Some like it hot: microclimatic variation affects the abundance and movements of a critically endangered dung beetle

Abstract

Abstract. 1. Habitat loss and fragmentation is a leading cause of species extinction. This not only concerns loss of major habitats, but also loss of microclimatic heterogeneity within such habitats.2. In this study, we examine the effects of microclimate on the abundance and movements of Onthophagus gibbulus, a dung beetle associated with pastoral habitats. While formerly widespread in Southern Finland, the species is now critically endangered at a national level, persisting within an area of 6 km 2 . 3. We divided the Finnish distribution of O. gibbulus into 50 · 50-m grid cells, characterised local microclimate by incident solar radiation, and surveyed the distribution of O. gibbulus within a subset of cells. To investigate the impact of microclimatic conditions on dung beetle movements, we conducted a mark-release-recapture study.4. Our approach allowed us to estimate the national population size of O. gibbulusa figure rarely available for endangered insect species. The Finnish population of O. gibbulus comprises between 2000 and 6000 individuals.5. The abundance of beetles per dung pat increases with incident solar radiation, and beetles are more likely to move towards warmer than colder spots in the landscape.6. Overall, our study depicts O. gibbulus as a thermophile confined to the warmest part of the landscape, and offers loss of microclimatic variation as the cause for its largescale decline. To conserve O. gibbulus and similar species, we need to consider not only the amount of macrohabitats, but also the amount and distribution of microclimatic variation within them. Future predictions are complicated by ongoing climate change.

MESOCLOSURES – increasing realism in mesocosm studies of ecosystem functioning

“…For instance, Onthophagus gibbulus (Pallas, 1781) is critically endangered in Finland and has been found to be most abundant in the hottest and most strongly grazed parts of its habitat (Roslin et al . ). The species richness of dung beetles has also been shown to increase in grazed, open areas compared to overgrown habitats in some instances (Verdú et al .…”

Incorporating microclimate into species distribution models

“…For example, strong correlations have been observed between changes in the frequency of plant species over time and the in-situ temperature of their preferred microhabitat on mountain summits in Switzerland (Kulonen et al 2018). Sometimes, topoclimatic variables derived directly from DEMs (like elevation, solar radiation or cold-air pooling) are also used independently in SDMs, thus using an indirect topoclimatic derivative instead of actually downscaled climate to improve the spatial resolution of SDMs (Roslin et al 2009, Maclean et al 2015, Shinneman et al 2016, Patsiou et al 2017.…”

Moisture, thermal inertia, and the spatial distributions of near-surface soil and air temperatures: Understanding factors that promote microrefugia

“…As long as the quality of climate data continues to be overlooked as a source of error in species distribution models (Soria-Auza et al, 2010), and insufficient research is undertaken to relate global climate change to ecologically relevant microclimates (Kennedy, 1997), we will be unable to predict future impacts to microclimate-sensitive species (e.g. Roslin et al, 2009). …”