The influence of a competitor on the geographic mosaic of coevolution between crossbills and lodgepole pine
The influence of a competitor on the geographic mosaic of coevolution between crossbills and lodgepole pine
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DOI：
10.1111/j.0014-3820.2001.tb01293.x
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发表时间：
2001-02-01
期刊：
影响因子：
3.3
通讯作者：
Smith, JW
中科院分区：
文献类型：
--
作者：
Benkman, CW;Holimon, WC;Smith, JW
共同进化的地理镶嵌理论假定，相互作用的物种之间的选择形式在景观中变化，共同进化在某些地方是重要和活跃的（即，共同进化热点）而不是在其它热点（即，coevolutionary coldspots）。我们测试的假设，即红松鼠（Tamiasciurus hudsonicus）的存在影响发生的共同进化之间的红交嘴鸟（Loxia curvirostra复杂）和落基山lodgepole松（松扭叶松ssp。宽叶），从而提供了一种机制，产生了地理选择镶嵌。红松鼠是火炬松球果的主要种子捕食者和选择剂。然而，在落基山脉东部和西部的四个孤立的山脉中，红松鼠缺席，红交嘴鸟是主要的传播前种子捕食者。这些孤立的松树种群显然已经在没有Tamiasciurus的情况下进化了大约10,000到12,000年。根据已发表的形态，遗传和古植物学研究，我们推断，这些孤立的人群，显示平行的差异，在落基山脉的锥性状发生了平行变化。我们使用的数据crossbill和针叶树锥形态和喂养的喜好和效率，以检测是否红交嘴和黑松表现出相互适应，这将意味着共同进化。锥性状，以阻止Tamiasciurus，并导致高比例的锥质量，种子质量不发达的隔离人群。锥性状，以阻止交喙包括更大，更厚的鳞片，也许连续鳞片之间的重叠增加，并在隔离的人群中得到增强。在较大的、孤立的山脉中，交嘴鸟进化得更深、更短，因此也更下弯，以利用这些锥体。这为交嘴雀提供了更高的进食率，并且通过减少伴随的体重和每日能量消耗的增加，嘴形状的改变提高了效率，如果只增加嘴的大小，就会导致体重和每日能量消耗的增加。红交嘴雀和黑松的这些平行适应和反向适应被解释为相互适应，并暗示这些交嘴雀和黑松处于共同进化的军备竞赛中，而红松鼠缺席（即，共同进化的热点）而不是红松鼠存在的地方（即，coevolutionary coldspots）。
The geographic mosaic theory of coevolution posits that the form of selection between interacting species varies across a landscape with coevolution important and active in some locations (i.e., coevolutionary hotspots) but not in others (i.e., coevolutionary coldspots). We tested the hypothesis that the presence of red squirrels (Tamiasciurus hudsonicus) affects the occurrence of coevolution between red crossbills (Loxia curvirostra complex) and Rocky Mountain lodgepole pine (Pinus contorta ssp. latifolia) and thereby provides a mechanism giving rise to a geographic mosaic of selection. Red squirrels are the predominant predispersal seed predator and selective agent on lodgepole pine cones. However, in four isolated mountain ranges east and west of the Rocky Mountains, red squirrels are absent and red crossbills are the main predispersal seed predator. These isolated populations of pine have apparently evolved without Tamiasciurus for about 10,000 to 12,000 years. Based on published morphological, genetic, and paleobotanical studies, we infer that cone traits in these isolated populations that show parallel differences from cones in the Rocky Mountains have changed in parallel. We used data on crossbill and conifer cone morphology and feeding preferences and efficiency to detect whether red crossbills and lodgepole pine exhibit reciprocal adaptations, which would imply coevolution. Cone traits that act to deter Tamiasciurus and result in high ratios of cone mass to seed mass were less developed in the isolated populations. Cone traits that act to deter crossbills include larger and thicker scales and perhaps increased overlap between successive scales and were enhanced in the isolated populations. In the larger, isolated mountain ranges crossbills have evolved deeper, shorter, and therefore more decurved bills to exploit these cones. This provides crossbills with higher feeding rates, and the change in bill shape has improved efficiency by reducing the concomitant increases in body mass and daily energy expenditures that would have resulted if only bill size had increased. These parallel adaptations and counter adaptations in red crossbills and lodgepole pine are interpreted as reciprocal adaptations and imply that these crossbills and pine are in coevolutionary arms races where red squirrels are absent (i.e., coevolutionary hotspots) but not where red squirrels are present (i.e., coevolutionary coldspots).