We examined the responses of an allergenic species, western ragweed (Ambrosia psilostachya DC.), to experimental warming and clipping. The experiment was conducted in a tallgrass prairie in Oklahoma, USA, between 1999 and 2001. Warming increased ragweed stems by 88% when not clipped and 46% when clipped. Clipping increased ragweed stems by 75% and 36% in the control and warmed plots, respective...

A new species of aphid, belonging to the genus Macrosiphoniella Del Guercio, 1911, is described using three samples collected in Iran on Helichrysum armenium (Asteraceae, Inuleae) by the late Prof. G. Remaudière. Both apterous and alate viviparous females of the new taxon, Macrosiphoniella remaudiereisp. n., are described and compared to corresponding morphs of the closely allied Macrosiphoniel...

The sunflower alliance of families comprises nearly 10% of all flowering plant species and includes the largest of all plant families, the sunflower family Asteraceae, which has 23,000 species, and the bellflower family Campanulaceae. Both are worldwide in distribution, but the majority of their species occur in the northern hemisphere. Recently it has been shown that a number of small, woody f...

Isocarpha comprises five species ranging from southern Texas and the Bahamas to northern Peru and northeastern Brazil. The genus belongs in Eupatorieae rather than Heliantheae, but structure of the head of Isocarpha with its elongate, chaffy receptacle is anomalous within Eupatorieae. An hypothesis is presented suggesting the evolutionary derivation of this type of head through formation of flo...