Trip to Helsinki, Finland

Kaisaniemi Botanic Garden at Luomos, the Finnish Museum of Natural History

I've just returned from Helsinki! It's a beautiful city, even in wintry March, and I had a great time working with fern colleagues at the Finnish Museum of Natural History. Aino Juslén and Henry Väre were my hosts, and we have some big projects on Dryopteris, among other things, planned together. We had never met before, despite having co-authored a paper, so it was wonderful to spend a whole week with them. We poured over herbarium specimens they had received on loan from Kew, Berlin, and Stockholm, as well as Helsinki's own great collections, I gave a talk on reticulate evolution in ferns, and we ate some delicious food. I thought I'd share some photos reflecting most of these activities, as well as Helsinki itself.

The entrance to the herbarium

Beautiful wooden cabinets 

Carvings on each of the doors (not necessarily representative of the plants inside...)

Henry, Aino, and me

Sorry vegetarians, but there were lots of delicious sausages to be had...

A sunny day!

Main University of Helsinki building

Finnish Museum of Natural History

Finnish National Theater

Waterfront

Senate Square

Helsinki Cathedral

Statue of Alexander II, who established the Diet of Finland in 1863.

North American Dryopteris pubs

I'm thrilled to announce that a final version of the third chapter of my PhD thesis, which was published in provisional proof version months ago, has finally been posted on the journal's website, BMC Evolutionary Biology. If you're interested in reading about the evolutionary history of the fern genus Dryopteris in North America, you can find the paper here (or here's a direct link to the PDF). BMC is a collection of open-access journals, so you can download the paper for free. If you're really interested in Dryopteris and either feel like paying for articles or are associated with a university and have library access, you can find the papers corresponding to my chapters 1 and 2 online as well. You can also email me at sessa DOT emily AT gmail DOT com and I'll be happy to send you reprints (are they called that anymore if they're not actually printed out?). Here are links to the full set of what's published thus far:

• Phylogeny, divergence times, and historical biogeography of New World Dryopteris (Dryopteridaceae) (= ch. 1). Sessa, Zimmer, Givnish 2012 AJB 99(4): 730.
• Reticulate evolution on a global scale: A nuclear phylogeny for New World Dryopteris (Dryopteridaceae) (= ch. 2). Sessa, Zimmer, Givnish 2012 MPE 64(3): 563.
• Unraveling reticulate evolution in North American Dryopteris (Dryopteridaceae) (= ch. 3). Sessa, Zimmer, Givnish 2012 BMC Evol Biol 12: 104.

I'm proud of each of these papers for different reasons, but this third one is probably my favorite, because it tells the story that got me interested in Dryopteris in the first place. This group in North America has been suspected of having undergone reticulate evolution via allopolyploidy ever since botanists started looking at them over a hundred years ago, and many hypotheses have been suggested to explain the relationships among the 13 species on this continent (see Figure 1). 

The most widely accepted of these theories involves a missing, putatively extinct diploid ancestor of several of the allopolyploids, but no one had ever tested this using DNA sequence data. Figure 6 from the paper summarizes the results of my analyses, which unequivocally supported this hypothesis, known as the "D. semicristata" hypothesis after the missing ancestor.

I also included a figure showing the range maps of these taxa up above, because the final pieces of my PhD puzzle focus on transgressive trait expression and physiological ecology of these ferns. Hopefully you can see in the maps that several of the allopolyploids have ranges that are transgressive relative to one or both parents - meaning their ranges extend beyond those of their parents. This suggests that the polyploids, which are hybrids between those parental species that then underwent whole genome duplication, likely possess some physiological or morphological features that are distinct from the parents and that have allowed them to expand their ranges and coexist at a regional level with their progenitor species. The two final papers resulting from my PhD explore these ferns' physiology using field and common garden experiments. The first is in review right now, and the second awaits publication of the first. Stay tuned for more news about that in the coming months.

Dryopteris clintoniana

The final species I needed to measure on this trip was Dryopteris clintoniana; after D. ludoviciana it probably has the next-most-limited range of the North American Dryopteris, but happily it grows just a few miles from my beloved Ithaca, NY, so I never mind going out to visit this one. I've followed this population for several years and it's nice to find that it continues to remain stable at the edge of its little swamp. I did notice as I was measuring this year though, that there were a number of plants with, for lack of a better word, weird fronds.

Here's a plant displaying the horizontal, venetian blind-looking pinnae which this allohexaploid inherited from its maternal progenitor, the tetraploid D. cristata:

And a couple of odd looking individuals:

Dryopteris ludoviciana

Prior to this last field trip I had only seen Dryopteris ludoviciana in the field once, near Darlington, South Carolina, a couple of years ago, and a major goal of this trip was to find it and measure it. It is the Dryopteris species in North America with the most restricted range, occurring only in the extreme southeast, along the coasts. It is also one of only four diploids involved in the North American reticulate complex, and it is thought to be involved in the parentage, either directly or indirectly, of three of the five allopolyploids in North America. So it was a high priority indeed! Luckily we found a huge, beautiful population of these ferns at the Nature Conservancy's Rocky Hock Swamp Forest Preserve in Hertford, NC, with the help of Raleigh, NC fern enthusiast Jessie Perry. Getting to the plants was no easy feat, and involved a trek across a soybean field followed by hacking our way through a forest - my equipment is many-parted and cumbersome, so in the end I think we were just as glad to be done with these plants as we had been to find them in the first place! It was a great find, though, and I'll remember this population for years to come.

Dryopteris campyloptera

The first species I visited in the field on this last trip was Dryopteris campyloptera, which is a tetraploid hybrid between D. intermedia and D. expansa, and which grows at higher elevations in the eastern US. It actually has a disjunct distribution between the Great Smoky mountains and mountains farther north, like the Adirondacks. The southern population is likely a relict that retreated up into the mountains following the last ice ages in the northern hemisphere

I've visited this population before, and it grows in a hemlock dominated forest at Bear Pen Gap turnout on the Blue Ridge Parkway. One of the benefits of working along the Blue Ridge is being treated to views like this:

Another neat thing we saw, quite unexpectedly, was this.

What's neat about this, you ask? Look closer...

Greenhouse

First up in this travel diary of sorts, I have to share these photos of the fantastic greenhouse that Tom Goforth of Crowdog Native Ferns and Gardens set up to house the Dryopteris species used in this study. He built this structure, which has plants in three light levels that were achieved using shade cloth over the roof, and cared for all these plants over the course of the growing season. They had to be regularly watered, randomized and moved around within the treatments, etc. No small task, and I'll be eternally grateful to Tom for all his help with this project (and especially for killing the red wasps that had made a nest over some of the plants in the back of the greenhouse, and for moving two GIGANTIC writing spiders to quarters that wouldn't bring me into contact with them; I'm not a fan of spiders).

Late summer fern fieldwork

After returning from two weeks in Australia this summer, I had about a week's respite at home in Madison before heading out into the field in the US for my last field trip for the ecophysiological portion of my PhD. This three week trek started with a week in Pickens, South Carolina measuring seven Dryopteris species that have been grown and cared for in a greenhouse by my good friend and colleague Tom Goforth of Crowdog Native Ferns and Gardens. We also visited and measured a population of D. campyloptera in the Great Smoky Mountains. Then we drove east to Raleigh and Hertford, North Carolina, where we were led to populations of D. ludoviciana and D. celsa by fern fancier Jessie Perry. I then headed north toward western New York via Norfolk, Virginia, narrowly missing hurricane Irene in the process. In Hamilton and Ithaca I measured the final two species I needed for these studies, and celebrated the end of my PhD fieldwork with friends! The next few posts here will document this whirlwind journey and the plants I encountered along the way. Most will be well known to anyone familiar with this blog, but it's always fun to visit the same species, and in some cases, the same populations, again year after year; many of them have become like old friends to me after five years on this project.

* The photo up top is a hemispheric photograph taken with a special fisheye lens mounted on a regular camera. The photo is taken at about plant height, and can be used to measure the percent of the canopy that is open and affording access to sunlight for the plants; you can also get more sophisticated and use it to figure out the total amount of light a given location under the canopy will receive over the course of the growing season, given is elevation and lat/long. I have used these photos to quantify the light environments of my species, as light is the primary environmental variable whose potential influence on evolution I'm interested in quantifying.

Dryopteris expansa

My most exciting fern find so far this year has definitely been locating Dryopteris expansa in northern Wisconsin. This is the only species which I should have been able to find a field site for, but have failed at finding for the last couple of years. I've seen D. expansa out west, in Washington and Oregon, but I need a site within driving distance to make the types of measurements I need for my research. This species is well-documented in northern Wisconsin and Michigan, but somehow I was never able to track down any of those populations, or they were gone from the sites where they previously occurred. But now, finally, with the help of some very nice folks from the Chequamegon-Nicolet National Forest, I've got not one, but two field locations of D. expansa! I will probably only be returning to one to make measurements in the next few weeks, but it's nice to know that the other is there.

Like most Dryopteris, D. expansa is several times divided, and has a typical lacy, 'ferny' look to it. It's beautiful, needless to say. One stand-out character of this plant is the lowermost pair of pinnae, which are hugely triangular and expanded at the based (hence the species' specific epithet). The first innermost pinnule on the bottom (called basiscopic) is always the longest, as opposed to some other species of Dryopteris, where it is either always shortest, or varies considerably. The primary reason I was so anxious to find this species is that it is a diploid, and is one of two parents of a polyploid species called D. campyloptera. There are five sexual polyploid Dryopteris in the North American flora; of these, two have one parent that is unknown and probably extinct, leaving only three polyploids with both parents extant. Part of my work involves comparing the polyploids with their putative parents, and this is a very small sample size! So you can understand why finding this fern was so important to me - it was the only diploid parent of those three polyploids that was missing, so I now have the complete set for all three!

I'm measuring a number of characters related to light relations and photosynthesis for my research, and here's a shot of my photosynthesis equipment hard at work work on D. expansa:

Dryopteris goldiana at Abraham's Woods

I did a post about most of the ferns at Abe's Woods a few days ago, but I wanted to save Goldie's Woodfern, Dryopteris goldiana, for its own post. This species is close to my heart, since it's one of the (relatively) rarer members of the genus I study, and the population at Abe's Woods is really beautiful, and extensive. We saw it when we visited a couple of weeks ago, and the ferns were still unfurling, with many still in fiddlehead stage. I just went back to put out dataloggers, since I will be using this site for my research, and what a difference a few weeks makes! We've had a very strange, late spring here, and the temperature has gone from mostly in the 40s to mostly in the 90s over the last four weeks, and the ferns have responded in force.D. goldiana is one of the largest ferns we have in the woods around eastern North America (it could go toe-to-toe with Ostrich fern for that title), and it's remarkable to see how much they've grown and how quickly. Above and below are some 'before' shots...

And here are the 'after' shots. Quite a difference, huh?

These ferns are also showing off some helpful diagnostic characters. If you happen to come across an absolutely gigantic fern in the woods, and for some reason you're not totally convinced that it's Dryopteris goldiana just based on its massive-ness, here are a few things to look for. First, this species tends to have dense brown or golden-brown scales along the stipe (typical of the genus), but D. goldiana has a definite dark stripe down the middle of the scales, while many of the other Dryopteris I've come across in our area don't have this stripe. The arrangement of the sori is also pretty striking. They're very orderly, arranged in rows down either side of the costule of each pinnule, and have the typical Dryopteris form: a kidney-shaped, reniform indusium covering each sorus. Again, the only other really large fern you could confuse this with might be Ostrich fern, Matteuccia struthiopteris, but that one has totally dimorphic, separate sterile and fertile leaves, so should be easy to separate from this Dryopteris.

I included this last photo just to further impress you with the size of this critter, and I actually took a similar photo with Dryopteris celsa, the log fern, which is a polyploid between D. goldiana and D. ludoviciana. You can certainly see where D. celsa gets its size from!