One species of moth can subsist on a particular plant type, while another can’t. Why? Katja Hora has been exploring the way in which ermine moths choose their host plant and, more in particular, the genetic architecture underpinning that choice. Hora will receive her doctorate from the University of Amsterdam (UvA) on Wednesday, 24 September.
The ermine moth (Yponomeuta) is a family of moths of which nine different species are found in the Netherlands, each of which subsists on only one or a small handful of host plants. Caterpillars of each species also never eat each other's food plants, even if it leads to starvation.
Hora studied the rigid plant choices of the ermine moth and discovered that genetic architecture plays an important role. Certain genes 'tell' the ermine moth whether a given plant is or is not a suitable host. To trace the specific genes involved, Hora cross-bred various species of ermine moth. This led to a new generation of caterpillars that inherited one full set of genes from each parent. The information in those genes enabled these first-generation caterpillars to feed equally well on the host plants of both parents. However, a second crossing within this generation led to caterpillars that rarely inherited the full genomic information. In fact, these hybrid moths were not able to feed on either of the previous generation's host plants.
By cross-breeding in this way, Hora found that the ermine moth's preference for a specific host plant is encoded in a number of genes. Adult females choose a plant on which to lay their eggs based on information in certain genes, while another set of genes then tell the caterpillar which plant to eat. In the hybrid caterpillars, it appeared that a set of at least three genes had to be passed on from the parents in order for the offspring to be able to subsist on one of the parental host plants.
Evolutionary biologists are attempting to discover whether when insects switch to a different host plant, this is due to chance mutations following a change in the insect's or plant's habitat, or if insects make such transitions without spatial divisions. Hora's work contributes to a better understanding of the general basic mechanisms driving host plant-switching and species development. Such research provides valuable insight into how insects live in agricultural and horticultural areas and how host plant-switching among such insects can pose a threat to human food security.
Roos K.H. Hora: Genetic Architecture of Host Use in Yponomeuta. Supervisor: Prof. S.B.J. Menken. Co-supervisor: Dr P. Roessingh.
The doctoral thesis defence ceremony will take place on Wednesday, 24 September, at 10:00. Location: Agnietenkapel, Oudezijds Voorburgwal 231, Amsterdam.