Colorado potato beetle
The Colorado potato beetle (Leptinotarsa decemlineata) is also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle, or the potato bug. It is a major pest of potato crops. It is about 10 mm (3⁄8 in) long, with a bright yellow/orange body and five bold brown stripes along the length of each of its elytra. Native to the Rocky Mountains, it spread rapidly in potato crops across America and then Europe from 1859 onwards.[3]
"Potato beetle" redirects here. Not to be confused with the three-lined potato beetle, Lema daturaphila.The Colorado potato beetle was first observed in 1811 by Thomas Nuttall and was formally described in 1824 by American entomologist Thomas Say.[3] The beetles were collected in the Rocky Mountains, where they were feeding on the buffalo bur, Solanum rostratum.[4]
Native range of the potato and native and current range of the Colorado beetle
Expansion of the Colorado potato beetle's range in North America, 1859–1876
Expansion of the Colorado potato beetle's range in Europe, 1921–1964
Eggs laid on the underside of a leaf
1st instar larva after hatching
3rd instar stage of larvae
4th instar stage of larva, before pupation
Pupa
Adult beetle after emergence
Mating adult beetles
Behavior and ecology[edit]
Diet[edit]
L. decemlineata has a strong association with plants in the family Solanaceae, particularly those of the genus Solanum. It is directly associated with Solanum cornutum (buffalo-bur), Solanum nigrum (black nightshade), Solanum melongena (eggplant or aubergine), Solanum dulcamara (bittersweet nightshade), Solanum luteum (hairy nightshade), Solanum tuberosum (potato), and Solanum elaeagnifolium (silverleaf nightshade). They are also associated with other plants in this family, namely the species Solanum lycopersicum (tomato) and the genus Capsicum (pepper).[23]
Genetics[edit]
Genetic differentiation from agriculture[edit]
Colorado potato beetles display genetic differentiation based on region. In the Columbia Basin and Central Sands, beetles in the Columbia Basin had less genetic diversity than those in Central Sands. According to the study done by Crossly, Rondon, and Schoville, in the paper Effects of contemporary agricultural land cover on Colorado potato beetle genetic differentiation in the Columbia Basin and Central Sands, nucleotide diversity in the Columbia Basin beetles ranged from 0.0056-0.0063 and 0.0073-0.0080 in Central Sands. Heterozygosity data showed the Columbia Basin was 19.4% ± 0.4% and 21.6% ± 0.8% in the Central Sands.[38] Additional mitochondrial DNA sequencing showed two haplotypes in the Columbia Basin compared to places like Wisconsin showed seven haplotypes.
Reasoning behind the genetic diversity is the landscapes of the regions: shrub-land and grains in the Columbia Basin versus the forest, corn, and beans in the Central Sands. In the same study, potatoes covered 3.5% in the Columbia Basin and 1.8% in the Central Sands.[38] Landscape resistance can be characterized by how the land responds to the spread of beetles. Its overall effect on allele frequency covariance was low, and the Central Sands had a higher rate of decay in allele frequency. Potatoes' relative effect sizes of land cover variables on genetic differentiation was the highest in the Columbia Basin. However, when comparing all the land types, no particular land cover displayed any significant difference from the others.[39]
Genetic differentiation in the Colorado potato beetle can be impacted by agricultural practices such as crop rotation. The same study mentioned earlier examines crop rotation's effects on genetic differentiation in Colorado potato beetles that were not found in the Central Sands. On the other hand, genetic diversity decreased with increased crop rotation in the Columbia Basin.[38] This difference could be attributed to larger rotation differences in the Columbia Basin or differences in the landscape itself that affect the spread of the beetles. Genetic diversity is not directly impacted by the land cover type. Instead, other factors such as climate could be responsible for the differences between the Colorado potato beetle in these two regions.[38]
Genetic differentiation due to invasion[edit]
The Colorado potato beetle has invaded North America and Europe. Because of its widespread invasion, the Colorado potato beetle displays genetic diversity in its different regions. In the paper The voyage of an invasive species across continents: genetic diversity of North American and European Colorado potato beetle populations by Grapputo, Boman, Lindström, and Mappes, sequencing of amplified mtDNA from 109 beetles in 13 populations showed 20 unique haplotypes.[40] Three haplotypes were shared in the populations and all others were restricted to a single population in North America. 51 European beetles collected from eight populations yielded in one haplotype that was also fixed in the Idaho population.[40] Mitochondrial data, mtDNA, of North American beetles showed significant population differentiation. For example, 44% of the variation can be attributed to subdivision among populations, especially in Kentucky and Idaho.[40]
Polymorphism was highest in Colorado potato beetles in Colorado and the lowest was in France. Polymorphism and heterozygosity was higher in North America than in Europe. Heterozygosity ranged from 0.25 in New Brunswick to 0.14 in France.[40] Further analysis revealed population differentiations between North America and Europe. There were two separate groups of European beetles, one formed by western European beetles and the second being eastern European beetles. 13% of total variation is from variation among the two continent groups, and 17% of variation is from population variance within groups.[40] Beetles from North American and Europe formed clusters. With the exception of New Brunswick and Kentucky beetles, most beetles from the same population cluster together. In Europe, there were more complex relations between the beetles. Estonian and Spanish beetles clustered, French and Italian beetles formed separate groups, and Russian and Finnish beetles were closely related to Estonian ones.[40] European beetles could be categorized by East and West except for Polish beetles which had relations to multiple countries.[40]
Importance of transposable elements in genome[edit]
To help explain why Colorado Potato beetles are such difficult agricultural pests to manage and control, a group of researchers sought to test both structural and functional genetic changes in the species of beetle as compared to other arthropod species. Using community annotation, transcriptomics, and genome sequencing, they uncovered that Colorado Potato beetles have a genome consisting of several transposable elements.[41] Transposons are sequences of genetic material that can shift/move their place within an organism's genome, and 17% of the Colorado Potato beetles’ genome consists of transposable elements.[41] This helps explain their rapid evolution to continually resist insecticides, contributing to their global spread.