Stephen Leahy at the Guardian reports on a battle between science and politics which is worth highlighting. The Atlantic cod fisheries in the Atlantic collapsed during the 90s due to overfishing. They have yet to recover. The Atlantic cod is an apex predator and its decline effected a trophic cascade, which modified the original food web, perhaps irrevocably.
The Canadian government is holding the grey seal responsible for this. They argue that the seals, which are growing in number, are preventing the recovery of the stocks and are planning to kill 70,000 of them next year.
This has vexed a group of marine biologists at Dalhousie University so much that they wrote an open letter arguing that cod are rarely preyed upon by the seals. Instead, the cod’s main predators are other, larger fishes. And in actual fact, the seal preferentially feeds on these fishes. So any reduction in seal numbers will produce the opposite result to the one intended, seals will be killed, the predatory fish population will increase, and the cod population will decline even further.
Correlation does not imply causation. But perhaps, the view of the Canadian government is that of Winston Churchill who once remarked, scientists should be on tap, not on top. It will be interesting to see how this one plays out.
It’s worthwhile highlighting the recent success of the “Biodiversity in Our Lives” campaign which has generated some notable publicity this week in Science. PhD students here at Trinity College decided to impress upon the public some facts about biodiversity and how it can impact our lives, often in surprising ways. To do this they decided to create a series of beermats which have succinct descriptions of these impacts. Pubs around Dublin have received a second round of the beermats and to coincide with this many of the students are giving pop up pub talks.
For the longest time floral nectar was considered to be made of two components: simple sugars (such as sucrose, fructose and/or glucose) and water. Research carried out in the past two decades however has repeatedly shown this paradigm to be incorrect. As analytical techniques such as high resolution GC-MS and HPLC have become commonplace, the composition of floral nectar of hundreds of plant species has been investigated in detail. The findings of this research have revealed that floral nectar has a lot of components other than sugars; amino acids, lipids, proteins, and vitamins have been detected at low concentrations. One surprising class of constituents of floral nectar has been found in plant species belonging to over 21 different families; plant secondary metabolites. It is strange to see these secondary metabolites- compounds such as alkaloids, terpenes, and phenolics- in floral nectar because we normally associate them with defence of plants against herbivores. They are often repellent to insect visitors and can potentially cause floral nectar to be unappealing to flower-visitors. The paradoxical phenomenon has many potential adaptive and non-adaptive hypotheses (see Adler 2000 for an excellent review) and it’s a subject about which there has been some really exciting literature published lately.
At NERD club one of our discussions focused around this topic of “toxic nectar”. I study the toxins found in the floral nectar of Rhododendron ponticum, a group of compounds called grayanotoxins. R. ponticum is invasive in Ireland and I am particularly interested in the effects of these toxins on native Irish insects that may use this mass flowering resource in early spring. Our discussion ranged from thinking about work done in other systems in which plant toxins might play an important role to considering trophic accumulation and mechanisms by which organisms deal with ingestion of toxins. I enjoyed the meeting immensely and it made me reflect upon how useful it is to discuss your research with as many people as possible. The varying opinions and perspectives that colleagues form different departments can bring to the discussion are both insightful and inspirational. We get so involved in our own research it is refreshing to hear these different perspectives, so thanks to everyone who could come along!
Charles Darwin Bacteria (Serratia marcescens), Nutrient Agar, Petri Dish
The concept of using bacteria and other microbes to test some of the big questions is creeping more and more into the world of ecology and evolution. Evolutionary biologists have been coming around to this idea for many years now (see Lenski’s experiment for a wonderful example of this) but the concept is still hard for most ecologists, particularly empirical ones to swallow. This is primarily a function of the microbial systems being thought of as ‘too simplistic’ and ‘unrealistic’ to apply to real world populations. In a review in 2009 Angus Buckling and colleagues very elegantly address the above charges and some of the other most frequently raised arguments against using bacterial microcosms. My argument (and his!) essentially comes down to two things:
1. Ecologists are supposed to be devising models and experiments to understand the dynamics of real world populations and the consequences of anthropogenic impacts on the organisms that inhabit the planet and yet they are largely ignoring the biggest Kingdom of organisms-Bacteria!
2. While nobody is suggesting that what happens in a 200ml microcosm tube will perfectly mimic or predict the exact response of a 200acre coral reef, why can they not be used as models to help test some of the theories or predictions that might equally affect larger systems?
Microbial systems have very similar dynamics to most other empirical food webs, in particular aquatic ones with highly size-structured predator-prey interactions, social cooperation and complex community networks. The importance of bacteria and microbes in the environment and their role in disease is undeniable and widely recognised meaning that individually bacteria are some of the most well studied organisms out their in terms of their genetic information and growth patterns. This can be used to the advantage of ecologists and evolutionary biologists by isolating strains of particular interest and culturing them very easily in laboratory conditions over short time periods to yield potentially very powerful results when viewed at the population or community scale.
One of the big problems in the field of ecology is linking empirical and theoretical study results; they frequently disagree due to the time scales, interactions and networks involved. The problem is basically that, however good the theoretical model, it cannot encompass all of the complexities of a natural system, and, similarly, while the empirical studies are more difficult to rebuke for their lack of realism or complexity, it is often impossible to disentangle the many different interactions taking place to get to the root of the question. What is therefore needed is a means to bridge this gap and provide logistically feasible model systems for testing more generalized ecological and evolutionary theory. I think the microbial systems might be a partial solution to this problem, as well as being fascinating for their own sake they can really aid in the developing and testing the drivers and disentangling the complex interactions in ecological and evolutionary processes. What they lack in size they certainly make up for in potential!
Scientific conferences can be a great way of meeting people, getting and sharing new ideas, and networking with people from, often, all over the world. And they can be good fun too! On October 25th-28th several people in the School travelled to Norway for the annual conference held by the Scandinavian Association for Pollination Ecologists (SCAPE). This meeting is held for ecologists working with pollination, plant reproductive biology and other related fields and it attracts a small but expert crowd from Scandinavia, Europe, and sometimes even further afield (this year there were attendees from Brazil and Israel!). Continue reading ““See you later, pollinator””
A Lemon-bellied White-eye Zosterops chloris with nesting material in its bill, Tomia Island
July and August of this year saw members of the Behavioural and Evolutionary Ecology research group embark on another field season studying the birds of tropical south-east Sulawesi, Indonesia. Principal investigators Dr. Nicola Marples and Dr. Dave Kelly were joined this year by PhD student Seán Kelly, as well as a number of undergraduates from the university. This year’s expedition, carried out in collaboration with Operation Wallacea, consisted of two teams: the mist netting team, led by Dr. Marples and Dr. Kelly, and the behavioural team led by Seán Kelly.
The netting team trapped birds using mist nets at various locations on Buton island, mainland south-east Sulawesi and Wangi-wangi island (of the Wakatobi archipelago). While small passerines such as white-eyes, sunbirds and flowerpeckers were the target species, individuals from a total of 35 species were caught. The season proved to be a great success with over 300 birds trapped and processed. Data on plumage, morphology, age, sex and breeding condition were collected from each bird, which was colour-ringed and released unharmed. A small number of body feathers were also plucked from each bird for later genetic and stable isotope analyses.
The behavioural team spent the season on various islands of the Wakatobi archipelago collecting detailed behavioural ecology data on the white-eye, sunbird and flowerpecker species present. This included information on their diets, competitors, preferred habitats, social habits, courtship and breeding, as well as their foraging and flocking behaviours. Data collection took place in the early morning and evening, walking 1 km transects through scrub, farmland or forest edge habitats. This resulted in some fantastic insights into the behaviour and ecology of these poorly studied species.
From analysis of the plumage, morphometric and genetic data we have found a number of significant differences between bird populations on the Wakatobi archipelago and mainland Sulawesi, as well as between populations within the Wakatobi. It is hoped that the behavioural data gathered this season will help us to understand the selective pressures driving this divergence, giving us further insight into the evolution of this region’s fascinating avifauna.
A new paper has been published in Science by George Sugihara and colleagues, which is an immediate contender for the most insightful paper I’ve ever read. In the paper they outline a new method, which they dub ‘Convergent Cross Mapping’ (CCM), for detecting causality between variables using time series data. Not only does CCM allow for the detection of causality but also its directionality. The method takes us well beyond the previous confines of Granger causality (which requires the assumption that systems are linear, or are showing linear behaviour near an equilibrium), and allows us to tease out causality in systems that show non-linearity and chaos. As examples of possible applications of their method the authors address two classic causality problems:
Predator-prey dynamics of Didinium and Paramecium. The authors show that there is bidirectional causality in this classic predator-prey system, but that top-down control is stronger than bottom up control (i.e. Didinium has a larger effect on the Paramecium population than vice-versa).
Dynamics of Pacific sardines and anchovies. There has been a long-standing debate about the cause of alternating dominance between sardines and anchovies in the Pacific. Some arguing that competition between the species is the driver, while others claim the pattern is caused by differing responses to temperature. The authors weigh in on this debate by showing that, while sardine and anchovy abundance is negatively correlated, this is a mirage as there is no causation in either direction. The authors also unambiguously show that sea surface temperature does causally affect the abundance of both species, indicating that climate is the main driver.
I think this method will be absolutely invaluable to future studies, and for me has already proved its worth from the results the authors present. The videos below are from the supplementary information of the paper and explain the method simply using beautiful illustrations.
I spoke before of how to use mathematics to convey an idea in biology. Here, I’ll take a different tack and discuss a paper in which the author makes his argument with naked English. The author in question is Nicholas Humphrey who in his famous paper ‘The social function of the intellect’ draws a wonderful metaphor of Mother Nature as an economist,
“It is not her habit to tolerate needless extravagance in the animals on her production lines: superfluous capacity is trimmed back, new capacity added only as and when it is needed”.
His metaphor serves as an introduction to the puzzle of the seemingly unnecessarily inflated intellects of some animals, notably humans.
Humphrey questions if such a highly developed intellect is really necessary for invention. The ability to produce tools is generally not a result of deductive reasoning or creative thought but rather follows from aping other individuals or pure trial and error learning. The intellect must have some other function in his estimation and in the end, he proposes that it is as a social glue. The complex interactions that arise out of the social milieu require some serious intellectual horsepower,
“[S]ocial primates are required by the very nature of the system they create and maintain to be calculating beings; they must be able to calculate the consequences of their own behaviour, to calculate the likely behaviour of others, to calculate the balance of advantage and loss – and all this in a context where the evidence on which their calculations are based is ephemeral, ambiguous and liable to change, not least as a consequence of their own actions.”
Calculating the consequences of your own behaviour is one thing but understanding that others around you have motivations of their own is a huge leap in understanding. All of this is done without ever having direct access to the subjective thoughts, motives, and desires of another person. Understanding the reasons for understanding is even more impressive and Humphrey’s paper has rightly influenced the theories of scientists since its publication. Most recently a study in the school that mechanistically linked sociality and selection for intelligence.
For over 10 years we have been making regular visits to islands in the Sulawesi region of Indonesia. We trap birds on these islands, collecting morphometric data. Each bird we trap is measured, marked with a plastic ring and released. As our dataset grows we gain more insight into the lives of the birds on these islands.
In 2007 and 2010 we visited the island of Kaledupa in the Wakatobi archipelago. In 2010 we made a point of revisiting all of the sites we had trapped at in 2007. This gave us an opportunity to look for the birds we had originally caught in 2007. Continue reading “Is island life easier?”
Bee populations are in severe decline, an alarming and worrying trend when you consider their vital importance as commercial and ecological pollinators. Research and media attention often focuses on afflictions of honeybees such as the Varroa mite and colony collapse disorder. However, parasites are also major contributors to the plight of the bumble bee.
Bumble bee queens spend 6-9 months in diapause, a hibernation-like state which allows them to survive harsh winter weather. My research demonstrated that queens have reduced immune function during this time, leaving them vulnerable to infections and parasitic attack.
Sphaerularia bombi is a common yet poorly studied nematode which is found primarily in the Northern hemisphere, infecting up to 50% of queen bumble bees in some areas. Adult female Sphaerularia present in the soil infect diapausing queens. My project showed that, with their immunological guards down, the queens cannot mount an effective response to invading parasites.
Sphaerularia exerts significant influence on its host after the queens emerge from diapause. The nematodes evert their uterus to a structure 300 times the volume of the rest of their body (see picture above). This enormous uterus releases numerous eggs into the host and also extracts nutrients from the bees.
Sphaerularia castrate the queens so they don’t form new colonies. The parasite also changes queens’ behaviour so they go to sites suitable for diapause even though it’s the wrong time of year. Having released larval stage nematodes into the soil, parasitised queens die while the nematodes are then poised to infect new queens entering diapause.
Sphaerularia clearly has a significant impact on a host species with high ecological and commercial value yet it remains very poorly studied. In collaboration with research currently being performed by PhD student Joe Colgan (Trinity College Dublin: Supervisor Dr. Mark Brown) and Dr. Jim Carolan (National University of Ireland, Maynooth), my project filled some of the gaps in our understanding of the molecular interactions between host and parasite. One particularly interesting finding was that S.bombi infection seems to change the protein expression in bees, indicating a complex interaction between host and parasite at the molecular level in parallel to the dramatic physiological and behavioural changes in the bees.
Continuation of this research on a fascinating host-parasite system will bring us closer to understanding and hopefully eventually combatting the plight of the bumble bee.
Sive is a PhD student from Trinity College Dublin, who recently won Best Biology student at the 2012 SET awards for her undergraduate project detailed here
