Literature Review: Hickory Evolution

by Carl Strang

The scientific papers that attract my attention are often ones that fill in pieces of life’s long history on Earth. What is happening today is plenty interesting, of course, but the present moment occupies only the tiniest fraction of billions of years of interesting stuff. One aspect of that story is the similarity of plants between Asia and North America. A study from earlier this year focused on hickories (trees in genus Carya), which occur in both places. The authors state their results well in their abstract, from which I’ll quote.

A shagbark hickory bud opening in spring

A shagbark hickory bud opening in spring

Zhang J-B, Li R-Q, Xiang X-G, Manchester SR, Lin L, et al. (2013) Integrated Fossil and Molecular Data Reveal the Biogeographic Diversification of the Eastern Asian-Eastern North American Disjunct Hickory Genus (Carya Nutt.). PLoS ONE 8(7): e70449. doi:10.1371/journal.pone.0070449

Abstract: “The hickory genus (Carya) contains ca. 17 species distributed in subtropical and tropical regions of eastern Asia and subtropical to temperate regions of eastern North America. Previously, the phylogenetic relationships between eastern Asian and eastern North American species of Carya were not fully confirmed even with an extensive sampling, biogeographic and diversification patterns had thus never been investigated in a phylogenetic context. We sampled 17 species of Carya and 15 species representing all other genera of the Juglandaceae as outgroups, with eight nuclear and plastid loci to reconstruct the phylogeny of Carya. … Our results support two major clades within Carya, corresponding to the lineages of eastern Asia and eastern North America. The split between the two disjunct clades is estimated to be 21.58 (95% HPD 11.07-35.51) Ma [millions of years ago, early Miocene]… [A]nalyses incorporating both extant and extinct genera of the Juglandaceae suggested that Carya originated in North America, and migrated to Eurasia during the early Tertiary via the North Atlantic land bridge. Fragmentation of the distribution caused by global cooling in the late Tertiary resulted in the current disjunction. The diversification rate of hickories in eastern North America appeared to be higher than that in eastern Asia, which is ascribed to greater ecological opportunities, key morphological innovations, and polyploidy.”

Juglandaceae is the plant family to which the hickories belong. It also includes the walnuts. The “eight nuclear and plastid loci” are genes in cell nuclei and chlorophyll-bearing organelles called plastids that the researchers analyzed. Mutations over the years accumulate at the same time species are splitting apart, allowing relationships to be discovered and time estimates for the process to be made.

Downy Woodpecker Dossier

by Carl Strang

This is another of my dossiers, a collection of observations that represents what I know about a particular species from my own experience. Following an initial description that summarizes what I remembered when I set up the dossier in the mid-1980’s, each individual entry begins with my date code.

Downy Woodpecker

This is an abundant, year-round resident of forested areas and savannas. They nest in small tree cavities. Feed by searching on small twigs up to the size of tree trunks, on shrubs, sturdier weed stems, occasionally on the ground. They crawl rather than hitch along. Voice a rapid whinny, individual tones mores musical than hairy woodpecker’s and lower in pitch; reminds me of a movie witch’s cackle. When feeding, they pick at twigs or flake bark. They do much pecking under bark edges, when foraging on a tree trunk. Nest in hollow branches or main tree stems.

30MR86. 2 male downy woodpeckers in an aggressive encounter. Frequent flicking of wings and spreading of tail. Assumption of posture in which body is upright and neck arched back so bill points straight up. Appeared to be trying to get above one another. Generally faced one another when in bill-up posture, and both did it at once. Red feathers conspicuous.

Late summer 1986. As a flock of ground-feeding grackles flushed at the approach of people, downies and jays at Meacham Grove Forest Preserve emitted contact calls, apparently as a final check of location and status before possible flight.

8MR87. Waterfall Glen Forest Preserve. Male appears to be exploring the acoustic properties of a white oak limb. Spiralling up it, drumming frequently. Full drum about 1 second, poor spots drummed 0.5-0.75 seconds. Repeatedly drummed fully the spots that gave the greatest volume and lowest pitch. As I wrote the above, I heard vocalizations. Three downies now in that tree. The drummer and a second, presumably its mate, chased a third which gave fragments of the whinny call. They held themselves flat against branches, tails fanned, and gave whinny fragments and a more chattering, flatter sort of vocalization. The third bird left, but a few seconds later I heard a brief drumming about 50m in the direction it had gone. The other two immediately flew in pursuit, and after a few brief whinnies all was quiet.

7MY88. Indian Trails area, Culver. One systematically probing and pecking bases of hickory buds, open with leaves about 1/4 expanded.

18OC88. Hartz Lake area, Indiana. A vigorous, repeated displacement of one individual by another, though they stick together.

7MR89. Extended confrontation between 2 male downies. Mostly jerkily hopped up small tree stems within 3 feet of one another, flicking wings almost constantly, approaching, withdrawing, occasionally expanding and flashing the red patches, changing trees together, occasionally getting out of sight of one another momentarily, overall appearance of jerky movement. After more than 5 minutes of this, one displaced the other several times in rapid succession, but then they returned to the jerky maneuvering, with occasional rests on opposite sides of the trunk, out of sight of one another. Before all this, one of them called repeatedly, loud single-note reps. Another bird (female? Not seen) called or drummed a couple times during this from at least 50 feet away.

26-31MY90. Hartz Lake area. A nest in a river birch, entrance 12 feet up. Both parents fed, about 10 minutes between arrivals for each parent. Young still small, faint cheeping voices. When screech owl family passed by early one morning, one adult mobbed at a distance with alarm notes.

30SE90. Downy woodpecker eating poison ivy berries near Lafayette, IN.

10FE99. Two pairs of downy woodpeckers are actively engaged in drumming, calling, displaying and chasing in an area that centers on the Willowbrook bridge but extends most of the way to the marsh in one direction, and up to the big willow near the marsh’s water intake pipe in the other.

23MR99. The situation has become very complex at Willowbrook and difficult to follow, with displaying and chases, drumming and calls going on all day. It appears that at least 3 pairs are involved, with the center of the activity between the creek and the center of the outdoor animal exhibit. A downy woodpecker also was drumming in the big cottonwoods in the center of the Nature Trail circle, the first I’ve noticed there this year.

29MY99. Maple Grove Forest Preserve. Young audible in nest.

5OC99. Willowbrook. Downy eating poison ivy berries.

23FE00. Willowbrook. Male downy woodpecker displaying toward female, body in a stiff posture, tail fanned, unusual chattering vocalization, following or chasing her, matches Stokes’ description of Bill Waving.

1-2JL00. Juvenile downies have large red patches on top of head.

27MR06. Downy woodpecker drumming is so rapid that individual strikes cannot be followed. Hairy woodpecker drumming very rapid, individual strikes can be distinguished. Red-bellied rapid but slightly less so.

2009. Mayslake. One successful nest was in a large weeping willow branch in the SE corner of the mansion grounds. Young were vocal for several days before fledging. There was at least one other successful nest on the preserve.

Union Township, 1830’s

by Carl Strang

Yesterday I began to recount my study of what my home township in Indiana was like in the 1830’s, before Americans began to transform it from wilderness to a predominantly agricultural landscape. Here is a more detailed line drawing of the final map.


The surveyors’ description provided enough information for me to rough out the map. Getting to the final version required another step. I acquired a soils map of Marshall County, and looked for correlations between soil types and vegetation categories as the surveyors described them. A specialist might have done it differently, but for my part I was satisfied that the correlations were good enough to draw the detailed boundaries of vegetation areas by combining the surveyors’ records with the finer-scale soils map.

Of the various communities defined by woody plants, swamps are the ones most absent from today’s Union Township. The characteristic swamp tree was the tamarack. Here is some foliage of that species, which is unusual in that it is a deciduous conifer.

Tamarack foliage b

I remember seeing a tamarack tree at the old state fish hatchery that was formed out of the south end of Moore Lake, but that tree died years ago and I know of none surviving in the township today. There are bits of shrub swamps here and there.

A relatively moist (mesic) forest occupied much of the east half of the township, on the rolling Maxinkuckee Moraine. Sugar maples and beeches were characteristic trees, though not necessarily the dominant ones. A remnant of this forest is preserved by the Culver Military Academy in its Bird Sanctuary.

Dry forests and savannas were dominated by oaks and hickories, which grew on more sandy soils. They represent a continuum, with the forests shading the ground fully in the summer and the savannas’ trees scattered enough that prairie-like vegetation grew between them. A forest of this type was the site of the town now known as Culver. Gradually over my lifetime I have noted the passing, one by one, of the town’s largest surviving old oaks that were part of that forest. Dry forests persist mainly in the many “wood lots” preserved by the township’s farmers.

I am grateful to all the individuals and organizations, from private landowners to The Nature Conservancy, who have made the commitment to preserve and restore these reminders of the wilderness that once was.

Mast Year

by Carl Strang

Mast is a collective term referring to nuts and acorns. Trees do not produce these in the same amounts each year. In some years very few nuts or acorns develop in a given species, and in other years prodigious numbers appear. High production seasons are called mast years. 2009 is proving to be a mast year for bur oaks and white oaks at Mayslake Forest Preserve, where the trails in places are littered with the fallen acorns. Here is an example for bur oak.

Bur oak mast b

Here, white oak acorns abound.

White oak mast b

Though elsewhere I am seeing lots of walnuts, this does not seem true for that species at Mayslake, which also is having an unremarkable year for hickory nuts. Nearby, at Fullersburg Woods Forest Preserve, I noted in 2007 that walnuts, hickories and red oaks had a mast year. It is common for members of the white oak group and red oak group of species to be decoupled from one another in their mast years.

Fox squirrel 1b

As you might imagine, animals such as tree squirrels are impacted by mast years. Mayslake’s gray and fox squirrels will have an easy winter with so much food available. They help their cause by biting acorns before burying them in an effort to kill them. The acorns, in a countermeasure, are quick to sprout when they fall to the ground. A study published in 2006 in Science (314:1928) found that red squirrels (which live north and south of us, but not in DuPage County) themselves reproduce more heavily in mast years (perhaps responding to an increase in flowering or other advance cue). Such adaptive interactions between species are referred to as coevolution. The phenomenon of the mast year itself likely is, at least in part, an evolutionary tactic by the trees. By coordinating their mast production they can limit their seed-predators’ survival in some years, overwhelm them in others. Such an episodic mass reproduction is reminiscent of the periodical cicadas.

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