Search for: All records

ABSTRACT AimWe tested whether co‐distributed phrynosomatid lizards in the Baja California Peninsula (BCP) share synchronous phylogeographic discontinuities, as predicted by the “peninsular archipelago” hypothesis, and examined the diversification ofCallisaurus draconoidesthroughout its range. LocationThe BCP and the Great Basin, Mojave and Sonoran Deserts of southwestern North America. TaxaFive co‐distributed species complexes representing four genera within Phrynosomatidae:Callisaurus,Petrosaurus,UrosaurusandSceloporus. MethodsDouble‐digest restriction‐associated‐DNA (ddRAD) sequencing was used to collect genome‐wide sequence data for 309 lizards. We used phylogenetic analyses of concatenated loci and population admixture analysis of unlinked SNPs to identify lineages. To infer a species tree, we collected target sequence capture (TSC) data. Migration between adjacent peninsular lineages was estimated using the multispecies coalescent with migration (MSC‐M) in BPP. A full‐likelihood Bayesian comparative phylogeographic approach (ecoevolity) was used to test the simultaneous divergence hypothesis for the Isthmus of La Paz and Vizcaíno Desert. ResultsWe identified 24 potential lineages within the five co‐distributed complexes. Contact zones between lineages were observed at the Isthmus of La Paz in four of the five complexes, and in all five within the Vizcaíno Desert. The time‐calibrated species tree indicates that within each complex, divergences at the Isthmus of La Paz predate those across the Vizcaíno Desert. We found strong support for at least three independent divergence events at the Isthmus of La Paz and the Vizcaíno Desert, thereby rejecting the simultaneous divergence hypothesis. Inferred migration rates between adjacent peninsular populations were generally low (M << 1) to absent. Zebra‐tailed lizards (Callisaurus), in which the earliest diverging lineages are endemic to the southern BCP, exhibit a clear pattern of Pleistocene range expansion from the BCP into the deserts of the western United States and mainland Mexico. The most deeply nested populations inCallisaurusoccur at the northern, eastern and southeastern range limits in temperate, subtropical and tropical biomes, respectively. Main ConclusionsThese results support the BCP's tectonic isolation as a driver of peninsular endemism and a contributing factor to lineage diversification more broadly in the region. Taxonomic adjustments, including resurrectingUrosaurus microscutatus, are proposed to better reflect evolutionary history in taxonomy. 

Abstract Phrynosoma mcallii(flat‐tailed horned lizards) is a species of conservation concern in the Colorado Desert of the United States and Mexico. We analysed ddRADseq data from 45 lizards to estimate population structure, infer phylogeny, identify migration barriers, map genetic diversity hotspots, and model demography. We identified the Colorado River as the main geographic feature contributing to population structure, with the populations west of this barrier further subdivided by the Salton Sea. Phylogenetic analysis confirms that northwestern populations are nested within southeastern populations. The best‐fit demographic model indicates Pleistocene divergence across the Colorado River, with significant bidirectional gene flow, and a severe Holocene population bottleneck. These patterns suggest that management strategies should focus on maintaining genetic diversity on both sides of the Colorado River and the Salton Sea. We recommend additional lands in the United States and Mexico that should be considered for similar conservation goals as those in the Rangewide Management Strategy. We also recommend periodic rangewide genomic sampling to monitor ongoing attrition of diversity, hybridization, and changing structure due to habitat fragmentation, climate change, and other long‐term impacts.