I use ecological niche models and species distribution models fairly extensively in my research - both my thesis work and side projects. For some time now my advisor has been involved in projects that link these types of models with population projection models, so when I was thinking about researching the patterns and processes of the invasion of Glossy buckthorn, it made sense to me that I would employ similar techniques. Additionally, I have only found a dozen or so unique presence records for Glossy buckthorn here on Long Island, so I thought it may be good do a SDM focused just on the island here. I haven't completed this part of my project, so don't get excited, I don't have any results to share with you yet. Anyhow, I've spent a fair bit of time gathering more occurrence locations from numerous public lands (parks and what not) in Nassau and Suffolk County, and had been thinking that carrying out an SDM would be pretty straight forward.
SIDE BAR: Looking for invasive species is a bit funny for me. When I go to a new location that I think is likely to have buckthorn, I'm giddy with anticipation. I'm excited when I find it and disappointed when I don't. Now, objectively speaking, if buckthorn is in fact having a strong negative effect on native ecosystems (most likely the case in my New Hampshire populations), then shouldn't I be happy when I don't find it? Yeah, it's complicated I guess...
Ok, back to modeling, and how spending time in the field has affected my thinking. One thing I tend to think about often when in the field is how Glossy buckthorn got to that particular spot? Where is the nearest, next-oldest, population? Glossy buckthorn seeds can be dispersed by any one of the many bird species that eat its fruit, but not too far. The fruit has a laxative effect (on humans too), so birds don't hold it, or the seeds, for long. Because nearly all of my field sites are embedded in suburban areas, they all have at least some length of border shared with someones backyard. At my Long Island sites, I can see backyards from many of my plots. Initially I hadn't thought much of this, but while visiting my uncle and his family in New Jersey a while I back, I noticed that there in the unmaintained garden next to the patio there was a Glossy buckthorn tree. Me - "Uncle Joe, did you plant that tree?" Uncle Joe - "Oh no, that came with the house." So there you have it, people in the suburbs may be inclined to plant this tree in there backyard.
What are the implications of this on my models and how I use them? I'm not sure yet. On the one hand, it makes me think of possible uses of high-res remote sensing and how it may be used to determine what types of plants are growing in urban and suburban yards. This technology and its applications are improving rapidly, and we are getting to the point that identification of individual species from satellite imagery may be possible. (Yeah, that's crazy!) On the other hand, can I use the results of my distribution models to identify distances between populations if plants in your neighbors backyard are actually the source for my populations? I'm not sure, and will definitely be giving this more thought as the project progresses in the near future.