Hybrid watermilfoil (Myriophyllum spicatum × Myriophyllum sibiricum) exhibits traits associated with greater invasiveness than its introduced and native parental taxa

Abstract

Hybridization has been associated with increased invasiveness in plants. In North America, the hybrid aquatic plant Myriophyllum spicatum × Myriophyllum sibiricum (hybrid watermilfoil, hereafter HWM) is a cross between non-native invasive Eurasian watermilfoil (M. spicatum, EWM) and native northern watermilfoil (M. sibiricum, NWM). Lab-based trials have demonstrated higher growth rates in HWM compared to EWM and NWM, but these patterns have not been systematically examined in the field. In this study, we compared the invasiveness of HWM to its parental taxa, EWM and NWM, by examining the amount and timing of: (1) flowering, (2) surface cover, and (3) biomass (using stem counts as a proxy). We conducted repeat surveys of Myriophyllum beds at eight lakes (2–3 lakes/taxon) in the Minneapolis–St. Paul Metropolitan area (Minnesota, USA) between June 2017 and November 2018. HWM produced more flower spikes earlier and overall, and maintained consistently more flower spikes throughout the growing season than EWM and NWM. In addition, surface cover reached greater annual peaks and was higher for longer throughout the growing season for HWM than for both parental taxa. We did not observe a significant difference in stem counts among the three taxa, but HWM did reach a higher maximum number of stems than either parental taxon. This study provides field-based evidence of increased invasiveness associated with hybridization between EWM and NWM; specifically, greater reproductive potential via flowering and greater surface cover may increase HWM spread, have greater impacts on native species, and pose more of a nuisance to lake users.

Temporal changes in genetic diversity reveal small-scale invasion dynamics of the eastern redcedar (Juniperus virginiana var. virginiana) in the Lakeside Daisy State Nature Preserve in Ohio

“…In contrast, native species that become invasive do not always experience loss of genetic diversity due to environmental filtering (Negi et al 2021). Native invasive species, like ERC, have more sources of genetic diversity close to their invasive range than most nonnative invasive species and are therefore more likely to experience intraspecific hybridization with other ecotypes, which allows the species to cope with stresses resulting from invading new habitat (Castillo et al 2021; Glisson and Larkin 2021; Negi et al 2021).…”

Changing phenology of benthic primary producers in inland waters: Current knowledge and future directions

“…For example, shading by the free-floating duckweed in a mesocosm experiment modified submerged charophyte morphology and Conversely, increased light availability through changes in riparian vegetation canopy associated with stochastic weather events explained an increase in gross primary production by macroalgae in streams altering the overall growing season (Roberts et al 2007;Mulholland et al 2009). Other plant influences on BPP phenology included changes in community structure through the arrival of invasive plants (Toth et al 2019;Torso et al 2020;Glisson et al 2022), adaptation through hybridization (Glisson and Larkin 2021), and sexspecific seasonal variation (Hoffmann et al 2014). In terms of interactions with fauna, event timing was altered by changes in herbivory (Franceschini et al 2010;Pinero-Rodriguez et al 2021) including gut passage of seeds favoring earlier germination (Figuerola et al 2005).…”

2,4‐D and 2,4‐D butoxyethyl ester behavior in Eurasian and hybrid watermilfoil (Myriophyllum spp.)

“…8 This species and its hybrids are especially problematic across the upper midwest states of Wisconsin, Michigan, and Minnesota. In lakes where EWM and the native northern watermilfoil (M. sibiricum Komarov) co-occur, they can hybridize and these hybrids (M. spicatum × M. sibiricum; HWM) grow more aggressively than either parent, [9][10][11] requiring intensive management. 12 One of the main herbicides used to manage EWM and HWM is the synthetic auxin, 2,4-dichlorophenoxy acetic acid (2,4-D).…”