To explore possible determinants of PPSR, we tested four statistical models following : (i) a null model, where prey BW is common among all predators (i.e. logten(prey BW) = ?), (ii) a taxonomic model, where prey BW is species-specific (i.e. logten(prey BW) = ? + ? ? (predator species identity)), (iii) an allometric model, where prey BW is size-dependent (i.e. log10(prey BW) = ? + ? ? log10(predator BW)), and (iv) a combined model (i.e. log10(prey BW) = ? + ?1 ? (predator species identity) + ?2 ? log10(predator BW) + ?step 3 ? (predator species identity) ? log10(predator BW)). Here, BW represented individual weights for individual-link PPSR, whereas the mean measurements were used for the other definitions. Calculating the Akaike information criterion (AIC) by ordinary least-squares regression, we determined the best statistical model for each definition. All analyses (including calculations of parameters ? and ?) were conducted using the software R .
step three. Abilities
For all the definitions, PPMR generally ranged between 0 and 1 on a log scale, i.e. the predators and prey had similar body sizes of the same order of magnitude (figure 2a). For species-averaged definition, K. deyrolli had larger prey BW than the other species (p < 0.05, figure 2b). For link-averaged definition, A. japonicus and L. japonensis increased their prey size as they grew, whereas K. deyrolli did not (figure 2c). For individual-link definition, all species showed increases in prey BW during growth, but the regression slope of K. deyrolli was significantly lower than the other species (figure 2d). These results indicate that the effects of predator size and species identity were scale-dependent. We plotted contour lines of PPMR (grey lines) in each panel of figure 2b–d. By comparing these contours with the regressions of predator versus prey BW, we can infer how PPMR during growth (also see the electronic supplementary material, S4 for direct comparison of PPMR versus predator size). We found that K. deyrolli clearly increased individual-link PPMR as it grew (i.e. the regression slope was significantly less than 1), whereas the other two predators had slightly R during growth (i.e. the regression slope is greater than 1) (figure 2d). The AIC values showed that species-averaged prey BW was best explained by the allometric model, whereas link-averaged and individual-link prey BWs were best explained by the combined model (table 1; see the electronic supplementary material, S5 for model selection to explain PPMR).
Figure 2. (a) The three definitions of PPMR are shown in box plots. The thick and dashed lines represent the median and mean values, respectively. (b) Species-averaged prey body weight (BW), (c) link-averaged prey BW, and (d) individual-link prey BW are plotted against predator BW on a log–log scale. The open circles with dotted regression, grey squares with dashed regression and black diamonds with solid regression represent A. japonicus, K. deyrolli and L. japonensis, respectively. The grey lines represent contours of PPMR on a log scale. Only significant regressions were shown in (c) and (d). Different superscripts indicate significant differences in regression slope or intercept between species (p < 0.05), and ‘p' columns indicate the significance of the regressions.
To the knowledge, this is actually the first had written make an effort to formally characterize PPSR when predators normally eat sufferer larger than themselves. The content revealed that pÅ™Ãklady profilÅ¯ eharmony PPSR varied which have predator proportions and variety name, although the utilization of the averaged designs perplexed such consequences (profile 2b–d and desk step one). It measure dependency is in line with that inside seafood tummy content datasets . Somewhat, yet not, our very own show revealed that species averaging builds a deceitful picture of real serving dating while it will not connect with PPMR (figure 2a), whereas earlier in the day knowledge managed this matter in accordance with the meaning dependence away from PPMR [eight,fourteen,15]. Hence, it is very important take a look at variability and the determinants regarding PPSR from the individual level.
Significantly, PPSR would be laid out in almost any means with respect to the definition from dimensions [7,ten,14,15]. Right here, i noticed around three significance following [7,10,14]: (i) ‘species-averaged PPSR’ which spends indicate looks weights (BW) from predator and you may target variety, (ii) ‘link-averaged PPSR’ and that spends indicate BW out-of predators and you may victim some one that actually eat or try ate from the connecting kinds, and you will (iii) ‘individual-hook up PPSR’ hence uses predator and you may victim private BW for every google search enjoy. Remember that the last signifies the real giving matchmaking. We opposed target BW certainly one of predators that with a standardized major axis (SMA) way to likewise thought variations in the two axes . For species-averaged PPSR, we simply put you to definitely-means ANOVA while the SMA wasn’t relevant. It will be useful to is individual identity out-of predators since the a random factor to get rid of a possible pseudo-replication issue , yet , this is maybe not possible while the predators we examined moult and you will lost decorate scratches to possess personal personality; not, this will maybe not connect with our major results. We including evaluated predator–prey bulk percentages (PPMRs) sizes-dependent restaurants-internet knowledge, into three significance (comprehend the digital second matter, S3).