Going, Going, Going…

by Carl Strang

The former friary at Mayslake Forest Preserve continues to be whittled away by the demolition contractor, opening space for re-establishment of native vegetation and animal life.

The east wing was taken down, and the big crane began to remove the middle of the building’s north side. Meanwhile, materials continued to be sorted. In particular, metals were collected presumably for recycling.

Soon the north side was reduced to two separate fragments.

The western fragment was nibbled away from its east side.

The work evident inside suggested this was a slow process.

For example, here is a pile of lumber removed from that end.

The eastern fragment appeared to be less of a challenge.

It was whittled from the east.

I happened to be present to witness its final moment. A bit of wall was being munched by the big crane’s jaws.

The crane removed a window.

After taking the following picture I started to shift my position.

In that instant the remaining part of the building collapsed. It happened so quickly that by the time I turned my head, this is all there was.

Only one corner portion of the original building complex remains standing.

Prehistoric Life 3

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Proterozoic Eon (2.5 billion-542 million years ago)

The beginning of this eon formally is marked by the oldest continental rocks that never have been metamorphosed by heat or chemical change. The Proterozoic Eon was officially subdivided in 2004, with the part of it from 640-542 million years ago designated the Ediacarian Period (Science 305:621). The beginning of that period is marked by the end of the “Snowball Earth” glaciation (see below). Other eras and periods have been proposed (4 periods in a Paleoproterozoic Era, 3 in a Mesoproterozoic Era, and 3, including the Ediacarian, in a Neoproterozoic Era).

Life on Earth. Aerobic, eukaryotic life forms appeared in the Proterozoic eon around 2 billion years ago, when oxygen produced by photosynthesis built up enough to require organisms to adapt. Archaea are genetically closer to eukaryotes than are bacteria, and are regarded as the more likely source of the first eukaryotes (Science 311:1283). The oldest eukaryote fossils, at 2.1 billion years, were found in Michigan. This was a significant step, now regarded as resulting from a combination of organisms, with today’s mitochondria and chloroplasts, for instance, the descendents of once separate organisms (for a present-day analog, in which a protozoan consumes an alga and converts it to an indwelling partner, see Science 310:287). Though it has been assumed that this early life was all single-celled, with some colonial forms like stromatolites, in 2010 some marine fossils were reported from Gabon of 2.1 billion years ago that may have been multicellular.

A long time period, from 2 billion to 1 billion years ago, then passed with life stalled at a very simple level. It has been proposed that the cyanobacteria and algae produced oxygen, but it was limited to the atmosphere and upper ocean. It weathered sulfur into the seas, and the resulting sulfides tied up iron and other needed metal nutrients. In particular, iron is needed for nitrogen fixation. The lack of nitrogen limited growth under this theory, and the bulk of the ocean depths lacked oxygen as well, putting that long hold on evolution (Science 297: 1137). An alternative possibility is that an early invasion of land by simple life broke down rock to produce certain clays which buried a significant amount of organic matter. This would insulate it from decomposition by oxygen, allowing the oxygen in the atmosphere to build up and break the long deadlock (Science 311:1446).

The first undisputed eukaryotic, multicellular life forms appeared in the late Proterozoic. These early multicellular organisms, called the Ediacaran biota, were sea creatures, most of them having forms like those of today’s worms, sea pens and jellyfish. Others were unlike anything living today. All known varieties were filter feeders, none preyed on other multicellular species. Study of a series of these fossils from Newfoundland of 560-565 million years ago suggests that the Ediacaran biota were less diverse than had been thought, that previously distinguished species in fact are various body parts, growth stages and environmental variants of the same genetic line (Science 305:1141). A 2010 report of trackways from that area (similar to those produced by sea anemones) suggests that some could move. This appearance of multicellular life followed by only 5 million years an elevation of oceanic oxygen levels that corresponded to an atmospheric content 15% of today’s (Science 314: 1529). In 2010, fossils were reported from Australia that may have been early sponges from 650 million years ago, prior to or during the Snowball Earth glaciation. This is consistent with another 2010 study of sponge genes that found much in common with all animal life and pointed toward a Proterozoic origin of the group.

Local landscape. The most ancient part of North America, the Canadian Shield (extending as far south as central Wisconsin), formed through the collision and fusing of some of the more ancient continental plates, when the Earth had cooled enough in the Proterozoic Eon, 1.95-1.85 billion years ago, that plate tectonics settled down some.

1.83 billion years ago, when the southern edge of North America was in central Wisconsin, a subduction zone dragged a body of continental crust in from the south. The resulting collision enlarged North America, but whether it extended to include northern Illinois is not known. If not, our bit of North America became added 1.8-1.6 billion years ago through further subduction activity accreting new volcanic island arcs in the Middle Proterozoic. With subduction at the local plate boundary a possibility, this was the most likely time for a deep ocean environment here.

Our closest Proterozoic rocks are 4000 feet below us, granite that formed far underground, 1-1.4 billion years ago, as further geological activity resulted from the collision of our continent with others to the south and east (during the formation of an early supercontinent, Rodinia [Science 300:1379]). It is possible that Rodinia’s formation brought a temporary halt to plate tectonic activity, as all subduction zones fused and halted (Science 319:85-88). Without the cooling effect of subducted crust the mantle heated up, with the granite far below us forming as a result. This collision also lifted our area up, so that by the late Proterozoic, that granite was at the surface, exposed to erosion.

The most extensive and severe ice age in the history of the planet is thought to have occurred during this late Proterozoic time, 0.85-0.64 billion years ago. This ice age has been dubbed “Snowball Earth,” and is thought to have occurred because of an incomplete biogeochemical carbon dioxide regulating system. Phytoplankton with calcium carbonate shells had not yet evolved, and their absence at critical times has been connected to too little carbon dioxide in the atmosphere, the inadequate greenhouse gases leading to runaway ice ages (Science 302:859). However, the Snowball Earth period does not appear to have had a major impact on the life that still was restricted to the oceans (Science 300:395). The present consensus is that the planet’s surface was not frozen solid, that there were open places and patches of thin ice that allowed light to reach the ocean’s persisting life (Science 327:1186).

Local life. Granite forms well beneath the Earth’s surface, under continents rather than the sea, but there is the unknown window between life’s origin 3.8 billion years ago and the granite formation 1.5 billion years ago when whatever was replaced by our Precambrian granite could have been a primitive-life-sustaining sea. Our part of the North American continent appears to have been sea floor first. That implies that for an undetermined time period, prokaryotic life was here. Our addition to North America happened at the same time that single-celled eukaryotic life evolved, so there is a slim chance it was here, too, before this area became dry land. There would have been no Ediacaran (late Proterozoic marine multicellular) forms here. There simply is not enough information to allow us to be absolutely certain about whether life was here at all before the current Phanerozoic Eon began.

Fossil cyanobacteria and bacteria, as well as stromatolites are known from as close as northern Michigan, 2.3-2.4 billion years old; stromatolites 1.9 billion years old also have been found in Minnesota. If such organisms were here then, any trace of them was destroyed by volcanism and subsequent erosion. So, in sum: 5-3.8 billion years ago, no life; 3.8-1.5 billion years ago, local life may or may not have existed, if so would have been stromatolites or similar simple marine forms; 1.5-0.5 billion years ago, no local life because it was dry land (unless the clays described above were indeed the result of early microbial activity on land).

Literature Review: Forest Tree Diversity

by Carl Strang

One of the fundamental questions of community ecology is: why are there so many species? This question comes in many forms, and two papers published in the past year addressed a narrowly focused version of it. Given that trees are competing for just a few kinds of resources (light, soil moisture, nutrients), how is it that so many different kinds of them can coexist in forests? Why don’t the best competitors just push the rest out of the picture? One study looked at a temperate forest (Clark, James S. 2010. Individuals and the variation needed for high species diversity in forest trees. Science 327:1129-1132).

The other study had some personal interest because it was done at the famous Barro Colorado Island field station in Panama, which I got the chance to visit as a graduate student in 1975 (Comita, Liza S. Helene C. Muller-Landau, Salomón Aguilar, Stephen P. Hubbell. 2010. Asymmetric density dependence shapes species abundances in a tropical tree community. Science 329: 330-332).

Both studies followed the careers of hundreds of individual trees of the various species present, considering their growth and survival with respect to their neighbors. Despite the differences in physical environmental conditions, similar results came out. The bottom line in each case was that trees compete most strongly with (and therefore suppress most strongly) members of their own species. Clark pointed out that this is not shown when species are taken as wholes. Individual careers, particularly variations in size or age, need to be followed to obtain this result. Comita et al. in addition obtained the interesting finding that intraspecific suppression increased with species’ rarity, contributing significantly to the structure and diversity of the tropical forest tree community.

Mayslake Birds

by Carl Strang

Birds still are showing migratory activity at Mayslake Forest Preserve in the second half of November. As I wander the preserve early in the morning or on my lunch break, the birds I find often are changing significantly from one day to the next.

Some, like the golden-crowned kinglet in the photo, come and go day to day. Others may be settling down, as they are present each day and their numbers are more stable. These include dark-eyed juncos and American tree sparrows.

One promising sign that this may be a livelier winter than last is that I have seen pine siskins on three occasions. There were none last year, but the winter before last was a good one for winter finches from the North. That will make for a more interesting season if it happens again.

Prehistoric Life 2

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Archean Eon (4-2.5 billion years ago)

This eon began with the earliest Earth rocks. Bacteria and other prokaryotes were the only life by the end of the Archean, and they began influencing the planet’s geochemistry. The eon’s division into four eras appears to have been done mathematically, with a 300 million year length for the Neoarchean Era and 400 million for each of the earlier others (in order, Eoarchean, Paleoarchean and Mesoarchean Eras).

Life on Earth. The origin of life in the Archean eon is somewhat speculative. It has been demonstrated that organic chemicals formed in outer space and carried to Earth by comets and meteorites were capable of forming vesicles in water that resemble living cells in some ways. Alternatively, the compounds may have formed near volcanic plumes (Science 300:745) or in the atmosphere (Science 308:1014), or around hydrothermal vents (which some argue are the most likely energy source for the first living forms). The main thought at present is that the first step was the formation of RNA, followed by the RNA replicating itself, followed by some of it getting contained within fatty acid vesicles that were the first membranes, and the whole reproducing and taking in new material. Ultimately DNA formed from RNA. All of life probably descended from a single original micro-organism. (Science 323:198). Ribosomal RNA, of a self-replicating type, when inside the kind of fatty acid vesicle that can form spontaneously, creates osmotic tensions that can lead to the absorption of additional membrane material. Competition between similar combinations of components would introduce a natural selection process very early (Science 314:1558).

The earliest fossil life forms were stromatolites, mats of microbes (mainly cyanobacteria) that formed rocklike reefs, perhaps as far back as 3800 million (3.8 billion) years ago. They lived in shallow seas, and some can be found living in the Bahamas and in Australia today. They were preceded by organisms like today’s bacteria (some, called archaea or achaebacteria, are a different division of life. One of these, a recently discovered deep sea thermal vent species, can survive hotter temperatures than any other known life form. It uses what may be the oldest form of microbe respiration [Science 301:934]). More recent genetic evidence supports the idea that the first organism, ancestral to both bacteria and archaea, lived in a very hot environment (Science 311:1283). The first organisms obtained energy for life by chemically manipulating substances such as hydrogen, hydrogen sulfide, and methane. A huge step came when an organism evolved photosynthesis, the ability to oxidize (acquire electrons from) water, thus capturing energy and producing oxygen as a byproduct. This made possible the stromatolites mentioned above. The Archean eon has been called by some the Age of Prokaryotes. There was at best a trace of oxygen in the Archean atmosphere. The main organic matter consumers may have been methane-producing bacteria. The resulting methane was one major greenhouse gas keeping the planet warm then (Science 298:2341), but it also reacted with nitrogen to produce an atmospheric haze that protected ammonia, another greenhouse gas, from being destroyed by ultraviolet light (Science 328:1266). Recent evidence suggests that the Earth’s magnetic field was active in the Archean, at 50-70% of today’s strength, and this also would have helped shield early life from solar damage (Science 327:1238). Life was limited to aquatic environments.

Local landscape. The farther back in time we look, the less information is available to tell us where Illinois’ part of the Earth’s crust was located, and what it was like. At first, the Earth was still so hot, and plate tectonics so active, that Archean continents were kept small. Only 30-40% of the present volume of continental crust existed by the end of the Archaean. Pieces of today’s continents were scattered all over, in much different relationships than we have today. There is inadequate remaining geological material to tell us whether our part of the Earth’s crust even existed in this eon.

Local life. Any life that may have been here that early was very simple, unicellular though possibly colonial, marine, and limited to prokaryotic organisms.

Component Communities Video

by Carl Strang

In the early days of this blog I shared some of my observations on component communities, groups of species centering around the various plants in an ecosystem, in this case local forests. A particular plant species is consumed by a group of more or less specialized insects, which in turn support more or less specialized parasites. This kind of partitioned structure is an important contributor to ecosystem stability, according to recent ecological research.

The Forest Preserve District of DuPage County, my employer, asked me to put together a slide show illustrating the component community concept. It was posted on the District’s web site this week, and you can find it here:


One goal of the presentation is to explain how deer, in the absence of their predators, can threaten ecosystem integrity. An explanation of the District’s deer management program, which begins this time of year, is included.

Eastern Bluebird Dossier

by Carl Strang

A couple weeks ago I shared my dossier on the great blue heron. Today’s choice is an example of a species for which I have not made a lot of observations, and so my personal knowledge is more limited.

Eastern Bluebird

As a child, occasionally I saw these at the horse-jumping practice ground in the Culver Military Academy’s Bird Sanctuary near Culver.

They nested in birdhouses mounted on posts in a tall-grass meadow with widely scattered trees at the Tyler Arboretum near Philadelphia in 1980.

I saw them in a similar area in spring 1986 at Waterfall Glen Forest Preserve, DuPage Co. I also saw them in southern Illinois at Giant City State Park. [Bluebirds once were so uncommon that simply listing the places where I had seen them was most of what I could write when I first created this dossier].

23MR88. A bluebird singing from the top of a nest box, one of those posted out from a fencerow. [Location not indicated; Blackwell?]

29AP90. Indian Knoll Schoolyard, near Winfield Mounds Forest Preserve. Bluebird foraging on mowed lawn by perching 8-15 feet up and sallying out 20-40 feet from perch to land on ground and take food, then returning to same perch or moving to another. [I since have concluded that this version of sit-and-wait foraging is their primary hunting method. Other birds I have seen hunting in this way are Australia’s kookaburras. Of course, the latter are after larger insects, small lizards, etc.]

20FE93. Bluebirds at the boundary between Hidden Lake F.P. and Morton Arboretum.

6FE99. Bluebirds wintering in a savannah area in the Morton Arboretum.

29AP00. Apparent territorial boundary dispute between two male bluebirds near prairie at Morton Arboretum. Song “peer, peer, poowee,” wings flutter when singing. Flying bird has an appearance like horned lark or swallow.

8OC00. Flock at West Chicago Prairie.

26MY01. A protracted dispute between a pair of bluebirds and a pair of tree swallows at a nest box in the prairie area at the Morton Arboretum’s Heritage Trail. The male bluebird was at the entrance on the outside of the box, with the female on the ground nearby, when the swallows arrived. At first it appeared that the swallows were attempting to chase the bluebirds away, but then the male bluebird became vigorous in chasing after the swallows. After 5 minutes of this, the bluebirds backed off and a swallow took the perch on top of the house. Soon, though, the bluebirds returned and the male resumed his attack. I never saw any of the birds enter the house.

5JA06. Fullersburg. A small flock of bluebirds feeding on honeysuckle berries near the Visitor Center bridge. (These stayed around for another week or so).

4AU09. Mayslake. Bluebirds nesting near the chapel have fledged at least one youngster.

(Dates are coded with the day, two-letter month code, and two-digit year).

Literature Review: Ermine Moth Origins

by Carl Strang

One set of journals I am able to follow continuously is published on-line by the Public Library of Science (PLoS). A paper in PLoS ONE attracted my attention this past year because it related to one of my own studies. Here’s the reference:

Turner H, Lieshout N, Van Ginkel WE, Menken SBJ (2010) Molecular Phylogeny of the Small Ermine Moth Genus Yponomeuta (Lepidoptera, Yponomeutidae) in the Palaearctic. PLoS ONE 5(3): e9933. doi:10.1371/journal.pone.0009933

Each year I follow the story of the trailing strawberry bush at Meacham Grove Forest Preserve (most recent chapter here). That plant’s main consumer historically at Meacham has been the ermine moth Yponomeuta multipunctella.

This paper by Turner and company gave me some context. They looked at all the members of genus Yponomeuta worldwide, and concluded that the genus first evolved in far eastern Asia, originally feeding on leaves of plants in family Celastraceae. As they diversified and expanded west they spread to other plant host families, but some reverted to Celastraceae (which includes Euonymus obovatus, the trailing strawberry bush).

It turns out that Y. multipunctella is the only North American moth in that genus. Science is about story, and connecting stories and giving them context is part of the satisfaction I draw from science.

Downy Gets Gall

by Carl Strang

Last week I had the opportunity to see something I had heard about, had seen signs of, but never had observed myself. I saw a downy woodpecker going after goldenrod gall fly larvae. The bird was a male, like this one.

He was in an open area between the north and south savannas at Mayslake Forest Preserve. He was gripping a tall goldenrod stem with his feet and precisely, quickly hammering a small hole to reach the center of a goldenrod ball gall. He needed only a couple minutes to finish before moving on to the next gall. I photographed the one he opened.

The gall fly larva (Eurosta solidaginis) was gone. Several nearby galls had similar holes. A few questions come to mind. Is this usually the time of year when these birds go after this prey? How does a given woodpecker get started (once he has gotten the idea and has begun, he can go from gall to gall, but how does he learn that there is food here to begin with)?

Prehistoric Life 1

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Hadean Eon (4.6-4 billion years ago)

Earth’s history has been divided into four eons, the Hadean (4.6 to 4 billion years ago, though the recent discovery of rocks that may be 4.28 billion years old may push back the Hadean-Archean boundary [Science 321:1828-1831]), the Archean (4-2.5 billion years ago, though again the starting point may be revised), the Proterozoic (2.5 billion to 543 million years ago), and the Phanerozoic (the remaining time to the present).

The Hadean Eon began with the formation of the Earth, its end coincided with the formation of the crust. The eon was named in recent years for the molten planet Earth was then. Consequently there are no Hadean rocks on Earth, but rocks from the Moon are known from that time and help us in ageing these events (the Moon, being smaller, cooled more quickly).

Life on Earth. Conditions on Earth during the Hadean would not have permitted the existence of life. We must wait for the cooling that will come with the Archaean Eon to see the origin of life.

Local landscape. The Hadean eon is so called because the frequent collisions of comets and meteorites with the growing Earth kept it hot and molten. The largest of these involved a Mars-sized object called Theia by some, the core of which was absorbed into the Earth and some of the crust of which formed the bulk of the Moon (recent measurements and models indicate that one-fifth to one-third of the Moon’s material came from the Earth, and the impact happened 4.533 billion years ago [Science 301:84, 304:977]). The collision tilted the Earth on its axis, so that the Moon, tides and seasons all became possible during a few hours of violence. As the crust cooled, plate tectonics began to operate, and small areas of continental crust were rapidly forming and recycling into the mantle by 4.4-4.5 billion years ago (Science 310:1947; Science 315:1704).

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