Mason Heberling

​Staghorn sumac (Rhus typhina) collected on October 19, 1929 near Penn Hills (Rosedale), PA by W.R. Van Dersal. This species is in the cashew family (Anacardiaceae), which is includes many painfully irritating species like poison ivy and poison sumac (although both of these species are not closely related, but in different genera).
 
For some reason, staghorn sumac is one of those species that I find iconic in Western PA.  Common along roadsides, farms, and old fields.  Its leaves are often brilliant red in the fall.  The fruit persist on branches through winter.
 
Sumac specimens in the Carnegie Museum herbarium are now imaged and online!  Searchable at midatlanticherbaria.org.
 
High resolution image of this specimen can be found here: http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12232607&clid=0
 

Fall allergies causing you grief?  
 
Ragweed is a plant many people are (all too) familiar with.  Or at least their bodies are.  Common ragweed (Ambrosia artemisiifolia) is actually native to North America, but has been introduced across the world.  In many cases, this plant (or other ragweed species) are to blame for seasonal pollen allergies known as “hay fever.”  In summer and early fall, ragweed plants produce copious numbers of pollen grains, which are dispersed in the wind.  Don’t blame those insect-pollinated plants with showy flowers for your allergy troubles.  Wind pollinated plants like ragweed are your culprit. 
 
This ragweed specimen was collected by Bonnie and Joe Isaac in Lawrence county, Pennsylvania on October 8, 1995.  Bonnie is the collection manager in the Section of Botany at the museum, an active plant collector and field botanist, and an expert on the plants of Pennsylvania.
 
Although ragweed is native in the US, historical records (pollen deposited in sediment cores) suggest that this species was far less common in North America before European colonization.  This is perhaps not too surprising considering the species thrives in disturbed habitats that came with European colonization and urbanization.  A study published in 2014 by Martin and colleagues in the journal Molecular Ecology extracted DNA from nearly 500 historic herbarium specimens dating back to the 1800s to measure the genetic makeup prior widespread changes to the landscape in the late 19th century. Combined with data from recent collections, they found shifts in the genetic makeup of ragweed populations as the species was expanding in the United States. 
 
Read the study abstract here: https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.12675

​Corn is a staple crop known well by many across the world.  Corn is used in a variety of ways including human food (from corn on the cob to corn syrup), animal feed, ethanol production, and especially this time of year, fall decoration and corn mazes. Corn is an economically important crop worldwide, with over 81 acres expected to have been harvested in the US alone this year.  But where did this plant come from?
 
Corn, better known to many as maize (Zea mays), is a domesticated plant.  Yes, plants can be domesticated, just as your pets.  Corn was domesticated from a wild grass species known as teosinte in Mexico approximately 8,700 years ago.  Like many other food crops, corn was domesticated by humans through artificial selection – that is, through selective breeding for traits of interest over many generations, causing the evolution of a species.  In the case of corn, teosinte evolved through human intervention by selecting seed from plants with desirable traits (such as large cobs), planting those seeds, again selecting the “best” plants, and repeating over decades.  Eventually, teosinte evolved from a many branching grass with small seed cobs to what we recognize as corn today – tall, unbranched plants with large, tasty cobs. 
 
This specimen is of a species of teosinte (Zea mays subspecies parviglumis) that is thought to be the close relative of the domesticated crop we know today (Zea mays subspecies mays).  This specimen was collected near the site of domestication in Mexico on October 2, 1982 by Hugh Iltis, a botanist and geneticist at the University of Wisconsin-Madison who studied teosinte species and an influential conservationist.   Note the species name on the label “Zea mays L. subsp. parviglumis var. parviglumis Iltis and Doebley” – his name at the end denotes Iltis was one of the scientists who named the taxonomic variety new to science in 1980. It was also collected in the “type locality,” meaning from the same spot where the specimen used to describe the species was collected.