Butterflies and Host Plants

1. Butterflies and Host Plants Is it a Family Affair? Kenneth A. Bridle, Ph. D. Director of Stewardship and Inventory Piedmont Land Conservancy August 2012

2. This Presentation • My discomfort with Host Plant Lists • Most are over simplifications • Even if lists are correct, Why? • My interest in Plant and Insect Interactions • Co-evolution? • My interest in Natural Product Chemistry • Chemical ecology and environmental impact

3. Butterfly Host Preferences Vary • Some Butterflies use many kinds of plants: • Painted Lady, Mourning Cloak, Red-spotted Purple • Gray Hairstreak, Spring Azure • Some Plants support many kinds of Butterfly: • Willow, Cherry, Nettles, Grasses, Legumes • Some Butterflies and Host Plants are very specific • Monarchs, Pine elfin

4. Monarch Caterpillar

5. How Do Butterflies Recognize their Host Plants? • Some evidence suggests that some butterflies can learn the leaf shape/texture • Some insects, including butterflies might be able to see distinctions in leaf color not obvious to us • UV light patterns similar to flowers and bees • The best evidence seems to be chemical selection

6. The history of insects eating plants (greatly abbreviated) • The first insects were polyphagus (Paleozoic) • They ate any plant material they found • (sucking sap comes first then chewing later) • Most plant matter was similar in composition • Later, some insects specialized in eating spores • Plant spores are higher in nutrient value than other tissues • Some spore eaters later moved to pollen with the rise of the angiosperms (Cretaceous) • This avoids much toxic chemistry • Pollen is hard to digest • Finally some pollen eaters switched to nectar. • Insects with complex life cycles often specialize in different foods at different stages

7. Evolution from Polyphagus to Oligophagus to Monophagus • Suppose all insects started out as food generalists • Competition among plant eaters is high • Impact on plants by all the eaters is high • Plants develop some protective chemistry to defend themselves • An “arms race” starts as insects develop ways to avoid or metabolically adapt to these new chemistries. • What were once toxic chemistries, soon became markers, attractants and nutritional requirements. • So what started as chemical defense became the basis of mutual adaptation.

9. Geologic Time

11. Plant Chemicals influence Insects in many ways • Repellants / Attractants • Change movement direction of insects • Start or Stop Movement • Simulant or depressant of locomotors systems • May work in-vitro • Start or Stop Feeding • Antibiotics • Limit larval growth and development • Limit life expectancy/ fecundity of Adults • Ovipositional cues

12. Cloudless Sulfur laying eggs

13. Types of Plant Chemistry • Basic Biological Chemistry • Carbohydrates, Proteins, Nucleic Acids • Plant Structural Chemistry • Cellulose , Lignin, Tannin • Plant Secondary Natural Products • Not strictly necessary for growth and development • Internal toxic compounds • Volatile organics that surround the plant • Leaf Surface Chemistry • Induced or Constitutive • Induced are made in response to damage

15. Plant Natural Product Chemistry

19. Compounds found on the leaf Surface

20. Plant Leaf Cross Section

21. Leaf under Dissecting Microscope

22. Monarch Egg

23. Glandular Trichomes under Electron Microscope

24. Trichome Exudate collected on Glass

25. Large Scale Leaf Surface Chemistry Collection

26. Gas Chromatograph of Leaf Surface Chemistry, Nightshade and Tomato

27. Chromatograph of Flue Cured Tobacco

28. Chromatograph of Oriental Tobacco

29. Tobacco Bud Worm Moth

36. Plant Sterols

38. Plant Chemistry is a Family Trait • Closely related plants share growth habit, structural and biochemical themes • They look (and smell) alike to us and insects • Chemistries that have adaptive advantage are continued from ancestral types of plants • If it works stick with it • Members of plant families usually have variations on the basic chemical theme(s) • Tweaking and improving all the time

40. Common Plant Families

41. What are the important butterfly host plant families in our area? • Started with the list of common plant families, identify the ones known to be used by butterflies • 35 families host butterflies out of about 150 in flora • About 17 plant families host the majority of butterflies • Made a table of these most common host plants compared to the families of butterflies • XX means many butterflies in that group

42. Butterfly Family Groups • Swallowtails • Tigers, Pipevines, Blacks, Zebra • Blues and Hairstreaks • Azures, Eastern-tailed Blue • Brushfoots • Monarch, Fritillaries, Buckeye, Satyr, Wood nymph • Yellows and Whites • Cabbage White, Sleepy Orange, Sulfurs • Skippers • Fiery, Silver Spotted, Sachem

43. The Family Correlation

44. Thoughts on Family Correlation • At the Family level there appears to be a segregation of butterfly families using plant families • No one plant family is used by all butterflies • Three plant families are used by three butterfly families • Three plant families are used by two butterfly families • Eleven plant families are used by only one butterfly family • Many families are not butterfly hosts, but may be hosts of other insects.

45. The Whites and Yellows group nicely in two families • Yellows use legumes, Whites use brassicas • Skippers group into three plant families • These are most often found in open fields and grassland natural communities. • The Swallowtails and Brushfoots seem to diversify most • Swallowtails predominantly on woody species • Brushfoots seem to favor herbaceous • If the Gossamers, Yellows and Whites and Skippers were broken into subfamilies other patterns might appear • This is by no means a rigorous scientific study, there is lots of room for improvement.

46. Additional Information • Subsequent to the original presentation, “Butterflies of the East Coast an Observers Guide” was published (Cech and Tudor, 2005) • These authors recognize the importance of plant families to the butterfly host plant discussion in several parts of this book. • They also integrate host plant use with theories of butterfly lifestyle or success strategies

47. Cech and Tudor 2005

48. Host-Plant Related Lifestyles Cech and Tudor 2005

49. Final thoughts • Host plant selection and use is complex and is certainly varies depending on the species involved • Ovipositional cues are most likely chemical although some visual cues and random trial also occur • Chemical content of the leaf both feeds larva and may protect larva and later adults from predation and completion. • These insects are often harmed or suppressed, but they are still successful. • Relationships of host plants and insect predators reflect past evolution and speciation. • Plant chemical arms race might be responsible for insect diversity explosion in Cretaceous • Diversity of plant families in an area probably supports a diversity of butterfly species • Good for wildlife sensitive gardeners to know • Awareness of chemical cues in nature will make us better naturalists.

50. Thanks to: • Dennis Burnette • Founder of the Carolina Butterfly Society • Motivational force behind the Triad Chapter • And special thanks for any butterfly images which may have slipped into any of my butterfly presentations! • To all the folks who organize and report butterfly counts. This is really great citizen science. • To the current board of CBS and organizers of this meeting.