Butterfly phenology in Mediterranean mountains using space‐for‐time substitution

Abstract

Inferring species' responses to climate change in the absence of long-term time series data is a challenge, but can be achieved by substituting space for time. For example, thermal elevational gradients represent suitable proxies to study phenological responses to warming. We used butterfly data from two Mediterranean mountain areas to test whether mean dates of appearance of communities and individual species show a delay with increasing altitude, and an accompanying shortening in the duration of flight periods. We found a 14-day delay in the mean date of appearance per kilometer increase in altitude for butterfly communities overall, and an average 23day shift for 26 selected species, alongside average summer temperature lapse rates of 3°C per km. At higher elevations, there was a shortening of the flight period for the community of 3 days/km, with an 8.8-day average decline per km for individual species. Rates of phenological delay differed significantly between the two mountain ranges, although this did not seem to result from the respective temperature lapse rates. These results suggest that climate warming could lead to advanced and lengthened flight periods for Mediterranean mountain butterfly communities. However, although multivoltine species showed the expected response of delayed and shortened flight periods at higher elevations, univoltine species showed more pronounced delays in terms of species appearance. Hence, while projections of overall community responses to climate change may benefit from space-for-time substitutions, understanding species-specific responses to local features of habitat and climate may be needed to accurately predict the effects of climate change on phenology. K E Y W O R D Schanging climate, developmental delay, elevational gradient, emergence time, flight period S U PP O RTI N G I N FO R M ATI O NAdditional supporting information may be found online in the Supporting Information section.

Low winter precipitation, but not warm autumns and springs, threatens mountain butterflies in middle-high mountains

“…Univoltine butterflies of Sierra de Guadarrama, Spain, advanced flight onset after warm springs, but this was not always connected with increased abundances (Stewart et al, 2020). Zografou et al (2020) observed delayed flight onsets and shorter durations in higher elevations of two Greek mountain systems. In the Erebia butterflies studied here, warmer conditions during larval feeding periods may support larval growth, extending adult longevity.…”

Species traits affect phenological responses to climate change in a butterfly community

“…Earlier emergence or mean flight dates have been widely documented 1 , 9 , 15 , 31 , 56 , 57 and have often been assumed to enable species to adjust to a changing climate. Shifts in mean flight dates were not related to population change across all species in our study, however.…”

“…This is because the direct response of oligophagous species to abiotic conditions altered by climate change may be tempered by their high dependence on their host plants 1 . Second, we expected larval woody feeders to show more pronounced changes in the seasonal timing and duration of the adult flight period compared to larval herb feeders since herbs can produce fresh shoots throughout the season while leaves of woody plants are available only for a short time period 8 , 31 and the newly flushing leaves of woody plants are increasingly appearing earlier in response to climate change 32 . Thus, woody feeders may track the earlier availability of fresh leaves of woody plants, and transition to the adult flighted stage earlier.…”

Changes in Alpine Butterfly Communities during the Last 40 Years

“…In the European Alps, the effect of climate change, a large-scale driver, is confounded by local-scale human activities. Cattle grazing in the alpine pastures has decreased throughout the last century, allowing a fast recolonisation by trees and shrubs, but this can also result from climatologic variation [21,25,54,88].…”

“…Butterflies, as well as biotic components in general, may adapt to changing environments showing phenological plasticity and/or genetic changes (see [51] for a review on invertebrates), as well as by shifting their spatial distribution moving towards favourable conditions [52]. Thus, as the climate warms, adults tend to emerge earlier [53,54], flight periods last longer [54] and numbers of generations in multivoltine species increase [55]. In mountain ecosystems, upwards shifts of species linked to colder conditions can be observed [8,52].…”