Chromosomal evolution, environmental heterogeneity, and migration drive spatial patterns of species richness in Calochortus (Liliaceae)

• 成果类型: Article
• 署名作者: Karimi, Nisa; Krieg, Christopher P.; Spalink, Daniel; Lemmon, Alan R.; Lemmon, Emily Moriarty; Eifler, Evan; Hernandez, Adriana I.; Chan, Patricia W.; Landis, Jacob B.; Strickler, Susan R.; Rodriguez, Aaron; Specht, Chelsea D.; Givnish, Thomas J.
• 署名单位: Missouri Botanical Gardens; University of Wisconsin System; University of Wisconsin Madison; Texas A&M University System; Texas A&M University College Station; State University System of Florida; Florida State University; State University System of Florida; Florida State University; Cornell University; Cornell University; Universidad de Guadalajara; Cornell University; Boyce Thompson Institute for Plant Research
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9829
• DOI: 10.1073/pnas.2305228121
• 发表日期: 2024-03-05
• 关键词: founder-event speciation; historical biogeography; serpentine endemism; adaptive radiation; number evolution; model selection; plant diversity; global patterns; gene flow; diversification

摘要

We used nuclear genomic data and statistical models to evaluate the ecological and evolutionary processes shaping spatial variation in species richness in Calochortus (Liliaceae, 74 spp.). Calochortus occupies diverse habitats in the western United States and Mexico and has a center of diversity in the California Floristic Province, marked by multiple orogenies, winter rainfall, and highly divergent climates and substrates (including serpentine). We used sequences of 294 low-copy nuclear loci to produce a time-calibrated phylogeny, estimate historical biogeography, and test hypotheses regarding drivers of present-day spatial patterns in species number. Speciation and species coexistence require reproductive isolation and ecological divergence, so we examined the roles of chromosome number, environmental heterogeneity, and migration in shaping local species richness. Six major clades-inhabiting different geographic/climatic areas, and often marked by different base chromosome numbers (n = 6 to 10)-began diverging from each other similar to 10.3 Mya. As predicted, local species number increased significantly with local heterogeneity in chromosome number, elevation, soil characteristics, and serpentine presence. Species richness is greatest in the Transverse/Peninsular Ranges where clades with different chromosome numbers overlap, topographic complexity provides diverse conditions over short distances, and several physiographic provinces meet allowing immigration by several clades. Recently diverged sister-species pairs generally have peri-patric distributions, and maximum geographic overlap between species increases over the first million years since divergence, suggesting that chromosomal evolution, genetic divergence leading to gametic isolation or hybrid inviability/sterility, and/or ecological divergence over small spatial scales may permit species co-occurrence.