Observations on nectar availability and bee visitation at patches of yellow star-thistle and chasteberry on the northeast aegean Island of lesvos (Greece)

Abstract

We examined numbers of honey bees (Apis) versus non-Apis bees at patches of yellow star-thistle, Centaurea solstitialis, and chasteberry, Vitex agnus-castus, on the Northeast Aegean Island of Lesvos in Greece. The resulting visitation patterns are associated with average nectar volumes measured from florets of each plant species. Honey bees visit V. agnus-castus more frequently when bees are sampled from adjoining floral displays of both species. In addition, the average size of bee pollinators (as measured by head capsule width) collected during this time was always larger from V. agnus-castus relative to C. solstitialis, and significantly so in the majority of cases. These patterns contrast with findings from previous studies in the western USA (California) where yellow star-thistle is not a native plant species but honey bees commonly visit it. Indeed, in North America, the abundant honey derived from yellow star-thistle is often considered a desirable product for marketing by beekeepers.

İstilacı bitki türleri istila ettikleri çevrelere nektar gibi yeni besin kaynakları getirerek büyük etkiler yapmaktadır. Batı Amerika’da Kaliforniya’daki Santa Cruz adasında örneğin güneş çiçeği Centaurea solstitialis ada ekosisteminde balarılarını daha yüksek sayıda cezbetmekte ve kendisine çekmektedir, sonucunda ise bu türün fazla sayıda tohum üretmesine neden olmaktadır. Bu çalışmada benzer durum iki farklı türde güneş çiçeği ve hayıt bitkisinin ürettiği nektar miktarı ile tozlaştırıcıları kendilerine farklı sayılarda çekip çekmediği konusu araştırılmıştır.