A Tiny Little Mushroom Connoisseur

Here's a nice find from last summer:

Psychoglypha subborealis, Zion, Lake Co, IL  7/1/2013

This is Psychoglypha subborealis, a large caddisfly (order Trichoptera). Caddisfly larvae are aquatic, and most of them are quite intolerant of pollution, so finding this guy here appears to be a sign that at least some of our local wetlands are in good shape.

Caddisfly larvae are famous for constructing cases out of whatever debris is available around them, binding the stuff together with silk. There's a good deal of variation in this behavior, both in terms of the size and shape of the structure itself and the point in development when it's constructed. Some species wait until they're ready to pupate, but apparently this species builds it's cases soon after hatching.

Caddisflies also vary in their food preferences, with this species being known as a leaf shredder. Arsuffi & Suberkropp looked into this at a finer scale in the 1980's, finding that they preferred leaves that had been colonized by certain species of fungi. (1) Furthermore, the preferred level of pre-digestion by the fungi appeared to vary with the fungal species. They were even able to demonstrate that the larvae are distinguishing between fungi on different parts of the same leaf. (2)

The guiding assumption behind their initial work seems to have been that the processing of the fungi improved the quality of the leaves as a food source. However, further research suggested instead that the larvae actually gain more nutrition from the fungus than they do from the leaves themselves, suggesting that the food preferences they initially reported were based as much on the status of the fungi than on the leaves. (3)

I don't see any larger conclusions to draw from these studies, but this sort of detail is why biology remains such a fascinating topic.

Arsuffi, T. L., & Suberkropp, K. (1984). Leaf processing capabilities of aquatic hyphomycetes: interspecific differences and influence on shredder feeding preferences. Oikos, 144-154.

Arsuffi, T. L., & Suberkropp, K. (1985). Selective feeding by stream caddisfly (Trichoptera) detritivores on leaves with fungal-colonized patches. Oikos, 50-58.

Arsuffi, T. L., & Suberkropp, K. (1988). Effects of fungal mycelia and enzymatically degraded leaves on feeding and performance of caddisfly (Trichoptera) larvae. Journal of the North American Benthological Society, 205-211.

The Beaches are Filling Up!

First shorebird of the year!

Killdeer (Charadrius vociferus), Illinois Beach SP, Lake Co, IL  3/14/2014

This is a Killdeer (Charadrius vociferus). (They don't really hunt deer, that's a rendering of one of their common calls.) They occasionally winter as far north as Chicago, so it's probably not surprising that they are typically one of the first back in the spring, occasionally showing up here in Lake County in late February. They are also one of three species of shorebirds that breed commonly in this area -- most of our shorebirds nest either along the coast or on the Arctic tundra, with several more species using the boreal forests of Canada and Alaska.

Given that they are common, widespread, and conspicuous, it's hardly surprising that they've been the focus of quite a bit of research. Some of that has focused on migration and wintering behavior, but much of it has focused on this stage of their life:

Killdeer (C. vociferus) nest, N. Pt. Marina, Lake Co, IL,  5/26/2003

This, obviously, is a Killdeer nest -- and yes, they really do just dig a bit of a scrape in the gravel, and trust mostly in the camouflage pattern on the eggs to hide them when neither parent is on the nest. This is a monogamous species where both parents incubate, and if a female loses her mate, she is usually unable to hatch the eggs on her own. (1, 2) Males can manage to reach hatching, but even then their success rate is considerably lower.

We usually expect male and female animals to put equal amounts of energy into reproduction, although they allocate it differently. In Killdeer, males put more energy into mating displays, and females put more energy into the actual reproductive effort. (Eggs are expensive.) Both sexes put equal amounts of energy into parental care. But since their nests tend to fail at a rather high rate, females end up putting more energy, on average, into a given nesting season. (2) Probably as a result, they spend more time foraging than males. (1) Put it all together, and we have a nice neat explanation for why they are monogamous. Since females are unable to raise offspring without help, any male that doesn't stick around won't leave any offspring at all, no matter how successful he is at mating.

Surprisingly, in shorebirds, some polygamous species are polyandrous, meaning that one female mates with several males. Most polygamous species of birds are polygynous, which makes sense since the females are the ones putting lots of energy into producing eggs and raising offspring. But as we saw with the Killdeer, many species of shorebirds have males that put a lot of energy into raising their own offspring. So the system best known in Phalaropes can evolve, with females competing for multiple males.

When we see this sort of thing in the usual way, sexual selection often ends up producing bright, colorful males and dull, drab females. Here we have a test: if females are competing for males, they should be the bright ones. And what do we see?

This is a male Wilson's Phalarope (Phalaropus tricolor).

Wilson's Phalarope, (Phalaropus tricolor),
Quivira NWR, Stafford Co, KS 5/23/2013

And this is a female Wilson's Phalarope:

Wilson's Phalarope (P. tricolor),
Quivira NWR, Stafford Co, KS 5/23/2013

Sharp-looking bird, isn't she?

When we're using the comparative method to examine theoretical predictions, we need a speciose group with considerable variation in the traits we're interested in. Frequently, the shorebirds fit the bill.

And the first Killdeer of the season is always a welcome reminder of spring!

Killdeer (C. vociferus), N. Pt. Marina, Lake Co, IL  3/31/2013

(1) Brunton, D. H. (1988). Sexual differences in reproductive effort: time-activity budgets of monogamous killdeer,< i> Charadrius vociferus</i>. Animal Behaviour, 36(3), 705-717.

(2) Brunton, D. H. (1988). Energy expenditure in reproductive effort of male and female Killdeer (Charadrius vociferus). The Auk, 553-564.

Little Shells, Big Problems.

Now that we're able to see the ground again, here's something from the beach at North Point Marina:

Zebra Mussel (Dreissena polymorpha),
N. Pt. Marina, Lake Co, IL 2/23/14

Actually, I could have gotten this shot at just about any beach in the area -- it's a Zebra Mussel (Dreissena polymorpha). They're native to Europe, where they're quite widespread. The first discovery in North America occurred in 1988, and that initial publication predicted that they would likely spread throughout the Great Lakes. (1) They were right! The same life history traits that produced their widespread native range has allowed them to spread rapidly here, and they now are abundant throughout the Great Lakes and the Mississippi River basin. They don't get very big, just an inch or so long, but they grow in dense colonies that cover just about any hard surface. They cause economic issues by fouling water intakes and similar structures.

They also cause a host of ecological changes -- they are very efficient filter feeders, and increase water clarity by removing phytoplankton. (2) They also cover native mussels and clams, causing steep declines in many of them. (3) Given that 60% of the 297 known species of freshwater mussels in the US are considered endangered, with an additional 12% already presumed extinct, this is a serious problem. (3,4) Illinois alone has 16 species that are listed by the state, seven of them also on the Federal Endangered Species list. (5) It seems likely that we will lose all of them in the near future. (4) (Most of this work was done in the 1990's, so I don't know how many have disappeared in the meantime. The Illinois numbers are based on the most recent revisions to the Endangered Species List, in 2011, but I can't find any older versions to compare to.)

Surprisingly, finding additional research on this species published since 2000 isn't especially easy. Either they've somehow stabilized or we've mostly moved on to other crises.

There are, of course, things that eat Zebra Mussels, even here, and here's one of them:

White-winged Scoter (Melanitta fusca), Pleasant Prairie Yacht Club,
Kenosha Co, WI, 2/23/2014

This is a White-winged Scoter (Melanitta fusca). They're a large sea duck that breeds across Canada and winters mostly on the coasts, but some do spend the winter on the Great Lakes. Zebra Mussels seemingly provide an easy food source, so I would have expected an increase since the early 1990's in the state. However, CBC numbers don't back that up -- both White-winged and Surf Scoter (M. perspicillata) numbers decline rather dramatically at just about the time that the mussels were getting started here. (6) Either they prefer larger food, or there's something else entirely going on with them.

(1) Griffiths, R. W., Schloesser, D. W., Leach, J. H., & Kovalak, W. P. (1991). Distribution and dispersal of the zebra mussel (Dreissena polymorpha) in the Great Lakes region. Canadian Journal of Fisheries and Aquatic Sciences,48(8), 1381-1388.

(2) MacIsaac, H. J. (1996). Potential abiotic and biotic impacts of zebra mussels on the inland waters of North America. American Zoologist, 36(3), 287-299.

(3) Schloesser, D. W., Nalepa, T. F., & Mackie, G. L. (1996). Zebra mussel infestation of unionid bivalves (Unionidae) in North America. American Zoologist,36(3), 300-310.

(4) Ricciardi, A., Neves, R. J., & Rasmussen, J. B. (1998). Impending extinctions of North American freshwater mussels (Unionoida) following the zebra mussel (Dreissena polymorpha) invasion. Journal of Animal Ecology, 67(4), 613-619.

(5) http://www.dnr.illinois.gov/ESPB/Documents/ETChecklist2011.pdf

(6) National Audubon Society (2010). The Christmas Bird Count Historical Results [Online]. Availablehttp://www.christmasbirdcount.org [3/13/2014]

The Great Exchange

Invertebrates in lecture today, so here's a find from last summer:

Anacalonia conica, Zion, Lake Co, IL 8/22/2013

This is Anacalonia conica, a planthopper in the family Anacalonidae. They're native to the eastern US, where they live by sucking the sap of plants. (1)

So what is this one?

Codling Moth (Cydia pomonella), Zion, Lake Co, IL 6/27/2012

This is a Codling Moth (Cydia pomonella), a European moth whose larvae feed on apples. (2)

What do they have in common? They're both introduced species!

Wait, wait, you may be thinking -- the hopper's native, right? Right -- it wasn't introduced here. Rather, it was introduced into Italy in recent years. (3) We tend to think of introduced species as coming from Europe to the Americas -- feral pigs, cheat grass, House Sparrows. But the great exchange across the Atlantic (and now around the world) goes both ways. Here are a couple more species that came from Europe:

European Starling (Sturnus vulgaris),
 National Aviary, Pittsburgh, PA 3/28/2012

Teasel (Dipsacus fullonum), Sedge Meadow FP, Lake Co, IL 8/5/2006

And here's a couple that went over to Europe.

Gray Squirrel (Sciurus carolinensis),
Lyons Woods FP, Lake Co, IL 11/7/2012

Grass-leaved Goldenrod (Soldago graminifolia),
Illinios Beach SP, Lake Co, IL 10/2/2011

Historians will tell you that crops, cultures, and people crossed back and forth quite a bit, often in surprising ways. (The quintessential American meal, Thanksgiving dinner, includes foods from North America (turkey, pumpkins, cranberries), South America (potatoes, sweet potatoes), and Eurasia (wheat for breads and pies, sugar), while Irish potatoes, Italian marinara sauce, and Thai hot peppers all started off as New World crops.) What shouldn't be surprising, but somehow still seems to be, is that we took a bunch of not so wanted critters with us.

(1) http://bugguide.net/node/view/15671

(2) http://bugguide.net/node/view/67544

(3) D'Urso, V., & Uliana, M. (2006). Acanalonia conica (Hemiptera, Fulgoromorpha, Acanaloniidae), a Nearctic species recently introduced in Europe. Deutsche Entomologische Zeitschrift, 53(1), 103-107.

Treetop Dining?

A short walk at Lyons Woods FP today produced no new birds for the year, but you could tell someone had been busy:

These are the cones from Norway Spruce trees, planted there while the property was still a tree farm. Here's what one looks like close up:

Norway Spruce cone (Picea abies), Lyons Woods FP, Lake Co, IL 3/10/2014

Quite a few of them, though, looked like this:

What's going on here?

These are the leftovers from this guy's breakfast:

Gray Squirrel (Sciurus carolinensis), Lyons Woods FP, Lake Co, IL 11/7/2012

Here's one he just got started on:

But why are they on the ground? Squirrels can climb -- surely it makes sense to eat in the trees where it's safer?

I can't say for sure with Gray Squirrels, but with Red Squirrels like this one, someone found very interesting behaviors in this regard.

Red Squirrel (Tamiasciurus hudsonicus),
Alaska Zoo, Anchorage, AK 8/12/2012

Red Squirrels spend the morning and evening hours up in the treetops, cutting cones off and simply dropping most of them to the ground. In the middle of the day, they come down to the ground and collect them, actually eating them on particular posts. When you see a well-used post, it's quite noticeable -- there's cone scales piled up around for several feet.

So again, what's the point? In the morning, it's nice and cool up in the treetops, and the sun is falling on them and warming things up. As the sun gets higher and things start to really heat up, the squirrels move down to the well-shaded ground to avoid the heat. By dropping the cones, they provide themselves with a meal that they can take all day to eat.

The demands on a wild animal's life are often obvious -- a Cooper's Hawk in hot pursuit of  a squirrel isn't something you're likely to miss. Many selective pressures, though, are much more subtle, and we shouldn't be surprised when the adaptations to them are similarly hard to spot.

Trees that talk?

Still lots of snow, but still managed to get out, and here's some leftovers from last summer:

Gray Alder (Alnus incana rugosa), Van Patton Woods FP,
Lake Co, IL 3/9/2014

Gray Alder (Alnus incana rugosa), Van Patton Woods FP,
Lake Co, IL 3/9/2014

These are male (skinny) and female (round) catkins from a Gray Alder, (Alnus incana rugosa). Although they look like hemlock cones, alders are actually flowering plants. In contrast to birches or willows, though, these catkins develop woody tissue and remain on the tree through the winter.

Alders are interesting plants. They grow nodules on their roots that host nitrogen-fixing bacteria (1), just as legumes do, so they enrich the soil where they grow.

They also, apparently, talk to each other! When European Alders (A. glutinosa) are attacked by leaf beetles (Agelastica alni), they alter their leaf chemistry, adding phenols and increasing the activity of various oxidative enzyme pathways. They also emit ethylene and various terpenes. Beetle activity after this occurred was found to decrease not only on the affected tree but on trees some distance away, as did other specialist herbivorous insects. Generalist herbivores were apparently not affected. When other trees were exposed to the mix of emitted chemicals, they saw similar results, even though those other trees hadn't been attacked. (2) The authors rightly point out that this is a form of communication -- between trees!

Tolkien may have exaggerated their liveliness, but apparently trees can talk to each other.

(1) Akkermans, A. D. L. (1971). Nitrogen fixation and nodulation of Alnus and Hippophaë under natural conditions. Meded. bot. Lab. Rijks-Univ., Leiden.

(2) Tscharntke, T., Thiessen, S., Dolch, R., & Boland, W. (2001). Herbivory, induced resistance, and interplant signal transfer in Alnus glutinosa.Biochemical Systematics and Ecology, 29(10), 1025-1047.

Clams Adrift on Ancient Currents

Here's a shot from the Shedd Aquarium in Chicago:

Giant Clam (Tridacna gigas), Shedd Aquarium, Cook Co, IL 1/20/2013

This is a Giant Clam (Tridacna gigas). They're normally found in the Indo-Pacific region, but are decreasing due to over-harvest for food and shells.

Since they're sessile as adults, it isn't surprising that they practice external fertilization. Their offspring typically float for approximately 2 weeks, if they can then find a suitable bottom to settle onto and start growing. As they grow, they capture algae known as zooxanthellae, which provide food through photosynthesis, and thereby increase the clam's growth rate considerably. (1)

Given the sort of broadcast spawning that this species and it's relatives practice, we should expect populations to show fairly little geographic variation in genetic structure, and indeed this is the case, with the entire 600 mile length of the Great Barrier Reef showing no such variation. (2) On the other hand, long-distance dispersal is probably fairly rare, so it's probably not surprising that widely separated populations show more genetic differentiation, at least in the related T. derasa. (3)

What was surprising is that in both this species (4) and the closely related T. maxima, (5) genetic dispersal events appear not to have followed modern surface currents! Clam larvae are definitely planktonic, so they're not swimming against currents in any meaningful sense, so unless they're somehow using deep-water currents, we're seeing the results of rather old events. Of course, Giant Clams can live over 100 years, and successful recruitment of such a long-lived species is typically quite low, so I guess it shouldn't be surprising that such echoes of the past are still visible.

Biologists are trained to consider the history of the organisms they're working on. Geologists are trained to consider the history of the Earth that those organisms live on. Mixing the two can't help but give us insights into this world we're all drifting through space on.

Jameson, S. C. (1976). Early life history of the giant clams Tridacna crocea Lamarck, Tridacna maxima (Roding) and Hippopus hippopus (Linnaeus). Pacific Science, 30(3), 219-233. 

Benzie, J. A. H., & Williams, S. T. (1992). No genetic differentiation of giant clam (Tridacna gigas) populations in the Great Barrier Reef, Australia. Marine Biology, 113(3), 373-377.

Macaranas, J. M., Ablan, C. A., Pante, M. J., Benzie, J. A. H., & Williams, S. T. (1992). Genetic structure of giant clam (Tridacna derasa) populations from reefs in the Indo-Pacific. Marine Biology, 113(2), 231-238.

Benzie, J. A. H., & Williams, S. T. (1995). Gene flow among giant clam (Tridacna gigas) populations in Pacific does not parallel ocean circulation.Marine Biology, 123(4), 781-787.

Benzie, J. A., & Williams, S. T. (1997). Genetic structure of giant clam (Tridacna maxima) populations in the West Pacific is not consistent with dispersal by present-day ocean currents. Evolution, 768-783.