Haran R. (2025) Mutualism across biogeographic regions between Lesser Whitethroat Curruca curruca and Maerua crassifolia trees. ARDEA 113 (2): 5-5

For pollination via mutualism to occur, both the plant and the pollinator must be present at the same time, specifically during the plant’s flowering. Migrating birds may act as pollinators for different plant species that flower at different times of the year, and in different places thousands of kilometres apart. The insectivorous palearctic warbler Lesser Whitethroat Curruca curruca winters in eastern Sahel where it is found to be a major visitor on flowering Sahelo-Sudanian Maerua crassifolia trees (Capparaceae). The peak flowering of M. crassifolia occurs in January, in the middle of Sahel’s dry season. Lesser Whitethroats use the eastern Mediterranean flyway during spring migration towards their breeding sites all over Europe. Bird migration was monitored for 12 years, in three different sites in the Dead Sea Valley, c. 1200 km north of the Sahel. These sites hold a disjunct, relict and northernmost part of the world distribution of Sudanian flora. Specifically, the Ein Gedi oasis, holds dozens M. crassifolia trees. In this study it is shown that in the Dead Sea Valley (1) the Lesser Whitethroat is a potential major pollinator of M. crassifolia while consuming nectar and picking pollen from the flowers on its feathers, (2) the peak migration of Lesser Whitethroats and the peak flowering of M. crassifolia coincide in the beginning of April and (3) the Lesser Whitethroat prefers stopover sites with flowering M. crassifolia trees. These findings suggest that mutualism exists between the Lesser Whitethroat and M. crassifolia, in different seasons and in different biogeographical regions. In addition, these findings suggest a possible adjustment of M. crassifolia flowering time, on an edge of its distribution range, to the phenology of its migrating pollinators.