2018 ASHS Annual Conference

Introduction to the workshop (Lyn Gettys – workshop coordinator and moderator, 5 minutes)

If waterlettuce is native, why is it taking over? (Lyn Gettys, 15 minutes): Arguments for why we consider Pistia stratiotes to be an exotic species despite its presence in fossil records will be the focus of this lead presentation. This talk will uncover some of the buried history of this invasive species, how it came to be such a problem despite its native status, and why things changed. The speaker will discuss the implications of how such burial of a native’s background can create false impressions in the face of the desperate need for control.

Other bad-acting native species (Mike Schnelle, 15 minutes): Natives can evolve and be just as problematic as exotic (non-native) species. They often go unnoticed due to their strategic advantage of being recognizable natives even if they have deleterious effects on humans, landscapes, and local flora and fauna. Natives with subtle but invasive tendencies can affect ecosystem services and sweep through landscapes, often as ornamentals with allied species of economic importance. This talk will focus on but not be limited to the following species capable of escaping cultivation: Black cherry (Prunus serotina), Yaupon holly (Ilex vomitoria), Inland seaoats (Chasmanthium latifolium), and Woodbine (Clematis virginiana). This presentation will examine some of the factors leading these indigenous species to invade landscapes and natural areas, and the issues horticulturists and land managers face in light of their presence.

Challenges of establishing native vs. exotic status of herbarium specimens (Andrzej K. Noyszewski, 15 minutes): In cases where invasive species are presumed to be strictly exotic, the discovery that the species is also native can be disconcerting for researchers and land managers responsible for eradicating an exotic invasive. Such is the case with reed canarygrass, Phalaris arundinacea, where decades of misinformation had led to the call for nationwide control of this species in the US. However, native populations were first reported by LaVoie and then later confirmed by Casler with molecular analyses. This, coupled with the discovery by Anderson that this species has been used in weavings by Native Americans for centuries, also made the native forms of interest for protection. Questions of importance that should be answered when identifying native while controlling exotic/invasive genotypes are the subject of this talk. Identifying the native status of historic, herbarium specimens via molecular analyses is of great interest to determine localities of native populations for confirmation with extant specimens. Historic specimens are often degraded which makes DNA extraction challenging.

Throwing out the bathwater but keeping the baby (Neil O. Anderson, 15 minutes): How and why invasive species evolve has long been prejudiced by their labeling and presumed invasive abilities (native=noninvasive; exotic=invasive). Historic ignorance of species’ native range, expansion due to unintentional involvement by vectors, and their quiet evolution has caused several invasive species to become “poster children”, such as purple loosestrife (Lythrum salicaria), reed canarygrass (Phalaris arundinacea), and others. Common misconceptions on how these became problematic have involved a variety of causes, including sympatry and cross-compatibility creating introgressive hybrids, lack of phytophagous insects for control, wind pollination and intercontinental distribution for their native range. Current research is focusing on how misappropriating the historical contexts can reverse our misconceptions of native species being non-invasive and how this affects control by land managers. Lythrum and Phalaris will be used as example species to demonstrate challenges that native vs. exotic, intra- and inter-specific differences confer to land managers. Issues such as a lack of phenotypic differences challenge land managers’ charge to control invasive genotypes yet retain noninvasive; this is fraught with challenges when native vs. exotic status is invoked or cultural values are entwined. To avoid a monumental impasse, particularly when native and exotic types are phenotypically indistinguishable, this dilemma could be solved via modern techniques using molecular biology.

Open discussion and roundtable (25 minutes): This is an opportunity to talk about problems, challenges and solutions related to nuisance natives. All workshop speakers will be available and audience participation is encouraged.