POSTCARD from Mexico N°15

(By Fernando Rivadavia, July 7 to 9, 2006) 

CPs IN GUERRERO

               Knowing that I’d be back in Mexico – supposedly for work! J – in July 2006, I wrote to my friend Ruben Resendiz in Mexico City and we began planning where we would go, which Pinguicula species we would seek. Our first objective turned out to be a rather ambitious one: find the elusive P.imitatrix, known from a single collection made in Guerrero state in 1939. P.imitatrix was named by Zamudio who thought it resembled P.heterophylla (an imitator of P.heterophylla, thus the name), although with larger pink-purple flowers (To be confirmed) . Location data for this species is rather vague and we spent several hours trying to find it using all our maps and web resources, including the amazing Google Earth. We found 2-3 likely spots in Guerrero and decided to explore the two closest ones.

               We headed out late on Friday July 7 and returned only late on Sunday the 9^th, driving a total of 1350km. We first headed south to Chilpancingo, then east to Tlatlauquitepec, then south towards Tlacuapa. Between the last two towns, we found a flowering population of P.orchidioides growing at 2470m on mossy north-facing banks by the roadside just as it went over a mountain pass. The surrounding vegetation was oak forest (or at least what was left of it, since there were many farms all around). The flowers were very uniform in shape and colored a dark purple-pink with a white stripe at the base of the lower lip. The flower scapes and calyx lobes were most often reddish. The narrow-leaved rosettes varied from light to dark-green in color, often reddish (especially on the undersides, most visible on the inwards-curled leaf edges near the apex). After several minutes of excitedly photographing the plants, I suddenly noticed the elongated stolons reaching several centimeters out from most plants in different directions! Many mature plants were nestled among dozens of immature plants, probably originated from stolons.

               Not far away, further north along this same road, we found a very interesting P.moranensis population growing on dry banks by the road at 2450m. The rosettes were rather small and reddish and the inflorescences were (surprisingly) nearly identical to those of P.orchidioides in both overall color and flower shape! Was this a case of convergent evolution to take advantage of the same pollinator? Or was this a case of hybridization between P.moranensis and P.orchidioides with subsequent character selection and fixation in the descendents (that is, a genetic chimaera with P.moranensis rosettes and P.orchidioides flowers)? I favor the second hypothesis, especially because there was something strange about the leaves other than the smaller size. They seemed narrower, less rounded than is usual for P.moranensis, suggesting it was in fact a hybrid.

               We ended up leaving this area without seeing anything that looked like P.imitatrix. It’s a pity we didn’t have more fuel and hadn’t done our homework properly. Later we realized that if we had continued driving further south we would have passed several known P.heterophylla sites. This left us with the thought that if this was the correct area where P.imitatrix was collected, maybe this species was actually a natural hybrid between P.heterophylla and P.orchidioides or P.moranensis…

Heading back west towards Chilpancingo, we found more P.moranensis near the town of Chilapa. These were relatively “normal” plants with typical purplish-pink flowers and large green to reddish leaves growing on north-facing banks along the road in humid soil at 1900m altitude. From Chilpancingo we drove south to Acapulco and then northwest to Atoyac, where we spent Saturday night.

               We left at dawn on Sunday, thinking we’d reach Chilpancingo in a few hours by an alternate route past Puerto del Gallo and maybe even still have time to visit Taxco and see flowering P.heterophylla, P.parvifolia, as well as their newly-discovered natural hybrid. HA! Little did we know that what was an asphalt road on all our maps was actually mostly dirt – more precisely around 150km of holes, mud & rocks, all the way from the coast to 3200m altitude and then back down to around 1500m on the other side of the mountains. A total of around 250km in ten hours of driving – tiresome even for me as a passenger, but certainly worth it!

               It took us several hours to see our first objective of the day: P.zecheri, which was found between 2250-2400m altitude in large numbers covering humid mossy banks (including with sphagnum) by the roadside, in an area of mostly pine forests. The rosettes were large and green in color, while the flowers varied in color from light-purple to pink, rarely darker purple. White and occasional darker purple streaks were common at the base of the petals around the throat. We even spotted a plant high up on a road bank with a very light lilac, nearly white flower. Petals were sometimes rounder or sometimes narrower, sometimes longer or sometimes shorter – variable as with most Pinguicula species. In fact, can P.zecheri be considered a good species? Ruben & I agreed that, considering the wide morphological variation observed in P.moranensis, having a larger flower is not sufficient to separate a species. Or else we'd have 20 different species emerging from this complex, all with very poorly defined borders. Zamudio himself wrote in his PhD thesis that there are no clear borders between P.moranensis and P.zecheri.

               As far as I know P.zecheri had never been photographed in the wild before and further up the road we were hoping to find another CP that apparently had never even been photographed nor introduced to cultivation: Utricularia petersoniae. This species was only known from a few collections along this road between 2900 and 3200m altitude. I knew from experience that Utricularia normally like more sunlight than Pinguicula, so we stopped to look at the first moss-covered rock next to a small waterfall as soon as we were above 2900m – and sure enough we found it! The leaves are small and rounded while the traps are relatively large for such small leaves. Unfortunately we found no flowers, but we did see a few very young flower scapes. Surprisingly, although the scapes were only about a centimeter high or less, a deep-pink embryo of a flower bud was clearly visible atop each.

The habitat of Utricularia petersoniae : a moss-covered rock next to a small waterfall. Photo : F.Rivadavia	Utricularia petersoniae growing among mosses. Photo : F.Rivadavia
Utricularia petersoniae growing among mosses. Easy to find without knowing the possible habitat of this Utricularia ? No chance to stay hidden with Fernando's experience. Photo : F.Rivadavia	Utricularia petersoniae with flower bud. Photo : F.Rivadavia
A photo of the flower ??? Unfortunately not yet...	Utricularia petersoniae a small delicate, annual lithophyte showing the traps. Photo : F.Rivadavia

               Before reaching asphalt, we found a population of P.moranensis growing on mossy banks along the road at around 1910m altitude. The flowers were not as large as those of P.zecheri/moranensis seen on the other side of the mountain, but were nonetheless very similar in color and shape and thus a possible member of the morphologic/genetic continuum between P.zecheri and P.moranensis. We also saw lots of cool mushrooms along the way, I’d forgotten that Mexico had so many large and colorful fungi!

               Unfortunately we were down on gasoline once again – not to mention tired to the bone from the long dirt road – and could not explore a side road to Tlacotepec where P.heterophylla have been found previously. So we returned to Mexico City without seeing P.imitatrix nor P.heterophylla, but it was certainly great to see U.petersoniae as well as flowering P.orchidioides and P.zecheri/moranensis.

Fernando Rivadavia.