Geoscience Reference
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2. Prey Species Identity
It is reasonable to expect that PPMR is critically affected by prey species
identity (see
Henri and vanVeen, 2011
for host-parasitoid interactions). In
general, predation avoidance is more important for prey than predation
success is for predators, which is known as the life-dinner principle
(
Dawkins and Krebs, 1979
). The evolution of defence by prey may, therefore,
more effectively influence feeding relationships compared with the evolution
of offence tactics by predators. To evaluate the possible effect of prey species
identity on PPMR, we analysed the data from 13 sampling sites, where
multiple prey species were identified to at least the genus level (i.e. sites 01,
02, 04, 05, 06, 09, 10, 14, 16, 17, 18, 19, and 21). In the analysis, we used prey
species identity as an independent variable and included predator individual
identity as a random effect. Unidentified prey categories were excluded from
the analysis. The analysis showed that PPMR is highly variable among prey
species, with significant interspecific differences being found at 12 sites,
except for site 01 (
Figure 6
). It should be noted here that we detected
predator species specificity of PPMR in just 8 of the 11 sites (
Figure 4
).
Therefore, prey species identity may be more crucial for PPMR. Further
study is required to determine the predator-prey species-pair specificity of
PPMR, by focusing on prey species identity in the gut contents of predators
(see Section
V.B
).
3. Evolutionary History
What determines species identity of predator and prey? One proposal is that
feeding relationships may reflect the evolutionary history of food webs.
Bersier and Kehrli (2008)
supported this idea by showing that phylogeny
and trophic relationships are closely linked in a size-structured food web.
With the same framework,
Rohr et al. (2010)
predicted that the structure of
food webs is explained by species-specific latent parameters, as well as by
body size, which they suggested were size-unrelated traits determining pred-
ator foraging and prey vulnerability (i.e. species identity). Although these
studies are formed on the species-based approach without intraspecific var-
iations, it is noteworthy that the incorporation of the evolutionary perspec-
tives of food webs (
Meli´n et al., 2011
) might enhance our understanding of
prey-predator feeding relationships, and thus possibly PPMR.
We examined the phylogenetic relationships of individual-predator PPMR
to identify the possible effect of phylogeny on PPMR. Following
Nelson
(2006)
, we assigned phylogenetic ranks, ranging from 1 to 16, to all available
orders of fish predators. Note that the dataset includes one species of squid
predator, which we treat as the most ancestral order, with a ranking of 1.
