Monday, 24 March 2014

Darwin's Pub.

[This is a duplicate of a post on my ecoevo-evoeco blog.]

Surely the greatest contribution that England has made to the world (apart from deep-fried Mars bars) is Charles Darwin. Certainly, then, the most important tourist destinations in England should be sites associated with Darwin. At least, that has always been my opinion. This post is about my failures and successes in attempting to visit Darwin’s haunts – and a few unexpected and uncommon discoveries along the way.

Would Chuck D have partaken?
On my first visit to London a number of years ago, I had half a day to spare and so sought out Darwin’s grave at Westminster Abbey. I showed up at the door, all aquiver with anticipation, only to be told that it was the one day of the year when tourists were not allowed – a special day instead for worship only. Damn. The next time I visited England, I had a whole day to spare (owing to that annoying policy of airlines charging almost double if you don’t stay over a Saturday night) and so I set my sights on a pilgrimage to Darwin’s home, Down House. Seeing his study and walking his Sandwalk, his “thinking path,” would surely be a great inspiration – and it must certainly be on the bucket list of every evolutionary biologist. After arriving in London on that trip, I looked Down House up on the internet and discovered that it was closed for renovations. Double damn. Instead, I visited the British Natural History Museum, where I could at least see the statue of Darwin. This statue figured prominently in a David Attenborough video for Darwin’s 200th birthday that explained how the statue of Richard Owen, who was instrumental in the museum’s history but a vocal critic of evolution, had recently been removed and replaced by this monument to his archrival Darwin.

Westminster Abbey
I visited London again last week, and I promised myself that I would visit both Darwin’s grave and his home. I even checked the opening times of Down House before booking my flight – Saturdays and Sundays only. So, on the Friday after our bioGENESIS meeting (see this post), I set out for Westminster Abbey. After waiting in line for nearly an hour, I finally made it inside. It was crowded and I was awash in hundreds of graves and monuments all over the floor and walls. Where was Darwin? The audio guide didn’t mention him – as I had been certain it would – so I had to ask. It turned out to be a plain white marble slab on the ground. I had expected something more dramatic, maybe with finch beaks engraved on it, but it was still fun to see the grave and compose pictures of it with the backdrop of an institution that – initially at least – felt so threatened by his ideas. After leaving Darwin’s grave, I tried to take a photo of the “grave of the unknown soldier” (definitely on the audio guide) and was promptly informed that photos were not allowed in the Abbey. Oops. I guess no one cares enough about Darwin’s grave to guard against photography. Even so, it was great to see the founder of evolutionary biology buried in the most important religious institution in England. (Writing this, I wonder if Bishop “Soapy Sam” Wilberforce is also in the church, perhaps with a perpetual frown in Darwin’s direction. Or maybe he is in some lesser church, with an even bigger frown.)

Westminster Abbey
The next day I was off for Down House, which proved to be quite a commute from the hotel, as befit Darwin’s desire to escape the city. I was even forced to wait about an hour for the bus from South Bromley to Downe Village (the “e” was added after Darwin’s time to distinguish it from another Down elsewhere). Fortunately, a Starbuck’s was right beside the bus stop, and so I could sip a non-fat no-whip hot chocolate (tastes the same the world over) and edit a paper. Eventually the bus came and about 20 minutes later we stopped at St. Mary’s Church in Downe. From there it was a 10 minute walk along a narrow lane between some fields and I had the great fun of seeing a pheasant prancing about – did Darwin shoot at its ancestors and miss? Down House was amazing, of course, particularly Darwin’s study and his thinking path, where I made a video to ask the pressing question: How did Darwin walk his sandwalk?

I could well have written an entire post about the wonders of Down House: Darwin loved billiards and would play every day with his butler, Darwin would leave his office dozens of times a day just to get a pinch of snuff from the hallway outside, Darwin rode horses until he fell and gave up, and so on. However, what happened after I left proved to be even more surprising and inspiring and so I will turn to that story.

Submitting a paper at Down House.
After about four hours at Down House, I walked back to the church in Downe to catch the bus. I had a few minutes to spare and so I walked around the church (and saw a plaque saying the sundial was in Darwin’s honor) and in the church (where written material explained how Darwin and his butler, Mr. Parslow, were an integral part of the community). As the bus was arriving, I saw a pub across the street from the church – the George & Dragon. Hmmm, I thought, how could I not have a drink in the bar in Darwin’s home town? So I let the bus go by, committing myself to at least an hour in Downe, and walked across the street to have a pint of Guinness. On my way there, I started to wonder. Could Darwin have gone to this pub? It looked quite old – perhaps he stopped in for a beer or two. Or maybe he spent the whole church service there after his beloved daughter Annie died and his faith was thus permanently shattered.

Emma’s church.
I entered the pub and was reinforced in my romantic hope as it looked really old, down to the low ceiling with rough-hewn and sagging support beams. But it still seemed a silly hope, so I started by asking the bartender some leading questions. “How old is Guinness?” – “Oh, hundreds of years.”  “Cool – and how old is this pub.” – “Oh, considerably older than Guinness.”  “Really,” I say, my excitement mounting. “Could Darwin have come in here for a pint.” – “Oh, yes, certainly. In fact, he stayed upstairs while visiting Downe and looking at the house.”  “Awesome. Perhaps he had a pint of Guinness here – just like I am doing.” – “Oh, that seems likely as he did some business here – see the photo and inscription on the wall.”

Darwin’s pub – the George and Dragon
Guinness in hand, I walk over to a framed document, which included a picture of the pub in the old days – originally called the George Inn – accompanied by an excerpt from the Bromley Record, July 1, 1867.

On Tuesday, 11th June, the Downe Friendly Benefit Society held their 17th anniversary at the GEORGE INN where a most excellent dinner was provided by Mr. and Mrs. Uzzell. The chair was taken by Mr. Snow and the vice-chair by Mr. Parslow. After the cloth was removed and the usual loyal toasts and healths of the treasurer C. R. Darwin Esquire and others, had been given …

Be still my beating heart.

Over the next few hours, I sat in a big comfy chair beside a fireplace that might have warmed Darwin (but not me, owing to fire regulations) and drank several pints while bus after bus went by without me. I edited a paper about the evolution of resistance to parasites. I edited the video asking How did Darwin walk his sandwalk? And I generally absorbed the ambiance and reveled in the thought that I might be sitting in the place where Darwin first scribbled his “I think” diagram – perhaps on a bar napkin.

Darwin’s thinking chair?
OK, I realize I am being overly romantic here. Guinness was probably not on tap in 1860. And, if it was, it was probably not available in the George Inn. And, if it was, Darwin’s delicate stomach probably made him gravitate toward easier fare. And bar napkins probably didn’t exist. And, if they did, Darwin probably didn’t bring his quill to the bar. And, if he did, he probably wasn’t thinking about evolution while drinking. And, of course, he probably scribbled his I think diagram somewhere else (indeed, he did so before buying Down House). But the experience was nevertheless inspiring and the scenario at least plausible in that Darwin might have had some eureka moments in the same physical location I was occupying. Certainly, most of my good ideas have come in bars over a pint of beer or a glass of whisky – at least most of my good blog ideas anyway.

Or maybe Darwin would have preferred this sherry - photo by Mike Hendry
So, the next time you’re in England, by all means visit Darwin’s grave and Down House. Marvel at his writing chair. Be inspired on the sandwalk. But – most of all – don’t forget to visit Darwin’s pub. Bring your computer – do some science. Darwin would want you to.

Monday, 24 February 2014

Evolution coming undone in Galapagos: human impacts on Darwin's finches

[This is a duplicate of a post on my eco-evo evo-eco blog.]

I just returned from a short trip (my tenth) to Galapagos. New experiences during the trip prompted further speculations on a phenomenon we had earlier described: human influences on the adaptive radiation of Darwin’s finches.

An oft-repeated mantra is that remote oceanic islands (never connected to the mainland) are natural laboratories for studying evolution. Part of the reason is that they tend to be simple environments, making it easier to disentangle otherwise overly-complicated ecological and evolutionary relationships. One way in which islands are simple is that they often lack human populations, which contributed to the evolution of strange forms that proved to be utterly unsuited for a life with colonizing humans. As a result, the settlement of remote islands by humans often leads to the extinction of local life forms. However, not all isolated populations go extinct when humans colonize, instead they often evolve to suit the new conditions. 

A spectacular male Darwin's finch.
My own foray into island life involves Darwin’s finches in Galapagos. This work obviously follows closely from the insights and work of Peter and Rosemary Grant, and was made possible by an impromptu postdoc I did with Jeff Podos at UMass Amherst. In general, the adaptive radiation of Darwin’s finches is thought to have been driven by specialization of different species on different food types, which has led to reproductive isolation (speciation) through assortative mating by beak size (beaks, songs, and mate preferences are all linked) and natural selection against hybrids (which are poorly suited for either parental diet). With respect to this last point, different “adaptive peaks” are thought to exist in the Galapagos as a result of different food types. For example, large-beaked species evolve to use large/hard seeds and small-beaked species evolve to use small/soft seeds but intermediate beak sizes are rare because intermediate seeds are rare. (I just made and posted a video illustrating this phenomenon.) Darwin’s finches thus diverge onto different adaptive peaks and the few hybrids they produce have intermediate beaks that lack appropriate intermediate seeds on which to feed, and therefore suffer low survival – thus keeping the two species separate.

Yum - a native food!

Our contribution to this story has been the study of two beak size morphs within a single species (the medium ground finch, Geospiza fortis) on the island of Santa Cruz. We (originally Jeff Podos, Sarah Huber, Luis De Leon, Antony Herrell, and myself) have shown that these large and small G. fortis morphs at one site (El Garrapatero) have a bimodal beak size distribution (many large and many small individuals with relatively few intermediates), have different diets, manifest different feeding performances (bite force), sing different songs, show different responses to songs, mate assortatively (large females with large males and small females with small males), experience disruptive selection (intermediate birds have lower survival), and show limited gene flow (based on microsatellite DNA). Stated plainly, these two morphs seem to be part of the way to becoming separate species, presumably through the same mechanisms as those that drove the radiation as whole.

The two El Garrapatero G. fortis morphs.

All of the above effects were demonstrated at a site (El Garrapatero) that is removed from any human settlements and therefore experiences little direct human influence (although indirect influences from introduced species are present). What happens when these two morphs – on their way to potentially become separate species – contact a growing human population? We were able to explore this question in a paper published in PRSB in 2006 by obtaining long term records (1964-2005) of G. fortis beak sizes from Academy Bay, a site immediately adjacent to the rapidly growing town of Puerto Ayora on Santa Cruz Island. This analysis was made possible through data collected by David Snow in 1963-1964, Hugh Ford in 1968 (data was being collected for me as I was being born!!!), the Grants and their colleagues (1970s-1980s), and our own samples (2004 and onward). Analysis of these data showed that the beak size bimodality currently seen in G. fortis at El Garrapatero was also present at Academy Bay in the 1960s but not thereafter. The two morphs at Academy Bay thus seemed to have fused together into a single hyper-variable population in concert with the dramatic increase in human population density at that site.

That is not a native food!

We proposed in the 2006 paper that fusion of the two G. fortis morphs at Academy Bay was the result of humans introducing food types that were accessible by finches of all beak sizes, thus turning the separate adaptive peaks into a long adaptive ridge spanning different beak sizes. On such a ridge, selection against intermediate birds should disappear and their increasing abundance should eliminate the bimodality. We provided support for this hypothesis in a paper in Evolution in 2011 that showed how the naturally strong (confirmed at El Garrapatero) associations between diets, beak sizes, bite forces, and gene flow that presumably drive finch diversification had all become weaker at Academy Bay. In short, humans were causing “reverse speciation” or “despeciation” by turning a formerly rugged adaptive landscape with distinct fitness peaks into a broad ridge without the gaps (fitness valleys) necessary to maintain species distinctiveness.

Our 2011 paper.
This finding was where we left the story until recently. This year, we (spurred mainly by Luis) took up the problem again by making more extensive surveys in the town of Puerto Ayora to see how many finches were using human resources. Various teams of researchers and Earth Watch volunteers would walk through town in the mornings counting birds and determining what they were feeding on. Although I was already suspect the outcome, I was still rather shocked by how many finches were present in the town (more than in nature) and their incredible use of human foods – although they still found natural foods in vacant lots and gardens. I saw finches eating waffles, chips, plantains, rice, corn, fruit, ice cream cones, and many other items. I thereby gained a personal confirmation of our original intuition that finches in Puerto Ayora (Academy Bay) had access to many food types that were usable by finches of any beak size. Then came the real kicker – at El Garrapatero.

Dozens of finches of many species eating rice.

We have been work at El Garrapatero for 12 years now. During that time, the site has transitioned from a difficult-to-access and rarely used site to a very popular destination for locals and tourists. The road has been paved and extended closer to the beach, the path to the beach has been cobbled, buses and taxis roar up and down the road, and gaggles of kids and adults play on the beach. My first hint of possible impacts was the appearance of non-native fruits (passion fruit) along the roadside. I was willing to accept that this would not have a major influence on finch evolution until recently. In 2012, we filmed Galapagos 3D IMAX – narrated by David Attenborough (no I didn’t meet him – but it was cool to hear him say my name on air) – at El Garrapatero. The film crew felt that our normal site, which was away from the beach, was not very picturesque – so they asked us to set up our nets at the beach itself. I was initially skeptical because we had never netted therefore and I couldn’t be sure we could get finches. However, we quickly caught lots of finches – they even seemed more abundant than at our normal site several hundred meters inland. And they seemed attracted to us. At one point, we were waiting to film something and noticed about 20 finches that landed right beside our banding station. We pointed this out to the film crew and they quickly swung their camera boom to film the finches at close range – this became the scene that opens the finch sequence in the film. We also saw several finches attacking the food we had brought for lunch. I was intrigued by this from a filming perspective but didn’t dwell on it much from the perspective of evolution. This year, however, my opinion changed.

Team Pinzones IMAX 3D (Photo by Aspen Hendry)

A few days ago, we walked with the Earth Watch volunteers down to the beach and came across a place where finches were everywhere. We sat down and they swarmed us. Jeff would crinkle a chip bag and they would come running. Then Luis would do the same in a different place and they would run over to him, jumping up on his bag and even into his hand in hopes of getting free handouts. Nearby, other finches of several species were fighting over some plantains someone had left out. It seems that the beach is now an accepted place to feed the finches. This got me to thinking that the direct human influence at El Garrapatero is increasing dramatically and that we might – in the near future – see impacts on the finch bimodality. In particular, we documented disruptive selection (selection against intermediate beak sized birds) in 2004-2006 before all these human changes were so dramatic. My prediction is that selection now will be less disruptive– and perhaps even less so in the future as human use of the site continues to expand.

An El Garrapatero G. fortis enjoys a cracker - when it shouldn't. 
Evolution is coming undone in Galapagos. Human influences are pervasive in some places and they are expanding to new places. This is exciting as a scientist because we can now test evolutionary hypotheses using whole-ecosystem “experiments” – we can add humans and see how evolution changes. But it is depressing as a nature lover because a unique set of island life might well change dramatically. Finches will still be present, of course, but they might no longer be so diverse – at least not in sites where human influences are strong. Fortunately the government limits those impacts to restricted sites, leaving much of the archipelago free of direct human impacts (indirect effects can remain strong). This policy is reassuring because it would be a travesty if unique forms such as the “vampire finch” on Wolf Island were to disappear.

I will report back in another decade or so.

We were even besieged by finches during our breakfast (and they ate our chocolate bread, damn it).


Thanks to our 2014 team so far: Diana Sharpe, Jaime Chaves, Kiyoko Gotanda, Joost Raeymaekers, Luis De Leon, Sofia Carvajal, Jeff Podos, and 16 Earth Watch volunteers.

Pictures and videos: 

  • Galapagos 2014 images on FLICKR
  • All my past Galapagos images on FLICKR

Related posts: 
    • Kiyoko's blog from this year's Earth Watch expedition.

    Some earlier Galapagos posts on this blog:

    Human influences on sea lion evolution?

    Tuesday, 17 September 2013

    From Ridge to Reef: Conservation and education opportunities in Belize! Presentation at 11:30 on Friday Sept. 20th in Redpath

    As a former NEO student I am really excited to announce the possibility of a collaboration between the NEO program and a tropical field station my partner and I have built in the Maya Mountains of Belize.

    Our field station, called the T.R.E.E.S Hosting Center, has been operating since March 2013. Our facilities are set on 200 acres of Lowland Broadleaf Forest at about 200 m elevation. Most of this forest is primary growth and as it is in the foothills of the mountains there is a lot of precipitation that creates a dense rainforest. We have over a km of river (Dry Creek) that runs through our site as well as numerous tributaries. Finally, some secondary growth forest, grassland habitat, and an organic fruit orchard provide a variety of habitats and hence a very high diversity of flora and fauna species. Our site is adjacent to the Sibun Forest Reserve which together with several other reserves forms the Southern block of protected areas in Belize, consisting of thousands of hectares of intact contiguous tropical forest. We have kms of trails running throughout the site and in the making is a 4-day hiking trail that goes up into the Sibun Forest Reserve in the mountains (at about 1000 m elevation).
    T.R.E.E.S cabins and Maya mountains
    Dry Creek that runs through T.R.E.E.S 
    Our remote cameras have shown dozens of different large mammal species present on our site, including jaguar, margay, tayra, armadillos, agoutis, brocket deer, pacas, and skunks. Live trapping of small mammals and mist-netting of bats have added several species of small mammals, including several individual mouse opossums. At least 9 fish species have been identified in the river systems, more than 40 species of reptiles and amphibians have been observed on site to date (including many endemic and endangered species), and our bird list now numbers over 150 species.
    Map of Belize (star is T.R.E.E.S)

    Freshwater fish from Dry Creek

    Mouse possum
    Jaguar on field cam

    Blue-spotted Treefrog (Endangered)
    Royal Flycatcher
    White Hawk

    We can host groups of up to 30 students with accompanying professors for faculty-led field courses but we also offer our facilities to undergraduate students interested in internships or volunteer work, or graduate students pursuing studies in tropical ecology. That is where the NEO program comes in!
    To graduate students we offer field equipment for stream sampling (including minnow traps, D-frame kick nets), mist-netting of birds and bats, and small mammal trapping. Starting March 2014 we will setting up a bird-banding station that will run as a long-term monitoring site for migratory and resident bird species. Long-term herp monitoring projects for frogs and turtles is also underway.

    Bird bag Christmas Tree

    Belize, although not officially Spanish-speaking, is a country in Latin America and as such is an excellent location for NEO students to conduct graduate studies in ecology, community development, political science, and resource management. We work with professors from the University of Belize and Galen University that can act as co-supervisors for students in NEO. My partner and I (both biologists) are also at the T.R.E.E.S field station the better part of the year to help students on projects.

     If you or anyone you know might be interested in conducting research based out of T.R.E.E.S in Belize and would like more information, I invite you to see our talk at the Redpath Museum at 11:30 am this coming Friday, September 20th. You can also check out our website at or email me directly at

    I am looking forward to being part of the NEO program again!

    Vanessa Kilburn
    Director and Program Manager,
    T.R.E.E.S (Toucan Ridge Ecology and Education Society) 

    NEO graduate 2008 (Herpetology)
    Supervisor Dr. David M. Green

    Friday, 6 September 2013

    Food or Poison

    “Often there is not even a thin line between a food plant, a toxic plant and a medicine”
    Marjorie Grant Whiting, 1962

    Its all a matter of dosage” they say.

    Lets take an example from a common medicinal compound, like codeine. Codeine is one of the opioid alkaloids produced by the poppy plant and can be detected in the human blood after eating a poppy seed bagel. Its magical powers (activating opioid receptors) justify the extensive use of codeine as a painkiller, analgesic, antidepressive, sedative and cough relieve. However at very high doses codeine will kill you by respiratory depression. The importance of dosage can be observed in many relationships between humans and plants. While the dosage issue might come off as common knowledge for many, we drinkers like our plant brews and distillates in the rage of 4 – 40 % alcohol, the parallels to other plant-animal interactions might not be so obvious.

    After studying a beetle that loves cycad toxins, we might have found parallels to the human relationship to medicinal/drug plants. The beetles seek out the cycad plant when the new foliage is being produced and voraciously feed and mate on the plant. They actually sequester the cycads toxins as means of defense and upon threat they will expose a drop of hemolymph from the leg-joints. The tiny drop of hemolymph contains high concentrations of the plant toxins. This surely shows that the beetle is a cycad specialist and can deal with the plant’s toxicity. But when we looked at the relationship a bit closer we found that the insect does not feed on the leaves with highest concentrations of toxins as we predicted. They rather choose a lower range of dosage from which they take their fix. Our data suggest that the high concentrations are still protecting the youngest leaves even from these cycad-loving beetles. Just as in the human-plant interactions, the beetle benefits from a particular chemical compound present in the plant but only at a certain dosage.

    The dosage dependent manner of plant-animal relationships is probably based on the enzymatic capacity of the animal in question. Intoxication arises from saturation of the detox capacity of the herbivore.

    So why doesn't the plant produce more of these toxins if they are so effective? Well, no one really knows, but it could be due to the cost of production or a matter of autotoxicity. The plant cells are also vulnerable to the deleterious effects of these toxins if they are not properly controlled.
    And why doesn't the insect increase its enzymatic capacity to be able to feed on the most toxic leaves? Maybe there is no need, we have not observed any predator feasting on these aposematic beetles despite their local abundance.
    Plants produce a plethora of secondary metabolites many with the ability to deter herbivores and pathogens. Sometimes the same compounds that effectively deter one set of organisms will be mediating the interactions with others. How do these plant-insect relationships arise? Why are some insect groups more prone to tolerating a specific type of plant chemistry?
    So many questions to explore, so many lessons to be learned.    

    Photo credits: Don Windsor and Guillaume Dury.

    Monday, 29 July 2013

    Impossible realities: adaptive radiations and the suspension of disbelief

    [This post also appears on my other blog:]

    Adaptive radiations occur when a single ancestral species radiates into multiple descendent species as a result of adaptation to different environments or resources. Adaptive radiations provide perhaps the clearest evidence for the role of adaptation in shaping the diversity of life – think Darwin’s finches in Galapagos, Anolis lizards in the Carribean, figs and fig wasps, Hawaiian silverswords, and so on. The typical assumption of this model of evolution is that a number of empty “niches” exist and that organisms evolve and speciate to fill them, after which the radiation ceases. However, a number of alternative possibilities exist, such as the evolution of one species creating a brand new niche that favors the evolution of still more species – diversity begets diversity.

    These possibilities have been explored using a variety of methods. One method is to try to figure out how many possible niches are out there – and how many of them are filled. That is, do the 13 or so species of Darwin’s finch correspond to the 13 different resources to which finches can possible adapt? Stated another way, is the fact that marine finches and cave finches don’t exist mean that these niches are not accessible to finches or that finches simply haven’t gotten there yet? 

    Questions along these lines are often explored by investigators attempting to guesstimate what niches are possible for a given taxonomic group, thus enabling estimates of which niches have and have not been filled by a given adaptive radiation.  But how does one establish the range of possibilities? That is, how does one determine whether a hypothetical niche (marine finches) is or is not possible (i.e., accessible to the adaptive radiation)? A common route to this determination is to estimate the range of biomechanically possible morphologies and then determine how much of this range is filled by extant organisms. Unfilled morphospace then means the radiation hasn’t yet been completed – empty niches are still in waiting.

    Sometimes I fear that these endeavors are doomed to failure – because it is usually impossible for us to determine what realistic empty niches are out there but have not yet been filled. This opinion first crystallized for me on my first trip to Africa and was brought back to mind by this week’s trip to sample guppies in Trinidad. The key realization for me was that many organisms that currently exist would probably not have been considered possible if they hadn’t already existed. The most obvious examples of these impossible realities are situations where one or a few species are highly divergent in morphology from other organisms – with giraffes first bringing the point home to me. Giraffes are so different from other organisms that I would bet that we would never imagine they could exist if they didn’t already. Ditto for hippos and bombadier beetles and aye-ayes and emperor penguins and mudskippers and cookie-cutter sharks and gastric brooding frogs and hydrothermal vent organisms and so on. In other cases, it is a whole group that is so bizarre that we wouldn’t believe them without the proof staring us in the face. Perhaps most striking, no one imagined dinosaurs – at least not in the depth and breadth of their majesty – before they had been revealed by fossils.  And I would place deep sea angler fishes in a similar place. These bizarre creatures suggest to me that many other morphologies, presumably suited for very divergent niches, still exist out there and have not been filled.

    Beth and Felipe catching guppies.

    The reason my trip to Trinidad brought this point back to mind was that a species exists there that is so bizarre as to challenge credulity, except of course for the fact that it actually exists. Imagine a bird that lives in caves (some other birds – cave swiftlets – also do so), feeds at night (some other birds – nightjars – also do so), has chicks that can be melted down to make oil, and echolocates (….). Yes, indeed, they echolocate. They use a series of clicks and screeches to help them navigate in pitch darkness both inside and outside of their caves. Bats do it, but birds? Bizarre. Unprecedented. Impossible? I had long heard about oilbirds and had even seen (mostly heard) them fly by while camping at night in remote rivers of the northern range of Trinidad – but never before in 13 years of visiting Trinidad had I seen them in their caves. But this was finally that year, with Felipe Perez leading me on a 2.5 hour hike up into the mountains to one of their (few) caves.

    From my field notes: We reached the cave well after dark and were coaxed along the last few hundred meters by an ever growing crescendo of loud clicks and screeches. We wormed our way down a tiny creek in a small canyon and into a boulder field that descended into the mouth of the cave. The cave was quite large and extremely noisy and a bit smelly and wet, with water dripping from the cave roof. It was not a horizontal cave like you see in the movies but rather seemed to go about 45 degrees down and into the depths – presumably having been wrought by the creek flow over eons. Along the walls of the cave were ledges that were full of screaming oilbirds. [Wikipedia notes: In Trinidad it was sometimes called diablotin (French for "little devil"), presumably referring to its loud cries, which have been likened to those of tortured men.] They would either sit there and hurl imprecations or fly back and forth in and out of the cave opening or around inside the cave. It was quite spectacular and I wasted no time in getting out the camera. The photography conditions were quite difficult, however, as it was pitch black and the oilbirds were mostly far away – so Felipe would hold both headlamps pointing at a bird and I would use a telephoto with a big flash, which – after much trial and error – took some decent photos.

    Echolocating oilbird.

    Although oilbirds were the main reason I was reminded of the difficulty of identifying the possible in evolution – and although they fit the illustrative point of a specific bizarre species very different from all their relatives – I can’t help but also mention a very different scenario that tells the same story on a much grander scale. That is, an entire group that seems familiar to us only because of their existence – snakes. By this I mean that – if snakes didn’t exist – we might be hard pressed to imagine their existence, although some legless lizards get pretty close. But, in reality, I am particular motivated to mention snakes – and to think about their strangeness – because of a recent encounter in Trinidad.
    Fer-de-lance: the snake we most commonly encounter in Trinidad.

    From my field notes: I was processing fish at the table in Simla (the William Beebe Tropical Research Station) and had just finished a tank of fish. I picked up the tank to take it and empty it outside and was walking out the door when “thump” something heavy fell in the area between the open door and the door jamb. I looked quickly and saw it was a very big snake. Thankfully, I also instantly saw that it wasn’t a poisonous one – or at least not a poisonous one I was familiar with – so I just kind of backed off and called Felipe and Beth to come have a look. During this time, the snake, which turned out to be Pseustus sulphureus sulphureus, was slowly working its way up the door jam and higher toward the rafters of Simla. Felipe quite correctly pointed out that it would be good to not let it get too high above our reach or we would never get it – so I ran and got some butterfly nets to catch it. Felipe then engaged in a protracted dance with the snake to try to catch him in the nets, which he eventually did. I kibitzed and took photos and videos. After taking it outside, we let it go and it sort of hung around in some bushes nearby. We were confident its traumatic capture, handling, and release would convince it to depart.
    Knock knock
    Getting higher
    Pest removal by Felipe.
    Now that's a big snake (Pseustus sulphureus sulphureus)
    About 15 minutes later, I was sitting having lunch on a couch facing the open door when, what should I see but the snake slowly slithering back inside the door. This time it was my turn to take a stick and pick the snake up and deposit it farther away from the house. But, by this time, I was starting to think that maybe it really wanted to be in the house and that it would not be deterred. Sure enough, about 15 minutes later, Felipe found it right beside the house again. This time, we moved it into the trees a bit away from the house, just the sort of habitat where it should like to be. It stayed there initially but I was getting more confident that it would be back – so I kept an eye on it. In fact, I went and got my camera to take some more photos – this time in its more natural environment. By the time I got back outside, I could see that it was starting to move out of the trees again toward the house. So I started filming.

    As it got closer and closer, it changed direction and was heading right for me. Hmmm, this will be a good video, I thought. Then it came out of the tree not two feet in front of me – heading straight for me. A good video indeed! In fact, I could see that it was still heading toward the house, which was behind me, and the most direct route from where it was to the house was directly between my legs. I kept filming and, sure enough, it kept going right through my legs and toward the house. I eventually stopped filming because I could see it was about to enter the house through a small hole, so I grabbed its tail and it instantly whipped around and struck at me. Being at about waist height on some steps at that point, it definitely raised my adrenalin level. 
    You lookin' at me punk?

    By this point, I was really enjoying the snake but also finding it quite distracting – I had fish to process after all. So at the end of this third encounter, I collected it with a pole and dropped it off a rather steep – if short – cliff lined with ivy. Although it clearly wouldn’t be injured, I figured it would at least get the idea that it might get injured if it stayed. It wasn’t that I was afraid of the snake or didn’t like it – quite the contrary – I just figured that it would be very distracting if we were having to keep our eyes open all the time while we were in the house for fear of stepping or sitting on it. Remember sitting on your house cat by accident, well this would take it to the next level.
    Pseustus sulphureus sulphureus

    After this most recent encounter, I went back to work processing guppies, but I kept looking behind me toward the door and windows because I was still thinking it might be back. Sure enough, about 15 minutes later, I could see it climbing the outside of the house and then entering the house along the edge of the vaulted rafters about 3.5 m up. Then it proceeded to move along this edge. Well, I thought, we can’t have it moving up into the attic or down into our rooms – that would take the distraction to a whole new level, so I set out to corral it in the same way Felipe had done previously. But now it was about a meter higher than before, so I had to stand on a desk or table and reach way above my head with the nets trying to get the snake into the net. This I could sort of do – but only the first half of the snake – try as I might I couldn’t pry the other half off the edge – and it became rather exciting when it would turn around and coil up as if to strike – while being 1 m above my head looking down at me.
    As I didn’t succeed in capturing it, it turned around and went the other direction until it got to a new place where I could take another whack at it. Back and forth and back and forth we went in some bizarre pas de deux. Each time I tried to catch it, it would turn around and head the other direction. I would then sit down to process a few fish and, then, when it finally reached somewhere new where I could get at it, I would rush over, jump on the table (or desk) and try to corral it again. It eventually seemed to tire of this game and worked its way out of the house and onto the roof. That was it for that day but I suspect that the next visitor to Simla will have a similar adventure.

    Another Trinidad oddity - the endemic Mannophryne trinitatis and his tadpoles.

    So, from snakes to oilbirds to dinosaurs to hippos to giraffes, it seems to me that the human imagination and even calculation is incapable of postulating the possible endpoints in an adaptive radiation. We either circumscribe the possible morphospace much more than the actual reality, or we postulate things that really aren’t possible no matter what.  I am not sure where this leaves the study of adaptive radiation except perhaps to the idea that the best judge of what is possible is what already exists, with the caveat that this is almost surely an underestimate of what is actually possible. Adaptive radiations are indeed stranger than fiction.
    Here are some more pictures from the Trinidad trip:
    Here is my Trinidad post from last year:

    Tuesday, 2 July 2013

    NEO Symposium Abstracts


    Galaxias eclipsed by aliens

    Abstract: In the realm of galaxiid fishes (Galaxiidae) in cold-temperate freshwaters of the Southern Hemisphere, understanding the ecological impacts of invasive salmonids (Salmonidae), especially brown trout and rainbow trout, is a priority to develop conservation guidelines and learn about the diversity and function of natural ecosystems. Galaxiids are considered amongst the most seriously threatened fishes known presumably due to trout invasions, but data is often qualitative and ambiguous. Furthermore, little is known about the extent to which native ecosystems have been transformed, especially in lakes. The goal of my PhD thesis was to fill some of these knowledge gaps by investigating Patagonian lakes. The results showed a strong effect of trout on the decline of Galaxias platei, as well as a natural constraint to trout invasions (impacts) that results in valuable yet insufficient ecological refugia. At the individual level, trout and G. platei affected each other’s trophic niche asymmetrically—trout escalated whereas G. platei sank in the trophic chain, a perspective rarely studied. Finally, the invasion created a natural experiment suitable to demonstrate a strong negative top-down control on zooplankton elicited solely by G. platei. By contrast, trout, by reducing the abundance of galaxiids, had a strong positive top-down control on zooplankton. This talk will be spiced up with footnote slides addressing additional issues related to methodologies, conservation, management, and environmental policy, in an attempt to showcase the diversity of perspectives and approaches that NEO students are prone to navigate.


    On sex and the evolution of parasite resistance: does sexual dimorphism prevent parallel evolution?

    Abstract: Populations that are spatially segregated often experience different selective environments, which cause the adaptive divergence of traits that influence survival and reproduction. When this occurs in a similar fashion for multiple independent population pairs, the outcome is called “parallel” evolution. Recently, increasing emphasis has been placed on the fact that populations in similar environments often differ substantially in adaptive traits, suggesting an element of “non-parallel” evolution. Similar questions surround adaptation by the two sexes to divergent environments. Parasites are an important selective agent known to cause adaptive divergence between populations; how host resistance (the ability to reduce or control parasite numbers) evolves is a key issue in multiple fields. We explore whether males and females in the same population respond differently to a similar shift in parasite pressure. On the one hand, parasites often have similar effects on males and females and the genes that influence resistance to specific parasites are often found on autosomes, suggesting that a shift in parasite pressure might lead to parallel (or symmetric) evolution of the sexes. On the other hand, males and females often experience different parasite levels, have different costs of infection and different costs of defence. We tested guppies (Poecilia reticulata) that were released from selection by a key parasite (Gyrodactylus spp.) in four replicate translocations in the wild. After four and eight generations, guppies from the translocated populations, and from the source population which remained exposed to Gyrodactylus, were sampled and bred to second generation under common garden. We exposed these descendants to individual infections with G. turnbulli and monitored parasite numbers on isolated guppies over a period of 24 days. The release of wild fish from Gyrodactylus led to asymmetric (non-parallel) evolution of resistance in the sexes: females derived from three of four translocated populations showed increased resistance relative to the source population, whereas males showed no change.


    Supervisors: Mark Torchin (STRI) and Andrew Hendry (McGill)

    Infection preference and host specificity of an invasive parasite to novel invasive hosts in the Panama Canal: natural experiments in ecology and evolution of adaptive specialization in a human-dominated invaded landscape.

    Abstract: Host range, or the breadth of species that a parasite or pathogen can infect, is an important life-history trait that determines the ecological impact of a parasite and elucidates evolutionary trajectories of biotic interactions. Trematode parasites have complex life cycles with varying degrees of host-specificity, such that they are less specific to second intermediate hosts than they are to first intermediate snail hosts. Here, we investigate the extent to which exotic parasites interact with an assemblage of invasive species in order to understand the role of biological invasions in facilitating the transmission of these parasites through ecological and evolutionary processes. Specifically, we investigate how a globally widespread and economically important invasive parasite, Centrocestus formosanus, interacts with an assemblage of invasive snails with which it does and does not share a common evolutionary history. We also investigate how it interacts with a novel community of native cichlid fish in the Panama Canal that can serve as potential second intermediate hosts. We report that in natural assays of prevalence and in preference experiments in the laboratory, infection of Cichla ocellaris was significantly higher than other co-occurring cichlids. Single species experiments also demonstrate a higher infection rate for this fish than other available hosts. We speculate that the observed preference of C. formosanus on C. ocellaris, a popular sport-fish, demonstrates local adaptation to an invasive host in the Panama Canal. Infection preference for novel invasive hosts can thus have significant consequences for the transmission and evolution of emerging parasitic diseases. We hope to continue this research by evaluating patterns of host preference and parallel local adaptation to invasive and aqua-cultured fish species in other parts of the world in understand the processes that drive rapid local adaptation of infectious agents in invaded, human dominated landscapes.


    Supervisor: Sylvie DE BLOIS1, and Gerardo CEBALLOS2
    1  Plant Science and School of Environment, McGill University. Montreal, H9X 3V9 Canada
    2 Ecology Institute, National Autonomous University of Mexico. Mexico city, 70-275 Mexico

    Bridging the gap for large cats: connecting the dots for ecological corridors of a complex habitat for the jaguar in Mexico.

    Abstract: Current trends in biodiversity conservation are based on maintaining suitable habitat conditions not just within protected areas, but also on adjacent, sustainably managed lands. This is especially challenging for the conservation of large carnivores such as the jaguar that require connected habitats to minimize extinction risks and facilitate movement while minimizing conflicts with humans. This study provides spatially explicit habitat information for jaguar management and the implementation of corridors linking its populations in the Yucatan peninsula, Mexico, an area of international significance for the species. First, habitat suitability models based on jaguar occurrence records and a combination of land use and land cover (LULC), distance to infrastructures (human settlements and roads), and climate (mean annual precipitation) were constructed using MaxEnt. Then, this information was used to derive a cost surface for mapping suitable corridors, linking four locations (nodes) where current jaguar observations were concentrated. Five potential corridors of varying quality have been identified between the population nodes in the biosphere reserves in the peninsula, the best one being from south to northeast along the Caribbean coast. The corridor connecting northern locations from west to east had the poorest habitat conditions. The suitable habitat models and corridors support the potential value for conservation of productive lands under sustainable forest management since most potential suitable habitats for jaguars were found outside protected areas. These results can be useful to highlight areas of potential opportunities or conflicts for jaguar conservation in a human-dominated landscape and to target areas for further jaguar surveys.


    Remittance Cultivated Landscapes: Land use change, forest recovery, farming decline, and new trends in a Zapotec town of the Sierra Norte of Oaxaca, Mexico

    Abstract: In indigenous towns, high levels of emigration have led to rapid shifts in economy and landscape. Such is the case of Yalálag, a Zapotec town in the Sierra Norte of Oaxaca, Mexico. Many Yalatecans have observed transformations in landscape composition over the past three decades due to a dramatic decline in farming activity. In this presentation, I show how land-use change is related to emigration but also to broader economic changes and state-policies. As a result, there have been intentional changes to social organization and norms around the use of natural resources that, on the one hand, has led to increased forest conservation but, on the other, has led to conflict with settlements on the periphery of the town’s borders. Moreover, I show how land-use change has caused a dependency on external food sources and affected the Yalatecan diet. Thus my presentation will aim to link the ecological, social, and cultural dimensions of transformations in Yalálag’s landscape.


    Title: Leaf traits and specialist herbivores on Zamia elegantissima (Zamiaceae)

    Abstract: Neotropical cycads protect their leaves against insect herbivores with different chemical and mechanical barriers. Specialist herbivores have means to cope with these defenses; however, the extent that leaf traits limit the activity of these well-adapted specialist insects is unknown. In this study, we have investigated the incidence of specialist herbivores and changes in leaf traits of the Panamanian cycad Zamia elegantissima. Herbivore incidence and leaf traits related to herbivory, such as leaf age, lamina thickness, resistance to fracture, work to fracture, chlorophyll content, water content, trichome density, and toxic azoxyglycoside (AZG) content were measured throughout leaf development. Principal Component Analysis of leaf traits identified characteristics that may explain specialist herbivore incidence. Z. elegantissima leaf development is characterized by quick leaf expansion and delayed greening. Young leaves are protected by trichomes and AZGs, but these defenses rapidly decrease as leaves expand. Decreases in AZGs are correlated to increases in lamina thickness and leaf toughness. Specialist herbivores feed on leaves for a discrete window of time (10 to 100 days after leaf flush) and consume 36% of total leaf production. AZG levels between 5–200 mM/g are correlated with herbivore incidence, however, at extreme levels (>500 mM/g) herbivory was absent. Herbivory by specialist is constrained during leaf development; young leaves are chemically protected and older leaves are physically protected. Our results support the hypothesis that chemical defenses still limit the activity of specialist insects. However, as leaves age, AZG levels decrease and toughness becomes a primary mechanism to deter herbivores.


    Latitudinal Gradients in the Parasitism of the Invasive Lionfish (Pterois volitans) in the Caribbean

    Abstract: The biotic resistance hypothesis (BRH) posits that resident species can limit the demographic success of introduced species through herbivory, predation, competition, and parasitism.  Biotic resistance to biological invasions is hypothesized to be strongest at low latitudes due to higher native diversity and stronger biotic interactions. We have examined this hypothesis by comparing the abundance, species richness, and effect of metazoan parasites infecting the invasive lionfish (Pterois volitans) across 13 sites in the western Atlantic, encompassing 17 degrees of latitude. The invasion by the lionfish presents a unique opportunity to test predictions regarding latitudinal patterns of biotic resistance to invasion due to its rapid spread and broad geographical distribution.  We predicted that the diversity and abundance of parasites infecting P. volitans would be highest at low latitudes, and that higher parasitism at low latitudes would have a negative effect on the condition of the host. Overall, P. volitans were infected by few parasites.  Though parasitism was relatively low in lionfish, species richness and abundance of ectoparasites was significantly higher at low latitudes; meanwhile no such pattern was observed for endoparasites.  Furthermore, we did not find an association between parasite abundance (within or across parasite groups) and host condition at any site.  These results suggest that although lionfish are more parasitized at low latitudes, they experience little resistance from native parasites across their introduced range.  Results from this work correspond with the findings of previous studies on latitudinal patterns of parasitism for native marine fish.  This suggests that factors other than host-parasite evolutionary history may also play a role in structuring observed latitudinal trends in parasitism.


    The role of predators on the evolution of electric fish signals.

    Abstract: Brachyhypopomus occidentalis is a weakly electric fish that produces electric signals for navigation, prey location and communication. Recent studies have shown that populations of B. occidentalis across Panama are diverging in the shape of their electric signals, but we do not know if these modifications have been driven by selection. Electroreceptive predation has been proposed as a major selective force shaping the electric signals of weakly electric fish. The main objective of my research is therefore to investigate if electroceptive predation has been driving signal divergence in B. occidentalis.


    Supervisor: Catherine Potvin

    The good dweller's dilemma: A land tenure and forest cover analysis in Panama and its
    implications for REDD+ implementation

    Abstract: Conserving forest carbon stocks in forested areas of developing countries is an essential component for REDD+ yet IPCC guidance focuses on emissions and removals from the Land Use and Land Use Change and Forestry Sector. Using recent land cover maps, we assessed and compared different land tenure regimes in Panama with respect to forest cover and forest cover changes through time. We found that protected areas and indigenous territories, which collectively represented 77% of Panama's total mature forest area in 2008, had the highest forest cover and lowest deforestation levels. While protected areas and indigenous territories in Panama have shown similar forest coverage from 1992-2008, the lowest deforestation rates were found where indigenous territories comarcas and claimed lands) and protected areas overlapped. Our results suggest that in the future national REDD+ strategy, government investment providing incentives for REDD+ should strengthen existing protected areas and increase participation of indigenous peoples in REDD+ efforts. We discuss the implications of this finding for the establishment of a reference level and examine possible financial incentives that could contribute to the Panamanian REDD+ strategy. The discussion is relevant to high forest cover/low reforestation rate countries and jurisdictions. Recognition of good stewardship in national and international contexts will indeed help to maximize the effectiveness of REDD+ by reducing potential leakages and promoting equity in the program.