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.

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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.

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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.

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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.

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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.

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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.

Segovia: sandstones and granite

I have always loved things made of stone, especially ancient constructions.  The stone-masonry I have done has only increased my respect for the strength, vision, and talent of past masons.

Vermont garden wall

Small garden wall of Panton Shale for a friend in Vermont

Most of my stone projects have been small in scale.  The largest project was a 180 foot long retaining wall standing between 2 and 6 feet high, using 30 or 40 tons of stone.  That seems large when you’re doing it by yourself, but that’s a tiny project, barely larger than the little garden wall in the photo above.

In Peru there were some truly astounding pieces of megalithic engineering, many of them little known like Lanche and Kuelap, others well known like Saqsaywaman.

Walls at Saqsaywaman.  For scale zoom into the center of the full-size image to see the person.

Walls at Saqsaywaman. For scale zoom into the center of the full-size image to see the person.

Two days ago I went to the small Spanish city of Segovia and got to see several astounding pieces of stone-based architecture.  The first of these is the ancient Roman aqueduct.

The aqueduct in Segovia

The aqueduct in Segovia

The aqueduct runs about 15 km from the mountains into Segovia, with a 683 meter long raised section running through town.  The tall double arch of granite blocks is impressive enough by modern standards, even more so when you consider that it was built in the 1st or 2nd century, that the granite had to be carried in from the mountains, and that it is a dry-laid structure (no morter holding the blocks together) that has been standing for 1800 or 1900 years.  Clearly, this is a place with few earthquakes.

Granite is a favorite building material for many people.  It is an igneous rock that bubbles up in volcanic flows and cools in place.  The size of the crystals in the rock give an estimation of how long it took for the rock to cool and how much water there was in the melt.  The colors tell of the mineral content.  This granite is pale, with moderately large crystals weathering out, leaving the exposed stone extremely rough to the touch.

Due to the way it forms granite has no preferential cleavage plane, meaning that, given the right tools, it is easy to shape into whatever form is needed.  It is a dense and strong rock as well, another reason it is often used as a foundational material.

The blocks of stone making up the aqueduct are large, not enormous, but large, hundreds of pounds each.  At its highest point the aqueduct is 29 meters tall (that’s about as tall as a 4 or 5 story building).  Nearly 2 thousand years ago those blocks had to be hoisted up and set in place.  Clues as to how the Romans did so are carved into the blocks.

Lifting divots on the granite blocks

Lifting divots on the granite blocks

Each block was lifted into place with a pair of metal pincers, like those people used to carry ice-blocks with.  Divots were carved into the stone to prevent the pincers from losing their grip.  Presumably the divots were carved at the balance point of the block as well, a calculation I would be very curious to know how was done.

Supposedly Segovia was a “small outpost” when the Romans ran things in the area, though the effort and cost of building the aqueduct makes me question that assessment.  Small outpost or no, very little happened in the area for a long while, then in the 1200s the town began to grow and with that growth came the buildings that Europe is so well known for.

Castles and Cathedrals.  Segovia has impressive examples of both, the castle being the inspiration for Walt Disney’s version of Sleeping Beauty, and the cathedral being on the of the last of built of the great Gothic cathedrals.

Segovia cathedral

Segovia cathedral

Construction of the cathedral began in the 1500s, but took more than a century to complete.  The massive building looms over the city, glowing golden in the sunlight.

The first thing that struck me was neither the size nor the the tremendous amount of fine detail.  It was the color.  A warm, yellow/orange, not the color one associates with Gothic architecture, or with goths in general.  The castle, cathedral, and much of the rest of Segovia is made from this stone, not from the granite the aqueduct is made from.

The town of Segovia rests upon an outcrop of calcareous sandstone (sandstone with the grains cemented together by calcium rather than silica) and the land around rises and falls, exposing the bedrock in numerous small cliffs.  Sandstone is a sedimentary rock, a class of rock at the opposite end of the formation spectrum as granites and other igneous rocks.

Sandstone tends to have horizontal cleavage planes, refection the initial depositional patterns, and is often soft and easy to carve.  The sandstone in Segovia seems made for carving and the cathedral  builders took full advantage of this.

Cathedral detail carved from sandstone

Cathedral detail carved from sandstone

Sandstone weathers and erodes easily, especially in the presence of water.  Segovia, despite being a dry region by my standards (about a half meter of rain per year) is considered a wet place in comparison with nearby areas.  As such the builders took pains to protect the soft sandstone, making their waterspout gargoyles of the more resistant granite.

Cathedral gargoyle rain-spout

Cathedral gargoyle rain-spout

Statues of sandstone have not weathered as well as those of granite.

A royal lion slowly weathering away

A royal lion slowly weathering away

The the level of fine detail in the cathedral architecture is reflected elsewhere in the town.  The older buildings and the castle are covered with patterned façades.  In the past these patterns seem to have indicated which family owned the building and in a few cases older patterns could be seen under the more recent ones.

Old wall pattern, the material looks and feels like reconstituted sandstone.

Old wall pattern, the material looks and feels like reconstituted sandstone.

The castle, the Alcázar de Segovia, has a more simple pattern, but each intersection is studded with fragments of volcanic rock.

Looking up the castle wall to the battlements.  the small black studs are fig sized pieces of vesicular volcanic rock brought in from far away.

Looking up the castle wall to the battlements. the small black studs are fig sized pieces of vesicular volcanic rock brought in from far away.

Like many European castles the one at Segovia has gone through a number of iterations; fort, castle, palace, prison, artillery college, and museum.  It still serves the latter two roles.

The castle commands a wonderful view of the countryside in all directions.  One of the most magnificent views is of the cathedral:

Segovia cathedral from atop the Alcázar de Segovia battlements

Segovia cathedral from atop the Alcázar de Segovia battlements

In the opposite direction an old Templar keep and the sandstone cliffs much of the stone was quarried from to make the city are visible.

Templar keep and sandstone cliffs above the river below the castle

Templar keep and sandstone cliffs above the river below the castle

This has been a less science based post than most, but the trip to Segovia was far too interesting to keep all to myself.

The castle, aqueduct, and cathedral are the largest of the attractions, but not the only ones by far.  The food is delicious, mockingbirds flit about the city, interesting small plants grow from the old walls and on the red tile roofs, and great architecture abounds.

Small church in Segovia

Small church in Segovia

Meteor Impacts and Ourselves

I am fascinated and enthralled by things that fall from space and the marks they leave behind.  It’s not just my love of space, it’s is something far more profound, it is in part what those things signify.

Go to a museum, one that has meteorites.  Often there will be at least one display of a metallic body that you can touch.  Lay your hands on it, press your palms against it, feel the soft curves, the slightly nubby surface, the coolness of the blackened metal.  You are touching the core of an extinct planet.  That should give you pause and send a small shiver up your spine.

On Earth there less than 200 known, confirmed, impact structures.  Just looking at the map it is clear that the distribution is skewed to areas where there are many people (North America & Europe), exposed bedrock (Canada & Scandinavia), or regions where weathering is slow (Australia & North Africa).

Confirmed impact structures on Earth from:

Every other rocky body in the solar system is liberally coated in the scars left by impacts.  The Earth bears the history of its impacts in a different way.  Weathering, plate tectonics, and the oceans have served to hide the marks of the numerous past impacts.  Except…

The global ocean, that covers 70% of the surface of the planet to a depth of 7 miles in some places, this, the single largest surface feature of the planet, is impact derived.  It is believed that ALL the water on the planet arrived by cometary impacts soon after the planet formed.  The Moon is another large impact structure, a relict left over from  the collision of the proto-Earth and another roughly Mars sized body.

The frequency of large impacts has, thankfully, fallen over time, but they still happen.  Some of you, I hope all of you, may remember the comet Shoemaker-Levy 9, the comet that crashed into Jupiter in 1994 after being torn apart by Jupiter’s immense gravitational field.  The fireballs in Jupiter’s atmosphere were larger than the entire Earth, and there were multiple fireballs.

Shoemaker-Levy 9 impact on Jupiter

The energy released by each of the Shoemaker-Levy impacts was on a par with the Chicxulub impact in the northern Yucatan 65 million years ago that is implicated in the demist of all terrestrial animals larger than a piece of carry-on luggage.

On Earth impacts are still frequent, but most are small and do not survive passage through the atmosphere.  Think shooting stars, grains of sand and dust traveling at orbital speeds, around 20km/second.  Several months ago, on the last day of February, I was treated to a something more dramatic than one of these little grains of dust.  A little after 10pm on the 28th I was driving under a clear sky and the snow covered landscape lit-up with a bright blue flash.  I later found out that the flash of light had been seen from New Jersey to Quebec.  This was just one of the many fireballs that flash in the sky each year, probably something small only a few meters in diameter, an explosion not more than a few kilotons.

In a few places the scars left on the ground from large impacts are still visible.  One of my favorite ones is in NE Canada.  Canada is an excellent place for finding impact structures as much of the Canadian Shield is ancient, exposed bedrock.

Manicoaguan impact crater turned into a reservoir

The Manicoaguan impact is about 215 million years old and approximately 60 miles across.  It has been dammed and the island in the middle is now one of the largest fresh-water islands in the world.  Big impacts like this are rare, but they leave dramatic remains behind.

Small impacts are surprisingly common, the frequency rapidly trailing off the larger the impact.  This is good news, but the picture is very incomplete as we have only been able to watch carefully for a short period of time.

Impact frequency Table from

We are struggling to understand how the universe fits together and have tremendous difficulty comprehending the scales and energy involved.  We are too used to thinking on our small scales, our bodies, our houses, maybe our planet, for a few our solar system or galaxy.  Our solar system is huge, our galaxy immense, yet in the lager context of our body of knowledge and what we can see even the Milky Way galaxy is barely a microscopic speck.

Look at the ocean, lay back and watch the trails left by falling meteors, look at the background of stars, go to a museum and touch the heart of a planet, if you live near an impact crater go visit.

We often say, “We are all connected,” and this is true, and that web of connection is far greater, wider, and deeper than most of us realize.


North American porcupines specifically…  Erethizon dorsatum to be even more specific.

I like porcupines. They are large and slow-moving, meaning that when you find a live one in the woods you can often get a really good look.  Their defense is to turn their back, erect their spines while periodically slapping their tails, and give you dirty looks.  Usually you will encounter them in a rocky den or in a tree, positions from which they will not flee.  On the ground they will scurry to a place where they can present you with their spines while hiding their faces.

They have a very good reason for this strategy, two really.  One is that their back and tail are densely covered in long, loosely held, barbed harpoons that will gradually work their way deeply into any flesh they encounter.  Many a dog owner will unhappily tell you of traumatizing encounters their dogs have had with porcupines, often followed by either a compliment for their dog’s learning ability for avoiding porcupines from that point on, or with a disgusted expression of affection for their dog despite its incredible stupidity for not learning to avoid porcupines after the third or fourth encounter.

To actually catch and kill a porcupine with your teeth and claws is a dangerous, potentially fatal proposition.  This brings us to the second reason porcupines huddle rather than run.  Their primary predator in New England, and in much of northern America, is the fisher (Martes pennanti), a weasel of largish stature, by weasel standards.  Contrary to what the fisher’s name suggests they are primarily forest and tree-dwelling animals and the only non-bipedal North American animal that regularly, and successfully, hunts porcupines.

Weasels are fast.  They are meat eaters.  They are the sports cars of the animal world; energy to burn, but you have to fill them up often with costly fuels.  They do not hibernate.

Porcupines are the electric forklifts of the animals world.  They are slow and they are tough.  They also do not hibernate.

One of the things that amazes me about porcupines is that, despite the low quality, high volume food they eat and the virtual lack of fur under the posterior spines, they remain active all through the winter.  They are large, for a rodent, just a little smaller than a modern American beaver, but they are not all that big.  A porcupine has about the surface area of two basket balls and slightly less volume.  When it’s -20F that’s a bad surface area to volume ratio to have, and a rock crevice, boulder cave, or hollow tree is  poor shelter from the cold.  They are tough creatures.

Unchecked porcupines can reach densities that make foresters tear their hair and reach for their guns.  They are not gregarious animals, neither are they particularly territorial.  Like many animals their willingness to tolerate others is resource dependent, and, in the absence of predators, in an area with sufficient resources such as food and denning sites they will proliferate.

This happened in New England after fishers were hunted to local extinction for their rich fur.  It’s actually more complicated than that, as the spread, species composition, and variation in age of the trees in the New England Forest underwent dramatic changes as the land was converted from Native American land to simple American land.  Fishers were killed and porcupine numbers skyrocketed.

In Vermont the damage to the regrowing forests was so great that fishers were reintroduced to the state in the late 50s.  Vermont, like many New England states had been paying a bounty on porcupines for decades before fisher reintroduction.  The bounties started off at 5 cents an ear (per pair I’d assume) and eventually reached 25 cents an ear.  By the time fishers were reintroduced Vermont Fish & Wildlife reports that around $160,000 had been paid out in bounties.  Think about that… that’s a lot of small change.

In any event, by the 70s fisher reintroduction was considered to be a success and porcupine numbers to be manageable, except for the odd dog owner or two.

So, why do I like porcupines?  Well, they’re an animal you can track easily, get close to, and spend time next to really studying.  How long can you stand next to a rabbit, trout, bear, or deer out in the wild?  I’ve stood watching rabbits 20 feet away for perhaps 30 minutes, but nearly had to hold my breath while each tiny movement of mine made them twitch and prepare to bolt.  Most of the time spent watching rabbits has been spent trying to be invisible and not think of them roasted over an open fire stuffed with potatoes, bacon, and onions basted with a thick rosemary – Dijon mustard – black pepper paste.  Animals can tell when you are thinking of eating them, I am convinced of it.

Porcupines are probably pretty good eating, but they are so easy to catch that many native tribes had taboos about catching them for food.  They were food for hard times, last resort stuff after all the animals you had to work to catch were gone.  Save the easiest for last, good advice in many situations.

You can get up to petting distance of a porcupine and sneeze and it won’t go far.  They’re wary, perhaps even afraid, but they have an effective defense and they know it.  You will eventually go away and they can get back to eating tasty bark, twigs, hemlock needles, and basswood buds.  At least, I hope porcupines think their food is tasty.

Perhaps most importantly, porcupines are part of the environment.  They also live on this planet.  They are part of its ecology.

This is important; they are part of how the environment (the discrete things out there) relates to itself (ecology).  Relationships, as I think we can all agree are complicated, sometimes non-intuitive, and riddled with hidden depths and counter currents.  When I look at a porcupine track I think of bobcats, fishers, trees, geology, land use, history, and everything those touch.

Like everything else, porcupines are a window into a larger world, if you allow them to be.