Ancestral state reconstruction for Dendroctonus bark beetles: evolution of a tree killer.
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.
Department of Zoology, Southern Illinois University, Carbondale, IL 62901, USA. jreeve@zoology.siu.edu
John D
JD
Reeve
Frank E
FE
Anderson
Scott T
ST
Kelley
D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D003576:Electron Transport Complex IV / Q000235:genetics; D019143:Evolution, Molecular; D060434:Herbivory; D019476:Insect Proteins / Q000235:genetics; D007814:Larva / Q000033:anatomy & histology / Q000145:classification / Q000502:physiology; D016013:Likelihood Functions; D008390:Markov Chains; D010802:Phylogeny; D012919:Social Behavior; D014197:Trees; D048889:Weevils / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics* / Q000502:physiology
D019476:Insect Proteins; D003576:Electron Transport Complex IV