(American Journal of Botany. ;90:0.)
© Botanical Society of America, Inc.
A very interesting biological system
Lara and Ornelas contribute to the area of exploitation of plant-animal mutualisms with a 4-yr study describing how the fungus Fusarium moniliforme modifies the plant-pollinator interaction between the tropical gesneriad Moussonia deppeana and its hummingbird pollinator. Among the results, they found that infected plants remained infected year after year and produced more flowers with longer life spans than uninfected plants, infected plants produced both infected and uninfected flowers, and hummingbirds visited more flowers on diseased plants than healthy ones.
(see p. 262)
Stilwell et al. track genetic changes in American chestnut (Castanea dentata) populations that have occurred since the blight pandemic killed approximately 3.5 billion trees about 100 years ago. The fungus responsible girdles the stem, killing the vascular cambium, but does not invade the roots. The once dominant canopy tree is now a clonal understory shrub, reproducing vegetatively from shoots sprouting from the root collar. Their study found evidence of selection favoring heterozygosity. This data will be valuable for assessing how that heterozygote advantage is affected should the American chestnut ever return to sexual reproduction. Given the apparent heterozygosity advantage, conservation efforts should strive to preserve the natural genetic variation to prevent a further decline in the ability of American chestnut to respond to selection pressures.
(see p. 207)
The genus Clarkia has been the subject of intense evolutionary study for more than half a century. In this paper Ford and Gottlieb present an excellent analysis of the phylogenetic implications of sequence variation at loci coding the cytosolic form of phosphoglucose isomerase. The study provides significant and surprising new insight into phylogenetic relationships in one of the most evolutionarily significant sections in the genus and an excellent example of how variation at duplicate loci can be used to address phylogenetic hypotheses.
(see p. 284)
Diverse, strange, and unorthodox morphologies characterize the southeast Asian Epithemateae, a tribe of the Gesneriaceae. These morphologies include the unifoliate habit of Monophyllaea (see cover), mixture of solitary and opposite leaves in Epithema, sympodial plant architecture, anisophylly, alterniphylly, and more. Mayer et al. use plastid DNA markers to clarify the systematic position and the generic relationships of this critical tribe in the Gesneriaceae.
(see p. 321)
