Using molecular tools to predict invasion potential in the family Cerambycidae

Kapil R Raje, Purdue University

Abstract

With the surges in international trade, the threat of invasive wood-boring longhorned beetles continues to increase. These beetles could potentially cause damage worth hundreds of millions of dollars as has been demonstrated by the Asian longhorned beetle. While we cannot conduct realistic invasion experiments, we can study the behavioral traits of the native longhorned beetles. The longhorned beetles are a good study group of potential invaders because their diversity results in great variation in biological and behavioral traits. The aims of this project were to construct a molecular phylogeny of the longhorned beetles that are native to the Midwestern U.S. and to map biological and behavioral traits onto this phylogeny. During the first step of collecting the beetles we set up traps on private forest lands. We studied the relationship between forest productivity and longhorned beetle communities. Our results suggest that the numbers of both the pest and the harmless species increase with decreasing forest productivity. Chapter 1 deals with this change in communities with forest health. Chapter 2 deals with the species Sternidius alpha, which is common in the eastern part of the United States. Two populations of Sternidius alpha that differed in color were collected from two geographically disjunct Indiana sites. One population was red and the other gray. The technique of DNA barcoding employed in our laboratory separated the red and gray beetles into different phylogenetic clades. In Chapter 3, a phylogeny of all the longhorned beetle species collected was inferred based on partial DNA sequences from two mitochondrial genes: 12S ribosomal RNA and cytochrome oxidase subunit I. Maximum Likelihood and Bayesian inferences were used for building a phylogenetic tree. All of the subfamilies in the family Cerambycidae were monophyletic, which supports the delineation of the subfamilies based on morphological characters. An unexpected result, however, was the placement of the subfamily Prioninae, as a derived sister of the subfamily Cerambycinae. This contrasts with the previous finding that suggest Prioninae is basal to most of the remaining subfamilies of the Cerambycidae. Also, the subfamily Lamiinae, thought to be a sister to the subfamily Cerambycinae on the tree based on morphology, did not have a sister subfamily on the molecular tree. In Chapter 4, an ultrametric Bayesian algorithm was used to reconstruct the ancestral states on the phylogenetic tree of the longhorned beetles. This analysis showed that the inferred ancestral longhorned beetle was probably a polyphagous feeder as a larva on long dead and decaying angiosperms and non-feeding as an adult. As the lineages diversified over time this ancestral biology gave rise to other traits as well, although some species retained the traits that the ancestor displayed. In Chapter 5, the ultrametric Bayesian tree was used to calculate the extent of phylogenetic signal in the phylogenetic tree for various biological traits. The phylogenetic signal was strong for the following traits: host condition for larval feeding, adult feeding behavior, plant part attacked, the plant tissue attacked and the utilization of angiosperms or gymnosperms. The presence of phylogenetic signal in the first four traits was used to build a threat index to predict which newly introduced species could be capable of becoming invasives. Study of the invasion-promoting traits among native species can be useful in predicting which of the relatives of the native species are likely to share a suite of traits that could enable them to become invasive.

Degree

Ph.D.

Advisors

Ferris, Purdue University.

Subject Area

Entomology

COinS