Crossing Tehuantepec

If you look at a topographic map of Mexico, you’ll see a series of mountain ranges extending from Oaxaca in the south through the volcano-studded centre to the northern ranges that extend into the U.S. Their cooler altitudes hold a fauna and flora with many relationships to those of the United States and Canada. Indeed, these Mexican highlands are the heart of North America for many groups of organisms, the place where their diversity is highest.

This broad network of mountains ends at one of Nature’s important boundaries: the Isthmus of Tehuantepec, a swath of low elevation cutting across Mexico at its narrowest point. The isthmus isolates the bulk of Mexico’s highlands from a smaller set to the east, those of Chiapas. The Chiapas highlands are rather different, biologically more related to those of Central American countries to the east and south.

Isthmus of Tehuantepec, shown with arrow (map from Google Maps)

We crossed the Isthmus of Tehuantepec last week, signalling the midway point in our #Mexigonus2017 jumping spider expedition, as well as a transition in our team members. We left Arturo Casasola behind in Ixtlán, and bade farewell to Ricardo Paredes on arrival in Chiapas. Both boosted the success of our expedition enormously. Arturo gave us a home base and guidance to perfect habitats, where we discovered the amazing green ghosts, purple tomatoes, and others. Ricardo not only did the driving, heroically, but he also added to our search effort. To my eternal gratitude, his sharp eyes allowed me to see the blue legged Mexigonus species again.

We spent the last week in Chiapas with two new team members. Jorgé León, a faculty member at ECOSUR, guided us to interesting habitats and facilitated our logistics, providing local knowledge that was vital for our work. Gerardo Contreras, a doctoral student at UNAM, not only has been another hero in driving us to far-flung places, but also a role model for us in going out fearlessly at all hours of the day (and we suspect night) to search the forests for the scorpions he studies. We have now finished with the Chiapas portion of the trip, and in the next few posts I’ll report on the discoveries that Jorgé and Gerardo have enabled.




Bell-bottom pants

On the weekend, our #Mexigonus2017 jumping spider expedition stumbled on many bell-bottom pants, but not the kind you’re thinking of. After leaving Ixtlán, we drove south to San José del Pacifico, a little town in the Sierra Madre del Sur mountain range famous (so it seems) for its interesting mushrooms. Around our little cabin in the oak-pine forest at 2500 metres elevation, and then along our hike up the hill behind it, we found three different species of Mexigonus whose males have fringes of black hairs on either side of their first legs. It makes the legs look much thicker than they are, giving the illusion of bell-bottom pants.

The next day we found two more fringed species, giving a total of 5. Here they are:

Mexigonus species with fringes on the sides of the first pair of legs

OK, maybe they don’t look like bell-bottom pants to you. The fringes don’t actually get wider toward the tip (like a true bell-bottom), but rather they don’t taper as much as normal, so (to someone who is used to seeing spider legs taper) it seems as if they are getting wider. Believe me.

Here is another view of the five species, in the same sequence as above:

Same Mexigonus species with lateral fringes on the first pair of legs

What’s strange is that we didn’t find any species with lateral fringes in the mountain range north of Oaxaca city. Is there a local diversification of them in the Sierra Madre del Sur?

By the way, all 5 of these species appear new to science.

Magic rediscovered

Arthur C. Clarke once wrote “Any sufficiently advanced technology is indistinguishable from magic”. There is an implicit shift of observer here, from those who make the technology (to whom it isn’t magic) to those who see the technology for the first time (to whom it looks exactly like magic). As an evolutionary biologist, I would suggest a generalization of this: “Any sufficiently advanced creative process generates products that are indistinguishable from magic.” Natural selection is one such creative process, and its products often seem as magic before we get a chance to study them.

As a 25 year old biologist I went on a grand expedition to Mexico with Stewart Peck, Jarmila Kukalova-Peck, Bob Anderson, and Mike Kaulbars. We drove from Ottawa to Chiapas and back to Canada. The trip was full of new experiences for me, but there was a singular moment I’ll always remember — the capture of a jumping spider on the road from Valle Nacional to Oaxaca City. Along a path in the cloud forest at about 1250 metres elevation, I found a handsome male spider with black, white and red markings, and a little brush of black hairs on the tip of the first leg that made it look like he was carrying a semaphore flag. When I put it in a vial to look at it, I saw a glow of delicate sky blue metallic hairs shimmering on the femora of his first legs. A sense of magic overcame me, the first time I’d experienced it. How could something like that exist without magic? The glow of blue was otherworldly. Of course, evolutionary biology has found that sexual selection can make such things exist, but when first encountering a marvel like this, magic springs to mind.

Thirty four years later I find myself in Mexico again, retracing some of the same paths. With considerable excitement we arrived to the same site to look for this blue-legged marvel. The team spread out in search of magic. In the first few minutes I found what I’m pretty sure are juveniles of the species, but no males. It was morning, and the ground and plants were still warming up, so we expected the males would take a bit of time to bother to wake themselves up and present themselves to the world. After perhaps an hour, Ricardo Paredes reported through our walkie talkies that he’d found a jumping spider with blue legs. I wasted no time in traversing the 100 m or so to Ricardo. In the vial he handed me, there it was, the mythical creature.

Here it is:

Mexigonus “blue legs”, male

This is what he looks like from above.

Mexigonus “blue legs”, male

Here is Ricardo at the site where he found the male hopping through small plants — right along the highway!

Ricardo Paredes León, where he found the blue-legged Mexigonus

And I have to put in another, gratuitous, picture of his blue legs. Note that both the first and second pairs of legs have blue femora.

Mexigonus “blue legs”, male

We didn’t find another adult male, but we did find some juveniles, including a young male (with one moult to go), which we will try to raise.

Magic still exists.

Shivering for diamonds

There was good news and bad news. The good news: we had found something new and special at Humo Chico, the green ghost Mexigonus jumping spiders. The bad news: we had not found any of our target, the delicate “diamond” jumping spiders. Disappointed, we went to the restaurant along the highway there, thinking to do a quick look before eating lunch. I’d found the diamond Mexigonus in 1983 near where the restaurant now stands, but there had been no restaurant then, and the area in the intervening years had been considerably disturbed by human presence (that was the reason we started instead in the undisturbed habitat along the road to the microwave tower).

As I went to try one last time, I was dripping wet and very chilled, for I’d not brought a jacket. When packing for a trip to Mexico, I had stupidly not imagined the chill of a rainy day at 3000 metres elevation. Just beside the buildings of the restaurant complex, I started beating the moss- and lichen-covered bushes. First beat, two specimens of diamond fell on my sheet. What relief, what satisfaction. They were still incredibly common at that particular spot, despite the degradation of their habitat. We got lots of specimens, including both forms of male I’d seen in 1983. Here is a male with just the first pair of legs black:

Mexigonus “diamond one dark”, male

And here is a male with the first two pairs of legs black:

Mexigonus “diamond two dark”, male

Now we can figure out whether they are Mexigonus, and whether the two forms of males represent different species. (I suspect so.)

In the end it was a very satisfying day at Humo Chico, finding our target diamonds and also new things like the green ghost. Shivering, the first thing I ordered at the restaurant was a hot chocolate.

Green ghosts

We chose as an important site to visit on this jumping spider expedition the summit of highway 175 as it goes north from Oaxaca City. There, at about 3000 metres elevation in a place called “Humo Chico”, is a foggy, damp elfin forest. In 1983 on my first trip to Mexico, I caught some elegant little jumping spiders there. Uriel named them “diamond” after the shapes of their markings. We can see that they are generally related to Mexigonus, but it’s not clear to us that they are actually Mexigonus, as they are more delicate-bodied than the other Mexigonus species we know. If they are Mexigonus, they would show the genus can evolve to such a body form, and so they are important for Uriel’s project. Their other point of interest is that two colours of males were found in 1983: one with the first two pairs of legs black, the other with just one pair of legs black. With fresh specimens, we could get new data to decide if they were Mexigonus, and whether the two forms represented different species.

We drove up on Monday from Ixtlán to this high elevation site, but it was misty, raining. We went first to the microwave station at the top, and found very little. All of us were discouraged. We decided to walk down to the main highway. I’m accustomed to jumping spider species staying hidden in their retreats, and so I expected that my anticipation in seeing these delicate spiders would be unrewarded.

And then a surprise occurred. In the drizzle, a jumping spider dropped on my beating sheet that I didn’t recognize at all. Pale and with long legs, it looked ghostly. When I picked it up in the vial I saw that it was a male with a big white moustache, and little black tips to the first legs. Beneath its white hairs the legs were a soft green colour. No jumping spider like this very distinctive species has ever been described. Here is the beautiful male staring boldly at my camera:

Mexigonus “green ghost”, male

Here are a male and female from above:

Mexigonus “green ghost”, male and female

We ended up finding 9 males and a few females of the green ghost Mexigonus. Even though I enjoy finding new species of any sort, whether brown and dull or spectacular, I have to admit that strange and colourful species excite me the most. Finding green ghost was a special moment.

But we didn’t find any “diamond” on our walk down to the highway. I was prepared to give up.

Purple tomato

In my last post I described our success in finding 5 new species of Mexigonus jumping spiders in the oak-pine forest above Lachatao, but I left unexplained one of the species: purple tomato.

That great prize of the day was found by Uriel. Beating some small bushes and branches of fallen pine trees, he found some female Mexigonus that looked really interesting. We decided that it was worth trying to set the whole team looking for a male. The news soon spread: Uriel found a male, and he had figured out the species’ habitat: on exposed or dead branches of bushes or fallen trees, less than a metre from the ground, with just the right amount of sun.

The male is a spectacular creature with black and white fringes on the legs and glistening palpi. We eventually found three males and a few females. Here are photographs of the male

Mexigonus “purple tomato”, male

and of the female

Mexigonus “purple tomato”, female

The male’s biggest claim to fame, though, is the purple sheen on his jaws (chelicerae). He guards the sheen modestly as he walks around, covering it with his palpi. It’s been therefore difficult to photograph. We managed to get a male to briefly do courtship, and of course then he spread his palps to show his purple jaws to the female, modesty abandoned. Here is a screen shot from the video of courtship. You can see the shine of purple just below his eyes.

Mexigonus “purple tomato”, courtship pose

We call this species “purple tomato” because his body form suggests he is related to the bright red species I showed in my first blog post about the expedition. That species was the first one we knew of its group, and so we have started referring to all of the species of the group as “tomatoes”, whether or not they are red. The Lachatao one is just the third member of the group we know, and its jaws compel us to name it “the purple tomato”.

The Lachatao day was a spectacular way to start an expedition.

Preconceptions dashed by sad faces, black pepper, and purple tomatoes

For our first full day of collecting, Arturo Casasola guided us south of Ixtlán, to the community of Lachatao. The winding mountain road brought us to a pine-oak forest that looks a lot like Canada — until you see the bromeliads decorating the trees. It wasn’t quite wet enough to be a cloud forest, but it had some of the elements — not only the bromeliads, but also many other epiphytes (plants growing on other plants) on the branches of the oaks, especially lichens and mosses.

I brought to this collecting expedition a particular concept of where Mexigonus jumping spiders live: mostly on the litter of dry fallen leaves beneath trees. I had formed this idea from previous collecting of other jumping spiders. As I’d collect Habronattus, one of my favourite groups, on such leaf litter, I’d often find a few Mexigonus along the way.

Given this preconception, when we got to the Lachatao forest, I started looking on the leaf litter, and promptly found a little humble brown and tan Mexigonus species quite common there. Good! I decided to try something bold, to look on leaf litter not on the ground, but accumulated in the crooks of branches of the trees. I found a strange cryptically-coloured Mexigonus and was motivated to keep looking above ground. In the end, the team found this cryptic Mexigonus to be common on the epiphyte-covered branches of the oaks — not the habitat of my preconceptions.

We call this species “triste” (sad) for the melancholy expression on their little faces. Here is a male.

Mexigonus “triste”, male.

It turned out that that wasn’t the only Mexigonus living above ground in the forest. We found a small peppery black species by beating dead branches of trees in shadow. (Beating is a technique we use a lot — we hold a kite-like sheet under a bush or tree and shake or hit it with a stick. For more details see here:

In the end we found two species of Mexigonus on the ground, as I’d expected, but three species beating bushes and trees (sad face, black pepper, and a third that I’ll describe next post: purple tomato). All 5 of the species are most likely new to science. This is a happy way to dash one’s preconceptions.

On the road to Oaxaca

Here in Ixtlán de Juárez we took the day off from collecting to catch up with our processing of specimens. We collect the spiders live. When we return from the field, we sort them to species, choose ones to photograph, and preserve the rest, freeing up their vials for the next day. The photographs take a while, and when you add it to the basic note-taking and other duties (we hope to do videos!), we usually don’t quite get done the day’s tasks. Today I had a big pile of spiders that took most of the day to photograph.

So, a belated #Mexigonus2017 report on our trip down from Mexico City. The drive was smooth on the big toll highways, and of course we chose to make a few stops to look quickly for spiders. The highlight of the day for me was to find Habronattus nahuatlanus (at least, that’s what I think it is) at Santa María Tinú and to learn its habitat — in or under grass clumps, just like the recently described H. luminosus from Arizona. Here is the male, and female. The female wasn’t known before, so it’s good to see what it looks like.

Habronattus nahuatlanus, male (top row) and female (bottom row)

We’ve had many successes in subsequent days, and I’ll report on purple tomatoes, green ghosts, and blue-legged magic as soon as I can, perhaps not in chronological order.

By the way, for English speakers who don’t know Spanish, “Oaxaca” is pronounced (more or less) as the English “Wahaca”.

Expedition to Oaxaca and Chiapas

It’s been too long since I’ve been on a major field expedition, more than 3 years. Today I fly to Mexico to begin three weeks in the mountains of Oaxaca and Chiapas with salticidologists (jumping spider experts!) Uriel Garcilazo and Łukasz Trębicki and others interested in arthropods: Ricardo Paredes, José Arturo Casasola, Jorge León, and Gerardo Contreras. Uriel, Łukasz and I will be looking for new species of jumping spiders, with special focus on the genus Mexigonus. There are only a few species of Mexigonus described, but we already know that many more undescribed ones are hiding in the mountains of Mexico.

There are many poorly studied groups of spiders, so why did we choose to focus on Mexigonus? One reason is that it is an evolutionary radiation of the Mexican highlands, its species having diversified among the mountain ranges that fragment the landscape into isolated patches of habitat. Studying the diversity of Mexigonus species and their evolutionary relationships could help us understand the biological history of this region. Another attraction of Mexigonus is the red or orange courtship ornamentation that males of some species have — attractive to the females perhaps, but to us attractive because red ornamentation is not common in salticid spiders. There’s a good chance that most salticids can’t distinguish red (colour blind, in a sense), and so when we find a salticid that can, it could tell us something about the evolution of colour vision.

A species of Mexigonus new to science, from Oaxaca.

Our expedition has been supported generously by Tila Pérez, Griselda Monteil, and Ricardo Paredes of the Universidad Nacional Autónoma de México (UNAM) in Mexico City. We’ll drive first to Oaxaca, where we’ll spend about 10 days collecting, based at Universidad de la Sierra Juárez (UNSIJ) with José Arturo. After that we’ll spend about 10 days in Chiapas, where Jorge León (EcoSur) has been guiding our plans. At the end of the trip we’ll attend the meetings of the American Arachnological Society in Juriquilla being organized by Fernando Alvarez.


Quest for a tidal spider

In my last blog post I described my somewhat obsessive quest to find the mysterious green-faced Habronattus of southern Arizona. It’s not my only such quest. Another that comes to mind was spent mostly waiting — for the chance to return Sonora to look for the strange tidal spider of the Sea of Cortez.

On the northernmost shore of México’s Sea of Cortez is a little town called Puerto Peñasco. The land there is a harsh, harsh desert, with sparse vegetation barely hanging on. The sea, though, is beautiful, and rich with life. Where they meet, the land blooms. The fluctuation of the tides has eroded inlets that are called “negative estuaries”, mud flats with river-like channels where the tides drain. These mud flats are covered with plants like Salicornia that are tolerant of salt water.

In 2003 I visited one of these negative estuaries, and found a male Habronattus jumping spider that I thought was immature, because it lacked the usual fancy colourful ornaments typical for adult male Habronattus. But a closer look showed it to be adult, a rather peculiar one, unlike anything I’d seen. When I got it back to the lab, I was confused by its features. Some of its traits suggested that it belonged to one group of species; others suggested it belonged to another group. Was it a hybrid? Did it occupy a special place on the evolutionary tree?

I called it “the Peñasco beast”. My curiosity was strong, but I didn’t get a chance to get back to look for more until 10 years later. Our little 2013 expedition, consisting of Heather Proctor, Geneviève Leduc-Robert, Sam Evans and me, arrived to Puerto Peñasco after the drive from Tucson. We were staying and working at CEDO (Centro Intercultural Estudios Desiertos y Oceanos), a scientific and educational centre that plays many roles in raising knowledge and awareness about the amazing ecosystems there. The estuary was close by, so every day we went to look for the Peñasco beast.

What we found, instead, was a different species of Habronattus that was quite striking: a little yellow-orange “monkey” with green legs and a stunning red face, hopping from plant to plant. It was common, and yet it was another new species, never before collected. Exciting, but where was the Peñasco beast? We found but a single baby, and nothing more.

The morning came when we were to pack up and leave. I was pretty disappointed. My colleagues offered to pack up, and urged me to go out one last time to look. So, I went out with our local guide Abraham Meza López to a new spot, a bit of a drive away. The habitat at the other estuary was a bit different. I found a female! And another! And a male! I was beside myself with joy, but at the same time, anxious. We were already late returning to CEDO, and I still wanted to look for more. I knew that the crew would be worried as to why we were late, and might be imagining bad things happening to us in the unfamiliar estuary. But how to tell them not to worry? We were in the middle of this desolate estuary, probably a few kilometers from the nearest human. I knew that none of my colleagues would have their Canadian or American cell phones turned on. But, I knew that they had computers, and internet access at CEDO, and they were probably bored (but anxious) waiting for me. So, I turned my cell phone on — signal! — and sent a tweet that we’d found the Peñasco beast. When I got back I was greeted with congratulatory hugs, rather than cries of relief, and so I knew they’d seen the tweet. And we had the Peñasco beast again!

Habronattus aestus and its habitat in the negative estuaries of Sonora

Habronattus aestus and its habitat in the negative estuaries of Sonora

The specimens we got in 2013 helped me to prepare the publication describing it as a new species, Habronattus aestus. The specimens were also used in a genetic analysis that found it to be a cousin of some species found around my haunts here in Vancouver (Habronattus americanus and Habronattus ophrys). Even when you travel far away, you find things with genetic ties to home.