Summary Climate warming is leading to earlier budburst and therefore an increased risk of spring frost injury to young leaves. But to what extent are second‐cohort leaves, which trees put out after leaf‐killing frosts, able to compensate incurred losses? To investigate whether second‐cohort leaves behave differently from first‐cohort leaves, we exposed saplings of beech (Fagus sylvatica), oak (Quercus robur), and honeysuckle (Lonicera xylosteum) to experimental treatments mimicking either a warm spring or a warm spring with a leaf‐killing frost. Refoliation took 48, 43, and 36 d for beech, oak and honeysuckle, respectively. In beech and oak, autumn Chl content and photosynthesis rates were higher in second‐ than in first‐cohort leaves, senescence in second‐cohort leaves occurred c. 2‐wk‐later, and autumn bud growth in beech was elevated 66% in frost‐damaged plants compared with the warm spring treatment. No differences in autumn phenology and growth were observed for honeysuckle. Overall, in beech and oak, delayed Chl breakdown in second‐cohort leaves mitigated 31% and 25%, respectively, of the deficit in growing‐season length incurred by spring frost damage. These results reveal an unexpected ability of second‐cohort leaves of beech and oak to compensate for spring frost damage, and demonstrate that long‐lived trees vary their autumnal phenology depending on preceding productivity.

On the basis of outgroup comparison, 2n = 18 is the ancestral number, and repeated chromosomal fusions with simultaneous genome size increase as a result of repetitive elements accumulating near centromeres characterize the papaya clade. These results have implications for ongoing genome assemblies in Caricaceae.

We analysed plant collecting in Germany between 1826 and 2014 by counting specimens of common, rare, and invasive species deposited in the herbaria of Munich during that period. Plant collecting increased in the late 1940s and continued until the mid-1980s, but has since declined to levels similar to 1900. In spite of the decline in collecting, the number of specimens of invasive species has strongly increased. The only other attempt to analyse botanical collecting in a large European region, an analysis of botanical recording in the British Isles 1836 to 1988, did not find a decline by the mid-1980s. For the United States, an analysis of collecting between the 1890s and 1999 found that it peaked in the 1930s. Museum time-series (representing the same species collected at different times) have been integral to identifying temporal responses to environmental change, for example, changed flowering times in response to an earlier onset of spring and the change of a region's floristic composition. A possible way to combat the likely loss of time-series in European herbaria is for collection personal to engage with biology teachers at high schools and universities to encourage the collecting of local plants as part of courses in the life sciences.

BackgroundWith some 700 species, the pantropical Crotalaria is among the angiosperm’s largest genera. We sampled 48% of the species from all sections (and representatives of the 15 remaining Crotalarieae genera) for nuclear and plastid DNA markers to infer changes in climate niches, flower morphology, leaf type, and chromosome numbers.Results Crotalaria is monophyletic and most closely related to African Bolusia (five species) from which it diverged 23 to 30 Ma ago. Ancestral state reconstructions reveal that leaf and flower types are conserved in large clades and that leaf type is uncorrelated to climate as assessed with phylogenetically-informed analyses that related compound vs. simple leaves to the mean values of four Bioclim parameters for 183 species with good occurrence data. Most species occur in open habitats <1000 m alt., and trifoliolate leaves are the ancestral condition, from which unifoliolate and simple leaves each evolved a few times, the former predominantly in humid, the latter mainly in dry climates. Based on chromosome counts for 36% of the 338 sequenced species, most polyploids are tetraploid and belong to a neotropical clade.ConclusionsAn unexpected finding of our study is that in Crotalaria, simple leaves predominate in humid climates and compound leaves in dry climates, which points to a different adaptive value of these morphologies, regardless of whether these two leaf types evolved rarely or frequently in our focal group.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-017-0903-5) contains supplementary material, which is available to authorized users.

As part of a revision of the species of Crotalaria L. (Papilionoideae, Crotalarieae) occurring in Brazil, eleven lectotypifications are proposed for: Crotalaria acutiflora Benth., Crotalaria depauperata Mart. ex Benth., Crotalaria holosericea Nees & Mart., Crotalaria holosericea var. grisea Benth., Crotalaria laeta Mart. ex Benth., Crotalaria leptophylla Benth., Crotalaria rufipila Benth., Crotalaria unifoliolata Benth., Crotalaria vitellina Ker-Gawl., Crotalaria vitellina var. glabrata Benth., and Crotalaria vitellina var. minor Benth. Four new synonyms are also proposed.