Fig. 1

In general, flowering plant richness decreases with increasing latitude (A). However, the number of plants a focal species (here, the honey bee) interacts with (its niche breadth) could covary with this decline in multiple ways. If the species is a wide generalist, with interactions representing a random sample of the potential partners, then the niche breadth should follow the pattern of species richness aligning with the Neutral Theory (B). Alternatively, the species may focus on fewer species in the tropics but interact more strongly with each species, as proposed by the Latitudinal Biotic Interaction Hypothesis. This would lead to greater generalism at higher latitudes (C). We use the honey bee Apis mellifera as our focus to explore latitudinal gradients in niche breadth because of the global distribution of this species - as seen in global distribution data available through GBIF (D; [26]) shown by the yellow dots on the map. Note that A. mellifera’s occurrence is more comprehensive than shown by GBIF records, covering most of the world [27]. In particular, note that A. mellifera occurs, and our dataset includes records from, much more of Africa than is included in the GBIF record. The red dots indicate the location of samples used in the current study (D)