DOI: 10.5061/dryad.8t2v0
title: Data from: Impacts of environmental variability on desiccation rate, plastic responses and population dynamics of Glossina pallidipes

description: Physiological responses to transient conditions may result in costly
 responses with little fitness benefits, and therefore, a trade-off must
 exist between the speed of response and the duration of exposure to new
 conditions. Here, using the puparia of an important insect disease vector,
 Glossina pallidipes, we examine this potential trade-off using a novel
 combination of an experimental approach and a population dynamics model.
 Specifically, we explore and dissect the interactions between plastic
 physiological responses, treatment-duration and -intensity using an
 experimental approach. We then integrate these experimental results from
 organismal water-balance data and their plastic responses into a
 population dynamics model to examine the potential relative fitness
 effects of simulated transient weather conditions on population growth
 rates. The results show evidence for the predicted trade-off for
 plasticity of water loss rate (WLR) and the duration of new environmental
 conditions. When altered environmental conditions lasted for longer
 durations, physiological responses could match the new environmental
 conditions, and this resulted in a lower WLR and lower rates of population
 decline. At shorter time-scales however, a mismatch between acclimation
 duration and physiological responses was reflected by reduced overall
 population growth rates. This may indicate a potential fitness cost due to
 insufficient time for physiological adjustments to take place. The
 outcomes of this work therefore suggest plastic water balance responses
 have both costs and benefits, and these depend on the time-scale and
 magnitude of variation in environmental conditions. These results are
 significant for understanding the evolution of plastic physiological
 responses and changes in population abundance in the context of
 environmental variability.
description: Environmental
 variability effects on GlossinaGlossina pallidipes
 (Diptera, Glossinidae) puparia were subjected to simulated weather front
 scenarios (also referred to as acclimations), involving varying humidity
 and temperature for different durations. We determined water loss rates
 (WLR, in µg H2O h-1) individually using conventional gravimetric methods
 by recording body mass on an electronic microbalance at two experimental
 time points after a 3-day acclimation or after a 5-day acclimation.
 Individual puparia were placed on cotton wool in separate, open, numbered
 0.6 ml micro centrifuge (eppendorf) tubes randomly assigned into
 replicated plastic 100ml airtight vials, (volume = 166 cm3). Each vial
 contained six tubes (N = 6 puparia per vial), and each vial was replicated
 five times to give a total sample size of N = 30 puparia per treatment.
 Care was taken to ensure that all treatment groups were handled for the
 same duration during transfer from the climate chamber to the vials (~ 7
 min per group), and spent a similar amount of time outside of the vials
 whilst being weighed (~ 15 min per group). Relative humidity and
 temperature were recorded during treatments using Thermochron iButtons
 (DS1402D-DR8, Philippines; sampling rate = 10 min, ± 1 °C temperature
 accuracy, ± 0.5 % r.h. accuracy). Hygrostatic solutions were used to
 control the different humidities. Saturated solutions of magnesium
 chloride (MgCl2.6H2O), magnesium nitrate (Mg(NO3)2.6H2O) and sodium
 chloride (NaCl) were employed to correspond to humidities of 33 %, 55 %
 and 76 % r.h., respectively, and the same batch of each solution was used
 across all 5 vials to ensure similar conditions between replicates.
 Filtered, doubly-distilled water was always used as the solvent for
 production of saturated salt solutions. Silica gel was used for completely
 desiccating conditions (&lt;5 %, referred to as 0 % r.h.) and
 double-distilled water for fully hydrated air: 95 – 100 % (referred to as
 99 % r.h.). To test the effect of acclimation duration on WLR, we measured
 WLR over a five-day period at 25 °C, 76 % r.h. after exposure to
 acclimations (combinations of temperature and r.h.) lasting for different
 durations. The first experimental group was subjected to acclimation
 conditions for three days (15 temperature and r.h. combinations, N = 30
 individuals per combination), while the second experimental group was
 subjected to acclimation conditions for five days (15 temperature and r.h.
 combinations, N = 30 individuals per combination). Acclimations included a
 combination of three temperatures (21, 25 and 29 °C) and five relative
 humidities (0, 33, 55, 76 and 99 % r.h.) resulting in a total N = 15
 acclimations per three and five day exposure. After we measured WLR, we
 scored the time to eclosion (in days) and survival (%) at 25 °C, 76 % r.h.
 Given that the conditions for optimal population growth rates are already
 well established for constant stable conditions we compare all our results
 to this baseline condition (referred to as optimal rearing conditions
 throughout) as a relative improvement or decline for each treatment. The
 simulated experimental changes in thermal and hygric conditions allowed us
 to explore the impacts of plastic responses on population growth rates and
 relative changes thereof. Population growth rates are calculated as a
 function of the duration of the puparial life-stage (pupal eclosion rate)
 and pupal survival. The Euler-Lotka equation has been used in several
 studies of population dynamics, relating the growth rate of a population
 (r) to age-dependent fecundity and mortality. The puparial life-stage
 lasts for a duration τa (in days) during which time the daily survivorship
 is described by σa. In our treatments we estimated τa under a range of
 environmental conditions varying in both temperature and humidity and use
 the estimated fraction survival minus the 1 % constant predation rate for
 tsetse puparia as an estimate of σa.JEB-2013-00543.R1
 DATA.xls