Monday, July 2, 2018

Field Work in Paradise

This summer the Chipojo Lab has initiated some new projects at a fascinating new field site in the Indian River Lagoon on the Atlantic coast of Florida. We are working in the Indian River Aquatic Preserve which stretches for 12 miles along the Indian River Lagoon from Vero Beach in the north to Fort Pierce in the south, encompassing over 9500 acres of protected land. Florida’s aquatic preserves aim to maintain the natural beauty of Florida’s coastlines, managed for wildlife habitat, recreation, and cultural heritage.

A group of dolphins surface near one of our islands.

I am only slightly larger than a newborn 'tee.

Along the lagoon are countless spoil islands, which are small, man made islands that result when the debris dredged up to make the channel piles up and breaks the surface. These islands eventually become vegetated and have developed into unique wildlife habitat. Many of the larger islands are home to populations of green and brown anoles, which are the focus of our study. To get to these islands, as you might imagine, we needed a boat. For this purpose, the Chipojo Lab is now the proud new owner of El Lagartijo, a 14 ft aluminum jon boat that we brought with us all the way from Missouri. More about our ship later, though.

A beautiful mural on the local Manatee Center.

A vulture committee meeting we interrupted one morning.

The Indian River Lagoon is the most diverse lagoon ecosystem in the northern hemisphere,  containing a huge variety of habitats and species. During our time on the lagoon the last few months, we have been able to glimpse so many magical creatures. One important habitat are the expansive sea grass meadows, which a large proportion of the world’s West Indian manatee population calls home. We have seen manatees frolicking at one of our boat launches, Round Island, and just offshore of the islands we work on. Federally endangered wood storks nest in the lagoon, as well as many other migratory bird species. Our group has seen some boisterous nesting herons, committees of black vultures, ospreys carrying fish overhead, cormorants poking their long necks out from under the water, and pelicans diving in to catch their next snack. Dolphins also inhabit the lagoon, and we often see them catching fish and traveling past us in small groups. In addition to the majestic creatures described above, we have also seen some cool tiny critters as well, such as hermit, fiddler, and mangrove crabs, a Florida horse conch, and different sorts of fish jumping from the water. We have yet to see some cool species that call the lagoon home, such as diamondback terrapins and alligators. We are working on it, though!

Some manatees surfacing near the dock at Round Island.

There is nothing more beautiful than a calm, cool morning on the Indian River Lagoon, and I am so excited to have had this opportunity to work here.  

The striking view from the dock at the Indian River Waterfront Cottages, where we are staying.

Monday, June 11, 2018

Island Experiment on A. sagrei in Florida

Greetings from the southeast coast of Florida! My name is Stephanie, and I am working as a research assistant here with Levi and another assistant Leslie.  We have been working in Florida for about a month now and will soon start running our experiment once preparation has been completed.  For this experiment, Levi is testing learning in the brown anole, an invasive species here in Florida.  Since we are using man-made islands as experimental habitats, we have the capability to transport lizards to these areas and track their evolution. The goal for this project is to establish a database of brown anoles we put onto these islands as well as keep track of generations to come.

As of now, we have identified lizards and transported them to the islands.  We are in the process of surveying the habitats to check up on the lizards and make sure they are behaving normally and not being taken by predators.  We look forward to the commencement of this experiment and will give further updates as the project progresses.  Check back for more on the adventures of team El Lagartijo!

What a catch this little lady is! This is a female brown anole with a brightly colored dewlap and a red tinted snout

Leslie, Levi, and myself pictured as the subtropical storm Alberto passes over us

       Levi demonstrating his expert boating skills as El Lagartijo (our boat) glides across the Indian River Lagoon

Brighter is not always better

Those that follow the Chipojoblog are familiar with one of our core tenets: strive as best you can to design experiments under natural conditions. This philosophy reflects my own view that behavior should be studied in the field whenever possible. Our recent paper in Current Zoology,Visual playback of colorfulsignals in the field supports sensory drive for signal detectability,” is a prime of example of the power of this approach, in which an intimate understanding of the ecology and behavior of anoles was used to test a major prediction of the sensory drive hypothesis: are signals locally adapted? In other words, are dewlaps locally adapted to effectively grab the attention of an inattentive receiver?

Over the years we have published a series of papers supporting the hypothesis that dewlap diversity can be partially explained by selection to increase the probability of detection. However, until this paper, experimental evidence from the field was missing, in part because manipulating dewlaps of live anoles is not trivial. Furthermore, even if we were able to successfully manipulate dewlaps, there are still many other signals (e.g., body color, motion pattern, size and posture) that would be out of our control. This problem was solved by researchers working with acoustic signals a long time ago by figuring out ways to play the signal of interest in isolation in what have become known as ‘playback experiments.’ We stole a page from their book and constructed a remote-control dewlap apparatus, which provided an opportunity to display only the dewlap under natural conditions (see gizmo below).  Alex’s building and painting skills was key to the success of this gizmo. He was able to construct dewlaps with similar reflective and transmission properties of real dewlaps while taking into account the visual system of the anoles (please see papers for details). 
Control-remote dewlap display apparatus. A) Acrylic box within which electrical components were housed. B) Electrical components. C) The apparatus at a mesic site with a fake dewlap displayed.

Besides presenting the dewlaps in the field, we wanted to test the hypothesis that the dewlaps are locally adapted. Under this hypothesis, increased detection in one habitat comes at the cost of decreased detection in another habitat. This functional approach to test for adaptive value of a trait is commonly used as robust evidence to support selection favoring the evolution of the trait in question. In this paper we tested if the observed differences in dewlap brightness between xeric and mesic populations of Anolis cristatellus is adaptive. If so, dewlaps from mesic populations should be more detectable in mesic habitats and dewlaps from xeric habitats should be more detectable in xeric habitats. Furthermore, detection probability should decrease in the ‘wrong' habitat. Below are the results of the experiments.  In A. cristatellus individuals from xeric habitats have dewlaps which are darker, that is less brighter,  than individuals from mesic populations.
Responses of free-ranging A. cristatellus to fake dewlaps that mimic the brightness properties of real dewlaps.

Our findings support the sensory drive hypothesis and strongly suggest that the brightness  properties of A. cristatellus dewlaps are locally adapted via selection on signal detectability.  Furthermore, we have demonstrated that a brighter signal is not always the most detectable or effective signal. A common misconception, which is partially the result of not including the sensory system and habitat conditions as part of the analysis. Studies addressing potential functions and selective forces promoting the diversity of dewlaps found in anoles have flourished over the last decade,  nevertheless, these results are the best experimental evidence that we have to support the hypothesis that diversity of dewlap colors might be partially explained by local adaptions to habitat light conditions and the best smoking gun to support the idea that diversity of dewlap colors can be the result of local adaptations to habitat light conditions.  Additionally, our study once again underlines the need to measure both reflection and transmission when asking questions regarding the potential function of the dewlap because the two combine to determine dewlap coloration (brightness, coloration, etc.) in the real world.