REN R464 Lecture Notes - Lecture 9: Urban Species, Habitat Destruction, Biological Dispersal
29 Sep 2016
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Midterm: short answer, definitions, short problems (paragraph, 10 sentences or less is the longest thing he will ask of us no essay questions) Rare species are those most at risk from extinction. Gaston (1994) recommends defining rare as the 25% of species with low abundance estimates / frequency distribution. Again, this is a relative definition of rarity. Defined only on rank percentage of rares does not change if there are shifts in abundance. I. e. always have 25% rare species regardless of abundance! When you do this you are basically basing rares only on rank. The main point: whether continuous or discontinuous, the choice of cutoff points to define rare species is subjective: types of rarity models. Rabinowitz (1981) adds also habitat breadth/specificity to definition. Combination of range, abundance and habitat breadth/specificity results in 7 types/forms of rarity . The diagram above with the blue green and white.
