Literature Review: Leaf Mine Diversity

by Carl Strang

This week’s literature focus is on a paper that provided information suggesting why leaf miners produce such diverse mine structures.

Leaf miners are larval insects so tiny that they fit between the upper and lower leaf surfaces, feeding on the tissues in between. This example is a twisting linear mine on Heracleum.

Leaf miners are larval insects so tiny that they fit between the upper and lower leaf surfaces, feeding on the tissues in between. This example is a twisting linear mine on Heracleum.

Ayabe Y, Ueno T (2012) Complex Feeding Tracks of the Sessile Herbivorous Insect Ophiomyia maura as a Function of the Defense against Insect Parasitoids. PLoS ONE 7(2): e32594. doi:10.1371/journal.pone.0032594

They looked at linear mines in a fly that develops in a French aster. In their review they mention research that has been done on various mine forms and how they may deter parasitoids. Parasitoids focus mainly on the upper leaf surface, so lower surface mines (including tentiform mines of Phyllonorycter moth caterpillars in some of our local plants) provide some protection, and upper surface miners sometimes shift to the lower surface to pupate. Blotch mines provide more escape space for their occupants. In this study they found that complex linear mines, especially ones that have branches and crossing tunnels, reduce parasitoid effectiveness.

We can see a wide range of leaf mine types on our local plants.

Expanded blotch-type mine on poison ivy (the leaves aren’t always 3 leafleted!).

Expanded blotch-type mines on poison ivy (the leaves aren’t always 3 leafleted!).

The outline of a tentiform mine shows on this maple leaf. The mine is on the underside of the leaf, not readily reached from above.

The outline of a tentiform mine shows on this maple leaf. The mine is on the underside of the leaf, not readily reached from above.

According to this research, it boils down to a game of hide-and-seek. If a leaf miner can make its mine complex enough, or in a place where it is difficult to reach, or expand the mine to the point where finding the miner is somewhat needle-in-haystackish, it gains an advantage over the insects that would parasitize and kill it. Furthermore, the diversity of mine types provides a more complex evolutionary puzzle for the parasites as a whole to solve.

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