Collected on this day...
a weekly blog featuring specimens in the Carnegie Museum's herbarium.
each specimen has an important scientific and cultural story to tell.
each specimen has an important scientific and cultural story to tell.
Herbarium specimens can provide insight into plant-insect interactions. For instance, many specimens show obvious signs of insect damage to the leaves or flowers. Many other specimens, upon closer inspection under magnification, show damage that is much subtler. Sometimes, even the larvae or insects were also pressed with the plant! Some of this damage may have happened from pests in the herbarium that occurred over decades of storage. Damage from herbarium pests is a serious concern and collection managers are also conservators of these archives, keeping a vigilant eye out for damage from the elements (such as light, temperature, humidity, water, and other chemicals) and introduced pests (such as mold and insects). However, damage that occurs in the herbarium is minimized for long term preservation and luckily, insect damage that occurs in the herbarium is often easily distinguished from herbivory that happened in the wild, before the plant was collected, dried, pressed, and added to the collection.
Few studies to date have used the herbarium record to understand the ecology and evolution of plant-insect interactions. However, there are several pioneering studies at the frontier of this novel use of these collections.
This specimen pictured above of wild parsnip (Pastinaca sativa) was collected by Leroy Henry on July 17, 1968 along the Pennsylvania Turnpike not far from Pittsburgh. Leroy Henry was an influential Curator of Botany at the Carnegie Museum from 1937-1973, having collected thousands of specimens in the herbarium.
In addition to the “standard” herbarium label that gives information on what the specimen was first identified as, where it was collected, who collected it, etc., check out another typed label affixed to this sheet. This annotation label indicates two seeds were removed from for chemical analysis in 2005. Annotation labels are commonly added to specimens years to centuries later to note its use in a study, a new identification, and/or part of the specimen was removed.
This specimen was one of many specimens included in a study on wild parsnip by Zangerl and Berenbaum published in 2005 in the high-profile journal Proceedings of the National Academy of Sciences (PNAS).
Wild parsnip (Pastinaca sativa) was introduced to the United States from Europe centuries ago and has since spread to become invasive. The species is a member of the carrot family (Apiaceae). Like many other species in this plant family, wild parsnip produce phototoxic chemicals called furanocoumarins, which protect the plant from insect herbivory. These compounds also cause major skin irritations in humans, reacting with sunlight to cause nasty rashes. This group of chemicals is of the same fame of giant hogweed, poison hemlock, and other well-known toxic plants in the United States.
Zangerl and Berenbaum (2005) analyzed herbarium specimens collected over the past 150+ years. These specimens were collected from before wild parsnip was widespread in the US and compared those to specimens collected more recently, after the species was widely established. A major herbivore, the parsnip webworm (Depressaria pastinacella) was also accidentally introduced in the mid-late 1800s. The authors found that as rates of webworm attack increased, so did the toxicity of wild parsnip. Specimens from 1850-1889 (early stages of introduction) had lower levels of the toxic furanocoumarins than plants collected more recently, as well as than specimens collected in their native range (Europe), where the parsnip webworm is also native.
There is so much known and unrealized potential in herbarium specimens. This particular specimen was not collected with the intention of studying the ecology and evolution of plant-insect interactions. This study helped inform our current and future use of biological control agents to manage introduced species.
These unanticipated uses (often decades to over a century after a specimen was collected!) illustrate the incredible power of natural history collections.
See an excellent paper by Meineke et al. just published on this topic (including quantifying the effects of climate change on plant herbivory through herbarium specimens): https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecm.1307.
Check out the cool parsnip webworm study here: http://www.pnas.org/content/102/43/15529
Wild parsnip (Pastinaca sativa) in an unmowed roadside median next to Bloomfield Bridge, Pittsburgh PA on June 29, 2018.
Spring wildflower season will be here very soon. Known as “harbinger-of-spring” (Erigenia bulbosa), this little plant in the carrot family (Apiaceae) is among the first to flower in our region. It emerges and flowers before many other species, often in March. Although faced with cold temperatures in the early spring, the species is able to take advantage of the high light before the overstory trees leaf out in late spring. Harbinger-of-spring can be found in forests throughout the midatlantic and great lakes states. It is uncommon, however, and listed as a rare species of “special concern” in Pennsylvania.
In addition to its scientific importance, this particular specimen has special cultural significance. It is one of the earliest specimens collected by Otto Jennings, one of the first botany curators at the Carnegie Museum of Natural History and an influential botanist, conservationist, and educator. Jennings (1877-1964) was born on a farm in Olena, Ohio. He collected this species in Olena when he was 21 years old, the year he started as a student at the Ohio State University. Jennings started his 60-year tenure at the Carnegie Museum six years later, in 1904. He made many contributions throughout his career, serving as the Curator of Botany, Director of Education, and eventually Director of the Carnegie Museum of Natural History. He also was Professor of Head of the Department of Biological Sciences at the University of Pittsburgh, having advised many students. His legacy remains to this day for his influence on the museum, botany, conservation, and environmental education.
Above: Jennings in the field in 1958.
Giant hogweed (Heracleum mantegazzianum) is considered a significant public human health concern. This non-woody plant can be 8-20 feet tall with leaves up to 5 feet wide! In fact, it took 6 separate herbarium sheets to capture the characteristics of this species. This specimen was collected from a garden, where it was intentionally grown for the purposes of educating the public about this plant. Native to central and southwest Asia, this plant can now be found in parts of Europe, Australia, New Zealand, and North America. It is thought to be eradicated in Pennsylvania.
This plant is highly poisonous and designated as a federal noxious weed. The sap of giant hogweed causes “phytophotodermatitis,” meaning serious skin inflammation occurs when contacted skin is exposed to sunlight. Skin rashes can be very severe. The sap is also said to cause blindness.
Giant hogweed, like poison hemlock and Queen Anne’s lace, is in the carrot family (Apiaceae). It might be confused with the related native plant, cow parsnip (Heracleum lanatum), but giant hogweed is noticeably larger in height and flower size.
Poison hemlock (Conium maculatum) was used to kill the Greek philosopher Socrates in 399 BC. All parts of the plant are highly toxic, containing an alkaloid poison, coniine, which disrupts the central nervous system and can cause paralysis of respiratory muscles and death.
Although native to Europe, poison hemlock has been introduced to the United States and found in the Pittsburgh region. Despite the name, it is not related to hemlock trees, but instead a member of the carrot family (Apiaceae). Carrot family members are often recognizable by their flowers, which are on stalks that spread from a common point to form umbrella-like clusters (botanically called an “umbel”).
Keep an eye out for this species. It is blooming now in our region along roadsides and ditches. Towering at heights over 9 feet tall, this plant is hard to miss if you look for it. Aside from its height, it can also be distinguished from similar species by the purple blotches on the stems. It is best to avoid contact with this species, it can be fatal if ingested but can also cause skin irritations if touched.
It has been introduced for a while now, but seems to be getting more common in some areas of region.