Habitat Use Across the Geographic Range of Limenitis reducta Reveals Stronger Constraints at the Northern Edge

Species abundance typically declines toward the edges of geographic ranges, while their conservation relevance increases. Habitat studies therefore often focus on only small parts of species' ranges, potentially biasing our understanding of ecological niches. Here, we compared habitat use of the Southern White Admiral (Limenitis reducta) between populations at the northern and near the southern range edge to assess whether and how habitat associations differ across the species' distribution range. The Swabian Jura represents the northern range edge, while the Turkish Aegean region lies near the southern range edge within the Mediterranean core distribution. We systematically surveyed larval stages in both regions. We compared host plant species, host plant height, site exposition, solar radiation duration at host plants, and shading by neighboring trees. In addition, the height of the larvae above ground was recorded. Host plant species differed between regions but belonged to the genus Lonicera in both. The species was associated with relatively well-sunlit sites in both regions, reflected by preferences for host plants receiving high solar radiation and low shading by neighboring trees. These associations were markedly stronger at the northern range edge. Larvae were found higher above ground at the northern range edge, and species occurrence was positively associated with host plant height in both regions. Regional differences in habitat associations indicate differences in realized microhabitat use between regions with contrasting macroclimatic conditions. The stronger association with highly sun-exposed habitats at the northern range edge is consistent with the hypothesis that habitat use is more strongly constrained under cooler climatic conditions than near the southern range edge. These findings highlight the importance of considering multiple parts of a species' geographic range when assessing habitat associations and developing conservation strategies under changing climatic conditions.