Fowler Norma L, Clay Keith
Department of Botany, University of Texas, 78713, Austin, TX, USA.
Department of Biology, Indiana University, 47405, Bloomington, IN, USA.
Oecologia. 1995 Jul;103(1):55-62. doi: 10.1007/BF00328425.
This study investigated the demographic consequences of fungal infection of a perennial grass, Stipa leucotricha. The rate of parasitism of this grass by the host-specific, systemic fungus Atkinsonella texensis varies over short distances. Infection was frequent (57% of plants) in "mottes" (clusters of woody plants) but rarer in adjacent open grasslands (9%). To test the hypothesis that the relative performance of infected and uninfected plants differed in the two habitats, infected and uninfected genotypes were collected from mottes in a central Texas population, propagated in the green-house and then transplanted into the same site in replicate plots within mottes, at the edges of mottes, and in open grassy areas. Demographic data were recorded for 30 months over three growing seasons. Plants were observed to lose and gain infection. Infection had no significant effect on plant survival, tiller number or dry mass although infected plants tended to be larger. Uninfected plants had a significantly higher probability of setting seed but there were no differences in seed production by reproductive plants. There were significant effects of planting environment on all of these measures. Motte edges were most favorable for S. leucotricha transplants while motte interiors were least favorable and open areas were intermediate. There was no evidence of habitat x infection interactions; therefore the fungal infection had similar effects in different habitats. The high frequency of infection in motte habitats is best explained by more efficient contagious spread there. The favorability of motte edges for plant growth is substantially offset by higher infection rates at the edges of mottes.
本研究调查了一种多年生草本植物——白刺针茅（Stipa leucotricha）真菌感染后的种群统计学后果。宿主特异性的系统性真菌——德克萨斯阿特金森菌（Atkinsonella texensis）对白刺针茅的寄生率在短距离内存在差异。在“小块林地”（木本植物群落）中，这种草的感染频率很高（57%的植株），而在相邻的开阔草地中则较为罕见（9%）。为了验证在这两种生境中，受感染和未受感染植株的相对表现存在差异这一假设，从德克萨斯州中部一个种群的小块林地中采集了受感染和未受感染的基因型植株，在温室中进行繁殖，然后分别移栽到小块林地内部、小块林地边缘和开阔草地的重复样地中。在三个生长季节里记录了30个月的种群统计学数据。观察到植株会感染和清除感染。感染对植株存活数、分蘖数或干重没有显著影响，不过受感染植株往往更大。未受感染植株结籽的概率显著更高，但繁殖植株的种子产量没有差异。种植环境对所有这些指标都有显著影响。小块林地边缘对白刺针茅移栽最为有利，小块林地内部最不利，开阔区域则处于中间水平。没有证据表明生境与感染之间存在相互作用；因此，真菌感染在不同生境中的影响相似。小块林地生境中感染频率较高，最合理的解释是那里的传染性传播更有效。小块林地边缘对植物生长的有利性被边缘更高的感染率大大抵消了。
