title: The importance of relative humidity and trophic resources in governing ecological niche of the invasive carabid beetle Merizodus soledadinus in the Kerguelen archipelago.
abstract: Comprehensive studies to identify species-specific drivers of survival to environmental stress, reproduction, growth, and recruitment are vital to gaining a better understanding of the main ecological factors shaping species habitat distribution and dispersal routes. The present study performed a field-based assessment of habitat distribution in the invasive carabid beetle Merizodus soledadinus for the Kerguelen archipelago. The results emphasised humid habitats as a key element of the insect's realised niche. In addition, insects faced food and water stress during dispersal events. We evaluated quantitatively how water availability and trophic resources governed the spatial distribution of this invasive predatory insect at Îles Kerguelen. Food and water stress survival durations [in 100%, 70%, and 30% relative humidity (RH) conditions] and changes in a set of primary metabolic compounds (metabolomics) were determined. Adult M. soledadinus supplied with water ad libitum were highly tolerant to prolonged starvation (LT50=51.7±6.2d). However, food-deprived insect survival decreased rapidly in moderate (70% RH, LT50=30.37±1.39h) and low (30% RH, LT50=13.03±0.48h) RH conditions. Consistently, body water content decreased rapidly in insects exposed to 70% and 30% RH. Metabolic variation evidenced the effects of food deprivation in control insects (exposed to 100% RH), which exhibited a progressive decline of most glycolytic sugars and tricarboxylic acid cycle intermediates. Most metabolite levels were elevated levels during the first few hours of exposure to 30% and 70% RH. Augmented alanine and lactate levels suggested a shift to anaerobic metabolism. Simultaneously, peaks in threonine and glycolytic sugars pointed to metabolic disruption and a progressive physiological breakdown in dehydrating individuals. Overall, the results of our study indicate that the geographic distribution of M. soledadinus populations is highly dependent on habitat RH and water accessibility.
authors.affiliation: Université de Rennes 1, UMR 6553 EcoBio CNRS, 263 Avenue du G(al) Leclerc, 35042 Rennes Cedex, France.
authors.forename: Tiphaine
authors.initials: T
authors.lastname: Ouisse
authors.affiliation: Ghent University, Department of Biology, Terrestrial Ecology Unit, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium.
authors.forename: Dries
authors.initials: D
authors.lastname: Bonte
authors.affiliation: Université de Rennes 1, UMR 6553 EcoBio CNRS, 263 Avenue du G(al) Leclerc, 35042 Rennes Cedex, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Lebouvier
authors.affiliation: Ghent University, Department of Biology, Terrestrial Ecology Unit, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium; Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium.
authors.forename: Frederik
authors.initials: F
authors.lastname: Hendrickx
authors.affiliation: Université de Rennes 1, UMR 6553 EcoBio CNRS, 263 Avenue du G(al) Leclerc, 35042 Rennes Cedex, France. Electronic address: david.renault@univ-rennes1.fr.
authors.forename: David
authors.initials: D
authors.lastname: Renault
mesh_terms: D063147:Animal Distribution; D000818:Animals; D000864:Antarctic Regions; D001517:Coleoptera / Q000502:physiology*; D003890:Desiccation; D005260:Female; D005508:Food Deprivation; D006813:Humidity; D058865:Introduced Species; D062312:Islands; D008136:Longevity; D008297:Male
keywords: Biological invasions; Body water; Metabolomics; Relative humidity; Starvation; Vapour pressure deficit