American Journal of Botany最新文献

Polyploid research has traditionally distinguished between autopolyploids and allopolyploids on the basis of evolutionary origins, modes of inheritance, or chromosomal pairing behavior during meiosis. It has long been recognized, however, that a binary classification does not accurately reflect the complexity and diversity inherent to polyploid organisms, and that these definitions may be inadequate to capture biological diversity. Moreover, inferred conditions at polyploid formation are often obscured by numerous post-polyploidy genomic processes, necessitating a temporal perspective on the meaning of polyploid terminology. In this review, we explore the concept of the “polyploid continuum” and highlight the temporal biological fluidity between the classically recognized alternative end points of autopolyploidy and allopolyploidy. We consider aspects of the polyploid continuum that might meaningfully be evaluated on the basis of genetic variation, including at the sequence, structural, and functional levels. We discuss the utility of the polyploid continuum concept and how it might be visualized as a multidimensional landscape of polyploid diversity that represents a temporal snapshot at any one time. This perspective may better reveal the genesis of polyploid diversity in its many dimensions and provide a framework for understanding the dynamic evolutionary processes that underpin polyploid variation.

Reconstructing the evolution of crop plants is fundamental to understanding their origins, ecological adaptations, and impacts on ecosystem processes. However, our understanding of crop evolution stems largely from archaeology and genetics, with less focus on a trait-based ecological approach. Crop-specific studies have shown that phenotypic traits changed substantially during domestication and modern breeding. Yet, global comparative analyses across multiple species and traits remain scarce. Moreover, we largely ignore which plant traits distinguish wild species that were domesticated (progenitors) from those that were not, and how their ecological profiles differ. Here, I propose a conceptual model that integrates crops, their wild progenitors, and other non-domesticated herbaceous species into Grime's CSR theory and the integrated framework of plant form and function. This model provides insights into the evolutionary trajectories of domesticated plants along economics, root-microbial collaboration, and size spectra, shedding light on the ecological strategies of the wild progenitors of crops. After a comprehensive review, I emphasize that crops and their wild progenitors share similar resource-use traits, as progenitors were already highly acquisitive species. Conversely, main trait differences between domesticated and progenitor plants occur along size and collaboration axes, driven primarily by selection of large-seeded genotypes and intensive agricultural practices, respectively. I propose that crops deviate from the disturbance-adapted strategies of their wild progenitors toward more competitive ones, including links to different stages of evolution under cultivation. Finally, I outline implications for future breeding programs and the origins of agriculture, and recommend research directions to further advance our understanding of crop evolution.

Why did it take so long for angiosperms to diversify after they arose? Here I consider the indirect but potentially crucial impact of the “photosynthetic revolution” on plant–herbivore coevolution. Increased vein density in fossil leaves implies a doubling in photosynthesis 125–100 million years ago. Higher photosynthetic rates increase the opportunity cost of anti-herbivore defenses, favoring shifts to chemically diverse, low-cost, low-molecular-weight qualitative toxins (e.g., alkaloids) from chemically stereotyped, high-cost, high-molecular-weight quantitative toxins (e.g., tannins). Given the greater functional significance of incremental changes in defensive compounds of lower molecular weight, shifts to qualitative toxins should accelerate plant-herbivore coevolution and species diversification. The large genome and cell sizes of ferns and gymnosperms should drive lower rates of coevolutionary diversification by decreasing vein density and photosynthetic rates; high vein density found in many euasterids, eurosids, and monocots should drive higher diversification rates. This theory might also explain the general restriction of qualitative toxins to herbaceous plants, given the higher photosynthetic rates of herbs vs. woody plants. Lower hydraulic limitation and selection for small genomes in short, fast-growing, short-lived plants should foster evolution of small cells, fine vein networks, high leaf N levels and photosynthetic rates, reliance on qualitative toxins, and high speciation rates.