RESEARCH

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PITVIPER VENOM

CHARACTER DISPLACEMENT & MACROEVOLUTION

Imagine you enter a restaurant to find your cousin sitting at a completely empty dinner table. You decide to join them at the table, but notice that the only thing your cousin has is a fork. Weird…why doesn’t your cousin have any other silverware? Soon, a waiter comes and sits down a bowl of spaghetti and a bowl of soup in the center of the table. The waiter then comes to you and asks if you would like a fork or a spoon. You now have a choice. You can either [1] take the fork and fight your cousin for the bowl of spaghetti or [2] take the spoon and have the entire bowl of soup to yourself.

 

This scenario is fairly common in evolutionary biology and is a phenomena known as character displacement. In this scenario, you and your cousin are closely related species which normally live in different areas, but there are some areas where you run into one another. However, one of you is older (or at least arrived in that shared area first) and is prepared for the environment with a fork in hand. The fork in this scenario is a trait that helps you eat or function in the environment. The waiter in this scenario is a representation of alternate evolutionary strategies; asking whether you would like to compete for resources or if you would like to wield a different trait that allows you to have another resource to yourself.

 

For my dissertation, I aim to examine whether venom in pitvipers show this pattern of divergence in closely related co-distributed species. Venom is an ecologically important trait used for prey capture and prey species often develop a degree of resistance to venom. Therefore, if one species is specialized to prey on one species, a close relative should theoretically evolve a divergent venom to specialize on a different prey rather than compete with its relative.

Associated Publications:

SIDEWINDER RATTLESNAKE

VENOM EVOLUTION

Associated Publications:

  1. Hofmann EP†, Rautsaw RM†, Strickland JL, Holding ML, Hogan MP, Mason AJ, Rokyta DR, Parkinson CL. Comparative venom-gland transcriptomics and venom proteomics of four Sidewinder Rattlesnake (Crotalus cerastes) lineages reveal little differential expression despite individual variation. (in review at Scientific Reports)

Sidewinder 1d_.jpg

Sidewinder Rattlesnakes (Crotalus cerastes) are an iconic rattlesnake species well known for their desert-specialized strategy of locomotion and the scales that resemble horns above their eyes. However, despite being distributed from California to Arizona and further south into Northwest Mexico, very little is known about their venom. In many species which occupy the same range, venom is highly divergent between populations, so we wanted to know whether this same pattern held for Sidewinders. 

We used methods known as transcriptomics and proteomics to characterize the venom of Sidewinders across their range in the United States and test for differences in their venom expression patterns between evolutionary lineages. 

Overall, we found that:

  1. Venom is largely consistent with other rattlesnake species.

  2. Most variation in the venom was on the individual level and was not related to evolutionary lineages, subspecies, or age.

  3. Important to include multiple individuals for characterization of full venom arsenal. 

  4. Important to accurately account for evolutionary history when testing for differences in expression.

GOPHER TORTOISE

MOVEMENT ECOLOGY & CONSERVATION

Associated Publications:

  1. Rautsaw RM, Martin SA, Vincent BA*, Lanctot K*, Bolt MR, Seigel RA, Parkinson CL. 2018. Stopped dead in their tracks: The impact of railways on Gopher Tortoise (Gopherus polyphemus) movement and behavior. Copeia 106(1): 135–143. DOI: 10.1643/CE-17-635

  2. Rautsaw RM, Martin SA, Lanctot K*, Vincent BA*, Bolt MR, Seigel RA, Parkinson CL. 2018. On the road again: Assessing the use of roadsides as wildlife corridors for Gopher Tortoises (Gopherus polyphemus). Journal of Herpetology 52(2): 136-144. DOI: 10.1670/17-013

  3. Martin SA, Rautsaw RM, Bolt MR, Parkinson CL, Seigel RA. 2017. Adapting coastal management to climate change: Mitigating our shrinking shorelines. The Journal of Wildlife Management 81(6): 982-989. DOI: 10.1002/jwmg.21275

Gopher Tortoises (Gopherus polyphemus) are known as ecosystem engineers because the burrows they dig provide shelter for over 360 different species throughout the Southeastern United States where they are distributed. However, despite their importance in the ecosystem, their populations are slowly declining due to habitat destruction and urbanization including the presence of roads and railways. For my Master's degree at the University of Central Florida, I researched the impact of roads and railways on Gopher Tortoise movement. 

 

In addition to understanding their movement patterns, I also worked with Scott A. Martin to develop a method to combine distance sampling and occupancy modeling to estimate Gopher Tortoise abundance in a given area based on the observation of their burrows. We utilized this method to test if man-made coastal sand dunes used to combat sea-level rise and climate change are quickly colonized and utilized by Gopher Tortoises. 

Overall, we found that:

  1. Railways are significant barriers to movement (see video above)

  2. Tortoises use roadsides as normal habitat and roadsides may function as ecological traps.

  3. Our method of abundance estimation is comparable to previous methods while providing additional ecological information.

  4.  Gopher Tortoises regularly use the man-made dunes and they represent a successful management strategy for coastal populations

USING GAME CAMERAS TO DETECT

REPTILES, AMPHIBIANS, AND SMALL MAMMALS

Associated Publications:

  1. Martin SA, Rautsaw RM, Robb F, Bolt MR, Parkinson CL, Seigel RA. 2017. Set AHDriFT: Applying game cameras to drift fences for surveying herpetofauna and small mammals. The Wildlife Society Bulletin 41(4): 804-809. DOI: 10.1002/wsb.805

  2. Martin SA, Rautsaw RM, Bolt MR, Parkinson CL, Seigel RA. 2018. Estimating the response of wildlife communities to coastal dune construction. Ocean & Coastal Management 161(1): 31-36. DOI: 10.1016/j.ocecoaman.2018.04.021

Game cameras are becoming more and more common in ecological studies to characterize communities and calculate abundance of species. However, normally, game cameras are only useful for detection of large mammals and other warm-blooded (endothermic) animals. Small, cold-blooded animals are difficult to detect because they cannot trigger the infrared sensors on the cameras. In collaboration with Scott A. Martin, we developed and tested a method to combine drift fences (a common method of trapping reptiles) and game cameras to detect small animals including ectothermic reptiles and amphibians. We also utilized this method to test if man-made coastal sand dunes used to combat sea-level rise and climate change are quickly colonized and utilized equally to natural sand dunes.

Overall, we found that:

  1. Our method was highly sensitive and capable of detecting all sizes of reptiles, amphibians, and even small invertebrates such as velvet ants and centipedes. 

  2. There were some differences between natural and man-made dunes, but these differences were largely driven by rarely observed species.

  3. When accounting for rare species, man-made dunes and natural dunes are equal. Therefore, man-made dunes represent a successful management strategy for coastal populations