Lost Spruces?

Here's a shot from Volo Bog last week:

Black Spruce (Picea mariana), Volo Bog, Lake Co, IL 2/9/2014

This is a Black Spruce (Picea mariana). There are only a handful of individuals there, at least that are visible from the boardwalk. Swink and Wilhelm state that someone clearly planted them there (1), and the Illinois Natural History Survey lists the species as introduced in the state (2). But they're found naturally in bogs as far south as Ozaukee County, WI, and they're generally slow growers in bog environments. This one is just southeast of the open center of the bog, in a spot that would have taken a lot of work to reach, through thick growths of Winterberry Holly (Ilex verticillata) and Poison Sumac (Toxicodendron vernix). It does seem rather odd that a person would go through all that to plant a few trees in the middle of a bog where they'd hardly ever be seen.

Another possibility, of course, is that they were planted nearby as ornamentals, and the seeds were then carried by the wind into the bog, where they found a favorable environment for growth. But, could these trees actually be leftovers? The idea isn't too far-fetched. James King found palynological evidence of Picea in northern Illinois as recently as 400 years ago, within a handful of lifetimes of a slow-growing tree. (3)

Volo Bog does have other species at the southern edge of their range. Pitcher Plants (Sarracenia purpurea) are the most famous, but Tamarack (Larix laricina) is also found here, limited in NE Illinois to these bogs. And then there's this guy:

Boreal Carrion Beetle (Nicrophorus vespilloides), Volo Bog, Lake Co, IL 9/26/2012

This is a Boreal Carrion Beetle (Nicrophorus vespilloides), which in North America is only found in sphagnum bogs such as Volo, and is mostly found north of Illinois. (4) Does all this mean that these Spruces didn't have human help to grow where they are? No. But it should give us pause when we assume that they did.

The question of these spruces' origin is, of course, purely academic. But it is a wonderful example of the limitations of historical data. Many sciences, including evolutionary biology, make extensive use of historical data, and we've derived some amazing insights from it. But over time information does get lost, and it's always worth remembering that we're looking at a puzzle with pieces missing, increasingly so as centuries pile into eons. Our conceptions of ancient life have changed repeatedly over the years, partly as a result of improvements in our theoretical understandings, and partly as a result of new information left over from long ago. Modern insights really are based on more information than before, which can only help improve them, but the next revolution is always waiting, under a stone or deep in a bog.

(1) Swink, F. and Wilhelm, G. Plants of the Chicago Region. (1994) Indianapolis: Indiana Academy of Science.

(2) http://www.inhs.uiuc.edu/~kenr/woody2.html

(3) King, J. E. (1981). Late Quaternary vegetational history of Illinois. Ecological Monographs, 43-62.

(4) http://bugguide.net/node/view/148730/data