Flowering early or shifting north

This is my first blog entry in English. I’ve been blogging in Japanese for over 8 years (!) and I’ve come to realise that it is a very effective way of conveying things to many people, including those I’ve never met. Having tweeted in English for 2 years, I’ve decided that I want to write in English and make it available to more people. I probably won’t blog very often, but I’m hoping to write something at least when my new papers come out. As many of you would know, there are so many things we can’t say within a short manuscript. I want to use this space to write what I couldn’t write in the paper.

Today I will write about my new paper*, which has just been published in Proceedings B. The main finding of this paper is that the two types of plants’ responses to warming climate, range shifts and flowering changes, are linked in a complementary manner.

*Amano, T., Freckleton, R.P., Queenborough, S.A., Doxford, S.W., Smithers, R.J., Sparks, T.H. and Sutherland, W.J. (2014) Links between plant species’ spatial and temporal responses to a warming climate. Proceedings of the Royal Society B: Biological Sciences 281: 20133017.

It is well known that under warming climates some species shift their ranges poleward while others don’t. What causes this varied response among species is still under debate. In this study we propose that phenological changes may be a reason. Using historical records of distribution (Atlas of the British & Irish Flora) and flowering dates (Nature’s Calendar) of over 200 British plant species, we showed that species that have not moved northward in the past few decades have instead tracked warming temperatures (or “conserved” their climatic niche) by advancing their flowering dates. The link was particularly strong in annual plants, probably because flowering at the right timing is more critical for an annual plant as it only gets the one chance to reproduce.

For example, Rue-leaved Saxifrage (Saxifraga tridactylites) has advanced its flowering dates by 11 days during the past 50 years and has successfully tracked increasing temperatures during flowering time.

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Changes in the first flowering dates of Rue-leaved Saxifrage, based on the species-level index developed in Amano et al (2010)*.

* Amano, T., Smithers, R.J., Sparks, T.H. and Sutherland, W.J. (2010) A 250-year index of first flowering dates and its response to temperature changes. Proceedings of the Royal Society B: Biological Sciences 277: 2451-2457.

Consequently, this species’ range has not moved north (mean latitude actually moved south by 0.07 degrees) over the same period.

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Changes in the geographical range of Rue-leaved Saxifrage. Blue, red and black dots show observations only in 1987-1999 (new colonization), only in 1930-1960 (local extinction), and in both periods, respectively.

In contrast, Blue Fleabane (Erigeron acer) has only slightly advanced its flowering dates (by 3 days over the past 50 years) and thus, experienced increasing temperatures during flowering time.

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Changes in the first flowering dates of Blue Fleabane.

Consequently, the mean latitude of this species’ range has moved north by 0.13 degrees over the same period.

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Changes in the geographical range of Blue Fleabane.

Many studies have reported species’ range shifts and phenological changes, but most of the studies have treated these two types of species’ responses separately. Our study indicates that the two well-known responses to warming climates are linked. We believe that this finding helps us understand the complex consequences of climate change for biodiversity.

As always, this work was a collaboration with many great coauthors, and I am particularly happy that this work has finally been published, as it took me almost 4 years to get it out as the second paper from my phenology project. I still clearly remember the day in 2009 when Tim, one of our coauthors, visited Cambridge to give a talk on phenological changes. I had been working on the modelling of bird population counts, and after his talk, Bill, Tim and I discussed the potential application of the modelling approach to phenological data. In 2010, we published our first paper using records from the UK Phenology Network. This paper was more or less a methodological paper, but produced estimates of changes in first flowering dates for 405 British plant species. So it was only natural that we then wanted to do something using these estimates.

Given that we can understand both phenological changes and range shifts within the same framework, i.e., they are both a consequence of climatic niche conservatism (tendency for species to maintain their climatic niche over time), it seemed logical for us to hypothesise that these two responses are linked in a complementary manner. Luckily (and as a positive surprise for me), we (I mean, Bill) could easily find data on historical range shifts for most of the species, based on the Atlas of the British & Irish Flora, and processed by Doxford and Freckleton (2012).

These data were key for this second paper, as it was essential that we had these historical data on both phenology and the distribution of many species if we were to test our hypothesis—that there is a link between plants’ spatial and temporal responses to climate change. So, needless to say, this study would not have been possible without the long history of botanical studies and a wealth of citizen science projects in the UK.

We admit that the detected link was relatively weak, but believe that the main novelty of this paper lies in showing the potential link between the two-well known species responses to climate change. So we are very keen to test this link in other taxa and systems. I want to end this blog entry with a special thanks to the countless people who have contributed to the UK Phenology Network and the Atlas of the British & Irish Flora, as well as the Woodland Trust and NBN Gateway for providing the data.