Elevational gradient and human effects on butterfly species richness in the French Alps

Alpine butterflies want to fly high: Species and communities shift upwards faster than their host plants

Despite sometimes strong codependencies of insect herbivores and plants, the responses of individual taxa to accelerating climate change are typically studied in isolation. For this reason, biotic interactions that potentially limit species in tracking their preferred climatic niches are ignored. Here, we chose butterflies as a prominent representative of herbivorous insects to investigate the impacts of temperature changes and their larval host plant distributions along a 1.4-km elevational gradient in the German Alps. Following a sampling protocol of 2009, we revisited 33 grassland plots in 2019 over an entire growing season. We quantified changes in butterfly abundance and richness by repeated transect walks on each plot and disentangled the direct and indirect effects of locally assessed temperature, site management, and larval and adult food resource availability on these patterns. Additionally, we determined elevational range shifts of butterflies and host plants at both the community and species level. Comparing the two sampled years (2009 and 2019), we found a severe decline in butterfly abundance and a clear upward shift of butterflies along the elevational gradient. We detected shifts in the peak of species richness, community composition, and at the species level, whereby mountainous species shifted particularly strongly. In contrast, host plants showed barely any change, neither in connection with species richness nor individual species shifts. Further, temperature and host plant richness were the main drivers of butterfly richness, with change in temperature best explaining the change in richness over time. We concluded that host plants were not yet hindering butterfly species and communities from shifting upwards. However, the mismatch between butterfly and host plant shifts might become a problem for this very close plant-herbivore relationship, especially toward higher elevations, if butterflies fail to adapt to new host plants. Further, our results support the value of conserving traditional extensive pasture use as a promoter of host plant and, hence, butterfly richness.

Faunistic Study on Butterflies in the Lowland Forests of Central Surigao del Sur, Philippines

The province of Surigao del Sur is among the areas in the Philippines with limited wildlife studies, especially on lepidopteran fauna. Thus, this study was conducted to evaluate the butterfly congregation and diversity in Gamut and Mat-e, areas which are underexplored for lepidopteran surveys. It also aimed to assess the conservation and ecological status of the species. Sweep netting for a total of 196 person-hours was carried out to document the species. The results revealed a total of 29 species belonging to four families. Among the families, Nymphalidae was the most represented, comprising 48% of the total richness. The species Gandaca harina mindanaensis and Junonia hedonia ida were the most dominant in both sites representing 12% (each) of the total population. Species richness and diversity (H’) were relatively higher in Mat-e (n=22; H’=1.22) than in Gamut (n=15; H’=1.00). The total endemicity was 31%, but higher endemism was observed in Mat-e (36%) compared with Gamut (20%). The noteworthy findings are the listing of the nationally and globally assessed as rare species (Acrophtalmia leto ochine and Jamides celeno), but were locally assessed as common in Mat-e. One recorded butterfly (Atrophaneura semperi aphtonia) was assessed to be a threatened species. Based on the results, the two habitats showed a poor representation of butterfly assemblage, however, these results are highly affected by the limitations of the observation. Thus, it is recommended that an intensive study on butterflies in the area should be considered.

Elevational gradient and human effects on butterfly species richness in the French Alps

We examined how butterfly species richness is affected by human impact and elevation, and how species ranges are distributed along the elevational gradient (200–2700 m) in the Isère Department (French Alps). A total of 35,724 butterfly observations gathered in summer (May–September) between 1995 and 2015 were analyzed. The number of estimated species per 100‐m elevational band was fitted to the elevational gradient using a generalized additive model. Estimations were also performed on a 500 m × 500 m grid at low altitude (200–500 m) to test for the human impact on species richness using generalized least squares regression models. Each species elevational range was plotted against the elevational gradient. Butterfly richness along the elevational gradient first increased (200–500 m) to reach a maximum of 150 species at 700 m and then remained nearly constant till a sharp decrease after 1900 m, suggesting that after some temperature threshold, only few specialized species can survive. At low elevation, urbanization and arable lands had a strongly negative impact on butterfly diversity, which was buffered by a positive effect of permanent crops. Butterfly diversity is exceptionally high (185 species) in this alpine department that represents less than 5% of the French territory and yet holds more than 70% of all the Rhopalocera species recorded in France. Both climate and habitat shape the distribution of species, with a negative effect of anthropization at low altitude and strong climatic constraints at high altitude.