Ward David, Seely Mary K
Desert Ecological Research Unit of Namibia, Gobabeb, P.O. Box 1592, Swakopmund 9000, Namibia.
Evolution. 1996 Jun;50(3):1231-1240. doi: 10.1111/j.1558-5646.1996.tb02363.x.
A comparative phylogenetic approach was used to test the following adaptive hypotheses pertaining to the physiological abilities of the Namib desert tenebrionid beetle genus Onymacris to withstand the hot, dry desert environment: (1) Desert-interior species evolved longer legs (relative to body size) than beetles in the cooler coastal region to facilitate stilting, i.e., elevating their bodies out of the hot boundary layer of air close to the substrate. (2) Wax blooms on the exoskeleton, which reduce evaporative water loss, are more likely to evolve in desert-interior species than in coastal species. (3) The high costs of activity in the extreme climates select for perfect coadaptation of preferred body temperatures (i.e., optimal temperatures for activity) and those they achieve in the field. All three of these adaptive hypotheses were supported by the results of squared-change parsimony and independent-contrasts analyses. Additionally, a parsimony approach suggested that a novel means of obtaining water from periodic fogs, known as fog basking, has evolved independently on two occasions.
（1）与较凉爽沿海地区的甲虫相比，沙漠内部的物种进化出了更长的腿（相对于体型），以便于高跷式行走，即将身体抬高到靠近基质的热空气边界层之上。（2）外骨骼上的蜡质层可减少水分蒸发损失，沙漠内部物种比沿海物种更有可能进化出蜡质层。（3）极端气候下的高活动成本促使偏好体温（即活动的最佳温度）与它们在野外实际达到的体温实现完美协同适应。平方变化简约法和独立对比分析的结果支持了所有这三个适应性假说。此外，一种简约法表明，一种从周期性雾中获取水分的新方法，即雾浴，已在两种情况下独立进化出来。
