Himantormia lugubris, an Antarctic endemic on the edge of the lichen symbiosis
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Himantormia lugubris, an Antarctic endemic on the edge of the lichen symbiosis Leo Sancho 1 & Asunción de los Ríos 2 & Ana Pintado 1 & Claudia Colesie 3 & José Raggio 1 & Carmen Ascaso 2 & Allan Green 1 Received: 6 July 2020 / Accepted: 15 September 2020 # Springer Nature B.V. 2020
Abstract Himantormia lugubris is an Antarctic endemic with a distribution restricted to the northwest tip of Antarctic Peninsula, adjacent islands and South Georgia Island. In this region H. lugubris is an important component of the epilithic lichen community. The species has a fruticose thallus with usually simple and flattened branches whose grey surface is often disrupted exposing the black and dominant chondroid axis. Because the photobiont cells are mainly restricted to the patchy grey areas, positive carbon balance seems to be rather difficult for this species. Therefore, the aim of this paper is to elucidate which functional strategy, possibly linked with thallus anatomy, is used by H. lugubris that enables it to be a successful species in the maritime Antarctic. To achieve this goal, we constructed a picture of the lichen’s physiological, anatomical and morphological characteristics by using a broad range of technologies, such as chlorophyll fluorescence, CO2 exchange and electron microscopy. We found that H. lugubris has a very low net photosynthesis, apparently restricted to the grey areas, but high respiratory rates. Therefore, positive net photosynthesis is only possible at low temperatures. Chlorophyll content is also low but is present in both gray and black areas. Our conclusion is that the only possibility for this species to achieve a positive carbon balance is to be active for long periods under optimal conditions, that means, wet, cold and with enough light, a common combination in this region of Antarctica. Given these constrains, we suggest that H. lugubris is likely to be especially sensitive species to predicted climate warming in the maritime Antarctic. Keywords Ecophysiology . Antarctic . Lichens . Photosynthesis . Anatomy . Himantormia lugubris
1 Introduction Antarctic climate is usually described as extremely cold and dry, which is true for most of the Antarctic continent but not for the north-west tip of the Antarctic Peninsula and adjacent islands, an area known as maritime Antarctic (Convey 2013). Here, strong and humid westerly winds from the Pacific Ocean are the main feature of the atmospheric circulation. Despite the climate being much more habitable than in
* Leo Sancho [email protected] 1
Unidad de Botánica, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, S-28040 Madrid, Spain
2
Departamento de Biogeoquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales, CSIC, Serrano 115 dup, 28006 Madrid, Spain
3
Global Change Institute, School of GeoSciences, University of Edinburgh, Alexander Crum Brown Road, Edinburgh EH9 3FF, UK
continental Antarctica, the prevailing cold temperatures in summer, typically below 5 °C, prevent the growth of the vast majority
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