The latitudinal gradient in plant diversity is one of the most famous patterns in ecology. It is hypothesised that narrow niche breadths and restricted geographic ranges in the tropics allow more species to coexist with minimal overlap, relative to high-latitude regions. Although a wealth of studies have investigated these questions across different regions and taxonomic groups, these have consistently yielded contradictory results, leading to the continued persistence of numerous ecological explanations. Here, using a global occurrence database containing over 100,000 plant species, we provide the first globally standardised investigation into the geographic relationships among latitudinal range, environmental breath, and latitudinal median. We find limited evidence for a global latitudinal gradient in species’ ranges and environmental breadths, with results varying between hemispheres and along latitude within each hemisphere. In agreement with previous observations, we show consistent support for a latitudinal gradient in environmental breadth and latitudinal range, but only for trees in the northern hemisphere and for tropical species. In the southern hemisphere, conversely, these trends are inverted for non-tropical species, with latitudinal range and environmental breadth decreasing with distance from the equator. Moreover, these relationships are even weaker with environmental breadth, even though there is a strong relationship between environmental breadth and latitudinal range. By applying standardised methods at the global scale, these results illustrate that variation in species’ ranges is largely a by-product of biogeographic patterns rather than niche processes. Collectively, this work suggests that existing ecological “rules” linking niche breadth to latitude predominantly reflect regional sampling biases and a historical focus on the northern hemisphere and certain taxonomic groups.

Sexual reproduction, despite its associated costs and risks, is prevalent among many organisms, presumably to generate and maintain genetic diversity. This diversity is vital for adapting to environmental changes and combating natural enemies. Paradoxically, several clonal species also exhibit high genetic diversity. One theory for the maintenance of this genetic diversity is frequency-dependent selection, which favors rare genotypes over common ones, limiting the extent and dominance of a single clone, thereby preserving genetic diversity. Empirical evidence for this theory under natural conditions is sparse. Twelve years ago, we established in the forest fourteen genetically diverse plots where all plants had a unique genotype (rare genotypes) and paired with them clonal plots where all plants had the same genotype (common genotypes) to test whether common genotypes have a disadvantage and frequency-dependent selection is in action. Clones were created from cuttings from Piper cordulatum, a naturally clonally reproducing understory plant. We aimed to test if common genotypes are disadvantaged and if frequency-dependent selection is effective. Over the experiment's first ten years, herbivory, pathogen attacks, and plant size remained similar across both genotype categories. Intriguingly, clones exhibited superior survival during the initial five years. Survival rates equalize for rare and common genotypes by the decade's end. By year twelve, survival remained similar for rare and common genotypes. However, modeled survival projections based on the twelve-year-long trend suggest that common genotypes might experience increased mortality in the long run, consistent with the hypothesis of negative frequency-dependent selection. Moreover, plants in clonal plots exhibited lower fitness in terms of infructescence production at the plot level by the tenth year. Our findings suggest that having low genetic diversity in the neighborhood does not increase disease or herbivory susceptibility or reduce short-term survival. The impact of negative frequency-dependent selection is not immediate. However, it could eventually restrict the survival and reproduction of Piper clones in a tropical forest's understory, curbing the dominance of any single genotype and potentially enhancing population-wide genetic diversity.