SG: Is Pollinator Discrimination Among Populations of the Southwestern Desert Creosote Bush Differing in Chromosome Number Promoting Speciation?

本研究将通过研究荒漠灌木杂木灌木（Larrea tridentata）中不同染色体补体植物的传粉者偏好和生殖相互作用，探讨多倍体在开花植物多样化中的作用。确定一个物种变成两个物种的过程对于理解生物多样性和生态系统功能的模式至关重要。物种形成，即新物种形成的过程，发生在种群或群体之间繁殖障碍的进化过程中。然而，研究具有多染色体组的开花植物物种形成——一种被称为多倍体的情况——被证明是困难的。大多数开花植物是多倍体，染色体数目不同的类群不容易杂交，但它们很少被认为是不同的物种。造成这种情况的原因包括染色体数目不同的植物之间的物理相似性，以及它们是否适应了不同的环境。尽管具有不同染色体互补体的杂酚灌木栖息在生态上不同的区域，但它们有时会同时发生，这表明额外的生殖障碍是导致分化的原因。通过结合DNA分析、温室实验和实地调查，该项目将为具有不同染色体互补体的植物群的物种形成的早期阶段提供前所未有的见解。本研究的总体目标是通过阐明基因组复制对植物多样化的生物学意义，将多倍体物种置于物种形成研究的大保护伞下。多倍体，特别是自多倍体，基因组复制发生在一个谱系内而不是通过杂交，给进化生物学家带来了许多挑战，包括理解生态和内在遗传过程对多样化的相对重要性。种群水平分析对于评估植物-动物相互作用和生态适应如何影响染色体互补差异的“种内”群体之间的差异，以及多倍体物种的多样化是否与模式二倍体物种相似至关重要。此外，本项目以北美沙漠敏感生物群系中的关键植物Larrea tridentata及其原生传粉者为研究对象，将有助于揭示多倍体物种的新型分子多样性和生态相互作用。对染色体补体差异种群的分类识别可能会显著改变世界某些地区，特别是温带生物群落的生物多样性估计，影响我们对主要生态模式的理解。

This research will investigate the role of polyploidy in flowering plant diversification by studying pollinator preferences and reproductive interactions between plants differing in chromosome complement in the desert shrub creosote bush (Larrea tridentata). Determining the processes by which one species becomes two is crucial to understanding patterns of biodiversity and the functioning of ecosystems. Speciation, the process of new species formation, occurs when barriers to reproduction evolve between populations or groups. However, studying speciation for flowering plant species with multiple chromosome sets - a condition known as polyploidy - has proven difficult. Most flowering plants are polyploid, and groups with different chromosome numbers cannot easily interbreed, yet they are rarely recognized as different species. Reasons for this range from the physical similarity between plants with different chromosome numbers, to whether they have adapted to different environments. Although creosote bush with different chromosome complements inhabit ecologically distinct areas, they sometimes co-occur suggesting additional reproductive barriers are responsible for divergence. By combining DNA analyses, greenhouse experiments, and field investigations, this project will provide unprecedented insight into the early stages of speciation for groups of plants with different chromosome complements.The overarching goal of this research is to bring polyploid species under the larger umbrella of speciation research by elucidating the biological significance of genome duplication to plant diversification. Polyploidy, especially autopolyploidy, where genome duplication occurs within a lineage rather than through hybridization, poses many challenges for evolutionary biologists, including understanding the relative importance of ecological and intrinsic genetic processes to diversification. Population-level analyses are critical for evaluating how plant-animal interactions and ecological adaptation influence divergence among "intraspecific" groups differing in chromosome complement, and whether diversification of polyploid species is similar to model diploid species. Moreover, this project, focused on the keystone plant species Larrea tridentata and its native pollinators in sensitive North American desert biomes, will help characterize the novel molecular diversity and ecological interactions comprising the cryptic biodiversity of polyploid species. The taxonomic recognition of populations differing in chromosome complement could significantly alter biodiversity estimates for certain parts of the world, especially temperate biomes, impacting our understanding of major ecological patterns.