Data from: Do pathogens reduce genetic diversity of their hosts? Variable effects of sylvatic plague in black-tailed prairie dogs

Introduced diseases can cause dramatic declines in—and even the loss of—natural populations. Extirpations may be followed by low recolonization rates, leading to inbreeding and a loss of genetic variation, with consequences on population viability. Conversely, extirpations may create vacant habitat patches that individuals from multiple source populations can colonize, potentially leading to an influx of variation. We tested these alternative hypotheses by sampling 15 colonies in a prairie dog metapopulation during 7 years that encompassed an outbreak of sylvatic plague, providing the opportunity to monitor genetic diversity before, during and after the outbreak. Analysis of nine microsatellite loci revealed that within the metapopulation, there was no change in diversity. However, within extirpated colonies, patterns varied: In half of the colonies, allelic richness after recovery was less than the preplague conditions, and in the other half, richness was greater than the preplague conditions. Finally, analysis of variation within individuals revealed that prairie dogs present in recolonized colonies had higher heterozygosity than those present before plague. We confirmed plague survivorship in six founders; these individuals had significantly higher heterozygosity than expected by chance. Collectively, our results suggest that high immigration rates can maintain genetic variation at a regional scale despite simultaneous extirpations in spatially proximate populations. Thus, virulent diseases may increase genetic diversity of host populations by creating vacant habitats that allow an influx of genetic diversity. Furthermore, even highly virulent diseases may not eliminate individuals randomly; rather, they may selectively remove the most inbred individuals.

传入型疫病可引发自然种群的剧烈衰退，甚至彻底消亡。局地集群灭绝后若重新定殖率偏低，则会引发近交与遗传多样性丧失，进而影响种群存续能力。反之，局地集群灭绝也可能形成空置生境斑块，可供多个源种群的个体定殖，进而有可能带来遗传变异的流入。本研究针对一场覆盖7年的丛林鼠疫（sylvatic plague）暴发事件，对草原犬鼠（prairie dog）集合种群（metapopulation）中的15个集群开展采样，以此验证上述两种对立假说，借此实现对该种群在鼠疫暴发前、暴发中及暴发后的遗传多样性监测。对9个微卫星位点（microsatellite loci）的分析结果显示，整个集合种群的遗传多样性未出现显著变化。但局地灭绝的集群的遗传多样性变化模式存在差异：其中半数集群在恢复后的等位基因丰富度低于鼠疫暴发前水平，另一半则高于疫前水平。此外，个体水平的遗传变异分析显示，重新定殖集群内的草原犬鼠的杂合度显著高于鼠疫暴发前的种群个体。我们确认了6只奠基个体在鼠疫中存活，这些个体的杂合度显著高于随机预期水平。综合而言，本研究结果表明：即便邻近种群同时发生局地集群灭绝，高迁入率仍可维持区域尺度的遗传多样性。由此可见，强致病性疫病可通过形成空置生境、引入外来遗传变异，提升宿主种群的遗传多样性。此外，即便高致病性疫病也并非随机清除宿主个体，反而可能选择性移除近交程度最高的个体。