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

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

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

Monarch Caterpillar

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

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

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.

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

Cloudless Sulfur laying eggs

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

Monarch Egg

Plant Sterols

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

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

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

The 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.

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.

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

Cech and Tudor 2005

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.

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.