Krasnov Boris R, Shenbrot Georgy I, Khokhlova Irina S, Poulin Robert
Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede-Boqer Campus, 84990, Midreshet Ben-Gurion, Israel.
Oecologia. 2006 Nov;150(1):132-40. doi: 10.1007/s00442-006-0498-9. Epub 2006 Aug 4.
Population density is a fundamental property of a species and yet it varies among populations of the same species. The variation comes from the interplay between intrinsic features of a species that tend to produce repeatable density values across all populations of the same species and extrinsic environmental factors that differ among localities and thus tend to produce spatial variation in density. Is inter-population variation in density too large for density to be considered a true species character? We addressed this question using data on abundance (number of parasites per individual host, i.e. equivalent to density) of fleas ectoparasitic on small mammals. The data included samples of 548 flea populations, representing 145 flea species and obtained from 48 different geographical regions. Abundances of the same flea species on the same host species, but in different regions, were more similar to each other than expected by chance, and varied significantly among flea species, with 46% of the variation among samples accounted by differences between flea species. Thus, estimates of abundance are repeatable within the same flea species. The same repeatability was also observed, but to a lesser extent, across flea genera, tribes and subfamilies. Independently of the identity of the flea species, abundance values recorded on the same host species, or in the same geographical region, also showed significant statistical repeatability, though not nearly as strong as that associated with abundance values from the same flea species. There were also no strong indications that regional differences in abiotic variables were an important determinant of variation in abundance of a given flea species on a given host species. Abundance thus appears to be a true species trait in fleas, although it varies somewhat within bounds set by species-specific life history traits.
种群密度是一个物种的基本属性，但同一物种的不同种群之间其密度会有所不同。这种差异源于物种内在特征与外部环境因素之间的相互作用，物种的内在特征往往会在同一物种的所有种群中产生可重复的密度值，而外部环境因素在不同地区存在差异，从而往往会导致密度出现空间变化。种群间密度的差异是否太大以至于密度不能被视为一个真正的物种特征呢？我们利用小型哺乳动物体表寄生跳蚤的丰度数据（每个宿主个体上的寄生虫数量，即等同于密度）来解决这个问题。这些数据包括548个跳蚤种群的样本，代表145种跳蚤，取自48个不同的地理区域。同一宿主物种上的同一种跳蚤，在不同地区的丰度彼此之间比随机预期的更为相似，并且在不同跳蚤物种之间差异显著，样本间46%的变异是由跳蚤物种之间的差异造成的。因此，丰度估计在同一种跳蚤内是可重复的。在跳蚤的属、族和亚科层面也观察到了同样的可重复性，只是程度稍低。不管跳蚤物种的身份如何，在同一宿主物种上或同一地理区域记录的丰度值也显示出显著的统计可重复性，尽管远不如同一种跳蚤的丰度值之间的相关性那么强。也没有有力迹象表明非生物变量的区域差异是给定宿主物种上给定跳蚤物种丰度变异的重要决定因素。因此，丰度似乎是跳蚤的一个真正物种特征，尽管它在特定物种的生活史特征所设定的范围内会有所变化。
