Janzen-Connell effects are negative effects on the survival of a plant's progeny at high conspecific densities or close to its conspecifics. Although the role of Janzen-Connell effects on the maintenance of plant diversity was frequently studied, only few studies targeted Janzen-Connell effects via postdispersal seed predation in temperate grassland systems. We examined effects of conspecific d...

PREMISE OF THE STUDY Biotic resistance is often studied in the context of how interactions between native biota and invading species influence the success of those invaders. Seldom, however, is the strength of "resistance" compared biogeographically, where the ability of a species to impede invader establishment is contrasted between an invader's native and introduced recipient community. MET...

Biological control of exotic invasive plants using exotic insects is practiced under the assumption that biological control agents are safe if they do not directly attack non-target species. We tested this assumption by evaluating the potential for two host-specific biological control agents (Urophora spp.), widely established in North America for spotted knapweed (Centaurea maculosa) control, ...

The influence of temperature, shoot age, and medium on gall induction by Subanguina picridis on Russian knapweed (Acroptilon repens) was examined in vitro. The optimal temperature for gall formation was 20 C. Gall induction was delayed as the temperature decreased, and decreased as shoot age increased. Bud primordia (0-day-old shoots and 5-day-old shoots) with an average length of 4.2 mm and 7....

Klasea is a taxonomically complex genus in which there are many problems, mostly with Klasea kotschyi and Klasea hakkiarica. It is challenging to differentiate the genera based on morphological characters alone. Revision studies performed on the basis of molecular data obtained from studies conducted in recent years have made the phylogenetic relationships and systematic positions of the taxa m...

At local scales, it has often been found that invasibility decreases with increasing resident plant diversity. However, whether resident community diversity similarly resists invasion by alien versus native species is seldom studied. We examined this issue by invading constructed native plant assemblages that varied in species and functional richness with invasive alien or native Asteraceae spe...