Physical Sciences and Mathematics Commons^™

Influence Of Biocontrol Insects On Canada Thistle: Seed Production, Germinability, And Viability, Gary E. Larson, Tim A. Wittig, Kenneth F. Higgins, Brent Turnipseed, Dawn M. Gardner

The Prairie Naturalist

We conducted surveys of thistle-feeding insects on Canada thistle [Cirsium arvense (L.) Scop.] during the 2000 and 2001 growing seasons at Lacreek National Wildlife Refuge (LNWR), South Dakota, and analyzed their impact on thistle seed production, germination, and viability. Insects included Canada thistle stem weevil [Hadroplontus litura, formerly Ceurtorhynchus lilura, (Coleoptera: Curculionidae)], introduced at LNWR as a biocontrol agent, plus two seed head parasites, the thistle head weevil [Rhinocyllus conicus (Coleoptera: Curculionidae)] and the seed head fly [Terellia ruficauda (Diptera: Tephritidae)]. Infestation by these insects caused no significant reduction in per-head seed yield, with means ranging from 82.5 seeds per …

Reproductive Ecology Of Two Common Woody Species, Juniperus Sabina And Artemisia Santolinifolia, In Mountain Steppes Of Southern Mongolia, Katrin Ronnenberg

Erforschung biologischer Ressourcen der Mongolei / Exploration into the Biological Resources of Mongolia, ISSN 0440-1298

The present study describes the reproductive ecology of the prostrate shrub Juniperus sabina and the dwarf shrub Artemisia santolinifolia in dry mountain steppes of southern Mongolia. Whereas stands of the juniper are located at the drought limit of the genus’ distributional range, the genus Artemisia is typical of central Asian drylands. Both species produce large numbers of reproductive organs. For Juniperus sabina, however, only 2.5% of the morphologically intact seeds were found to be viable. Correspondingly, neither seedlings nor saplings were found in the field, and recruitment by reseeding happens at most rarely under the present climatic conditions.

Instead, …