American Journal of Botany最新文献

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.

Climate change and land-use alterations are driving forest fires to unprecedented frequencies and intensities worldwide. Even wet tropical forests—historically rarely subjected to fire—are increasingly experiencing fire disturbances. The impact of wildfires on these forests is likely large, since many of their tree species are not adapted to fire. The extent of the consequences depends on complex feedback mechanisms between fire and vegetation, with plant functional traits playing a critical role. However, how different traits may drive fire–vegetation dynamics in such ecosystems is poorly understood due to limited consolidation of relevant data. This uncertainty leaves the future of tropical forests in question. In this review, we explore how functional traits influence the feedback between fire and vegetation. Specifically, we examine how functional traits of species shape (1) fire regimes (here considered in terms of fire frequency and intensity) through fuel characteristics, (2) their resistance to fire, and (3) their recovery after fire. Resilience is conceptualized as resistance to biomass loss and capacity for post-disturbance biomass recovery. We provide a comprehensive overview of these traits and 12 mechanisms involved. Since the relative importance of these traits and mechanisms for fire dynamics and species’ fire resilience remains unknown, we conclude by outlining possible scenarios for how novel fire regimes might affect tropical forest resilience. We also identify knowledge gaps and avenues for future research to improve our understanding of fire–vegetation dynamics in tropical forests.