(American Journal of Botany. 2003;90:0.)
© 2003 Botanical Society of America, Inc.
Carnivorous plant evolution
Whether of the snap-trap or flypaper type, carnivorous plants have been intriguing humans for a long time for many reasons. In this issue Rivadavia et al. decode some of the mystery with a robust phylogenetic analysis of a thorough sampling of the Droseraceae. The rbcL chloroplast gene data show that Drosera originated in Africa or Australia and that Australian species expanded their distribution to South America and then Africa. Combining rbcL and 18S rDNA sequence data, the authors conclude that all Drosera with active flypaper traps form a clade sister to a snap trap clade including Dionaea and Aldrovanda, suggesting that the snap traps of Dionaea and Aldrovanda are homologous despite their morphological differences.
(see p. 123)
Sanzol, Rallo, and Herrero describe, for the first time, stigmatic asynchrony in a flowering plant species. Their data show that in the pentacarpellar Pyrus communis (pear) different carpels within a flower mature and degenerate asynchronously. They hypothesize that this carpellar relay system maximizes pollination efficiency and may explain why more than 89% of recent flowering plant species have more than one carpel.
(see p. 78)
Two articles in this issue highlight the grass family. Michelangeli, Davis, and Stevenson's study resolves the small Australian endemic family Ecdeiocoleaceae as sister to the grasses, instead of Joinvilleaceae as has been previously suggested. Ingram and Doyle's work on tef (Eragrostis tef), an important cereal crop for Ethiopians, identifies E. pilosa, a weedy grass found throughout the world in tropical and subtropical regions, as the direct progenitor of this understudied crop species.(see
p. 93
and
p. 116
)
How plants respond to variation in more than one essential nutrient is addressed by Rubio, Zhu, and Lynch in a study using the aquatic plant Lemna minor. They draw on two prevailing theories to frame their work: ``Liebig's law'' or ``the law of the minimum,'' dating from Sprengel's 1828 formulation, states that plant growth is limited by the resource in the shortest supply, while ``the multiple limitation hypothesis,'' favored by current ecological theory, proposes that plant growth is limited by all resources simultaneously. However, the ``undefined'' emerges as an equal contender in predicting plant response to resource availability.
(see p. 143)
