Search Results (2)

Gymnosperms are generally regarded as poor resprouters, especially when compared to angiosperms and particularly following major disturbance. However, is it this clear-cut? This review investigates two main aspects of gymnosperm resprouting: (i) various papers have provided exceptions to the above generalization—how frequent are these exceptions and are there any taxonomic trends?; and (ii) assuming gymnosperms are poor resprouters are there any anatomical or physiological reasons why this is the case? Five of six non-coniferous gymnosperm genera and 24 of 80 conifer genera had at least one species with a well-developed resprouting capability. This was a wider range than would be expected from the usual observation ‘gymnosperms are poor resprouters’. All conifer families had at least three resprouting genera, except the monospecific Sciadopityaceae. Apart from the aboveground stem, buds were also recorded arising from more specialised structures (e.g., lignotubers, tubers, burls and underground stems). In some larger genera it appeared that only a relatively small proportion of species were resprouters and often only when young. The poor resprouting performance of mature plants may stem from a high proportion of apparently ‘blank’ leaf axils. Axillary meristems have been recorded in a wide range of conifer species, but they often did not form an apical dome, leaf primordia or vascular connections. Buds or meristems that did form often abscised at an early stage. While this review has confirmed that conifers do not resprout to the same degree as angiosperms, it was found that a wide diversity of gymnosperm genera can recover vegetatively after substantial disturbance. Further structural studies are needed, especially of: (i) apparently blank leaf axils and the initial development of axillary meristems; (ii) specialised regeneration structures; and (iii) why high variability can occur in the resprouting capacity within species of a single genus and within genera of the same family. Full article

Research highlights: We present evidence indicating that covariation of functional traits among populations of a forest tree is not due to genetic constraints, but rather selective covariance arising from local adaptation to different facets of the climate, namely rainfall and temperature. Background and Aims: Traits frequently covary among natural populations. Such covariation can be caused by pleiotropy and/or linkage disequilibrium, but also may arise when the traits are genetically independent as a direct consequence of natural selection, drift, mutation and/or gene flow. Of particular interest are cases of selective covariance, where natural selection directly generates among-population covariance in a set of genetically independent traits. We here studied the causes of population-level covariation in two key traits in the Australian tree Eucalyptus pauciflora. Materials and Methods: We studied covariation in seedling lignotuber size and vegetative juvenility using 37 populations sampled from throughout the geographic and ecological ranges of E. pauciflora on the island of Tasmania. We integrated evidence from multiple sources: (i) comparison of patterns of trait covariation within and among populations; (ii) climate-trait modelling using machine-learning algorithms; and (iii) selection analysis linking trait variation to field growth in an arid environment. Results: We showed strong covariation among populations compared with the weak genetic correlation within populations for the focal traits. Population differentiation in these genetically independent traits was correlated with different home-site climate variables (lignotuber size with temperature; vegetative juvenility with rainfall), which spatially covaried. The role of selection in shaping the population differentiation in lignotuber size was supported by its relationship with fitness measured in the field. Conclusions: Our study highlights the multi-trait nature of adaptation likely to occur as tree species respond to spatial and temporal changes in climate. Full article