Latitudinal gradients in seed predation persist in urbanized environments.

Urbanization is creating a new global biome, in which cities and suburbs around the world often resemble each other more than the local natural areas they replaced. But while urbanization can profoundly affect ecology at local scales, we know little about whether it disrupts large-scale ecological patterns. Here we test whether urbanization disrupts a macroecological pattern central to ecological and evolutionary theory: the increase in seed predation intensity from high to low latitudes. Across 14,000 km of latitude spanning the Americas, we compared predation intensity on two species of standardized experimental seeds in urbanized and natural areas. In natural areas, predation on both seed species increased fivefold from high latitudes to the tropics, one of the strongest latitudinal gradients in species interactions documented so far. Surprisingly, latitudinal gradients in predation were equally strong in urbanized areas despite significant habitat modification. Nevertheless, urbanization did affect seed predation. Compared with natural areas, urbanization reduced overall predation and vertebrate predation, did not affect predation by invertebrates in general, and increased predation by ants. Our results show that macroecological patterns in predation intensity can persist in urbanized environments, even as urbanization alters the relative importance of predators and potentially the evolutionary trajectory of urban populations.

Two orthogonal differentiation gradients locally coordinate fruit morphogenesis.

Morphogenesis requires the coordination of cellular behaviors along developmental axes. In plants, gradients of growth and differentiation are typically established along a single longitudinal primordium axis to control global organ shape. Yet, it remains unclear how these gradients are locally adjusted to regulate the formation of complex organs that consist of diverse tissue types. Here we combine quantitative live imaging at cellular resolution with genetics, and chemical treatments to understand the formation of Arabidopsis thaliana female reproductive organ (gynoecium). We show that, contrary to other aerial organs, gynoecium shape is determined by two orthogonal, time-shifted differentiation gradients. An early mediolateral gradient controls valve morphogenesis while a late, longitudinal gradient regulates style differentiation. Local, tissue-dependent action of these gradients serves to fine-tune the common developmental program governing organ morphogenesis to ensure the specialized function of the gynoecium.

Studying flowers in 3D using photogrammetry.

Flowers are intricate and integrated three-dimensional (3D) structures predominantly studied in 2D due to the difficulty in quantitatively characterising their morphology in 3D. Given the recent development of analytical methods for high-dimensional data, the reconstruction of flower models in three dimensions represents the limiting factor to studying flowers in 3D. We developed a floral photogrammetry protocol to reconstruct 3D models of flowers based on images taken with a digital single-lens reflex camera, a turntable and a portable lightbox. We demonstrate that photogrammetry allows a rapid and accurate reconstruction of 3D models of flowers from 2D images. It can reconstruct all visible parts of flowers and has the advantage of keeping colour information. We illustrated its use by studying the shape and colour of 18 Gesneriaceae species. Photogrammetry is an affordable alternative to micro-computed tomography (micro-CT) that requires minimal investment and equipment, allowing it to be used directly in the field. It has the potential to stimulate research on the evolution and ecology of flowers by providing a simple way to access 3D morphological data from a variety of flower types.