Climate change-driven elevational changes among boreal nocturnal moths

Abstract

Climate change has shifted geographical ranges of species northwards or to higher altitudes on elevational gradients. These changes have been associated with increases in ambient temperatures. For ectotherms in seasonal environments, however, life history theory relies largely on the length of summer, which varies somewhat independently of ambient temperature per se. Extension of summer reduces seasonal time constraints and enables species to establish in new areas as a result of over-wintering stage reaching in due time. The reduction of time constraints is also predicted to prolong organisms' breeding season when reproductive potential is under selection. We studied temporal change in the summer length and its effect on species' performance by combining long-term data on the occurrence and abundance of nocturnal moths with weather conditions in a boreal location at Värriötunturi fell in NE Finland. We found that summers have lengthened on average 5 days per decade from the late 1970s, profoundly due to increasing delays in the onset of winters. Moth abundance increased with increasing season length a year before. Most of the species occurrences expanded upwards in elevation. Moth communities in low elevation pine heath forest and middle elevation mountain birch forest have become inseparable. Yet, the flight periods have remained unchanged, probably due to unpredictable variation in proximate conditions (weather) that hinders life histories from selection. We conclude that climate change-driven changes in the season length have potential to affect species' ranges and affect the structure of insect assemblages, which may contribute to alteration of ecosystem-level processes.

Positive shifts in species richness and abundance of moths over five decades coincide with community-wide phenotypic trait homogenisation

“…The finding of a dramatic overall increase in abundance and species richness is inconsistent with many recent studies (Franzen and Johannesson 2007;Nilsson et al 2008;Sánchez-Bayo and Wyckhuys 2019). However, previous reports show increases in richness and abundance from studies conducted at higher latitudes (Antão et al 2020;Keret et al 2020) and in freshwater ecosystems (van Klink, 2020). The present study was conducted in a high latitude transitional boreonemoral zone dominated by mixed forests, relatively species-poor moth communities, and characterised by shorter and brighter nights, less light pollution, lower temperatures, low human population densities, compared with many areas in the south.…”

Developmental temperature predicts body size, flight, and pollen load in a widespread butterfly

“…Given their large population sizes, relatively short generation times (for many taxa), and highly plastic life histories, insects are expected to respond rapidly, both ecologically and evolutionarily, to increased temperatures. Several studies have demonstrated that in response to climate warming, insect distributions have expanded poleward (Hickling et al, 2005; Li et al, 2014; Parmesan et al, 1999) and up‐slope (Chen et al, 2009; Keret et al, 2020; Kerr et al, 2015; Menéndez et al, 2014; Wilson et al, 2005). Springtime emergence of insects has also advanced (Gordo & Jose Sanz, 2009; Hällfors et al, 2021; Hassall et al, 2007; Visser et al, 2006) and body sizes have decreased (Bowden et al, 2015; Nooten & Rehan, 2020; Tseng et al, 2018).…”

Rising minimum temperatures contribute to 50 years of shifting Arctic and boreal butterfly communities in North America

“…Finally, exploration of our climate data revealed that average minimum temperature and average precipitation were highly correlated (Pearson's r = 0.67 for the 100×100-kilometer scale and Pearson's r = 0.73 for the 200×200-kilometer scale), thus we opted to run our models separately for both climate covariates (results for temperature are shown in the main text and precipitation in the Supplementary material). We opted to focus on temperature over precipitation as prior research has demonstrated temperature to be more important for range dynamics in butterflies (Keret et al 2020).…”