Bartlett Jesamine, Convey Pete, Hayward Scott A L
1University of Birmingham, Edgbaston, Birmingham, B15 2TT UK.
2British Antarctic Survey, NERC, High Cross, Madingley Rd, Cambridge, CB3 0ET UK.
Polar Biol. 2019;42(2):271-284. doi: 10.1007/s00300-018-2420-4. Epub 2018 Oct 16.
Understanding the physiology of non-native species in Antarctica is key to elucidating their ability to colonise an area, and how they may respond to changes in climate. is a chironomid midge introduced to Signy Island (Maritime Antarctic) from South Georgia (Sub-Antarctic) where it is endemic. Here, we explore the tolerance of this species' egg masses to heat and desiccation stress encountered within two different oviposition microhabitats (ground surface vegetation and underlying soil layer). Our data show that, whilst oviposition takes place in both substrates, egg sacs laid individually in soil are at the greatest risk of failing to hatch, whilst those aggregated in the surface vegetation have the lowest risk. The two microhabitats are characterised by significantly different environmental conditions, with greater temperature fluctuations in the surface vegetation, but lower humidity (%RH) and available water content in the soil. Egg sacs were not desiccation resistant and lost water rapidly, with prolonged exposure to 75% RH affecting survival for eggs in singly oviposited egg sacs. In contrast, aggregated egg sacs ( = 10) experienced much lower desiccation rates and survival of eggs remained above 50% in all treatments. Eggs had high heat tolerance in the context of the current microhabitat conditions on Signy. We suggest that the atypical (for this family) use of egg sac aggregation in has developed as a response to environmental stress. Current temperature patterns and extremes on Signy Island are unlikely to affect egg survival, but changes in the frequency and duration of extreme events could be a greater challenge.
了解南极非本土物种的生理机能是阐明它们在某一地区定殖能力以及它们如何应对气候变化的关键。摇蚊是一种从南乔治亚岛（亚南极地区）引入西格尼岛（南极海洋地区）的摇蚊，南乔治亚岛是其本土栖息地。在此，我们探究了该物种卵块对两种不同产卵微生境（地表植被和下层土壤层）中遇到的热应激和干燥应激的耐受性。我们的数据表明，虽然在这两种基质中都会产卵，但单独产在土壤中的卵囊孵化失败的风险最大，而聚集在地表植被中的卵囊风险最低。这两种微生境的环境条件显著不同，地表植被中的温度波动更大，但土壤中的湿度（相对湿度%）和有效含水量更低。卵囊不耐干燥，水分流失迅速，长时间暴露在75%相对湿度下会影响单个产卵卵囊中卵的存活。相比之下，聚集的卵囊（n = 10）干燥率低得多，在所有处理中卵的存活率均保持在50%以上。在西格尼岛当前的微生境条件下，卵具有较高的耐热性。我们认为，摇蚊卵囊聚集这种非典型（对于该科而言）的行为是对环境压力的一种反应。西格尼岛上当前的温度模式和极端温度不太可能影响卵的存活，但极端事件的频率和持续时间的变化可能是一个更大的挑战。
