The things we leave behind

Sometimes I wonder what people would be able to deduce about me from looking at my office. If someone came in snooping I’m sure that they would get some understanding of me, even if I was absent, simply by looking at what I leave behind. Of course there are some obvious things. I have what I like to think of as a typical academic’s office, messy, possibly chaotic, a sense of personality, perhaps a sense of busy work. Of course not all academics are like this but there are plenty who are, like one of my corridor neighbours Tim Curran. Another neighbour, John Marris, has an immaculate office with everything in its place but, then, he is the curator of our entomology museum and so being precise and particular comes with the territory. Another neighbour, James Ross, also has a extremely tidy office. He is a regular academic, so no real excuse, and I find entering his office quite daunting. There is certainly some reflection of their offices into how they run the rest of their lives.

Adrian’s office – typical academic?

Turning to my office in more detail, such a snoop might gaze at my desk. At first glance (and at multiple glances really) there are many chaotic piles of paper. Perhaps evidence of a person that can multi-task and perhaps they use chronological filing? There is a pile of documents on new course development administration, another with an attempt to write a children’s story on insect identification, still another of recent papers (on explanatory power in ecology, self-immolation in plants, evolution of sex chromosomes, convergence of lizard morphology on islands and getting DNA from possums), and another with an odd collection of names of potential candidates for the Canterbury Country Under 15 cricket team, Adrian’s postgrad students monthly funding, a design for next year’s research methods course and a document about the appraisal of the local primary school principal. What would my snoop make of these? Perhaps that Adrian spends a lot of time on teaching committees, perhaps has had kids and likes to write, has a wide range of research interests, is involved in cricket coaching, supervises postgrad research, is proactive about getting ready to teach a course 3 months away, and is involved in governance at the local school. All correct. Looking closer they might observe some D and D dice (so a nerd!) and a dinosaur (so a science nerd!). Looking around my room the snoop would see from my posters that I have an interest in movies and Darwin and my books and ‘toys’ would confirm it.

As individuals move through the world they interact with other individuals and other elements of their environment. Every interaction leaves something behind, whether intangible, say a memory, or tangible, say a footprint. Individuals are constantly leaving clues about themselves behind. This is one of the reasons that we are uncomfortable with our new online existence, how it is possible for anyone with the right access to know almost everything about you! Of course, there is something even more personal that you leave behind you everywhere you go – your DNA. We live in a sea of DNA. Every living thing around you has DNA. All of the cells that you are constantly shedding have DNA. The DNA ranges from fully functioning in living cells to various states of decay in nonliving cells. Everything you touch, everywhere you breathe, leaves behind DNA. Most times this is in very low quantities but this can still be detectable. One of my students just found that in a few ml of seawater taken at a local shore that we could detect shark and seahorse species that are swimming about in the area! (More on that at a future time) Because of the presence of this sea of genetic material, DNA is a great potential resource for ecologists and conservationists.

A waxtag, complete with possum bites, saliva and DNA

As ecologists we often deal with animals that are difficult to find or detect. Usually, we want to monitor populations to find out if they are increasing, moving, changing in age structure and so on. For many species this is difficult. They might be nocturnal, or cryptic, or in tough terrain, or small, or dangerous, or – well you get the picture. Being able to detect where individuals have been (even if they have moved on now) is a very useful ability. We have cameras that detect motion, tracking tunnels that record footprints in ink, GPS collars that can be attached to an individual and then followed. These are all useful methods. Here at Lincoln we do a lot of work on possum behaviour. One method for inferring possum presence is to put out waxtags which possums happily bite and leave tooth marks on. We can collect these up and know that at least one possum came past and bit the tag. Sometimes we would like more precision. We want to know how many possums came past and bit the tag. Were they males or females? The bites don’t tell us that kind of information. However, the possums leave more than just the bite marks, they also leave DNA that is present in their saliva.

In a new study by masters student Juan Duenas, with James Ross and Rob Cruickshank, just published in New Zealand Journal of Ecology, it is confirmed that possum DNA can be collected from saliva on waxtags. More impressively, enough microsatellites (highly variable areas of DNA) can be distinguished to identify individuals (a kind of genetic fingerprinting). The DNA doesn’t come easily though as it quickly starts to degrade in the saliva and then on the waxtag itself. The tags were bitten by possums at some point during the night of collection and their DNA was only just good enough, condition-wise, in the morning to actually be decoded. Still, this is a good step forward, we can use the DNA that possums leave behind to find out how many individuals are in an area, where they might have moved into the area from and what the sex ratio might be. This is all information that is very difficult and labour intensive to collect otherwise. The DNA that organisms leave behind is becoming a very powerful tool for understanding the private lives of these individuals. I wonder if my snoop has a DNA kit….

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