13-10 A new working model to explain how plant and animal species have co-evolved with the Baja California peninsula landscape ~5 Ma to present

Session: Earth Life Sciences across the Cordillera

Presenting Author:

Greer Dolby

Authors:

Dolby, Greer Andersen¹, Munguia-Vega, Adrian², Dorsey, Rebecca J³, Bennett, Scott E.K.⁴, Andreev, Victor⁵, Darin, Michael⁶, Gardner, Kevin⁷, Araya-Donoso, Raul⁸, Davalos-Dehullu, Elizabeth⁹, Baty, Sarah M¹⁰, Biddy, Austin¹¹, Lira-Noriega, Andres¹², Wilder, Benjamin T.¹³, Cortez, Diego¹⁴, Culver, Melanie¹⁵

(1) Biology, University of Alabama at Birmingham, Birmingham, AL, USA, (2) School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA, (3) Earth Sciences, University of Oregon, Eugene, OR, USA, (4) United States Geological Survey, Portland, OR, , (5) School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA, (6) Department of Earth Sciences, University of Oregon, Eugene, OR, USA, (7) University of Oregon, Eugene, OR, , (8) School of Life Sciences, Arizona State University, Tempe, AZ, USA, (9) Centro de Ciencias Genómicas, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos, Mexico, (10) School of Life Sciences, Arizona State University, Tempe, AZ, USA, (11) Biology, University of Alabama at Birmingham, Birmingham, AL, USA, (12) Red de Estudios Moleculares Avanzados, Instituto de Ecología, A.C., Xalapa, Veracruz, Mexico, (13) Next Generation Sonoran Desert Researchers, , (14) Centro de Ciencias Genómicas, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos, Mexico, (15) School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA, (16) School of Life Sciences, Arizona State University, Tempe, AZ, USA, (17) ,

Abstract:

Biologists have long documented a striking pattern of population-level genetic divergence on the Baja California peninsula in dozens of disparate plant and animal taxa. Evolutionary theory predicts that this type of shared divergence is caused by extrinsic factors (environmental, climatic, or physiographic) rather than species-specific effects. New high-resolution geologic mapping, geochronology, and stratigraphic analysis by the Baja GeoGenomics consortium provides critical context for evaluating such drivers. Our data show that at a ≥40-km-wide region of the central peninsula has been occupied by terrestrial environments continuously over the last ~30 Myr. This result shows that the mid-peninsula was never submerged and did not form island or archipelago paleo-configurations, refuting long-standing seaway vicariance hypotheses to explain biological divergence patterns. By integrating our geological reconstructions with genomic (DNA) and transcriptomic (RNA) data from plants and animals, we have developed a new working model for species evolution on the peninsula over the last ~5 Myr. In this model, dissected topography interacts with strong regional climate disparities to generate persistent environmental heterogeneity, driving differential adaptation among northern, southern, and in some cases, east–west populations. Supporting this framework, we detect widespread and statistically significant niche divergence between northern and southern populations across 21 taxa. Using information-theoretic and integrative statistical analyses, we find that physical distance and climate explain most population divergence in the lizard Uta stansburiana (87%) and the desert shrub Encelia farinosa (89%), with each responding to distinct climatic factors. Divergence associated with monsoonal precipitation in the lizard is linked to selection on genes involved in brain development, cognition, and sensory perception. In contrast, divergence in the shrub associated with temperature and ultraviolet radiation involves genes for trichome development, light-regulated growth, and circadian rhythm. Older genetic divergence events (ca. 9.3–13.2 Ma) in the lizard Urosaurus nigricaudus are unexplained by modern abiotic variables, reflecting its evolution on a paleolandscape fundamentally different from today. This paleogeographic setting is tectonically reconstructed by restoring the position of the peninsula ~300–400 km southeastward to western mainland Mexico. Together, results refute an island-driven history of diversification, instead revealing that complexity–abiotic heterogeneity across axes—has fueled peninsular endemism and biodiversity. They underscore the necessity of integrating primary geological data into evolutionary studies to understand how Earth processes shape the origin of species. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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