Reeve John D, Anderson Frank E, Kelley Scott T
Department of Zoology, Southern Illinois University, Carbondale, IL 62901, USA.
Environ Entomol. 2012 Jun;41(3):723-30. doi: 10.1603/EN11281.
While most bark beetles attack only dead or weakened trees, many species in the genus Dendroctonus have the ability to kill healthy conifers through mass attack of the host tree, and can exhibit devastating outbreaks. Other species in this group are able to successfully colonize trees in small numbers without killing the host. We reconstruct the evolution of these ecological and life history traits, first classifying the extant Dendroctonus species by attack type (mass or few), outbreaks (yes or no), host genus (Pinus and others), location of attacks on the tree (bole, base, etc.), whether the host is killed (yes or no), and if the larvae are gregarious or have individual galleries (yes or no). We then estimated a molecular phylogeny for a data set of cytochrome oxidase I sequences sampled from nearly all Dendroctonus species, and used this phylogeny to reconstruct the ancestral state at various nodes on the tree, employing maximum parsimony, maximum likelihood, and Bayesian methods. Our reconstructions suggest that extant Dendroctonus species likely evolved from an ancestor that killed host pines through mass attack of the bole, had individual larvae, and exhibited outbreaks. The ability to colonize a host tree in small numbers (as well as gregarious larvae and attacks at the tree base) apparently evolved later, possibly as two separate events in different clades. It is likely that tree mortality and outbreaks have been continuing features of the interaction between conifers and Dendroctonus bark beetles.
虽然大多数树皮甲虫只攻击死树或衰弱的树，但齿小蠹属的许多物种有能力通过大规模攻击寄主树来杀死健康的针叶树，并能引发毁灭性的虫灾。该类群中的其他物种能够少量成功地在树上定殖而不杀死寄主。我们重建了这些生态和生活史特征的演化过程，首先根据攻击类型（大规模或少量）、虫灾（有或无）、寄主属（松属和其他属）、在树上的攻击位置（树干、基部等）、寄主是否被杀死（是或否）以及幼虫是群居还是有单独的虫道（是或否）对现存的齿小蠹物种进行分类。然后，我们为从几乎所有齿小蠹物种中采样的细胞色素氧化酶I序列数据集估计了一个分子系统发育树，并使用这个系统发育树，采用最大简约法、最大似然法和贝叶斯方法，重建树上各个节点的祖先状态。我们的重建结果表明，现存的齿小蠹物种可能是从一个通过大规模攻击树干杀死寄主松树、幼虫单独生活且会引发虫灾的祖先演化而来的。少量定殖寄主树的能力（以及群居幼虫和在树基部的攻击）显然是后来演化出来的，可能是在不同分支中的两个独立事件。树木死亡和虫灾很可能一直是针叶树与齿小蠹树皮甲虫相互作用的特征。
