September 1879: 144 years ago

Hidden cargo of ship ballast recorded in herbaria

This specimen was collected in 1879 by Isaac Martindale, who collected more than 80,000 specimens during his lifetime. The label reads it was collected in "Camden, NJ Ballast."  The specimen was identified as Galingsoga caracasana, which is now considered the same as Galingsoga quadriradiata. The species is native to Mexico, and Central/South America. A common name for the species is "shaggy soldier."  Though my favorite name for the species is "Pittsburgh weed," which it was once called due to its abundance in Pittsburgh.  But that is a different story. 

This specimen was recently used in a fascinating new study published in the American Journal of Botany by botanists by Ryan Schmidt and other botanists at Rutgers University entitled "Hidden cargo: The impact of historical shipping trade on the recent-past and contemporary non-native flora of northeastern United States."  They used herbarium specimens to assemble a dataset of species that were introduced to North America via ship ballast.  In the 1800s, ships travelling across the Atlantic (and elsewhere) filled their hulls with stones, sand, dirt, and other material to use as weight to stabalize the ship.  When then got to their destination port, they dump this extra ballast.  This ballast material often contains plant material, including seeds, thereby making ballast an important vector for the introduction of new plant species from far away.  The study of "ballast flora" has long fascinated botanists, who noticed unusual new plants growing around port cities.  Many of the species may not become established but other species would establish, spread, and become invasive.

There are a lot of fascinating things about this study.  They surveyed specimens in the Mid Atlantic and Northeastern US, many of which were recently digitized through the NSF funded Mid Atlantic Megalopolis Project (including Carnegie Museum!). Based on the labels, they assembled a dataset of species which were introduced or found in "ballast." The study used specimens to track introduction, establishment, and invasion of plants introduced via ballast in New Jersey.

Incredibly, they found that 48% of introductions from ballast became established to some degree! This rate is MUCH higher than what is sometimes suggested (the "tens rule" or 10% of introduced plants become established).  

This study points to herbarium specimens as a unique source of data.  It is very difficult to measure the success of introduced species, as those species that fail to establish are rarely recorded.  

Read more about this cool study here: ​https://botany.one/2023/08/the-hidden-cargo-that-brought-hundreds-of-plant-species-to-the-garden-state/