A freshwater invasive in a salty pond: Investigating the germination of invasive Yellow flag iris (Iris pseudacorus) in saline conditions and risk of invasion in coastal marine habitats
| dc.contributor.author | Thomson, Hanna M. | |
| dc.contributor.supervisor | Shackelford, Nancy | |
| dc.contributor.supervisor | Gerwing, Travis G. | |
| dc.date.accessioned | 2023-12-20T22:54:16Z | |
| dc.date.copyright | 2023 | en_US |
| dc.date.issued | 2023-12-20 | |
| dc.degree.department | School of Environmental Studies | en_US |
| dc.degree.level | Master of Science M.Sc. | en_US |
| dc.description.abstract | Numerous generalities have been derived to explain how and why species become invasive. However, species may demonstrate niche shifts, differing phenotypic plasticity, or seemingly able to persist in novel conditions or interactions in disparate portions of their invaded range. As such, regionally tailored, species-specific understanding of invasive species ecology may be fundamental to deriving effective and efficient early detection monitoring and rapid-response control efforts. Yellow flag iris (Iris pseudacorus L.) is a typically freshwater invasive aquatic plant that is sufficiently tolerant of saltwater to disperse through, establish in, and reach sexual and asexual maturity in coastal habitats characterized by full marine salinity (~33 practical salinity units [PSU]). Emerging research suggests that I. pseudacorus may display diverse responses to saline environments in different portions of its invaded range. As such, this thesis aims to clarify the germination response of I. pseudacorus seeds exposed to seawater and identify the risk of coastal invasion in southern British Columbia (BC, Canada) to inform where efficient early detection and rapid response management actions are best maximized. The germination response of I. pseudacorus seeds exposed to saline conditions was evaluated. Seeds were collected from freshwater and coastal marine populations (two experimental source populations) and were immersed in fresh (0 PSU), brackish (13-15 PSU), or marine salinity (33-35 PSU) for 15, 30, 60, or 90 days before recovering in freshwater or remaining in saline conditions for the germination phase. The viability of ungerminated seeds and population-level seed traits (dried weight and testa thickness) were assessed. Gemination was fully inhibited by immersion in salinity unless seeds recovered in freshwater. The freshwater population of seeds consistently achieved higher germination than the coastal population, regardless of immersion salinity or duration. Remarkably high tissue viability among ungerminated seeds and population differences in mean seed coat thickness suggest that population germination differences may arise from dormancy mechanisms rather than seed fitness. A Maxent species distribution model (SDM) was developed to explore the drivers of I. pseudacorus’s coastal habitat suitability and identify regions most at risk of invasion in southern BC to catalyze early detection monitoring and rapid response management efforts. Precipitation during the driest season (40.6% contribution to model prediction) and proximity to urban landscapes (24.9% contribution) were the strongest determinants of coastal habitat suitability. Habitats near perennial freshwater sources were found suitable, though proximity to these features was not essential (distance to freshwater 7% contribution). More generally, south-facing slopes (aspect 6.2% contribution) at or above the mean high tide extent (elevation 7.9% contribution) will likely facilitate the establishment of I. pseudacorus. Regional invasion hotspots are expected near Tofino and Ucluelet on Vancouver Island’s west coast, the southern Gulf Islands and southern Vancouver Island, and in the backshore of the Fraser River delta. My research identifies the germination response of saline-exposed I. pseudacorus and key drivers and locations of coastal habitat suitability in southern British Columbia. These insights can inform the efficient execution of early detection and rapid response coastal monitoring and management strategies targeted at the emerging threat of coastal invasion by I. pseudacorus. While the invasion risk for the southern BC coast was derived, I. pseudacorus has a near-global invaded distribution. As such, understandings gleaned here can more broadly inform invasion dynamics of aquatic invasive plants and the invasive potential of other species with similar life history traits. | en_US |
| dc.description.scholarlevel | Graduate | en_US |
| dc.identifier.uri | http://hdl.handle.net/1828/15742 | |
| dc.language | English | eng |
| dc.language.iso | en | en_US |
| dc.rights | Available to the World Wide Web | en_US |
| dc.subject | Iris pseudacorus | en_US |
| dc.subject | Yellow flag iris | en_US |
| dc.subject | macrophyte | en_US |
| dc.subject | invasive | en_US |
| dc.subject | aquatic | en_US |
| dc.subject | freshwater | en_US |
| dc.subject | coastal | en_US |
| dc.subject | marine | en_US |
| dc.subject | germination | en_US |
| dc.subject | seed | en_US |
| dc.subject | species distribution model | en_US |
| dc.subject | Maxent | en_US |
| dc.subject | early detection | en_US |
| dc.subject | management | en_US |
| dc.subject | British Columbia | en_US |
| dc.title | A freshwater invasive in a salty pond: Investigating the germination of invasive Yellow flag iris (Iris pseudacorus) in saline conditions and risk of invasion in coastal marine habitats | en_US |
| dc.type | Thesis | en_US |