Title: Joint effects of global warming and pollutants on damselflies
Other Titles: Gecombineerde effecten van klimaatsopwarming en polluenten op waterjuffers
Authors: Dinh Van, Khuong; R0236246
Issue Date: 14-Oct-2014
Abstract: Global warming and contamination are two major threats to freshwater biodiversity, which, moreover, have the potential to interact synergistically. To persist in a warming world, organisms have to either adapt in situ to the temperature increase or shift their range to track their moving climate niche. However, we poorly know the roles of thermal adaptation, life history and the rapid evolution at an expanding range front in shaping the vulnerability to contaminants under global warming. In this study, I investigated the separate and joint effects of global warming andcontaminant stress on damselflies focusing on two aspects: (i) a 4°C temperature increase and how this is further modulated by thermal and latitudinal adaptation and (ii) a poleward range expansion and associated life history evolution.In chapters I-IV, I describe the results ofcommon garden warming experiments where larvae of replicated populations from low, central and high latitudes of Ischnura elegans were reared at 20°C and at 24°C corresponding to the mean summer water temperatures in ponds in southern Sweden and Southern France, respectively. Importantly, the 4°C temperature difference also corresponds to the predicted temperature increase by 2100 under IPCC scenario A1FI. This space-for-time substitution approach allows testing whether local thermal adaptation mayshape the future susceptibility of contaminants under global warming athigher latitudes. I found a strong latitude-specific vulnerability to contaminants for both the metal zinc and the pesticide chlorpyrifos. Indeed, high-latitude populations showed a stronger reduction in escape swimming speed when exposed to zinc, indicating that the metal contaminationmay make them more vulnerable to predation. Importantly, at high temperature high-latitude populations were also more vulnerable to zinc in term of survival and activity levels while these effects were not present or much less pronounced in low-latitude populations, indicating that gradual thermal adaptation may mitigate the future effects of metals on high-latitude populations under global warming. In contrast, the low-latitude populations showed a stronger growth reduction at high chlorpyrifos concentrations and high temperature. This result suggests that the faster life history, more than three generations per year, of low-latitude populations makes them more vulnerable to organophosphate pesticides like chlorpyrifos. At higher temperature, the negative effects of chlorpyrifos were also stronger for predator behaviors while these effects were similar for antipredator behaviours at both temperatures. These results highlight the complexity of contaminant effects on predator-prey interactionsbeing differentially temperature-dependent pending on the trophic level.In chapters V and VI, I tested for the role of the evolution ofa faster life history and a higher investment in flight morphology during range expansion in driving the vulnerability to two widespread pesticides, the organophosphate chlorpyrifos and the pyrethroid esfenvalerate,in the edge populations of the damselfly Coenagrion scitulum, a currently poleward moving damselfly. I did this by comparing the vulnerability of replicated core and edge populations reared under common garden conditions from the egg stage. Besides testing for effects of the pesticides during the larval stage I was particularly interested in carry-over effects in the adult stage in traits related to range expansion, namely flight ability and immune function. I found evidence for the faster life history of edge populations in term of growth rate and development time while the higher investment in flight-related traits was only present at high density in the absence of pesticides. Nevertheless, the edge populations showed a consistently higher vulnerability to pesticides both during the exposure period and with regard to carry-over effects across metamorphosis; the mortality rate was higher in esfenvalerate-exposed edge larvae and the chlorpyrifos-induced reductions in flight muscle mass and phenoloxidase activity were only present in the edge animals.The here presented results provide a comprehensive picture on the vulnerability of damselflies both at the larval and adult stage to different types of contaminants under global warming. I, for the first time, documented that thermal adaptation may mitigate the effects of metals such as zinc at higher latitude by applying a space-for-time substitution approach. I also showed that the faster life history of the multivoltine animals at low latitudes may make them more vulnerable to pesticides. This researchis also the first one that studied and documented that rapid range expansion may increase the vulnerability of edge populations to pesticides. These results emphasize the need for spatially explicit risk assessment and associated conservation tools. The documented higher mortality and the carry-over effects from larval exposure on flight- and immune-relatedtraits indicate that contamination may slow down the future range expansion in poleward moving species.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Ecology, Evolution and Biodiversity Conservation Section

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