Alpine microclimates, biodiversity, and climate change

Abstract/Description

The vast majority of individuals in an ant colony are sterile females, that is, workers. Normally, exclusively queens and males are the fertile individuals. After mating, queens can lay eggs, from which female individuals (diploids) and/or males (haploids) will hatch. Nevertheless, under specific ecological circumstances, workers can lay eggs, from which haploid males or diploid females, that is, cloned workers, can originate by asexual reproduction. Lasius fuliginosus is a well-studied ant species because of its peculiar ecology that occurs up to the timber line and plays an important role in mountain ecosystems. This fungus breeding ant is famous for building its paper-nests using shredded wood, honey dew, and the hyphae of symbiotic fungi. The breeding system is peculiar (queens must penetrate the nests of other Lasius species to reproduce), and many details still await discovery. The aim of this study was to investigate within-nest relatedness between individuals in several L. fuliginosus as a basis to evaluate the occurrence of asexual reproduction. We sampled 744 individuals from 62 different nests in five populations in Austria and Germany along elevational transects and used 12 nuclear microsatellite loci for evaluating genetic diversity. We estimated the linkage disequilibrium, deviations from Hardy-Weinberg equilibrium, heterozygosity, allele frequency, allelic richness, probability of identity, and genetic relatedness inside each nest. We found clones originating from asexual reproduction in nearly half of the L. fuliginosus nests analyzed. This now opens up questions about proximate causations, such as if clonal individuals are produced by workers and / or queens. The latter would mean that sexual and asexual reproduction by the same individual coexists. Our findings also open up questions about ultimate causations, such as the dependence of asexuality in this ant on environmental conditions. In more detail, as environmental conditions become more extreme at higher altitudes, ant populations may benefit from increasing colony size through asexual reproduction, while avoiding the risks associated with sexual reproduction. The presence of asexual reproduction in L. fuliginosus provides new insights into the reproductive mode and social structure of ants generally as it does into mountain ecosystems.

Abstract/Description

In recent decades, the rate of change in species richness in European mountain summits has increased and been correlated with rising temperatures. However, evidence of seasonal soil moisture deficit as a potentially emerging driver has rarely been discussed. In fact, species richness changes have been strongest on calcareous bedrock, so that limestone mountain summits with their shallow soils might serve as early warning signals of species redistributions.

Here, we present plant species diversity patterns on mountain summits between 2.203 m and 2513 m asl. in the National Park Berchtesgaden in Germany (GLORIA site DE-NPB, resurveyed between 2007 and 2024) along with in situ measured microclimate (growing degree days, snow cover), soil temperature and soil moisture data (Geoprecision+TOMST). For understanding details on species-specific leading and trailing edges, we further draw on recently recorded field data representing three different local species pools, summit (GLORIA NPB), alpine (AlpVeg NPB) and subalpine (Almenkartierung NPB), as well as species occurrence data from other calcareous GLORIA sites across the European Alps.

Abstract/Description

Mountain environments pose significant climatic challenges for breeding birds, including strong temperature fluctuations and exposure to harsh weather. Nest-site selection can help mitigate these stressors and improve fitness. Rock cavities may offer thermal advantages by buffering external temperature variation. We monitored alpine bird nests in two volcanoes of the temperate Andes during the 2024–2025 breeding season in southern Chile (~39°S, 71°W). A total of 40 nests from six treeline-breeding species were studied: Blue-and-white Swallow (Pygochelidon cyanoleuca, n = 23), White-browed Ground-Tyrant (Muscisaxicola albilora, n = 8), Ochre-naped Ground-Tyrant (Muscisaxicola flavinucha, n = 1), Buff-winged Cinclodes (Cinclodes fuscus, n = 7), Plumbeous Sierra Finch (Geospizopsis unicolor, n = 1), and Upucerthia saturatior (n = 1). To assess microclimatic conditions, thermal sensors (Hobo Temp) were placed inside and outside 20 nest cavities (n = 40). External sensors were positioned in stone stacks, facing north, and shielded from direct sunlight, up to 130 cm from cavity entrances. Temperature was recorded every 10 minutes for 42 hours per cavity. Temperature differences between interior and exterior were analyzed for four species: P. cyanoleuca (n = 9), M. albilora (n = 6), C. fuscus (n = 4), and U. saturatior (n = 1). Across species, temperatures were generally higher inside at night and lower in the evening. However, variation in magnitude and direction was species-specific. For M. albilora, all cavities were warmer inside at night and cooler in the evening, while three were warmer outside at twilight and one in the morning. C. fuscus followed the same pattern, with two cavities warmer outside at twilight and one in the morning. P. cyanoleuca showed significant nighttime differences, with higher temperatures inside. Five cavities differed at twilight, only one being warmer inside. Additionally, four cavities were warmer in the morning. U. saturatior showed temperature differences in all periods except the morning. These findings suggest that mountain-top species may select rock cavities for their microclimatic benefits, indicating an adaptive response to thermal conditions.