Price Mary V, Podolsky Robert H
Department of Biology, University of California, 92521, Riverside, CA, USA.
Oecologia. 1989 Oct;81(2):267-273. doi: 10.1007/BF00379814.
Several lines of evidence show that soil texture plays an important role in the distribution of desert-dwelling heteromyid rodents. This is not surprising, since texture influences the energetic cost of digging burrows and of scratching at the soil surface to harvest buried seeds. Texture also may influence the efficiency with which seeds can be separated from the soil particles with which they are mixed. To explore mechanisms of "particle separation" by foraging heteromyids we measured seed harvest rates and size selection in the laboratory for a variety of seed sizes and soil textures. Harvest rate declined with increasing soil coarseness, and the preference for seeds of intermediate size that was apparent in fine soil disappeared when seeds were mixed with soil slightly coarser than the preferred seed size. In addition, there was evidence that particle separation efficiency is sensitive to the relative sizes of seeds and soil. A discontinity in the function relating harvest rate to soil texture occurred at finer soil textures for small seeds than for large seeds, suggesting that harvest techniques change once soil particle diameter equals or exceeds that of seeds. These results are consistent with the hypothesis that heteromyids use a combination of gravity-and rake-sorting mechanisms for particle separation.
有几条证据表明，土壤质地在沙漠穴居异鼠科啮齿动物的分布中起着重要作用。这并不奇怪，因为质地会影响挖掘洞穴以及在土壤表面抓挠以获取埋藏种子的能量消耗。质地还可能影响种子与混合在一起的土壤颗粒分离的效率。为了探究觅食的异鼠科动物进行“颗粒分离”的机制，我们在实验室中针对各种种子大小和土壤质地测量了种子收获率和大小选择。随着土壤粗糙度增加，收获率下降，并且当种子与比首选种子大小稍粗的土壤混合时，在细土中明显的对中等大小种子的偏好消失了。此外，有证据表明颗粒分离效率对种子和土壤的相对大小敏感。对于小种子，收获率与土壤质地之间的函数关系在较细的土壤质地处出现间断，而对于大种子则不然，这表明一旦土壤颗粒直径等于或超过种子直径，收获技术就会改变。这些结果与异鼠科动物使用重力分选和耙式分选机制相结合进行颗粒分离的假设一致。
