Fish collection and rearing
We established lab populations of guppies from high- and low-predation
populations pairs collected from the Aripo and Quare river drainages in
2012 and 2014, respectively. To maintain the genetic variation of the
original wild-caught fish, we established 20 - 30 unique family lines
for each population (i.e., for each generation a single female from each
family was crossed to a single male from another family) (D. N. Reznick
& Bryga, 1987). We used second-generation lab born fish from these
unique family lines in this study to minimize environmental and maternal
effects. At birth, we split second-generation siblings into rearing
environments with (pred+) or without (pred-) predator chemical cues, and
they remained in these environments until the completion of the
experiment (as in Fischer et al., 2016). We used only mature males in
this study. To maximize the range of genetic variation captured among
focal fish, all males in a given experimental group (i.e. population and
rearing environment) were from distinct families; however, our
split-brood design allowed us to simultaneously leverage genetic
similarity among siblings and control for the effects of genetic
background on developmental responses. Figure 1 provides an overview of
our experimental design and interpretation of comparisons.
All guppies were individually housed in 1.5 liter tanks on a 12:12 hour
light cycle at Colorado State University. Fish were fed a measured food
diet once daily, receiving Tetramin™ tropical fish flake paste and
hatched Artemia cysts on an alternating basis. Prior to tissue
collection for this study, behavioral and hormone data were collected in
an identical manner for all fish and these results are reported
elsewhere (Fischer et al., 2016b). All experimental methods were
approved by the Colorado State University Animal Care and Use Committee
(Approval #12-3818A).