POSTCARD from Mexico N°22

(By Fernando Rivadavia, November 22, 2008 ) 

San LUIS POTOSI

    For my 2^nd weekend, out of a total of four during my latest work trip to Mexico, I decided to go to the state of San Luis Potosi. In order to include my work colleague, Natalhie, I chose a touristy destination as our main goal: an old mining town called Real del Catorce. Little did she know that I intended to explore for Pings all along the way there and back, hahaha!

            We left early on Saturday morning, the 22^nd of November, heading north from Guanajuato. The whole day we stuck to smaller secondary roads while driving through the state of San Luis Potosi, enjoying the views of the various types of arid landscapes. One of the exploratory detours we took that day – west towards Cerrito de Rojas – brought us up onto some highlands through an interesting little canyon with promising north-facing cliffs which I decided to hike up to and explore. Unfortunately I found no Pings in this area, although there were spots where thin films of water trickled down over the vertical rock surfaces.

            We arrived at Real del Catorce in the afternoon, after climbing a long winding road and driving through a rustic one-way tunnel a few kilometers in length. I stopped several times to explore for Pings along the roadside on the drive up, but found nothing. The white soil was very dry and it was somehow different from the clayish soil I’d seen in mountains just to the east where P.esseriana / ehlersiae grew – but sadly my knowledge in geology is far from sufficient to describe in what way they differed. Either way, the different soil seemed to say something about why I couldn’t find any mention in the literature of Ping collections for those highlands.

            After exploring Real de Catorce for a couple of hours, the cold temperatures at nearly 3000m altitude started chilling us to the bone and we decided not to stick around and discover how much colder it would get after sunset. So instead of checking into one of the rustic little colonial hotel up on the mountains where we’d probably freeze all night long, we instead headed back down to find a hotel in Matehuala.

            The next morning we headed back south along a different route, passing through a beautiful valley covered in Joshua trees, where rattlesnake and coyote skins were sold along the roadside. We took a detour east towards Villa Juarez, where in 2003 I saw P.gypsicola and P.takakii together with my friends Adolfo Ibarra & Ruben Resendiz (see my Postcard 3). Revisiting the area two weeks later in the season (plus 5 years), I was curious as to what I would find. Would all P.gypsicola be dormant? Would the annual P.takakii still be around, or would they already all be dead for this season? Would I find any more of the fantastic pink P.gypsicola X P.takakii that we saw in 2003???

            From Villa Juarez we took a road which had been partially asphalted since my last visit, and as we drove south and then west up the mountains we began seeing the white gypsum soils where the two Ping species grow. I soon recognized the north-facing hillside where we’d found P.gypsicola in 2003 and stopped the car alongside it. I convinced Natalhie that it would be worth the effort to see the Pings and we began climbing the banks by the road. In order to reach the P.gypsicola-covered hillside, we had to find a clear spot to cross through a thick patch of prickly bushes and other spiny vegetation growing parallel to the road. To my total surprise, all along this bushy patch were countless P.takakii in flower!!!

            Wow, I can’t believe we hadn’t seen a single P.takakii at this site in 2003! They probably weren’t in flower yet and we simply overlooked the tiny rosettes. Well, we didn’t even really know what P.takakii looked like back then, having seen only a picture of a flower. In 2003 we only found a small area with P.takakii a few kilometers further up the road. And here were hundreds of adult P.takakii in full flower & fruit, the larger specimens reaching around 3cm in diameter with up to 8 scapes each!

            Walking around, I saw that P.takakii grew in spots shaded by mounds of soil or plants like bushes, hechtias, and even the large rosettes of Selaginella lepidophylla. The delicate rosettes of P.takakii were mostly light-green in color, but many were yellowish or dark green and even pinkish. The scapes were dark green to dark pink, while the flowers of P.takakii have a wonderful combination of colors, (see pics or my description in Postcard 3), with the corolla lobes varying from a lighter to a darker shade of lilac.

            P.takakii seems to be very effective at capturing prey. Its leaves were often carpeted with tiny insects as well as occasional prey that seemed oversized for the minute leaves. I guess P.takakii has to be really good at what it does since it needs plenty of nourishment to make its extremely short & fast life cycle possible. My guess is that the natural life cycle of P.takakii lasts only around two months, with germination occurring sometime around mid to late October, and death due to frosts and dryness occurring somewhere between mid to late December. That’s fast!

            We found more P.takakii growing intermingled with P.gypsicola, but the two species very rarely grew side-by-side. They seemed to grow mostly in separate patches, apparently occupying slightly different micro-habitats (which I couldn’t really differentiate). Although I searched, unfortunately I didn’t find any of the beautiful hybrids we’d seen in 2003.

            As for P.gypsicola, most plants had retreated almost entirely to their winter rosettes and lots were in fruit. Yet some specimens hardly showed signs of going dormant and we even found a few open flowers! These were mostly old and ugly, but it still pushes forward the known flowering season of P.gypsicola in the wild by two weeks.

            Instead of driving back to Villa Juarez, like I’d done in 2003, I decided to drive further along that dirt road to explore for more Ping habitats and possibly find a way out to another highway to the west. The road climbed a little further to the top of the highlands and then zig-zagged down the other side. Although this other side of the mountain faced mostly west, we passed by several deep ravines along the way which had one side facing north. I explored one of these and found a vertical wall covered with P.gypsicola. We also found a north-facing spot by a curve in the road where there were plenty of P.takakii and P.gypsicola.

            Looking across the valley below us we could see more mountains with white gypsum soil and deep ravines which were probably also home to P.takakii and P.gypsicola. But we were too lazy and didn’t bother hiking all the way out to explore these, being happy with what we’d already found. We still had a long way back to the main roads and the gypsum soils soon disappeared behind us. The habitats changed continuously, as they tend to do in Mexico, and we stopped to explore a few places along the way, like mossy banks along the road and a small canyon with vertical cliffs – but no Pings.

            Eventually we made our way back to highway 70 and headed back towards the city of San Luis Potosi. It was a very long and winding road from the dry lowlands to the humid oak forests at the top of high mountains, then all the way back down to the dry valley on the other side, with hardly any spots to overtake slow-moving trucks. And when we finally did pass some of the trucks already near the top of the mountains, we began spotting P.moranensis on humid north-facing banks along the roadside and had to stop the car. I knew this site, near the town of Xoconoxtle, having driven down those mountains in 2003 with Adolfo & Ruben. This was the type location of P.potosiensis, which is a bogus name since these plants fit nicely into the continuum of taxonomic variation of P.moranensis. In 2003 we didn’t see any flowers, but this time I did find a single specimen with three beautiful dark purple flowers plus a developing bud.

            We arrived at San Luis Potosi city mid-afternoon and spent the rest of the day just wandering around the beautiful colonial-style city center and visiting its lovely churches. We then headed back to Guanajuato, stopping by another town called Dolores Hidalgo for dinner and for a little more touring around a colonial city center and its churches.

            Total for the weekend: about 1000km !

Fernando RIVADAVIA