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The Irreplaceable Role of Nature in Scientific Discovery

There is no greater high for a scientist than discovery. It’s a cocktail of adrenalin and joy that imbues a pure sense of euphoria. Yet because it’s natural, there’s no hangover on the downside. In fact, it can last and last. Even recollections of long-past discoveries can evoke these sensations. And like many drugs, it’s often in short supply and addictive. Consequently, the brains of scientists crave it, so we are always on the lookout for opportunities to achieve our next dopamine-induced fix.

For field biologists, there’s no place more alluring than nature. For it’s in the field where we feel simultaneously at ease yet invigorated, quieted yet energized. Those sensations often come from a deep appreciation—some call it love—of the organisms we study. For many herpetologists, that passion is traceable to an early childhood experience. I grew up in Southern California and mine came in kindergarten. One day, two older boys came to our class for show and tell and passed around a jar containing several Pacific Chorus Frogs (Pseudacris regilla). I was rapt, and especially enamored with a bright green male. Yet, despite staying late to beg to take them home, my teacher patiently explained she had no authority to give them to me. So a few days later, I convinced my father to take me to a drainage canal near our home to search for my own. That evening, we captured about a dozen adult Western Toads (Anaxyrus boreas). I fondly remember their unique body patterns (so distinct, I named each one), the endearing bleating of the males when grasped under their armpits, and their mossy–earthen aroma. My fate was sealed. Although I had been interested in science and nature since I was a toddler, these formative experiences with amphibians proved decisive: I would become a herpetologist.

I spent most of my youth immersed in herpetological pursuits. By the time I was an early teen, I had countless pet frogs, salamanders, turtles, lizards, and snakes (both local and exotic) and raised my own mice and rats to feed them. (Major shout out to my mom for enduring the many escapees and rodent-cicles in our freezer!) In junior high, I started attending monthly meetings of the San Diego Herpetological Society (SDHS). There, I learned about the diverse pursuits of herpetologists: anatomy, behavior, ecology, biogeography, systematics, and so on (this was prior to the takeover of most amateur herp societies by those primarily interested in breeding herps for profit). I began collecting herp books and taking notes and photographs on field excursions. I also met professional herpetologists and others who shared and encouraged my interests, including several boys my age who also aspired to be herpetologists. For several years, I hiked nearly every weekend along the river valleys, mountains, and deserts of Southern California with my SDHS pals in search of herps. Those experiences strengthened my love of nature, reinforced the knowledge acquired from field guides, and sharpened my field-herping skills. In high school, I shared my live animals and growing knowledge of herps with various groups and schools and worked in local pet stores as the herp specialist. I supported myself though college, in part, by selling lizards and snakes I bred in captivity. Immediately upon transferring from community college to San Diego State University as a college sophomore (and blissfully unaware of prerequisites), I enrolled in Dr. Richard Etheridge’s senior-level herpetology class. That was the single-most important step I made toward a career in herpetology. Not so much for what I learned (although there was plenty of knowledge acquired in that rigorous course) but even more for the lifelong network of colleagues and friends established through Richard.

Indeed, it was Richard, who about seven years later, invited me to accompany him on a trip to Argentina and introduced me to the wonders of its herpetofauna and the warm and gifted herpetologists at the Fundación Miguel Lillo (FML) at the Universidad Nacional de Tucumán. It was the austral summer of 1994–1995. I had just started the doctoral program at Colorado State University and had plans to study the evolution of herbivory in reptiles. My investigation would focus on a then poorly studied group of lizards in the genera Liolaemus and Phymaturus from the southern cone of South America. These are small to moderately sized lizards (lacking fitting common names) that occupy a diversity of ecological niches from Andean Peru to nearly the southern tip of the continent and from sea level to above 5000 m. Liolaemus was a fairly large group, with about 150 species recognized at the time (nearly double that currently); likewise, Phymaturus had only 10 species (now 50).

I learned more than about herps on that trip. So much more. It was my first full immersion in a culture outside the United States. (Not counting high school jaunts for surfing, tacos, and beer in northern Baja California.) Fortunately, we had knowledgeable and patient hosts at the Instituto de Herpetología at the FML, including (then) graduate students Virginia Abdala, Félix Cruz, Monique Halloy, Fernando Lobo, Adriana Manzano, and Silvia Moro; senior herpetologists Esteban Lavilla, Ricardo Montero, and Gustavo Scrocchi; and the world-renowned herpetologist, Raymond Laurent, who served as the institute director. In January 1995, Richard, Esteban, Fernando, local undergraduate Juan Carlos Moreta, and I set out in a well-aged field truck, primarily in search of Liolaemus. Our trip included herping dozens of localities in seven northwestern provinces, primarily along the Andean cordillera. I was surprised by how similar the climate and many of the habitats were to those in the southwest United States. Even numerous plant genera were shared between the two regions. I found the many instances of convergence between species of Argentinian herps and those from Southern California to be remarkable. Although memorable on many levels—particularly the new herps we encountered (not to mention the 13 flat tires we endured)—the grander herpetological discoveries would come a few years later.

Back in Tucumán, in the course of dissecting lizard guts to determine the diets of Liolaemus in the FML collection, I often encountered females with either shelled eggs or developing embryos. After recording the reproductive modes of a few dozen species, followed by a cursory literature review, my interests detoured from herbivory to an investigation of the evolution of viviparity within the group. When I shared my new plans with Fernando, he told me about Martha Patricia Ramírez-Pinilla, a recently graduated doctoral student who had studied the reproductive cycles of several species of Liolaemus, including some in the L. alticolor group. She found that this group included both oviparous and viviparous species, but remarkably, one species (L. alticolor at the time) was reproductively bimodal—a species within which some females produce eggs and others give birth to live young. Martha had even identified a reproductively bimodal population of this species. This was intriguing because reproductive bimodality is very rare in reptiles, and at the time, there weren’t any known reproductively bimodal populations of squamate reptiles (lizards or snakes).

So, in the early austral summer (November) of 1996, Fernando and I set out to study this bimodal population, which occurred just a couple hour’s drive from the FML. Prior to my arrival, Fernando had reexamined Martha’s reproductively bimodal specimens with the keen eye of a taxonomist and had identified morphological differences between the oviparous and viviparous morphs. Notably, the viviparous morphs had two dorsal fields of black-and-white paravertebral markings bordered by narrow golden-yellow stripes and speckled bellies (labeled A in the following figure), whereas the oviparous morph lacked paravertebral markings, had less distinctly defined dorsal stripes of dark gray and light brown, and lacked belly speckling (B). They were so different, in fact, we strongly suspected they were different species (both were also distinct from the true L. alticolor, which was originally described from Peru). To test our hypothesis, we set out to collect lizards along the road (Ruta Provincial 307) where FML’s enduring and indispensable herp collector, Omar Pagaburo (known to all as Pagaburo), captured the specimens that Martha had studied. Not long after we started collecting along that 16-km stretch of road (km markers 82 to 98), we discovered what Martha could not have realized from her laboratory examination of preserved specimens: the two morphs lived in distinct habitats. We found the viviparous morph exclusively in a monoculture of golden bunchgrass (Festuca) above 3000 m in elevation (C), and we found only the oviparous morph about 12 km northwest and 200 m lower in elevation, where the vegetation was dominated by spindly, dark-gray branched shrubs (Parastrephia; D). Both morphs were always encountered in the dominant vegetation of their respective regions, within which they were remarkably cryptic and nearly impossible to detect unless they moved. Ultimately, we encountered the ecotone (at km marker 88) where the two plant species co-occurred in roughly equal densities (E). Here, as might be expected, the two lizard morphs were also found in sympatry yet maintained their strict microhabitat preferences: viviparous form in the bunchgrass, oviparous form in the shrubs.

Needless to say, we were elated to have discovered a few more pieces of the puzzle, but the full picture had yet to emerge. First, the reproductively bimodal population collected by Pagaburo and documented by Martha was from km marker 95, not 88. Indeed, at km marker 95, we encountered only the oviparous morph, doubtless because there was no bunchgrass along the road at that site. Second, we couldn’t explain what was driving the dramatic vegetation ecotone over such a small area and narrow elevational range.

The next morning, we arrived early to the locality of the viviparous morph. It had been cold the previous night and the humid valley some 21 km to the southeast (Tafí del Valle) was blanketed in dense fog. The Festuca growing along the hillsides was also covered in fog and dew. As we drove northwest along the road toward km marker 88, we realized that the fog penetrated just up to the ecotone, where it did not dissipate until early afternoon. When we returned to Tucumán, meteorological and reproductive data in Martha’s dissertation confirmed that the air temperatures average about 10 °C cooler over the range of the viviparous morph relative to the oviparous morph during the peak of their respective reproductive seasons, in support of the long-held hypothesis that cold climates drive the evolution of viviparity in squamate reptiles. Furthermore, Pagaburo confirmed that he had collected both reproductive morphs of lizards at km marker 95 by first capturing the oviparous forms along the road and later ascending the adjacent hills, which did have Festuca, to collect the viviparous forms.

The puzzle pieces finally assembled into a complete image. Fernando and I wrote the first of what would be numerous papers penned by us and his future students, ultimately leading to the recognition of nine cryptic species, all of which were formerly considered geographic variants of L. alticolor. In that first paper (Lobo and Espinoza 1999) we also described our integrated approach to discovering the identities and ecologies of the two lizard morphs, which we named in honor of Pagaburo, L. pagaburoi (viviparous form; A), and Martha, L. ramirezae (oviparous form; B). In doing so, our investigation affirmed a widely held credo of field biologists: There is no better way to learn about the intricate lives of organisms than by studying them in nature.