Cryptic genetic diversity, population structure, and gene flow in the Mojave rattlesnake (Crotalus scutulatus)

Schield, Drew R.; Adams, Richard H.; Card, Daren C.; Corbin, Andrew B.; Jezkova, Tereza; Hales, Nicole R.; Meik, Jesse M.; Perry, Blair W.; Spencer, Carol; Smith, Luis J.; García, Gustavo Campillo; Bouzid, Nassima M.; Strickland, Jason L.; Parkinson, Christopher L.; Borja, Miguel; Castañeda, Gamaliel; Bryson, Robert W.; Flores‐Villela, Oscar; Mackessy, Stephen P.

doi:10.1016/j.ympev.2018.06.013

Cited by 35 publications

(50 citation statements)

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“…Mountain mahogany populations had significantly elevated genetic differentiation across the Continental Divide, especially in central Colorado, where the Continental Divide is at its highest altitude. Several studies have shown that the Continental Divide is a strong barrier to gene flow (Schield et al, 2018; Machado et al, 2018). However, to date, no published study has documented this in plant species.…”

Section: Discussionmentioning

confidence: 99%

Implications of genetic heterogeneity for plant translocation during ecological restoration

Crow

Runcie

Hufford

2020

Preprint

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1Ecological restoration practices often require translocating plant material from distant sites. 2 Yet published guidelines for seed transfer are available in very few species. Accurately pre-3 dicting how plant populations will perform when transferred requires multi-year and multi-4 environment field trials and comprehensive follow-up census work. In this study, we analyzed 5 the genetic structure of an important shrub used in ecological restorations in the Southern 6 Rocky Mountains called alderleaf mountain mahogany (Cercocarpus montanus) by sequenced 7 1440 individual plant samples from 48 populations across a broad geographic range. We 8 found that geographic and environmental covariates of genetic differentiation and diver-9 sity reflected the complex climate and topography across which the species is distributed.10We identified several temperature and precipitation variables that were useful predictors of 11 genetic differentiation in this species and can be used to generate seed transfer recommen-12 dations. These results will be useful for defining management and restoration practices for 13 mountain mahogany and other widespread montane plant species.

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Section: Discussionmentioning

confidence: 99%

Implications of genetic heterogeneity for plant translocation during ecological restoration

Crow

Runcie

Hufford

2020

Preprint

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“…[35] Anderson and Greenbaum 2012. [36]Schield et al, 2018. [37]Ashton and de Queiroz 2001. [38] Davis et al, 2016.…”

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Comparative phylogeography reveals how a barrier filters and structures taxa in North American warm deserts

Provost

Myers

Smith

2020

Preprint

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The study of biogeographic barriers have been instrumental in understanding the evolution and distribution of taxa. Now with the increased availability of empirical datasets, it is possible to infer emergent patterns from communities by synthesizing how barriers filter and structure populations across species. We assemble phylogeographic data for a barrier and perform spatially-explicit simulations to quantify temporal and spatial patterns of divergence, the influence of species traits on these patterns, and understand the statistical power of differentiating alternative diversification modes. We incorporate published datasets to examine taxa around the Cochise Filter Barrier, separating the Sonoran and Chihuahuan deserts of North America, to synthesize phylogeographic structuring across the community with respect to organismal functional traits. We then use a simulation and machine learning pipeline to assess the power of phylogeographic model selection. Taxa distributed across the Cochise Filter Barrier show heterogeneous responses to the barrier in levels of gene flow, phylogeographic structure, divergence timing, barrier width, and divergence mechanism. These responses vary concordantly with locomotor and thermoregulatory traits. Many taxa show a Pleistocene population genetic break, often with introgression after divergence. Allopatric isolation and isolation-by-environment are the primary mechanisms purported to structure taxa. Simulations reveal that in spatially-explicit isolation-with-migration models across the barrier, age of divergence, presence of gene flow, and presence of isolation-by-distance can confound the interpretation of evolutionary history and model selection by producing easily-confusable results. By synthesizing phylogeographic data for the Cochise Filter Barrier we show a pattern where barriers interact with species traits to differentiate taxa in communities over millions of years. Identifying the modes of differentiation across the barriers for these taxa remains challenging because commonly invoked demographic models may not be identifiable across a range of likely parameter space.

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“…Introduction FIGURE 1. Mitochondrial phylogeny of Crotalus scutulatus lineages reproduced from Schield et al (2018), with arrows showing inferred gene flow between adjacent clades. Grey bars represent hypotheses of species limits corresponding to (A) a four-species model where each mitochondrial clade is a species, (B) a two-species model where the deepest mitochondrial split coincides with species (i.e., "expanded salvini" hypothesis), (C) a three-species model where the deepest nuclear splits coincides with species (i.e., an alternative "expanded salvini" hypothesis), (D) a two-species model where current subspecies are elevated to species, and (E) a one-species model where C. scutulatus is recognized as a single species.…”

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confidence: 99%

“…Here we investigate morphological variation across the distribution of Crotalus scutulatus and evaluate our inferences in context of recent molecular studies (Schield et al 2018;Strickland et al 2018b) to evaluate the taxonomic status of the species. Because our purpose was to interpret phenotypic patterns within the context of previous genetic studies, we considered five alternative species hypotheses ( Fig.…”

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confidence: 99%

“…Because our purpose was to interpret phenotypic patterns within the context of previous genetic studies, we considered five alternative species hypotheses ( Fig. 1): (A) each of four putative genetic lineages represents a unique species; (B) a more conservative hypothesis whereby the deepest lineage divergence (at the boundary between Chihuahuan and Central Plateau populations) divides C. scutulatus into two species (i.e., an "expanded salvini" concept); (C) an alternative "expanded salvini" concept, but which further splits Mohave-GEOGRAPHIC VARIATION IN CROTALUS SCUTULATUS COMPLEX Zootaxa 4683 (1) © 2019 Magnolia Press · 131 Sonoran and Chihuahuan lineages, in congruence with the deepest nuclear splits (Schield et al 2018); (D) each subspecies (as currently defined geographically) represents a species; or (E) C. scutulatus is maintained as a single species. Based on previous analyses of genetic data, each of these hypotheses has some merit, but a more definitive taxonomic assessment would benefit from a perspective from morphological variation.…”

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Geographic variation in morphology in the Mohave Rattlesnake (Crotalus scutulatus Kennicott 1861) (Serpentes: Viperidae): implications for species boundaries

Watson

Spencer

Schield

et al. 2019

Zootaxa

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The Mohave Rattlesnake (Crotalus scutulatus) is a highly venomous pitviper inhabiting the arid interior deserts, grasslands, and savannas of western North America. Currently two subspecies are recognized: the Northern Mohave Rattlesnake (C. s. scutulatus) ranging from southern California to the southern Central Mexican Plateau, and the Huamantla Rattlesnake (C. s. salvini) from the region of Tlaxcala, Veracruz, and Puebla in south-central Mexico. Although recent studies have demonstrated extensive geographic variation in venom composition and cryptic genetic diversity in this species, no modern studies have focused on geographic variation in morphology. Here we analyzed a series of qualitative, meristic, and morphometric traits from 347 specimens of C. scutulatus and show that this species is phenotypically cohesive without discrete subgroups, and that morphology follows a continuous cline in primarily color pattern and meristic traits across the major axis of its expansive distribution. Interpreted in the context of previously published molecular evidence, our morphological analyses suggest that multiple episodes of isolation and secondary contact among metapopulations during the Pleistocene were sufficient to produce distinctive genetic populations, which have since experienced gene flow to produce clinal variation in phenotypes without discrete or diagnosable distinctions among these original populations. For taxonomic purposes, we recommend that C. scutulatus be retained as a single species, although it is possible that C. s. salvini, which is morphologically the most distinctive population, could represent a peripheral isolate in the initial stages of speciation.

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Cryptic genetic diversity, population structure, and gene flow in the Mojave rattlesnake (Crotalus scutulatus)

Cited by 35 publications

References 67 publications

Implications of genetic heterogeneity for plant translocation during ecological restoration

Implications of genetic heterogeneity for plant translocation during ecological restoration

Comparative phylogeography reveals how a barrier filters and structures taxa in North American warm deserts

Geographic variation in morphology in the Mohave Rattlesnake (Crotalus scutulatus Kennicott 1861) (Serpentes: Viperidae): implications for species boundaries

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