Fig. 1: Seasonality and latitudinal phenology of V. cardui.
From: A north-south hemispheric migratory divide in the butterfly Vanessa cardui
A The central heatmap plot shows monthly frequencies of V. cardui occurrences by latitudinal divisions. Maps illustrate differing photoperiod and temperature amplitudes across the distributional range, factors likely influencing the migratory syndrome and denoting substantial differences between hemispheres. Occurrence data comprise 768,332 observations of painted ladies obtained from public repositories and authors’ field expeditions. Peaks of presence linking consecutive months can be observed. Monthly frequencies through the year are relative to each latitudinal division. B Summary of hypothesised migratory movements in both hemispheres. Synchrony in northwards and southwards movements in the two populations may lead to allochrony in the equatorial zone, with independent populations spatially overlapping but temporally isolated. The Sahara Desert (yellow) and the tropical forest (green) are regions where V. cardui seldom breeds. Data used for monthly observations are available in Supplementary Data 1. Data underlying the temperature amplitude map are deposited into the OSF repository and are available at the following URL: https://osf.io/6u32k/. Data underlying the photoperiod amplitude map can be obtained online using the provided code (https://doi.org/10.5281/zenodo.17113173). Maps were made using free vector and raster map data from naturalearthdata.com. Butterfly illustrations by Blanca Martí.
