Genetic Basis and Effect of Diet on Color Polymorphism in the Diaprepes Root Weevil
Subtropical Insects and Horticulture Research
Project Number: 6034-22320-004-08
Nonfunded Cooperative Agreement
Start Date: Sep 01, 2013
End Date: Aug 31, 2018
Understand the genetic basis for phenotypic variability in the Diaprepes root weevil, an agricultural pest whose larvae and adults feed on >300 plant species. Diaprepes causes damage to citrus through root feeding and by facilitating infection by soil-borne pathogens. Adult color is highly variable, including red, orange, yellow, white, grey and brown. The objective is to evaluate the origin of color variation in Diaprepes. Color may be associated with biogeographical variables, host plant interactions, or genetic factors. We will evaluate two hypotheses. Color variation may be associated with plant secondary chemicals found in larval or adult diet. Musum collection data and field collections support this hypothesis. Most museum specimens collected between 1948 and 2007 do not include host plant data; those that do show a possible relation between color and plant host. Over 500 specimens collected on five non-citrus plants included all colors except red. Recent sampling suggests that red individuals are only found on citrus; nevertheless the sample size is too small to allow conclusions. Genetic factors may also be responsible for color; color may be an inheritable trait. A phylogeny based on mtDNA data obtained from GenBank produced three groups consisting of specimens from (1) Dominica, (2) the Dominican Republic and western Puerto Rico, and (3) Puerto Rico, Florida and the Dominican Republic. The phylogenic analysis suggests there may be variables other than biogeographical factors separating populations; color differences may explain phylogenetic structure. By evaluating the origin of color variation, this study will contribute to understanding phenotypic variability, distribution and recent movement of D. abbreviatus. Host plant information will aid in the decision making process related to control.
ARS has developed rearing methods and artificial diets for the Diaprepes root weevil. Inter American University of Puerto Rico will collect and maintain colonies of phenotypically diverse populations and study the effect of diet and crossing on phenotypic expression. Inter American University of Puerto Rico will perform a feeding preference experiment. Adults of different colors will be offered plants different from those they were collected on to evaluate food specificity in association with color. Inter American University of Puerto Rico
will amplify three genes (COI, EF1-a and 16S rRNA) from individuals of different colors and localities. The sequences will be aligned and phylogenies will be constructed based on these data and information obtained from GenBank.