My PhD viva experience

As I mentioned in my last post I successfully defended my PhD viva (thesis defence) just over three weeks ago. As I was preparing to defend my thesis I found it helpful and often reassuring to read the experiences of other PhD students to get some idea of what I could expect. Of course, every viva will be different but below are some of my thoughts post-viva which I hope my be useful to others.

Preparation

In the weeks leading up to my viva I tried to prepare as best I could by re-reading my thesis and refreshing my memory of the major papers which I had cited often or based my own work upon. Apart from this I didn’t feel like I could really do much to prepare as I had no idea what questions I would be asked. At the time I found this quite stressful because I felt like I should have been working harder and doing more to prepare. Now with the benefit of hindsight I can see that I did the right things.

What my reviewers most wanted to know was that I understood and could explain my own work. Since I had spent the last 3+ years working on it this was not a problem! What I now know is that the preparation for my viva began on the very first day of my PhD. While it was helpful (and definitely recommended) to refresh my memory of the key points of my work in the weeks leading up to my viva,  the real hard work had already been done over the past years.

The warm-up

On the day of my viva I got up early and read a few notes one last time over breakfast. I then headed into my university for a pre-viva chat and coffee with my supervisor. This really helped calm any nerves I had as he seemed quite confident that I would have no problems.

In the hour before my viva began I had to go and register with the secretary before being shown to the room where I would meet my reviewers. Here I had to wait outside for quite a few minutes and it was at this point that I first started to get really nervous. I think because the time waiting gave me the time to think of all the possible worst case scenarios!

Eventually, I was shown into the room where my reviewers introduced themselves and explained what the viva was and what would happen over the next few hours. I was offered drinks which had been prepared for us (tea/coffee/water) before the viva really began. These first few minutes felt like a warm-up before the real questioning began.

Full-speed

The first thing I was asked to do was to explain in broad terms what my thesis was about, why I did it and what I had discovered. This was possibly the easiest question of the whole day as I had spent so long working on my PhD that I could explain it in my sleep. The only difficulty I had was condensing more than three years of results into fifteen minutes of explanation. This meant leaving out everything but the biggest and most important elements of my work.

On a couple of occasions I found myself spending too much time explaining minor details and had to force myself to move on to more important aspects of my work. Nevertheless, this question really helped me to get into the flow of explaining my research and after a few minutes I really felt like I was firing on all cylinders.

After this warm-up question things got a lot more detailed. My reviewers went through each chapter one by one and stopped wherever they had a question about something I had written or wanted some more detail about a particular point I had raised. In almost all cases these questions were not too difficult, and in most cases they were relatively easy to answer.

However, I don’t want to suggest that there were no difficult questions. On a couple of occasions a question was put to me that I couldn’t answer very well or a criticism of my work was made which I could only agree with. During the viva this made me quite uncomfortable, but now, with the benefit of hindsight, I can see that my reviewers pushed me to look at my work from a different perspective and consider new possibilities. This is probably one of the best things to come out of my viva and will really help me as I write-up some of my chapters for publication.

Towards the end

My viva was just under three hours long. It sounds like a really long time but it really didn’t feel like it. After the first few questions it felt more like a friendly discussion that an exam and I relaxed a little bit and started to feel slightly more confident. This, along with the stress and adrenaline really helped the time to fly by.

Once both my reviewers were satisfied that they had no more questions to ask me I was asked to leave the room for a few minutes while they discussed how I did and what the outcome should be. This was probably the most nerve-wracking moment for me as I really had no idea how well I’d done or what outcome to expect. After maybe five minutes I was asked back into the room where my reviewers both seemed happy and congratulated me on passing with minor corrections. This means I  have up to six months to make a few changes to my thesis which in reality should take no more than a week or two.

And relax!

The feeling of relief on being given the news that I had passed was overwhelming and I didn’t really know how to react. The corrections I need to make are only very small and my reviewers really seemed to like my work.

Once the viva was over I had a celebratory pint in the local pub with my supervisor, a reviewer and some friends. At this point I was still dazed, relieved, tired and hadn’t really full absorbed had what just happened. I think it took a full 24 hours before it really sank  in that all of my work over the past years had been worth it. Often it was fun, at times it was hard, stressful and I felt like I couldn’t do it. But now it has paid off and I am happy!


If you are a PhD student about to defend your thesis and have any questions about the process please feel free to email me or leave a comment. And most of all, good luck!

 

The end of the beginning

The very first post on this blog was written while I was still an undergraduate at the University of Derby. Today I am happy to say that I have just successfully defended my PhD thesis on the effects of urbanisation on the behaviour of song birds. This means not only can I order a new bank card with “Dr.” on it, but also that my time as a student has finally come to an end.

thesis-picture
The first draft of my PhD thesis just before I submitted it.

The question I have to ask myself now is what next?

Right now I am working at the Max Planck Institute for Ornithology in Germany and am loving it. I work with a really fantastic research group and I hope I will be able to stay here a while yet to pursue some of my research ideas. After that, I have no idea! I am considering several possibilities including continuing in academia long-term, working for conservation/environmental charities or applying for jobs in government environmental agencies. If you have completed a PhD I would love to hear in the comments what you did next.

As for this blog, I hope to revive it after its long and unplanned hiatus. As all PhD students know, the final year is the most intense and personally challenging. In the last year I have moved to Germany, written my thesis and published a paper. amongst all this I didn’t find the time for my poor blog! Now, however, I have a little more time and I plan to use it to write a series of blog posts on my PhD experience. Both the good and the bad. If there is anything you would like to know about the PhD experience please let me know below!

I also plan to write about whatever I do next. Although it is still quite unclear at the moment I am optimistic for the future and looking forward to the next challenge. The end of being a student me is really just the beginning of the next stage in my life and I can’t wait!

Different personalities. Great tits are not all the same. Image credit: Per Tillman.

My study species in four facts

ResearchBlogging.org
The last few months have been a blur of conferences, workshops. I attended a fantastic two week course on sensory ecology in Sweden (read about that here and here), I went to London and presented a poster of my work at the annual meeting of the Association for the Study of Animal Behaviour and have recently returned from the Joint meeting of the British Ecological Society and the Société Française d’Écologie in Lille. Time has been flying by and now Christmas is upon us but I wanted to write at least one more post for 2014 so here it is. These are four facts about my wonderful study species the great tit (Parus major).

Great tits have personalities.
My study species.

Every great tit has a unique personality

It’s true, you might think that a bird is just a bird and they are all the same but research has shown that this is not the case. In fact, many species of birds including great tits are now known to have distinct personalities and behave differently to one another, just like humans do. Researchers at Groningen University in the Netherlands found that when they exposed adult great tits to a completely new environment which they had never experienced before some birds were confident and bold and explored their new environments quite happily, while others were much more cautious and did not adapt quickly to the unfamiliar surroundings. Further tests have shown that birds which are bold or shy the first time they are tested tend to stay that way in repeated experiments. These results suggest that personality types are probably fixed characteristics which do not easily change. So, for anyone who’s ever said that animals have personalities, you were right. And it’s not just great tits either; research over the past few years has identified distinct personalities in a huge number of species including mammals, birds, insects and even anemones!

Different personalities. Great tits are not all the same. Image credit: Per Tillman.
Different personalities. Great tits are not all the same. Image credit: Per Tillmann.

City great tits just aren’t as colourful as their countryside cousins

With their bright yellow breast feathers and marked and glossy black plumage great tits are hard to miss at the best of times and are particularly conspicuous during the breeding season when the males are singing their hearts out trying to attract mates. The purpose of the great tits striking colouration is not fully understood but it is likely that females are most attracted to those males which have the brightest and boldest feathers. It is unfortunate then for city birds that their feathers just aren’t as bright as their rural counterparts. A likely explanation for this is that the same carotenoid compound which is used to create the bright yellow colour in great tits feathers is also an anti-oxidant which reduces the physiological stress caused by oxidising pollutants in the environment. As urban birds are known to be exposed to much higher levels of pollutants than rural birds it may be that urban birds are forced to divert carotenoids away from their feathers and use them instead to reduce the levels of stress and cell damage that oxidising compounds can cause. Evidence of this comes from a study at Göteborg University in Sweden which found that the increased oxidative stress faced by urban birds correlated well with reduced levels of carotenoid pigments in their feathers.

Great tits can be incredibly aggressive

They might look cute and friendly but in reality great tits can be incredibly violent, and particularly so during the spring and summer when males are competing for the best breeding territories. During this period male great tits mark their territories by singing at regular intervals and this signal tells other males to move on and find an empty territory of their own. This works most of the time but not always. Sometimes males deliberately invade territories and may attempt to mate with the resident female or even try to force the current territory holder out and take over completely. If this happens the first thing the resident male will do is to sing frequently and loudly in an attempt to show their strength and to drive the intruder away. Should this not work things typically escalate quickly as the resident male flies back and forth across the intruder before coming into full-on physical confrontation. It is not common to see fights in the wild as invaders will usually leave before it comes to actual violence. It does happen sometimes though and you can see the result in these incredible videos.

Great tits sing at higher frequencies in cities than in rural areas

Cities are notoriously noisy places full of cars, people and factories, with aircraft flying overhead and noise from building sites, road repair crews or similar urban development projects. This level of noise is something which wild animals have only had to face in the last century or so, and for species which communicate using sound it could make life in cities very difficult as their vocal signals are easily lost amongst the clatter and din of urban life. Great tits are a good example of a species which might be expected to fare badly in urban habitats as the males rely on communicating by song to defend their territories, show aggression towards rivals and attract mates. To make matters worse, the typical song of a great tit lies in exactly the same frequency range as the background noise of most cities and this means that when a great tit sings its song is quickly swamped by urban noise and cannot be heard by other birds. Yet despite this, great tits are one of the most common song birds seen in city parks and at garden bird feeders so how do they manage to cope with the noise problem? The answer is simple but ingenious. Urban great tits have adjusted their typical song frequency so that they now sing around 350Hz higher. That might not sound like much but experiments have shown that this small adjustments means that the song of urban birds travels above the low-frequency rumble of urban noise and can still be heard by other birds, even at long distances. Genius!

When there are high background noise levels great tits adapt by singing at a higher pitch. Figure from Slabbekoorn and Peet (2003).
When there are high background noise levels great tits adapt by singing at a higher pitch. Figure from Slabbekoorn and Peet (2003).

References

Every great tit has a unique personality

Dingemanse, N. (2002). Repeatability and heritability of exploratory behaviour in great tits from the wild Animal Behaviour, 64 (6), 929-938 DOI: 10.1006/anbe.2002.2006

City great tits just aren’t as colourful as their countryside cousins

Isaksson, C., Örnborg, J., Stephensen, E., & Andersson, S. (2005). Plasma Glutathione and Carotenoid Coloration as Potential Biomarkers of Environmental Stress in Great Tits EcoHealth, 2 (2), 138-146 DOI: 10.1007/s10393-005-3869-5

Great tits sing at higher frequencies in cities than in rural areas

Slabbekoorn, H., & Peet, M. (2003). Ecology: Birds sing at a higher pitch in urban noise Nature, 424 (6946), 267-267 DOI: 10.1038/424267a

Poster header

My poster for Behaviour 2013

I’m going to be spending the next few days in Newcastle at Behaviour 2013, a conference billed as the largest gathering of researchers working in the field of animal behaviour this year. Today we had talks on assassin bugs that actually attack and eat spiders on their webs, to bats that home in on the call of their unfortunate prey, the túngara frog. Tomorrow it all starts again bright and early with talks on everything from avian cognition to social learning and parental care. It’s so rare to be in a place where everyone shares my enthusiasm for animal behaviour, it’s great!

I’m not just going to listen to talks though, oh no,  I’m also presenting a poster showing some of what I’ve been working on for the last year. For those of you that won’t be there I thought I’d put the poster up here, I’ve received some good feedback on this so far but if you have any comments I’d love to hear them.

Click here for a high-res pdf version.

ASAB Behaviour 2013 poster

 

Grey seal pup in the grass

Highlights from the field season 2012

I’ve spent most of the last two months sitting in a small wooden box in the middle of a grey seal colony on the east coast of England. It wasn’t just for fun though, this was part of my research into the links between ‘personality’ and mate choice in female grey seals (you can read about that here). The data for my research comes from behavioural observations of grey seals in the wild. After 320+ hours of observation in the field I think I’ve seen almost everything that happens on a grey seal colony, these are some of the highlights…

As you might expect the weather in November and December can be very cold, we experienced everything from rain, hail and snow to howling gales to bright sunshine. The weather might not always have been welcome but it did make for some nice photographs.

Sunrise over the beach
Sunrise at 7am

We started each day at 6.00am, the mornings were hard but when the weather was good we were rewarded with sunrises like this.

The rainbow after the storm
The rainbow after the storm

The weather on the day this photo was taken was really bad, strong winds and heavy rain from morning till night. This rainbow appeared during a brief window of sunshine at about midday and made an otherwise bad day in the field worthwhile.

Fights were a regular occurrence on the colony, females would fight off the unwanted advances of the ever-present males or fend off other females if they got too close.

Two female grey seals fighting
Two female grey seals fighting

Some of the most memorable fights were between two males competing for access to females.

This photo was taken just before the fight began. The open mouth is a threat.
This photo was taken just before the fight began. Grey seals open their mouths and bare their teeth as a threat behaviour.

This video filmed at the start of the season shows just how aggressive males can be, and this fight was relatively tame!

There were of course lots of opportunities for photographing cute pups, these are some of my favourite photos.

Posing for the camera
Posing for the camera
Chilling out
Chilling out
Grey seal pup in the grass
Grey seal pup in the grass
Glowing
Glowing

Grey seal births can happen very quickly and so they are easy to miss. We were very lucky then to see this one up close, the female came right up to the hide before giving birth in front of the video camera!

Those are favourite moments from this season. I’ll be writing up more detailed posts about my research over the next year, in the meantime my lab group has a blog at www.sealbehaviour.wordpress.com that you might be interested in.

IMG_00701

How does urbanization affect biodiversity?

Imagine that you’re standing in the very centre of a large city complete with roads, skyscrapers, traffic, noise and pollution. How much wildlife is there around you? How many species are there? How much of what you see is native?

Now imagine you walk in a straight line out of the city, for every mile you walk you stop and observe the wildlife, You count how many species there are (species richness) and how many individuals of each species there are (abundance). What you are measuring is biodiversity, the straight line you are walking along is a transect. By studying biodiversity at regular points along the transect you are able to observe changes as the habitat becomes increasingly rural, in turn this allows you to determine what effect (if any) the city has on biodiversity.

Approaching the city centre. Species rich or Species poor?

So, what might you expect to find? Does biodiversity increase or decrease in response to urbanization? Are different species found in cities than in rural areas? Is there no change at all?

Sadly, it is often the case that urbanization causes biodiversity to decline. As cities grow vital habitat is destroyed or fragmented into patches not big enough to support complex ecological communities. In the city, species may become endangered, or even locally extinct as previously natural areas are swallowed up by the urban jungle. In the United Kingdom for example, an increasing human population density, and the resulting increase in urban development were found to be the cause of 35% of scarce plant species extinctions in the counties surrounding urbanized areas (2). Similarly, in the United States urbanization has been found to be directly responsible for the endangerment of 275 species, only invasion by non-native species had a greater impact causing 305 species to become endangered (1). Ironically it is urban growth that is often responsible for the introduction of non-native species, either accidentally (e.g. the brown rat, Rattus norvegicus), or deliberately, for food, pets or for aesthetic reasons. Non-native plants for example, are often planted in urban and suburban gardens and subsequently “escape” into the wild (3).

Why does biodiversity decline in urban areas?

The growth of cities may cause biodiversity to decline by fragmenting or destroying large areas of natural habitat on which many species depend. The rising human population is driving the expansion of urban areas and increasing the demand for natural resources such as timber and fossil fuels. This inevitably leads to habitat destruction which has been called “the largest factor contributing to the current global extinction event”(4). The rate of urbanization is alarming, for example, in the city of Concepción, Chile, 1734ha of wetlands and 1417ha of agricultural land, forest and scrub was lost to urban development between 1975 and 2000 (5). Similarly, in the United States the amount of urbanized land has increased year on year since 1970. Over 5% of the US land surface is now urbanized, substantially exceeding the combined total of both conservancy and national park land cover (3).  Although there are many causes of habitat loss, urbanization has been shown to be one of the most damaging in terms of numbers of species lost or threatened (2).  Numerous studies have found that both the richness and abundance of native species including plants (1), mammals (6), insects (7) and amphibians (8) decrease in response to urbanization.

Closely related to habitat loss is habitat fragmentation which can be defined as the transformation of a large and continuous habitat into many smaller, isolated habitats. The expansion of cities causes the fragmentation of large areas of natural habitat through the construction of roads, houses and industry. In many cases all that remains are small remnant patches of the original habitat contained within the confines of the city. Biodiversity is greatly reduced when large areas of natural habitat are fragmented. Small habitat patches are unable to support the same level of genetic or taxanomic diversity as they formerly could (9), while some of the more sensitive species may become locally extinct (4).

How severely fragmentation affects biodiversity depends to a large extent on the size of habitat patch that remains. Many species require large contiguous habitat patches in order to maintain stable populations. Smaller patches therefore typically contain fewer species than do large patches. As an example, a study in the US looking at forest birds in fragmented and contiguous forests found that in fragmented forests brood parasitism and predation on the birds significantly increased whilst reproductive success declined (10). Similar effects have also been shown for reptiles. Predation pressure on the lizard Psammodromus algirus was found to increase as patch size decreased leading to the lizard’s  extinction in small patches while populations in large patches remained viable (11). Small patch size can also have genetic effects for example, it was found that populations of the plant Trillium camschatcense had much lower genetic diversity in fragmented habitat compared to those growing in contiguous habitat (12).

Understanding the impact of small patch size is critical for scientists and conservationists alike if biodiversity is to be preserved. However, it is not the only factor in need of consideration. The distance between habitat patches and the quality of the intervening land also have significant effects. For example, two closely spaced patches of woodland habitat separated by farmland are likely to be much more biodiverse than the same habitat isolated on either side of a city. Populations occupying habitat fragments are rarely self-sustaining, rather they act as sinks relying on immigration from larger stable populations to remain viable. As a result poor quality intervening habitat or a high degree of isolation may substantially reduce the long-term survival potential of fragment populations (12). Different species have different requirements, some may be able to tolerate high levels of fragmentation and isolation while other more sensitive species may not. However, if we are to preserve biodiversirty for the future reducing habitat loss and fragmentation should be priorities.

In addition to the twin effects of fragmentation and habitat loss there is another factor working to reduce biodiversity in urban areas. Biotic homogenization refers to the replacement of regional native (and often endemic) species with non-native, invasive and cosmopolitan species. Often it is the same non-native invasive species that are found in many cities worldwide (for example the rock dove Columba livia could be considered a global species), the result is a high species overlap between areas of formerly distinct biota, the homogenization of biological communities and a decrease in regional and global biodiversity (13, 14).

Many studies have shown that the expansion of the urban environment causes declines and local losses of native species including plants (1) and insects (15). As native species decline the number of non-native species rises. For example, as of 2006 New York city has lost 578 native species and gained 411 non-natives meanwhile, Massachusetts has lost over 330 native species and gained over 200 non-native species (16). It has been suggested that the increase of non-native species in urban areas may be due to one of two factors, (i) the importation into cities of non-native species and (ii) the city providing a favourable habitat for non-native species (16). Human settlements have been shown to provide ideal conditions for invasive and exotic species due to high levels of disturbance which tends to favour non-native species at the expense of native species (17).

The removal of native species from urban areas and their replacement with non-native species drastically alters the composition of urban biological communities, the ecology of cities is therefore very different to the surrounding undeveloped areas. For example urban bird communities are often composed of granivorous (seed eating) rather than insectivorous species (18), while insect communities have been shown to become more generalist towards the urban centre and more specialist in less urbanized environments (7).

Replacing native species with non-native species does not necessarily cause biotic homogenization. If different communities of non-native species replace native species at cities around the world then biotic differentiation rather than homogenization will have occurred. However, there is no evidence that this is happening. Many studies have shown that the extirpation of native species in urban environments and the influx and non-native invasive species is leading to global biotic homogenization. For example a study of urban bird populations from two distant locations (Ohio and California) found urban populations to be much more similar to each other than rural populations the same distance apart (19). Similarly, a study in Canada found that the ecology of cities across the country was becoming increasingly alike with many of the same species found in cities nationwide (14).

The trend towards global biotic homogenization of urban areas poses a serious threat to local, native species in countries around the world. The importation and introduction of exotic species is changing biological communities by forcing out local indigenous species, which may not be so well adapted to the urban environment, and replacing them with globally common and widespread species. If we are to preserve distinct regional species the importation of non-natives species should be discouraged and the diversity of native and indigenous species promoted and protected.

Does biodiversity always decline?

Perhaps surprisingly, no. Although many studies have found that declines in biodiversity and increasing urbanization are strongly correlated (5, 15), research has also shown that in some situations biodiversity actually peaks in suburban areas for certain groups such as insects (7), and plants (6). For example, it was found that in the Finnish city of Vantaa the number of vascular plant species was much higher on urban wasteland than in the surrounding forest. The reason being that wasteland contained large numbers of non-native introduced plant species while the forest did not (20).

Three explanations have been proposed that may explain the suburban peak in biodiversity, (i) The import of exotic species into urban areas increases species richness at a faster rate than native species are lost. (ii) Urban areas contain a large number of widely different habitats at small scales such as gardens, parks and wasteland. Each of these may provide very different habitats and so support a wide variety of species, urban gardens in particular are highly variable with no two containing quite the same combination of plants. (iii) The importation of large amounts of water, fertilizers and food into urban areas provides the nutrients required to significantly increase primary productivity. This in turn supports larger numbers of individuals than would be able to survive otherwise. These three proposals are not mutually exclusive, it is likely that all three (and possibly other factors) play a role in increasing urban biodiversity (6).

My research

I have been studying the effects of urbanization on biodiversity in the city of Leicester in the UK. By collecting arthropods along an urban-rural gradient I have been able to observe changes in species composition, richness and abundance. The diversity of arthropod communities then served as an indicator of the overall biodiversity of the sampling area.

Using sets of pitfall traps set at one mile intervals along the gradient, I collected just over 2000 arthropods belonging to more than 250 species over a period of one month. By identifying how many species and  individuals of each species were found at different locations along the gradient I was able to identify changes correlated with urbanization.

The aim of the study was to answer two questions. (i) Does urbanization affect biodiversity? And (ii) If so how?. Although these questions have been answered many times before the results have varied widely depending on location and experimental design of the studies. Previous studies have also often focused on a limited range of taxa such as bees (15) or plants (1), whereas this study aimed to examine biodiversity as a whole. Finally, with a few notable exceptions (1, 21) there has been little research of this type in Britain, the hope therefore, is that this study will provide an interesting insight into the response of Britain’s wild flora and fauna to urban development.

References

1. Thompson, K. and Jones, A. 1999. Human Population Density and Prediction of Local Plant Extinction in Britain. Conservation Biology. 13, 185-189.

2. Czech B, Krausman P.R, Devers P.K. 2000. Economic Associations Among Causes of Species Endangerment in the United States. BioScience 50, 593–601.

3. McKinney, M. 2002. Urbanization, Biodiversity and conservation. BioScience. 52, 883-890.

4. Fahrig, L. 2001. How Much Habitat is Enough?. Biological Conservation. 100, 65-74.

5. Paucharda, A., Aguayob, M., Peñaa, E., Urrutia, R. 2006. Multiple Effects of Urbanization on the Biodiversity of Developing Countries: The Case of a Fast-Growing Metropolitan Area (Concepción, Chile). Biological Conservation. 127, 272-281.

6. McKinney, M.L.. 2008. Effects of Urbanization on Species Richness – A Review of Plants and Animals. Urban Ecosystems. 11, 161-176.

7. McIntyre, N.E., Rangob, J., Faganb, W.F., Faeth, S.H. 2000. Ground Arthropod Community Structure in a Heterogeneous Urban Environment. Landscape and Urban Planning. 52, 257-274.

8. Riley, S.P.D., Busteed, G.T., Kats, L.B., Vandergon, T.L., Lee, L.F.S., Dagit, R.G., Kerby, J.L., Fisher, R.N., Sauvajot, R.M. 2005. Effects of Urbanization on the Distribution and Abundance of Amphibians and Invasive Species in Southern California Streams. Conservation Biology. 19 (6), 1894–1907.

9. Cane, J.H., Minckley, R.L., Kervin, L.J., Roulston, T.H., and Williams, N.M.. (2006). Complex Responses Within a Desert Bee Guild (Hymenoptera: Apiformes) to Urban Habitat Fragmentation. Ecological applications. 16 (2), 632–644.

10. Diaz, J.A., Carbonell R.,Virgos E., Santos T., Telleria J.L., 2000. Effects of forest fragmentation on the distribution of the lizard Psammodromus algirus. Animal Conservation. 3, 235–40.

11. Robinson, S.K., Thompson III, F.R., Donovan, T.M., Whitehead, D.R. and Faaborg, J.. (1995). Regional forest fragmentation and the nesting success of migratory birds. Science. 267 (5206), 1987-1990.

12. Tomimatsu, H., and M. Ohara. 2003. Genetic diversity and local population structure of fragmented populations of Trillium camschatcense (Trilliaceae). Biological Conservation 109, 249–258.

12. Donovan, T.M., Thompson, F.R., Faaborg, J., Probst, J. 1995. Reproductive success of migratory birds in habitat sources and sinks. Conservation Biology. 9 (6),1380–95.

13. McKinney, M.L. and Lockwood, J. L.. 2001. Biotic Homogenization: A Sequential and Selective Process. In: Biotic Homogenization. New York: Kluwer Academic/Plenum Publishers. 1.

14. Olden, J.D., Poff, N.L., Mckinney, M.L.. 2006. Forecasting Faunal and Floral Homogenization Associated with Human Population Geography in North America. Biological Conservation. 127 (9), 261-271.

15. Ahrné K, Bengtsson J, Elmqvist T. 2009. Bumble Bees (Bombus spp.) along a Gradient of Increasing Urbanization. PLoS ONE 4(5): e5574.

16. McKinney, M. 2006. Urbanization as a Major Cause of Biotic Homogenization. Biological Conservation. 127, 247-260.

17. D’Antonio, C., Meyerson, L.A., 2002. Exotic plant species as problems and solutions in ecological restoration: a synthesis. Restoration Ecology 10, 703–713.

18. Grimm, N.B., Faeth, S.H., Golubiewski, N.E., Redman, C.L., Wu, J., Bai, X., Briggs, J.M. 2008. Global Change and the Ecology of Cities. Science. 319, 756-760.

19. Blair, R.B., 2001. Birds and Butterflies Along Urban Gradients in two Ecoregions of the United States: is Urbanization Creating a Homogeneous Fauna. In: Lockwood, J.L., McKinney, M.L. (Eds.), Biotic Homogenization. Kluwer Academic/Plenum Publishers, New York, pp. 33–56.

20. Niemelä, J. 1999. Is there a need for a theory of urban ecology?. Urban Ecosystems. 3, 57–65.

21. Thompson K, Austin KC, Smith RM, Warren PH, Angold PG, Gaston KJ (2003) Urban domestic gardens (I): putting small-scale plant diversity in context. Journal of Vegetation Science 14, 71–78.