Summary• Paleobotanists have long used models based on leaf size and shape to reconstruct paleoclimate. However, most models incorporate a single variable or use traits that are not physiologically or functionally linked to climate, limiting their predictive power. Further, they often underestimate paleotemperature relative to other proxies.• Here we quantify leaf-climate correlations from 92 globally distributed, climatically diverse sites, and explore potential confounding factors. Multiple linear regression models for mean annual temperature (MAT) and mean annual precipitation (MAP) are developed and applied to nine well-studied fossil floras.• We find that leaves in cold climates typically have larger, more numerous teeth, and are more highly dissected. Leaf habit (deciduous vs evergreen), local water availability, and phylogenetic history all affect these relationships. Leaves in wet climates are larger and have fewer, smaller teeth. Our multivariate MAT and MAP models offer moderate improvements in precision over univariate approaches (± 4.0 vs 4.8°C for MAT) and strong improvements in accuracy. For example, our provisional MAT estimates for most North American fossil floras are considerably warmer and in better agreement with independent paleoclimate evidence.• Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions. This work also illustrates the need for better understanding of the impact of phylogeny and leaf habit on leaf-climate relationships.

We investigated responses of growth, leaf gas exchange, carbon-isotope discrimination, and whole-plant water-use efficiency (W P ) to elevated CO 2 concentration ([CO 2 ]) in seedlings of five leguminous and five nonleguminous tropical tree species. Plants were grown at CO 2 partial pressures of 40 and 70 Pa. As a group, legumes did not differ from nonlegumes in growth response to elevated [CO 2 ]. The mean ratio of final plant dry mass at elevated to ambient [CO 2 ] (M E /M A ) was 1.32 and 1.24 for legumes and nonlegumes, respectively. However, there was large variation in M E /M A among legume species (0.92-2.35), whereas nonlegumes varied much less (1.21-1.29). Variation among legume species in M E /M A was closely correlated with their capacity for nodule formation, as expressed by nodule mass ratio, the dry mass of nodules for a given plant dry mass. W P increased markedly in response to elevated [CO 2 ] in all species. The ratio of intercellular to ambient CO 2 partial pressures during photosynthesis remained approximately constant at ambient and elevated [CO 2 ], as did carbon isotope discrimination, suggesting that W P should increase proportionally for a given increase in atmospheric [CO 2 ]. These results suggest that tree legumes with a strong capacity for nodule formation could have a competitive advantage in tropical forests as atmospheric [CO 2 ] rises and that the water-use efficiency of tropical tree species will increase under elevated [CO 2 ].

Although Rhamnaceae are distributed worldwide today, the former hypothesis for its Laurasian origins may need to be reconsidered in view of recently discovered fossils from the Guaduas Formation of central Colombia (∼68 Ma), including fossil leaves (Berhamniphyllum) and a fruit (Archaeopaliurus boyacensis). Recent phylogenetic studies calibrate the stem of Rhamnaceae at 64 Ma and divide the family into three groups, rhamnoid, ampeloziziphoid, and ziziphoid. Although the fruit, Archaeopaliurus boyacensis, resembles that of Paliurus and suggests a relationship to the Paliureae in the ziziphoid group, associated leaves of Berhamniphyllum conform in architecture to those found today only in the Rhamneae tribe. The Maastrichtian age of these fossils predates the ages previously estimated for the Rhamneae tribe (28.5 Ma) and the Paliureae tribe (31.6 Ma) using a modified clock approach. Based on the new megafossil evidence, two alternative ideas are proposed: (1) that these fossils predate the extant tribes or (2) that the family diversified into modern tribes earlier than previously proposed.

In the search for antiparasite compounds from the Colombian flora, an active compound against Leishmania (Viannia) panamensis amastigotes was isolated from the fungi Pycnoporus sanguineus. The structural elucid-ation was achieved with spectroscopic methods ((1)H and (13)C NMR and MS). This compound was identified as ergosterol 5,8-endoperoxide.