Micro-habitat shifts by butterflies foster conservation strategies to preserve pollinator diversity in a warming Mediterranean climate

Abstract

The Butterfly Monitoring Scheme based on linear transects conducted by citizen scientists has become a fundamental indicator for understanding the impact of climate change on butterfly populations. A key finding is the fast poleward expansion of butterfly distributions in Europe, coupled with slower population declines in southern regions. Given that the Mediterranean region is a climate change hotspot, understanding the largely unknown mechanisms employed by butterflies to cope with increasing aridity is crucial for developing data-driven conservation strategies. To address this issue, we developed a monitoring approach based on 90 transects fully covering areas of 50 m × 50 m squares instead of linear paths. This enabled us to explore the fine-scale dynamics of 80 butterfly species and their association with vegetational units in the Mediterranean hills (∼800 m a.s.l. as maximum altitude) of the MAB UNESCO Reserve of Monte Peglia (Central Italy). We sampled the transects from April to October 2022 (the locally hottest summer of the last decade) and documented three main patterns: 1) butterfly richness and abundance correlate with environmental features and these relationships vary across seasons. Richer sites consisted of some 30 % of woodland and were those closer to water, mostly during summer (area-based analysis). 2) Environmental preferences vary with species traits. Specialist species and those adapted to colder climates and narrower temperature ranges were more abundant in higher altitudes sites, closer to water and with wider woodland coverage (fourth-quadrant analysis). 3) Although most species preferred meadows, when temperature increases, they increased their abundance in sites with wider tree coverage, closer to streams, and at higher altitude (species-based analysis). These dynamics demonstrate that butterflies opportunistically move to cooler micro-habitats to buffer elevated temperatures. This phenomenon potentially involves most of the community since the species showing significant effects encompass >80 % of the observed individuals. Our analysis introduces new dimensions to the niche of Mediterranean butterflies, highlighting the significance of shady micro-habitats, altitudinal ranges, and water streams. These factors are likely to become increasingly critical with rising aridity levels. By combining our findings with existing literature data, we have provided a protocol aimed at preserving Mediterranean butterflies within the resist-accept-direct framework.

Keywords

• Lepidoptera
• Climate buffering
• Micro-habitat selection
• Environmental heterogeneity
• Site management
• Woodland habitat