POSTCARD from Mexico N°25

(By Fernando Rivadavia, December 7th, 2008 ) 

Moctezuma Canyon

        Sunday the 30^th of November, 2008, had already turned out to be a fantastic day : I’d found countless flowering P.lilacina. And the day before I'd finally discovered the type locations of P.martinezii and P.calderoniae. A memorable weekend by any standards! But I was still hungry for more...

            It was already nearly noon, but I wondered if it would still be possible to reach the Moctezuma Canyon and have time to hike at least 2h to where P.moctezumae supposedly grew... It was worth a try of course!

            I sped down the mountain along the dirt road, quickly leaving P.lilacina behind. The Moctezuma Canyon was really not too far away in a straight line, but to get there I still had to drive up and down two very high mountain ranges along endlessly winding. single-lane roads. Trying to do so at high speeds made me carsick, but it was a small sacrifice to pay.

            I finally reached the bottom of the Moctezuma Canyon at around 2pm. I left my car at the same little roadside bar in La Mora where Ed Read, Ruben Resendiz & I had set out from on our last attempt in August 2006 (see my Postcard 19). Except this time I didn’t waste nearly as much time trying to get to the canyon entrance itself – having learned a few important lessons about the easiest paths from our previous attempt.

            Hiking into and up the Moctezuma Canyon (see pictures 1-3), I kept my eyes open for rattlesnakes – we’d seen a few of them last time. The river seemed less muddy than in 2006, which made the several river crossings a bit easier since I could better see where I was stepping. But what worried me more than the rattlesnakes was that the water level seemed to be about the same as before... All along the hike I feared not being able to get past the small waterfall where we'd been forced to turn back in 2006 because of the high waters.

            Nonetheless, I was highly motivated and made great progress, reaching the dreaded spot in only 1h (it took us 2h last time). To my absolute delight, the water level was not only lower in the pool of water (only about knee high), but there was also a dead tree trunk now conveniently positioned at the base of the ~3m high smooth rock wall next to the waterfall! I effortlessly stepped on the tree trunk and climbed to the top of the rock wall in mere seconds.

            In disbelief, I stopped for a quick breath at the top and smiled at my luck before pushing ahead. But as I continued to hike upriver, I decided to go a little bit slower, looking more carefully at my surroundings, since this was all new territory and P.moctezumae could be anywhere…

            It was a little hard to concentrate though because of an unexpected nasty side effect of hiking the canyon in the dry season: BURS! The vegetation was much drier and one plant species was releasing hundreds of tough little burs with very prickly spikes. When I tried to remove them from my clothes, their minute tips would break off under the skin. Although I could hardly see them, I could feel them when I rubbed my skin in the wrong direction. Ouch!!! And to make matters worse, due to the several river crossings my clothes were constantly wet and clinging to my body, which brought those hundreds of burs in close contact with my skin, prickling me continuously as my clothes rubbed against my body. Hiking the Moctezuma Canyon that afternoon was turning out to be minor torture and I sure hoped to be compensated with beautiful populations of P.moctezumae!

            A little further up the river from the waterfall, I noticed some interesting palm trees which seemed to grow in the wetter parts of the canyon (see picture 4). But these were a little far, on the opposite side of the river, and not even on a north facing-side of the canyon. So I decided to ignore them for now and focus my hunt for P.moctezumae further upriver.

            The further I hiked, the narrower and deeper the canyon became. The surrounding mountains rose claustrophobically ~1000-1500m above the canyon floor. But this was good news since it meant less direct sunlight and thus more likely to harbor Ping habitats. Another half hour of hiking brought me upon another small waterfall with rock walls on both sides. There didn’t seem to be any way around it, I was blocked off again! Crap!

            Frustrated, I stood there for a minute looking at the waterfall, thinking I’d been defeated by the Moctezuma Canyon once more. Not giving up, I began scanning the canyon walls, looking for a path climbing the rocks to the top of the waterfall. And there, on the opposite side of the river, maybe 100m downriver (hidden from view as you come upriver), I noticed a rock wall with calcareous formations like the inside of a cave (see picture 5). Why, that looked like a perfectly good Ping habitat! And it seemed to be covered in light-green-colored leaves too... Was my mind playing tricks on me or was I seeing a few dark-pink blotches amidst the green?

            Afraid to get my hopes up, I darted silently across the river towards the wall. About halfway there I started yelping with joy as I realized that I'd finally found my first wild population of P.moctezumae!!! In wide-eyed disbelief, I quickly closed the gap to the wall, hardly looking at the ground as I ran.

            I started taking pictures immediately, while admiring the beautiful Ping-covered wall. There was a very dense population of P.moctezumae growing in what seemed to be the wettest part of the wall, on the left side, with more plants growing sparsely for another ~20-30m to the right (See picture 6). Several plants were in flower, but these were all out of reach (see pictures 7-9), except for one plant which I had to nearly do acrobatics for, in order to hold on to the rocks while taking pictures at close range.

            Interestingly, this wall was not north-facing (as is usual for most Ping habitats) but south-west-facing. Due to the depth of the canyon I guess direction doesn't really matter much since little light reaches the bottom anyway. Considering this is a perennial species that supposedly does not go dormant, I was curious to see that almost all the P.moctezumae seemed to have winter rosettes, although often still surrounded by longer summer leaves (see picture 10). To me, this made the plants not look their best and I confess I was a bit frustrated. Yes, I was in ecstasy at having finally found P.moctezumae, but after so much effort to find this species over the years, I'd been hoping for better-looking specimens...

            It was getting late in the afternoon and my drinking water was running low, although I'd brought more than on my prevous trip, when we'd run into the same problem. But instead of turning around and heading back down the canyon, I decided to push a little further on, in hopes of finding more and better P.moctezumae populations. Fortunately, it did not take me long to discover some...

            After finding a way up and around the waterfall which had stopped me in my tracks less than half an hour before (forcing me to look around and as a result discover my first populations of P.moctezumae), another ~10 minutes brought me around a bend in the canyon which presented me with a wondrous sight.

            Way up high above the canyon floor, maybe 200m up on a vertical cliff facing north-east, I could see a huge wet patch of rock which was covered in a thick green carpet (see pictures 11 & 12). I knew immediately that this must be P.moctezumae, thousands of them too! I tried zooming in with my camera and taking some pictures. Although the results were not too good, you can easily see a light-green patch with many dark pink flowers (see picture 13). Unbelievable!

            I was of course very tempted to climb the scree slope to what was surely a fantastic population of P.moctezumae, but sadly I did not have the timenor drinking water. I would need an extra 2h or so to reach this 2^nd population, take pictures, and return. It would have to wait for a future trip.

            But I was not yet finished with P.moctezumae! Although I couldn't hike up to this amazing patch high up on the canyon wall, the water that I could see seeping over the rocks must surely make its way down into the river at some point. On the river margin at the base of the scree slope I could see a few of those curious palm trees I'd seen earlier, which seemed to grow in the wetter spots – could they be a bio-indicator of P.moctezumae sites? So I hiked a little further up the canyon, hoping to find a 3^rd P.moctezumae population near those palm trees below the 2^nd population. And sure enough, I did!

            Right along the river margin was a very nice P.moctezumae population growing on sloping rocks seeping with water (See pictures 14-29). It wasn't as thick a carpet as the 2^nd site ~200m above, but there were hundreds of plants and very large & beautiful ones too. Here the P.moctezumae did not show any signs of dormancy and many were in flower. I was surprised at the huge amount of prey captured on some of the leaves!

            With this 3^rd population, full of large plants in bloom within easy reach, I finally felt that my P.moctezumae hunger was satisfied. I couldn't be any happier and snapped pictures non-stop from all possible angles. But unfortunately this lasted no more than 20-30 minutes since I still had at least 2 & 1/2h of hiking before reaching my car and the sun was quickly sinking towards the horizon. The canyon floor was already in full shade and would plunge into darkness fast once the sun set behind the horizon.

            I began scampering back down the canyon, trying to retrace my steps and take the best route, which involved several river crossings at key spots. I accidentally missed one crossing and ended up having to backtrack when I got to a cliff of sorts and there was no way down. But the second time this happened, I was able to leap/slide down into the knee-deep pool of water below, instead of going around.

            I soon passed the 1^st P.moctezumae site and said good-bye to this lovely species, wondering when (and if) I would ever return to this canyon and see this plant again. But it was too early for good-byes, I was still in for a little surprise...

            I was much closer to the river's edge when I reached that first patch of palm trees I'd seen earlier. As I approached the spot immediately below he palms, I noticed there was a hidden little rock wall dripping with water. Upon closer inspection, I could see a carpet of ferns as well as...  huge flowering P.moctezumae (See picture 30)!! I had to get closer for pictures, I had to cross the river.

            This was easier said than done. The river was very narrow and deep at this spot and in order to get to the opposite side I was forced to hold my backpack above my head as I waded with water up to my chest, trying to keep a firm foothold and not be dragged downriver by the current. All the while I kept a firm gaze on my tantalizing goal immediately ahead and above me. It was like candy just out of reach of a child.

            There were only a few clumps of P.moctezumae at this 4^th population, but the plants were the largest and healthiest I'd seen thus far (See pictures 31-36). I only spent about 10 minutes taking pictures at this site before having to wade back (fearing for my camera held above my head). Curiously, this spot was just around the corner from the waterfall where we'd been forced to turn back on the previous trip. This bit of news is guaranteed to make Ed Read & Ruben Resendiz even more frustrated, knowing they'd been so close! 

            As I continued hiking down the canyon, I reviewed in my mind the wonderful events transpired that afternoon. I'd found P.moctezumae at last! So many years (and attempts) had passed, I couldn't believe I'd finally rediscovered this species! But at least now I understood why it had taken me so long. The more I searched for P.moctezumae, the more I realized that it was endemic to a very small section of the Moctezuma River canyon. It was a mere 1km between the populations I observed.

            Looking on Google Earth, I found that only 1km upriver from my 2^nd & 3^rd populations the steep cliffs disappear and the deep canyon gives way to a shallow valley that almost certainly does not offer any suitable habitats for P.moctezumae. And I knew from previous trips that this species does not occur for many kilometers downriver nor in the neighboring canyons. If rumors are confirmed and a hydroelectric damn is ever built in this section of the Moctezuma River, it would most likely condemn P.moctezumae to extinction.

            I find it truly amazing that many Ping species are seemingly so narrowly restricted to small geographic territories. I'd imagine such small populations are very prone to becoming extinct with any slight climate change over the centuries and millenia. But if extinction rates are high, then so must be the speciation rates, if you consider how many taxa are known from Mexico alone. And this possible high turnover rate leads me to believe that Ping species probably evolve very quickly (relative to other groups of plants at least).

            This hypothesis of fast speciation in Pings would support a suspicion I had from my travels in Mexico in 2006, when I explored the Toliman Canyon and found P.elizabethiae. The Toliman and Moctezuma Canyons run nearly parallel to each other before becoming a single canyon. Upon finding P.elizabethiae, I'd been surprised at how similar the flowers of this species were to those of P.moctezumae, which everybody knows since it is so popular in cultivation.

            Yet the leaves of these two species are entirely different, P.elizabethiae having small rosettes of rounded leaves. Was the flower similarity a case of convergent evolution to the same pollinator between species not closely related? Or had these two species split very recently in their evolutionary history, developing completely different leaf shapes while maintaining almost identical flowers?

            I suspect the latter hypothesis is probably closer to the truth, with the ancestors of P.moctezumae quickly evolving long leaves and thus taking better advantage of the permanent water oozing down the steep walls in that extra-deep and short stretch of the Moctezuma Canyon – whereas P.elizabethiae is forced into dormancy every year in its drier habitat and can not afford to have such large leaves.

            It was almost completely dark by the time I finally reached my car around 6:30pm. I'd run out of drinking water about an hour before and unfortunately the bar I'd parked next to was closed. So I had to quench my thirst with the nearly-boiling drinks that had been cooking inside my car the whole afternoon.

            Before I entered the car and drove off, I stood there for a while wondering what to do with all the burs on my clothes (See picture 37). I couldn't get in the car like that or I'd have those prickly burs sticking to the car seat and poking my ass for the whole drive back to Guanajuato! I had clean clothes to change into, but what would I do with all those burs on my hiking pants, t-shirt, and socks?? It would take ages to remove them all and my fingers would quickly be covered with tiny thorns. Maybe the burs would come off easily after a few weeks on their own, or after washing. But I wasn't even sure that US customs would let me through with all those burs. So after some deliberation, I simply hung up my bur-covered pants, socks and shirt next to the car and drove away, leaving them there as a present for any local willing to deal with the bur removal (See picture 38). Being used to it, they probably even had special techniques for removing those nasty burs from clothes.

            During the 4h drive back to Guanajuato, I basked in all the amazing memories of the previous 2 days. What a memorable weekend it had turned out to be! Not only did I see a beautiful flowering population of P.lilacina, but I'd finally reached two places that I'd been avidly pursuing for years: the type locations of P.moctezumae in the Moctezuma Canyon and of P.calderoniae and P.martinezii on the Sierra Gorda. All of this in a single weekend, what an unbelievable adventure!

            I'm almost certain I remember Sergio Zamudio (who described these and many other Mexican Ping species) telling me in 2003 that he'd seen P.elizabethiae growing near P.moctezumae and had even found a few natural hybrids between these two taxa. I did not see any P.elizabethiae in this section of the canyon, but do not doubt that it does grow there. Aaaaah, if only I'd had a whole day and more water bottles to explore the Moctezuma Canyon...

            Actually, I still had one more weekend in Mexico before returning home to San Francisco. Should I return to the Moctezuma Canyon and face the burs once again to explore further and better, to search for P.elizabethiae and its hybrid with P.moctezumae, and to climb up the scree slope to the 2^nd population so I could admire those walls covered in P.moctezumae? Or should I go exploring for other Ping species?

            These were the questions I asked myself over and over again throughout the following week...

Fernando RIVADAVIA