Investigation of threatened arable weeds and their conservation status in Turkey C TU ¨ RE & H BO ¨ CU ¨ K Faculty of Science, Department of Biology, Anadolu University, Eskis ¸ ehir, Turkey Received 8 November 2007 Revised version accepted 9 January 2008 Summary Agronomic operations carried out in arable lands may cause changes in weed populations and also decrease the number of animal species that depend on these weed species. An emerging paradigm is the conservation and sustainability of weed species. In this study, risk status of arable weeds in Turkey was evaluated and it was determined that 112 of them (76 endemic and 36 non- endemic species) were at risk according to the IUCN Red List. Turkey is extremely diverse, with over 3000 endemic plant species out of nearly 12 000 recorded. Considering endemic weeds, they are classified in the following risk categories: critically endangered (four weed species), endangered (EN) (six), vulnerable (VU) (14), near threatened (seven), least concern (41) and data deficient (DD) (four species). Among the non-endemic weeds, three species are EN, 31 VU and two are DD. The families with the highest threatened weed species are Scrophulariaceae, Fabaceae, Asteraceae, Brassicaceae and Lamiaceae. The identification of weed species in arable habitats and their risk status is a useful tool for assessing and monitoring how the sustainability of weed populations is affected by farming practices. The results show the necessity of adopting new environment- friendly agricultural methods to conserve the high number of endemic weed species under threat in Turkey. Keywords: weed species, conservation, agroecosystem, biodiversity, rare species, risk category. TU ¨ RE C&BO ¨ CU ¨ K H (2008). Investigation of threatened arable weeds and their conservation status in Turkey. Weed Research 48, 289–296. Introduction Weed species are important components of both natural and arable lands. Although they cause some negative effects with reference to productivity, weeds in crop fields could be repositories of native species for the restoration of native habitats (Tu¨re & Bo¨cu¨k, 2000; Scheepens et al., 2001). Arable habitats are conceived to be not only food and feed supplying areas, but also for supporting biological diversity (Freemark et al., 2002). Therefore, basic research on weed species of arable systems is crucial to understand their relationships with biodiversity, ecosystem functioning, conservation and sustainability. Because ecological studies are mostly carried out in natural areas outside arable habitats, it has taken time to realise the role of weeds for biodiver- sity. In Europe, there has been a dramatic loss of native species growing in arable fields for the past 60 years, because of increasing agricultural activities (Kleijn & Van Der Voort, 1997). At present, this situation has been recognised by many countries like the UK, the Netherlands, Germany and Denmark. Efforts to deter- mine how the weed populations are affected by the applications in arable lands and why they are becoming extinct are being made (Gerowitt et al., 2003; Marshall et al., 2003). Data obtained from these kinds of studies provide awareness of the importance of threatened weeds in Turkey in respect to biodiversity and conser- vation. However, weeds are major constraints on crop yields and the provision of food. As such, it is a necessity to control their spread or to eliminate them from arable fields (Tanveer et al., 2003). In Turkey and across the world, weeds have been eliminated by modern practices, such as herbicide usage, application of mineral fertilis- ers, deep ploughing as well as mechanical removal Correspondence: C Tu¨re, Faculty of Science, Department of Biology, Anadolu University, Eskis¸ ehir 26470, Turkey. Tel: (+90) 222 335 05 80 5700; Fax: (+90) 222 320 49 10; E-mail: cture@anadolu.edu.tr Ó 2008 The Authors Journal Compilation Ó 2008 European Weed Research Society Weed Research 48, 289–296