Phylogenetic structure of Holbrookia lacerata (Cope 1880) (Squamata: Phrynosomatidae): one species or two?

Abstract

Species delimitation attempts to match species-level taxonomy with actual evolutionary lineages. Such taxonomic conclusions are typically, but not always, based on patterns of congruence across multiple data sources and methods of analyses. Here, we use this pluralistic approach to species delimitation to help resolve uncertainty in species boundaries of phrynosomatid sand lizards of the genus Holbrookia. Specifically, the Spot-tailed Earless Lizard (H. lacerata) was historically divided into a northern (H. l. lacerata) and southern (H. l. subcaudalis) subspecies based on differences in morphology and allopatry, but no research has been conducted evaluating genetic differences between these taxa. In this study, patterns in sequence data derived from two genes, one nuclear and one mitochondrial, for 66 individuals sampled across 18 counties in Texas revealed three strongly supported, reciprocally monophyletic lineages, each comprised of individuals from a single geographic region. Distinct genetic variation evident across two of these regions corresponds with differences in morphology, differences in environmental niche, and lines up with the presumed geographic barrier, the Balcones Escarpment, which is the historical subspecies boundary. The combined evidence from genetics, morphology and environmental niche is sufficient to consider these subspecies as distinct species with the lizards north of the Balcones Escarpment retaining the name Holbrookia lacerata, and those south of the Balcones Escarpment being designated as Holbrookia subcaudalis.

Estuary‐Level Genomic Variation Confirms Demographic and Life History Differences among Black Drum Populations in Texas

“…2014; Hibbits et al. 2019). More directly, the hypersaline “barrier” of the Laguna Madre is a commonality associated with the population structure of eastern oysters Crassostrea virginica (Anderson et al.…”

Transcriptome sequencing reveals signatures of positive selection in the Spot-Tailed Earless Lizard

“…We successfully annotated a total of 71,314 transcripts into 55 functional categories using GO-Slim assignments within the three categories of the GO classification system biological process, cellular component, and molecular function. The primary categories our coding genes were clustered into are cellular metabolic processes (30,145), nitrogen compound metabolic process (28,816), primary metabolic process (23,249), and ion binding (21,228). A breakdown of GO terms for each category for each Holbrookia sample is shown in Fig 3.…”

“…The results in this study, alongside Roelke et al (2018) finding that both the northern and southern lizards are genetically distinct using mitochondrial genomes, all further support the Hibbitts et al (2019) recent reclassification of their taxonomy. The elevation of the Northern and Southern Spot-Tailed Earless Lizard from subspecies to full species status requires the FWS consider them separately for protection, as each species faces unique threats [23,24]. The southern H. subcaudalis has two isolated populations that were once part of a larger distribution across southern Texas, while the more robust northern species has more observations in multiple surveys of the region [23].…”

“…The elevation of the Northern and Southern Spot-Tailed Earless Lizard from subspecies to full species status requires the FWS consider them separately for protection, as each species faces unique threats [23,24]. The southern H. subcaudalis has two isolated populations that were once part of a larger distribution across southern Texas, while the more robust northern species has more observations in multiple surveys of the region [23].…”

“…Renewed interest in resolving their taxonomic status revealed that the disjunct populations are reciprocally monophyletic with an approximately 4% mitochondrial sequence divergence [3]. Most recently, Hibbits et al (2019) took an integrative approach and used morphology, mitochondrial, and nuclear data to elevate each subspecies to full species status [23].…”