Reproductive and environmental traits explain the variation in egg size among Medusozoa (Cnidaria)

Medusozoa (Cnidaria) are characterized by diverse life cycles, with different semaphoronts (medusa, medusoid, fixed gonophore, polyp) representing the sexual phase and carrying the gametes. Although egg size is often considered a proxy to understand reproductive and developmental traits of medusozoans, understanding of the processes influencing egg size variation in the group under an evolutionary context is still limited. We carried out a comprehensive review of the variation of egg size in Medusozoa to test whether this variation is related to biological/sexual or environmental traits. Egg size presents a strong phylogenetic signal (λ = 0.79, K = 0.67), explaining why closely related species with different reproductive strategies and different individual sizes have similar egg sizes. However, variation in egg size is influenced by the number of eggs, depth and temperature, with larger eggs frequently present in species with few eggs (1-15), in deep-sea species and in cold-water species. Conversely, the production of small eggs among cold-water species of Staurozoa might be associated with the development of a small benthic larvae in this group. Our study reinforces that egg sizes respond to reproductive and environmental traits, although egg size is highly conserved within medusa classes.

Considering landscape-level processes in ecosystem service assessments

The provision of ecosystem services is inherently spatial. Landscape structure affects service provision through multiple landscape-level processes, such as fragmentation, edge and connectivity effects. These processes can affect areas of ecosystem service supply and demand, and the flows linking those areas. Despite the emergence of sophisticated spatial ecosystem service assessments in the last two decades, we show through a literature review that landscape-level processes are still rarely considered in a comprehensive way. Even when they are considered, landscape effects are mostly limited to landscape composition, and configuration effects are underrepresented. Furthermore, most studies infer ecosystem service provision by only evaluating supply, ignoring demand and flows. Here we present a simple conceptual framework that illustrates how to incorporate landscape-level processes in the assessment of the different components of the service provision chain (supply, demand and flows). Using simulations, we evaluated how estimations of ecosystem service provision change when considering different landscape processes and discussed the implications of disregarding landscape effects. However, to fully implement the framework, a series of challenges linked to mapping and quantifying supply and demand, defining adequate scales of analysis, measuring flows, and parameterizing models for different types of services, still need to be overcome. To promote an adequate use and management of ecosystem services, it is essential to better incorporate landscape processes in ecosystem service assessments. This will lead to more quantitatively accurate and spatially precise estimates.

Beekeeping practices and geographic distance, not land use, drive gene flow across tropical bees

Across the globe, wild bees are threatened by ongoing natural habitat loss, risking the maintenance of plant biodiversity and agricultural production. Despite the ecological and economic importance of wild bees and the fact that several species are now managed for pollination services worldwide, little is known about how land use and beekeeping practices jointly influence gene flow. Using stingless bees as a model system, containing wild and managed species that are presumed to be particularly susceptible to habitat degradation, here we examine the main drivers of tropical bee gene flow. We employ a novel landscape genetic approach to analyse data from 135 populations of 17 stingless bee species distributed across diverse tropical biomes within the Americas. Our work has important methodological implications, as we illustrate how a maximum-likelihood approach can be applied in a meta-analysis framework to account for multiple factors, and weight estimates by sample size. In contrast to previously held beliefs, gene flow was not related to body size or deforestation, and isolation by geographic distance (IBD) was significantly affected by management, with managed species exhibiting a weaker IBD than wild ones. Our study thus reveals the critical importance of beekeeping practices in shaping the patterns of genetic differentiation across bee species. Additionally, our results show that many stingless bee species maintain high gene flow across heterogeneous landscapes. We suggest that future efforts to preserve wild tropical bees should focus on regulating beekeeping practices to maintain natural gene flow and enhancing pollinator-friendly habitats, prioritizing species showing a limited dispersal ability.