Phenology responses of temperate butterflies to latitude depend on ecological traits

Abstract

Global change influences species’ seasonal occurrence, or phenology. In cold‐adapted insects, the activity is expected to start earlier with a warming climate, but contradictory evidence exists, and the reactions may be linked to species‐specific traits. Using data from the GBIF database, we selected 105 single‐brooded Holarctic butterflies inhabiting broad latitudinal ranges. We regressed patterns of an adult flight against latitudes of the records, controlling for altitude and year effects. Species with delayed flight periods towards the high latitudes, or stable flight periods across latitudes, prevailed over those that advanced their flight towards the high latitudes. The responses corresponded with the species’ seasonality (flight of early season species was delayed and flight of summer species was advanced at high latitudes) and oceanic vs. continental climatic niches (delays in oceanic, stability in continental species). Future restructuring of butterfly seasonal patterns in high latitudes will reflect climatic niches, and hence the evolutionary history of participating species.

Method matters: pitfalls in analysing phenology from occurrence records

“…Our results varied substantially in both onset and termination across species (Figure 2). In contrast to Fric et al (2020), we found significantly later and/or shorter flight periods at higher latitudes for most species. These new results were consistent with the latitudinal gradient in climate and growing season length (Kobayashi et al 2016).…”

“…Given these biases, proper data curation and appropriate modelling strategies are necessary to ensure valid inferences. Fric et al 2020 used occurrence data for 100 species aggregated in the Global Biodiversity Information Facility (GBIF) in temperate regions of North America and Europe to track phenology across latitudes. Estimating phenology metrics and trends from large occurrence datasets is possible, but requires sufficient data density and appropriate statistical methods (Taylor & Guralnick 2019).…”

“…Many species analysed (in 105 datasets separated by continent) in Fric et al (2020) had insufficient data for independent analysis. Data were analysed with as few as 15 occurrence records across > 20°latitude and >100 years.…”

“…Finally, the analytical approach in Fric et al (2020) produced biased results. Beyond regressing individual species' phenometrics against latitude, altitude and year separately, regression of residuals was used for corrected regressions.…”

The story of endurance: Biogeography and the evolutionary history of four Holarctic butterflies with different habitat requirements

“…Their current ranges reach to the far North (see the sampling locations, Figures 1–4), suggesting efficient mechanisms of winter diapause (cf. Vrba et al., 2017) and an ability to capitalize on short but intensive Arctic summers (Faltynek Fric et al., 2020).…”