Editorial Type:
Article Category: Research Article
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Online Publication Date: 16 Dec 2020

Integrating Genetics and Metapopulation Viability Analysis to Inform Translocation Efforts for the Last Northern Leopard Frog Population in Washington State, USA

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Page Range: 465 – 475
DOI: 10.1670/19-097
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ABSTRACT

Population genetic and population viability analyses are powerful instruments that can be used to evaluate the status of populations of conservation concern. However, these two methods are rarely integrated. To better understand the status of the last known Northern Leopard Frog (Lithobates pipiens) population in Washington state, USA, and investigate the potential for translocation efforts, we analyzed 96 genetic samples from 2004 and 294 genetic samples from 2014 by using seven microsatellite loci and integrated population genetic data with population viability models. Partitioning of genetic diversity indicated the presence of three subpopulations in the area, aligning with Washington Department of Fish and Wildlife subunit designation within the watershed. In both years, heterozygosity and average number of alleles per locus were low for all subpopulations (0.20–0.36 and 1.86–2.50, respectively). Point estimates of gene flow out of two of the three subpopulations decreased from 2004 to 2014 based on G′′ST (a measure of genetic differentiation) and migration estimates from BayesAss. Summed effective population size for the entire area by using temporal estimates was estimated to be small, with large amounts of uncertainty (sum of 98.4 individuals, 95% confidence interval: 15.6–infinity individuals). Population viability models using genetic estimates of number of adults and migration rates suggest that adults may be the optimal life history stage for successful direct translocation; however, because only metamorphs can be routinely collected, translocation with head-starting was modeled and active management strategies may be necessary to establish new populations.

Copyright: Copyright 2020 Society for the Study of Amphibians and Reptiles 2020
Fig. 1. 
Fig. 1. 

Survey area of individuals of Northern Leopard Frogs (Lithobates pipiens) near Moses Lake, Washington state, USA, taken in summers 2004 and 2014 by WDFW. Numbers in parentheses represent number successfully genotyped at each drainage unit for 2004 and 2014 from toe clips (N = 294 and 96, respectively). Sample points were converted to a convex polygon and buffered for protection of site.

Fig. 2. 
Fig. 2. 

Model parameterization using genetic and literature values. Blue represents parameters estimated from genetic data. Red represents parameterization from the literature. Purple represents a combination of the two. A = adult number; E = egg number; F = fecundity rate; M = metamorph number; Mr = migration rate; S = survivorship rate. Single subpopulation shown. Starting population numbers for metamorphs and eggs were calculated by using the number of adults determined by COLONY (187), reproduction rates, and survival rates assuming the population size did not change from 2013 to 2014. Dashed shading indicates a combination of genetic and literature data.

Fig. 3. 
Fig. 3. 

Subpopulation (A, BCDG, F, and N) sizes of adult female Northern Leopard Frogs (Lithobates pipiens) after 50 yr postcollection under three scenarios. Simple = survivorship previously described, with parameters drawn from a normal distribution, 10% of the parameter value set to the SD, each year. Rough = poor years occurring with a yearly probability of 0.10 with all parameters from top being reduced by 20%. Dry = 0.05 chance of no recruitment in the year. N represents a newly established pond through translocation. First 25 of 100 runs are shown. A–C represent different stages removed for establishment of N. Model parameters used were means of 0.03 egg-to-metamorph survival, 0.05 metamorph-to-adult survival, 0.60 adult-to-adult survival, and a carrying capacity of 1,500 for entire Moses Lake, Washington state, USA, population. Collection from source subpopulations is modeled to occur in year 1. Red line represents N = 50. Numbers in plots represent the number of individuals moved and the number of failed runs, if failed runs was greater than 5 of the 100.

Fig. 4. 
Fig. 4. 

Effects of headstarting Northern Leopard Frog (Lithobates pipiens) metamorphs, the only available stage, to increase probability of establishment at a new population. Double = headstarting program to boost survivorship. With eggs and metamorphs/juveniles, this represents boosting survivorship to 50% from the given stage to the following stage. Adult headstarting encompasses collecting adults, placing them at the new site, and then collecting half of the metamorphs at that site and increasing their survivorship to 50%. Simple = survivorship previously described, with parameters drawn from a normal distribution, 10% of the parameter value set to the SD, each year. Rough = poor years occurring with a yearly probability of 0.10 with all parameters from top being reduced by 20%. Dry = 0.05 chance of no recruitment in the year. Sizes reported of adult females after 50 yr postcollection. A–C represent different stages removed for establishment of N. N, the new population and target of the translocation. Red line represents N = 50. Only first 25 of 100 runs shown. Numbers shown are the total number of individuals brought in across all three subpopulations.

Appendix Fig. 1. 
Appendix Fig. 1. 

STRUCTURE results of 187 genotyped Northern Leopard Frog (Lithobates pipiens) toe clips from around Moses Lake, Washington state, USA. k = 3 was the most supported number of subpopulations based on the Evanno method. Letters represent the subunit designation from WDFW.

Appendix Fig. 2. 
Appendix Fig. 2. 

BIC as a function of the number of clusters during DAPC analysis seven microsatellite loci for 187 genotyped Northern Leopard Frog (Lithobates pipiens) toe clips.

Appendix Fig. 3. 
Appendix Fig. 3. 

DAPC for genetic data for 187 Northern Leopard Frogs (Lithobates pipiens) by using seven microsatellite loci.

Appendix Fig. 4. 
Appendix Fig. 4. 

Source population (A) size of adult female Northern Leopard Frogs (Lithobates pipiens) after 50 yr postcollection under three scenarios. Simple = survivorship previously described, with parameters drawn from a normal distribution, 10% of the parameter value set to the SD, each year. Rough = poor years occurring with a yearly probability of 0.10 with all parameters from top being reduced by 20%. Dry = 0.05 chance of no recruitment in the year. N represents a newly established pond through translocation. First 25 of 100 runs are shown. A–C represent different stages removed for establishment of N. Model parameters used were means of 0.03 egg-to-metamorph survival, 0.05 metamorph-to-adult survival, 0.60 adult-to-adult survival, and a carrying capacity of 1,500 for entire Moses Lake, Washington state, USA, population. Collection from source subpopulations is modeled to occur in year 1. Red line represents N = 50.

Contributor Notes

3

Present address: Department of Fish and Wildlife Sciences, 875 Perimeter Drive MS 1136, Moscow, Idaho 83844-1136, USA

4 Corresponding Author. E-mail: travis.seaborn@wsu.edu
Accepted: 07 Aug 2020
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