International Scholarly Research Notices / 2014 / Article / Tab 3 / Research Article
Natural Prey Preferences and Spatial Variability of Predation Pressure by Cyphoma gibbosum (Mollusca: Gastropoda) on Octocoral Communities off La Parguera, Puerto Rico Table 3 Ivlev’s prey electivity index for each reef zone for octocoral species harboring snails. Prey electivity
, was estimated whereby
is the proportion of prey species
utilized and
is the proportion of prey species
available.
Inner reefs Occupancy Availability Electivity index Octocoral spp. Spp. utilization B. asbestinum 0 0.000 25 0.019 −1.000 Total rejection G. ventalina 10 0.156 370 0.280 −0.284 Total rejection P. americana 33 0.516 496 0.375 0.158 Prop. abundance P. acerosa 4 0.063 141 0.107 −0.259 Total rejection P. flexuosa 8 0.125 154 0.117 0.033 Prop. abundance P. porosa 8 0.125 101 0.076 0.244 Prop. abundance P. homomalla 1 0.016 34 0.026 −0.238 Total rejection Total 64 1.0 1321 1.0 Mid-shelf reefs Occupancy Availability Electivity index Octocoral spp. Spp. utilization B. asbestinum 5 0.125 58 0.040 0.515 Prop. abundance G. ventalina 9 0.225 470 0.327 0.185 Prop. abundance P. americana 10 0.250 255 0.177 0.171 Prop. abundance P. acerosa 0 0.000 194 0.135 −1.000 Total rejection P. flexuosa 10 0.250 250 0.174 0.179 Prop. abundance P. porosa 3 0.075 182 0.127 −0.257 Total rejection P. homomalla 3 0.075 28 0.019 0.596 Prop. abundance Total 40 1.0 1437 1.0 Shelf-Edge Reefs Occupancy Availability Electivity index Octocoral spp. Spp. utilization B. asbestinum 11 0.105 47 0.059 0.280 Prop. abundance G. ventalina 48 0.457 313 0.393 0.075 Prop. abundance P. americana 18 0.171 76 0.095 0.286 Prop. abundance P. acerosa 2 0.019 62 0.078 0.603 Prop. abundance P. flexuosa 16 0.152 128 0.161 −0.029 Total rejection P. porosa 10 0.095 142 0.178 −0.304 Total rejection P. homomalla 0 0.000 28 0.035 −1.000 Total rejection Total 105 1.0 796 1.0