Mexico 2018
In April of this year, we traveled to Oaxaca, Mexico, to continue an ongoing project with our colleague Rafael Torres (Universidad Nacional Autónoma de México), and Alejandra Vasco to catalogue the fern and lycophyte diversity of the Sierra Juárez mountains in Oaxaca, Mexico. Each year, for the past five years, we have spent about a week collecting ferns and lycophytes in forests owned by small Zapotec and Chinantec communities in the Sierra Juarez. Most of our activity has been along MEX 175, the interstate highway that runs from Oaxaca's Pacific coast to the Laguna de Alvarado on the Gulf coast in Veracruz. Heading out of Oaxaca City, this road climbs from the dry central valley, over the frozen summit of Cerro Pelón at 2950 meters elevation, and then descends into wet tropical forest towards the small city of Valle Nacional and eventually the larger city of Tuxtepec. This is the same terrain that was thoroughly botanized by John Mickel and others during the 1980s and 1990s in preparation for the Pteridophyte Flora of Oaxaca, however the region is extraordinarily rich in diversity and we continue to make new discoveries each trip. Through our work, we've documented around 500 species of ferns and lycophytes along this route, found numerous new state records, and described fern hybrids and species new to science. Specimens from these trips are disseminated to herbaria world-wide, and images of the live plants are posted online on a website we maintain, fernsoftheworld.com. On each trip, the support of the communities in which we work is central to our success; we meet with their leaders to obtain permission to work and rely on them for guides, lodging, and food. In turn, we do our best to share our knowledge of the local flora, and are working on developing species checklists and field guides for their communities.
On our most recent trip, Michael and I met up in Oaxaca City a day before Rafael was to make the eight-hour drive from Mexico City. While Rafael was en route, we tracked down collecting supplies (50 pounds of old newspaper, rubber boots, and grain sacks to collect into) at Oaxaca's open-air market and loaded up on our favorite local street foods: tlayudas, memelas, and quesadillas. After Rafael arrived, we left the city and headed north into the mountains, following up on a tip we received on our previous trip about the possibility of collecting in San Miguel Yotao, a Zapotec village of approximately 600 inhabitants about six hours northeast of Oaxaca City. We were principally interested in visiting this town because of its proximity to the llano verde, an important collecting locality visited by Henri Galeotti, Karl Hartweg, John Mickel, David Lorence, and other famous botanists over the past 175 years. It is the type locality for dozens of fern species including several taxa that have never been collected elsewhere. Plenty of people know where the llano is, but actually getting there is another story. With some careful planning it should be possible to get there and back in a single day, yet the combination of political tension between adjacent land owners, intentional and unintentional misinformation from locals, and general cartographic mishap have confounded us. Several years of scanning maps, reading now-digitized accounts of 19th century field trips, and long hikes in the surrounding woods had brought us close to the llano, but the rediscovery of what Hartweg described as a "green swampy space in the midst of the woods," along with its limestone outcrops and unusual ferns, has still eluded us. If we were to find the llano verde, a long hike from San Miguel Yotao looked to be our last good option.
After a long, slow drive from Oaxaca City that finished with a tense ascent of a muddy, cliff-hugging logging road, we arrived in San Miguel Yotao around 7pm. We asked around to see if the comisariado de tierra communales (village leader responsible for communal land, selected for a term of typically one or two years) was available for us to present ourselves and ask permission to work; we were told to return to the municipal building in an hour. We got dinner at a house where we had eaten while passing through two years before, and returned to the comisariado's office at the agreed time. As the school brass band worked their way through a wandering, free-for-all practice session in the adjacent room, we sat down with the community leaders and explained why we had come: to explore their forest, document the plant diversity, and make some herbarium collections. We would send a checklist of species and a guide to the local ferns once our work was completed. After twenty minutes of discussion centered on our qualifications and research objectives, the comisariado and his two colleagues conferred amongst themselves in Zapotec for a few moments and then gave us the bad news: because of a dispute over property boundaries with a neighboring community, we would only be able to collect along the road into town, not in the forest extending beyond their village toward the llano verde. The news was not altogether unexpected -- tensions about territory appear to be widespread in the Sierra Juárez, and we had heard the same story before at other villages that had withheld the privilege to collect on their land. This was discouraging news – would the llano verde elude us again? Facing the prospect of mediocre roadside collecting and sleeping on a concrete floor (it was already 9 pm), we got back in the truck and headed for the neighboring village of Santo Domingo Cacalotepec, which offered cabins for rent and (possibly) better fern hunting opportunities.
We arrived in Cacalotepec twenty minutes later, entering the village through an ancient narrow cobblestone street better suited for the resident burros than for our pickup truck. With some luck and directions from helpful children, we found our way to the center of town. After some searching, we were able to find someone to bring us to the cabins, which were situated in the forest just above the town. As our hosts prepared the cabin for us, we walked around the clearing to get a preview of what ferns might lie in the surrounding forest: Pleopeltis plebeia, Parablechnum falciforme, Sticherus underwoodianus, and Pteridium aquilinum var. feei were all abundant. After that brief survey of our surroundings, we settled in for the night around midnight. We would meet with the comisariado early the next morning.
When we arrived in town at 7:30 am, the comisariado, a pleasant but rather serious-looking man named Vicente Vicente, and his committee were already seated in their office. We exchanged pleasantries, took our seats in front of Vicente's desk, and started quite nearly the same conversation that we had the night before in San Miguel Yotao. Things seemed to get off to a poor start when Vicente informed us that we would have to wait until the town had its next monthly meeting before our proposed research could be discussed and voted upon. Sensing that our second rejection in less than a day was impending, we explained that we could only spend that week in the Sierra Juárez and could not wait for a meeting that was still three weeks away. The committee broke off into Zapotec, leaving us to wait in botanical purgatory for a few long minutes. They concluded, and to our surprise, Vicente had changed his mind: not only could we collect ferns on their property--we would be guided on an all-day hike into some of their best forest.
While our guide, Abdias Ruíz, prepared himself for our trip, we stopped by the home of a young woman named Claudia, who fed the occasional visitor in her kitchen. For the following four days, we would eat breakfast and dinner with Claudia--she and her playful two-year-old daughter Dani quickly became some of our favorite locals. Our breakfast, like most of our meals during this trip, was typical of rural communities in Oaxaca's Sierra Juárez : eggs, salsa, and black beans, served with giant platter-sized, freshly made corn tortillas and cafe de olla, coffee sweetened with piloncillo (unrefined cane sugar) and cinnamon. Claudia packed us tlayudas, an iconic Oaxacan dish that resembles a tortilla-based flatbread pizza, and we were ready for our day trip with Abdias.
Our hike started with a long, steady incline through some of the village's collectively owned coffee plantations before reaching a wet, breezy ridge at about 2200 meters elevation. In this cooler zone, ferns flourished: Blechnum appendiculatum, Elaphoglossum petiolatum and Lophosoria quadripinnata were especially abundant on the sides of the trail in this area. On the trunks of trees we spotted three common species of Pleopeltis: P. mexicana, P. plebeia, and P. rosei. In wetter areas, a small Selaginella (possibly S. sertata) formed extensive colonies on the sides of the trail. We continued on at a fast pace and decided to hold off on collecting until we returned down the same trail later that afternoon.
The trail eventually left the forested ridge and began a steep descent through a thicket of Pteridium arachnioideum and a particularly well-armed Rubus. We assumed the area was a grown-over field that had been cleared for grazing, but Abdias informed us that it had been forested until a few years ago, when a severe fire had burned everything to the ground. Looking around, we found some holdovers from before the fire, most notably Polypodium puberulum, a giant terrestrial polypod with, as its name suggests, densely short-hairy leaves. Further down the thicketed slope, we entered secondary forest dominated by large oaks and a sparse understory of Hedyosmum mexicanum and various Miconia species. Ferns were not abundant here, but we did find some nice drought-tolerant species growing along the trail, including Asplenium monanthes, Mildella fallax, Anemia phyllitidis, and Adiantum alan-smithii, a recently described maidenhair that previously was only known from the neighboring state of Chiapas. Several Pleopeltis species, including P. collinsii, P. rosei, and P. angustum var. stenolepis clung to the trunks and branches of oaks here, along with several elaphoglossums. We followed the trail downhill onto a ridge through open forest—the waterfall we were seeking was barely audible, far below us off the left side of the ridge. The papery fronds of Polypodium arcanum draped off the branches of oak trees around us; the narrow, undivided leaves of Elaphoglossum sartorii and Campyloneurum angustifolium arched out of crevices in the boulders that lined the trail. Further ahead, we encountered a dense colony of Blechnum appendiculatum, a common mid-elevation species, along with some plants of Blechnum polypodioides, a closely related species with somewhat narrower leaves that are tapered towards the base. Scattered amongst them were several plants that were intermediate in their leaf shape and cutting to the two aforementioned Blechnum species. These appeared to be the hybrid Blechnum appendiculatum × Blechnum polypodioides, which is known from elsewhere in Mexico and Central America, but has never been formally described.
As we approached the waterfall, we passed through a small thicket along a wet cliff face dotted with the peculiar lithophytic bromeliad Fosterella micrantha, whose broad leaves and loose growth form are reminiscent more of a lilioid monocot than of most Bromeliaceae. This species, which is distributed from central Mexico to El Salvador, is the only Fosterella species that can be found outside of South America (the genus is most diverse in Bolivia). In the shaded, humid habitat at the base of the cliff, we found several larger terrestrial ferns that were absent from the drier forest we had passed through earlier: Phanerophlebia remotispora, Tectaria mexicana, Campyloneurum tenuipes, Diplazium lonchophyllum, and Asplenium achilleifolium.
We ate lunch on a large boulder just out of the spray of the 30-meter-high waterfall before heading back on the same trail. Our hike back was slow and tiring, both because we were forced to climb the same steep slopes we had descended earlier in the day and because our bags were getting increasingly heavy with collected plants. Our slow pace did allow us to spot some exceptional species that we had missed on our first pass, including Phlegmariurus pithyoides and a giant plant of Dryopteris cinnamomea with leaves more than two meters long. We got back to town as the sun was setting, stopped at Claudia’s house for dinner, and then returned to our cabin to press the plants we had collected—about 100 numbers amongst the three of us.
When we arrived in town the following morning for breakfast, we found out that Abdias was already in the cafetales collecting coffee with most of the other town’s inhabitants. Without a guide for the day, we stayed close and collected around our cabin while attending to the material drying in our presses. In addition to weedy species like Christella dentata, Sticherus bifidus and Pleopeltis plebeia, we found some less common ferns, including Sceptridium schaffneri, Sticherus palmatus, and more Dryopteris cinnamomea, which was locally abundant on rocky slopes in the woods. A series of meandering trails through the woods led us to a wet, open clearing of about 100×50 meters with a large patch of tall herbs and shrubs in in the center. We soon realized that the swath of tall plants in the middle of the field was mostly comprised of Osmunda spectabilis (=Osmunda regalis ssp. spectabilis) and Osmundastrum cinnamomeum. Both species are widely distributed in the Americas from Canada to southern South America, but are uncommon throughout the tropical portion of their broad distributions. Floristics accounts suggest these species are particularly rare (or under-collected) in Oaxaca, with only a handful of collections of O. spectabilis and a single collection of O. cinnamomeum reported. Finding hundreds of these plants growing together was not only a pleasant surprise for us, but also helped improve our understanding of fern distributions in the state. A man who was tending to his cattle nearby told us that this wet field was the site of a prehistorical village and is known locally as the laguna encantada. Maybe those same royal ferns grew around that now-lost village hundreds of years ago?
On our third day in Santo Domingo Cacalotepec, we met again with Abdias early in the morning, and Claudia packed us another field lunch. Our plan was to hike far into the mountains west of town, toward a large natural spring known as el malacate. This spring is the principal source of water for the village in the dry village below, running through a 10-kilometer-long series of pipes and hoses through the mountains. We started off on a steep trail near our cabin, with the goal of reaching el malacate by lunchtime. Within fifteen minutes of following the village’s water pipeline uphill, it became apparent that the forest here was wetter and cooler than the one we had seen on our hike to the waterfall. Large terrestrial ferns were common here, including Lophosoria quadripinnata, Pteridium aquilinum var. feei, Dryopteris wallichiana, and the ever-present Sticherus bifidus. In open areas, the giant scrambling fronds of Diplopterygium bancroftii arched overhead. The trail continued climbing, and we started to encounter more high-elevation taxa; Polystichum hartwegii, Arachniodes denticulata, and Parablechnum falciforme were abundant along the trail here. We started to see epiphytes typical of cloud forests as well, such as Vittaria graminifolia, Polypodium subpetiolatum, and Asplenium auriculatum. Serpocaulon falcaria was the most abundant fern here, and formed large colonies on the ground and in trees via its long-creeping rhizomes. In areas where a small stream would bisect the trail, we would find others: the giants Marattia weinmanniifolia and Sphaeropteris horrida along with diminutive species like Elaphoglossum muscosum and Asplenium flabellulatum. Among the smaller taxa we encountered was Asplenium insolitum, a rare spleenwort endemic to southern Mexico that otherwise is only known from six collections, including one we had made two years earlier in the nearby town of Capulalpam de Méndez. With its twice-pinnate, lanceolate leaves this species looks similar to the widespread Asplenium adiantum-nigrum, but it most likely closely related to Asplenium solmsii, which is restricted to Guatemala and the neighboring state of Chiapas.
After about two hours of walking through this wet forest, the trail began to narrow and led us onto a series of ledges of a large cliff. Judging by the cooler air temperature and the changing flora, we estimated that we had attained an elevation of around 2500 meters at this point. With this increase in elevation, we began to find new ferns clinging to the cliff face and overhanging branches, including Jamesonia hirta, Moranopteris basiattenuata, and Elaphoglossum peltatum. The epiphytic lycophyte Phlegmariurus myrsinites was here too—this species is easy to identify because it is the only Mexican Phlegmariurus with strongly dimorphic fertile and sterile leaves. On shaded rock faces, we found several rare species; most notably a tiny epipetric Elaphoglossum, Dryopteris nubigena, and Ceradenia sacksii. The Ceradenia was described by one of us just last year, and was previously only known from Cerro Pelón, 25km to the northwest. In total we found eleven plants at the new site—a small number, but nonetheless an important range extension for this species. We didn’t realize the importance of the Elaphoglossum find until we tried keying the plant out in John Mickel and Alan Smith’s Pteridophytes of Mexico and found out it was Elaphoglossum leonardii, which was previously known only from the type collection. Unknown to us at the time, John Mickel had visited el malacate in 1970 as part of his studies on Oaxacan ferns and collected this peculiar Elaphoglossum, along with a haul of other interesting ferns. John described the plant as a new species in 1980 and named it for Steven W. Leonard, then-curator of the University of North Carolina’s herbarium and his collecting partner on that trip.
The ledge we were on soon flattened out and sloped down to the stream below us: we had arrived at el malacate. We ate our lunch on some boulders in the middle of the stream, and explored the surrounding rocky slopes for some more ferns. We found a few interesting species here, including Athyrium bourgaei, a narrow-leaved member of the Athyrium filix-femina complex that appears to be restricted to Mexico and northern Central America. Despite recent study on Athyrium at a global scale, the relationships of the species in the American tropics remain poorly understood.
Satisfied with our finds and mindful that a long hike back lay ahead of us, we decided not to push on further. The hike back was slow and tiring, but we did make some new finds. One of the most exciting was not a fern or lycophyte but a gymnosperm: Podocarpus guatemalensis. Though podocarp diversity is highest in the southern hemisphere, there are some species that make it as far north as Mexico. The plant we found was perhaps 10 meters tall, but this species is known to attain heights of more than 30 meters! Nearby we found another giant--Marattia weinmanniifolia, a common terrestrial fern in wet ravines in Oaxaca. This species has triangular leaves to nearly 3 meters long, and stands out in the forest because of its fleshy texture and blue-green color. With limited room in our collecting bags and no fertile leaves to be found, we left the Marattia behind and continued to the cabin. We arrived as the sun was setting, and returned to Claudia’s for a much-needed meal before we got to work pressing our specimens. Each of us had collected about 25 specimens with several duplicates, so we were busy pressing and labeling specimens late into the night. With our presses full and specimens drying slowly in the wet air of the mountains, we decided we would leave Santo Domingo Cacalotepec the following morning for Calpulalpam de Méndez, a town halfway to Oaxaca where we could finish processing our specimens.
The following morning, we went to town one last time to have breakfast and say goodbye to Claudia, Abdias, and Vicente Vicente. Rafael got Vicente’s contact information so we could send a species checklist, and we began the long journey towards Capulalpam. The winding dirt road leading out of Cacalotepec afforded us opportunities to spot some more ferns on the road banks, and we stopped several times to collect. Among our finds were Anemia pastinacaria, Adiantopsis radiata, Diplazium franconis, and several Pityrogramma, including the putative hybrid Pityrogramma calomelanos × Pityrogramma ebenea. The likely hybrid was found growing with P. calomelanos but clearly was not that species; it was intermediate to that species and the less finely divided P. ebenea. Additional morphological study and analysis of DNA sequence data are needed to confirm the identity of this plant, but it is a fun hypothesis!
We crossed the bridge over the Río Tanetze and eventually found the main road back towards the central valley. We reached Capulalpam late that afternoon and set up our loaded presses over the portable driers Rafael had brought. With some luck, our specimens would be herbarium-ready by morning, when Rafael was due to drive back to Mexico City. Our work complete, we settled over some tlayudas and beers at a restaurant just down the hill from our hotel. As we do at the close of each of our collecting trips, we started to discuss where we should go next year. We considered the Zoque forest in the tropical lowlands near the Chiapas border and Cerro Zempoaltepetl, Oaxaca’s highest peak, but agreed on a more familiar locality: perhaps the llano verde was worth another shot.