(American Journal of Botany. ;90:0.)
© Botanical Society of America, Inc.
Understanding invasive genotypes
Py
ek et al. address an interesting and important problem regarding hybridization and the biology of invasions. It is one of the few empirical investigations that correlate "regeneration" success through clonal growth with invasion successes in the field. They studied two Asian Reynoutria (Polygonaceae) species and their hybrid, which are notorious invaders of riverside and temperate forest habitats in central Europe. The authors sampled hybrid clones from the field and documented a significant fitness variation (and allozyme variation) in a hybrid taxon that was originally thought to be rarely generated. The regeneration data presented by the authors should be of broad use to those interested in predicting the spread of invaders.
(see p. 1487)
Cane and Schiffhauer present a well-designed study that represents a major advancement in the interpretation of pollinator efficacy and pollination factors affecting the cranberry, Vaccinium macrocarpon (Ericaceae). Through manual pollinations with incremental doses of pollen, they developed predictive curvilinear relationships between stigmatic pollen loads and fruit set, and fruit size and seed count. They then studied the pollination efficacies of four different bee species in the field and contrasted the traditional method for comparing pollinator efficacies with the estimated yields of fruits and seeds calculated from the predictive regression equations developed in the manual pollination experiment. Further, they suggest shortcuts for extending their calculations to other systems.
(see p. 1425)
How has plant water supply (stem) evolved to meet demand (leaf)? Preston and Ackerly make a convincing case that the allometric relationship between leaf area and stem hydraulic capacity has itself been selected for, rather than its separate components in isolation. Using a paired comparison approach involving six species pairs representing three genera, the authors tested relative stem-to-leaf area relationships of these species in drier to moister habitats. They discuss their evidence for repeated evolutionary divergences in these relationships associated with water availability, and the benefits of comparing phylogenetically paired species.
(see p. 1502)
Reviewers noted several important features of Antonovics et al.'s study on the distribution of anther-smut disease (Microbotryum violaceum) and Silene species in the eastern United States as inferred from herbarium records. First, field biologists are often limited in the scale at which they can study spatial processes (they can't work in all locations) and temporal processes (even a five-year study of a system is unusual). This paper illustrates how herbarium records can be used to provide quantitative insights on both these issues, despite the inevitable variation in collection intensity at different times and for different species. Second, the paper provides specific information on how the distributions of this disease and its hosts have changed over the last century. Such information is extremely limited for pathogens of non-agricultural plants. Above all this herbarium-based study highlights the importance of preserving and collating the information present in historical collections, as well as developing new quantitative techniques for its analysis.
(see p. 1522)
