Genetic diversity of photobionts in Antarctic lecideoid lichens from an ecological view point

Abstract

As part of a comprehensive study on lecideoid lichens in Antarctica, we investigated the photobiont diversity and abundance in 119 specimens of lecideoid lichens from 11 localities in the continental and maritime Antarctic. A phylogeny of these photobiont ITS sequences, including samples from arctic, alpine and temperate lowland regions, reveals the presence of five major Trebouxia clades in Antarctic lecideoid lichens. Two clades are formed by members of the T. jamesii and T. impressa aggregates but for all other clades no close match to any known Trebouxia species could be found in sequence databases. One genetically uniform and well-supported Trebouxia clade was found only in the climatically unique cold desert regions of the Antarctic (preliminarily called Trebouxia sp.URa1), where it is preferentially associated with the highly adapted Antarctic endemic lichen Lecidea cancriformis. Levels of genetic photobiont diversity differ slightly, but insignificantly among ecological regions of the Antarctic and do not decrease towards regions with more unfavourable ecological conditions. The genetic diversity of photobionts varies among mycobiont species. Most pairwise comparisons reveal that these differences are insignificant, probably due to the small sample size for most species. The Antarctic lichens studied here are predominantly not specific for a single photobiont species or lineage, except for Lecidella greenii and L. siplei. These two species are preferably associated with Trebouxia sp. URa2, although in the sampling areas of both species, a pool of several other photobionts is available. Lecidea cancriformis associates with the highest diversity of photobionts followed by L. andersonii.

A first approach to calculate BIOCLIM variables and climate zones for Antarctica

“…All together, they described six different climate zones, of which only the first three were restricted to Antarctica and thus also mentioned here. Ruprecht et al (2012a) described some tendencies which in the main also appear in the classification of the present study: T. jamesii seems to be rather variable regarding climate (their samples occurred in all the six climate zones), but the (exclusively Antarctic) subspecies only occurs in cold and dry areas. T. sp.…”

“…But to date, the similarities of the areas in terms of macroclimate conditions were not investigated, mainly due to the lack of area covering climate data for Antarctica. Several studies show clear differentiation in species composition on lichen photobionts, which are evidently climate related (Fernandez-Mendoza et al 2011;Jones et al 2013;Peksa and Skaloud 2011;Ruprecht et al 2012a) and match well with the macroclimate conditions. However, for large-scale niche modeling projects which require two types of data, accurate latitude/longitude coordinates (i.e., georeferenced localities) and environmental data available in form of GIS layers, no sufficient continent covering climate data was available.…”

“…12. For the comparison of this study and the study of Ruprecht et al (2012a), it is important to notice that the latter also included samples from South America, Europe, USA, and Arctic, which was not done here. All together, they described six different climate zones, of which only the first three were restricted to Antarctica and thus also mentioned here.…”

“…The present study is an important contribution to a current research project (Diversity, ecology, and specificity in Antarctic lichens) to search for evidence that variations in Antarctic macroclimate may control the distribution of photobionts and/or mycobionts in the all over the continent available crustose lecideoid lichens and possibly the specificity of (certain) mycobionts towards the photobionts (Ruprecht et al 2012a). There have been several studies dealing with this climate-dependent specificity between mycobiont and photobiont (e.g., Fernandez-Mendoza et al 2011;Jones et al 2013;Peksa and Skaloud 2011;Ruprecht et al 2012a).…”

“…There have been several studies dealing with this climate-dependent specificity between mycobiont and photobiont (e.g., Fernandez-Mendoza et al 2011;Jones et al 2013;Peksa and Skaloud 2011;Ruprecht et al 2012a). In our study, we aim to define the base for the modeling and comparison of the Antarctic climatic conditions, in order to show preferences of each symbiotic partner (photobiont vs. mycobiont) identified within given lichen samples.…”