If plant times this right it may latch onto a migrating animal that may carry the seed hundreds or even thousands of miles.

A more targeted technique is to bribe the animal.

Lowbush Blueberries and Rock Polypody fern

Fruits (like the blueberry in the background of the image above) are sacrificial bribes for animals, like free drinks at a casino.  Often the fruits are targeted to specific animals or classes of animals.  The colors and smells let birds and beasts know when the fruit is safe to eat (meaning, when the seeds will survive a passage through the animal’s digestive system).  Just as with flowers, specific colors and odors are targeted at specific animals or suites of animals.  Certain plants have been very successful in hijacking humans for their purposes.

Also, notice the developing spores on the fern frond.

In some cases the plant simply sacrifices a portion of the seeds themselves so that a few may survive.  Oaks are a classic example of this.  Woodpeckers, blue-jays, chipmunks, and squirrels will cache acorns in a variety of places like leprechauns with pots of gold.  Some of these caches will be forgotten and will sprout.  This is why, in some areas, you may find 3 or 4 oak trees growing from a rock-pile all joined at the base.  Most likely they were separate seeds in a single food cache.  Again, oaks games the system by slowly dropping seed production year after year, then mast fruiting, producing an overabundance of food, far more than the now decreased animal population can possibly eat.

Wind and water are effective distributors as well, maples, coconuts, dandelions, and mangroves all use one or another of these techniques.  In most cases seeds don’t travel far, but in rare occurrences wind or water will carry seeds tremendous distances, and all it takes is that one or two times.

Right now the question of long distance dispersal and Reid’s Paradox is experiencing a revival in light of climate change.  Tree species in New England are moving north rapidly, and whole populations of plants and animals are moving away from the equator rapidly as well.  Others are climbing up or down mountains depending on whether temperature or moisture is the limiting factor.  If we want to know what the future holds we need to understand these action better than we currently do.

This hardly does justice to the complexity of methods and techniques used for dispersal, but it opens the door.

Canada Geese and goslings

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Balsas on the Rio Alto Madidi in Bolivia

I have wanderlust.  Intense wanderlust; the kind of wanderlust that makes your teeth hurt, your hands itch, and your mind always turn to the new, the unknown.

I don’t often get to indulge in my wanderlust, so when I do I try to make it count.  Back in 2005 I quit the very nice job I had as the cellar-master of a lovely little California winery and left for South America, all in all spending about a year working on various ecology related projects and traveling.  It was amazing and, despite the troubles that emerged from it, eminently worth the experience for far too many reasons to enumerate.

One of the key drivers of my wanderlust is the desire to learn new things and encounter new challenges, and in Bolivia I got to learn some extremely interesting things about a plant I only knew a little about before.

Balsa (Ochroma pyramidale).  We in the northern hemisphere know it mainly from toy airplanes, model making, and sometimes from lightweight packing crates.  I suspect that a number of people reading this blog will have read about Thor Heyerdahl’s incredible 1947 Kon Tiki expedition where he and 5 companions spent 101 days traveling 4300 miles across the Pacific on a raft made from Balsa logs based on ancient Peruvian raft designs.  If you have not read this book, go out and get it immediately, also look for the movie he made while on the raft which is also incredible.  I digress, the point being that most of us know Balsa as a lightweight wood used for novelty items.

In South America it is used for far more than novelty items.  River rafts being key amongst the numerous uses of this amazing plant.

Our supply raft, Rafael and Franklin piloting it down the Río Madidi

Balsa is a short-lived, small to midsized tree that grows rapidly, reaching not much more than 90 feet tall in 10-15 years and dying within 50 years.  Balsa is in the Malvaceae family, a group of  intensely useful plants that included cocoa, hibiscus, durian, jute, okra, bass wood, and a number of ornamental plants.  In the Amazonian lowlands, where the rivers often over-run their banks Balsa trees often line the rivers in thicket-like stands along with Caña Brava (Gynerium sagittatum), a tall reed that looks like a fan-topped cross of Arundo donax and bamboo.

Balsa Colorado (red balsa) and Caña Brava lining a riverbank

The seeds develop in rugby ball shaped pods that break open to reveal thousands of tiny fluffy seeds that trickle out and drift away on the wind, or drop on the water to float down river.  They come to rest in the sticky mud of the river banks, then sprout and grow rapidly, trying to reproduce before the next flood that scours the landscape clean.

Balsa seeds are light, drifting on the wind and floating on the water

My first introduction to the diversity of uses Balsa can be put to was when I embarked on a 20 day trip into the Madidi National Park in northern Bolivia at the eastern foothills of the Andes.  To go in as deeply as I and my 2 traveling companions wanted to involved a guide, 3 porters/navigators, and a 2 day motorboat ride up the Río Tuichi where we were dropped off on the river bank followed by the boat turning and leaving us.

Welcome to the jungle – yes, that is an enormous catfish on the rock next to the river, caught with a machete

Our local guides and porters did not have backpacks, only synthetic canvass sacks filled with food and cooking gear, lacking shoulder straps.  The first 4 or so days of our trip involved long hikes, clearly there needed to be a better way of carrying these sacks than slung over one’s shoulder like Santa Claus.  Near where we were dropped off were some young Balsa trees, about the diameter of a broomstick, maybe larger.  The bark was peeled off and stripped down to the cambium layer, resulting in a long, translucent ribbon of surprisingly tough fiber which was, with the addition of several pebbles, swiftly put into use as shoulder straps for the carry bags.  This material was so tough that it did not need to be replaced for the extent of the trip.

After quite a bit of hiking, some interesting encounters, and a few adrenaline filled moments we crossed over a line of low mountains and followed the stream down the other side to a point where we could no-longer wade across.  We were on the Alto Río Madidi and we needed boats to continue.  There were trees and we had machetes.

Tío (we all called him “uncle”) peeling bark from a Balsa tree

We camped for several days felling 15 or so young Balsa trees with trunks about the diameter of your thigh, cut some short acacia rods, some Caña Brava, and made rope from the cambium of sapling Balsa trees.  When we were done we had two fine river craft, one for two people and everyone’s luggage, another for myself, my two traveling companions, our guide, and one of the porter/navigators.

Two rafts made with machetes from Balsa logs. A mooring rope of Balsa cambium is coiled on the foremost raft

For the remaining 16 days of our trip these rafts served us well, riding through flash floods, over rapids, banging into submerged logs and steep banks, with minimal problems, keeping us dry and stable the whole time.  When they needed repairs all we had to do was collect material from the riparian vegetation and we were back in business.

Balsa leaves are large and soft.  Many insects eat the leaves as there is little, if any, toxin in them, the tree spending its energy on growth rather than protection.  I have seen entire trees completely denuded of leaves within a day by leaf cutter ants.  We used the leaves as well.  The make adequate toilet paper (the lack of toxin being especially important in that instance), for cooking, and for carrying food.  We cut bamboo, filled the culms with freshly caught fish, packed Balsa leaves in the open top to prevent steam from escaping and placed the fish packed bamboo next to the fire to cook.  We carried lunches of roasted fish cooked the night before wrapped in Balsa leaves, and would pick them to use as seat covers on muddy ground.

Lunch carried wrapped up in Balsa leaves

The word balsa, means raft and the ones we made were proof that the tree is well named.

Me running rapids on the Alto Madidi with Tío in front and our guide, Pedro MasCuapa in the rear

A side note, the area we went into is sparsely traveled; the year I went in our group was the only one that had gone so far in and only 3 or 4 other groups had gone into the park more than a day’s hike that year.  If tourism were to increase in the area, a different raft solution would have to be sought.

These photos were taken with a Canon AE-1 with a 50mm 1.8 lens.  All the film was developed and scanned in South America and the picture quality reflects the abuse I put the camera through and the questionable film developing of the places I went to.

The final photo of me was taken by one of my traveling companions.

Club-Mosses on the mountain

A few days ago I had the opportunity to be a guest speaker on an alpine botany field trip for a class a friend of mine is teaching.  The highest and largest alpine environment in Vermont is atop Mt. Mansfield, two hundred acres of exposed rock, lichens, and a delicate assortment of tiny plants bordered by dense krummholz forest housing several rare bird species.

Mt Mansfield ridge trail

This areas is one of only three tiny regions of Vermont where alpine tundra environments exist, and part of a very small handful of places on the East Coast.  These places are relicts from the end of the last ice age, extremely sensitive to changes in temperature and moisture, home to plants that are usually found much further north.  The growing season is short, nutrients are in short supply, and wind stresses are high, all of which result in slow growing, long lived plants that do not colonize open areas well.  Visitors are encouraged to walk only on the rocky areas, keeping off of the easily damaged vegetation.

I had been eager to visit the peak of Mt. Mansfield for some time because it is one of the only places in Vermont that a certain small clubmoss lives.  I mentioned this to the botany students and during a rest break one of them got my attention and asked if the little plant he was pointing to was the one I had mentioned.

Appalachian Fir-Clubmoss (Huperzia appalachiana)

It was one of the smallest examples of Appalachian Fir-Clubmoss (Huperzia appalachiana) that I had seen anywhere, but it was indeed the plant I was looking for.

Clubmosses are really cool and predate flowering plants by an embarrassingly large span of time.  They are not really moss of any type, though they bear a superficial resemblance to the true mosses.  Mosses themselves are not true plants, having no vascular tissue, the plant equivalent of our circulatory system.  Mosses rely on diffusion to distribute water and nutrients and this imposes strict limits on their size.  Clubmosses are more akin to ferns and conifers: they have simple hair-like roots (true mosses have no roots), they have vascular tissue, and, at one point in the extremely distant past (300+ million years ago), their close cousins were the dominant large vegetation reaching one hundred feet above the ground.  Now most clubmosses are small, only a few inches tall, although in the Amazon I did encounter one waist high clubmoss near an overgrown pond.

Unknown Peruvian clubmoss. It grew to just above my waist.

I was interested in the Appalachian Fir-Clubmoss, Huperzia appalachiana, because several years ago I spent a summer in Shenandoah National Park, Virginia, climbing about on steep cliffs looking for this plant and trying to figure out how to measure any change populations might experience as the climate changes.  It likes acidic, well drained soils over igneous (or highly metamorphic) bedrock that receive frequent moisture, and, unusual for a clubmoss, direct sunlight.  It hybridizes easily with several other clubmosses, Shining Clubmoss (Huperzia lucidula), Northern Fir-Clubmoss (Huperzia selago), and Huperzia appressa, which some people do not distinguish from Huperzia appalachiana, making the identification question particularly vexing where the ranges overlap.

The Huperzia genus was recently split from the Lycopodium genus, which is where many of the more familiar clubmosses reside.  Like many of the Huperzia, the Appalachian Fir-Clubmoss grows from a dense basal cluster and, unlike many of the Lycopodium, it does not creep about over the ground.

Huperzia appalachiana – note the bands of white spore capsules

No-one is certain how long Appalachian Fir-Clubmoss lives.  The best answer I could get from a sharp fellow at Miami University in Ohio was, “At least seventeen years.”  Not a very satisfying answer, and he knew it.

One way to estimate the age is to count the bands of spore capsules on the stalk, those little white bits that looks like tiny eggs or pale ticks in the image above.  Each band correlates to roughly one year of growth.  Unfortunately, no-one knows how old the plant has to be before it starts producing those, and they don’t always produce them each year.  With some Huperzia species you can count the rings of gemmae, odd little cup-shaped brackets the plant produces that contain a tiny asexually produced plant that is dropped onto the ground in place of a spore when conditions are good.  The gemmae look very different from the microphylls, which is what clubmoss leaves are called.

Huperzia appalachiana
The gemmae are the little 3-part flanges near the top of the plant – further down the empty brackets are visible

Another way to judge the age is to count the bands of vegetation where the microphylls are pressed up close to the stem and where they spread out.  Each spreading ring indicates spring growth.

All that is good in theory, unfortunately Appalachian Fir-Clubmoss produces gemmae in a haphazard fashion and, unlike the photo above, often does not have those nice alternating bands of growth.  Hence the, “At least seventeen years,” answer to my question.

Clubmosses grow in a variety of forms and have been used for some rather unlikely purposes in the past.  The spores they produce are tiny and highly flammable, so much so that they were used as flash powder in old time photography.  Condoms were dusted with clubmoss spores to keep the rubber from sticking to itself, and diapers are sometimes dusted with the spores to prevent rashes.  Today, we mainly use living clubmosses in garlands and ancient clubmosses in our coal burning power-plants.

One of the great things about living in New England is the wonderful variety of local clubmosses.  They are delightfully archaic.  Deceptively so, considering that they have been living for well over 300 million years and are still common in many places world-wide.

Tree Ground-Pine (Lycopodium dendroideum)

Rock Harlequin – what is a fire adapted species doing in Vermont?

A few days ago I bumped into a plant I rarely see in Vermont.  It goes by a number of names, The USDA plant database lists it as Rock Harlequin, various other sources call it Tall, Pink, or Pale Corydalis, and the scientific community has settled on Corydalis sempervirens, although it used to be called Capnoides sempervirens.  Rock Harlequin ranges from Alaska to the northern Pacific Northwest, across Canada, and down most of the East Coast.

I don’t see Rock Harlequin in Vermont very often, so it’s a bit exciting when I do find it.   Here it grows on well drained, dry, rocky, south or west facing slopes, often in the company of Shad Bush, Red Maple, Hop Hornbeam, and/or Red, White, and Chestnut Oak.  It is a pretty little plant with yellow-tipped pink flowers of a peculiar shape and long, green bean-like seed pods.

Corydalis sempervirens with aphids and spiders

The Corydalis genus is wide spread, with most of its members living in China.  It is in the poppy family (Papaveraceae) via the intermediary of the bleeding heart sub-family (Fumariaceae).  When I first saw this plant I was really confused.  I grew up in California where the California Poppy and the Pacific Bleeding Heart are common.  The Rock Harlequin looked like some strange cross between these plants, with oddly asymmetrical flowers.  I wasn’t sure exactly what to make of it.

The other branch of the Fumariaceae is the Dicentra genus, most commonly represented in Vermont by Squirrel Corn and Dutchman’s Breeches.  These plants have extremely symmetrical flowers.

Dutchman’s Breeches (Dicentra cucullaria)

The leaves are similar and, if you squint, you can see a bit of similarity between the flowers.  Dutchman’s Breeches tends to grow in rocky, but damp places, producing lush vegetation.  Like Dutchman’s Breeches the Rock Harlequin initially grows all it’s leaves from a basal rosette, but, unlike Dutchman’s Breeches, when it produces a flower stalk there are little leaflets on the stalk as well.

Rock Harlequin is spare, lean, and tough.  Its blue-tinged leaves have a leathery feel to them and the flower stalks are wiry, resistant to wind and sun.  It is a fire adapted species, which may be why it is unusual to find it in Vermont.  The land here is damp, like a sponge left in the sink, fires do not take easily and burns remain small when they do ignite.  The patch of flowers I found was growing directly from cracks in the exposed bedrock near small trees that had lived a hard life.  All the trees nearby were chest-height or shorter, broken by wind and ice, lightning struck, and starved of water and nutrients.  A perfect place for Ericaceae plants, the family that contains blueberries and huckleberries.

Rock Harlequin against dwarf blue-berries

Sure enough, the larger Rock Harlequin were growing right on the edge of patches of dwarf blueberries.  I tried to get a back-lit photo showing a little of the internal structure of the flower.  There is a darker line running through the pink of the flower body which terminates in a spiky yellow rosette.  The flower begins growing as a tiny yellow nub which expands, turning pink as it does so.  Once the flowers are pollinated, by wind and by ants (how cool is that, ant pollination), long bean-like seedpods grow, containing tough, easily germinated seeds.  The seeds need either heat or scarification to germinate, but have extremely high success rates.

In the past Native People managed the land with fire, burning frequently with small, low temperature fires that kept the forest understory clear and promoted the growth of a number of plants.  I can’t help but wonder if this plant was more common in the past.

Rock Harlequin with seed pods

The Mighty Dragonfly

Of all insects there are few that capture our attention and interest the way dragonflies do.  They have, perhaps, the coolest, most evocative name of any group of insects: Dragonfly.  In English there are a great number of other common categorical names: Devil’s Darning Needle, Snake Doctor, and Ear Cutter among others.  Many of these names come from the mystifying apparent fear of nature that crops up over and over in European views of the world.  Many European cultures viewed dragonflies as sinister creatures, servants of the devil, in league with other evils such as snakes and bats.

Other cultures, often more agrarian ones, had a far more benign view of dragonflies, based, perhaps, on the recognition of their fundamental role in controlling populations of pest insects of all sorts.  An archaic name for the Japanese Islands is Akitsushima (秋津島), the Dragonfly Islands, where dragonflies symbolized courage, strength, and happiness.  For some native American tribes dragonflies symbolized clean, pure water, swiftness, and agility.  In the modern world dragonflies are good indicators of environmental heath, indicating a robustly functioning ecosystem.

Libellula quadrimaculata – Four Spotted Skimmer
The Alaskan State Insect

Dragonflies and their close relatives, Damselflies, come in a dazzling array of colors and patterns, ranging in size from less than  an inch long up to the South American Megaloprepus caerulatus with a wingspan of over 7 inches.  The largest dragonfly we know of is from the 300 million year old fossil Meganeura that had a wingspan of over 2 feet.

Dragonflies are powerful hunters, both in their nymph and adult stages.  Dragonfly nymphs are aquatic and prey on any animal or insect they can grab with their claws or their extendible jaws.  Insects, small fish, tadpoles, and small amphibians are all food for these voracious predators.  The nymphs are large, and, in turn, are prey for a wide range of other animals, insects, birds, and fish.  Elva Paulson has some wonderful watercolors of a dragonfly emerging from its nymph stage.  Humans are included as predators, many Asian cultures eating both dragonfly nymphs and adult dragonflies as delicacies.  One of the most tasty things I’ve eaten (from a long list of foods most people would consider to be unusual) was a plate of deep fried dragonfly larvae.  Absolutely delicious.  In Beijing I would sometimes find adult dragonflies candied in liquid sugar, their wings crispy with the hardened sugar.

Unknown green dragonfly – note the barbs on the forelegs for catching prey

The adult phase of a dragonfly’s life is short, in temperate climates only the length of the summer.  This is their mating stage and it takes them between 2 months and 6 years living under water to reach this stage.  Dragonflies are extremely active during this mating phase and must eat often.  They have enormous eyes giving nearly 360 vision, incredibly swift reactions, fast, powerful flight, and wicked barbs on their legs to assist capturing insects in flight.  The inset above shows these barbs.

Libellula exusta – White Corporal (I think)
eating its prey

The common names of dragonflies often reflect their speed or their abilities as hunters.  Meadow-hawk is one of my favorite names, and watching one dart away to catch an insect and return to its roost to devour it definitely brings hawks to mind.

Libellula quadrimaculata – Four Spotted Skimmer
note the different wing heights

Dragonflies are powerful fliers.  They have been clocked at over 35 miles an hour, fast enough to get a speeding ticket in a school zone, and, like hummingbirds, can fly forwards, backwards, sideways, up and down, and hover.  Their backs are sloped where their wings anchor, placing each pair at different heights, allowing for tremendous wing mobility.  Some species of dragonfly migrate, but the scale of some of those migrations has only recently been realized.  One dragonfly species in particular, the Globe Skimmer (Pantala flavescens) flies from India to Africa and back, island hopping cross the Indian Ocean, making open water crossings of nearly 1000km (620 miles) between island stops.  The only places they can breed are at the Indian and African ends of the migration, many of the islands they use as stopover points do not have sufficient freshwater for dragonflies to breed.  This is a stunning feat of flying for an insect and may be a behavior that evolved as a result of plate tectonics splitting India and Africa apart, eventually thrusting India into Asia.  If so, this migration could have begun 135 millions years ago.  Unfortunately, we have no reliable way of telling if this is the case.

Last year was a good year for dragonflies in Vermont, and this year looks like it is shaping up to be a good one as well.  The ecologist in me cannot help wondering why and one idea is that it may be linked to the calamitous drop in bat populations as a result of white-nose disease, a fungus that infects hibernating bats, weakening and eventually killing them.  It may be that adult dragonflies have more to eat with fewer bats and a greater percentage of them are surviving through the summer.  There is a historical precedent for this sort of boom in insect populations.  During the Great Leap Forward, Chairman Mao promoted a policy of killing off all things he thought were eating grain, birds amongst these.  With the crash in bird populations in China the insect population exploded.

Unidentified dragonfly – maybe a Darner of some sort

I am happy to see the dragonflies here.  Their presence means that the water is clean, we will have fewer mosquitoes, midges, and black-flies, and they are extraordinarily beautiful creatures.

Three-hundred twenty-five millions years old and going strong.  They have it figured out!