Category: Research

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Another piece in the trophic puzzle

Meles.meles

The food chain is a concept that many non-biologists are familiar with. Ecologically-speaking, this should be referred to as a food web, because there is rarely one prey species for a given predator or one predator of any given species.

The biochemistry of metabolism and digestion means we can reconstruct the diet of a member of a given food web with some basic information about the stable isotopes in its tissues and the stable isotope values of the available prey. Simply put, “you are what you eat”. Carbon isotopes generally reflect the “where” of the diet and nitrogen isotopes generally indicate the “what”.

This overview omits several complications. Firstly, the calculation of diet requires a “conversion factor” (trophic enrichment factor or TEF) for any given tissue of an animal. Animal metabolisms tend to retain 15N, so consumers have greater 15N:14N ratios than their prey. Secondly, each tissue is likely to have a different TEF, as it is made to perform a different job in the animal. Thirdly, TEFs can only be derived by feeding animals highly controlled diets, ideally a single food for the length of time it takes for the study tissue to be fully replaced. In the case of teeth and bone, this can be months or even years.

As there are relatively few TEFs available for animal species, many ecologists “borrow” TEFs from other species for their calculations. Having derived TEFs for carbon and nitrogen in badger blood serum, a tissue that is completely replaced several times a month, we demonstrated that badger TEFs differ from fox TEFs. This is important, as foxes are similar in size to badgers and have a similar feeding ecology, and ecologists might be tempted to “borrow” fox TEFs to use in badger studies.

So knowing more about the biochemistry of badgers (in the form of TEFs) will allow us to learn more about their diets. This may be of importance to farmers planning biosecurity measures for their farms, as they will be able to learn if badgers are raiding their crops (in the field or in the barn). It will also help identify when badgers are specialising on different foods and potentially allow farmers to minimise contact between badgers and livestock.

Authors

David Kelly: djkelly[at]tcd.ie

Nicola Marples

Photo credit

wikimedia commons

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Gorillas and/or potatoes?

Capture d’écran 2012-12-14 à 14.07.18

If you were given a resource that could guarantee revenue of $30 million every year, with almost triple that amount additionally coming through ancillary spending, would you ignore it? If this resource then had the power to lift some of the most marginalised people on the planet out of poverty, you would even think twice? Gorilla tourism in Rwanda is this valuable and the people living around Volcanoes National Park (one of the few remaining islands for this species) are some of the poorest in Africa. My research into interactions between the national park and local farmers has revealed that control of land is one of the key factors in creating conflict between the ideals of national park management and those of subsistence farmers. When people have little control over what they grow in this highly fertile region, either through government land use consolidation initiatives or private agro-industry, the impact of buffalos raiding potato fields or gorillas decimating eucalyptus plantations is exacerbated. The catch is, cultural values and hierarchies in Rwanda mean that leadership will be followed, as changes are effected unquestioningly. One solution is to increase the proportion of tourism revenue shared with local communities, instilling a feeling of ownership, and responsibility for, their forest. But this can only come with livelihood autonomy.

 

Author

Shane McGuinness: mcguinsk[at]tcd.ie

Photo credit

Shane McGuinness

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The selfish huddle

As it is December now and the frost is creeping in I thought I’d talk about one of the all time favourite winter animals: the penguin! These happy footed, tuxedoed up cartoon-esque waddlers are among the most charismatic and endearing of creatures. They are favourites in films, books, documentaries, toys and of course a must on Christmas cards. Tales of their romantic dances, lifelong partnerships and working together to get through the winter have long been a part of the ‘nicer side’ of wildlife television and research. But are these loveable, laughable poster birds of cooperation and cuteness really all that genuine? Recent research would suggest not…

It has long been observed that emperor penguins form mass huddles to help prevent heat loss while they incubate their eggs amid Arctic storms. Anybody who has watched March of the Penguins can’t help but feel for the poor mites as they shuffle about with ice crystals covering their faces! Morgan Freeman also gives a heart warming narrative of their struggles during this time and how they “take turns” to be at the centre of these huddles so nobody is left at the edges long enough to freeze entirely. Nice thought, but it seems not quite the reality. A paper published in Plos one last week looked at the mathematics of the famous penguin huddles. What they found was that the shape and movement of these huddles over time was most accurately (although not perfectly) described by individual penguins setting out to minimize their own heat loss, rather than generously taking turns.  Penguins at the edges seek to move toward the centre while those in the centre have neither the space nor inclination to move anywhere so remain stationary. The result is a dynamic huddle that actually achieves pretty uniform heat loss from the huddle. So in this case being selfish can benefit the group.

This is not the first account of penguins acting in a less than Disney-like fashion: they have been observed stealing pebbles from neighbours’ nests and waiting to see whether other, more hungry, souls fare okay in orca/seal infested waters before jumping in themselves. There are stories too of them pushing their fellows off ice floats in to swelling seas to check for leopard seals but these are largely dispelled by researchers as misconceptions of the unfortunate results of the hustle and bustle of clumsy penguins perched on cliff edges!

I’m sorry to shatter any illusions of a wholly philanthropist snuggly-for-the-sake-of-it penguin but it is another nice example of how we humans often choose to perceive interactions in the animal world based on our own ideas of moral obligation: we like to see penguins cuddling in the cold to say “see what we can face when we work together?” Don’t worry though, I am sure that none of these findings will do much to shake the penguins off of their happy-go-lucky, cuddly pedestals and they will still be a key player in the Christmas festivities and focus points of many a blockbuster documentary to come. After all, who can resist that waddle!?

Author

Deirdre McClean: mccleadm[at]tcd.ie

Photo credit

www.funnycutepics.com

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Bamboo systematics: less swaying in the wind

Young shoots of Phuphanochloa Sungkaew & Teerawat.: a new species and genus of woody bamboo discovered by TCD botanists.

The bamboos are an extraordinary group of plants and the only large group of grasses to diversify in forests. They represent a major radiation in the angiosperms with nearly 1,500 species. The Bamboo Phylogeny Working Group (including TCD botanists Sarawood Sungkaew and Trevor Hodkinson) have recently used molecular, anatomical and morphological characters to update the tribal and subtribal classification of bamboos including the new genus (Phuphanochloa) shown in the photo.

Authors

Sarawood Sungkaew

Trevor Hodkinson: hodkinst[at]tcd.ie

Photo credit

Trevor Hodkinson

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Sulawesi field report

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.

Author

Seán Kelly: kellys17[at]tcd.ie

Photo credit
Seán Kelly
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Hotbeds of photosynthesis evolution

Grasses rank among the world’s most ecologically and economically important plants including wheat, barley, rice and maize. Evolution of the C4 syndrome has made photosynthesis highly efficient in about half of their species, inspiring intensive efforts to engineer the pathway into C3 crops to improve drought and heat tolerance.  An international collaboration called the Grass Phylogeny Working Group (including Trevor Hodkinson, TCD) produced one of the most comprehensive phylogenetic trees of the grasses and used this to show how C4 evolution has evolved. Results published in the journal New Phytologist show that it has evolved repeatedly 22-24 times and within two groups in particular.

Author

Trevor Hodkinson: hodkinst[at]tcd.ie

Photo credit

Wikimedia commons

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Is island life easier?

Lemon-bellied White-eye (Zosterops chloris)

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?”

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The plight of the bumble bee; diapause, immunity and parasitic attack

Sphaerularia bombi with an everted uterus.

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.

References

1. Society of Biology News Page http://www.societyofbiology.org/newsandevents/news/view/469

Author

Sive Finlay: sfinlay[at]tcd.ie

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

Photo credit

Mike Kelly