September 19, 2011
Does organic or conventional fertilizer make a difference?

This is an okay study, but nothing too spectacular.  They show there are significant differences in rates of parasitism in the field based upon what fertilizer is being used (John Innes the most,unfertilized and nitram 2nd, and chicken manure with the least) but in Y-tube experiments show no difference in terms of host choice.  What does this say to me?  That parasitoids are picking the aphids that are more fit (bigger), on the plants that are receiving more nutrients.  To me, this study is nothing new.  Does it provide a quandary? I suppose so, showing that in some cases, unfertilized plants are more attractive to natural enemies than those that are fertilized.  What is the reasoning behind this?  There are probably more mycorrhizae in the soil there.

What are your thoughts?  Do you think this is a worthwhile study? 

July 14, 2011
Oyster restoration

A friend of mine from undergrad studies marine biology at Delaware State University.  Check out this article on his research

June 26, 2011

washingtonpoststyle:

motherjones:

Miss USA 2011 contestants on whether evolution should be taught in schools. Just…wow.

This is fascinating. Especially Miss Hawaii’s line: “Everybody should have their opinions taught.”

June 20, 2011
"Zombie Ideas in Ecology"

Since I have been lax with posting as of late (I’m busy!), check out this excellent post over at Oikos blog.

June 13, 2011
The Emerald ash borer OR Release the wasps! Part II

This post is a continuation from my previous post, “Release the wasps (no, really, release the wasps) Part I,” which I put up on Wednesday.  If you haven’t yet read it, please do, as it will provide a bit more context as to what I’m writing about today.

In my earlier post, I wrote about two parasitic, non-native wasps, which I released as a part of the USDA APHIS EAB Biocontrol program.  This post will be used to provide background on the Emerald ash borer and why the decision was made to release non-native wasps in order to control it.

The Emerald ash borer (Agrilus planipennis) is a member of the sun-loving family,Buprestidae (~15,000 known species), commonly known as the Jewel beetles or the Flat-headed borers.  These beetles can be found feeding from the crown downwards, on hardwoods, tending to be specialists, meaning that each beetle will often only feed on a particular species or genera of tree (This specialization is often emphasized in the common name of the beetle, e.g. the Bronze birch borer, Twolined chestnut borer, Bronze poplar borer, Emerald ash borer.)  Behind this specialization are physiological and morphological implications for the beetles.  Organisms that have spent a great deal of time feeding on one, or a few, closely related species will evolve mechanisms that improve their ability to feed upon that species, or genera.

I think it’s worthwhile to break this down and think about it.  Evolution always favors adaptations that improve fitness.

In order to understand how the fitness of the beetle is being changed, I’m going to define a three words I have mentioned, to provide a more clear picture.

What is a mechanism?  A mechanism is a process that achieves a result.

For instance, you may have seen numerous comics or jokes that involve this sort of setup (forgive me for using an academic setup here…),

Step 1. Read papers on topic of interest, decide to study it.

Step 2. ???

Step 3. Publish results!!!

Step 2., is what could be referred to as a “black box,” because one understands the input (the knowledge required to study a topic), as well as the output (publishing a paper on it), and does not necessarily need to know (unless YOU are the one performing the study), the mechanism (or work) that allowed Step 1. to proceed to Step 3.

To be more specific about my usage of mechanism now, I refer to mechanisms that improve a beetle’s ability to feed upon a tree.  A general explanation could be, “evolution,” whereas more specific explanations could be, “larger or smaller mandibles” to chew with, or “chemicals specific to dissolve a particular wood tissue”, etc.

Mechanisms are what generally answer questions such as, “How does X species do Y?”

What is an adaptation?  An adaptation is a particular change in an organisms biology specific to a certain situation.  Examples of adaptations are: the ability to regulate body temperature (These organisms, of which we are one, are known as endotherms), coloration that assists in hiding from, or escaping predators, (also known as camouflage), and the evolution of cognition.

It is important to recognize that in the case of the beetles being able to feed more efficiently, these adaptations ARE the mechanisms which produce the resultant efficiency of particular beetle species performing well on particular trees.

What is fitness? Fitness can be defined in a few different ways, but they all fundamentally refer to the health of the organism.  For the sake of synthesis, I am going to use the Emerald ash borer as an example.  When the Emerald ash borer was first discovered in the United States, researchers performed a study to determine what the “host preferences" of the beetle were.  These preferences refer to its propensity to eat the foliage of, as well as lay eggs upon, and chew into the phloem of particular tree species. (also see: 1,2)  It was found that the Emerald ash borer would occasionally lay its eggs on species aside from ash (Fraxinus spp.), under both laboratory and field conditions, but would only eat ash foliage.  In spite of laying eggs on these non-ash species, Emerald ash borer larave that attempted to bore into the phloem and construct galleries always failed, ultimately ending in death.

To be utterly facetious, death is the complete opposite of fit.  I hope you’re beginning to see where I’m going- there is something about the nature of the tissues within the wood, specific to particular tree species, that makes it difficult, or rather, impossible, for an Emerald ash borer to develop on a non-ash species.

This evokes the concept of a trade-off: if you want one thing, you have to give something else up.  A generalist is able to eat a little of a lot of things, whereas a specialist is able to eat a lot of a few, or one particular thing.

Since the Emerald ash borer is more of a specialist than a generalist, it would be adaptive for it to develop means to eat more ash, and less of other species.  An example of a strategy it MAY (I put this in caps because there is no evidence to this claim, it is my speculation-but, if research were done, I believe results would fall along this line) employ is secreting chemicals via its saliva, that help detoxify tree defense compounds that are specific to ash species.  If this speculation is true, then it would add some context as to why the Emerald ash borer performs so poorly and cannot develop on non-ash species: it doesn’t have compounds to detoxify tree defenses, the defenses overcome the beetle, and therefore, the Emerald ash borer dies.

To finally define fitness in terms of the Emerald ash borer, a fit beetle would lay more eggs and produce more of, and larger larvae, than an unfit, or less fit beetle.  What I just explained above, in terms of fitness, are components that could leads to more fit beetles, with respect to the evolution of the beetle (I say this as I am not taking into account any abiotic or external biotic effects).

Now that I have defined those terms, and given context to the situation, you hopefully understand how beetles which tend to feed on and develop inside of, a few or particular species of tree, may begin to form a close evolutionary relationship with its host, over time.

This close evolutionary relationship is termed, coevolution, also known as the Red Queen Hypothesis.  The Red Queen posits that if one organism is high specialized to another, so that, it could potentially cause the other to go extinct, the second organism must evolve (like a counter-defense), in order to persist.  This leads to the famous Lewis Carroll quote (from which the Red Queen is named),

"…it takes all the running you can do to keep in the same place."

This implies that the two organisms, continue to counter-evolve to each other’s evolutionary adaptations to improve their respective fitness’, in an endless struggle.  Can you imagine ash trees and the Emerald ash borer, over generations upon generations, struggling against one another for dominance?

Most likely you can’t imagine this, because you probably live somewhere in the United States.  One thing I haven’t mentioned yet (that if you are familiar with the Emerald ash borer, you already know), is that the Emerald ash borer is not a species native to North America, it is endemic (native to), East Asia.  Because it isn’t native consider the situation above, regarding coevolution.  There are two possible outcomes: (1) The Emerald ash borer is too specialized upon Asian ash, that it will fail to survive on North American ash or (2) The Emerald ash borer will be able to use its adaptations and feed very heavily upon ash that have NOT evolved defenses to it like its East Asian hosts.

Before I respond to the obvious answer above, I want to note that the Emerald ash borer in East Asia responds to East Asian ash just like our North American Agrilus respond to their respective hosts (you can find some context a few posts back, here), they become noticeable only during stressful events.  What I mean, is that, Agrilus only become a problem when there is a drought, or a flood, or an outbreak of another insect, that weakens the host trees of Agrilus.  Once the trees has less vigor, the beetles go to work attacking the trees.  After the area has had time to recover, the beetles are maintained at low levels and are not an issue until the next big stressful event.

In North America, the Emerald ash borer does not wait until trees are weakened to attack, because it does not need to.  That is why the Emerald ash borer has been deemed invasive and dangerous to the North American ash.

Look at this map of where the Emerald ash borer is as of May 2nd, 2011.  It was only found in Detroit, MI in 2002 (was likely around since 1992, just unnoticed), and has spread rapidly through its own feeding, and most likely, transport of firewood.

Because the Emerald ash borer is so voracious and moves quickly due to various factors, is why biological control (the wasps I released), in conjunction with systemic insecticides, cutting of ash, and environmental education, is being used to slow the spread of the beetle; so that it may be able to be more effectively managed in the future. 

Some Emerald ash borer resources:

www.emeraldashborer.info

Emerald ash borer: Invasion of the urban forest and the threat to North America’s ash resource

The Biology and Ecology of the Emerald ash borer (Agrilus planipennis)

The Chemical Ecology of the Emerald ash borer (Agrilus planipennis)

Cost of potential emerald ash borer damage in U.S communities, 2009-2019

June 13, 2011
Free conservation biology text

This text is full of reputable authors.  Download it and give it a browse

June 8, 2011
Release the wasps! (no, really, release the wasps) Part I

Today, I released a bunch of wasps into a forest in Wisconsin…

Now tell me what sort of image does that conjure up in your head?

BeedrillWell, if you’re of my generation (mid-twenties), it might consist of something looking like the image on the left (Beedrill, for those of you not baptized into the church of Pokemon as children, as I was), multiplied into a swarm of sorts, as the bottom image shows.  While this prospect may seem terrifying/exciting/(insert adjective here), I’m going to break it down for you, I did not release a swarm of Beedrill (is that the plural? Beedrill…Beedrills…?  I know, I’m too tangentially worried about Pokemon.) into a nearby forest.  I apologize to any enthusiast who was hoping his or her dream may have come true.  Sorry.

To move back in the direction of more seriousness, you may wonder why I felt it necessary to go into that whole bit about the Beedrill and wanting to catch all the Pokemon.  I must digress.  Many of our perceptions are shaped by the things in which we most commonly associate them.  When I mentioned “wasps,” you certainly may have thought about Beedrill, or "killer" bees (even though they aren’t wasps), or a recent SyFy original movie.  I wish to dispel that notion and enlighten you a little bit (if I may).

Beedrill swarm Although we are correct when we call this (Paper wasps, Polistes spp.), and this (Digger wasp, Philanthus sp.), and this (Sapygid wasp, Eusapyga verticalis), wasps, they are by far the “only” wasps.  In fact, the family Braconidae is one of the largest, most highly diverse, family of wasps, with estimates from 50,000 to 150,000 species living today.  One may be incredulous at such a claim, but it is in fact true.  Many of these wasps, especially those that parasitize other organisms, can be very cryptic, or difficult to discern against the background of the outdoors.  Additionally those that are parasitic (termed, parasitoids), spend the bulk of their life cycles inside other organisms, hiding them from only those that know where to look.

If you’re still with me at this point, you’ll notice I’ve highlighted a few things:

(1) I released wasps into a Wisconsin forest

(2) Wasps are a diverse group and

(3) We should not immediately associate the term “wasp” with something that is negative to, or will attack humans

Now that I’ve gotten you (hopefully) to reassess your predisposition to cringe (or run and hide), when you hear someone say, “wasp” (and if you already knew all of this stuff, pat yourself on the back and forgive my slow synthesis), I’d like to introduce you the two wasps that I released into the forest today.

The first image on the right is of Spathius agrili, a parasitoid of the Emerald ash borer (Agrilus planipennis) from China.  Although the picture may make it seem rather large and menacing, it’s actually quite small and docile.  To get a good (general) comparison of the size, take one of your hands and look at your pinky nail; the wasp is slightly smaller than that.  This wasp, being a parasitioid has two goals in life (if I may be so bold and anthropomorphize it): first, to mate, secondly, to find the Emerald ash borer’s larval stage, and lay its eggs on it.  A parasitoid that lays its eggs on an external surface of a larvae is known as an ecto-parasitoid.  In the case of this parasitoid (as well as many others that are ecto-parasitioids-but remember there are always exceptions), it is also known as an idiobiont, which is a parasitoid that paralyzes its host after oviposition-preventing it from moving further.  This makes perfect sense- if a parasitoid lays its eggs on the outside of its host, it does not want the host to be able to move and potentially crush or defend itself against the Spathius agrili larvae consuming it.

The second image to the right is another parasitoid from China that lays its eggs in the Emerald ash borer, Tetrastichus planipennisi.  This wasp is even smaller than S. agrili, averaging the size of a grain of rice.  Unlike S. agrili, T. planipennisi is an endoparasitoid, meaning it lays its eggs inside of the larvae, rather than externally.  Because this wasp does not lay its eggs on the outside of the larvae, it has no reason to paralyze it and prevent it from moving.  In fact, the host larvae will continue to feed (and therefore provide nutrition to the eggs and T. planipennisi larvae) until the eggs inside it hatch and consume its innards.  Parasitoids that employ this non-paralysis strategy are known as koinobionts.

What do you notice about these two parasitoids?

Probably that they have two pointy things that look a lot like stingers.  Let me clarify, those are not stingers.  We are looking at two females both of which have a organ called an ovipositor.  What this organ does is allow a female to direct where she lays eggs.  In the case of these two wasps, they both use it to probe the wood of ash trees until they find an Emerald ash borer larvae, in which they then, lay their eggs.  Let me emphasize again, they is an organ to lay eggs; not sting things.

Another thing you may have noticed, is that unlike the Emerald ash borer, these wasps do not have common names, only scientific ones.  This is a result of them being cryptic (as I mentioned above).  These insects were not named as species (giving them formal scientific recognition) until they were found on a survey that specifically looked for natural enemies (I defined this in my previous post, “In search of native Agrilus”) of Emerald ash borer.  This further emphasizes that this insects are harmless to humans- if it doesn’t sting or bite or provide something beneficial, it can go unnoticed.

The purpose of this post was to introduce you to the wasps that I released today and quell the misconception that every wasp is a bad wasp.  What I will do in the second part of this series is introduce you to the Emerald ash borer and explain why wasps from China are being imported into North America to attack (lay their eggs in) it.

June 1, 2011
In search of native Agrilus…

Today I spent my day in a part of the Clark County Forest, girdling northern red oak (Quercus rubra) trees, in hopes of attracting nearby Twolined chestnut borers (Agrilus bilineatus) to them.

After that sentence you may be asking, what exactly is girdling, what are Twolined chestnut borers, and why do I want them?  Well-let me explain.

I study the behavior of and chemical interactions between the parasitic wasps, called parasitoids, that attack and lay their eggs (ala Aliens style, maybe not quite as dramatic, but definitely as cool) inside beetles in the Jewel beetle or flat-headed borers family, Buprestidae, genera Agrilus.  More specifically, I study native (Spathius floridanus) and non-native (Spathius agrili) wasps, in the family Braconidae, and what mediates their ability (I mean, what helps them find, or attracts them) to find hosts.  The hosts that are of interest to me are: three native Agrilus beetles, the Twolined chesnut borer (Agrilus bilineatus), Bronze birch borer (Agrilus anxius), and Bronze poplar borer (Agrilus liragus), and one non-native Agrilus, which has been quite a hot topic for awhile, the Emerald ash borer (Agrilus planipennis).  These beetles can be found on oak (Quercus spp.), birch (Betula spp.), poplar (Populus), and ash (Fraxinus spp.), respectively.

One thing to mention about the hosts of the Spathius spp. wasps.  Spathius floridanus is known to oviposit (or lay its eggs) inside of all four of those beetles. Spathius agrili, on the other hand, only lays its eggs in the Emerald ash borer.  Why is this?  Hopefully I may be able to provide some sort of answer to this question in the future.  Maybe I will speculate on it later.

So now you know what the beetles are, and why I want them; but what exactly is “girdling” a tree, and why do I need to do it?


Girdling a tree is when one creates a gap in the vascular tissue of a tree (xylem, phloem), making it difficult for a tree to receive the water and nutrients it needs in order to survive.  After a tree has been girdled, it usually dies.  Because girdling kills trees, it is often applied as a management option for undesirable tree species (e.g. invasives).  Before it dies, the tree becomes very stressed out (imagine how erratic and crazy you would feel if you could not feed or drink) and releases a bouquet of volatile chemical compounds (low molecular weight chemicals that are gaseous), known as stress volatiles, which signals its poor condition (some- term these, herbivore-induced plant volatiles, or HIPV, when an herbivore attacks a plant and induces a similar, stressed out, condition.  Again, something worth discussing, but not in this post).

Have you figured out yet why I’m girdling these trees?  If not, I’ll tell you.  Insects can sense or perceive chemical signals.  In the case of the Twolined chestnut borer, it can tell when those northern red oaks I cut, are stressed.  Another question that may be on your mind- “why would the Twolined chestnut borer want a stressed out tree instead of a healthy one?”

Well, beetles in the genera Agrilus, in their native habitats, are boom and bust, outbreak species.  They require some sort of (often) abiotic or biotic (inorganic, or organic, non-living, or living, both, respectively) stress event such as a flood, drought, fire, etc., or other insect invasion such as Forest tent caterpillar (Malacosoma disstria) to weaken their host tree defenses, allowing them to attack.  After a period of time, a stressful event subsides, and so does the outbreak of Agrilus beetles, returning them to low, cryptic (hard to find, hidden almost) population levels.

By girdling those northern red oaks, I hope to provide suitable hosts for the low numbers of Twolined chestnut borer.  Am I worried that I may start an outbreak?  No.  These beetles in situations at this latitude (I am referring to the number of days above 50 degrees F), only have one generation per year.  The trees will be cut at the end of the summer or early fall, well before next spring or summer when the beetles would emerge again, allowing me to remove the concentrated populations of the beetles in the trees to a cold room, where the logs will be stored until I need the beetle larvae for experiments.

So, that’s how I spent my day- cutting trees in hopes of scoring the motherload of all beetle densities, that way I can do experiments later in the year.  What did you do?

May 27, 2011
Succint essays on bird biology from Stanford

If we had websites or publications on various organisms with the breadth and clarity of these short essays on bird biology, I think science might actually begin to get through to people.

May 26, 2011
Understanding Evolution

An excellent resource.

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