Nectar secretion and bee guild characterıstıcs of yellow star-thistle on Santa Cruz island and lesvos: where have the honey bees gone

Abstract

We compared nectar secretion rates and bee guilds of yellow star-thistle, Centaurea solstitialis, on Santa Cruz Island (USA) and the Northeast Aegean Island of Lesvos (Greece). This plant species is non-native and highly invasive in the western USA but native to Eurasia (including Lesvos). “Nectar flow” was assessed by measuring nectar volumes in florets of flower heads covered with mesh bags (preventing visitation by bees); “nectar standing crop” data were taken from open (unbagged) flower heads to which all bees could gain access. We censused bees at C. solstitialis during comparable periods on both islands and determined the bee guild composition of the plant on Lesvos. Significant differences in nectar levels occurred between bagged and unbagged florets at each locale, especially during the period that pollinators were most common. Nectar flow and nectar standing crop volumes were lower on Lesvos than on Santa Cruz Island. The bee guild diversity at Lesvos was higher relative to Santa Cruz Island. Surprisingly, however, honey bees were not recorded during our monitoring periods on Lesvos.Bu çalışmanın amacı Centaurea solstitialis (Güneşçiçeği) bitkisinin Santa Cruz adası (ABD) ve Ege Denizin’de bulunan Midilli adasında (Yunanistan) balözü akımı ve bu bitkiyi ziyaret eden arıların sayı ve çeşitliliğinin karşılaştırılmasıdır. Güneşçiçeği bitkisinin anavatanı Avrasya olup kendine döllenemeyen bir bitkidir. Yani döllenme ve tohumun oluşması için başka bir bitkiden çiçek özü veya polenin gelmesi gerekmektedir. Bu yüzden bu tip bitkiler gelecek nesillerinin devamı sağlayacak tohum oluşturulması için tozlayıcıları özellikle arıları cezbetmek için balözü, çiçek özü ve yağ gibi maddeler salgılar.