Alpine butterflies want to fly high: Species and communities shift upwards faster than their host plants

Abstract

Despite sometimes strong codependencies of insect herbivores and plants, the responses of individual taxa to accelerating climate change are typically studied in isolation. For this reason, biotic interactions that potentially limit species in tracking their preferred climatic niches are ignored. Here, we chose butterflies as a prominent representative of herbivorous insects to investigate the impacts of temperature changes and their larval host plant distributions along a 1.4‐km elevational gradient in the German Alps. Following a sampling protocol of 2009, we revisited 33 grassland plots in 2019 over an entire growing season. We quantified changes in butterfly abundance and richness by repeated transect walks on each plot and disentangled the direct and indirect effects of locally assessed temperature, site management, and larval and adult food resource availability on these patterns. Additionally, we determined elevational range shifts of butterflies and host plants at both the community and species level. Comparing the two sampled years (2009 and 2019), we found a severe decline in butterfly abundance and a clear upward shift of butterflies along the elevational gradient. We detected shifts in the peak of species richness, community composition, and at the species level, whereby mountainous species shifted particularly strongly. In contrast, host plants showed barely any change, neither in connection with species richness nor individual species shifts. Further, temperature and host plant richness were the main drivers of butterfly richness, with change in temperature best explaining the change in richness over time. We concluded that host plants were not yet hindering butterfly species and communities from shifting upwards. However, the mismatch between butterfly and host plant shifts might become a problem for this very close plant–herbivore relationship, especially toward higher elevations, if butterflies fail to adapt to new host plants. Further, our results support the value of conserving traditional extensive pasture use as a promoter of host plant and, hence, butterfly richness.

A fiddler crab reduces plant growth in its expanded range

“…Engineering species worldwide, such as kelp (Gilson et al, 2021), urchins (Ling, 2008), grasses (Kerner et al, 2022), and mangroves (Chapman et al, 2021), have expanded their ranges due to climate change. Our results show that climate migrants can influence key ecosystem functions such as primary production and trophic interactions in their new ranges in unexpected ways.…”

Micro‐ and macroclimate interactively shape diversity, niches and traits of Orthoptera communities along elevational gradients

“…We used the mean elevation of the study sites as a proxy for macroclimatic temperature variation along the gradient (hereafter referred to as macroclimate/elevation, correlation with summer‐seasonal mean temperature derived from a climate model based on neighbouring local climate station temperature data: r = −.98, df = 1,92, p < .001; Kerner et al., 2023). At each of the study sites, we additionally recorded temperature in 2‐h intervals from June to October 2020 with three covered temperature loggers (ibuttons, Maxim Integrated) installed 2 cm above the soil level in the vegetation to account for average near ground temperature deviations from macroclimate resulting from vegetation structure, aspect/orientation, inclination/slope, exposition, topography, wind speed, solar radiation, atmospheric moisture and cloud cover (Hodkinson, 2005; Hoiss et al., 2013; König et al., 2022).…”

“…Rapid range shifts of insect communities to higher elevations in mountain regions due to temperature increase have been shown (Kerner et al., 2023; Maihoff et al., 2023; Ogan et al., 2022). However, responses to increasing temperatures are species‐specific (Engelhardt et al., 2022; Hickling et al., 2006; Neff et al., 2022; Poniatowski et al., 2020).…”

Active around the year: Butterflies and moths adapt their life cycles to a warming world

“…Summers are becoming hotter and drier, winters wet and mild (Christidis & Stott, 2021). These changes are particularly visible in the higher Alpine regions, where annual amounts of precipitation and temperatures significantly rose since the 1980s (Kerner et al., 2023; Ohmura, 2012). These changes caused earlier plant leaf unfolding and prolonged vegetation periods in autumn (Wang et al., 2022).…”

“…As a reaction to these climatic changes, numerous plant and animal species are shifting their distribution ranges to higher latitudes and altitudes where they now find appropriate conditions (Parmesan et al., 1999; Parmesan & Yohe, 2003). Altitudinal shifts are particularly visible in the European Alps (Bonelli et al., 2021; Kerner et al., 2023; Neff et al., 2022; Rödder et al., 2021; Roth et al., 2014). Cold‐adapted (arctic‐)alpine and (boreo‐)montane species as well as continental species suffer from increased temperatures and less predictable precipitation regimes (Schmitt, 2007).…”