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Global change has become a central focus of modern biology. Yet, our knowledge of how anthropogenic drivers affect biodiversity and natural resources is limited by a lack of biological data spanning the Anthropocene. We propose that the hundreds of millions of plant, fungal and animal specimens deposited in natural history museums have the potential to transform the field of global change biology. We suggest that museum specimens are underused, particularly in ecological studies, given their capacity to reveal patterns that are not observable from other data sources. Increasingly, museum specimens are becoming mobilized online, providing unparalleled access to physiological, ecological and evolutionary data spanning decades and sometimes centuries. Here, we describe the diversity of collections data archived in museums and provide an overview of the diverse uses and applications of these data as discussed in the accompanying collection of papers within this theme issue. As these unparalleled resources are under threat owing to budget cuts and other institutional pressures, we aim to shed light on the unique discoveries that are possible in museums and, thus, the singular value of natural history collections in a period of rapid change.This article is part of the theme issue 'Biological collections for understanding biodiversity in the Anthropocene'.

Aim: During its entire history, the Earth has gone through periods of climate change similar in scale and pace to the warming trend observed today in the Anthropocene. The impact of these ancient climatic events on the evolutionary trajectories of organisms provides clues on the organismal response to climate change, including extinction, migration and persistence. Here, we examine the evolutionary response to climate cooling/warming events of the clusioid families Calophyllaceae, Podostemaceae and Hypericaceae (CPH clade) and the genus Hypericum as test cases. Location: Holarctic. Time period: Late Cretaceous–Cenozoic. Major taxa studied: Angiosperms. Methods: We use palaeoclimate simulations, species distribution models and phylogenetic com- parative approaches calibrated with fossils. Results: Ancestral CPH lineages could have been distributed in the Holarctic 100 Ma, occupying tropical subhumid assemblages, a finding supported by the fossil record. Expansion to closed- canopy tropical rain forest habitats occurred after 60 Ma, in the Cenozoic, in agreement with ear- lier ideas of a post-Cretaceous origin of current tropical rain forest. Posterior Cooling during the Eocene triggered diversification declines in CPH tropical lineages, and was associated with a cli- matic shift towards temperate affinities in Hypericum. Hypericum subsequently migrated to tropical mountains, where it encountered different temperate conditions than in the Holarctic. Main conclusions: We hypothesize that most clusioid CPH lineages failed to adapt to temperate regimes during periods of Cenozoic climate change, and went extinct in the Holarctic. In contrast, boreotropical descendants including Hypericum that underwent niche evolution demonstrated selective advantages as climates became colder. Our results point toward macroevolutionary tra- jectories involving the altering fates of closely related clades that adapt to periods of global climate change versus those that do not. Moreover, t

Aim: During its entire history, the Earth has gone through periods of climate change similar in scale and pace to the warming trend observed today in the Anthropocene. The impact of these ancient climatic events on the evolutionary trajectories of organisms provides clues on the organismal response to climate change, including extinction, migration and persistence. Here, we examine the evolutionary response to climate cooling/warming events of the clusioid families Calophyllaceae, Podostemaceae and Hypericaceae (CPH clade) and the genus Hypericum as test cases. Location: Holarctic. Time period: Late Cretaceous–Cenozoic. Major taxa studied: Angiosperms. Methods: We use palaeoclimate simulations, species distribution models and phylogenetic comparative approaches calibrated with fossils. Results: Ancestral CPH lineages could have been distributed in the Holarctic 100 Ma, occupying tropical subhumid assemblages, a finding supported by the fossil record. Expansion to closed-canopy tropical rain forest habitats occurred after 60 Ma, in the Cenozoic, in agreement with earlier ideas of a post-Cretaceous origin of current tropical rain forest. Posterior Cooling during the Eocene triggered diversification declines in CPH tropical lineages, and was associated with a climatic shift towards temperate affinities in Hypericum. Hypericum subsequently migrated to tropical mountains, where it encountered different temperate conditions than in the Holarctic. Main conclusions: We hypothesize that most clusioid CPH lineages failed to adapt to temperate regimes during periods of Cenozoic climate change, and went extinct in the Holarctic. In contrast, boreotropical descendants including Hypericum that underwent niche evolution demonstrated selective advantages as climates became colder. Our results point toward macroevolutionary trajectories involving the altering fates of closely related clades that adapt to periods of global climate change versus those that do not. Moreover, they sugge

Background and Aims Malpighiales are one of the largest angiosperm orders and have undergone radical systematic restructuring based on molecular phylogenetic studies. The clade has been recalcitrant to molecular phylogenetic reconstruction, but has become much more resolved at the suprafamilial level. It now contains so many newly identified clades that there is an urgent need for comparative studies to understand their structure, biology and evolution. This is especially true because the order contains a disproportionally large diversity of rain forest species and includes numerous agriculturally important plants. This study is a first broad systematic step in this endeavour. It focuses on a comparative structural overview of the flowers across all recently identified suprafamilial clades of Malpighiales, and points towards areas that desperately need attention. Methods The phylogenetic comparative analysis of floral structure for the order is based on our previously published studies on four suprafamilial clades of Malpighiales, including also four related rosid orders (Celastrales, Crossosomatales, Cucurbitales, Oxalidales). In addition, the results are compiled from a survey of over 3000 publications on macrosystematics, floral structure and embryology across all orders of the core eudicots. Key Results Most new suprafamilial clades within Malpighiales are well supported by floral structural features. Inner morphological structures of the gynoecium (i.e. stigmatic lobes, inner shape of the locules, placentation, presence of obturators) and ovules (i.e. structure of the nucellus, thickness of the integuments, presence of vascular bundles in the integuments, presence of an endothelium in the inner integument) appear to be especially suitable for characterizing suprafamilial clades within Malpighiales. Conclusions Although the current phylogenetic reconstruction of Malpighiales is much improved compared with earlier versions, it is incomplete, and further focused p