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Dung beetles in high mountain landscapes of Oaxaca

By Matthias Rös, Alfonsina Arriaga-Jimenez, Bert Kohlmann

 

Dung beetles (Scarabaeidae) belong, besides ants and butterflies, to the best-studied insect groups in tropical ecosystems. Three subfamilies are considered as true dung beetles: Scarabaeinae, Geotrupinae, and Aphodiinae. There are about 10,000 species of dung beetles around the world known to science, although that number is still rising; montane areas in the tropics are exceedingly rich in species, and new species are regularly discovered. 

High mountain ecosystems in the American tropics have been less studied than the diversity-rich lowland rain forests, which have received greater attention and efforts for conservation purposes. Nevertheless, the significance of temperate ecosystems within the tropics may have been underestimated regarding their importance to explain species distribution patterns in various biodiversity hotspots of the Earth. Mexico, and particularly the state of Oaxaca, will serve us here as an example to explain why. 

Oaxaca is one of the most (if not the most) biodiverse states of Mexico. One reason is the rugged orography, shaped by different geological events, which, accompanied by changing climate, separated and connected animal and plant populations several times, and so turned Oaxaca into a laboratory of species evolution. Oaxaca is situated in the southeast of Mexico and is dominated by three major montane areas (Sierra Norte, Sierra Sur, Mixteca Shield). Eighteen percent of the state has an elevation higher than 2000 m, and around four percent is situated between 2500m and 3700m. 

Typical land-use patterns in Oaxacan mountains. Forest dominated landscapes with traditional milpa system (corn, beans, squash). El Rosario Temextitlan, Chinantla, Sierra Norte de Oaxaca at elevations between 2000 and 2700 m. Photo by Matthias Rös.

In the last two years, we have collected and described new dung beetle species from Oaxaca. All of them were not collected in pristine or remote places, but in mountain forests close to the capital city of Oaxaca. Whereas the state has few large reserves, Oaxaca is known for its high number of community-conserved areas (CCA), and the new species were collected in the CCA La Mesita, in San Pablo Etla, a 3000 ha community-managed forest at altitudes between 1800 and 3200 m, which provides firewood, clean water to the entire watershed, and offers small scale sustainable tourism. In Oaxaca, at lower altitudes, there exists an oak forest, with mostly small trees that lose all their leaves during the dry season, reminiscent of the familiar chaparral vegetation. In Oaxaca, this oak forest is a typical vegetation type of piedmont, mostly surrounding the Central Valley. We named Canthidium quercetorum after this forest type, only known at present from La Mesita. Onthophagus etlaensis, named after the Nahuatl word for bean-fields, sampled by us in the same reserve, had already been collected in the 1970s but was erroneously identified because of its closeness to another, more common species. This is a very typical pattern found in Oaxaca: there abound many endemic sister species of common and more widespread taxa, and they have a small distribution range in the mountains of Oaxaca, which indicates their speciation in situ.  Finally, Phanaeus dionysius, a veritable jewel of a beetle, was also found in this CCA.

Onthophagus etlaensis (left) and Phanaeus dionysius (right), two dung beetle species of the subfamily Scarabaeinae, described from the community-conserved area of La Mesita, San Pablo Etla, near the city of Oaxaca.

Oaxaca belongs to the Mexican Transition Zone, a region ranging between the southern USA down to the Nicaraguan lakes. Its outstanding characteristic is the overlap of Nearctic and Neotropical species distributed here, the former more often at higher elevations with the latter at lower elevations. Both Neotropic and Nearctic faunas have generated a high number of endemic species in Mexican mountains. 

Besides its rich biodiversity, Oaxaca is also one of the most understudied states in Mexico, and regarding plant or animal groups we have only little information. This  might explain why we also found, in addition to the recently described species, some species which were last collected 45 years ago. 

This map shows Oaxaca as depicted by a 3D Digital Elevation Model. Black dots represent sampling sites for Onthophagus anthracinus, the red dot Canthidium quercetorum, and the blue dot Phanaeus dionysius.

AAJ started to work on dung beetle diversity at high-altitude mountains ten years ago when she collected insect material from the alpine prairies of the Trans-Mexican Volcanic Belt (TMVB). For her Ph.D. project, she moved up to high elevations between 2500 and 3500 at four volcanos. One of the most interesting results was that a high variability of diversity patterns between the volcanoes existed. We also found an unexpectedly high diversity, coupled with low abundances and detection probabilities, that in three years of sampling, abundances were still lower than what you collect in one rainy season in a cloud forest. Our next step shall be to compare diversity patterns between the mountains of Oaxaca and the Trans-Mexican Volcanic Belt. Bert Kohlmann has studied for almost three decades the dung beetle communities in the high altitude-mountains of Costa Rica and Mexico, where interesting evolutionary phenomena have been discovered associated with the Last Glacial Maximum. Nevertheless, to detect and understand processes which determine diversity patterns at high altitude mountains in the tropics, more attention, longer sampling periods, and deeper taxonomic knowledge of the species and their phylogenetic relationships covering the whole Neotropics is needed. Matthias Rös studies diversity patterns in natural and human-modified landscapes, looking for biodiversity-friendly land-use patterns. Oaxaca seems to have plenty of these biodiversity-friendly land-use patterns in its mountain landscapes, despite or even because of a human-induced modification history dating millennia. Our research of describing new species is the baseline for further investigations. How can we protect the outstanding biodiversity under scenarios of climate change and land-use intensification? Oaxaca might suggest very interesting answers to many questions related to this topic. Oaxaca and its mountains still have many secrets to unfold, and we want to explore and reveal them.

 

Arriaga-Jiménez, A., Escobar-Hernández, F., Rös, M., & Kohlmann, B. (2020). The establishment of the Onthophagus anthracinus (Coleoptera: Scarabaeidae) species complex and the description of a new species. The Canadian Entomologist, 152:1-17. https://doi:10.4039/tce.2019.62. (Paper made available to read for FREE until March 24, 2020 in cooperation with Cambridge University Press)

 

Related research to dung beetles in high mountains:

Kohlmann B., Arriaga-Jiménez, A., Rös, M. 2018. Dung beetle vicariant speciation in the mountains of Oaxaca, Mexico, with a description of a new species of Phanaeus (Coleoptera, Geotrupidae, Scarabaeidae). ZooKeys743:67-93. https://zookeys.pensoft.net/articles.php?id=23029

Arriaga-Jiménez, A., Rös, M. & Halffter.G. 2018. High variability of dung beetle diversity patterns at four mountains of the trans-Mexican volcanic belt. PeerJ 6:e4468. https://doi.org/10.7717/peerj.4468

Kohlmann, B., Arriaga-Jimenez, A., & Rös, M. 2018. An unusual new species of Canthidium (Coleoptera: Scarabaeidae: Scarabaeinae) from Oaxaca, Mexico. Zootaxa 4378 (2): 273–278. https://doi.org/10.11646/zootaxa.4378.2.7

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When Adventure Comes Calling ~ Foreign Perspectives

By Paul Manning, Post-doctoral Researcher, Dalhousie University

Sometimes when you’re least expecting it you can find yourself presented with the adventure of a lifetime. This recently was the case for me. My adventure took me to the United Kingdom, from September 2013 to August 2016, where I completed my DPhil in Zoology at the University of Oxford.

I didn’t have any long-standing plan to attend the University of Oxford. While finishing my undergraduate degree at the Faculty of Agriculture at Dalhousie University (Truro, Nova Scotia), I decided to apply for a Rhodes scholarship on a bit of a whim. The application was daunting but nonetheless, I managed to put something together and received word that I was a regional finalist. Roughly a week before my final interview, I scanned the University of Oxford – Department of Zoology website and came across the name Owen Lewis. I read through a couple of his papers and sent him a quick e-mail explaining my situation. I received a near-immediate response. Owen enthusiastically wished me the best of luck with my interview and agreed to act as my supervisor should I receive funding. Through a combination of luck, privilege and merit I found myself presented with the opportunity to study at the University of Oxford. I submitted my application to the university a week later. Opting to spend three years being supervised by a stranger based on a single e-mail exchange is not something I would advise to others, but it is exactly what I chose to do. Fortunately, I landed in an incredibly supportive and inclusive research group – and Owen’s first exchange perfectly predicted his supervisory style: helpful, available, and incredibly kind.  

I fell in immediate love with the city of Oxford soon after my arrival. The first thing you might notice about the city is the architecture: medieval walls, ivory towers, and ancient gates seem to appear around every corner. The second thing you might notice is all the bikes – they easily outnumber the cars on the road. The squealing of rusty brakes and pinging of bells is the soundtrack of a morning commute. The third thing you might notice is the gigantic slugs and snails that appear at night – that was my experience at least.

Looking West down High Street Oxford from the top of the Magdalen Tower (L). A delightful garden snail (Limax flavus) that would greet me at the entrance to my flat (M). A delightfully plump slug (Cornu aspersum) with a pound coin for scale (R).

My DPhil research explored the importance of insect biodiversity in perturbed environments using dung beetles as a model system. I did a fair amount of my fieldwork in Southwest Wales, where I was introduced to my co-supervisor Sarah Beynon. Sarah had recently completed her DPhil with Owen as a supervisor and was in the process of setting up “Dr Beynon’s Bug Farm”, which is probably best described as a mixture between a research centre, tropical insect zoo, and working farm. It also is home to Grub Kitchen, UK’s first restaurant with edible insects on the menu.  I spent my first summer living and researching on-site, while the start-up was in its initial stages. It’s a beautiful place – in the early spring the farm is blanketed with yellow iris, red campion, and various orchid species. It was a short bike ride to the coast which I frequented to enjoy steep paths, white sands, and impressive waves.

One of the things that I truly loved about the United Kingdom was the widespread appreciation and knowledge of natural history. The entomology and ecology circles that I ran in certainly would have amplified this signal, but it seemed to run deep in society-at-large. When a server interrupts your book-in-face breakfast to offer her insights about myxomatosis, a viral disease of rabbits, you might just be in the United Kingdom.

A late afternoon rainbow spotted at the Bug Farm (L). Some red campion (Silene dioica) blooming near St. David’s, Pembrokeshire UK (M). Blue skies and strong current on the Ramsey Sound (R).

Some of my favourite memories from my time abroad were natural history outings. Richard Comont, a DPhil student in our research group took me out in the winter of 2014 to see the impressive minotaur dung beetle. We arrived at a local park in the pitch black of night, armed with a couple flashlights. Richard, who bears a certain resemblance to Hagrid (the brawny groundskeeper for Hogwarts School of Witchcraft & Wizardry), also carried a pooter, umbrella, and beating stick. We found the minotaur beetles, they were certainly impressive, but perhaps more memorable was a vivid image of a grinning Richard whaling on a bit of gorse with a broom stick, in the pitch black of the woods.

Another dung beetle memory involves Darren Mann, Head of the Life Collections at the Oxford University Museum of Natural History. Darren invited me out for a day of dung beetle recording as part of a Scarabaeoidea recording effort known charmingly as Team DUMP. We left at six in the morning, drove two-and-a-half hours to rural Wales, and sifted through animal dung on sand dunes until it was so dark that we couldn’t see our hands in front of us. Darren found one species he expected was locally extinct – upon realizing what he found, he gave a fantastic howl of excitement. I’d expect there are few people who are more enthusiastic and knowledgeable about insects than is Darren Mann. If you ever get the chance, make sure to ask him about cockroaches sometime.

A third dung beetle memory is a day I spent collecting with Sarah and her partner Andy. We were getting ready to run a few experiments, and set-up a dung beetle demonstration at a tradeshow. Of course, the powers that be sent along torrential rain. To this day, I don’t think there is a more miserable feeling than kneeling in prickly shrubs, soaked to the bone, sifting through sheep dung. Nonetheless, that’s what we did for hours and hours. Upon returning to the vehicle, I cleaned up and towelled off only to have a bird defecate directly onto my head and shoulder. There couldn’t have been a more fitting end to the day.

An impressive Minotaur beetle (Typhaeus typhoeus) in Shotover Country Park, Oxfordshire (L). A vial of dung beetles containing 104 Onthophagus joannae removed from a single pile of dog dung (Photo by Darren Mann) (M). A collection of beautiful Geotrupid beetles found on Ramsey Island (St. David’s, Pembrokeshire) (R).

While my experience in Oxford was overwhelmingly positive, it did not come without its challenges. The biggest challenge I encountered was dealing with low points caused by an all-encompassing imposter syndrome. The ease and speed at which my colleagues could process and synthesize information was nothing short of intimidating.  Meanwhile, I had trouble getting my first few experiments off the ground; while simultaneously everyone around me seemed to be successfully completing ground-breaking research. I felt slow, unaccomplished, and lazy.  I tried to compensate by putting in additional time: arriving earlier, staying later, and working on weekends – but this just left me feeling burnt-out. Plenty of exercise, structuring my work days, limiting social media, and hours of conversation with my partner, friends, family, colleagues, and supervisors helped me get back on my feet.

I’ve been home in Canada since the summer of 2016, working as a post-doc and a sessional lecturer. I think often and fondly about my time spent abroad in the United Kingdom and would highly recommend it as a study destination. While competitive, there are many different funding sources that Canadian students can access, including the Commonwealth Scholarships, NSERC – Michael Smith Foreign Supplement, Rhodes Scholarships, as well as numerous other international scholarships offered at the institutional level. Living in a foreign country provides you with a fresh outlook and opens your world to a range of new experiences, ideas, and perspectives. If international study is compatible with your other commitments, mull it over a little, and think about giving it a shot – becoming an international student might be just the adventure you’ve been looking for.

Are you a Canadian resident spending time abroad to conduct entomological research, or are you coming to Canada for the opportunity to study? If you’d like to share your story and experiences as part of the Foreign Perspectives series, please get in touch with us by email.