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. log10(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 three ? (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 3. Overall performance
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.
cuatro. Dialogue
To the knowledge, this is the earliest penned just be sure to formally characterize PPSR when predators can also be eat prey larger than on their own. The data indicated that PPSR ranged with predator size and you will varieties label, while the utilization of the averaged sizes puzzled these types of effects (shape 2b–d and you will table 1). Which measure dependence is in keeping with one into the seafood tummy content datasets https://datingranking.net/cs/her-recenze/. Rather, not, the results indicated that types averaging builds a misleading picture of actual feeding matchmaking although it cannot apply to PPMR (figure 2a), while previous education handled this issue in accordance with the meaning dependency away from PPMR [eight,fourteen,15]. For this reason, it is essential to browse the variability in addition to determinants of PPSR on private height.
Significantly, PPSR might be outlined in different indicates according to definition out-of dimensions [eight,10,14,15]. Here, i experienced three significance pursuing the [seven,ten,14]: (i) ‘species-averaged PPSR’ and therefore spends indicate system loads (BW) of predator and you can prey species, (ii) ‘link-averaged PPSR’ hence uses indicate BW off predators and you may prey anyone that basically eat otherwise are ate by connecting kinds, and you may (iii) ‘individual-hook up PPSR’ and therefore spends predator and you will sufferer personal BW for every single google search knowledge. Observe that the very last means the actual eating relationships. We compared prey BW among predators that with a standard significant axis (SMA) strategy to in addition envision variations in both axes . Having types-averaged PPSR, we simply put one to-way ANOVA as SMA wasn’t appropriate. It could be good for is individual identity from predators while the a random basis to eliminate a potential pseudo-replication thing , yet , this is maybe not feasible because predators we checked out moult and you can destroyed painting scratching getting personal identity; yet not, this will not affect our big conclusions. We along with analyzed predator–victim bulk percentages (PPMRs) in dimensions-centered dinner-websites degree, toward around three significance (understand the digital supplementary point, S3).
