Brood II cicadas: a long time to wait for a lesson in ecology

Many emotive summaries have been scattered through the news regarding the coming of the periodical cicadas in Northern America [1].  This year welcomes the emergence of the Brood II cicada, whose parents emerged during the Clinton years.  Whilst this phenomenon seems abstract to us here in Australia, it is a noisy (listen here [2]) reality for those in the States, which not only pricked my biological interest but also got me thinking about how we study an organism whose lifecycle and population dynamics fluctuate over such long time periods.

There are seven species of ‘Periodical cicadas’, all within the Magicicada genus (Figure 1.). They are divided depending on the amount of time their nymphs spend below ground feeding on xylem sucked from tree roots: those that spend 17 years (three species – to which the Brood II set of whom are emerging now belong), and those that spend a shorter 13 years underground (4 species).  Within this, there are subsequent divisions into broods (of which there are 15) dictated by the years in which they emerge, and morphologically distinct ‘forms’ (of which there are 3) that are synonymous across species.  Confused yet?  The New York Times has made a beautiful feature where you can explore this structure interactively [3].   Regardless of the species debates that rage about whether morphotypes are distinct species, or how 17-year and 13-year species pairs are evolutionarily connected (but this is a very interesting angle that you can read more into here [4]) what strikes me is this: imagine having to wait 17 years for your study species to even APPEAR, and then have only a few weeks to study them!

Figure1

When budgets and funding revolve within a 3-year turn-style, and the contracts of new scientists are revoked if performance measures are not satisfied within 5 years, how do we tackle ecological questions that span long intervals?  The modern focus on more instantaneous ecological study makes a lot of sense in this scenario (e.g. Molecular Ecology), and whilst it is by no means invaluable, its popularity and productivity may be, in part, a product of its quicker turn-around and independence of direct observation (i.e. having to actually sit and watch your organism).  A single sampling bout to infer an evolutionary history, a short drive along the highway to collect the information that will reveal processes that occur over millennia.  Whilst the lab work is long and hard, the technology grows by the second and outsourcing to offshore laboratories means much of the wet-work can be done whilst you continue to write or analyse.  These studies are telling us valuable things about the populations they target but they do not replace long-term organism-centered and on site ecological enquiry.

So what can we do to maintain long data sets in an era focussed on quick turn-around?  In a seminar given by Australian Marine Ecologist Prof. Tony Underwood at our school in 2010, we were given a suggestion.  Prof. Underwood has been collecting data on the abundance of rocky-shore snails for over 50 years (for an example of the variance he found in just a three year interval see [5] & Figure 2.).  Come rain or shine, funded or not, he would continue to return to the same sites, every year, to count these cute but uncharismatic crawlers with inspiration bred of the knowledge that such long-term data sets are both incredibly valuable and seldom collected (especially for his chosen focal organisms).

Figure2

For those that study charismatic animals like the Lynx, such a data set may not seem so hard to come by as many people are interested in the long-term viability of populations of the species (e.g. the Hudson Bay Canadian Lynx and Snowshoe Hare dataset spans over a century [6] (Figure 3.)), though this is still a rarity even amongst the more ‘charismatic’ mega-fauna.  For those who dedicate their scientific lives to the small, or spineless or the oft-unnoticed, a labour of love such as Underwood’s may be the only way of maintaining long-term datasets.  Prof. Underwood urged the young scientists in the room to constantly remind themselves of their passion and their interest in ecology, and to always remember that these factors should drive their efforts, as financial drivers will be fickle and fleeting and most likely not operate at complementary temporal scales.  If we want this kind of information about long-term fluctuations in populations we are probably going to have to go out and monitor them ourselves, with little more support than our knowledge that such data is invaluable.

Figure3

Another option that the chirping of the Brood II cicadas has heralded is the powerful role ‘citizen science’ can play in capitalising on temporally short biological phenomenon, or in building long-term and spatially broad datasets.  ‘Citizen science’ has been employed in a wide variety of fields – my favourites include the Portable Antiquities Scheme in British Archaeology used to allow citizens who discover finds to report and database them for further archaeological investigation [7] and the ‘Birds in Backyards’ scheme of the Australian Museum used to monitor seasonal fluctuations in urban bird populations [8].  In the Brood II cicadas, the program is being expanded and made more accessible via online databases and interactive websites, with live feeds that let people not only report sightings but also monitor emergence at a national scale in real-time [9] (Figure 4.).  By educating and inspiring the public to the ecological interest and importance of invertebrates we can help inform them about the AMAZING ecological and biological adaptations of these species (rather than the annoying sound, disgusting invasion of bugs, or inconvenient scatterings of crunchy expired adults) but also inspire their belief in ecology by involving them directly.

Figure4

So, fellow ecologists, if you chose the occupation for the same reasons I did remind yourself of them from time to time.  I did not become an ecologist for the glamour (Figure 5.), or the prestige, or the money, but for the opportunity to spend my days outside, wandering around, watching the world around me in an attempt to understand it for myself and inspire an understanding in others.

Figure5

broodIIcicada_mine

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1. For example in the Washington Post (accessible here http://www.washingtonpost.com/local/brooding-among-the-cicadas-/2013/05/19/74ac47c4-befd-11e2-9b09-1638acc3942e_story.html) or NBC (accessible here http://www.nbcnews.com/video/nightly-news/51922691/#51922691)

2. Online accessible recordings of Periodical Cicadas accessible here http://www.insectsingers.com

3. Zimmer C. ’17 Years to Hatch an Invasion’, New York Times accessible at http://www.nytimes.com/2013/05/14/science/marvels-and-a-few-mysteries-in-cicadas-17-years.html

4. Berlocher S.H. 2013 ‘Regularities and irregularities in periodical cicada evolution’, PNAS 110:17,  accessible at http://www.pnas.org.ezproxy.library.uq.edu.au/content/110/17/6620.full

5. Underwood A.J. & Chapman M.G. (2000) ‘Variation in abundances of intertidal populations: consequences of extreme environment’, Hydrobiologia, 426 25-36, accessible at http://link.springer.com/content/pdf/10.1023%2FA%3A1003995218016.pdf

6. For a summary of some of the ecological ideas behind the Canadian Lynx observations see Krebs C.J. et al. (2001) ‘What drives the 10-year cycle of Snowshoe Hares?’ Bioscience 51:1 25-35 accessible at http://bio.fsu.edu/~james/krebs.pdf

7. The Portable Antiquities Scheme website shows how citizens can report their finds as well as reports on successful stories of the scheme.  You can visit them at http://finds.org.uk

8. Birds in Backyards lets citizen scientists report ongoing and seasonal bird sightings, as well as access information on local birds and identify birds using an easy-to-use interactive identification key.  You can see their work at http://www.birdsinbackyards.net

9. See how citizen science is being put into action in the U.S. Brood II cicada emergence with Radiolab at http://project.wnyc.org/cicadas/ or Magicada.org at http://www.magicicada.org/magicicada_ii.php

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