Hhmi Lizard Evolution Virtual Lab Graph

[Kenneth Melniczek]

TheCaribbean is home to about 150 species of anole lizards. In this lab, students investigate how so many species of anoles evolved. The lab includes four modules that cover different concepts in evolutionary biology, including adaptation, convergent evolution, phylogenetic analysis, reproductive isolation, and speciation. In each module, students engage in key science practices, including taking measurements to collect data, constructing and interpreting graphs, and performing statistical analyses.

These days I am towards the other end of the student-teacher continuum and I make a point of not teaching from a textbook. First, they are WAY too expensive for students. Second, they are out of date by the time they are published. Third, if classic works are covered (like those on anoles), the format of a textbook makes even the most exciting example remote and dull. My approach has always been to go directly to the source. And anoles offer such a rich collection of content for educators.

Previous analysis of the scapulocoracoid in isolation revealed that its shape differs between Anolis habitat specialists, and resembles a particularly dorsoventrally tall shape in twig anoles (Tinius et al. 2020). The other ecomorph groups (trunk-ground, trunk-crown, and crown-giant) show obvious tendencies towards a particular structural organization, but in none of these does the scapulocoracoid resemble a truly characteristic shape.

HHMI produced several fantastic videos and learning modules perfect for learning about anoles, ecology, and evolution in the classroom and at home! Each of the activities also comes with handy educator materials to make sure your newly homeschooled students gets the most out of these resources.

In another excellent study exploring the effects of anthropogenic activity on evolution in anoles, Postdoctoral Fellow Claire Dufour is investigating how the recent introduction of Anolis cristatellus from Puerto Rico to the island of Dominica may be driving changes in the display behavior of Anolis oculatus, a Dominica native. Specifically, Dufour is asking whether interactions between the A. cristatellus and A. oculatus are consistent with patterns of Agonistic Character Displacement, in which interference competition between the newly sympatric species results in shifts in traits affecting the rate, intensity, and outcome of interspecific aggression.

To begin, Dufour and colleagues constructed a pair of robots that mimicked the typical look and display behavior of a male A. oculatus and A. cristatellus. She then traveled across Dominica and presented over 130 wild male A. oculatus with one of the two robots, and recorded the display behavior exhibited in response. Beyond measuring the duration of the response display, Dufour also tracked the proportion of time spent by the A. oculatus engaging in any of nine specific display behaviors, such as dewlap extensions, push ups, nuchal crest presentations, and others. By repeating this experiment among populations of A. oculatus existing sympatrically with A. cristatellus, as well as populations not yet invaded by A. cristatellus, Dufour was then able to ask whether variation in display time or composition among the native anoles could be attributed to the presence of A. cristatellus. Indeed, this turned out to be the case.

Anolis oculatus living in allopatry from the introduced A. cristatellus were found to engage in longer display bouts when presented with the conspecific robot, and shorter display bouts when presented with the unfamiliar A. cristatellus robot. Alternatively, A. oculatus occupying habitats already intruded by the A. cristatellus increased the duration of time spent displaying, regardless of which robot was presented. In addition, A. oculatus were also found to alter the behavioral composition of their displays when occupying habitats shared by the introduced A. cristatellus.

Dufour and colleagues capitalized on a rare opportunity to document the very early stages of a species invasion, and in turn improve our understanding of how human-mediated species introductions can promote evolutionary change. As changes in behavior are often the first response to novel competition, these results are consistent with the criteria of Agonistic Character Displacement, and support the claim that the introduction of crested anoles in Dominica has indeed driven a shift in the behavior of native anole communities. While the consequences of these shifts on the outcome of interspecific competition are still unclear, it will be interesting to see how differences in display behavior develop over time, and further, whether these initial changes in display behavior could lead to additional shifts in behavior or morphology among these newly interacting species.

Human activity is well recognized as having evolutionary consequences, and studies on the prolific Anolis genus continue to show us just how adaptable these lizards can be. Dr. Kristin Winchell, a Postdoctoral Research Associate at Washington University in St. Louis, MO, is investigating the relationship between human activity and evolution in Puerto Rican crested anoles, with a current focus on how selection across urban habitats might be driving changes in morphology and behavior among the lizards.

In an elegantly designed study, Winchell and colleagues collected over 120 male crested anoles (Anolis cristatellus) from forests and urban areas across the island. The team then assessed the ability of these anoles to perform a series of tasks representing normal daily activities, such as sprinting and clinging. By comparing anole performance on natural substrates like wood to their performance on more urban substrates such as concrete and metal, the team determined that the lizards consistently performed better on natural substrates, yet decreased their velocity when perches were inclined. Specifically, the crested anoles sprinted at less then half of their maximum speed on painted concrete, up to 32% slower on metal compared to wood bark tracks, and as much as 34% slower when surfaces were steeply inclined.

PhD candidate, Abby Beatty, from Auburn University presented a poster entitled Integrating research into the classroom: causal effects of IGF1 and IGF2 on growth in the brown anole. The poster focused on an enhanced method of teaching science, particularly labs. The program, called C.U.R.E (Course-based Undergraduate Research Experience), allows students to experience teaching labs in a way that is more authentic and typical of the research experiences of graduate students. In most science labs, students are provided with different protocols and methods as well as a predetermined set of goals and results that explains how the experiment should turn out. The teaching method Abby proposed gives students the opportunity to learn from their failed attempts, before receiving the correct answers. Here we can draw a parallel with the approach used by the chemistry tutor.

Specifically, the first semester class cloned and expressed IGF1 and IGF2 (insulin-like growth factors) using a bacterial vector. Similarly, the second semester class cloned IGFBP2. Abby then used these proteins to optimize methods for studying the growth rate of eggs and hatchling brown anoles. Hatchlings were monitored for 10 weeks following an injection with either IGF1, IGF2, or vehicle (NaCl + 15% Gelatin). Two trials were performed on the hatchlings and one on the eggs. In the first hatchling trial, IGF1 and IGF2 treatments had significantly higher death rates than control groups, but there was no association with body size. In the second trial, which used refined and updated methods, there was no significant effect on survival or body size, when compared to control groups. Finally, egg treatment did not correlate with survival or body size.

As the class completed each step in this process, they reviewed their work and if their methods were unsuccessful, discussed a better approach. Following completion of the course, the students received a post-survey assessing the same skills and knowledge as the pre-survey.

Abby found the class gained significantly in these skills, particularly receiving higher survey scores in the areas of creativity and understanding. She also found that the average score on the knowledge assessment was higher in the classes post-assessment survey than in the pre-assessment, indicating that the students may be gaining from this method of teaching. Control surveys from a class taught using a typical lab curriculum are not available, but there are plans to include this over the course of coming school semester.

These data, while still preliminary, highlight the benefit of implementing this kind of teaching strategy. When students are able to explore the process of asking and answering questions they generally become more engaged in their work and better prepared for more authentic research experiences.

In this outreach project, James and colleagues had 101 schools participate in collecting data. Armed with a handy anole ID guide created by Jason Kolbe and a video by James explaining anole biology and species differences, students and teachers set out to conduct 15 minute visual surveys. On these surveys, they recorded how many animals they encountered, the species ID, and the approximate body size using a provided standardized collection protocol and entering data into a Google forms site.

The results were overwhelming: more than 1,000 students conducted a total of 1,356 surveys resulting in 12,000+ lizard observations! This project produced massive amounts of data on very short time frames. In general, distribution patterns fell as they were expected to, although some records certainly hint at some mis-identification (e.g. some A. cristatellus locations). Unsurprisingly, the least abundant lizards were those that were hardest to detect: the species typically found high in trees.

While the resulting dataset is impressively large, James admits that there are data quality issues with collecting data in this manner and asked for input on how to improve data collection. Specifically, he suggested that in the future they would like to incorporate photographic and smartphone GPS information, perhaps via an app. Does anyone have any suggestions for James on implementing such an app or otherwise improving the design?

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