Literature Review: Paleogene Period

by Carl Strang

The dramatic departure of the Mesozoic Era and its dinosaurs (as well as a large proportion of other life forms) opened an immense volume of ecological space which was filled by mammals, birds and other diversifying descendants of the survivors. The following are notes from some of last year’s published studies of those early post-Mesozoic epochs.

Blonder, B., et al. 2014. Plant ecological strategies shift across the Cretaceous–Paleogene boundary. PLoS Biol 12(9): e1001949. doi:10.1371/journal.pbio.1001949

Chase, J.M. 2014. A plant’s guide to surviving the Chicxulub impact. PLoS Biol 12(9): e1001948. doi:10.1371/journal.pbio.1001948 This study (interpreted in the Chase paper) found that slow-growing evergreen plants were selected against by the “impact winter” effects of the end-Cretaceous impact event. Plant species with faster growth, cheaper expendable leaves, and thus a quick response to changing and fluctuating conditions, had an advantage and better survival.

The following study suggests that all leaf miners, at least in half the continent, went extinct with the end of the Cretaceous. And yes, that is a poison ivy leaf with 4 leaflets.

The following study suggests that all leaf miners, at least in half the continent, went extinct with the end of the Cretaceous. And yes, that is a poison ivy leaf with 4 leaflets.

Carvalho, Mónica R., et al. 2014. Insect leaf-chewing damage tracks herbivore richness in modern and ancient forests. PLoS ONE 9 (5): e94950. DOI: 10.1371/journal.pone.0094950  They looked at fossil leaf mines, and concluded that all miners went extinct in western North America with the end of the Cretaceous. Newly evolved leaf mining species appeared within 1 million years.

Wilf, Peter, and Ignacio H. Escapa. 2014. Green web or megabiased clock? Plant fossils from Gondwanan Patagonia speak on evolutionary radiations. New Phytologist DOI: 10.1111/nph.13114 They examined a new array of plant fossils and found them to be significantly older than molecular clock studies had indicated they would be. This result points to a need to reconsider molecular dating. It also supports the idea that plants dispersed among the southern continents by continental drift more than by rafting, which had been supported by the younger ages of evolutionary diversification suggested by the molecular dating.

Solé, F., et al. 2014. Dental and tarsal anatomy of ‘miacis’ Latouri and a phylogenetic analysis of the earliest carnivoraforms (mammalia, Carnivoramorpha). Journal of Vertebrate Paleontology, 34(1): 1-21. As described in a ScienceDaily article. They studied fossils (teeth and ankle bones) of a European mammal, Dormaalcyon latouri, from the early Eocene of Belgium, and concluded it is a basal carnivore. It appears to have been arboreal, which implies a continuous forest connecting Eurasia with North America at the time which provided a corridor for carnivore immigration to North America (the age and location suggests that carnivores first evolved in Europe). At the same time it is derived enough to imply that there were early carnivores in the late Paleocene as well.

Rose, Kenneth D., et al. 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications 5: 5570 DOI: 10.1038/ncomms6570 As described in a ScienceDaily article. They found fossils bridging Perissodactyla with earlier mammalian groups, from around 56 million years ago, when India still was an island drifting toward Asia. This suggests that the group originated there during that period of isolation. It has been speculated that primates likewise started there, though that has yet to be determined.

Mayr, G., and V. Wilde. 2014. Eocene fossil is earliest evidence of flower-visiting by birds. Biology Letters 10 (5): 20140223. DOI: 10.1098/rsbl.2014.0223 As described in a ScienceDaily article. They describe a 47-million-year-old fossil bird with stomach contents dominated by diverse pollens, and with anatomy consistent with nectar feeding, and conclude that this is the oldest known bird species that visited flowers.


Literature Review: Leaf Mine Diversity

by Carl Strang

This week’s literature focus is on a paper that provided information suggesting why leaf miners produce such diverse mine structures.

Leaf miners are larval insects so tiny that they fit between the upper and lower leaf surfaces, feeding on the tissues in between. This example is a twisting linear mine on Heracleum.

Leaf miners are larval insects so tiny that they fit between the upper and lower leaf surfaces, feeding on the tissues in between. This example is a twisting linear mine on Heracleum.

Ayabe Y, Ueno T (2012) Complex Feeding Tracks of the Sessile Herbivorous Insect Ophiomyia maura as a Function of the Defense against Insect Parasitoids. PLoS ONE 7(2): e32594. doi:10.1371/journal.pone.0032594

They looked at linear mines in a fly that develops in a French aster. In their review they mention research that has been done on various mine forms and how they may deter parasitoids. Parasitoids focus mainly on the upper leaf surface, so lower surface mines (including tentiform mines of Phyllonorycter moth caterpillars in some of our local plants) provide some protection, and upper surface miners sometimes shift to the lower surface to pupate. Blotch mines provide more escape space for their occupants. In this study they found that complex linear mines, especially ones that have branches and crossing tunnels, reduce parasitoid effectiveness.

We can see a wide range of leaf mine types on our local plants.

Expanded blotch-type mine on poison ivy (the leaves aren’t always 3 leafleted!).

Expanded blotch-type mines on poison ivy (the leaves aren’t always 3 leafleted!).

The outline of a tentiform mine shows on this maple leaf. The mine is on the underside of the leaf, not readily reached from above.

The outline of a tentiform mine shows on this maple leaf. The mine is on the underside of the leaf, not readily reached from above.

According to this research, it boils down to a game of hide-and-seek. If a leaf miner can make its mine complex enough, or in a place where it is difficult to reach, or expand the mine to the point where finding the miner is somewhat needle-in-haystackish, it gains an advantage over the insects that would parasitize and kill it. Furthermore, the diversity of mine types provides a more complex evolutionary puzzle for the parasites as a whole to solve.

Literature Review: Cenozoic Prior to Pleistocene

by Carl Strang

The Cenozoic Era extends from the catastrophe that ended the Mesozoic Era up to the present day. Today’s literature review includes some research published last year pertaining to the bulk of the Cenozoic. Next week I will finish with some Pleistocene studies.

Leaf mine

Winkler, Isaac S., Conrad C. Labandeira, Torsten Wappler, and Peter Wilf. 2010. Distinguishing Agromyzidae (Diptera) leaf mines in the fossil record: new taxa from the Paleogene of North America and Germany and their evolutionary implications. J. Paleont. 84:935-954. Leaf-mining flies’ “mines often can be distinguished from those of other insects by the presence of an intermittent, fluidized frass trail that may alternate between the sides of the mine.” These researchers found an example of this pattern in an early Paleocene fossil sycamore leaf, Platanus raynoldsii, from Montana. They also see in those leaves “associated stereotypical marks identical to damage caused by feeding punctures of extant adult female Agromyzidae prior to oviposition.” This is the earliest fossil agromyzid (the family of these leaf-mining flies), named Phytomyzites biliapchaensis. Sycamores today do not have leaf mining agromyzids. The researchers speculate that this was “an evolutionary, possibly opportunistic colonization in the midst of the ecological chaos following the end-Cretaceous event in North America.”

Antoine, P.-O., et al. Middle Eocene rodents from Peruvian Amazonia reveal the pattern and timing of caviomorph origins and biogeography. Proceedings of the Royal Society B: Biological Sciences, 2011; DOI: 10.1098/rspb.2011.1732     Caviomorph rodents are the group that today characterizes the South American fauna and includes such species as guinea pigs and capybaras. These researchers found fossils of 3 species from 40 million years ago, much older than the previously known earliest South American rodents. The fossils indicate that the origin of that continent’s rodents was a rafting colonization from Africa.

Clarke, Julia A., et al. 2010. Fossil evidence for evolution of the shape and color of penguin feathers. Science 330:954-7. They describe a fossil giant penguin (Inkayacu paracasensis) from Peru, 36 million years ago in the late Eocene Epoch. The penguin’s primary wing feathers were difficult to distinguish from the coverts. Body contour feather shafts were broad like those of today’s penguins, and of similar proportionate length. Melanosomes suggest the colors were gray and reddish-brown.

Mihlbachler, Matthew C., et al. 2011. Dietary change and evolution of horses in North America. Science 331:1178-1181. They measured crown height and microwear of horse molars from the early Eocene on. There was considerable variation in the amount of wear for a given crown height, but in general wear increased with height. They interpret this to mean that selective pressure for increasing crown height generally was weak. There were times, however, when wear was greater, “including the early Miocene shortly before the first appearance of Equinae, the horse subfamily in which high-crowned dentitions evolved.” This supports the connection between the spread of grasslands in the Miocene (grasses are a relatively abrasive food) and the evolution of high-crowned teeth.

Cycad, King’s Canyon, central Australia.

Nagalingum, N.S., et al. 2011. Recent synchronous radiation of a living fossil. Science 334:796-799. They looked at cycad relationships based on molecular comparisons with fossil calibrations. The earlier assumption was that today’s 300 species are a holdover that survived the large drop in diversity in the Jurassic and Cretaceous that occurred with the rise in flowering plants, and thus are “living fossils.” Surprisingly this research group found that today’s species are the result of a diversification that began in the late Miocene, so that they “are not much older than ~12 million years.”

Maple Leaf Miners: Canopy Data

by Carl Strang

Last week I returned to Maple Grove and Meacham Grove Forest Preserves to collect leaf miner data from fallen sugar maple/black maple leaves. Fallen leaves mainly represent what happened in the canopy, and data from them allow me to make comparisons between preserves, between years, and between the understory and the canopy (I had collected understory data earlier in the season).

This year all the leaves had fallen by the time I did the survey.

It was a pleasant day, and I dressed warmly enough that the November weather was no distraction.

In fact, a number of male linden looper moths were flying at Maple Grove. Also known as winter moths, they wait until November to seek mates.

Though the main purpose of the venture was to count leaf mines, I also kept my eyes and ears open for anything else of interest.

I don’t remember noticing this small concrete foundation at Maple Grove before now. It appears to be an old latrine site.

With the leaves largely changed from yellow to brown, leaf mines were easy to see.

Typical leaf litter scene.

I counted 30 leaves at each of 10 randomly selected points on each preserve. Comparisons between canopy and understory counts this year revealed no statistically significant differences at either preserve, except that there were more Phyllonorycter clemensella tent mines in the Maple Grove understory than in the canopy. This species seems more tied to the understory, and seems to be more affected by controlled fall burns of leaf litter. There were no successful burns at either preserve last year, and I suspect that accounts for the statistically significant increase in this species in the understory at Meacham Grove this year. There were no differences between 2010 and 2011 in the canopy for any of the four mine types at either preserve, and there were no differences between the preserves in canopy counts.

Leaf Miners in the Understory

by Carl Strang

Yesterday I reported on one of my herbivory studies at Maple and Meacham Grove Forest Preserves. Today I have the data for the first part of the other study, a decades-long following of 4 leaf miner  genera in sugar and black maples in the understories of the two forests. While attempting to photograph confused ground crickets at Warrenville Grove, I had noticed a high incidence of tent mines, produced by the micro moth Phyllonorycter clemensella.

This photo from Warrenville Grove shows many leaves with one or more Phyllonorycter mines.

Consequently I was wondering if I would find a lot of mines at my study preserves this year. In fact, Phyllonorycter incidences were relatively high in both forests, in 15 percent of understory leaves at Maple Grove and 4 percent at Meacham. Statistically there were more at Maple than at Meacham, which has been true over the years, probably because of more intensive management at the latter site (controlled burning, and culling of maple saplings). Numbers were not different from last year at Maple Grove, but there was a statistically significant increase at Meacham for this species, possibly because there was no burn last year.

The other leaf miners were present in lower numbers that were indistinguishable from last year’s values. The two species of moths in genus Caloptilia, which leave their mines early and construct little cones or boxes in the leaf lobe tips for most of their development, were more abundant at Maple Grove (8 percent incidence) than at Meacham Grove (2 percent of leaves had them). While 3 percent of leaves at Maple Grove had blotch mines of Cameraria saccharella (another tiny moth), none of the 300 leaves in the Meacham Grove sample had any (only one had a mine last year). The fourth mine is distinctive in having a winding linear form.

The linear mine is visible in the lower part of this maple leaf at Warrenville Grove. I have not reared this one; it probably is produced by a caterpillar of the non-native moth Stigmella aceris.

This one was present in low numbers that statistically were indistinguishable between the preserves (8 leaves at Maple, 1 at Meacham). In November I’ll return to assess canopy incidence of these moths.

Maple Leaf Miners, Canopy

by Carl Strang

On Saturday I returned to Maple Grove and Meacham Grove Forest Preserves to complete this year’s measurements of leaf miners in black and sugar maples. Earlier I reported the results for the understory. This time I was looking at fallen leaves to index leaf miner abundance in the forest as a whole. This can be regarded as a measure of these tiny caterpillars in the canopy, in part because the vast majority of leaves grow there and in part because saplings still are holding many of their leaves at this point in the season.

I went to 10 randomly selected points at each preserve and examined 30 leaves per point. The sunny, calm day was good for this as mines can be difficult to see after the fallen leaves have turned brown. I can hold the leaf so the sun shines on each surface, then hold it up so light shines through it.

In the five years that I have taken this measurement I have found few differences between canopy and understory leaf miner abundances. The most common difference is a lower incidence of Phyllonorycter tent mines in the canopy than in the understory, and such was the case this year at Maple Grove. Also at Maple Grove, Caloptilia boxfolds were less common in the canopy than in the understory this year.

All four genera of these tiny moths were in low numbers in the canopies of both preserves. The most abundant were Phyllonorycter at Maple Grove, where I found tent mines on 15 of 300 leaves, or 5%. That was the only species which produced a statistically significant difference between the preserves. In general, populations have been low since I began measuring canopy leaves, so I have yet to see a consistent pattern of differences. The only complete miss this year in understory and canopy combined was an absence of linear mines (probably produced by the non-native moth Stigmella aceris) at Meacham Grove (one turned up in the canopy sample there last year).

I have been interested in the effect of the more intensive management at Meacham Grove on insects and plants I am studying in these preserves. On Saturday I noticed that a burn had been attempted yet again at Meacham.

As you can see, the line of burning fuel dripped along the edge of the trail (which serves as a firebreak) did not take. There still is time for another attempt this fall.

Maple Leaf Miners, Understory

by Carl Strang

In addition to the trailing strawberry bush (reviewed yesterday), I looked at leaf miners on understory sugar and black maples at Maple Grove and Meacham Grove forest preserves last week. As was the case with the other study, I was interested in the potential impact of controlled burning on the populations of the tiny moths whose caterpillars mine the leaves. Even after a year, the burned areas still had essentially no leaf litter.

Unburned areas at Maple Grove, and in a separate, off-study-area forest in Meacham Grove Forest Preserve, had plenty of litter remaining.

The upshot, though, is that I cannot identify any impact of that fire on leaf miner populations. This is not because they are all high, but rather because the four genera of miners have been consistently low at Meacham Grove for 15 years, now. This year, likewise, maple leaves were very clean at Meacham.

That result, I suspect, is more from the sustained intensive management at Meacham Grove over the years, with greater removal of understory maple saplings and more frequent and extensive burning. This is consistent with Meacham Grove’s forest having more of an oak component, a sign that it was exposed more to fire in its early days, fire that would have limited maple reproduction and dominance. The differences I have observed between the two forests in understory leaf miner populations thus may reflect a historically significant difference in the ecologies of the two preserves. Certainly the management at Meacham has produced an increase in botanical diversity of forest floor plants there.

In three of the four leaf miner genera, understory populations were higher this year at Maple Grove than at Meacham Grove. At Maple Grove, Caloptilia were present on 8% of understory leaves (2% at Meacham), probable Stigmella were on 3% (0% at Meacham), and Phyllonorycter were on a whopping 19% of understory leaves (0% at Meacham). The difference in Cameraria blotch mines, on 2% of Maple Grove leaves and 0% of Meacham Grove leaves, was not statistically significant (for more on these insects, go here). Though I did not take measurements, Phyllonorycter tent mines to the eye were much more abundant in the unburned, less managed forest block at Meacham Grove, and thus resembled Maple Grove.

At Maple Grove, two of the four insect groups increased over last year. That 19% figure for Phyllonorycter in fact is the highest since before 1996, and it is the fifth time that population has occurred on more than 10% of leaves in that period. The median annual value in those 15 years has been a healthy 6%. Caloptilia likewise have stayed strong, with a median matching this year’s value of 8%. This year’s frequency of 3% likewise is the median value for Maple Grove (probable) Stigmella. Cameraria has stayed low, with a median of 2% (also this year’s Maple Grove value). The respective medians for Meacham Grove have been 1%, 4%, 1%, and 0%. All of this discussion has been about the understory. The forest canopy may produce different results, which I’ll investigate in November.

Canopy Leaf Miners 2009

by Carl Strang

Recently I reported the results of my survey of black/sugar maple leaves in the forest understory at Maple Grove and Meacham Grove Forest Preserves. Each year I measure the incidence of four groups of leaf miners on those trees at those preserves, continuing a study I began in the 1980’s. Having found very few leaf miners of any type on the low saplings in September, I returned in November to gather data from fallen leaves, nearly all of which come from the canopies of mature trees.

Linear mine on a fallen leaf

As in the understory, canopy leaves had relatively few leaf miners. The highest incidence in any 300-leaf sample was 11 leaves bearing blotch mines of Cameraria caterpillars at Maple Grove. In comparisons between canopy and understory incidences, none were statistically significant. Comparisons between canopies of the two study areas likewise revealed no differences.

I also compared leaf miner incidences between 2009 and 2008. The only statistically significant changes were decreases in Caloptilia boxfolds at Maple Grove, both in the understory (a drop from 42 to 9) and in the canopy (a similar drop from 32 to 9).

It is worth noting that I found low numbers of all four mine types at both preserves this year.

Cameraria mine in a fallen leaf

This is the first time since 2006 that the sample included Cameraria at Meacham Grove.

Understory Leaf Miners 2009

by Carl Strang

In a series of posts last winter I outlined my results to date in a study of several species of leaf mining moth caterpillars that occur on black/sugar maples at Maple Grove and Meacham Grove Forest Preserves. This study, begun in the 1980’s, continues to be worth pursuing; I put in a total of about one full field day per year.

ACNI tent mine b

Tent mine formed by Phyllonorycter larva

One aspect of the study is a comparison of leaf miner occurrence in the canopy versus the understory. Today I’ll report this year’s results for the understory, having gathered those data in September. The story can be told simply, as I found very few leaf miners of any kind at either study area. Out of the 300-leaf samples from each preserve, the greatest number of leaves bearing a leaf mine type was 9 (Caloptilia boxfolds at Maple Grove). That number itself represented the only statistically significant change from 2008, having dropped from 42 leaves in last year’s Maple Grove sample. In comparisons between study areas, only the linear mines which I believe are produced by Stigmella showed a difference. Technically, however, the 8 leaves at Maple Grove versus 0 leaves at Meacham do not meet the criteria for the statistical test I use.

Maple leaves 19SEb

So in the understory the maple leaves were about as clean as I have ever found them. I’ll go out to collect the canopy data soon.

Return to Pachyschelus

by Carl Strang

Last winter I described a leaf-eating beetle, Pachyschelus purpureus, which has a diet contrary to the usual rules governing leaf-eating insects. My past observations have been that, instead of eating a variety of tree leaves, or focusing on a group of herbaceous plants with similar defensive chemistries, this beetle scrapes holes in the surfaces of both wild geranium and bitternut hickory leaves at Meacham Grove Forest Preserve.

Geranium beetle on leaf b

I was interested, then, to read in Missouri entomologist Ted C. MacRae’s blog, Beetles in the Bush, that he has studied beetles in genus Pachyschelus. Through e-mail correspondence I have learned from him that purpureus larvae are leaf miners, known to develop in geranium leaves. Ted encouraged me to continue observing these beetles, to see if indeed there is a particular connection between them and bitternut hickory.

Pachyschelus hickory 2b

The above photo I took in the late summer. I found only a few scattered Pachyschelus this year, and though they were resting only on geranium and bitternut hickory leaves, none were feeding. Thanks to Ted I now know that purpureus adults are known to feed on a variety of tree leaves. My observations simply may be of beetles taking a bedtime snack before finding winter shelter. In the spring they will emerge and lay eggs on larval host leaves. I want to continue studying this beetle at Meacham Grove, however. I want to learn to recognize their mines. Our expectation is that these will be limited to geraniums, but if I were to find them in bitternut hickory as well, that would open the possibility that incipient sibling species, separating to specialize on two separate larval hosts, may be evolving.

Incidentally, take another look at that last photo. While searching for the beetles this year I was struck by the white spots on the elytra, how they resemble eyes (complete with antenna-like extensions). A bird grabbing for the apparent head end might find its beak sliding off the hard pointed tail end of the beetle, which then could escape by flying away in the opposite direction, its dark color in the shaded forest no longer highlighted against a pale leaf.

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