Jake's list takes a few years to get going as it included the odd butterfly record a few years before he started regularly trapping. The diversity may be lower in the urban garden, but the trend looks pretty much the same to me. I'm more impressed that my garden is pretty much keeping pace with Barry's though, in spite of his proximity to Gower and the fact that I simply don't get migrants!
I guess it should be possible to make a prediction of what your list might be in x years time. It would be even more interesting to carry out a detailed analysis from a number of sites, incorporating trapping effort. I've often thought we should have sufficient data now to develop a model to identify a sites significance based on a limited sample. Anyone know if this has been attempted already?
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ReplyDeleteI'll add in some more long term site data sets and see what happens. There are of course lots of variables to consider: habitat, altitude, latitude and whether the recorder does micros.
ReplyDeleteIt would also be interesting to look at the number of species in common across different gardens, and the number which are unique. Maybe a job for the winter!
ReplyDeleteI think my curve would be somewhere between Dave/Barry's and Jake's, which reflects the garden being a bit less urban than Jake's but further from good habitats than Dave/Barry's.
Just a further question on this thread. Do folk think it would be possible to use diversity of moth species as a proxy for the wider biodiversity of a site, i.e. for other inverts/plants etc? Intuitively it seems likely that such a rule might hold true, but I wonder if there is any evidence for it? Are there any sites where there is good moth data that could be correlated against other species groups to check? If that does work it may be possible to make judgements about biodiversity value based on relatively limited data gathering??? Perhaps there's an Atropos article in here somewhere?
ReplyDeleteIt will be interesting to see what the numbers for my home trap show given that it is in a less urban setting than most - by Sept I should have 2 full years data. I think I picked up around 260 new species in 2011 and my feeling is that I have seen far fewer garden firsts this year, which would buck the trend a bit, although having said that 2011 was exceptional.
As long as all of the moth species are breeding on the site then there is no doubt that it would correlation between them and the plants and other invertebrates. The problem with moth traps is that they pull moths in from the surrounding countryside, so not everything you catch is a local resident species.
ReplyDeleteThis is certainly true for my trap, Dave. My garden is small and backs onto a field, which is semi improved grassland, which is fairly species rich and the proof that many of my moths came from there occurred when from years of being hardly grazed at all, four horses were suddenly introduced, leading to gross overgrazing and in winter, the churning of the surface to a complete mud bath that that takes half of the following growing season to partially recover. As a result of this, my catch sizes instantly dropped by at least 30%, with a significant drop in the number of species caught. This sudden decline in moth and species numbers coincided exactly with the trashing of the vegetation in the field, proving that many of the species entering my trap were coming from the field rather than my garden or from other nearby habitats. The field remains overgrazed, continuing the effect on my moth catches.
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