Cuscuta (dodder) includes obligate stem parasitic plants distributed globally in a wide array of ecosystems. Some species are agricultural pests that cause significant yield losses while others are endangered and at risk of extinction. While historically Cuscuta species were initially regarded as host-specific, subsequently the paradigm shifted towards considering them as generalists. Recent studies challenged the latter view and suggested that different Cuscuta species exhibit a diversity of host rages that may vary from specialists to generalists, but even in the latter case, different dodders exhibit a preference toward certain hosts. The objective of this study is to determine and analyse the host range diversity within C. gronovii species complex, which includes several closely related widespread species native to North America. This research parallels and complements another study that aims to solve the systematics of the group. Two approaches will be undertaken. First, herbarium species of all the taxa involved will be surveyed and their host data extracted. Based on the raw data, a host frequency index will be calculated for the family, genus and species of the hosts, and bipartite host-parasite networks will be generated. Networks will reveal both the range (or degree) of generalist/specialist strategies as well as possible host overlaps among the Cuscuta taxa. We hypothesize that closer related taxa share more of their hosts ranges. Second, a field study will be conducted for C. gronovii var. gronovii in two population from Ontario to determine the development of the host range during the lifecycle of the parasite. We hypothesize that a succession of primary and secondary hosts occurs during the lifecycle of the parasite. The results of the study will help to better understand the host-parasite relationships within the genus and its possible relationships with the invasiveness/weediness or rarity of different Cuscuta taxa.

 

Jazmen Tourangeau

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