Re: [ECOLOG-L] Similarity index
Hi Rajasri, Sorry for coming to this late. Is your concern that in the case of small patches you've sampled completely, but in the case of large patches, some species may have gone undetected? If that's the case, using Chao's indices might be a good option. They try to take account of unseen species. The paper is by Chao et al. 2005 in Ecology Letters. Here's a link: http://chao.stat.nthu.edu.tw/paper/2005_EcologyLetters_8_P148.pdf This might not be helpful, in particular you'll need species abundances or replication through time. Also, I'm not sure what the uniform area concept is, so I just took a guess. Hope it's helpful. Best of luck, Andy On Mon, Jun 13, 2011 at 10:23 PM, Rajasri Ray rb...@hotmail.com wrote: Hello, I am trying to compare species composition among different patches which vary in their sizes to a great extent.I am planning to compute Jaccard's similarity index for this. For species enumeration, in some patches I have documented presence of all members (due to very small size of the patch ~ 80 - 500 sq. m).There is problem to apply uniform area concept for species composition. I would like to know whether Jaccard's is suitable for that kind of comparison. Thanks Rajasri
[ECOLOG-L] Similarity index
Hello, I am trying to compare species composition among different patches which vary in their sizes to a great extent.I am planning to compute Jaccard's similarity index for this. For species enumeration, in some patches I have documented presence of all members (due to very small size of the patch ~ 80 - 500 sq. m).There is problem to apply uniform area concept for species composition. I would like to know whether Jaccard's is suitable for that kind of comparison. Thanks Rajasri
Re: [ECOLOG-L] Similarity index
Just try it and you will see. You may get a lot of criticism from people who either never used or would never use these indices, but I am sure that it will help you to analyze your data. You don't have to publish it, but you will get a better insight into your data. The size is another hot potato in your project. You touched the question of minimal area that is another sensitive problem in vegetation sampling. Are your patches large enough to get the majority of species in them? You will get some random noise, if your areas are too large, but skewed results, if they are too small. It depends on the vegetation types you are working with. Adolf Ceska P.S. I prefer Sorensen's similarity index. -Original Message- From: Ecological Society of America: grants, jobs, news [mailto:ECOLOG-L@LISTSERV.UMD.EDU] On Behalf Of Rajasri Ray Sent: June-13-11 10:23 PM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: [ECOLOG-L] Similarity index Hello, I am trying to compare species composition among different patches which vary in their sizes to a great extent.I am planning to compute Jaccard's similarity index for this. For species enumeration, in some patches I have documented presence of all members (due to very small size of the patch ~ 80 - 500 sq. m).There is problem to apply uniform area concept for species composition. I would like to know whether Jaccard's is suitable for that kind of comparison. Thanks Rajasri
