ABSTRACT

Tamarix (Tamaricaceae), a phreatophyte genus from the Old World, is a tenacious competitor which has invaded North America (namely the United States and Mexico), Australia, and South Africa amongst other countries. Biological control of invasive Tamarix taxa in South Africa is complicated by the indigenous T. usneoides, which is phylogenetically distant from the invasive T. chinensis and T. ramosissima. This suggests the possibility of finding a host specific biological control agent. Trabutina mannipara underwent laboratory-based host specificity trials. During no-choice testing, T. mannipara showed no difference in host range selection as there was no significant difference in the settling and developmental rate on all Tamarix taxa tested. These undesirable non-target effects on the indigenous species led us to reject T. mannipara as a potential biological control agent of invasive Tamarix taxa. We examined the possibility of secondary metabolites being a factor in the feeding choice of T. mannipara, but no significant difference in the bark tannin levels was found between the above Tamarix taxa. Further investigation of plant secondary metabolites, used for defense against insect herbivory, may however, assist in the selection of biological control agents against invasive Tamarix in South Africa.

摘要

柽柳(Tamaricaceae) 是来自旧大陆的藻类植物，是一个顽强的竞争者，已入侵北美（即美国和墨西哥）、澳大利亚和南非等国家。南非入侵柽柳分类群的生物控制因本土的T. usneoides而复杂化，其在系统发育上与入侵的T. chinensis和T. ramosissima相距甚远。这表明找到宿主特异性生物控制剂的可能性。Trabutina mannipara进行了基于实验室的宿主特异性试验。在无选择测试期间，T. mannipara显示宿主范围选择没有差异，因为所有测试的柽柳分类群的沉降和发育率没有显着差异。这些对本土物种的不良非目标影响导致我们拒绝将T. mannipara作为入侵性柽柳分类群的潜在生物控制剂。我们研究了次生代谢物成为T. mannipara饲养选择的一个因素的可能性，但在上述柽柳分类群之间没有发现树皮单宁水平的显着差异。然而，进一步研究用于防御昆虫食草的植物次生代谢物可能有助于选择针对入侵性柽柳的生物控制剂在南非。