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Guest blog post by David Skinner

I am a retired government bureaucrat who worked for 40 years as an administrator in state and federal taxation. I have absolutely no formal training in botany, but now I find myself as an active participant in a major taxonomic revision and a coauthor in the publication of 18 new species in a plant family called Costaceae. This is the story of how my gardening hobby turned into an avocation and led me to work with some of the premier botanists in the world. It is also the story of how I have met several other plant enthusiasts from countries throughout the tropics who have contributed so very much to our work. I write this story in the hopes of encouraging more professional scientists to incorporate the observations of such “citizen scientists” in their research, and to encourage these enthusiasts to more carefully document their observations and post their photos and notes to resources like Inaturalist.org.

My story started about 30 years ago when my wife gave me a rhizome of the white butterfly ginger (Hedychium coronarium) as a Christmas present. I became interested in gingers, species of the family Zingiberaceae, but soon my interests began to focus almost exclusively on the closely related “spiral gingers” in the family Costaceae. I loved the architecture of the plants with their spiral staircase of leaves leading up to a variety of shapes and colors of bracts and flowers. I started collecting any cultivated Costus plants I could find in nurseries or mail-order catalogues. Soon, I learned that only a few species can survive outdoors in the winter where I live, so built a greenhouse.

My serious interest in Costaceae began after I obtained a copy of the 1972 monograph of New World Costaceae by Dr. Paul Maas. It became my bible.

As I studied his descriptions of the species and applied his identification keys to the cultivated plants, I soon realized that many of the popular Costus species in cultivation had been incorrectly identified. I started doing presentations to garden clubs and posting to online groups. I developed a website called “Gingers ‘R’ Us.”

My “real job” had me traveling to Washington, DC periodically and I always tried to carve out time to visit Mike Bordelon at the Smithsonian Greenhouses in Suitland, Maryland. On one of these trips, I met Dr. Chelsea Specht, who was working at the Smithsonian Institution as a postdoctoral fellow.

She had written what I believe is the first molecular study in Costaceae in 2001.This opened up a whole new world of interest for me as I tried to understand these new-to-me terms, like “clades” and “phylogenetic relationships”. In this paper she introduced the new generic divisions of the family that were solidified five years later in a more complete phylogenetic study . Chelsea very patiently answered my novice questions about phylogenetic trees and how they relate to the taxonomy of the plants.

In 2005 I made my first trip to the New World tropics looking for Costus in its native habitat. On the Osa Peninsula of Costa Rica, I was incredibly lucky to meet Reinaldo Aguilar, the world-famous “para-taxonomist” who has studied the plants of the Osa for over 30 years. He is is self-taught like me and does not have a botanical degree, but has coauthored many scientific articles. He worked closely with the late Scott Mori of the New York Botanical Garden and was honored in a 2017 article in NYBG Science Talk.

That first trip to Costa Rica had me hooked. I fell in love with tropical forests and over the next few years made trips to several other Latin American countries as well as back to Costa Rica. Always, my focus was on Costus and the other members of its family.

Along the way, I met several “unsung heroes” in the plant world,  like Marco Jiménez Villata, whom I met in the town of Zamora in southern Ecuador. Marco specializes in orchids, but he is also a generalist and knows a lot about the plants of southern Ecuador. He (now retired) was a school administrator and had traveled to many remote villages in the province and was always on the lookout for interesting plants. I have traveled with Marco and his son Marco Jiménez León several other times and we have become good friends.

In 2015 we went to the type locality of the species Costus zamoranus and took the first photographs of this species. At that trip, Marco showed me an area of high elevation near the Podocarpus National Park, where I found an unusual-looking Costus that we are now describing as Costus oreophilus. He also showed me unexplored places where I found another new species, Costus convexus. I made sure we credited him with his role in the discovery and documentation of those new species in our publication in PhytoKeys.

I have also traveled several times in Panama and Ecuador with another very well known, but non-doctorate plant enthusiast – Carla Black. Carla is the president of the Heliconia Society International, an organization uniting enthusiasts (scientists and non-scientists) in the order Zingiberales.

In 2015 we searched for the critically endangered Costus vinosus. We found a few plants growing deep in the forest of the Chagres National Park along an old Spanish trail used to transport gold to the Atlantic coast. There is still a mystery regarding the true form of the flower of C. vinosus, and I am in touch with another Inaturalist observer who has found it (not in flower) in the mountains northeast of Panama City. He will let me know when he finds it in flower!

In 2019 Carla and I visited the “Willie Mazu” site in Panama to photograph and study the new species Costus callosus, and in Santa Fé de Veraguas, we looked for a species proposed by Dr. Maas that is now described as Costus alleniopsis.

My serious collaboration with Dr. Maas began in 2017, when I was preparing for a trip to Oaxaca in southern Mexico. He asked me to be on the lookout for  two species of Costus from that region that he had identified as new based solely on his examination of herbarium specimens, without any good data on the floral parts.

By that time, I was posting my Costus observations on Inaturalist.org and using that resource to look for interesting plants. I also used it to find plant people to contact for local information. For this Mexico trip I found a huge number of observations posted by Manuel Gutiérrez from Oaxaca City.

I found that he had extensive knowledge of the Chinantla region in the mountains east of Oaxaca City and had worked with the indigenous tribe there. Together, we explored the indigenous lands of Santa Cruz Tepetotutla.

We found many plants in flower of what Dr. Maas wanted to describe as Costus alticolus. We also found the species he planned to describe as Costus oaxacus, but I later found the same species in Guatemala, already described as Costus sepacuitensis.

Later I learned of the plans to prepare a complete revision to the taxonomy of the New World Costaceae. Together with Paul and Hiltje Maas, we spent several days at the Naturalis Herbarium in Leiden, comparing my photos against the hundreds of Costus herbarium specimens there. I had a long list of species that was curious about, and we were able to get through it and figure out what questions remained, even though we had not come up with all the answers.

It was soon apparent that there are major changes needed in the taxonomy and nomenclature of these plants, and that information from the field would be an essential supplement to the observations made from the herbarium specimens.

In 2016 I visited the type locality of Costus laevis in central Peru. I was surprised to find that the plants there are nothing at all like the Costus laevis of Central America, but match perfectly to the herbarium specimen that was deposited in Spain over 230 years ago. It was clear to me that the herbarium specimen designated as the type had been misinterpreted. I wrote an article explaining the problem – but I had no idea what the solution might be.

Dr. Maas agreed that there was a problem with that species that we eventually resolved. This resolution will be a part of the forthcoming revision of the New World Costaceae that is in preparation, nearing completion.

Another major problem involved the Costus guanaiensis complex. Paul and Hiltje, along with Chelsea, had visited the New York Botanical Garden Herbarium, where the holotype of that species is held, and realized that it had been misinterpreted due to the lack of a good flower description. What had been identified as Costus guanaiensis in the herbarium was actually a completely different species that Maas had planned to describe as a new species.

The entire C. guanaiensis complex needed name changes and redefinitions of species boundaries, ultimately resulting in the description of Costus gibbosus that is published in PhytoKeys. The resolution of the other members of that complex will be explained in the forthcoming revision. Over the next several years, Paul and I exchanged 1,626 emails (yes, I counted them – with the help of MS Outlook) pounding out the details of the changes needed in the taxonomy of New World Costaceae. In collaboration with him, I made many more field trips to resolve the remaining questions we had.

My extensive collaboration with Paul Maas has been one of the most rewarding experiences of my lifetime. He has taught me so much about the rules of nomenclature and the process of describing a new species. The one thing he could never teach me was his almost uncanny ability to look at a dried herbarium specimen and make a determination of the species. I suppose that only comes from experience as  he has examined over 11,000 specimens of Costaceae that will become our list of exxicatae when the full revision is published.

I should not fail to mention my time working with Dr. Thiago André. In 2014 I flew to Rio de Janeiro and then Thi and I, along with his academic advisor and another student, went to the state of Espirito Santo to look for the endangered species Chamaecostus cuspidatus. Thi has been our expert in that genus and has helped with the review of the new species published in PhytoKeys, Chamaecostus manausensis. In 2014 he was still finishing his doctorate and was in process of preparing a molecular phylogeny and morphological study of the species complex of Chamaecostus subsessilis.

Thi and I have stayed in close contact, and he came to Florida one year to visit in my home and see the Costaceae in my private garden, Le Jardín Ombragé. He is now a professor at the Universidade de Brasília.

Finally, I should discuss my collaboration with Eugenio Valderrama and the other members of the Specht Lab at Cornell University. In 2018 I went to Cornell to visit Eugenio and we discussed the sampling to be used in the molecular phylogeny that will be a very important part of the full revision when it is published.

At Cornell, Eugenio produced a novel baiting schema for extracting specific genes from across all Costus species and in 2020 published a paper. With further sampling, another paper was published in 2022 to reveal interesting data on a whole package of pollination-related characters, and how they show evidence of convergent evolution. Eugenio’s phylogenies very well support the new species we are publishing in PhytoKeys, and the full molecular phylogeny will be included in our full revision when it is published.

Just this past December I went to Colombia to attend the Heliconia Society Conference at Quindío, and Eugenio and I each made presentations there about our work with Costaceae. Then we traveled together to investigate several other interesting species of Costaceae, including the new species Costus antioquiensis, and a strange yellow bracted form of Costus comosus found in the species-rich area of San Juan de Arama in Meta.

How did I know to look there? An observer, a citizen scientist, had posted his records and photos on Inaturalist.org. I have my account set to filter all Costaceae and send me a daily email with all the new postings of the family, and this plant will now be appearing as a sample in a molecular phylogeny and as an observed species in a monograph.

I hope this blog article will provide some background and insight into what I think must be an unusual collaboration between a citizen scientist and the much more qualified lead authors of our PhytoKeys article describing eighteen new species in Costaceae. It has certainly been a rewarding experience for me, and I hope other plant enthusiasts will be encouraged to share their observations on forums like Inaturalist.org, providing detailed and accurate information and photos. At least for the one plant family I have some expertise in, I will continue to monitor and curate those observations on Inaturalist.

 To see all of my own field observations of Costaceae, including the new species we are describing in PhytoKeys, go to https://www.inaturalist.org/observations?user_id=selvadero.

References

André T, Specht CD, Salzman S, Palma-Silva C, Wendt T (2015) Evolution of species diversity in the genus Chamaecostus (Costaceae): Molecular phylogenetics and morphometric ap­proaches. Phytotaxa 204(4): 265-276. https://doi.org/10.11646/phytotaxa.204.4.3

Maas, P. J. M. (1972). Costoideae (Zingiberaceae). Flora Neotropica 8, 1–139. doi: 10.1093/aob/mch177

Maas PJM, Maas-van de Kamer H, André T, Skinner D, Valderrama E, Specht CD (2023) Eighteen new species of Neotropical Costaceae (Zingiberales). PhytoKeys 222: 75-127. https://doi.org/10.3897/phytokeys.222.87779

Salzman S, Driscoll HE, Renner T, André T, Shen S, Specht CD (2015) Spiraling into his­tory: A molecular phylogeny and investigation of biogeographic origins and flo­ral evolution for the genus Costus. Systematic Botany 40(1): 104–115. https://doi.org/10.1600/036364415X686404

Skinner D (2008) Costus of the Golfo Dulce Region. Heliconia Society Bulletin 14(4):1-6

Skinner D and Jiménez M (2015) Costus zamoranus: An endemic species to Zamora-Chinchipe Province in Southeastern Ecuador. Heliconia Society Bulletin 21(3):4-9

Skinner D (2016) Following Ruiz. Heliconia Society Bulletin 22(4): 7–14.

Skinner D and Black C. (2016) Search for the Mysterious Lost Plant (Costus vinosus). Heliconia Society Bulletin 22(3):1-3

Skinner D (2019) A Tale of Two Costus (Costus sepacuitensis) and Costus cupreifolius) Heliconia Society Bulletin 25(1):1-3

Specht CD, Kress WJ, Stevenson DW, DeSalle R (2001) A molecular phylogeny of Costa­ceae (Zingiberales). Molecular Phylogenetics and Evolution 21(3): 333–345. https://doi.org/10.1006/mpev.2001.1029

Specht CD, Stevenson DW (2006) A new phylogeny-based generic classification of Costaceae (Zingiberales). Taxon 55(1): 153–163. https://doi.org/10.2307/25065537

Valderrama E, Sass C, Pinilla-Vargas M, Skinner D, Maas PJM, Maas-van de Kamer H, Landis JB, Guan CJ, AlmeidaA., Specht CD (2020) Unraveling the spiraling radiation: A phylogenomic anal­ysis of neotropical Costus L. Frontiers in Plant Science 11: 1195. https://doi.org/10.3389/fpls.2020.01195

Valderrama E, Landis JB, Skinner D, Maas PJM, Maas-van de Kamer H, Sass C, Pinilla-Vargas M, Guan CJ, Phillips R, Almeida A, Specht CD (2022) The genetic mechanisms underlying the convergent evolution of pollination syndromes in the Neotropical radiation of Costus L.Frontiers in Plant Science 13: https://doi.org/10.3389/fpls.2022.874322

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