Inclusion of trophic interactions increases the vulnerability of an alpine butterfly species to climate change

Abstract

Climate change is expected to have significant and complex impacts on ecological communities. In addition to direct effects of climate on species, there can also be indirect effects through an intermediary species, such as in host-plant interactions.Indirect effects are expected to be more pronounced in alpine environments because these ecosystems are sensitive to temperature changes and there are limited areas for migration of both species (i.e. closed systems), and because of simpler trophic interactions. We tested the hypothesis that climate change will reduce the range of an alpine butterfly (Parnassius smintheus) because of indirect effects through its host plant (Sedum sp.). To test for direct and indirect effects, we used the simulations of climate change to assess the distribution of P. smintheus with and without Sedum sp. We also compared the projected ranges of P. smintheus to four other butterfly species that are found in the alpine, but that are generalists feeding on many plant genera. We found that P. smintheus gained distributional area in climate-only models, but these gains were significantly reduced with the inclusion of Sedum sp. and in dryclimate scenarios which resulted in a reduction in net area. When compared to the more generalist butterfly species, P. smintheus exhibited the largest loss in suitable habitat. Our findings support the importance of including indirect effects in modelling species distributions in response to climate change. We highlight the potentially large and still neglected impacts climate change can have on the trophic structure of communities, which can lead to significant losses of biodiversity. In the future, communities will continue to favour species that are generalists as climate change induces asynchronies in the migration of species. K E Y W O R D S alpine, biotic interactions, butterfly, global change, host-plant, maxent, species distribution modelling

Climate change drives mountain butterflies towards the summits

“…Nevertheless, previous studies showed similar range shifts towards higher altitudes in high mountain systems also for other organismal groups, as reported for montane and subalpine bumblebees, with upwards shift of more than 300 m within 33 years 35 , or a shift of almost 500 m of the alpine bumblebee Bombus alpinus in the Alps within as little as three decades 36 . Similarly, mountain plant species (the larval food plants of many butterflies) have shifted their distributions considerably towards the summits over time 37 , which might also interrupt interactions among species 38 .…”

“…Filazzola and colleagues predict a potential distribution expansion of this butterfly in the wake of climate warming. However, by integrating the future distributions of the relevant Sedum species (under dry-climate scenarios), a relevant reduction of the realised distribution of the butterfly is more likely in the near future 38 . Severe future geographic mismatches between butterflies and their larval food plants become even more likely against the background of diverging response velocities in both groups: The response of plant species to climate warming is rather moderate and slow if compared with flying insects 40 .…”

“…These findings go in line with other studies showing repeatedly that species’ responses to environmental changes strongly diverge depending on their specific demands, behaviour and plasticity 41 . For example, Filazzola and colleagues 38 modelled future distributions of five mountain butterfly species in North America and found that only generalist species (relying on a broad variety of different larval food plants) may benefit from distribution range expansions mediated by climate change. In contrast, the Rocky Mountain Apollo Parnassius smintheus , a specialist mostly relying on one larval food plant, might lose a significant proportion of its potentially suitable distribution range due to lacking future niche overlaps with this food plant.…”

Autumn larval cold tolerance does not predict the northern range limit of a widespread butterfly species

“…cresphontes at a broad scale. While other factors were not tested here, for example, biotic interactions (e.g., host plant occurrence; Filazzola et al., 2020), our results suggest that P . cresphontes depends on specific heat accumulation and water availability to complete its life cycle.…”

Spatial variation in early‐winter snow cover determines local dynamics in a network of alpine butterfly populations

“…Non‐mobile life stages of insects, such as eggs, are particularly vulnerable to weather extremes compared to mobile caterpillars (Turlure et al 2010) and adults (Ashton et al 2009, Bennett et al 2015) which can effect some choice in microclimate when active in spring and summer. Temperatures experienced by over‐wintering butterflies affects their physiology (Williams et al 2012, Stuhldreher et al 2014), dynamics (Forister et al 2011, Boggs and Inouye 2012, Roland and Matter 2013, 2016), community structure (Nice et al 2014) and potentially changes in their geographic range (Crozier 2004, Filazzola et al 2020).…”