DOI: 10.5061/dryad.8gtht76r8
title: An experimental test of the Growth Rate Hypothesis as a predictive framework for microevolutionary adaptation

description: The growth rate hypothesis (GRH), a central concept of ecological
 stoichiometry, posits that the relative body phosphorus content of an
 organism is positively related to somatic growth rate as protein
 synthesis, which is necessary for growth, requires P-rich rRNA and has
 strong support at the interspecific level. Here, we explore the use of the
 GRH to predict microevolutionary responses in consumer body stoichiometry.
 For this, we subjected zooplankton populations to selection for fast
 population growth (PGR) in P-rich (HPF) and P-poor (LPF) food
 environments. With common garden transplant experiments, we demonstrate
 that in HP populations evolution towards increased PGR was concomitant
 with an increase in relative phosphorus content. In contrast, LP
 populations evolved higher PGR without an increase in relative phosphorus
 content. We conclude that the GRH has the potential to predict
 microevolutionary change, but that its application is contingent on the
 environmental context. Our results highlight the potential of cryptic
 evolution in determining the performance response of populations to
 elemental limitation of their food resources.
description: This study consists of 4 seperate experiments
 1. Evolution experiment: Fourteen replicate populations with
 identical genetic composition, were exposed to culturing conditions that
 selected for fast clonal population growth, seven of the populations
 were allocated to a P-rich (HPF) and the other seven populations to a
 P-poor (LPF) diet. Every 24 hours we transferred 60 haphazardly selected
 individuals and all resting eggs from each population to a new culturing
 flask with a fresh food suspension. After the daily transfer, we counted
 the remaining individuals to calucate population growth rates.
 2. Common garden one: Using the populations from the evolution
 experiment we performed fully reciprocal common garden experiment to test
 for genetic adaptation to selection for fast growth in the two food
 quality treatments. Every 24 hours we transferred 10 haphazardly chosen
 individuals from each experimental unit into a fresh algal suspension. We
 counted the remaining animals to estimate PGR. We preserved the remaining
 individuals to estimate demographic composition. 3.
 Common garden two: Using the populations from the evolution experiment we
 performed large scacle fully reciprocal common garden experiment to
 evaluate the effect of selection history on organismal carbon (C),
 nitrogen (N), and phosphorus (P) content. We determined rotifer C and N
 contents using a FLASH 2000 organic element analyzer (Interscience B.V.,
 Breda, Netherlands), and P content with a QuAAtro segmented flow
 autoanalyzer (Beun de Ronde, Abcoude, Netherlands). For each of these
 analyses we used a sample of 100 individuals with a single parthenogenetic
 egg. 4. Life History
 Experiment in LP Food: Using the populations from the
 evolution experiment conducted a life history experiment in low-P food
 with the populations. During the life table 15-18 individuals from each
 population were monitored every two hours from birth until the production
 of the first juvenile or until confirmed as carrying a sexual
 egg. All raw data is provided please see associated
 analytical code for data processing.