Tuesday, February 16, 2010

What is a species?

Those who belong to the official lichen listserve, 'LICHENS-L', may remember a few months ago when someone threw out the fact that some biologists have adopted the notion that "There is nothing unique or special about the 'species' as a taxonomic rank".  This idea is not in any way unique to lichenology, but within that forum I gave the following response:

There is no question that genetic recombination creates forces that maintain uniformity and keep members of 'species' morphologically and molecularly similar to one another; this is not the case for higher taxonomic ranks, where similarity within a group can generally be attributed only to common ancestry or ecology.  When these forces break down permanently because of some reproductive barrier, we generally call that a 'speciation' event.  This is obviously based on a Biological Species Concept (BSC) which says that a 'species' is essentially a group of interbreeding individuals reproductively isolated from other such groups.  From my perspective, that is the only 'real,' justifiable species concept.  However, other species concepts (e.g., phylogenetic, morphological) are perfectly valid in that they provide excellent insight into what the groups of interbreeding individuals are likely to be (this is usually very hard to demonstrate experimentally, so the BSC is often not practical from a scientific standpoint).

Of course, this leaves out asexual organisms, and those must be pigeon-holed because the species are not 'real' (i.e., they do not represent anything uniquely different from any other taxonomic rank).  In these cases, species merely become names for phylogenetic entities possessing shared innovations that have altered the course of their evolutionary history (still valid, but no different from genera, families, etc.).

We must also not forget hybridization, polyploidy, etc., which can throw a wrench into the system.  These events can have major effects and cause instant 'speciation' (reproductive isolation) even though they are seemingly quite rare.  In some cases you can get new species with multiple progenitor species.  We have good examples of this in plants, but I really wouldn't be surprised to find all sorts of crazy things that we just do not know about yet happening in the fungi!

If your perspective is only phylogenetic, then it is true that 'species' often do not show up clearly and distinctly as special units per se.  However, if you can analyze a combination of molecular, morphological, ecological, and geographical features of organisms, then you can begin to infer 'biological species' by assuming that there are forces maintaining some degree of uniformity within each unit (but as I implied above, this is not always a sound assumption).

There is no doubt that the question of 'what makes a species' is a difficult one (the evidence for this is in the fact there there are so many well-accepted 'species concepts'), but it does not mean that we should throw out our species concepts and simply say that 'species' is just another taxonomic rank like any other.  If we do this, we are likely to miss the significance of certain phenomena that take place all around us in the natural world.

-Brendan Hodkinson, Duke University

Tuesday, February 9, 2010

Top Lichens

Dr. Robert L├╝cking (Field Museum, Chicago) recently asked lichenologists to send in a list of their top 5-20 favorite lichen species.  Along with Dr. Thorsten Lumbsch (also of the Field Museum) and others, he plans to assemble a list of 100 lichens, and eventually each will be featured on a website with its own page full of photos and information about the species.  Feel free to peruse my current top 20 lichens; each name has a link to a photograph of the species.

Arthonia caesia
Brigantiaea leucoxantha
Calicium trabinellum
Chaenotheca furfuracea
Cladonia bellidiflora
Conotrema urceolatum
Dibaeis baeomyces
Glyphis cicatricosa
Gyalideopsis buckii
Herpothallon rubrocinctum
Masonhalea richardsonii
Niebla cephalota
Ochrolechia oregonensis
Pilophorus clavatus
Placopsis lambii
Solorina crocea
Sphaerophorus globosus
Stereocaulon ramulosum
Umbilicaria cylindrica
Usnea longissima

I look forward to seeing how this project evolves!  It will be a great way to reach out to those outside of the field of lichenology and demonstrate the beauty and diversity of lichen-forming fungi!

- Brendan

Wednesday, February 3, 2010

Tasty Fungi

Over the past few days I've been trying out some new recipes with my wife and we came up with this one that seemed to be worth sharing!  It's loosely based on a recipe from a 2003 issue of Vegetarian Times, picked up from a library book sale (though we have so altered it that I'm not sure that it would be clear what it's based on anyway!).  The dish is called 'Mushroom Couscous Cakes' and it ended up being much better than either of us expected.  My wife made it clear from the start that she was skeptical, since she says that she does not like fungi, but once she tasted it she changed her mind!

This recipe seems to work best in a less formal setting, since the cakes are amazing when they first come off of the skillet, and it may be best for some people to start eating while others are waiting for their cakes to be prepared.  I highly recommend porcini mushrooms in the cakes, but the mushroom mix that goes on top could be made with any number of different types of fungi (e.g., chanterelles, morels, creminis/portobellos, etc.... I wonder if it could work with Umbilicaria....); we had shiitakes in our kitchen and they were great!

Mushroom Couscous Cakes

Serves 4

1/4 oz. dried porcini mushrooms
1/2 cup couscous
1/2 onion, chopped
1/2 tsp. salt
1 egg
1 Tbs. all-purpose flour
Extra virgin olive oil, as needed

Mushroom Mixture:
1 Tbs. extra virgin olive oil
1/2 lb. cleaned, dried shiitake mushrooms
Salt and freshly-ground pepper to taste
1/2 onion, finely chopped
1 clove garlic, finely chopped
1/3 cup dry white wine
1 Tbs. butter
1/4 tsp. Cavender's All-Purpose Greek Seasoning (a mix of salt, pepper, corn starch, garlic, MSG, and oregano)

To prepare dried mushrooms:
Put each type of mushroom in its own separate bowl, fill each bowl with warm water, squeeze mushrooms, pour off water, and repeat several times until mushrooms are reconstituted and the water remains somewhat clear when mushrooms are squeezed.

To make batter for cakes:
Chop porcini mushrooms very fine. Place couscous, 1/2 onion, salt, chopped porcini mushrooms, and 1 cup of water in a small saucepan.  Bring to a simmer, cover and reduce heat. Cook for 25 minutes or until couscous absorbs all liquid.  Transfer to mixing bowl and cool.  Stir in egg and flour.

To make mushroom mix:
Heat olive oil in large skillet over medium-high heat.  Add mushrooms, season with salt and cook, tossing from time to time, until mushrooms release moisture and begin to brown.  Add onions and garlic, cook 1 minute more and add wine.  Continue to cook until only a small bit of liquid remains.  Stir in butter and seasoning mix.  Transfer to bowl/saucepan and keep warm while making cakes. 

To make cakes:
Pour 1/8 inch layer of olive oil into a large skillet and heat over medium heat.  When oil is hot, drop in 2 tablespoon-sized mounds of couscous batter and flatten slightly (if they are too flat, they might start to come apart, but then you can make 'couscous cracklins' which are probably very good too!).  Cook until browned on bottoms, flip and brown top (we almost set off the fire alarm during this step!).  Repeat with remaining batter until used up.

To serve:
Toss each cake onto a small plate and top with a couple of tablespoons of the mushroom mixture.

My preferred way to eat them is to toss them onto a few napkins and squeeze the oil out of them before topping them with a handful of mushrooms.  This allows you to get the nice fried flavor with a little less fat, but it does somewhat deform the cakes!

I hope some of you reading this get a chance to try it!  Please let me know if you do!

- Brendan