Testing for Adaptation of Parasites to Their Local Hosts Hui Li, Eleanore Sternberg, Jacobus C. de Roode Department of Biology, Emor

Abstract Methods Results

Monarch butterflies suffer from infection by the parasite We used 550 eastern monarch butterflies total. Ophryocystis elektroscirrha. Based on the Red Queen Monarchs:y University, Eastern U.S. Atlanta, Population GA 30322 Hypothesis of coevolution, it is supposed that parasites 2 genetically adapt to optimally infect their local hosts. In order to 550 monarchs X = 0.06 F1, 276= 0.05 obtain more evidence on the adaptation of parasites to hosts, df = 1 P-value = 0.82 we aimed to determine in this experiment the infection success P-value = 0.80 of two populations of parasites, one native to Eastern United States and the other native to Hawaii, on monarchs from these 5 eastern US Parasite Clones 6 Hawaiian Parasite Clones 55 Control Monarchs same populations. We hypothesized that the parasites would have higher infection and replication success on monarchs collected from their own local populations. 5 monarch families 5 monarch families We experimentally infected monarch caterpillars from the eastern U.S. and Hawaiian populations with parasites collected from these populations. Once larvae pupated, data were 9 replicates 9 replicates collected on infection status. We also measured parasite replication of the parasites in the monarchs of the Hawaiian In a previous experiment we used 603 Hawaiian population. Our results show that Hawaiian parasites are better monarchs with the same parasites as the eastern at infecting Hawaiian monarchs than eastern US parasites. However, eastern US parasites were not better at infecting monarchs. The experimental design was similar to eastern US monarchs than Hawaiian parasites. Our results also the one described above for eastern monarchs, but th demonstrate that eastern US monarchs are more susceptible to there were 53 extra butterflies from a 6 family. Of Figure 1: Infection probability of Eastern Figure 2: Mean pupal score parasites from both populations than Hawaiian monarchs. these 53, 20 were assigned to eastern parasites, monarchs based on pupal score Overall, results suggest that Hawaiian parasites, but not eastern 22 to Hawaiian parasites, and 11 were controls. US parasites, are adapted to their local hosts. Monarch larvae within families were randomly Monarchs: Hawaiian Population Background assigned to experimental groups. They were reared in individual containers at 26°C with 16 hours of X2 = 94.80 F = 70.06 F1, 332 = 112.94 1, 331 The study of parasitic local adaptation is an important light. Two-day old larvae were infected with parasite df = 1 P-value < 0.001 P-value < 0.001 part of coevolution.1 The Red Queen hypothesis proposes spores, either eastern U.S. or Hawaiian, by feeding P-value <0.001 that there is adaptive genetic variation. Studies on the larvae with a leaf disc with parasite spores. parasites and snails suggest that there is a genetic basis to the success of infections by the parasites in their hosts, and that parasites may be locally adapted to their host genotypes.2

Monarch larvae in petri dishes that contain leaf Monarch butterflies suffer from infection by the parasite discs with spores Ophryocystis elektroscirrha. O. elektroscirrha The larvae underwent larval development and pupation for approximately two to three Butterfly scatters spores on egg and milkweed weeks. Pupal scores, a measure of the

Butterfly emerges covered in spores level of infection in monarch pupa, were taken Larva ingests spores, which lyse in the gut and release during the pupation period of the monarchs. parasites Figure 3: Infection probability of Hawaiian Figure 4: Mean pupal score Figure 5: Spore load of Hawaiian monarchs 3 nuclear divisions yield monarchs based on pupal score a spore with 8 parasites

Parasites penetrate Parasite spore load, a measure of the level of Life cycle of gut wall and infect Meiosis occurs hypodermal cells Ophryocystis elektroscirrha infection in adult monarchs, was counted on the in the monarch butterfly butterflies from the Hawaiian population after they

…to form a zygote had died. Analysis was done using ANOVA on Conclusion 2 …and pair… Parasites continuous variables and X test on categorical replicate and burst out of cells outcome variables.. Parasites round up… Parasites mature in hypoderm and Parasites replicate •There was a significant difference between the infection probability and parasite replication of the eastern and Hawaiian hemolymph once more parasites in the Hawaiian monarch population. References • However, there was no significant difference between the infection probability and parasite replication of the eastern and In a previous experiment on monarch butterflies from the 1. Greischar, M.A. & Koskella, B. (2007) A synthesis of Hawaiian parasites in the monarchs of the eastern U.S. population. eastern U.S. and western U.S. (Californian) populations, experimental work on parasite local adaptation. Ecology • Eastern U.S. monarchs are more susceptible to parasites from both populations than Hawaiian monarchs. the results showed that there is no significant difference Letters, 10, 418-434. •This suggests that there is local adaptation of parasites from the Hawaiian population, but not of parasites from the eastern between the interactions of parasites with their local population. monarch hosts and those of parasites with other 2. Lively, C.M. (1989) Adaptation by a parasitic trematode populations of monarchs.3 to local populations of its snail host. Evolution, 43, 1663- 1671.

In this experiment, we attempt to determine whether there 3. De Roode, J.C. & Altizer, S. (2010) Host-parasite genetic Acknowledgements is local adaptation by parasites from more geographically interactions and virulence-transmission relationships in distant populations, eastern U.S. and Hawaiian, to the hosts natural populations of monarch butterflies. Evolution, 64, We thank Rachel Rarick, Ashley Darar, and Yamini Potini for their help in conducting the experiment. We also thank the Howard of O. elektroscirrha. 502-514. Hughes Medical Institute, Grant No. 52005873.