Physiological responses to temperature in Merizodus soledadinus (Col., Carabidae), a subpolar carabid beetle invading sub-Antarctic islands

International audienceRecent human activities and rising air temperature have increased the vulnerability of sub-Antarctic islands to alien species. At the Kerguelen Islands, the predaceous ground beetle Merizodus soledadinus is the only invasive insect originating from the southern cold temperate area (native from Patagonia, Tierra del Fuego and Falkland Islands). This austral origin raises the question of the limits of its physiological tolerance and capability to withstand (1) global change and (2) warmer climates of archipelagos where its accidental transportation could be facilitated from the Kerguelen Islands (namely Amsterdam and Saint Paul). Using gas chromatography/mass spectrometry metabolomics, we compared metabotypes of adults exposed to different temperatures (0, 4, 8, 12, 16, 20 °C). All individuals survived after 2 weeks regardless of the temperature they were exposed to. The physiological changes observed were consistent with increased metabolic rate at increased temperatures, without extreme metabotypes that are characteristic of acute stress. First cues of sublethal stress were observed after prolonged exposure to 20 °C, a warm regime unrealistic for such duration in sub-Antarctic Islands. Overall, M. soledadinus’ thermal tolerance exceeded temperatures currently experienced in nature, suggesting that climate warming may boost its invasion by eliciting its activity and broadening habitat suitability in both invaded and still pristine islands. This thermal tolerance may allow survival aboard ships and development in sub-Antarctic islands with conditions warmer than the Kerguelen Islands, such as Amsterdam and St Paul. Stringent biosecurity measures are thus needed to prevent transfer from Kerguelen to these islands. The native range of this predaceous beetle limited to the Falkland Islands and southernmost South America may be partly constrained by factors other than temperature, such as desiccation, predation or competitio

New insights into the ecology of Merizodus soledadinus, a predatory carabid beetle invading the sub-Antarctic Kerguelen Islands

International audienceOur knowledge of the main determinants of invasion success is still incomplete. Among these factors, the effects of biological traits, including fecundity, longevity and dispersal in newly colonised regions, are pivotal. However, while numerous studies have considered ecological and evolutionary impacts of non-native species, their biology often remains understudied. Despite the continuous geographic expansion of Merizodus soledadinus (Coleoptera: Carabidae) at the Kerguelen Islands over recent decades, the main life-history parameters of this species are unknown. We determined adult longevity under controlled conditions, monitored seasonal activity through pitfall trappings, and analysed temporal variations of egg load and body reserves in field-collected individuals. Themedian adult life span (LT50) was 241 days, with maximum longevity of 710 days (N = 500). Females carriedeggs throughout the year (8.94 ± 3.56 eggs per female), and it was not possible to pinpoint any clear egg-layingperiod. Year-round trappings demonstrated continuous activity of adults over seasons, with a peak during the austral summer that may arguably be associated with higher temperatures. Body stores (glycogen and proteins) did not vary significantly through the year, suggesting that adults feed continuously despite different prey availability between summer and winter, possibly via diet shifts. The amount of triglycerides increased at onset of summer, which may be associated with higher summer locomotor activity and/or more intense predation and reproduction

Characterization of the habitats colonized by the alien ground beetle Merizodus soledadinus at the Kerguelen Islands

In the present work, we conducted a field-based study to identify the type of habitats colonized by the alien ground beetle Merizodus soledadinus at the Kerguelen Islands, southern Indian Ocean, and to delineate the spatial dynamics of this species. We used periodic trapping at several coastal habitats on Ile Haute (one of the islands from the Kerguelen archipelago), together with opportunistic active searches at other locations on this subantarctic archipelago. A total of 1081 sites were visited. Our data showed that adult M. soledadinus were mostly found near the tide drift line (372/ 540 obs., i. e., 69 %) in various habitats, including (1) in the foreshore under timber, (2) beneath stones in coastal areas near penguin colonies, and (3) in herbfields and meadows. It was previously assumed that the habitat distribution of this species was restricted to the herbfields of coastal areas, with our inland observations showing that M. soledadinus (265/ 541 obs., i. e. 49 %) occupied areas (1) in the vicinity of cushion-carpets, (2) along rivers and ponds beneath stones or mammal carrion, and (3) in fell-fields that contained plant patches (Azorella selago, Colobanthus kerguelensis, or Lycopodium magellanicum and/or bryophytes). Our study is expected to facilitate the implementation of biosecurity measures to mitigate accidental introduction of M. soledadinus to pristine areas that it has not yet colonized.Caractérisation des habitats colonisés par le coléoptère terrestre allochtone Merizodus soledadinus aux îles Kerguelen. — Dans le présent travail, nous avons conduit une étude de terrain visant à identifier les habitats colonisés par Merizodus soledadinus, un coléoptère terrestre allochtone afin de comprendre sa dynamique spatiale aux îles Kerguelen. Nous avons pratiqué un piégeage régulier dans plusieurs habitats côtiers sur l’île Haute, combiné à des recherches actives et opportunistes de cette espèce dans d’autres sites de cet archipel subantarctique. Au total 1081 sites ont été visités, et nos données ont révélé que les adultes de M. soledadinus se rencontrent très souvent sur la partie supérieure des estrans (372/ 540 obs., i. e. 69 %) (1) sous les laisses de mer et débris de bois jonchant la plage, (2) sous les pierres près des colonies de manchots dans ces zones côtières (3) dans les zones à herbacées et dans les prairies. Même si l’espèce a longtemps été considérée comme cantonnée aux herbages des zones côtières, nous avons relevé sa présence à l’intérieur des îles (265/ 541 obs., i. e. 49 %) (1) au voisinage de plantes en coussinets, (2) au bord des rivières et des mares, sous des pierres ou des déchets animaux et (3) sur les flancs de montage où poussent quelques plantes (Azorella selago, Colobanthus kerguelensis ou Lycopodium magellanicum et/ou des bryophytes). Notre étude permettra l’installation de mesures de biosécurité afin de tempérer les introductions accidentelles dans des zones vierges non encore colonisées par M. soledadinus.Renault David, Chevrier Muriel, Laparie M., Vernon Philippe, Lebouvier Marc. Characterization of the habitats colonized by the alien ground beetle Merizodus soledadinus at the Kerguelen Islands. In: Revue d'Écologie (La Terre et La Vie), supplément n°12, 2015. Les invasions biologiques et leur gestion au carrefour des sciences naturelles et des sciences humaines et sociales. Colloque organisé à Rennes (Université de Rennes 1) du 20 au 22 octobre 2014. pp. 28-32

Characteristics of introduced Aphididae species, an endemic fly (Anatalanta aptera) and an introduced ground beetle (Merizodus soledadinus) on the Kerguelen Islands

The suite of environments and anthropogenic modifications of sub-Antarctic islands provide key opportunities to improve our understanding of the potential consequences of climate change and biological species invasions on terrestrial ecosystems. The profound impact of human introduced invasive species on indigenous biota, and the facilitation of establishment as a result of changing thermal conditions, has been well documented on the French sub-Antarctic Kerguelen Islands (South Indian Ocean). The present study provides an overview of the vulnerability of sub-Antarctic terrestrial communities with respect to two interacting factors, namely climate change and alien insects. We present datasets assimilated by our teams on the Kerguelen Islands since 1974, coupled with a review of the literature, to evaluate the mechanism and impact of biological invasions in this region. First, we consider recent climatic trends of the Antarctic region, and its potential influence on the establishment, distribution and abundance of alien insects, using as examples one fly and one beetle species. Second, we consider to what extent limited gene pools may restrict alien species' colonisations. Finally, we consider the vulnerability of native communities to aliens using the examples of one beetle, one fly, and five aphid species taking into consideration their additional impact as plant virus vectors. We conclude that the evidence assimilated from the sub-Antarctic islands can be applied to more complex temperate continental systems as well as further developing international guidelines to minimise the impact of alien species

Emergence of atypical phenologies at both longitudinal ends of the northern expansion front of the pine processionary moth: the importance of identifying local drivers

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