Two Studies in Green

I'm falling a bit behind on processing photos these days (just too much going on outdoors!), and things have been a bit bug-heavy recently, so here's something completely different:

Emerald Tree Boa, (Corallus caninus), Louisville Zoo, 3/28/2013

This is an Emerald Tree Boa (Corallus caninus) from South America. (Well, this one's from the Louisville Zoo, actually.) At least, I think it's caninus. According to a recent paper, there's actually two species that have been historically lumped into this name, (1) and I don't know which one this guy might be.

Green Tree Python (Morelia viridis), Milwaukee County Zoo, 1/15/2012

These are Green Tree Pythons (Morelia viridis) from Indonesia, New Guinea, or northeastern Australia. (These live at the Milwaukee County Zoo.) I say or, because another paper looking at these guys suggests that there may be more than one species here as well. (2) Given how difficult dispersal over the New Guinea mountains or between islands must be, the idea of multiple species here makes a lot of sense.

These two species (or groups thereof) are impressive examples of convergent evolution -- boas and pythons are clearly different families, so the two species in question aren't closely related. Yet they're both similar shades of green, with similar patterning, they're similar in size, and they both rest in that odd looped position. Aside from the range, the easiest way to distinguish them is the size of the scales on the snout. Can their propensity to forming cryptic species also be chalked up to convergence? I rather suspect instead that cryptic species are simply much more common than we've believed.

(1) Henderson, R. W., Passos, P., & Feitosa, D. (2009). Geographic variation in the emerald treeboa, Corallus caninus (Squamata: Boidae). Journal Information, 2009(3).

 

(2) Rawlings, L. H., & Donnellan, S. C. (2003). Phylogeographic analysis of the green python,< i> Morelia viridis</i>, reveals cryptic diversity. Molecular Phylogenetics and Evolution, 27(1), 36-44.

Minty Little Bugs

Just a quick note about a lovely little critter I found yesterday:

Kuschelina gibbitarsa, Gander Mt. FP, Lake Co, IL  5/29/2014

 This is Kuschelina gibbitarsa, one of the Flea Beetles in the family Chrysomelidae. He's a leaf-eater, and I'm afraid I interrupted his lunch. The beautiful color seems very appropriate -- this leaf (and indeed all the leaves he'll eat) is a mint. (Mints are actually quite common in much of North America.)

Many of these chrysomelids are specialist leaf eaters, existing on just a few plant species. Since they are also quite diverse and rather well-known, they've been used to examine theories of coevolution between plants and their herbivores. Futuyma & McCafferty did so with the genus Ophraella, and found no evidence for such coevolution. (1) They concluded that speciation in beetles didn't correlate well with speciation in the plants, and suggested that much of the diversification in beetles happened more recently than diversification with the plants. Farrell & Mitter looked at Phyllobrotica, and they found the opposite, that these beetles apparently diverged in parallel with their host plants. (2) This difference is a beautiful example of how difficult it is to find sweeping generalizations in a world full of history.

This dietary specialization also means that these beetles can be serious agricultural pests. Our usual response to such things is pesticides, which come with their own set of problems. As early as 1972, Tahvanainen & Root demonstrated that a successful alternative is to plant diverse plots of crops. (3) That doesn't work well with our large-scale modern agricultural techniques, but it does with small garden plots. Another possibility, of course, is to release predators of the beetles. Biever & Chauvin suggested stinkbugs, (4) while Hazzard & Ferro examined ladybeetles. (5) (Specifically Coleomegilla maculata, a species we looked at earlier.)

(1) Futuyma, D. J., & McCafferty, S. S. (1990). Phylogeny and the evolution of host plant associations in the leaf beetle genus Ophraella (Coleoptera, Chrysomelidae). Evolution, 1885-1913.

(2) Farrell, B., & Mitter, C. (1990). Phylogenesis of insect/plant interactions: have Phyllobrotica leaf beetles (Chrysomelidae) and the Lamiales diversified in parallel?. Evolution, 1389-1403.

(3) Tahvanainen, J. O., & Root, R. B. (1972). The influence of vegetational diversity on the population ecology of a specialized herbivore, Phyllotreta cruciferae (Coleoptera: Chrysomelidae). Oecologia, 10(4), 321-346.

(4) Biever, K. D., & Chauvin, R. L. (1992). Suppression of the Colorado potato beetle (Coleoptera: Chrysomelidae) with augmentative releases of predaceous stinkbugs (Hemiptera: Pentatomidae). Journal of Economic Entomology, 85(3), 720-726.

(5) HAZZARD, R. V., & Ferro, D. N. (1991). Feeding responses of adult Coleomegilla maculata (Coleoptera: Coccinellidae) to eggs of Colorado potato beetle (Coleoptera: Chrysomelidae) and green peach aphids (Homoptera: Aphididae). Environmental Entomology, 20(2), 644-651.

Flying Scorpions?

Found a cool insect today at Gander Mountain:

Scorpionfly (Panorpa speciosa),

Gander Mt. FP, Lake Co, IL 5/29/2014

This interesting fellow is a Scorpionfly (Panorpa sp.), in the order Mecoptera. I think it's P. speciosa, but there are several other possibilities and they aren't especially easy to ID. The coiled abdomen that gives the group their name is only found in males. They're totally incapable of stinging, though -- that structure is used for mating.

Their mating system has inspired a surprising amount of research, given how infrequently I've managed to find the darn things. (This is my first for Illinois and my third ever scorpionfly.) The concept of fluctuating asymmetry (FA) has been around for some time. While the genes of most animals produce a bilaterally symmetrical result, those genes still have to work in a rather unforgiving environment. Genotypes that are better able to adapt to the surroundings during development should produce more symmetrical individuals, so FA becomes a measure of genetic quality.

This idea has been tested in other organisms -- for instance, Moller found that female Barn Swallows (Hirundo rustica) prefer more symmetrical males. (1) What makes Panorpa so interesting in this regard is that their mating system appears to be driven by pheromones rather than visual signals, so FA shouldn't be something directly selected for. However, Thornhill found that female Japanese Scorpionflies (P. japonica) prefer pheromones from males with low FA, providing strong support for the idea that FA is an honest signal of genetic quality. (2) The polygynous nature of their mating system helps with these sort of studies, (3) since sexual selection is based on differential mating success on the part of one or both sexes, and those differences are usually higher in polygynous species than in monogamous ones.

Actually finding life on another planet would be an amazing thing, and would give a lot of wonderful insights into evolution on Earth. But in the meantime, we don't have to worry about running out of things to learn right here in our own backyards.

(1) Moller, A. P. (1994). Sexual selection in the barn swallow (Hirundo rustica). IV. Patterns of fluctuating asymmetry and selection against asymmetry. Evolution, 658-670.

 

(2) Thornhill, R. (1992). Female preference for the pheromone of males with low fluctuating asymmetry in the Japanese scorpionfly (Panorpa japonica: Mecoptera). Behavioral Ecology, 3(3), 277-283.

 

(3) Sauer, K. P., Lubjuhn, T., Sindern, J., Kullmann, H., Kurtz, J., Epplen, C., & Epplen, J. T. (1998). Mating system and sexual selection in the scorpionfly Panorpa vulgaris (Mecoptera: Panorpidae). Naturwissenschaften, 85(5), 219-228.

 

Pretty Little Wallflowers

Found this little guy on a signpost at a local forest preserve today:

Tmarus angulatus, Van Patten Woods FP, Lake Co, IL 5/28/2014

What the heck are we looking at? It's a spider, specifically Tmarus angulatus, one of the Crab Spiders in the family Thomisidae. They're ambush hunters, waiting in one place for something to wander close enough to grab. Fortunately, they're all tiny enough to be completely harmless to us.

Here's an angle that may be a bit easier to process:

Tmarus angulatus, Van Patten Woods FP, Lake Co, IL 5/28/2014

Being an ambush hunter is well suited to wallflowers -- if you stand out from your environment, your prey isn't likely to come close enough. (You're also more likely to be eaten, of course.) Of course, being a wallflower on a flower can still be attractive enough:

Northern Crab Spider (Mecaphesa atratus), 

Illinois Beach SP, Lake Co, IL  6/2/2012

This is a Northern Crab Spider (Mecaphesa atratus). (At least I think it is -- it's certainly something close.) Like some of their relatives, these guys can slowly change color to match their surroundings, from white to yellow to pink depending on their favorite flowers.

From a researcher's standpoint, an ambush hunter that will spend several days hunting a single inflorescence is a godsend. Trying to examine predation behavior in wild wolf spiders, for example, would be pretty much impossible, given how much ground they cover. With crab spiders, though, you can watch (or even video these days) them for long periods of time, and get really good quantitative estimates of prey preferences, capture rates, and even net caloric intake with different prey types. Morse did this in Maine, looking for evidence of specialization on certain prey types based on optimal foraging theory, and not finding it. (1) I don't know whether he considered the issue of seasonal variation in prey type abundance. He also looked at the effect of flower type on prey capture rates, finding that roses were the least efficient places to hunt, with milkweed beating out goldenrod due to nocturnal captures of moths. (2)

Tmarus isn't a flower specialist -- it tends to wait on twigs and leaves instead. This sort of specialization makes sense, if the substrate makes a difference in capturing prey. Jimenez-Valverde & Lobo extrapolated that to a landscape scale, and found that species richness of crab spiders (and orb-weavers) was largely determined by the diversity of vegetation present in an area. (3) It's easy to see that specialist herbivores will be impacted by changes in plant distributions, but this shows that other species can be affected as well.

When Benoit Mandelbrot coined the word fractal, he was referring to very specific (but very hard to define) mathematical structures. Computer artists have taken advantage of the way that natural structures so closely mimic fractals. The more I delve into ecology, the more I think that ecologists should be doing the same thing.

(1) Morse, D. H. (1979). Prey capture by the crab spider Misumena calycina (Araneae: Thomisidae). Oecologia, 39(3), 309-319.

(2) Morse, D. H. (1981). Prey capture by the crab spider Misumena vatia (Clerck)(Thomisidae) on three common native flowers. American Midland Naturalist, 358-367.

(3) JIMÉNEZ‐VALVERDE, A. L. B. E. R. T. O., & Lobo, J. M. (2007). Determinants of local spider (Araneidae and Thomisidae) species richness on a regional scale: climate and altitude vs. habitat structure. Ecological Entomology, 32(1), 113-122.

Southern Visitors

Courtesy of a wonderful couple in Yorkville, IL:

Black-bellied Whistling-Ducks (Dendrocygna autumnalis), 

Kendall Co, IL 5/26/2014

 These beauties are Black-bellied Whistling-Ducks (Dendrocygna autumnalis). They are native to the southern US, from Louisiana, Texas, and Arizona south to South America. When the Spaniards arrived in Texas, they were apparently quite common there, but they had almost disappeared by the early 1900's. (1) However, habitat alteration in the 1940's and 1950's enabled them to rebound, and by 1964 they were well established in 4 counties in southernmost Texas.

Today, they are a breeding species in much of eastern Texas and Louisiana, and apparently quite regular near Memphis, Tennessee. There are records scattered the length of Illinois -- the birds shown above have been hanging around a housing development just southwest of Chicago for a week now. But if you look at the 1980's, you won't find a single Illinois record on e-bird. (To some extent that may be due to a lack of data as well as a lack of birds.) This is one species that is expanding dramatically as the weather warms.

This has been a constant theme for some time now, actually. Blue-gray Gnatcatchers are now an expected breeding species across all of Illinois and most of Wisconsin, whereas in the 1970's, records are almost non-existent in both NE Illinois and Wisconsin. (Again, limited coverage is part of that, but I've talked to birders from that era that took special trips to Indiana Dunes just to see the breeding gnatcatchers there. Today, it would be a rare forest preserve that didn't have them nesting.) Red-bellied Woodpeckers, Northern Cardinals, Northern Mockingbirds, Blue Grosbeaks, and so on, have all been shifting their ranges northwards over the late 20'th and early 21st centuries.

Now, species ranges can shift for all sorts of reasons. There's been speculation that the winter finch invasions that used to be part of a normal Chicago winter have been sadly reduced because of an increase in people feeding birds in Wisconsin and Michigan, for instance. But when most of the species that you see shifting are all going the same direction, there's something going on that needs to be addressed, and climate change appears to be the only hypothesis going here.

There is one thing neat about this topic -- for many species, we simply can't tell what they're doing. Even if we go out and start looking hard, right now, we wouldn't be able to say that ranges are shifting for quite a few years now. But with birds, we have a nice long history of observations we can fall back on, thanks to the efforts of amateur birders all over the world.

(1) Bolen, E. G., McDaniel, B., & Cottam, C. (1964). Natural history of the black-bellied tree duck (Dendrocygna autumnalis) in southern Texas. The Southwestern Naturalist, 78-88.

A Vision in White

Just a beautiful shot from the Spring Bird Count:

Great Egret (Ardea alba), Wadsworth Prairie FP, Lake Co, IL 5/10/2014

 This is a Great Egret (Ardea alba). Great Egrets are the second largest herons in North America, after the Great Blue Heron (A. herodia). (Egret and heron are different names for birds in the same family -- generally speaking, we use egret for the white ones and heron for the rest.) They are also found across South America, much of Africa, Europe, and parts of Asia.

As with most herons, they eat primarily fish and amphibians. This means that they are quite sensitive to water levels, especially near breeding colonies. Herring, et al. found that nest success rates in the Everglades varied with food availability, although unlike White Ibis (Eudocimus albus) they didn't adjust their clutch sizes to compensate. (1) Trocki & Paton found that the size of salt marsh patches in Rhode Island was a good predictor for how many egrets were to be found in a patch. (2) I'm not sure if they assessed food availability as a function of patch size, though. Wiggins found that egrets that fed in the company of others caught more fish than those that fed on their own, but they usually caught smaller fish, resulting in an equal amount of energy intake. On the other hand, they argued that the energy solitary birds spent chasing other egrets probably meant that solitary feeding was overall less successful. (3) It seems to me that the bird's choice of strategy is probably dependent upon the nature of the fish available wherever they happen to be feeding. So a shift in water levels could affect the available area to feed in, the concentration of various sizes of fish, and the resulting social structure and success rates of the egrets.

(1) Herring, G., Gawlik, D. E., Cook, M. I., & Beerens, J. M. (2010). Sensitivity of nesting great egrets (Ardea alba) and white ibises (Eudocimus albus) to reduced prey availability. The Auk, 127(3), 660-670.

 

(2) Trocki, C. L., & Paton, P. W. (2006). Assessing habitat selection by foraging egrets in salt marshes at multiple spatial scales. Wetlands, 26(2), 307-312.

 

 (3) Wiggins, D. A. (1991). Foraging success and aggression in solitary and group-feeding Great Egrets (Casmerodius albus). Colonial Waterbirds, 14(2), 176-179.

 

 

A Wonderful Little Michigander

Just got back from a week in Michigan, with this guy as the primary prize:

Kirtland's Warbler (Setophaga kirtlandi), Crawford Co, MI 5/23/2014

This is a male Kirtland's Warbler (Setophaga kirtlandi) from Crawford Co, MI. Until a few years ago, Michigan was the only state they bred in, and the bulk of the population still nests there. They only breed in short Jack Pine (Pinus banksiana), from 5 to 20 feet tall, and only in large areas of them. Historically, that's the sort of habitat you'd find after a major fire, but these days fires are put out as quickly as we can, so there's not a lot of habitat left. By the early 1990's, they were down to a potential breeding range of 18 square kilometers, and a population of less than 1000. They have also had problems with a drastic increase of Brown-headed Cowbirds (Molothrus ater) in the area, with nest parasitism rates reaching 70%.

Fortunately, a combination of management techniques has made a big difference in their populations. First, while wildfires are still extinguished in the area, clearcutting is providing large blocks of habitat, on a rotational basis that should be indefinitely sustainable. Second, trapping of cowbirds has reduced parasitism rates from 70% to less than 10%, leading to a population increase, to the point that they are now showing up as breeders in new places. They are now breeding in scattered locations across Michigan's Upper Peninsula, a few locations in Ontario, and two in Wisconsin.

This story has a couple of interesting points, to my mind. First is the idea that clearcutting, often seen as a terrible management technique, actually mimics natural processes here. Second, both the clearcutting and the tourism associated with such a rare bird give residents of the area a stake in the continuing presence of the bird, which can only help with any future management decisions. Finally, while Brown-headed Cowbirds are not an invasive species, their explosive increase in population has been aided by humans, and poses a distinct threat to this species that needs to be addressed. Seeing that addressed so effectively is a hopeful sign, I think.

Little Bits of Sky

Here's a nice find from this morning:

Summer Azure (Celastrina neglecta),
Lyons Woods FP, Lake Co, IL 5/17/2014

This is a Summer Azure (Celastrina neglecta). Well, most likely it's C. neglecta. Not very many years ago, it would have been called C. ladon, the Spring Azure. Today, C. ladon's been split into 8 species, all of them looking very similar to this, and most of them polymorphic, just to confuse things further. In the eastern US, every state has somewhere between 2 and 5 species of azures, all flying at slightly different times and differing in host plants and very minor structural differences. Apparently C. ladon is quite rare up here in Lake County, so even though it's only May, I'll settle for calling this one C. neglecta.

They're called Azures because the males have a bright blue upperside. Females are duller, either pale gray blue or dusky gray depending upon the species. Here's a female Appalachian Azure (C. neglectamajor) showing some of that color. (They rarely hold their wings open when they're perched, making it very difficult to photograph the topsides.)

Appalachian Azure (C. neglectamajor), Powdermill Bird Observatory,
Westmoreland Co, PA 6/13/2004

To better show how closely these species resemble each other:

Lucia Azure (C. lucia), Tussey Mountain Hawkwatch,
Center Co, PA 3/27/2012

This is a Lucia Azure from Pennsylvania.

Echo Azure (C. echo), Mogollon Rim, Coconino Co, AZ 8/2/2005

And this is an Echo Azure from northern Arizona.

These are a great example of what are often called cryptic species. That doesn't mean that they're hard to see, but that they're very hard to tell apart. Obviously, they manage it, but they're likely using clues like UV light or pheromones that we simply can't distinguish. Biologists have found impressive examples of cryptic species in parasitic wasps, finding that what was thought to be one generalist species of wasp was actually a whole host of specialist species, all of which look identical. Each one used just one host species, and they were genetically isolated from each other.

Biologists studying Red Crossbills (Loxia curvirostre) have found that the North American population falls into as many as 9 different groups, which differ by call notes and food preferences and appear to travel in segregated flocks. DNA results across the whole genus show as much individual variation as between-species variation, even though White-winged Crossbills (L. leucoptera) are clearly a good species, and British Ornithologists consider the three forms found in Scotland to all be good species. The American Ornithologists Union has yet to agree to splitting any of the Red Crossbill types, though.

I do suspect that this reluctance isn't something we'd see in entomologists, given the same data, since they're used to the idea of cryptic species. It is true that birds see the world in a way rather closer to our own than insects do, but we've seen evidence of cryptic species in flycatchers already. The ideal of science is to let the data speak while we listen. The reality is that both the questions we ask and the way we hear the answers is influenced to some degree by our backgrounds, both as scientists and as people. That's an important part of the process, but it can make for some interesting quirks in any given field.

Of Moths and Miners

It's been a couple of cool days, so I've been finishing up my grading for the semester. Here's a neat little guy from Wednesday:

Chinquapin Leaf-miner Moth, (Dyseriocrania griseocapitella),
Van Patten Woods FP, Lake Co, IL 5/14/2014

This is a Chinquapin Leaf-miner Moth, (Dyseriocrania griseocapitella). It's in the family Eriocraniidae, which is a rather early split in the modern Lepidoptera.

They are called Leaf-miners because the tiny little caterpillars (less than a centimeter long, even as adults) actually eat oak and chestnut leaves from the inside out. That seems like a difficult thing for a tree to deal with, but this moth seems to be uncommon enough, at least in Lake County, that it's not a serious problem. (Well, this is the first one I've ever spotted, so they can't be too common, right?)

Because of the early divergence of this family from the rest of the Lepidoptera, they've been used at times in phylogenetic reconstructions (1) and investigations of the evolution of moth morphology. (2) Other researchers have used them to investigate the effects of metal pollution on both the moths and their subsequent relationships with fungi. (3, 4)

Given how many critters there are out there, it seems remarkable that no matter how obscure one seems to be, someone's devoted their time to learning all they can about it.

(1) Friedlander, T. P., Regier, J. C., Mitter, C., & Wagner, D. L. (1996). A nuclear gene for higher level phylogenetics: phosphoenolpyruvate carboxykinase tracks mesozoic-age divergences within Lepidoptera (Insecta). Molecular Biology and Evolution, 13(4), 594-604.

(2) Monaenkova, D., Lehnert, M. S., Andrukh, T., Beard, C. E., Rubin, B., Tokarev, A., ... & Kornev, K. G. (2012). Butterfly proboscis: combining a drinking straw with a nanosponge facilitated diversification of feeding habits. Journal of The Royal Society Interface, 9(69), 720-726.

(3) V Kozlov, M., Haukioja, E., & F Kovnatsky, E. (2000). Uptake and excretion of nickel and copper by leaf-mining larvae of< i> Eriocrania semipurpurella</i>(Lepidoptera: Eriocraniidae) feeding on contaminated birch foliage.Environmental pollution, 108(2), 303-310.

(4) Lappalainen, J. H., Koricheva, J., Helander, M. L., & Haukioja, E. (1999). Densities of endophytic fungi and performance of leafminers (Lepidoptera: Eriocraniidae) on birch along a pollution gradient. Environmental Pollution,104(1), 99-105.

Voracious Little Ladies

Here's a nice find from this afternoon:

Coleomegilla maculata, Van Patten Woods FP,
Lake Co, IL 5/14/14

This is Coleomegilla maculata, one of approximately 500 species of lady beetle found in the US. It's a native species, and has played an important role in biological control of aphids in various agricultural settings.

That role is fading, though, because of these two:

Seven-spotted Lady Beetle (Coccinella septempunctatus),
Illinois Beach SP, Lake Co, IL 9/16/2012

This one is the Seven-spotted Lady Beetle (Coccinella septempunctatus), from Europe.

Asian Multicolored Lady Beetle (Harmonia axyridis),
Illinois Beach SP, Lake Co, IL 10/29/2011

And this one is the Asian Multicolored Lady Beetle (Harmonia axyridis), from Japan.

Both of these species were intentionally introduced to the US to try to control aphid pests. (1, 2) While they do appear to be effective in that role, their novelty has allowed first the Seven-spotted and then the Asian to become the dominant members of the family in most locations across the country. After introductions in the late 1980's, the Asian species reached Canada in the early 1990's. (3)

Their spread across the continent has coincided with declines in many of our native species. (2, 4) Although some authors are cautious about the causes of these declines, others have tested the Asian beetles for competition with native ones, finding that the new guests are most likely responsible for much of the decline in two native species: Cycloneda sanguinea in Florida (5) and the species I started this post with, Coleomegilla maculata, in Kentucky. (6)

Most of our conservation efforts (and dollars) go to the big, charismatic vertebrates. But conservation of little arthropods can be just as important. Here we have a passel of native species apparently being driven to scarcity by a couple of invaders that we didn't simply allow in, we invited them. Frankly, if Lady Beetles in general weren't such useful critters, we probably wouldn't have even noticed. Which has to make you wonder what other critters are slowly vanishing beneath our notice.


(1) Tedders, W. L., & Schaefer, P. W. (1994). Release and establishment of Harmonia axyridis (Coleoptera: Coccinellidae) in the southeastern United States. Entomological News, 105(4), 228-243.

(2) Brown, M. W., & Miller, S. S. (1998). Coccinellidae (Coleoptera) in apple orchards of eastern West Virginia and the impact of invasion by Harmonia axyridis. Entomological News, 109(2), 143-151.

(3) Coderre, D., Lucas, É., & Gagné, I. (1995). The occurrence of Harmonia axyridis (Pallas)(Coleoptera: Coccinellidae) in Canada. The Canadian Entomologist, 127(04), 609-611.

(4) Colunga-Garcia, M., & Gage, S. H. (1998). Arrival, establishment, and habitat use of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) in a Michigan landscape. Environmental Entomology, 27(6), 1574-1580.

(5) Michaud, J. P. (2002). Invasion of the Florida citrus ecosystem by Harmonia axyridis (Coleoptera: Coccinellidae) and asymmetric competition with a native species, Cycloneda sanguinea. Environmental Entomology, 31(5), 827-835.

(6) Cottrell, T. E., & Yeargan, K. V. (1998). Intraguild predation between an introduced lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), and a native lady beetle, Coleomegilla maculata (Coleoptera: Coccinellidae). Journal of the Kansas Entomological Society, 159-163.

Ecology On the Ground Floor

Here's a shot from a week or so ago:

Snow Flea (Hypogastrura nivicola),
Illinois Beach SP, Lake Co, IL  5/4/2014

This tiny little guy (~ 2 mm long) is a springtail. I think it's Hypogastrura nivicola, but I wouldn't be surprised to be wrong.

Here's a couple of more springtails:

Homidia socia, Van Patten Woods FP, Lake Co, IL 3/11/2012

This is Homidia socia, identified by the guys at Bugguide.net. He was floating on the surface of a little spring stream.

Sminthurinus henshawi, Van Patten Woods FP, Lake Co, IL 3/29/2014

This one is, I think, Sminthurinus henshawi, also found floating on the surface of that little spring stream. That behavior is actually normal for some springtails. Others live in spaces in the soil, or in downed logs. (Hypogastrura nivicola is also called a Snow Flea. It's not a flea, of course, but it is often found on snow.)

Springtails are arthropods, placed in the order Collembola (at least by some authorities). Despite the six legs, they aren't considered insects these days. They are also incredibly common, especially for critters that most people have never heard of. Joel Greenberg reports on three nearly unbelievable outbreaks that illustrated this. (1) One in Europe actually held up a train by coating the tracks so thickly that the wheels simply spun. One at Northwestern University was estimated at 9 million individuals per square meter. Apply that number to a 1976 occurrence in South Holland that covered two city blocks, and you end up with about 275 billion individuals! What sort of numbers actually live in our forests and fields?

Those sort of numbers have to have some important ecological effects, and a few observers have documented this. For instance, Hanlon and Anderson found that Folsomia candida grazed efficiently enough on fungus that they reduced fungal populations and thereby favored bacterial populations instead. (2)

I remember reading somewhere that we stand about halfway between the size of an atom and the size of the universe -- a remarkable stat. Among living things, however, we're decidedly on the large side, and it's easy to forget that the sorts of ecological processes we see at our scale are happening at the smallest scales as well.

(1) Greenberg, J. (2002) A Natural History of the Chicago Region. University of Chicago Press, Chicago.

(2) Hanlon, R. D. G., & Anderson, J. M. (1979). The effects of Collembola grazing on microbial activity in decomposing leaf litter. Oecologia, 38(1), 93-99.

Wasps with Gall!

Here's an attractive little critter from last week:

Gall Wasp (Cynipidae), Gander Mt. FP, Lake Co, IL  5/3/2014

Gall Wasp (Cynipidae), Gander Mt. FP, Lake Co, IL  5/3/2014

Emphasis on little. This is a Gall Wasp (family Cynipidae), one of 750 species. They earn their name by laying their eggs inside plant tissues, often including the oak trees found where I spotted this one. I don't know which species of plants this one parasitizes, since I have no way of knowing which one it is. (Bugguide shows more galls than adults, at least identified to species.)

Once the plants are parasitized, they form a structure called a gall. Some are simple balls while others can be impressively spiky; apparently many species of wasps can be identified by the form of the gall. (1) These galls are also used as homes by a number of inquiline species, similar to the Ant Cricket from a few weeks ago. The wasp larvae are sometimes parasitized by other hymenopterids as well. On top of all that, in some cases the galls are tended by ants, since they tend to produce honeydew. (2) Put all of this together, and you end up with a rather complicated little ecosystem growing up around these galls.

In the case of the ants, their presence both reduces parasitism rates on the Cynipid larvae and alters which parasites are likely to succeed. (2) Since gall-making comes at a cost to the plant host, (1) a reduction of parasitism on the wasps can't be seen as a good thing from the plant's point of view. This suggests that there's a negative relationship between the ants and the plants, not something I'd have guessed. On the other hand, it's possible that the ants reduce predation directly on the plant, and if so, the overall nature of their relationship could hinge on how important each of those factors is.

Inouye & Agrawal's work (2) focused on Argentine Ants (Linepithema humile), an invasive species from (you guessed it) Argentina. They note that interactions between the wasps, wasp parasites, and native ants show different dynamics, with some interactions dependent upon the density of galls that aren't so dependent with Argentine Ants.

So here we have an introduced ant in a mutualistic relationship with a native wasp, allowing, perhaps, for increased parasitism on a native plant, by reducing the success of other (mostly?) native parasitoid wasps. What effect that has at a slightly higher trophic level would be fascinating to find out.

(1) Stone, G. N., Schönrogge, K., & Atkinson, R. J. (2002). The population biology of oak gall wasps (Hymenoptera: Cynipidae). Annual Review Of Entomology, 47633-668.

(2) Inouye, B. D., & Agrawal, A. A. (2004). Ant mutualists alter the composition and attack rate of the parasitoid community for the gall wasp Disholcaspis eldoradensis (Cynipidae). Ecological Entomology, 29(6), 692-696.

Family Reunions

Illinois birders held their annual Spring Bird Count today, so here's a couple of little jewels for the day:

Yellow Warbler (Setophaga petechia),
Wadsworth Prairie FP, Lake Co, IL 5/10/2014

This is a Yellow Warbler (Setophaga petechia). During migration, you can find them anywhere there's a few trees, but when nesting they're associated with riparian areas, particularly ones with willows.

Philadelphia Vireo (Vireo philadelphicus),
Waukegan Beach, Lake Co, IL 5/10/2014

This is a Philadelphia Vireo (Vireo philadelphicus). If you own an older field guide (say, early 1980's) these two species will be placed close together, with the vireos immediately before the warblers. Here's another shot that shows the similarities a bit more.

Tennessee Warbler, (Oreothlypis peregrinus),
Van Patten Woods FP, Lake Co, IL 9/25/2013

This is a Tennessee Warbler (Oreothlypis peregrinus). They can sometimes cause confusion with some of the plainer vireos, since they are all small, active insectivores with fairly small bills and little patterning on an olive-green body.

In South America, there are several birds in the Vireonidae that are named Peppershrikes, and a few more called Shrike-Vireos. These names came from the resemblance between these birds and shrikes like this one:

Northern Shrike (Lanius excubitor),
Salmon Lake, Nome, AK 8/10/2012

This is a young (and very cooperative) Northern Shrike (Lanius excubitor) from Alaska. At one time, the similarities between vireos and shrikes were considered to be an odd example of convergent evolution. Then ornithologists began to apply DNA technology to the question of relationships within the birds, and that completely revolutionized our view of the order Passeriformes. The oscine passerines (those with more complex voiceboxes and often more complex songs) are now thought to have split fairly early into a couple of infraorders, one including crows as well as shrikes and vireos, the other including most of the passerines we're familiar with here in the US. (In SE Asia and Australia there are quite a few of the Corvoidea families.) That last would include our Wood Warblers. These days, the vireos are now placed very close to the shrikes -- if you have a newer field guide, it will probably put vireos just after the shrikes. Those peppershrikes were rather presciently named, it seems, while the similarities between vireos and warblers are now thought to be due to convergent evolution. Both groups include small, insectivorous, foliage gleaners, so it's not surprising that they're fairly similar in shape and behavior.

Of Flowers and Flies

Here's a nice shot from a windy, warm spring afternoon:

Toxomerus geminatus, Van Patten Woods FP, Lake Co, IL 5/9/2014

This is Toxomerus geminatus, a tiny hoverfly (family Syrphidae). They can be found over most of the warmer months, around here. Here's one from October a few years ago:

Toxomerus geminatus, Illinois Beach State Park, Lake Co, IL 10/22/2011

The adults are nectar feeders, which explains the other name for the group, the Flower Flies. The young, however, are primarily predators on aphids. (1) This has made them useful for agricultural pursuits, and they are sometimes encouraged by "insectaries", flower gardens meant to attract pollinators and predators of pest insects. (2)

Watching various nectar feeders at a flower, it's easy to remember that competition in nature can take all sorts of forms. Morse investigated this idea with various syrphid flies and bumblebees, and found some interesting things. While bumblebees displaced both Toxomerus and Melanostoma flies, Toxomerus immediately returned, and thus there wasn't much of an effect on them. Melanostoma took longer, and lost more time as a result. Melanostoma displaced Toxomerus, and since they stayed at each flower longer than bumblebees, they had more of an impact on Toxomerus. The authors suggested that bumblebee numbers might help regulate Toxomerus numbers by reducing Melanostoma populations through competition. (3)

This sort of cascade effect has been seen in other settings, but in this case, it gives us a better idea for how to manage those insectaries to encourage those species that are most effective at controlling pests. (2) An interesting thought when looking at these little guys with my knees in the grass.

(1) Reemer, M., & Rotheray, G. E. (2009). Pollen feeding larvae in the presumed predatory syrphine genus Toxomerus Macquart (Diptera, Syrphidae). Journal of Natural History, 43(15-16), 939-949.

(2) Ambrosino, M. D., Luna, J. M., Jepson, P. C., & Wratten, S. D. (2006). Relative frequencies of visits to selected insectary plants by predatory hoverflies (Diptera: Syrphidae), other beneficial insects, and herbivores. Environmental Entomology, 35(2), 394-400.

(3) Morse, D. H. (1981). Interactions among syrphid flies and bumblebees on flowers. Ecology, 81-88.

Gender Roles on the Tundra

Here's a visitor to Waukegan Beach this morning:

Dunlin (Calidris alpina), Waukegan Beach, Lake Co, IL 5/7/2014

This is a Dunlin (Calidris alpina), in it's breeding plumage. It's a cosmopolitan shorebird, nesting in high Arctic tundra all the way around the North Pole, and wintering on tropical coasts all over the world. (1) As might be expected, there are quite a few subspecies around the world, with Pyle listing 5 that occur in N. America and mentioning 3 more that don't.

Identifying these guys to species is easy, with the long bill, rufous back and black belly. Figuring out if this one is male or female is much harder, especially if you're not sure which subspecies you're dealing with. Clearly the birds can manage it, of course, and if you're on the breeding grounds, you will usually find that the male is the smaller of a pair. This pattern is called reverse size dimorphism, since in mammals and birds its not the expected situation. In many other groups of animals (and even plants), though, females are normally bigger -- in spiders and some anglerfish, the difference can be truly impressive.

When we do find something odd, it's always interesting to figure out why it happens. In this case, reverse size dimorphism is quite common in shorebirds (sandpipers, plovers, etc.) even though it's rare in other species. One hypothesis for this is known as the Aerial Display Hypothesis, which argues that males are smaller because small body size enables more impressive courtship displays. Blomqvist, et al. used this species to test the idea, and found that, indeed, smaller males could perform longer displays with more hovering. (2) What they don't seem to have showed is that those longer displays led to more breeding success, but it's still an intriguing bit of support for an interesting idea. Owls, hawks, and falcons all show reverse size dimorphism as well, and in hawks and falcons, aerial displays are important both for courtship and for territorial defense. That suggests that this hypothesis could apply to more than just Dunlin.

(1) Hayman, P., Marchant, J., Prater, T. (1986) Shorebirds -- An Identification Guide. Houghton-Mifflin, Boston, MA. 

(2) BLOMQVIST, D., JOHANSSON, O. C., UNGER, U., LARSSON, M., & FLODIN, L. Å. (1997). Male aerial display and reversed sexual size dimorphism in the dunlin. Animal Behaviour, 54(5), 1291-1299.

Not Quite Bees

Here's another take on last night's theme:

Systoechus vulgaris, Illinois Beach SP, Lake Co, IL  7/12/2013

This lovely creature (if you're another one, I suppose) is a Bee Fly (family Bombyliidae), specifically Systoechus vulgaris. While that proboscis looks pretty ferocious, this little critter feeds strictly on nectar and pollen, hovering in front of flowers and looking very bee-like.

Well, it only eats nectar and pollen now -- it used to be a predator of grasshopper eggs! (1)

This is a fairly diverse family, with over 5,000 species spread over 15 subfamilies. (2) Here's a couple more:

Hemipenthes edwardsii, Cimmaron NG,
Morton Co, KS 5/24/2013

This one is Hemipenthes edwardsii.

Villa arenicola, Lyons Woods FP, Lake Co, IL 7/25/2013

And this is Villa arenicola.

Both of these are parasitoids, with females laying their eggs on unsuspecting insects so that their offspring will have a ready-made meal that should last them until they grow up. Hemipenthes, though, is even cooler than that -- in some cases the insects it parasitizes are themselves parasites, specifically certain wasps and sawflies! (3)

It seems odd, perhaps, that such sinister little kids should grow up to be flower-sipping adults. But biology is good at making us see that odd is very much about your point of view.

(1) Berg, V. L. (1940). The external morphology of the immature stages of the bee fly, Systoechus vulgaris Loew,(Diptera, Bombyliidae), a predator of grasshopper egg pods. The Canadian Entomologist, 72(09), 169-178.

(2) http://bugguide.net/node/view/185

(3) Yeates, D. K., & Greathead, D. (1997). The evolutionary pattern of host use in the Bombyliidae (Diptera): a diverse family of parasitoid flies. Biological Journal of the Linnean Society, 60(2), 149-185.

Short Little Lives

My students pulled this little guy out of a small pond on campus tonight:

Damselfly larva (Odonata sp), College of Lake County, Lake Co, IL 5/5/2014

This is a damselfly larva, most likely in the family Coenagrionidae. It's a young one, quite small with no external wing pads present. It may well remain in an immature stage for several months, perhaps even several years, only to spend a few weeks at most as an adult.

This guy follows the same pattern, but even more so:

Hexagenia sp, Van Patten Woods FP,
 Lake Co, IL 6/5/2014

This is Hexagenia, one of the mayflies (order Ephemeroptera). The story, of course, is that they live for only one day. Which is almost true -- as adults, they live for one day or so. But before that one day, they may spend two years as larvae.

There is a strong, natural tendency to interpret other species in human terms -- not surprising, since that's the only background we have to work with. But science has given us a way out, and these guys show why it can matter. It's easy to look at a swarm of mayflies, and think about that one day of life, and forget about those two years as larvae. (Imagine if we spent 70 years as kids, and 2 as adults!) But if we're concerned about damselfly populations, it's crucial that we pay more attention to those years as larvae, since that's where threats to the population are most likely to be operating.

Our Beach Isn't Just for Frisbees!

Here's today's bird of the day:

Piping Plover (Charadrius melodius),
Waukegan Beach, Lake Co, IL 5/3/2014

This beauty is a Piping Plover (Charadrius melodius). They are rare annual migrants through the Chicago area, almost always on beaches along Lake Michigan, on their way either north to Lake Superior or northwest to the Missouri River. There is also a breeding population along the northern Atlantic coast of the US. This particular guy is probably from the Missouri River population, since he's not wearing any leg bands.

They prefer to nest in the sandy upper stretches of beaches, as well as on riverine sandbanks. Needless to say, nesting on beaches tends to bring them into conflict with people. Burger showed that human disturbance impacts where the birds tend to forage and how much time they spend watching out for predators. (1) (While we don't like to think of ourselves that way, any 2 oz. bird has to consider us to be potential predators.) As a result, Piping Plovers are listed as Endangered in Canada, and the US considers the Great Lakes population to be endangered as well, with the Missouri River and Atlantic populations considered threatened. (2)

While conflict with humans and the resulting habitat loss probably account for much of the original decline in Piping Plovers, these days nest predation appears to be an important factor in their continued decline. (3) This seems odd on the face of it -- why would predators play such a part now, when they've been around for as long as the plovers have been nesting?

That question brings us to the mesopredator release hypothesis, where the loss of top predators is said to allow a population increase of smaller carnivores. In the US, that would include skunks (Mephites sp.), Raccoons (Procyon lotor), and Virginia Opossums (Didelphis virginiana), all of which feed on bird's eggs when they can. This hypothesis has a good deal of experimental support, although the process appears to be controlled by more factors than first thought. (4,5,6,7) In the case of Piping Plovers, it might explain why erecting predator exclosures over Plover nests has actually allowed the birds to nest much more successfully (3) and led to increases in all three populations. The Great Lakes population in particular has increased from 39 birds in 1991 (8) to 126 breeding birds in 2008. (2) In 2009, a pair even attempted to nest in Illinois, not far from where I photographed this one. Those birds either abandoned their nest or were predated, but the eggs were taken to Michigan and hatched in an incubator. At least one of those birds has returned to breed in Michigan.

I love watching these little guys, and it's great knowing that they're coming back, so we should be seeing more of them in the future.

(1) Burger, J. (1994). The effect of human disturbance on foraging behavior and habitat use in piping plover (Charadrius melodus). Estuaries, 17(3), 695-701.

(2) http://www.fws.gov/midwest/endangered/pipingplover/index.html

(3) Rimmer, D. W., & Deblinger, R. D. (1990). Use of Predator Exclosures to Protect Piping Plover Nests (Utilización de cercados para proteger nidos de Charadrius melodus). Journal of Field Ornithology, 217-223.

(4) Schmidt, K. A. (2003). Nest predation and population declines in Illinois songbirds: a case for mesopredator effects. Conservation Biology, 17(4), 1141-1150.

(5) Elmhagen, B., & Rushton, S. P. (2007). Trophic control of mesopredators in terrestrial ecosystems: top‐down or bottom‐up?. Ecology Letters, 10(3), 197-206.

(6) Ritchie, E. G., & Johnson, C. N. (2009). Predator interactions, mesopredator release and biodiversity conservation. Ecology letters, 12(9), 982-998.

(7) Johnson, C. N., & VanDerWal, J. (2009). Evidence that dingoes limit abundance of a mesopredator in eastern Australian forests. Journal of Applied Ecology,46(3), 641-646.

(8) Haig, S. M., & Plissner, J. H. (1993). Distribution and abundance of Piping Plovers: results and implications of the 1991 international census. Condor, 145-156.