Consejo Nacional de Investigaciones Científicas y Técnicas - Universidad Nacional de Córdoba, Instituto Multidisciplinario de Biología Vegetal, Córdoba, Argentina.
Facultad de Ciencias Agropecuarias, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina.
Plant Biol (Stuttg). 2021 Mar;23(2):285-292. doi: 10.1111/plb.13212. Epub 2021 Jan 7.
Increased fire frequency usually erodes microenvironmental conditions, causing a drastic limitation of edaphic resources. Thus, the production of permanently closed-small flowers (cleistogamous, CL) should increase in sites with high fire frequency as this implies a less expensive reproductive assurance strategy. However, because open, insect-pollinated flowers (chasmogamous, CH) have the potential capacity to outcross via pollinators, CH progeny produced at any site should outperform selfed CL progeny. We evaluate the effect of fire frequency on the relative production of CL/CH flowers and fruits, and their seed set, along with several progeny performance parameters in Cologania broussonetii (Fabaceae), a resprouting herb with dimorphic cleistogamy native to the Chaco Serrano. Fire frequency increased cleistogamy expression, reaching extreme levels in high fire frequency sites. Seed set was similarly high for both CH and CL flowers in the unburned condition, while in burned sites the few developed CH flowers set more seeds than CL flowers. However, progeny performance was similar between CH and CL progeny at each and across all fire frequency conditions. Cleistogamy expression in C. broussonetii is maximized in abiotically degraded frequently burned habitats, although the selfed CL progeny is as successful as potentially outcrossed CH progeny. Fire frequency may decreased floral size and abundance, selecting for autogamous reproduction, which restricts not only the genetic potential of plant populations but also the resources offered to pollinators. At the community level, increased cleistogamy expression may potentially have negative implications for non-cleistogamous, more outcrossing species surviving in frequently burned environments.
火灾频率的增加通常会破坏微环境条件，导致土壤资源的急剧限制。因此，在火灾频率较高的地方，永久性闭合小花（闭花受精，CL）的产量应该会增加，因为这意味着一种成本较低的生殖保障策略。然而，由于开放的、昆虫授粉的花朵（开花受精，CH）有通过传粉者异交的潜在能力，因此在任何地点产生的 CH 后代应该优于自交的 CL 后代。我们评估了火灾频率对 CL/CH 花和果实的相对产量以及其种子结实率的影响，以及在 Chaco Serrano 地区原产的具有二型闭花受精的再生草本植物 Cologania broussonetii 中几个后代性能参数的影响。火灾频率增加了闭花受精的表达，在高火灾频率的地方达到了极端水平。在未燃烧的条件下，CH 和 CL 花的种子结实率都很高，而在燃烧的地方，少数发育的 CH 花比 CL 花结出更多的种子。然而，在每个和所有火灾频率条件下，CH 和 CL 后代的后代性能相似。在生物物理退化的频繁燃烧栖息地中，C. broussonetii 的闭花受精表达最大化，尽管自交的 CL 后代与潜在异交的 CH 后代一样成功。火灾频率可能会降低花的大小和丰度，选择自交繁殖，这不仅限制了植物种群的遗传潜力，也限制了向传粉者提供的资源。在群落水平上，增加的闭花受精表达可能对在频繁燃烧环境中生存的非闭花受精、更异交的物种产生负面影响。
