When cabbage is not cabbage

The cultivars of Brassica oleracea, family Brassicaceae.

Kale, collard, cabbage, cauliflower, broccoli, kohlrabi, and brussels sprouts all seem quite different in appearance and flavor.  Each is used in a different way in cuisine, and one is rarely substituted for another.

All of these vegetables are members of the family Brassicaceae.  This is commonly referred to as the cabbage family or the mustard family.  Plants in this family are largely biennial (require two years to complete a life cycle) and all have four-petaled flowers:

The invasive weed known as garlic mustard (Alliaria petiolata, Brassicaceae) photographed 05/15/2008 near Blissfield Michigan.

But not only are kale, collard, cabbage, cauliflower, broccoli, kohlrabi, and brussels sprouts are all members of the cabbage family, they’re all members of the same genus, Brassica.

But what’s really fascinating, however, is that all of these different vegetables are the same species.  Brassica oleracea is known as wild cabbage, but thousands of years of human cultivation and selective breeding have created all of these different plants.  Humans have bred individual plants with desirable traits in order to create offspring with those traits.  Over time, these traits have been magnified, and now we have individuals very different from one another.  Despite the differences in appearance they can all hypothetically interbreed, so they’re still the same species.

Insect Love: Fireflies

Fireflies (family Lampyridae) lighting up each others' lives.

Despite common usage, it’s not accurate to call these lightning bugs or fireflies since they are neither true bugs (order Hemiptera) nor flies (order Diptera).  I think they should be called “lightning beetles” or “fire beetles” since they’re members of the beetle order Coleoptera (family Lampyridae).

Adult females of some firefly species are larviform (look like larvae) and are commonly referred to as glowworms.  In some other species like the one above they appear similar to males.

Species capable of producing bioluminescence exhibit unique flashing patterns to attract mates.  Some species are known to mimic the patterns of other species for the purpose of luring them as prey.  The individuals above appear to be of a non-light-producing diurnal species, probably in the genus Ellychnia.

Plant-Insect Interaction: Honey bee on goldenrod

Honey bee (Apis mellifera, Apidae) feeding on nectar and collecting pollen from a goldenrod (Solidago sp., Asteraceae). Photographed 08/26/2010 near Clayton Michigan.

Honey bees (Apis mellifera, Apidae) are fascinating to watch.  The phrase “as busy as a bee” certainly has a lot of truth to it.  These bees are constantly moving, buzzing from flower to flower, stopping only for a few seconds to drink nectar and collect pollen.

The bees drink nectar both for their own nourishment and for the production of honey.  They gorge themselves on it and then regurgitate most of it back in the hive, saving only enough for their own needs.  The nectar that is collected at the colony is transformed into honey as the water evaporates from it.  The sugar-rich honey is used for food in the winter.

Pollen is also collected as a food source for larvae.  It’s rich in protein, which is vital to larval development.  Worker bees collect it and place it in pollen baskets (corbiculae) on the tibiae of their hind legs.  Stiff hairs (setae) on their legs help hold the pollen in place until the workers returns to the colony.  You can see the mass of pollen on the corbicula of this worker’s rear left leg.

Honey bees serve as important pollinators of flowering plants (angiosperms) like this goldenrod (Solidago sp., Asteraceae) and, more importantly to us, of commercial crops.  As they collect pollen and move from flower to flower, a little falls off along the way.  Some of the pollen (male gamete) can fall on the stamens (external female reproductive structure) of another flower.  The transport of pollen to the stamen is pollination, but fertilization is required for angiosperm reproduction.  Once a pollen grain reaches a stamen, if it’s sexually compatible it will grow through the pistil to the ovule (female gamete).  Only then can the ovule be fertilized and subsequently develop into a seed.

All worker bees like this one are sterile females.  Male bees (drones) exist only to attempt to mate with the queen (the only fertile female).  This sounds like a great deal for the males, but apparently they get evicted from the hive as winter approaches.  The males only serve to contribute sperm to the queen, and by late in the year the queen has already mated with a select few drones and stored their sperm internally (in a spermatheca).  Since the males no longer serve a purpose, they would be a drain on the colony during the lean winter months.  Outside of the hive the males end up dying, but have probably lived longer on average than the female workers.

Although most people probably think of honey bees when someone says “bee,” they comprise only 7 of the over 20,000 known bee species.  There are no honey bees native to North America;  the species above (Apis mellifera) was brought here by Europeans in the seventeenth century.

Insect-Insect Interaction: Crabronid wasps and treehoppers

Crabronid wasp photographed 07/14/2010 near Clayton Michigan.

This July I noticed a flurry of activity among some wasps (family Crabronidae, possibly of the genus Hoplisoides or Gorytes) outside of my workplace.  They were busy collecting a large amount of paralyzed prey to stock their nests.

Paralyzed treehopper (family Membracidae), photographed 07/14/2010 near Clayton Michigan.

Their choice of prey seemed to be a particular species of treehopper (family Membracidae).  The wasps were probably finding them feeding on nearby trees, where they would have stung them to induce paralysis. The wasps then carried them back to their subterranean nests to place with their eggs.

Paralyzed treehopper (Membracidae) left near the opening of a wasp burrow (Crabronidae). Photographed 07/14/2010 near Clayton Michigan.

These treehoppers are true bugs (order Hemiptera) in the suborder Auchenorrhyncha.  Many Crabronid wasps collect members of this suborder as food for their young.  Since insects in this suborder are usually plant pests to some extent, these wasps seem to be beneficial to us.

I would have liked to get a photo of one of the wasps carrying a treehopper while in flight.  The treehoppers were about as large as the wasps, so it must have been challenging for them.  They seemed to have a little trouble maneuvering in the air, but they got the job done.

After perhaps a week or two, the provisioning activity stopped.  I can only assume the adults went back to sipping on flower nectar while their offspring hatched and started devouring their prey.

Random Plant: Wood nettle

Wood nettle leaves and flowers (Laportea canadensis, Urticaceae), photographed 08/22/2010 in a floodplain forest near Blissfield Michigan.

I’ve found that wood nettle (Laportea canadensis, Urticaceae) seems to be one of the dominant understory plants in at least one local floodplain forest.  Together with stinging nettle (Urtica dioica, Urticaceae) and giant ragweed (Ambrosia trifida, Asteraceae) these large plants create a dense jungle of foliage.

Although wood nettle possesses stinging trichomes like those found on stinging nettle, in my personal experience the sensation isn’t nearly as painful.  In both plants the trichomes are composed of silica (think glass) and when brushed they break off, injecting irritating chemicals into the skin.

Wood nettle seems to serve as great cover for a number of arthropods, especially harvestmen (order Opiliones) and mosquitoes (family Culicidae).  Whenever I walk through the dense stands of this plant, I often stir up large numbers of them.

The larvae of several butterflies also feed on wood nettle.  You can see evidence of herbivory on the lower leaves in the photo above.

Textbook Cross-Bedding

One stop on my final undergraduate geology trip this March included a day at Zion National Park, located in southwestern Utah.  As I mentioned with Death Valley, there is a lot of stuff to talk about here and more will follow in the future.  For now I want to talk about the perfect cross-bedding present in the park.  But first, an obligatory shot of the awe-inspiring oasis that is Zion Canyon:

Drool-inducing view at Zion National Park near Virgin Utah. Photographed 03/10.

The view above is at the bottom of the canyon, where the Virgin River continues to slowly erode away the canyon walls and floor.  An exciting white-knuckle roadway leads up towards the top of the canyon, where there is more to see.  This is where you can see some great cross-bedding:

The textbook cross-bedding in the Navajo Sandstone near the top of Zion Canyon.

Here’s a better look:

The textbook cross-bedding in the Navajo Sandstone near the top of Zion Canyon.

So how did this cross-bedding form?  The Navajo Sandstone was formed from vast sand dunes in the early Jurassic period (almost 200 million years ago).  Sand dunes have a gently-sloping side facing the prevailing wind (windward), and an opposite steep side (leeward).  As the wind moves over the dune, it increases in velocity and picks up sand grains on the gentle windward side.  As the wind reaches the crest of the dune, its velocity decreases and the wind-borne sand grains are dropped.  These grains accumulate on the steep leeward side of the dune.  The dune migrates in the direction of the wind as the sand grains accumulate in layers on the lee side.  Cross-bedding like that above is a cross-section of such deposition.  A graphic may help illustrate this process:

Sand dune deposition, migration, and formation of cross-bedding.

In the third photo above, the three distinct beds represent dune migration to the left, then the right, and then the left again as wind direction changed.

Although not conducive to the preservation of fossils, there have been fossils recovered from the Navajo Sandstone including several cool vertebrates.

Insect Love: Lady beetles

Lady beetles (family Coccinellidae) getting it on. Photographed 08/26/2010 near Clayton Michigan.

I’m going to go ahead and call these lady beetles (order Coleoptera, family Coccinellidae) and not ladybugs.  True bugs are in the insect order Hemiptera, so it seems inaccurate to refer to lady beetles as “bugs.”

The pair above are engaged in what I understand may be up to two hours of mating.  The female then lays fertilized eggs on the undersides of leaves.

I can only speculate that the male took her out for a dinner of aphids (Aphididae) and scales (Coccidae) beforehand.  Lady beetles are important control agents of these plant pests.  Incidentally, aphids and scales are true bugs.

Plant-Insect Interaction: Cabbage white butterfly on giant ironweed

Cabbage white butterfly (Pieris rapae, Pieridae) feeding on nectar from a giant ironweed (Vernonia gigantea, Asteraceae). Photographed 08/22/2010 near Blissfield Michigan.

While the larvae of cabbage white butterflies (Pieris rapae, Pieridae) feed on plants of the mustard family (Brassicaceae), the adults seem to feed any any source of nectar.  Here a cabbage white is feeding on the nectar from a giant ironweed (Vernonia gigantea, Asteraceae).  This cabbage white is a male since it has one black spot on each forewing.  Females have two.

The larvae not only feed on plants of the mustard family, they’re serious pests of mustard plants, especially cabbage.  Farmers refer to them as the imported cabbage worm.

Random Plant: Cup plant

Cup plant (Silphium perfoliatum, Asteraceae), photographed 08/03/2009 in a floodplain forest near Blissfield Michigan.

I found this cup plant (Silphium perfoliatum, Asteraceae) noteworthy because of the interesting leaf arrangement.  The broad, opposite, coarsely toothed leaves come together at the stem in a cup shape (presumably what gives it its common name):

Closeup of the leaves of a cup plant.

The flower is your standard yellow composite:

Flower of a cup plant.

According to the USDA, this is a threatened species in Michigan.  To me, that makes it a cool find.  At the same time, it’s apparently listed as an invasive/banned weed in Connecticut.

Random Insect: Scarab beetle, possibly an earth-boring dung beetle

Beetle of the superfamily Scarabaeoidea, photographed 08/22/2010 near Blissfield Michigan.

I found this beetle trying to burrow underneath a dung pile I wrote about recently.  It’s in the superfamily Scarabaeoidea, and based on morphology and behavior I suspect it’s in the family Geotrupidae (earth-boring dung beetles).  The apparently 11-segmented antennae (unique to this family), 5-5-5 tarsal formula, prominent mandibles, and its affinities for digging and poop are my main evidence.

Scarab beetle with a mouthfull of dirt.

It also has a shiny blue metallic underside:

Scarab beetle unamused by my analysis.

It can be very difficult to identify beetles to any great specificity.  While some are quite unique and easily recognizable (like the Japanese beetles), the vast majority are very challenging to distinguish.  There are over 400,000 known species of beetles, comprising about 40% of all known insects.  The beetle order (Coleoptera) contains more known species than all other animals.  Since the beetle order is one of only about 34 insect orders, you can see that they’re disproportionately represented.

Random Plant: New England aster

New England aster (Symphyotrichum novae-angliae, Asteraceae), photographed 08/26/2010 near Clayton Michigan.

In a prairie full of bright yellow goldenrod (Solidago sp., Asteraceae) this purple New England aster (Symphyotrichum novae-angliae, Asteraceae) stuck out like a sore thumb.

Lessons From the Field #4: Elevation matters

In a continuation of my previous discussion about my trip to Death Valley this March, I wanted to bring up the profound impact elevation has on temperature.  When we arrived at Furnace Creek the first night it was in the 60s Fahrenheit.  This was at an elevation of 190 feet below sea level.  Just before dark I took this picture of some palm trees (family Arecaceae) near the campground:

Palm trees at Furnace Creek. Photographed 03/2010 in Death Valley National Park, California.

That night it snowed in the surrounding mountains:

Snow blanketing the Panamint Range in Death Valley National Park. Photographed 03/10.

The following morning we set out to Dante’s View in the Amargosa Range, some 5500 feet above sea level.  I really wanted to go here, since you can look west and simultaneously see the lowest point in North America (Badwater Basin at -282 feet) and the highest point in the contiguous United States (Mt. Whitney at 14,505 feet).  That would have been really cool.  Unfortunately, this is where the importance of elevation comes into play:

The approach to Dante’s View in Death Valley, photographed 03/10.

The steep gradient and ice- and snow-covered road made travel difficult.  As we approached Dante’s View, the road became even steeper and the van began to slip and slide, and it refused to ascend any further.  We turned back, but not before we had to get out of the van to get it unstuck.  It was then that I was able to appreciate how cold it was at around 5300 feet:

The author freezing to death in the hottest place in North America. To be fair, this was at a significant elevation and not at the notoriously hot sub-sea-level Furnace Creek or Badwater Basin.

And to think I woke up that morning in a t-shirt.  Later that day we ventured to Mosaic Canyon, near sea level, and it was back into the 80s Fahrenheit.

The effect of elevation on temperature is probably mundane to people out west.  To a native of southeast Michigan’s flatlands (glacial lake basin), this was pretty cool to experience.

Plant-Insect Interaction: Black swallowtail butterfly on bull thistle

Black swallowtail butterfly (Papilio polyxenes, Papilionidae) on bull thistle (Cirsium vulgare, Asteraceae). Photographed 08/26/2010 near Clayton Michigan.

Bull thistle (Cirsium vulgare, Asteraceae) is native to Eurasia but it’s present in North America as an invasive species.  It’s also classified as a noxious weed in many states.  Despite this unfavorable status, it has one benefit in that it supplies nectar to insects like this black swallowtail butterfly (Papilio polyxenes, Papilionidae).  This one is a female;  males have a more distinct yellow band on the back of the wings.

Random Plant: Giant ironweed

Giant ironweed (Vernonia gigantea, Asteraceae) photographed 08/22/2010 in a floodplain forest near Blissfield Michigan.

This beauty is a giant ironweed (Vernonia gigantea, Asteraceae).  I found a number of them growing in a small area near the bank of the River Raisin in southeast Michigan.  Here’s a closeup of the infloresence:

Giant ironweed (Vernonia gigantea, Asteraceae) photographed 08/22/2010 in a floodplain forest near Blissfield Michigan.

The flowers seemed to attract a number of butterflies, but I was unable to get a clear shot of any of them.

Random Plant: Cutleaf coneflower

Cutleaf coneflower (Rudbeckia laciniata, Asteraceae) photographed 08/22/2010 in a floodplain forest near Blissfield Michigan.

I recently found this cutleaf coneflower (Rudbeckia laciniata, Asteraceae) in a floodplain forest near Blissfield Michigan.  Here’s a closeup of the flower:

Cutleaf coneflower (Rudbeckia laciniata, Asteraceae) photographed 08/22/2010 in a floodplain forest near Blissfield Michigan.

When I was identifying this plant, what initially confused the hell out of me was the morphology of the leaves and this plant’s proximity to the giant ragweed (Ambrosia trifida, Asteraceae) in the area.  Both plants have three-lobed leaves:

Three-lobed leaf of a cutleaf coneflower (Rudbeckia laciniata, Asteraceae), photographed 08/22/2010 near Blissfield Michigan.

Three-lobed leaves of giant ragweed (Ambrosia trifida, Asteraceae), photographed 08/22/2010 near Blissfield Michigan.

They were growing almost on top of each other in every place I found them.  For a moment I almost thought I was dealing with a single dioecious species:  one that has separate male and female plants for reproduction.  I knew giant ragweed isn’t dioecious, so then the hunt was on to figure out the identity of the yellow-flowered plant.  I knew it was a member of the family Asteraceae, but “DYC” plants (Damned Yellow Composites) can be hard to identify.  Using this site I was able to finally figure it out.

Plant-Insect Interaction: Walnut husk flies on a black walnut

Walnut husk fly (Rhagoletis suavis, Tephritidae) crawling on a black walnut fruit (Juglans nigra, Juglandaceae). Photographed 08/22/2010 near Blissfield Michigan.

These fruit flies are walnut husk flies (Rhagoletis suavis, Tephritidae).  I found a large number of them crawling and flying around the fruit of a black walnut tree (Juglans nigra, Juglandaceae).

Walnut husk fly (Rhagoletis suavis, Tephritidae) crawling on a black walnut fruit (Juglans nigra, Juglandaceae). Photographed 08/22/2010 near Blissfield Michigan.

The flies were probably gathering to mate.  In late summer/early autumn the females lay their eggs in the fleshy outer husk of the walnuts.  The eggs hatch and the larvae eat the husk, but leave the walnut itself unharmed.  Commercially they’re considered pests, since the softened husks complicate the mechanical extraction of the nuts.

Lessons From the Field #3: Don’t feed the !@(*&# wildlife

This past March I went on a great geology field trip across northern Arizona, eastern California, and southern Nevada and Utah.  The biggest stop on the trip involved two days in Death Valley National Park.  This park is huge, and although it’s the hottest, driest, most inhospitable place in North America, there is a ton of cool stuff to see.  Here I’m focusing on why it’s so hot and dry, and how that’s precisely why you shouldn’t feed the wildlife here (or anywhere, but especially here).

Looking north up the valley from Mosaic Canyon.

First, why is this the driest place in North America?  High mountains create a rain shadow effect.  In North America prevailing winds carry clouds eastward.  As the clouds move up over mountains, they tend to release most of their moisture on the windward side.  Once the clouds pass over the mountains, they tend to have low moisture.  In mountainous regions, this rain shadow effect multiplies as clouds travel over each range.  The Sierra Nevada Mountains and the Panamint Range west of Death Valley completely dry out the approaching air in this manner.

Looking southwest across Badwater Basin from the mouth of Natural Bridge Canyon.  The Panamint Range is in the background.

What little precipitation occurs collects in the lowest spots on the valley floor.  The largest such location is Badwater Basin, shown above.  That is indeed water you see, but it’s not fit to drink.  It’s extraordinarily salty…hence the name “Badwater”.  The bottom of the valley is a 200-square mile salt flat.  The enclosed basin collects mineral-rich water that runs off the mountains.  After the water evaporates, it leaves behind these minerals.  Over a great deal of time, they collect into vast deposits.

Salt. Lots of salt.

Next, why is this the hottest place in North America?  Death Valley is the lowest basin in North America’s basin and range province.  Here the crust is slowly being pulled apart by extensional forces.  The crust cracks and forms faults, and some blocks drop along these faults relative to the surrounding blocks.  The dropped blocks form valleys (basin) and the higher blocks form mountains (range).  This alternating basin-range sequence continues for hundreds of miles.

Looking west from the Amargosa Range across Death Valley to the Panamint Range.

Badwater Basin is about 280 feet below sea level.  The large amount of sunshine, high atmospheric pressure, low humidity, and the enclosed nature of the basin help create and trap heat.  It got above 80 degree Fahrenheit in March, and in the summer it gets around 130 degrees in the daytime.

Despite the hostile landscape, a number of organisms make a living here.  Among them are coyotes (Canis latrans, Canidae) that manage to find enough food, water, and shelter to survive.  What doesn’t help them survive, however, is when ignorant people feed them.

Ignorant person tossing food to a coyote in Death Valley National Park.

While this may seem like a nice thing to do (it certainly feeds the animal in the short term), in the long term it actually hurts the animal.  First, animals learn to beg for food from cars, bringing them close to roads where they can get hit.  Second, animals can start pestering humans living and camping in the area, becoming a nuisance and a possible danger that can warrant their extermination.  Third, animals can learn to rely on people for food instead of hunting.

When there are a lot of generous tourists around, things are great for the animals.  Tourism plummets in Death Valley in the summer, however, when few people brave the scorching heat.  Animals that have learned to rely on people for food can suddenly find themselves starving.  This can negatively impact their health and survival, or it can lead them to invade human settlements in search of food.  Once they start harassing and threatening people, they can find themselves on the wrong end of a rifle.  While this is a problem everywhere, it’s especially alarming in Death Valley.

So a note to people like the guy above:  Do the animals a favor and don’t feed them.  They lived here for a long time without your help, and your “help” now may very well kill them.

Three flies on animal dung

Three flies (order Diptera) crawling on animal dung. Photographed 08/22/2010 near Blissfield Michigan.

Most people probably don’t spend several minutes on their hands and knees staring at dung in order to see the flies it attracts.  Luckily I’m not most people.  Here I was lucky enough to capture three different flies on dung simultaneously.  The one on the left is a flesh fly (family Sarcophagidae), and the other two are different species of blow flies (family Calliphoridae).

These fly adults usually feed on flower nectar or rotting fruit.  Here they may be taking advantage of the nutrients still available in the dung.  They may also be looking for a hospitable place to lay their eggs.  Dung is a great food source for growing larvae.

Random Plant: Black walnut

Leaves and fruit of a black walnut tree (Juglans nigra, Juglandaceae), photographed 08/22/2010 near Blissfield Michigan.

The interesting thing about black walnuts (Juglans nigra, Juglandaceae) and walnuts in general is that they’re not true botanical nuts.  They’re actually drupes, much like peaches or plums.  The walnut itself if surrounded by a fleshy husk, similar to a peach pit within a peach.

More specifically, a walnut is actually called a tryma, which is a nut-like drupe.  The “nuts” of hickory trees (also in the family Juglandaceae) are also trymata.

Plant-Insect-Insect Interaction: Goldenrod, Crabronid wasps, and jagged ambush bugs

Today I spent an inordinate amount of time staring at a goldenrod plant (Solidago sp., Asteraceae).  It’s not that I found the plant itself interesting, although it was flowering and rather beautiful.  What drew my attention was the sheer number of insects the plant attracted.  There were a large number of flies (order Diptera), butterflies (order Lepidoptera) and Crabronid wasps (order Hymenoptera) sipping on the flowers’ nectar.

Wasp of the family Crabronidae feeding on the nectar of a goldenrod (Solidago sp., Asteraceae). Photographed 08/22/2010 near Blissfield Michigan.

What really excited me was that I noticed a number of jagged ambush bugs (Phymata sp., Reduviidae) sneaking around amongst the flowers.

Jagged ambush bug (Phymata sp., Reduviidae) on goldenrod flowers. Photographed 08/22/2010 near Blissfield Michigan.

Reduviids aren’t known for sipping nectar, they’re known for eating other insects.  Sure enough, these predators were hiding among the flowers, waiting for the nectar-sippers to get close enough to catch and eat.

Jagged ambush bug sucking the life out of a Crabronid wasp. Photographed 08/22/2010 near Blissfield Michigan.

Jagged ambush bug sucking the life out of a Crabronid wasp. Photographed 08/22/2010 near Blissfield Michigan.

This was completely awesome to watch.  I would have liked to get a video of the action, but it was hard enough to get clear still photos of something so small.