Aliso: A Journal of Systematic and Floristic Botany Aliso: A Journal of Systematic and Floristic Botany Rarity in Astragalus: a California Perspective Rarity in Astragalus: a California Perspective
Aliso: A Journal of Systematic and Floristic Botany Aliso: A Journal of Systematic and Floristic Botany Rarity in Astragalus: a California Perspective Rarity in Astragalus: a California Perspective
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Aliso：系统和植物区系植物学杂志 Aliso：系统和植物区系植物学杂志 黄芪稀有性：加州视角 黄芪稀有性：加州视角
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通讯作者：
L. Degutis
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作者：
M. Garrettson;H. Weiss;E. McDonald;L. Degutis
黄芪属（豆科）是世界上最大的植物属，估计有3270种，以大量稀有特有种而闻名。对加州黄耆类群的气候、地形和土壤多样性模式（98个本地种和144个命名类群）进行了调查，为了解气候均衡性和区域物种丰富度对稀有性的影响提供了一种手段。该属的大多数分类群具有相对较小的分布范围，其中50%在地理上局限于单一的杰普森生物区。加州本土植物协会将51种黄芪分类群（占本土黄芪分类群的35%）列为稀有、受威胁或濒危（RTE）。地理区域的气候特征，如降雨量和极端温度，与物种丰富度或所列分类群的比例没有明显的关系。物种丰富度是最高的干旱大盆地（35种和53个类群）结合其组成部分，其次是29种和39个类群在塞拉利昂内华达州东部地区，包括白色和Inyo山脉。莫哈韦沙漠的多样性也很高，有32个物种和39个分类群，但相比之下，索诺兰沙漠地区的多样性很低，只有12个物种和14个分类群。尽管在黄芪分类群的数量上排名最高，但与南海岸地区（39.5%）和莫哈韦沙漠（32%）相比，大盆地地区的RTE分类群比例较低（17%）。强土壤专业化与大多数，但不是所有的RTE类群。虽然没有单一的生理生态适应可以解释这种模式，重要的是，黄芪类群具有发展共生固氮的潜在能力，这种特性是在不利于许多潜在竞争对手生长的土壤中取得成功的关键。土地使用的变化、外来草的入侵和放牧，以及其他威胁，正在使许多稀有类群的生境日益破碎化，从而对基因流动产生影响。稀有和地方特有类群的继续生存将需要更好地了解其个人的人口特征和长期的人口动态。
Astragalus (Fabaceae), the largest genus of plants in the world with an estimated 3270 species, is known for large numbers of rare endemic species. An inventory of patterns of climatic, topographic, and edaphic diversity of Astragalus taxa in California (98 native species and 144 named taxa) provides a means to understand the occurrence of rarity in relation to climatic equitability and regional species richness of congeneric taxa. Most taxa in the genus have relatively small ranges of distribution, with 50 % restricted geographically to a single Jepson Bioregion. The California Native Plant Society lists 51 Astragalus taxa (35 % of the native Astragalus taxa) as rare, threatened, or endangered (RTE). Climate characteristics of geographic regions such as rainfall and temperature extremes show no obvious relationship to species richness or the proportion of listed taxa. Species richness is highest in the arid Great Basin (35 species and 53 taxa) combining both its components, followed by 29 species and 39 taxa in the Sierra Nevada East region that includes the White and Inyo Mountains. The Mojave Desert is also high in diversity with 32 species and 39 taxa, but in contrast the Sonoran Desert region is low with only 12 species and 14 taxa. Despite ranking highest in the number of Astragalus taxa present, the Great Basin regions are low in their proportion of RTE taxa (17 % ) compared to the South Coast Region (39.5 % ) and Mojave Desert (32 % ). Strong edaphic specialization is associated with the majority but not all RTE taxa. While no single ecophysiological adaptation can explain this pattern, it is significant that Astragalus taxa have the potential ability to develop symbiotic nitrogen fixation, and this trait is key to success in soils not conducive to growth of many potential competitors. Land use changes, alien grass invasion and grazing, among other threats, are increasing fragmentation of habitats for many rare taxa with consequent impacts on gene flow. The continued survival of rare and locally endemic taxa will require improved knowledge of their individual demographic traits and long-term population dynamics.