In this third installment of the human stories behind herpetological research, we hear the story behind a recent publication in SSAR’s Herpetological Review. The citation for that article is as follows:
Lamb, J.Y., Kreiser, B.R., Waddle, J.H., and Qualls, C.Q. 2017. Characterization of microsatellite loci for the Gulf Coast waterdog (Necturus beyeri) using paired-end Illumina shotgun sequencing and cross-amplification in other Necturus. Herpetological Review 48(4): 758 – 763.
SSAR members can access the article here. Below is a first-hand account from the lead author, Dr. Jennifer Lamb.
Necturus beyeri juvenile from the Pascagoula River. © Jennifer Lamb
“Holy [expletive]! It bit me!” Is not what you want to hear from a lab-mate at a field site in southeast Louisiana. Fortunately, Chris Pellecchia, a PhD student at the University of Southern Mississippi (USM), was dealing with a Gulf Coast Waterdog (Necturus beyeri) and not a herp with a nastier bite. Several of the adult waterdogs from that particular site were feisty, snapping and “death-rolling” in their plastic bags (like what a crocodile does with prey, but a smaller, more mucous-covered version). No blood was shed but a few bags did spring leaks.
Chris and I were sampling waterdogs for my post-doctoral research, which focused on the population genetics of N. beyeri. This work was a collaboration between myself, Dr. Hardin Waddle (USGS), and Drs. Brian Kreiser and Carl Qualls (USM). My overarching goal was to describe patterns in genetic diversity and gene flow at several spatial scales. During the initial planning stages of the post-doc, I realized that there were no published microsatellites for any species of Necturus and that developing those primers would be one of my first hurdles.
N. m. louisianensis larva form south-central Louisiana. © Brad Glorioso
By early 2016 we had some tissue samples in hand for N. beyeri, but we wanted to test primers across species of Necturus so that our efforts could facilitate comparative studies as well as genetic assessments for species of conservation concern. I contacted individuals working with the Common Mudpuppy (N. m. maculosus), the Neuse River Waterdog (N. lewisi), the Dwarf Waterdog (N. punctatus), and the Black Warrior Waterdog (N. alabamensis), and several graciously donated tissue samples towards our objective. The last taxa brought into the fold was the Red River Waterdog (N. m. louisianensis), which we trapped and dip-netted from south central Louisiana in early 2017. Prior to that outing, my own fieldwork had focused on sampling N. beyeri in southeast Louisiana and Mississippi, where small juveniles are a mottled yellow-brown. I was taken aback by the beautiful striping on juvenile N. m. louisianensis.
Although technological advances have made it easier to identify potential microsatellite primers, the process of optimizing those primers and testing loci for variability is still time consuming, particularly when multiple taxa are involved. This is sometimes an underappreciated aspect of genetics projects. After approximately 10 months of tweaking amplification protocols in the lab (and making several offerings to the PCR deities – yes, many genetics labs have at least one shrine), I was rewarded with a set of 10, polymorphic microsatellites that amplified across several species of Necturus, including our target taxon, N. beyeri. For more details on this process and our results, check out our recently published article in Herpetological Review.
Dr. Jennifer Lamb measuring N. beyeri from the Pascagoula River. © Taylor Price
We have gone on to use these loci to examine the population structure and conservation genetics of N. beyeri across its range, and to look at gene flow and the movement biology of N. beyeri at a fine-scale within an intensively sampled creek in southeast Louisiana (manuscripts in prep.). Days in the field sampling for this salamander have spanned the gamut, as they typically do with fieldwork. Sometimes our dip-netting only yielded a few N. beyeri, and we shook our fists at the creek, our weak backs, and the mosquitoes. But other days were glorious, with scores of spotted N. beyeri wriggling out from the litter in our nets. It is awesome to imagine how many salamanders are pushing through packs of litter in some of these creeks in the Gulf Coastal Plain, and it is exciting to consider how population genetics studies will complement what we understand about the biology of N. beyeri. These endeavors are the culmination of substantial collaborations among multiple individuals in and out of the field, and it has been my privilege to work in an environment with such a high spirit of camaraderie.
Jennifer Y. Lamb
Southeastern Louisiana University
Department of Biological Sciences, SLU #10736
Hammond, Louisiana 70402, USA
jennifer.lamb@selu.edu