Research Archives - Page 9 of 13

03/10/201414/02/2019

Sustainability Through Stability

I recently took part in a Tansley working group, an initiative that has a main working theme of advancing the ecological foundations of sustainability science. In this specific case we are seeking to construct a unified framework to help understand the multidimensional stability of ecosystems.

In an era of increased human activity, significant climate change and biodiversity loss, an understanding of the mechanisms and drivers of ecosystem stability has vast implications for both ecological theory and the management of natural resources.

One large challenge in the study of ecological stability comes from the complexity of ecosystems. The dynamics of an ecosystem depend not only on the network structure, the interactions among different species, but also on external perturbations that vary in context, intensity and frequency.

Another huge challenge is the multidimensional nature of ecological stability, with its many measures and definitions including resistance, resilience and temporal variation, all of which are themselves interrelated. Stuart Pimm, a member of the Tansley working group, reviewed four measures of stability in one of his early publications in Science (Pimm, 1984) and one blog from Jeremy Fox even summarized 20 different stability concepts!

Both theoretical and empirical ecologists have spent decades exploring the role of community structure, interaction strength and disturbance in determining the dynamics and stability of ecosystems. However, most of these studies only focused on a single aspect of ecological stability, underestimating the impacts and recoveries of populations and communities.

Failure to consider the multidimensionality of stability is magnified when the relationships among these stability elements are quite fragile. For example, one lake or reservoir may maintain its stability in total biomass following a disturbance by adjusting its nutrient load, but the community composition has changed dramatically.

To create a unified concept of stability across theoretical, field-based and experimental research the confusion in using and defining these different elements of stability must be cleared up.

A typical confusion arises from the usage of the term resilience, which can be defined as the recovery time or speed following a disturbance to a pre-disturbed state; for instance the time taken for an area of scrubland to recover from a wild fire. The method used to calculate resilience in the local stability of theoretical communities is impossible to detect in the real world. So there is an urgent need to fill this gap by making a framework that suits both empirical scientists and theory development.

And that is one of the main challenges the Tansley working group seeks to face. We aim to construct a framework of ecological stability across major global ecosystems through a review of the most up to date measures of ecological stability (both empirical and theoretical) using specific case studies. This will help researchers adopt a more comprehensive approach to investigate stability and facilitate the comparison across different systems and scales in the future. We will also evaluate the feasibility in applying theoretical stability measurements to real ecosystems and abandon those which will are next to impossible to obtain from the real world.

To communicate the importance of the stability concept to a much broader audience, we will provide videos as well as vivid examples to illustrate the concepts of the different stability elements and how to measure them. We have an enthusiastic belief that the Tansley group will make a big contribution to the standardization of concepts and measurement of the multidimensional stability.

Author: Marvin Qiang, qyang@tcd.ie, @MarvinQiangYang

Photo credit: http://www.changedbygrace.net/2012/09/21/faith-floods-and-finances/

23/06/201415/06/2014

Dig for victory

In a previous post I showed what I think being a palaeontologist is all about, especially the point that palaeontologists are different from oryctologists. The first ones study changes of biodiversity through time, the second ones extract fossils (but again, both are far from exclusive).

Here is a short summary of experience working at Upper Cretaceous excavation sites in the South of France (that’s around 80-65 million years old) namely in the Bellevue excavation site in Esperaza run by the Musée des Dinosaures.

First step is to find a place to dig.

Why along the road? It doesn’t have to be but it has two clear advantages: you can park your car next to it and it’s usually rich in fresh outcrops of rock (where you can find more fossils than in a crop field!).

The second step, once you’ve decided that there might be something in the outcrop you’ve just explored, is to remove all the “annoying stuff”. To palaeontologists that obviously means all the wonderful fauna and flora and their associated environment (usually soil) that are growing above the potential fossiliferous site (how rude of them!).

Once you’ve removed the layer of living stuff, you can start the long and interesting part: hitting rocks with a hammer and a pike during the hottest days of summer.

Finally, with a bit (a huge bit) of luck, you’ll find a fossil that was worth all this hassle.

Once you’ve found the fossil, the first step is to clean the surface facing you and start to build a trench around it in order to pour plaster over it and bring it to the lab. As you can see, paint brushes are useless here too: the hammer and the pike make ideal tools for the surrounding trench and an oyster knife and a smaller hammer do the cleaning jobs. Oh yeah, and a tube of glue. After around 80 million years, the bones get a bit fragile.

The last step is to properly clean the fossil in the lab by removing it from all the surrounding rock. The best tools are mini pneumatic-drills and loads of patience. When all that is done, the palaeontologist can start to work on the fossil.

You can find more impressive pictures on the Musée des Dinosaures webpage.

Author: Thomas Guillerme, guillert[at]tcd.ie, @TGuillerme

Images: Thomas Guillerme and Sébastien Enault (with the kind authorisation of Jean Le Loeuff). Feature image: http://www.libraryofbirmingham.com/

05/06/201404/06/2014

The Wakatobi Flowerpecker: the reclassification of a bird species and why it matters

I posted previously about my PhD research studying bird populations from the tropical and biodiversity-rich region of Sulawesi, Indonesia. I am happy to announce that the first paper as part of this research has just been published in the open access journal PLOS ONE. To read the full paper for free, click here. This work is a collaborative effort from staff in the Department of Zoology in Trinity College Dublin and Haluoleo University in Sulawesi. Here, I’d like to discuss the wider importance of the findings of this study.

My current research focuses on bird populations from peninsular South-east Sulawesi and the nearby Wakatobi Islands. The main focus of this paper was to reassess the taxonomic status of a population of birds from the Wakatobi Islands (i.e. whether these birds represent a species or subspecies). The birds in question belong to the flowerpecker family (Dicaeidae); a group of small and colourful, arboreal passerines found from Southeast Asia to Australia. The Wakatobi birds were originally described as a separate species (Dicaeum kuehni) from those on mainland Sulawesi by the renowned avian taxonomist Ernst J. Hartert. However, for reasons that remain unclear in the literature, the Wakatobi birds were later reclassified as a subspecies of the Grey-sided Flowerpecker (Dicaeum celebicum) from mainland Sulawesi. Therefore we decided the Wakatobi populations were deserving of reassessment. From comparisons of plumage and morphology (that is, the measurement of various features such as a bird’s wing and bill), as well as estimates of genetic divergence and phylogenetic relationships between Wakatobi and Sulawesi populations, our results suggest the Wakatobi birds deserve to be recognised as a distinct species. We have therefore recommended the Wakatobi populations be reclassified as Dicaeum kuehni, a species found only on the Wakatobi archipelago and put forward the common name ‘Wakatobi Flowerpecker’. For more detailed methods and results check out the paper.

“So what?”, you might say. Well, despite centuries of work from naturalists aiming to estimate the number of different species that exist or have existed on Earth (be they animal, plant, fungus, bacteria, etc) and further understand their evolutionary relationships, we still have a lot to learn! Therefore, this research adds another tiny piece to this enormous and incomplete jigsaw. Through a greater understanding of life on Earth we can attempt to answer some of the great philosophical questions, such as ‘Where and how did life start?’; ‘How and why do new species appear?’; ‘Why has life evolved to become as it is today?’; and ‘How have we, as humans, come to be?’. Anyway, let’s be honest, who doesn’t enjoy learning of a recently discovered species or simply one they haven’t heard of before (be they as cute as the recently discovered olinguito or as frighteningly ugly as the goblin shark)? But the endeavour to discover species and classify and quantify the diversity on life on Earth brings us much more than entertainment and endless fascination, it also has very practical applications. Data on the distribution and conservation status of species are one of the major sources of information used to inform conservation policy. Therefore, as we are in the midst of an extinction crisis, it is vital that these data are accurate.

In order to maximise our understanding biodiversity, particularly in the remote and poorly known Sulawesi region of Indonesia, we require multi-disciplinary research. For example, take a look at Figure 1 below. On the left are a male (above) and a female (below) Grey-sided Flowerpecker from mainland Sulawesi. On the right are a male (above) and a female (below) Wakatobi Flowerpecker. They look very similar, right? This is true. However there are subtle but consistent differences in plumage between the species (again, see the paper for more info on this). Without the collection of detailed morphological data and the generation of genetic sequences, we may have incorrectly concluded that these make up just one species, when in fact they are morphologically distinct, reproductively isolated and genetically very different. This demonstrates the need for modern research, not just in Sulawesi, but globally, to employ integrative research, combining traditional comparisons of colour, size and shape with modern genetic and phylogenetic analyses.

Figure 1. Plumage comparisons-p18pjcggcs1dgo1ulm1sor9s214bc — Figure 1. A comparison of plumage characteristics between male (top row) and female (bottom row) Grey-sided Flowerpeckers (left) and Wakatobi Flowerpeckers (right).

Despite the knowledge that the Sulawesi region is home to a large number of remarkable birds that are found nowhere else in the world, it has remained relatively poorly studied. Furthermore, there has been a lack of integrative ornithological research in the area and very little genetic sampling. Therefore, it is likely that avian species richness for the Sulawesi region is underestimated and that numerous bird species are awaiting description. On top of this, Sulawesi’s biodiversity is facing major threats from a rapidly expanding human population and mass habitat destruction, among other things. Unless we can encourage more multi-disciplinary research within the region, we will likely fail to recognise evolutionarily distinct lineages and run the risk of losing them forever.

Our current findings inspire many further questions. For example, why have the flowerpeckers on the Wakatobi islands become so different to their close relatives on mainland Sulawesi? In other words, what are the evolutionary pressures that have driven the divergence of the Wakatobi Flowerpeckers? By investigating these questions, we hope to learn more about the evolutionary processes of speciation and adaptation to living on islands. As the Wakatobi Flowerpecker is found only on the Wakatobi Islands, the protection status afforded to the islands may require reassessment. Furthermore, considering one unique bird species has evolved on the Wakatobi, could there be more? Watch this space.

Author and Images: Seán Kelly, kellys17[at]tcd.ie, @seankelly999

19/05/201412/05/2014

Mooching in Madagascar

I recently returned from a short stint of fieldwork in Madagascar. The purpose of our trip was to run some behavioural tests of echolocation in tenrecs but things didn’t exactly go according to plan. Therefore we had plenty of time to explore and experience some of the wonders of the 8th continent.

Here’s a few of our wildlife highlights…

Shower lizard — Our friend from the shower

Spider webs — Enormous spider webs which span an entire river bed!

Spot the Indri (like four year olds in panda suits..)

Red bellied lemurs — Inquisitive red bellied lemurs (*Eulemur rubriventer*)

Tenrec in a bucket! *Hemicentetes semispinosus*

Author and Images: Sive Finlay, sfinlay[at]tcd.ie, @SiveFinlay

16/05/201412/05/2014

Bumblebees are not deterred by ecologically relevant concentrations of nectar toxins

In a previous blog post I wrote about my work on “toxic nectar.” This paradoxical phenomenon occurs when potentially deterrent or toxic plant secondary compounds, usually associated with defense against herbivores, are found in floral nectar rewards. Throughout my PhD I’ve spent countless hours in the lab performing experiments on toxic nectar, discussed this work at Nerd Club, and presented it at conferences. After what seems like an awfully long time, our first article on nectar toxins has been published in the Journal of Experimental Biology. Here I want to describe what I think are the most exciting findings of the study, and also talk about how this work came to be part of my PhD.

When I first started my PhD I had what seemed like a never-ending list of questions about nectar toxins: do they impact plant fitness? What about pollinator survival? Are there sublethal costs to pollinators that ingest nectar toxins? But before we could tackle these bigger-picture concepts, we kept on coming back to a very simple question: are bees deterred by naturally occurring concentrations of secondary compounds in floral nectar?

We know that many plant secondary compounds, such as alkaloids, phenolics, and terpenes, play a role in deterring herbivores form consuming plant tissues, and that’s why toxic nectar is such a paradox. Why would plants have deterrent compounds in a tissue that is meant to act as a reward for pollinating flower-visitors? Nectar secondary compounds, however, tend to occur at much lower concentrations than those found in leaf or floral tissues. Previous work found that whether or not bees will forage on artificial nectar containing secondary compounds depends on ecological context, i.e. the availability of other food sources. However most work on this subject focuses on only one compound (gelsemine) and tests concentrations that are well above those found in floral nectar.

One might hypothesize that secondary compounds at nectar-relevant concentrations should not be deterrent to pollinators. If nectar toxins do deter legitimate pollinators, plant pollination and hence reproductive success could suffer, leading to selection for lower concentrations of nectar compounds. In addition, the direct impacts of nectar toxins on pollinators are still understudied; deterrence behavior might indicate a cost in terms of health or fitness for the pollinators. So we were convinced it was well worth determining deterrence thresholds for several of the most common/popular nectar toxins, and comparing these thresholds to nectar-relevant concentrations, but how did we do it?

The experimental design was very simple (my favorite kind!); we used an economically and ecologically important pollinator, Bombus terrestris, in a series of controlled, paired laboratory bioassays. In each assay, we offered bees two solutions of identical sugar content, one containing a secondary compound of interest and one without it. We repeated this 24-hour assay at a range of concentrations that included the nectar relevant dosage for each compound we tested. The deterrence threshold was determined when bumblebees significantly preferred the sucrose solution over the sucrose solution containing the compound. We also measured the total food consumed and bumblebee survival. I spent a lot of time in the laboratory and the bee room, weighing feeding tubes and counting dead bees; I’m not going to lie, I may have succumbed to talking to my bees now and again. It gets lonely in the lab! It was all worth it in the end though, because what we found was pretty interesting.

IMG_0038 (1) — These were my friends for many hours!

Our experiments showed that bumblebees are actually rather bad at detecting nectar toxins. The most deterrent compound was the alkaloid quinine, which was avoided at concentrations as low as 0.01 mM. All the other compounds we tested (caffeine, nicotine, amygdalin, and grayanotoxin) had deterrence thresholds 7-60 times greater than the concentration range naturally found in nectar. Previous work on the honeybee found that it too has poor acuity for the detection of nectar toxins, especially compared to insects in the orders Diptera and Lepidtopera. So why is it that social generalist bee species are relatively insensitive to the plant secondary compounds in their food? One hypothesis we highlighted in the discussion is that the relationship between bees and plants is largely mutualistic, as opposed to the antagonist interactions between plants and herbivores. There may not be strong enough selection pressure on bees to develop more sensitive gustatory receptors, especially because in eusocial bee species, individual bees are the consumers, but selection pressures act on the colony as the reproductive unit.

For decades, researchers of plant-animal interactions have been asking how and why toxic nectar evolved and is maintained in plant populations. Our work helps us to better understand the functional significance of toxic nectar. If legitimate pollinators fail to be deterred by nectar compounds at low concentrations, the plant is less likely to suffer from reduced pollination. This trait therefore may be maintained in plant populations, especially if it confers some sort of fitness advantage to the plant. What kind of fitness advantage could these compounds provide you ask? There are a plethora of possibilities, including antimicrobial resistance and selection against more sensitive nectar robbers or thieves. Possibly the presence of the compounds in nectar is simply a consequence of defense of other plant tissues. The results from our study, however, suggest that these other factors affecting nectar secretion and production are more likely to select for the production of toxins in nectar of bee pollinated plants, rather than pollinator preference.

Check the paper for more details and to read the whole story!

Author: Erin Jo Tiedeken, tiedekee[at]tcd.ie, @EJTiedeken

Images: Wikicommons and E.J. Tiedeken

05/05/201423/04/2014

Flatland

Why are there no elephants in the mountains?

Well, mainly because it’s costly to climb when you’re an animal of that size. A previous study estimated that a 4 tonne elephant would have to eat for 30 minutes to compensate for a 100m climb. Ideas man Graeme Ruxton and his co-author David Wilkinson develop this further in their new paper. They ask whether avoidance of hilly areas is to be expected in general for animals of a large mass such as the sauropods. These are the long-necked dinosaurs that were the largest terrestrial animals that ever existed. Some of the upper mass estimates of, albeit poorly described, species are over 100 tonnes! Using simple scaling relationships relating to the energetics of movement, food intake etc. Ruxton and Wilkinson show that as a herbivore increases in size the fraction of time spent eating to balance the cost of climbing will increase. In the case of sauropods we can look to the fossil record for support and it does show the creatures preferred flat environments such as fluvial plains. Their footprints and nesting sites are often preserved in these areas. Of course, energetic concerns aren’t the only issue stopping these animals from populating the hills. The danger of falling would be much higher on a friable surface and the bigger you are…

Any thoughts of regaining your energy on the way down after a costly ascent can be dispensed with. An animal must expend energy to control the rate of descent especially to avoid falling. One benefit of being large is that you have energy reserves so it is possible to travel into the hills if absolutely necessary but these forays would be infrequent.

This result suggests steep areas should be depauperate with respect to larger herbivores. We could imagine highland islands of smaller herbivores alongside plants which are free from the pressures of huge plant-eaters. The conclusion of the paper asks us to explore extant ecosystems for such a pattern. This could be extended to Mesozoic ecosystems. Perhaps there would be an ontogenetic niche shift in the sauropods, moving from hilly areas to the flatlands as they developed.

Author: Adam Kane, kanead[at]tcd.ie, @P1ZPalu

Image Source: Wikicommons

02/05/201403/05/2014

Silence of the Tenrecs

I’ve been studying tenrecs for almost two years. I’ve read about them, watched video clips and handled hundreds of dead specimens. However, within that time I only met two live individuals, both of which were captive zoo animals. That’s all changed. I’m now well acquainted with a variety of tenrec critters. It turns out they’re a quiet bunch.

Just slightly excited to be holding a live tenrec!

My supervisor, Natalie, and I spent two weeks in Madagascar working with a research team from the Vahatra Association led by Steve Goodman. The purpose of their trip was to conduct a disease transmission study in bats and small terrestrial mammals study at Ambohitantely Special Reserve, a protected, upland native forest north west of Antananarivo.

Ambohitantely forest surrounded by central plateau grassland — Looking down onto Ambohitantely forest; not a bad place to work…

We tagged along on the trip to run behavioural experiments to test whether there’s evidence for echolocation in the shrew-type (Microgale) tenrecs. Armed with a bat detector and an adjustable maze, my plan was to record the tenrecs’ calls as they move through their environment in search of a worm food reward at the end of the maze.

Our “experimental chamber”; the maze box (covered with material in the bottom right of the picture) set up in a shower cubicle!

I had envisaged many potential problems with the experiment. How would we be able to filter out interesting noises from background sounds? Would the noise of the animals moving around mask out the true vocalisations? I didn’t, however, foresee the problem with which we were faced; they didn’t make any noise whatsoever, zilch, not a peep.

We tried multiple methods to coax some sound out of the furry creatures. The animals were kept warm in Natalie’s increasingly bulging coat pockets. We tried to entice the animals using juicy worms as proverbial carrots. We experimented with placing pairs of individuals in the box at the same time hoping to overhear some tenrec chat. We also eliminated technical faults as a possible cause by testing out my detector on the bats flying around camp at night. All to no avail.

Microgale dobsoni; "I'm not going to produce any sound and you can't make me" — *Microgale dobsoni*; “I don’t want to produce any sound and you can’t make me”

I think they were holding out on us. The other, more experienced field researchers had heard tenrecs squeaking while foraging. The previous work on echolocation in tenrecs which inspired my experiments includes recordings of one species of Microgale so the animals are certainly not mute. I think our empty sound files are an unfortunate consequence of our experimental protocol. Existing research on possible echolocation in shrews and tenrecs used captive animals under highly controlled experimental conditions. We, however, were constrained by time and resources to an artificial experimental set up so it’s unfortunate but not entirely surprising that things didn’t go according to plan.

Still, the trip was far from wasted. Studying and observing living animals is just a tad more exciting than their museum counterparts and I now have enough pictures of tenrecs to last for a lifetime of presentations. We met some extremely interesting and knowledgeable researchers and we had the opportunity to work in a remote, beautiful and exotic place.

Furthermore, our failed experiments left time to go and explore other areas as tourists; expect our encounters with Indri, mouse lemurs, chameleons and enormous spiders to be coming soon…

Author and Images: Sive Finlay, sfinlay[at]tcd.ie, @SiveFinlay

28/04/201406/04/2019

Dying without wings: Part II

Last week our newest EcoEvo@TCD paper came out in PRSB (it will be Open Access soon but currently it’s behind a pay wall – feel free to email me for a copy in the meantime. Code for the multiple PGLS models can be found here). This paper is exciting for me for two reasons – firstly because the science is really cool and secondly because of how it came about. In a previous post I explained the results of the paper. Today I want to focus on how it came about. Continue reading “Dying without wings: Part II”

25/04/201406/04/2019

Dying without wings* Part I

Last week our newest EcoEvo@TCD paper came out in PRSB (it will be Open Access soon but currently it’s behind a pay wall – feel free to email me for a copy in the meantime. Also code to fit multiple PGLS models can be found here). This paper is exciting for me for two reasons – firstly because the science is really cool, and secondly because of how it came about. Today I want to focus on the paper itself, and in my next post I will explain how this collaborative project started. Continue reading “Dying without wings* Part I”

18/04/201406/04/2019

The Easter bunny’s origins are linked with climate change

The Easter Bunny apparently originated in German Lutherans’ traditions before 1682 when it was first mentioned in von Franckenau’s De ovis paschalibus. In France and Belgium however, it’s not a rabbit that hides eggs in the garden for Easter morning but flying bells coming back from Rome (they went there for their holidays since the Maundy Thursday). For many people this makes no sense at all (flying bells, come on!) but on the other hand I think that a bunny carrying coloured eggs and hiding them does not make much more sense… Continue reading “The Easter bunny’s origins are linked with climate change”