Catherine H. Graham

Global plant diversity is distributed unevenly across terrestrial biomes. While the effects of environmental differences on species distributions have been well studied, how the spatial configuration of biomes structures the macroevolutionary assembly of the global flora remains unclear. Here, we introduce a biome-centred framework for elucidating global floristic assembly based on joint reconstructions of biome and geographic occupancy across 160 plant lineages comprising ~20,000 species. We demonstrate that global plant diversity is assembled predominantly through within-biome speciation (~86% of variation in biome-level plant richness) rather than biome shifts (~12%), revealing pervasive phylogenetic biome conservatism. Transitions among biomes are asymmetric and jointly governed by their biogeographic configurations and evolutionary histories: species-rich biomes with deeper evolutionary histories act as major evolutionary sources that disproportionately export lineages to other biomes, with biotic interchange increasing with biome area and declining with geographic and environmental distance. These results identify biomes as fundamental evolutionary arenas that both constrain diversification and mediate the biotic exchange of plant lineages, providing an integrative framework for understanding the spatiotemporal dynamics of global plant diversity.

Understanding biodiversity patterns requires integrating information across the interrelated dimensions that organize life. Species occupy specific regions in geographic space, respond to environmental conditions and vary within attribute (or trait) spaces that are shaped by their ecological and evolutionary histories. However, most analyses address these dimensions independently, limiting our ability to understand how constraints in one space interrelate to patterns in another. Developing approaches that explicitly quantify and connect the geometry of these spaces should unify the study of biodiversity across scales and dimensions. We implement such a framework in the letsR R package by constructing a triad of presence–absence matrices (PAMs) representing geographic, environmental and attribute spaces. A concise set of functions computes geometry‐aware descriptors such as centrality, frequency, isolation and border proximity, and allows these descriptors to be propagated among spaces through explicit connectors. This design builds on the letsR architecture and integrates with functions to facilitate macroecological analysis. Using global terrestrial mammals as a model group, we illustrate how descriptors derived from environmental space can be mapped back into geographic and attribute spaces. This approach reveals where particular regions of climatic space are common or rare, how isolated they are and how these properties influence species richness across dimensions. This novel implementation lowers the barrier to reproducible, geometry‐aware analyses and enables direct tests of how constraints in one space influence diversity in others, advancing a more integrated understanding of macroecological and macroevolutionary patterns.

Conservation planning requires prioritizing particular species, habitats, or objectives and handling information gaps. Spatial prioritization analyses apply various weighting schemes, for example assigning relative importance to different biodiversity features, balancing threatened and common species, or trading off ecological objectives against socioeconomic constraints. Such value driven choices may strongly affect conservation outcomes, yet little clarity exists on where and how they are employed. To address this opacity, we developed a comprehensive decision framework that organizes weighting criteria across three dimensions, conservation objectives, socioeconomic considerations, and implementation constraints, operating at species, habitat, and landscape levels. We then confronted 71 systematically chosen spatial prioritization studies with this framework to assess how weighting was considered. Representativeness and conservation urgency were the dominant motivations for weighting. However, ecosystem services were considered in only one study despite their prominence in policy-related discourse. Seventy-two percent of the studies did not explicitly justify their weighting decisions, challenging transparent communication of the underlying rationales. In a final step, we applied the framework in three case studies considering 1,472 species in Switzerland and prioritizing across taxonomic groups, realms, and threat categories to demonstrate the fundamental impact of weighting on conservation outcomes. Our results emphasize why weighting decisions require clear justification and documentation in spatial prioritization. Our framework will help planners make explicit choices that align with their conservation objectives.

Hummingbirds frequently feed on small volumes (NECTAR g _BODYMASS ⁻¹ _h ⁻¹ ), after which nectar consumption (and corresponding sucrose intake) decreased. Integrating maximum feeding rate with daily energy expenditure estimated from free‐living hummingbirds, we found most species could meet daily energy needs while feeding on dilute nectars, but there is an average dilution threshold (~7% sucrose). Hummingbirds may cope with energy deficits caused by variability in resources and competition with other nectarivores by adjusting their time spent foraging. Our models show that to meet average daily energetic needs, hummingbirds could feed ~2 h on concentrated nectars or an unattainable 19 h feeding on dilute nectars. We show that maximum feeding rates pose a physiological cap on hummingbirds' ability to use dilute nectars, which has implications for hummingbird survival and ultimately pollination. Thus, nectars provided by trochilophilous plants should be more concentrated than this dilution threshold. This mechanistic understanding may inform future work on the impacts of changes in flower phenology and nectar quality on hummingbirds. Read the free Plain Language Summary for this article on the Journal blog.

Aim: To determine how species richness gradients—commonly considered universal—vary across the phylogenetic hierarchy of birds and mammals, and to uncover how clade age and size predetermine the gradients. Location: Global. Time Period: Last 120 million years. Taxa Studied: Birds and mammals (~15,000 species). Methods: We used large‐scale phylogenies of birds and mammals and captured the species richness gradient for each of their monophyletic clades. Gradient strength was quantified with respect to latitude, environmental productivity and temperature using multiple measures (raw slopes, log transformation, log–log transformation, and correlations). To distinguish statistical from biological effects, we compared the observed gradients to those generated by null models that randomly reassigned species to clades while preserving the phylogeny and species distributions. Results: Species richness gradients show considerable variation. Small and young clades exhibited inconsistent gradients—including reverse or flat gradients—while older and larger clades converged on steep, consistent gradients. Even moderately large clades (~500 species) commonly displayed reverse gradients. Null models replicated this trend but only partially, implying that biological effects also drive gradient variation. These phylogenetic trends were sensitive to the choice of gradient measure: raw slopes frequently inflated the strength of this trend and the apparent differences among clades, while log and log–log transformations revealed only moderate trends. Main Conclusions: Species richness gradients are not universal, nor are they phylogenetic scale‐invariant. Instead, they follow systematic trends across the phylogenetic hierarchy. Young, small clades often bear signatures of their region of origin and historical dispersal, whereas older, larger clades converge on similar gradients. Recognising the variation and the phylogenetic trends within it elucidates the formation of biodiversity patterns. We offer guidelines for choosing gradient measures, arguing that multiple metrics, combined with careful use of null models, are necessary for a nuanced understanding of how, and why, global biodiversity patterns diverge from the presumed universal gradients.

Ecological communities result from complex species interactions, often summarized in interaction networks. The structure of these networks is described by metrics that provide insight into community assembly, ecosystem functioning and coevolutionary processes. Despite advances in measuring and mapping network structure, the mechanisms underlying its formation remain less explored. Network metrics may vary across communities owing to changes in species diversity and environmental conditions. However, network metrics may remain invariant if mechanisms influencing interactions (linkage rules) are independent of species composition and environmental conditions and instead influenced by traits. We investigated whether changes in taxonomic, phylogenetic and functional diversity along elevation gradients influence network modularity, nestedness, connectance and specialization across 32 sites in Brazil, Costa Rica and Ecuador. Despite elevation’s impact on diversity, we found that it had no effect on network structure, which remained consistent across elevations. Instead, trait-based mechanisms, specifically the matching between hummingbird bills and flower corollas, emerged as a consistent driver of network structure. Species showing strong trait matching contributed more to modularity and specialization, but less to nestedness and connectance than expected by chance. These results suggest that trait matching influences the invariant structure of plant–hummingbird networks, persisting despite shifts in diversity across biogeographical regions and elevational gradients.

Plant species pollinated by animals differ in the pool of visitors they attract. Some attract functionally similar animals, while others engage with a broader set of functionally distinct visitors; we term this species‐level variation functional generalism. Here, we explore the influence of plant traits and context‐dependent factors on functional generalism, and the potential effects of this overlooked aspect of mutualistic interactions on species' reproductive outcomes. We quantified functional generalism in 211 hummingbird‐visited plant species across 32 sites in three regions of Costa Rica, Ecuador and Brazil. We related functional generalism to plant traits (corolla length, opening, curvature) and context‐dependent factors, including the abundance and flowering duration of the focal plant species, as well as the functional diversity of co‐flowering plant species and of hummingbird pools during its flowering period. Finally, we assessed how functional generalism influenced plant reproductive outcomes (visitation rate and proportion of nectar‐robbing visits). Species with long, narrow corollas had the highest functional generalism, attracting more functionally diverse hummingbirds. Functional generalism increased in functionally diverse plant communities, highlighting the influence of neighbours within the same trophic level. Abundant species with short flowering periods had greater functional generalism than less abundant, continuously flowering species. Functional generalism had a hump‐shaped relationship with visitation rate, peaking at moderate levels but declining afterward. Moreover, the proportion of nectar‐robbing visits increased with functional generalism. These findings reveal the joint influence of plant traits and community context on functional generalism, which in turn affects plants' reproductive success. Read the free Plain Language Summary for this article on the Journal blog.

In pollination networks, indirect plant-plant interactions mediated by their shared pollinators, can shape community dynamics and species fitness; yet, the influence of floral traits on species roles remains unclear, particularly in diverse ecosystems like the tropical Andes. We studied hummingbird-mediated interactions among 31 flowering plants in three high-elevation shrubby habitats located in southern Ecuador. During August and November 2022, and January 2023, we collected stigma samples and constructed weighted interaction networks linked by heterospecific pollen grains. Species roles were determined by defining if they were overall donors or receptors of pollen. We also explored the association between the abundance of flowers and different floral traits and species roles. Finally, we assessed the potential influence of floral roles on species fitness by calculating the ratio of conspecific-to-heterospecific pollen grains observed in each species. We found that the identity of donor and receptor species was highly dynamic across sites and time. Donor species were characterized by being highly abundant, and having long and wide corollas, while receptor species had low abundance, and short and narrow corollas. Donor species received less heterospecific pollen than conspecific pollen, indicating that the pollen sharing roles of species could have fitness consequences. Our findings highlight the importance of floral traits and abundance in shaping floral roles and their potential fitness consequences in hummingbird-mediated indirect interactions.

Ecologists have long proposed that environments providing more energy can support more species, yet empirical evidence frequently contradicts this expectation. We argue that such inconsistencies result from confounding geographical influences that mask the true relationship between species richness and energy-related factors. Here, by comparing species richness across different climate conditions, we disentangle the direct effects of temperature, precipitation, and primary productivity from the confounding impacts of the area and isolation of various climates. Using a global analysis of terrestrial vertebrates, we reveal clear and consistent relationships between energy-related factors and species richness. Our findings clarify existing ecological theory and illustrate how adopting a climate space perspective advances biodiversity research, providing critical insights into biodiversity patterns and their responses to environmental change.