Italian Wall Lizards and Rapid Evolution

The last few years have been busy but have brought with them an opportunity to travel and to learn about new places, but little time to write.  Each year I spend a bit of time in Europe and extend my work trips to include a bit of time off.  Usually these trips are centered on Germany but I try to visit a few more places and in 2015 I had the opportunity to spent a few weeks in northern and central Italy.

A number of things caught my attention, for example how Virginia Creeper (Parthenocissus quinquefolia) has become invasive in much of Europe but especially in northern Italy, how different the color pattern of the Hooded Crow (Corvus cornix) is to what I’m used to seeing in the Americas or Asia, the deep similarity of vegetation assemblages and species to those in North America occupying similar habitats, and, of course, the fantastic views and towns perched on hills or nestled into narrow canyons, like Riomaggiore.

Riomaggiore pan above 085-091 small.jpg

Riomaggiore, one of the Cinque Terre, in La Spezia

Of the things I saw in Italy there is one I’d like to focus on for this post.  It is a small, common lizard, often overlooked.

The Cinque Terre coast is very similar to parts of the California coastal chaparral and dry coastal forests, so it was no surprise to find lizards sunning themselves on the trails, hiding in the stone walls of the terraced vineyards, and rustling through the oak, laurel, and chestnut leaf duff layer.  Lizards are funny beasts, sometimes bold as you please standing on their rocks as though they own the world, other times bolting at the bend of a blade of grass.  Unfortunately, these lizards were wary and fled my approach, leaving me with only vague, scaly impressions of what they looked like.

It was in Florence where I finally saw one of the little fellows clearly.  I’d had enough of the noise and crowds and escaped to the Boboli Gardens, where I paid a bit more attention to the plants than I did to the impressive array of statuary.  Near a hedge a slight twitch amongst the dried leaves caught my eye and revealed itself to be a beautiful small green lizard with black and tan patterning sunning itself on a bed of withered sycamore leaves.  It was almost done shedding its skin and the colors were vivid.

Florence Italian Wall Lizard (Podarcis sicula) 112.jpg

Italian Wall Lizard (Podarcis sicula subsp. ?) in the Boboli Gardens, Florence

This is, of course, the Italian Wall Lizard (Podarcis sicula), a highly adaptable small lizard native to Italy and nearby regions.  This not an endangered or even rare species, on the contrary, it is quite common within its range, and its adaptability has led to the development of at least 62 recognized subspecies.  I did not know any of this when I first encountered the species, but something about it seemed familiar.  It wasn’t until I came across several more of them in Bracciano and had the time to identify them that the niggling sense of familiarity clicked.

In 1971 scientists transplanted 10 individuals of this species (5 breeding pairs) from the island of Pod Kopište to Pod Mrčaru, Croatia, a small island; only a few hundred meters long on its longest axis; with a resident population of a different lizard species, the Dalmatian Wall Lizard (Podarcis melisellensis) .  The goal of this experiment was to test competitive exclusion in island biogeography theory.

Pod Mrčaru map.jpg

Unfortunately the 1970s were a troubled time for that part of Europe and Yugoslavia began its fragmentation into what are now Slovenia, Croatia, Bosnia/Herzegovina, Serbia, Montenegro, Kosovo, and Macedonia.  Trouble mounted through the 1970s and in 1980 Josip Broz Tito died, opening up a power vacuum exacerbated by ongoing ethnic conflicts.  It wasn’t until the mid-1990s that the dust more-or-less settled.

The long lasting conflicts in the region put a halt to the experiments of Eviatar Nevo  and his team on  Pod Kopište and Pod Mrčaru.  The lizards, of course, were undisturbed by the commotion of the excitable bipeds and the tiny island was left undisturbed until about 2004 when tourism was allowed in the area. Researchers returned to the island shortly afterward.

To the researcher’s surprise, they found that the initial 10 introduced Italian Wall Lizards had increased to a population of over 5,000 and that the native Dalmatian Wall Lizard was now locally extinct.

Further investigation revealed the real shocker; in the brief time the island had been left alone, some 30 lizard generations (abut 36 years), the introduced Italian Wall Lizards lizards had undergone profound evolutionary changes.

This is what had been tickling the back of my mind when I saw that first lizard in the garden of Florence.  Long before my trip to Italy I had seen a documentary discussing the rapid and unexpected changes these lizards had undergone.  I must have remembered the morphology of the lizard, but had lost the connection of that particular lizard to the documentary.  I can’t find the original video I saw, but there is a Richard Dawkins video on the subject:

Italian Wall Lizards are primarily insectivores, but in their new habitat they changed to become primarily herbivores.  For a omnivore like us this doesn’t seem to be a startling thing, we regularly shift back and forth between different types of foods, sometimes craving meat, other times preferring vegetables and many people make long-term dietary commitments to avoiding animal products entirely while other cultures have traditionally had a diet consisting almost entirely of animal products.  We are large animals and have evolved to be generalist gourmands.

For the lizards this switch is not so simple.  Plant matter needs time to ferment and break down to make digestion possible.  Plant matter can be extremely tough, requiring more effort to consume.  The shift from eating insects to eating plants is akin to shifting from eating exclusively fast food to eating primarily home-cooked meals.  Before you just ate what you bought, but now you need a working kitchen and utensils for preparing and cooking the food.

The introduced lizards developed a host of traits to aid in the consumption of tough plant matter; cecal valves (muscles that separate the large and small intestine, slowing down food digestion and effectively creating fermentation chambers – a bit like ruminates with their multiple stomach compartments-, allowed them to process the tough plant cellulose), larger, stronger jaws and bigger muscles to assist in the harvesting plant matter, changes in head morphology, and an over-all larger body size.

These changes may not seem like much, but they’ve been likened to humans evolving a new appendix in only a few hundred years.

Interestingly, the changes in food supply also changed the social behavior of the Italian Wall Lizards, leading them to be less territorial.

Changes in general should not come as a surprise considering the variability of Podarcis sicula.  After all there are some 62 subspecies of this lizard.  Even the between the individuals I saw in Florence and Bracciano there appear to be differences in head shape, color, and patterning.

Wall Lizard comparison (Podarcis sicula) Bracciano 173 Florence 115 small.jpg

Comparison between Italian Wall Lizards (Podarcis sicula) in Florence and Bracciano

What is surprising is how rapidly major evolutionary changes took place.  We tend to view evolution as a gradual process taking place over millennia with changes taking place so gradually that they are almost unnoticeable in human relevant timescales.  We know this is not true, but this view is so prevalent that it forms the backbone for one of the common critiques of evolution by those so inclined. Here we have a lovely example of evolution in action on a human relevant timescale. Better yet, it is an unexpected change, one that could well lead to a new species developing, if given enough time.

This is the largest change seen in this species, but it is far from the only case.  Italian Wall Lizards have been introduced in Turkey, Spain, and the US.  One of their populations in the US in New York, where they were introduced in 1966 or ’67 (most likely via the pet trade) has revealed an interesting an unexpected adaptation.  In the home range of the Italian Wall Lizard the temperatures rarely drop below about -7C and do not remain cold for prolonged periods.  As a result the lizards are active throughout the year with only brief periods of inactivity.  In New York, however, temperatures can drop to -20C and remain below freezing for extended periods.  It turns out that these robust little reptiles have a hidden ability and can supercool themselves and hibernate through the colder months in New York, a behavior not seen in their native range.

Bracciano Italian Wall Lizard (Podarcis sicula) 174.jpg

Italian Wall Lizard (Podarcis sicula) in Bracciano outside the Italian Air Force Museum

It is easy to overlook the little things and to take the common things for granted, but it is often those very things that open our eyes and our minds to greater understanding of the world around us.

These humble little lizards provide a window into evolution and adaptability, a window that might never have been noticed if not for the happenstance of a lost experiment carried out decades prior.

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Tar Pits, Dung Beetles, and Megafauna

Today Los Angeles is a city with a reputation for excess, dominated by cars and actors, and there is a reason for this.  Money.  Money in the form of oil.  The combination of oil and money led to the nascent fossil fuel industry teaming up with the budding car industry in the early 20th century to sabotage the successful street and rail car industry in the Los Angeles basin.  Money led to loose laws which led to crime, gambling, and guerrilla movie studios moving into the LA area, searching for places that were outside the influence of the film establishment of the times.  All of these things are interesting, but without the oil it is unlikely Los Angeles would have taken the trajectory it did.

Oil Fields, Signal Hill, Los Angeles 1914

Oil Fields, Signal Hill, Los Angeles 1914 – source: National Geographic archives

Oil is usually found deep under ground, but the greater Los Angeles area up through the Santa Barbara area is one of a few places in the world where oil is not just close to the surface, it is on the surface, bubbling in cold pits of bitumen, also known as asphalt and tar.  This asphaltum has been important to humans for as long as they have lived in the region.  In the past it was primarily used to waterproof boats, water carriers, and cooking vessels or as an adhesive.  Now, of course we use it to make a whole range of products from gasoline to Vaseline, rubber, plastics, pantyhose, parachutes, paint, detergents, antifreeze, golf balls, and more.

Bitumen occurs where vast amounts of living material (plankton, diatoms, or plant material usually) were deposited in a quiet anaerobic environment, such as a lake or sea floor, and left alone for a long, long time.  In essence, it is liquid coal.  Coal beds are sometimes repositories for incredible collections of fossils.  These ancient remains and offer a window into the deep past, but for a window into the more recent past we need something a little different from coal.  Bitumen provides one of the best preserving agents for more recent remains.

Near Hollywood there is a famous bitumen pit redundantly named the La Brea Tar Pits (literally “The Tar Tar Pits”).  Between approximately 38,000 years ago and 11,000 years ago the La Brea Tar Pits were very active.  An enormous variety of animals and insects were lured to the waters of what appeared to be a rich wetland and were trapped by the sticky tar that lay beneath the shallow layer of water.  A few posts back I brought up the fact that condors are representatives of an extinct assemblage of fauna.  The La Brea tar Pits provide a window into that now extinct assemblage.  Los Angeles was a land of giant bears and jaguars, pygmy pronghorn antelope, camels, mammoths, dire-wolves, great birds of prey, giant ground sloths, and numerous other animals.  

Mural of the La Brea Tar Pits during the Quaternary

Mural of the La Brea Tar Pits during the Quaternary

Animals trapped by the sticky tar aroused the interest of predators and scavengers which were themselves trapped by the tar.  Herbivores, carnivores, mammals, birds, and insects all fell prey to the tar pits and many of them have been preserved in astoundingly good condition.

Pygmy Pronghorn (Capromeryx minor)

Pygmy Pronghorn (Capromeryx minor)

Along with the large animals is one of the best collections of preserved insects in the world.  Most people know that insects are important in a sort of general way.  In recent years honeybees have been in the news quite a bit and their importance in maintaining our food supply has reached the mainstream audience.  I’ve mentioned the importance of both ladybugs and dragonflies, but these are iconic and popular insects, very much in the public eye.  There are many other insects that have an importance far beyond what their diminutive size would indicate.  One of these is the dung beetle (Scarabaeinae).

Until recently much of the planet was home to a wide range of large animals, grouped into the catch-all term “megafauna”.  This is a generic term for any animal massing more than 45-100 kg (100-220lbs).  Most of the recent megafauna of each continent (with the exception of Africa) went extinct shortly after humans reached the respective region.  Here in North America we had great mammoths, elephant relatives, standing 4 meters (13 feet) tall at the shoulder and weighing 9 metric tons (10 short tons).  You can walk under the tusks of the mammoth skeleton in the La Brea Tar Pits, reach your hand up as high as you can, and the tusks are still out of reach.

Colombian Mammoth (Mammuthus columbi)

Colombian Mammoth (Mammuthus columbi)

Numerous types of ground sloth roamed the area, including both the Shasta and Harlan’s Sloths.  Harlan’s Ground Sloth was not the largest and even it stood 3 meters (10 feet) tall and weighed more than a ton.

Harlan's Ground Sloth (Paramylodon)

Harlan’s Ground Sloth (Paramylodon)

The Antique Bison, some 15-25% larger than modern bison roamed the region,

Antique Bison (Bison antiquus)

Antique Bison (Bison antiquus)

And there were, or course predators of all sorts.  Dire Wolves are particularly well represented in the La Brea Tar Pit fossils.

Dire Wolf (Canis dirus) skulls.  One panel of a 3-panel display.

Dire Wolf (Canis dirus) skulls. One panel of a 3-panel display.

There were large numbers of these animals and, like all animals, they had to eat.  The larger the animal, the more it eats.  Modern African elephants eat 100-300kg (220-660lbs) of food per day, so it is reasonable to expect that the Colombian mammoth would eat at least that much per day, if not more.  Then, just on the herbivore side of things, there were the giant ground sloths, horses, camelids, bison, elk, antelope, peccaries, deer, and numerous other species.  Additionally there all the predators; giant jaguars, sabre-toothed cats, dire wolves, American cheetahs, bears of all sorts, including the giant short-faced bear, and more besides them.

All animals must eat, and everything they eat must come out eventually.  This is something we don’t really think much about: what happens to all the animal dung?  How much of it was there?

We don’t really have any good idea just what the animal numbers were like in the past, but we do have a very good idea of the numbers of another kind of modern megafauna.  Cows.  The numbers of cows in the US probably only represent a middling-small portion of the total amount of large megafauna in the US portion of North America, but they give some insight into the kinds of numbers we are talking about when it comes to dung quantities.

The 2006 article by Losey and Vaughan provides some insight to those numbers.  Each cow can produce approximately 21 cubic meters of waste per year, that’s a volume roughly equivalent to 1.3 VW buses worth of dung per year per cow.  In 2004 there were nearly 100 million head of cattle in the US, that means more than 2 billion cubic meters of poop per year, just from cows… I’ll let that image settle in.  For comparison that’s enough to cover  Manhattan to a depth of about 70 feet (21 meters) or Disney World to about 60 feet (18 meters) in cow manure every year (in other news: Disney World is larger than Manhattan).  That’s just from the cows and just the ones in the US.

What happens to all that crap?  Enter the humble dung beetle.  For the portion of cattle that are fortunate enough to be in fields, dung beetles take care of the waste.  According to Losey and Vaughan each year dung beetles save ranchers $380 million dollars in clean-up costs.  A 2001 article by Michelle Thomas indicates that without dung beetles each year we would find 5-10% of each cattle acre unusable due to dung pile-up.  Dung beetles are so important that foreign species of dung beetles have been imported to the US and elsewhere for use in areas that experience heavy livestock use.

Dung beetles range in size from just a few millimeters to several inches in length.  Their size is dependent on the size of the dung they have to deal with.  Currently Africa has the largest land animals and the largest dung beetles.  North America used to have an enormous range of very large animals with correspondingly large droppings.  As you might expect there were some very large dung beetles living here to take care of those droppings.  The large beetle on the left is an extinct giant water beetle similar in size the the large, extinct dung beetles.   This beetle is about 2 inches (5 cm) long.

Different species of dung beetles found in the tar pits.  The large one is extinct.

Different species of small dung beetles found in the tar pits and an extinct giant water beetle that is about the size of the large extinct dung beetles.

Ecosystems are delicate things, subject to trophic cascades, as I have previously mentioned, full of unexpected consequences and side effects.  Most of the great predators in North America died out when the large herbivorous megafauna became extinct.  Scavengers also suffered, amongst them the dung beetles.  All the large dung beetles in North America swiftly followed the rest of the megafauna into extinction.  Currently in North America the dung beetles are small, more like the insects to the right in the image above than the large tan one (you can check out photos of them here).

For many people the response to this is a shrug of the shoulders, but the effects of these beetles going missing had a tremendous effect on the ecosystem, in particular on plant growth and distribution.  We don’t know, and probably will never know how great an effect their absence had.  Dung beetles, the Scarabaeinae, are extremely important ecosystem engineers, gathering fresh dung and burying it as a food source for their developing young.  By doing so they fertilize and aerate the soil, speeding up the cycle of nutrient return by putting the nutrients in a safe place where the plant roots can get to them and where they are less likely to be washed away by rain or desiccated by the sun and blown away.  In addition, dung beetles are important in limiting the spread of diseases and parasites by removing fly and pest breeding sites.

Understanding the details of the world, the interactions, the interconnectedness, the causality of it is difficult.  When we look at the present we have the fine resolution, but lack a context.  When we look at the past we establish a context, but lack the fine scale resolution.  When we look to the future, as we must, we need to be able to combine the insights of the past and the present to predict the consequences of our actions.

Hopefully we are getting better at this, but I cannot help but look at connections like that between the mammoth, dung beetle, the dire wolf, the distribution of plants, and the radiating effects of that interleaving and wonder what vital link, or set of links, we are failing to see right now and what what will mean for our future.

The Archives at the La Brea Tar Pits

Archives at the La Brea Tar Pits

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Apologies for the multiple posting.  I made an edit using the WordPress App on my iPad and it deleted the original post.  I had to restore it and repost.

Plant Defenses – myriad strategies

Plants, as you might imagine, devote a great deal of energy to defending themselves from predators.  We humans have a natural bias towards animals, creatures that are like us in that they are mobile and respond to stimulus on a timescale similar to ours.  Plants operate, with a few notable exceptions, on a slower timescale, but this in no way should be taken to imply that they are any less interactive vis-a-vis their surroundings.

Plants react to light and dark, sense gravity, moisture, nutrients, and toxins; some can “feel” other organisms (Venus fly traps for example) or “hear” sounds (sensitive plants).  One thing all organisms must cope with is predators and competitors, and all organisms need defenses against these threats.  Plants are no different in their needs, but they are largely immobile, so some of their defenses tend to take a different form than they do in animals.  Surprisingly, their defenses are not as different from animal defenses as one might expect.  I would break plant defenses into three broad categories: chemical, physical, and co-optive.

Chemical defenses often involve toxins of one sort or another or pungent aromas.  Some of these we assiduously avoid, such as certain members of the Sumac (Anacardiaceae) family like poison oak (Toxicodendron diversilobum) and poison ivy (Toxicodendron radicans) due to the allergen urushiol found in the sap.  Other plants using chemical defenses we consume with great relish, many of our foods and spices, for example, derive their strong flavors from the defenses the plant manufactures to deter herbivorous predators.  Mints (Lamiaceae), rosemary, cinnamon, peppers, and onions are good example of common foods we consume that utilize strong chemical defenses.  Other chemical defenses we find recreational and/or medical uses for; ephedrine from plants in the Ephedra family, THC from Cannibus, and cocaine refined from alkaloids found in the coca family (Erythroxylaceae) all have enormous economies reliant on them.

Coca cultivation in Bolivia near Coroico

Coca cultivation in Bolivia near Coroico

Chemical defenses are enormously interesting and extremely sophisticated, but they are largely hidden from us until we are affected by them.  This is part of the reason why eating unfamiliar plants is so dangerous, there are few good ways to determine if a plant is edible upon first encounter.

Physical defenses are the most obvious to us, especially when they come in the form of thorns and barbs, but those defenses barely scratch the surface of the types of physical defenses plants can employ.

An impressive but unsubtle defense - Ceiba speciosa in the Bolivian Amazon

An impressive but unsubtle defense – Ceiba speciosa in the Bolivian Amazon

Sharp pokey bits may defend plants against larger herbivores and chemicals help to protect them from insects or pathogens, but other plants themselves can be, if not predatory, at least detrimental to large trees.  Lianas and other climbing plants, epiphytes, parasitic plants, and even other large trees may need to be defended against.

Strangler fig (Ficus spp.) overwhelming a palm tree's defenses - Bolivia

Strangler fig (Ficus spp.) overwhelming a palm tree’s defenses – Bolivia

The photo above I find particular interesting as the palm tree being overwhelmed by the strangler fig usually has an effective counter to this sort of attack.  Palm trees and tree ferns both allow their old fronds to droop as they age, sheathing the trunk and providing a structure for climbing plants to adhere to.  Eventually these canny plants shed their dead fronds, and with them the uninvited plant guests that have taken up residence.  Many trees employ a similar strategy, eucalyptus and madrone have smooth bark that regularly sloughs off in strips.  The combination of smoothness and shedding makes it difficult for other plants to gain purchase.

Strangler fig is a generic term for a wide variety of tropical fig trees sharing a similar life strategy.  These are the “matapalo” or killer trees.  Rather than growing from the ground and climbing up these trees co-opt animals to carry their tiny seeds through the canopy.  A small portion of these seeds wind up in a place like the crotch of a branch or a broken limb where organic material has built up.  The young fig sends dangling roots down from the canopy in search of nutrients, eventually reaching the ground and transitioning from a vine-like life style to a more tree-like life style.  More and more ground-seeking tendrils make their way downwards, eventually ringing the host tree and strangling it.  As this happens the strangler fig uses the original host as a scaffold and sends its own canopy high enough to overshadow the unfortunate host.  The palm tree in the photo above was underneath a tree the strangler fig took root in and had the misfortune to be attacked from above rather than from below.

Color is an oft overlooked plant defense, the role of which is still being debated.  I don’t mean fruit color, that is blatant advertising and animal bribery.  The color and pattern of the leaves and trunk of plants may serve as defense against predators.

The most familiar example of this is variegation in leaves, that is the white or colored mottling seen most often in ornamental plants, but also occasionally found in the wild.

Variegated hibiscus leaf. Source

Color mottling in leaves is often a symptom of nutrient deficiency, insect predation, viral infection, or genetic chimerism (expression of more than one genetic sequence in a single organism).  In most of the above cases this indicates poor health in the plant, and a plant in poor health makes for an unappetizing meal.  Some plants seem to capitalize on this and mimic the effects of various types of poor health (eg. false leaf damage and variegation) to trick predators into avoiding what appears to a be an un-nutritious meal(1)(2).  Bark color, whether natural or as a result of mutualistic lichen growth may be a predator deterrent as well, as lighter colors may make predators more visible to other predators higher up on the food chain.

Before moving on to animal co-option I should mention one other strategy employed by some plants.  Outgrow your predators.  In this case a plant allocates few resources to defense and focuses on growth and/or reproduction.  Balsa trees follow this strategy, they grow astoundingly rapidly and produce copious numbers of seeds.  They are not long lived and have few toxins, as a result they are subject to immense amounts of predation from a wide range of species.  Some of these, such as tapirs, they avoid by growing out of their reach.  Others are more problematic.  I saw a 30 foot tall young balsa tree completely stripped of leaves by leaf cutter ants in less than two days.

Basla saplings - Bolivia

Basla saplings – Bolivia

The most interesting of the plant defenses, to my mind, is animal co-option for defense.  Ants are probably the animal most often co-opted by plants.  We don’t often think of plants as being the ones to manipulate animals, but that is more a reflection of our animal bias than of the true nature of things.  Plants are highly manipulative, in their slow manner.  Like many effective manipulators, they accomplish their ends via bribes (and in a few cases by outright lies – orchids tricking bees into trying to mate with the flowers is a classic example of vegetative duplicity).  Ants are employed as guards by a great number of plant species.

When I first arrived in the Amazon I recall thinking to myself, “Cool, I hope I get to see some of the ant/plant mutualism.”  The first plant I looked at closely was a common understory shrub in the widespread and diverse Melastomataceae family.

Melastomataceae with ant sheltering nodes at the base of the leaves - Peru

Melastomataceae with ant sheltering nodes at the base of the leaves – Peru

At the base of each leaf there was a hollow, swollen node with two small openings on the underside.  Tiny ants occupied these nodes and would rush out to defend the plant when it was bumped.  This is a surprisingly effective defense against herbivores of all sorts, insect and mammalian.  All through the Amazon (and elsewhere in the world) ants and plants have banded together.  I found arboreal ferns with hollow rootballs harboring and colonies, tall cecropia and smoke trees (“palo diablo” – devil trees) with hollow trunks harboring vast numbers of fierce and painful fire ants, and evocative single species plant stands called Chullachaqui gardens.

According to legend the Chullachaqui is a forest guardian spirit that keeps small monoculture garden plots scattered here and there in the forest.  One should be wary entering these areas, ask permission first, and be careful not to damage any of the plants the Chullachaqui grows.  This is good advice as the Chullachaqui gardens are home to a species of ant that lives underground and kills all the plants growing on the surface except for one species.  Animals that interlope are attacked also attacked and the bite and sting of the ant is painful as it contains formic acid.

One of the neatest ant-plant interactions comes in the form of hanging “ant gardens”.

Ant garden in Peru with Monstera spp.

Ant garden in Peru with Monstera spp.

The dense cluster of plants in the above photo is growing from an arboreal ant hive.  Certain plants produce seeds with fatty nodules on them that ants eat.  Ants collect the seeds and store them in their hives, clipping the edible portions off as needed.  Some of the sees sprout and send their roots into the rich material of the ant hive, reinforcing it and protecting it from rain and predators as they grow.  These hanging ant gardens are found throughout the tropics.

Ant-plant interactions are not limited to the tropics.  Some trillium species bribe ants with food to carry their seeds to good growing locations and elderberries in certain portions of North America keep a protective coterie of ants nearby by bribing them with sugar produces from nectaries grown specifically for the ants.

Co-opting an animal may well be the most sophisticated of plant strategies for its subtly, specificity, and efficiency.  Energy cost is at the root of all these strategies.  A plant only has as much energy as it can collect from the sun and soil nutrients.  It must balance its energy use amongst growth, reproduction, and defense.  Every defense a plant employs lessens the amount of energy it can devote to growth and reproduction.  Combining forces with other species can provide a relatively low-cost way for a plant to gain an aggressive, mobile, multi-pronged defense force.  Ants, for example defend their plant hosts with both physically damaging attacks and with chemicals.  That’s a two-for-one defense with an added bonus of rapid deployment for the relatively minimal investment of a home or some food.

Humans may well be mammal plants have trained best.

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A note about the images and film vs digital in the field:

These photos (with the exception of the hibiscus leaf which is not mine) were taken in 2005 with a well used and abused Canon AE1 with a 50mm 1.4 lens and scanned from the negatives by the developing kiosks in Peru and Bolivia.  The quality of images reflects both the environmental stresses put on the camera and film and the irregular scanning quality.

For long periods of time in the field I still think that film is the better option.  I was in the jungle for months at a time, sometimes in places with no power (20+ days hiking and on a raft in Bolivia for example) and in hot, humid conditions with frequent thundering downpours and rampant mildew growth.  I love the digital camera I use now, but it would have been completely unusable for the majority of the time I spent in South America.

Film cameras do still have their place.

Chert – the birthstone of our species

Few types of stone have as long lasting and intimate relationship with our species as do those of the chert family.  Humans have been using this hard, glassy stone continuously to make tools since the time of Homo habilis, some 1.5-2 million years ago.  Our neolithic ancestors mined chert using fire to crack the stone (see video to see how it was done), at least 33,000 years ago at the Nazlet Khater site in Egypt chert was extracted from subterranean mines,  and flint (a type of chert) was used before we had matches to make fire, today we use crushed chert as the abrasive on some sandpapers, and to extract exquisitely detailed micro-fossils from the distant past.  When I worked as an archaeologist near Santa Barbara most of the projectile points, stone awls, and cutting tools we found were made from chert.

What is this “chert” we have been using so assiduously for the last 2 million years?

Chert is a microcrystalline stone made of silicon dioxide (SiO2) with a cryptocrystalline structure (crystals so fine that they are difficult to see even under a microscope) that lacks cleavage planes.  One of the most useful, for us, aspects of cryptocrystalline materials such as chert is that when they are struck they shatter in a predictable conical manner (conchoidal fracturing).  Obsidian and plate glass share this characteristic, making them and chert excellent for making extremely sharp stone tools.  Chert is more common than obsidian, but still rare enough that it was traded over great distances.  Another beneficial aspect of chert is that it is extremely hard, raking a 7 on the Mohs scale.

A number of well known minerals fall into the chert category: flint, jasper, radiolarite, chalcedony, agate,  and onyx are all types of chert, each with specific characteristics that give them enough difference from each other to warrant specific names.  The famous (and expensive) sharpening stones from Arkansas are made from novaculite, a porous, metamorphosed chert that makes an excellent abrasive.  Flints tend to be high quality cherts that are found specifically in chalk or limestone; these are deposited diagenically (via silicon replacement).  Chalcedony, agate, and onyx are a nested subset of minerals with chalcedony, a fibrous form of chert, being the parent of the group.  Jasper is usually found in association with volcanic activity and is sometimes considered to be under the chalcedony subset.  Jasper, agate, and onyx are popular semi-precious stones used for jewelry and sometimes intricately carved.

Red jasper cameo of Medusa by Benedetto Pistrucci (source)

What got me started thinking about cherts once more was a short day-hike I took with a friend in the Marin Headlands, those steep sided hills to the north of San Francisco that are so often obscured by the thick maritime fog.

Marin Headlands and the Golden Gate bridge partially hidden by fog

Marin Headlands and the Golden Gate bridge partially hidden by fog

The Northern California coast has a complex geology and is undergoing a number of divergent changes simultaneously.  This is an emergent shoreline (Geology of Northern California chapter 10, page 37), a place where the land is slowly rising in elevation.  Rising lands often suffer from high rates of erosion and the California coast has an even more drastic set of factors contributing to the erosion rare than merely rising land.  The bedrock is fractured by many faults, weakening the stone, earthquakes (most extremely minor) shake rubble loose periodically, and both wind and water eat away at the ocean facing slopes.  In addition, the sea level has risen several hundred feet since the last glaciation twelve thousand years ago, and the surf is greedily pounding on the hills, tearing parts of them away.

If you watched the video you probably noticed that the chert they were mining peeled off in plates, indeed that the whole formation was made up of sheets of stone layered atop each other like pastry dough.  About 50% of rock in the Marin Headlands is chert and has a similar texture.

Radiolarin ribbon chert cliff showing soft folds and a sharp fault-line cut

Radiolarite chert cliff showing soft folds and a sharp fault-line cut

This is ribbon chert, more formally known as radiolarite chert.  It gets the latter name because it is a biogenic stone made from the semi-gelled skeletons of radiolaria, a type of plankton that builds a silica based support structure.  These this rock was laid down over a 100 million year span beginning 200 million years ago and is filled with tiny fossils of the radiolaria.  Supposedly some of these are large enough to see with a standard hand-lens.

The folding tells us something interesting.  The folds in the above photo are smooth, meaning that this probably slumped slowly while it was still ductile.  Portions of the cliff have sharp folds where the rock broke, indicating that those deformations most likely happened more rapidly and after the stone had lost much of its ductility.

Red and greenish/blue indicate iron, either in oxodised or reduced form

Red and greenish/blue indicate iron, either in oxidised or reduced form

Much of the chert here is red, but there are many patches of vibrant blue-green and aqua as well.  The colors in chert indicate trace amounts of other minerals.  The red and the lovely greenish-blue are both indicators of iron, the red indicating that the iron has oxidised, the blue-green that it has been reduced (had the oxygen removed from it).  This is similar to the mottled gleying that one sees in wetland clay soils.  I am particularly fond of the blue and green colors in chert, perhaps because they are a bit more rare than the red.

Close-up of blue/green chert bands

Close-up of blue/green chert bands

The hardness of the chert leads to beaches with an interesting texture of sand, more like tiny glossy pebbles than the standard sand.

Chert sand

Chert sand

The combination of colors on the cliffs, beach, sky, and ocean make for a nice combination as well.

Tennessee Valley beach in the Marin Headlands

Tennessee Valley beach in the Marin Headlands

We have been using chert for nearly as long as we have been using tools, close to 2 million years now with no sign of slowing down.  If our species had a birthstone it would probably be chert.

Things that Gall – plants and parasites

The word “galling” is particularly evocative.  In its most simple form something that galls is merely annoying or vexing, but the true definition connotes annoyance taken to an extreme level.  The sort of thing that will do you no harm but rankles tremendously; much like being forced to pay taxes to support actions you object to.

For us these annoyances are mental and emotional, for plants these galls are physical but are often merely annoyances for them as well.

Dried oak apple gall  on Scrub oak in California

Dried oak apple gall on Scrub oak in California

Many plants suffer from galls and the galls are so singular in form that they can be reliably used to identify individual parasite species.  A fantastic book on identifying plant galls for the California region is the Field Guide to Plant Galls of California and Other Western States.

Oak trees seem to be particularly susceptible to parasites of all sorts and a common manifestation is the Oak Apple Gall, most often seen as a hard, woody ball dangling from a twig.  These galls are created by the Oak Apple Gall Wasp, a common name for a variety of small wasps that inject their eggs into the midrib of a developing leaf and chemically trick the tree into growing a protective shell for the developing larvae.  Despite appearing woody when dried, this type of gall is actually a modified leaf.  The delicacy of these galls is more easily seen when they are still green.

Fresh Oak Apple Gall - Virginia

Fresh Oak Apple Gall – Virginia

The developing wasps browse on the oak tissue and are often preyed upon or parasitized by other animals, including birds, raccoons, and a whole host of insects, other wasps included.  Some insects use the gall for their own protection, sharing the space with the wasp larvae.

Oak Apple Gall with non-wasp larva inside next to a Twig Gall - California

Oak Apple Gall with non-wasp larva inside next to a Twig Gall – California

Certain Oak Apple Galls, the Iron Galls,  in Europe were collected to make ink.  For 1500 years ink make from the iron gall was the primary source of writing quality ink in the Western Hemisphere.  For anyone interested Evan Lindquest provides detailed instructions on how to make your own iron gall ink.

Like may things we have a long history with there is a great body of mythology and folk-lore that has accumulated around these galls.

Many galls are hard and woody, there is a Twig Gall I sliced in half in the photo above.  It appears to be empty, but a dark brown patch filled with frass (insect excrement) can be seen winding its way though the bloated tissue.

Oak Apple Galls often fall from the tree, but Twig Galls are a more permanent fixture of the tree.

Twig Gall on a scrub oak branch flowering from the tip - California

Twig Gall on a scrub oak branch flowering from the tip – California

Right now the Scrub Oak is blooming along the coastal mountains in Southern California.  The twig galls are uniformly clustered near the tips of the branches, with many of them crowned by small clusters of flowers.  This provides a bit of insight into the formation of these and other galls.

The gall must be grown, and while the living plant cells are constantly dividing, the true growth of a woody plant takes place at the tips of the branches and roots, or at the apical meristem of each limb.  The cells in the apical meristem are undifferentiated,having the potential to become a wide variety of plant organs, much like stem cells in animals.  The parasite, be it a wasp, bacteria, or virus, co-opts these “stem” cells and gives them new instructions.  In a way the galls are akin to a tightly controlled cancer initiated by the parasite organism.

The Twig Galls I was looking at today were insect formed and, as such, the insect needs to escape the protective structure once it is mature.  Many of the galls had little holes in them showing where the little wasps has crawled out.

Exit holes in a Twig Gall - California

Exit holes in a Twig Gall – California

The variation in galls is astounding.  I have seen leaf galls on wild roses that look like tiny sea-urchins dipped in vermillion.  There are galls that not only force the plant to grow a protective structure around it, but that trick the plant into producing nectar to attract ants which in turn protect the growing larvae from predators.  Many are extremely colorful and the shapes are widely varied.

Colorful leaf galls on a Sugar Maple leaf - Vermont

Colorful leaf galls on a Sugar Maple leaf – Vermont

The common theme is that the galls are all formed in developing tissue, leaves, new twigs, flowers, roots, or fruit.

A gall on Shadbush fruit - Vermont

A gall on Shadbush fruit – Vermont

Some of the Ichneumonidae wasps that make so many of the galls we see have developed a biological metallurgy, evolving zinc and manganese coated ovipositors which they use to inject chemicals and hormones into the plants they co-opt.

The specificity and regularity of the galls and the relationships between the plants and the gall formers speaks to a lengthy and complicated evolutionary history.

We pride ourselves (or are horrified by) our newly found ability to genetically manipulate plants and animals.  In truth, we have a long way to go before we catch up to what we often mistakenly call the “humble” insects.

Brown Pelicans: today’s Pterosaurs

I am a big fan of Pelicans. They may be my favorite birds, though claiming anything to be a favorite is a little silly. I like all pelicans, but it is the Brown Pelican (Pelecanus occidentalis) and its cousin the Peruvian Pelican (Pelecanus thagus) that are at the top of my pelican list.

Brown Pelican (Pelecanus occidentalis) banking away from a landing at Point Dume, in Malibu

Brown Pelican (Pelecanus occidentalis) banking away from a landing at Point Dume, in Malibu

The Brown Pelican is the smallest of the 8 species of pelican in the world. Small is a relative term when it comes to pelicans, the Brown Pelican weighs up to 12 pounds (5.4kg) and has a wingspan up to a little more than 8 feet (2.4 meters). It and the Peruvian Pelican, which is nearly twice the size of the Brown Pelican, have a hunting strategy that differs from all other pelicans and one that is great fun to watch.

Pelicans are extremely successful apex predators. Their primary hunting tool, their beaks, have remained relatively unchanged for 30 million years as evidenced by a remarkably intact fossil from southern France. Pelicans have the largest beaks of any bird, a long affair with a sharp hook at the end and a large pouch underneath. Like baleen whales pelicans gulp huge mouthfuls of water and food (fish for pelicans) and strain the food from the water. Most pelicans do their fishing from the surface of the water, floating along like immense ducks, dipping their heads into schools of fish to grab a meal.

Brown Pelicans have an entirely different strategy.

Brown Pelican diving for fish.  View the fullsize image to see fpanicked fish leaping clear of the water to escape the pelican

Brown Pelican diving for fish. View the full-size image to see panicked fish leaping clear of the water to escape the pelican

Pelicans can see through the water well enough to spot fish near the surface. Brown and Peruvian pelicans hunt from the air in a delightfully cavalier fashion. When they spot a school of fish they dive for them, but this is not the elegant, dagger like dive of the gannet, this is the lumbering crash of a falling boulder. They fold their wings and plummet from the sky, more-or-less beak first, impacting with a great explosion of water. Their version of a dive is more akin to a drunken stumble into the pool than it is the clean Olympian dive. Despite the seeming lack of grace, their hunting strategy is effective.

While the dive of a pelican exhibits a singular lack of grace, they are elegant precision flyers. Pelicans of all species are probably best known for their surface skimming flight.

Brown Pelicans skimming the water - the lead pelican does not seem hindered by the loss of an eye

Brown Pelicans skimming the water – the lead pelican does not seem hindered by the loss of an eye

Being large, heavy birds (the largest species of pelicans weigh upwards of 20 pounds), pelicans use as little energy as possible when flying. We see them most often flying low over the water, wings nearly touching the surface of the ocean. The weight of their bodies compresses the air underneath them, making it more dense. As a result the air provides more lift, in effect they are riding on their own cushion of air. We make vehicles that do this, hover craft, and far more impressively, the Soviet ekranoplan vehicles.

Pelicans are adept surfers, riding the slight updraft of air above the curl of breaking waves.

Surfing Pelican

Surfing Pelican

Large air-sacks under the skin and hollow bones help pelicans float and a tough layer of fiber in their breast muscles helps pelicans keep their wings extended during long flights. Like other large birds pelicans search out thermals and other updrafts to climb into the sky for long flights.

I find Brown Pelicans to be surprisingly colorful.

Pelican eying me with suspicion

Pelican eying me with suspicion

Their heads have yellow, red, and a bluish tint as well. I suspect that the vibrancy of the colors changes in accordance with mating season. Peruvian Pelicans also share this colorful head, perhaps being even more colorful.

Peruvian Pelican (Pelecanus thagus)  in Paracas, Peru

Peruvian Pelican (Pelecanus thagus) in Paracas, Peru

Pelicans have a primeval aspect to them. We no-longer have Pterosaurs, but looking at Pelicans I feel a sense of what it must have been like when the sky was full of those wide-winged, short-tailed flying creatures.

Landing averted

Landing averted

Hummingbirds – miracles of evolution

Of all birds hummingbirds are one of the most fun to watch.  They are fast, colorful, and tiny, the smallest ones roughly the same size as a large moth or butterfly.  They are probably best known for their maneuverability.

Anna’s Hummingbird (Calypte anna) coming in for a landing. Note the small tail, the curve of the body, and the large wing muscles.

These birds are compact and extremely well muscled.  Their tails are short and flexible, notice how the tail of the Anna’s Hummingbird in the above photo is curved to the side and folded to cup the air to assist in guiding the bird in to its landing spot.  Their wings are short with thick muscles covering the limbs and have a range of motion far greater than that of other birds.

The name Hummingbird comes from the noise of their wings beating at 25 beats per second, about 1500 beats per minute. This high wing-beat and the extraordinary wing flexibility allows hummingbirds to hover far more effectively and energy efficiently than any other bird.

To hover they flap their wings in a figure-8 pattern, generating lift on both the down and upstroke.  Approximately 75% of the life of generated on the down-stroke with the remainder on the up-stroke.  The University of Texas has some nice graphs and charts providing more detailed information on how this works.

Anna’s Hummingbird hovering in front of Tobacco Tree (Nicotiana glauca) flowers

In to achieve this maneuverability hummingbirds give up the ability to glide.  In effect they have no low energy flight, they are always running at near full speed.  A 170 pound person would need to eat (and metabolize) 130 pounds of bread a day to keep up with energy output of a hummingbird.  Their energy output is so great that they enter torpor at night, a sort of hibernation.  If they did not do this the hummingbird would starve to death during the night.

Hummingbird flight characteristics are very nearly a blend of bird and insect methods of achieving lift.

Hummingbirds are generally extremely colorful, especially the males.  Like many birds this color is not pigment generated, but is the result of highly specialized feathers light refracting feathers.  Think of oil on water, that rainbow sheen that you see when light reflects from it.  Birds use the same technique, but in a far more specialized way.  Rather than an undifferentiated rainbow of colors the micro-structure of the feathers refracts only specific colors.  The natural color of the feathers is a dark brown, almost black.

Anna’s Hummingbird (Calypte anna) perched on a non-native Tobacco Tree (Nicotiana glauca)

I know I’ve used this photo before, but it illustrates the refraction vs pigment issue well.  The bold purple-pink behind the bird’s eyes is the color we associate with the male Anna’s Hummingbird’s head and gorget (the throat portion).  The dark, almost black, feathers are at the wrong angle to reflect the light and show the natural dark color of their pigment.

The tree in these photos is a Tobacco Tree (Nicotiana glauca), not native to North America, but native to South America, a place where there is a stunning variety of hummingbirds.  This tree and hummingbirds have a long relationship and have mutually evolved to reinforce that relationship.  Hummingbirds and may other birds and insects (and not a few mammals and reptiles as it turns out) drink nectar from flowers.  Not everyone who drinks the nectar will pollinate the plant, thus special relationships evolve.  Plants with long tube-like flowers (penstemon, humming-bird sage, tobacco, monkey flowers, heliconia, etc) are specialized to provide nectar for animals with long tongues that can reach the nectar.

Hummingbird tongue

Hummingbirds not only have long, narrow beaks, they have long, feathery tongues with which to lap up nectar hidden deep inside the tube-like flowers.  As they drink the plant deposits pollen on the beak and sometimes the bird’s head (two photos up you can see the pollen discoloring the hummingbird’s beak).  The next flower the bird visits gets a little pollen from the previous flower and the plant is happy.

A quick look at the shape and color of flowers will often give you a good sense of what type of animal the plant relies on for pollination.

Hummingbird catching insects under a Coast Live Oak

Hummingbirds need protein as well.  Some, such as the Anna’s Hummingbird, catch insects in flight, many others raid spiderwebs for insects.  Here in North America this is a relatively safe prospect, but in parts of South America there are spiders that will happily catch and eat a hummingbird and spin webs more than strong enough to trap the birds.

Hummingbirds have such a need for vast quantities of high energy foods that they are often extremely territorial, engaging in vicious fights and high speed chases.  Like most animals they would rather warn opponents off than waste energy fighting them.  Different species have various methods of letting others know how tough they are.

Anna’s Hummingbird staking out its territory

The little fellow above is marking out territory by fluffing out his head feathers.

One of the most amazing things about hummingbirds to me is that they migrate long distance, some species crossing the Gulf of Mexico in one long flight with no food.  At the shortest distance this is a flight of 480 miles, many birds fly closer to 600 miles to make this open water trip.  For a bird that only weights several ounces, cannot glide, and needs to eat constantly this is a truly remarkable voyage.

On a final note, hummingbirds are far more intelligent than most people realize.  Their memories are phenomenal, allowing them to keep track of individual flowers within their territories and when they were last visited for nectar.  They have the largest brain-to-body size of any bird.