Vestured pits: a diagnostic character in the secondary xylem of Myrtales

Vestures are small projections from the secondary cell wall associated with tracheary elements of the secondary xylem. They are usually associated with bordered pits and characterize various angiosperm families, including important timber species such as Dipterocarpaceae and Eucalyptus trees. The micromorphology and distribution of vestures were studied in 22 species representing all families within the order Myrtales based on light and scanning electron microscopy. Vestures are consistently present near the outer pit aperture of bordered vessel pits, suggesting the synapomorphic character of this feature for the entire order. It is unclear in which geological period this feature originated in the evolution of the pre-Myrtalean lineages. In some species vestures are associated with inner pit apertures, inner vessel walls, si

Systematic palynology in Ebenaceae with focus on Ebenoideae: Morphological diversity and character evolution

This study examines the diversity and character transformations in pollen and orbicule morphology of Ebenaceae, with a focus on subfamily Ebenoideae (ca. 600 sp.). 62 specimens comprising all three genera of Ebenoideae (Diospyos, Euclea, Royena), were studied using LM and SEM. Bayesian phylogenetic analysis was performed on molecular sequence data to establish an evolutionary hypothesis that was then used as an evolutionary framework to identify synapomorphies and trace evolutionary trends of palynological data with Bayesian posterior mapping and principle component analyses (PCA). Ebenoideae pollen is generally shed as monads (permanent tetrads in two species), medium-sized, prolate-spheroidal to subprolate and tricolporate. A substantial amount of variation is found in pollen size, equatorial outline (lobate, subtriangular, circular and hexagonal) and sexine ornamentation type ((micro)rugulate, striate, granulate and gemmate). Moreover, orbicules were present on the inner locule wall in all specimens examined. Their abundance, degree of fusion with tapetal membrane and aggregation vary considerably. We can conclude that Ebenaceae pollen is more heterogeneous than previously assumed. We traced palynological synapomorphies for groups at different taxonomic levels: subfamily level (pollen size, pollen wall stratification and aperture morphology), generic level (size, equatorial outline and sexine ornamentation types) and subgeneric clades (size, ectocolpus morphology, equatorial outline and sexine ornamentation subtypes) respectively. The granular infratectum and the unique sculpturing pattern on the orbicule walls are the most discriminating pollen features for subfamily Ebenoideae. (c) 2008 Elsevier B.V. All rights reserved.status: publishe

Climate warning results in phenotypic and evolutionary changes in spring events: a mini review

The impact of climate change, in particular increasing spring temperatures, on life-cycle events of plants and animals has gained scientific attention in recent years. Leafing of trees, appearance and abundance of insects, and migration of birds, across a range of species and countries, have been cited as phenotrends that are advancing in response to warmer spring temperatures. The ability of organisms to acclimate to variations in environmental conditions is known as phenotypic plasticity. Plasticity allows organisms to time developmental stages to coincide with optimum availability of environmental resources. There may, however, come a time when the limit of this plasticity is reached and the species needs to adapt genetically to survive. Here we discuss evidence of the impact of climate warming on plant, insect and bird phenology through examination of: (1) phenotypic plasticity in (a) bud burst in trees, (b) appearance of insects and (c) migration of birds; and (2) genetic adaptation in (a) gene expression during bud burst in trees, (b) the timing of occurrence of phenological events in insects and (c) arrival and breeding times of migratory birds. Finally, we summarise the potential consequences of future climatic changes for plant, insect and bird phenolog

Surviving in a warmer world: environmental and genetic responses

There are numerous reports in the literature of advancing trends in phenophases of plants, insects and birds attributed to rising temperature resulting from human-driven climate warming. One mechanism that enables a population to respond rapidly to changes in the environment is termed phenotypic plasticity. This plasticity grants a degree of flexibility to enable the timing of developmental stages to coincide with resource availability. If, however, environmental conditions exceed the plastic limits of an organism, evolutionary change may be necessary in order to ensure continued survival of their populations. We review evidence for phenotypic plasticity and genetic adaptation in phenological characteristics associated with climatic warming. We focus this review on examples from trees, insects and birds. We found many reports of direct observations of phenotypic plasticity but fewer studies providing conclusive evidence of genetic adaptation. Evidence for changes in genes linked with adaptive traits associated with a warming climate was stronger in insects, that have a relatively short life-cycle, than in longer-lived birds and trees. Further research is required to identify both appropriate long-term data sets for a range of species and traits and suitable analytical methods, which will permit the study of the complex interaction between phenotypic plasticity and genetic adaptation of organisms and their populations in response to climatic change