Cane James H, Minckley Robert L, Kervin Linda J, Roulston T'ai H, Williams Neal M
USDA-ARS Bee Biology and Systematics Laboratory, Department of Biology, Utah State University, Logan, Utah 84322, USA.
Ecol Appl. 2006 Apr;16(2):632-44. doi: 10.1890/1051-0761(2006)016[0632:crwadb]2.0.co;2.
Urbanization within the Tucson Basin of Arizona during the past 50+ years has fragmented the original desert scrub into patches of different sizes and ages. These remnant patches and the surrounding desert are dominated by Larrea tridentata (creosote bush), a long-lived shrub whose flowers are visited by > 120 native bee species across its range. Twenty-one of these bee species restrict their pollen foraging to L. tridentata. To evaluate the response of this bee fauna to fragmentation, we compared species incidence and abundance patterns for the bee guild visiting L. tridentata at 59 habitat fragments of known size (0.002-5 ha) and age (up to 70 years), and in adjacent desert. The 62 bee species caught during this study responded to fragmentation heterogeneously and not in direct relation to their abundance or incidence in undisturbed desert. Few species found outside the city were entirely absent from urban fragments. Species of ground-nesting L. tridentata specialists were underrepresented in smaller fragments and less abundant in the smaller and older fragments. In contrast, cavity-nesting bees (including one L. tridentata specialist) were overrepresented in the habitat fragments, probably due to enhanced nesting opportunities available in the urban matrix. Small-bodied bee species were no more likely than larger bodied species to be absent from the smaller fragments. The introduced European honey bee, Apis mellifera, was a minor faunal element at > 90% of the fragments and exerted little if any influence on the response of native bee species to fragmentation. Overall, bee response to urban habitat fragmentation was best predicted by ecological traits associated with nesting and dietary breadth. Had species been treated as individual units in the analyses, or pooled together into one analysis, these response patterns may not have been apparent. Pollination interactions with this floral host are probably not adversely affected in this system because of its longevity and ability to attract diverse pollinators but will demand careful further study to understand.
在过去50多年里，亚利桑那州图森盆地的城市化进程已将原本的沙漠灌丛分割成大小和年代各异的斑块。这些残留斑块及周边沙漠以三叶拉瑞阿（Larrea tridentata，即牧豆树）为主，它是一种长寿灌木，其花朵在整个分布范围内会被120多种本地蜜蜂光顾。其中有21种蜜蜂将花粉采集限制在三叶拉瑞阿上。为评估这种蜜蜂群落对碎片化的响应，我们比较了在59个已知大小（0.002 - 5公顷）和年代（最长70年）的栖息地斑块以及相邻沙漠中，光顾三叶拉瑞阿的蜜蜂群落的物种发生率和丰度模式。在这项研究中捕获的62种蜜蜂对碎片化的响应各不相同，且与它们在未受干扰沙漠中的丰度或发生率没有直接关系。在城市外发现的少数物种在城市斑块中并未完全消失。地面筑巢的三叶拉瑞阿专家物种在较小斑块中代表性不足，在较小且年代久的斑块中数量较少。相比之下，洞穴筑巢的蜜蜂（包括一种三叶拉瑞阿专家物种）在栖息地斑块中代表性过高，这可能是由于城市基质中筑巢机会增加。小型蜜蜂物种并不比大型蜜蜂物种更有可能在较小斑块中缺失。引入的欧洲蜜蜂（Apis mellifera）在90%以上的斑块中是次要的动物区系成分，对本地蜜蜂物种对碎片化的响应几乎没有影响。总体而言，蜜蜂对城市栖息地碎片化的响应最好通过与筑巢和食性广度相关的生态特征来预测。如果在分析中将物种视为单个单位，或合并到一个分析中，这些响应模式可能并不明显。在这个系统中，与这种花卉寄主的授粉相互作用可能不会受到不利影响，因为它寿命长且有吸引多种传粉者的能力，但仍需要进一步仔细研究以了解情况。
