High-performing plastic clones best explain the spread of yellow monkeyflower from lowland to higher elevation areas in New Zealand

Abstract

The relative contribution of adaptation and phenotypic plasticity can vary between core and edge populations, with implications for invasive success. We investigated the spread of the invasive yellow monkeyflower, Erythranthe gutatta in New Zealand, where it is spreading from lowland agricultural land into high‐elevation conservation areas. We investigated the extent of phenotypic variation among clones from across the South Island, looked for adaptation and compared degrees of plasticity among lowland core versus montane range‐edge populations. We grew 34 clones and measured their vegetative and floral traits in two common gardens, one in the core range at 9 m a.s.l. and one near the range‐edge at 560 m a.s.l. Observed trait variation was explained by a combination of genotypic diversity (as identified through common gardens) and high phenotypic plasticity. We found a subtle signature of local adaptation to lowland habitats but all clones were plastic and able to survive and reproduce in both gardens. In the range‐edge garden, above‐ground biomass was on average almost double and stolon length almost half that of the same clone in the core garden. Clones from low‐elevation sites showed higher plasticity on average than those from higher elevation sites. The highest performing clones in the core garden were also top performers in the range‐edge garden. These results suggest some highly fit general‐purpose genotypes, possibly pre‐adapted to New Zealand montane conditions, best explains the spread of E. gutatta from lowland to higher elevation areas.

Adaptive Differentiation in the General-Purpose Genotype Invasive PlantErythranthe guttata

“…guttata overall (Twyford et al, 2020, Williamson et al, 2023 or differentiation being still emerging (Prentis et al, 2008). Our findings demonstrate that known selective responses to altitude in E. guttata's native range are being replicated during the Canterbury invasion (Angert, 2006;Hall et al, 2010;Friedman et al, 2015;DeMarche et al, 2016;Kooyers et al, 2019).…”

“…At the University of Canterbury, we made four 10-40mm long cuttings from each plant from a mix of internodes and young shoot tips. Short cutting size minimises maternal effects (Williamson et al ., 2023). We placed the four cuttings from each plant together in small pots filled with fertilised potting soil and placed them under a mister where they were kept constantly warm and wet.…”

“…Data collection occurred from the end of October 2022 to April 2023. We measured 13 vegetative and reproductive traits already known to show adaptive and plastic variance in E. guttata (Galloway, 1995; DeMarche et al ., 2016; Simón-Porcar et al ., 2021; Villellas et al ., 2021; Williamson et al ., 2023). For vegetative traits, above-ground biomass was measured as dry weight.…”

“…E. guttata is an evolutionary model species (Braindvain et al ., 2014) from North America. As an invasive species it has a general-purpose genotype, with high levels of plasticity and little evidence of adaptive patterns (Holeski, 2007; Querns et al ., 2022; Williamson et al ., 2023). However, in its native range E. guttata shows large amounts of local adaptation (Friedman et al ., 2015; Kooyers et al ., 2019), especially based on altitude (DeMarche et al ., 2016; Popovic & Lowry, 2020).…”

“…Erythranthe guttata has been naturalised in New Zealand since 1878 (Vallejo-Marín et al ., 2021). The Canterbury region consists of lowland plains where E. guttata is very well established (below 100 metres above sea level), and a mountainous core where it is actively expanding its range and increasing in abundance (above 450 masl) (Williamson et al ., 2023). The total altitudinal gradient extends from 0-900 masl over distances of ∼120km.…”