Rapid local adaptation in both sexual and asexual invasive populations of monkeyflowers (Mimulusspp.)

Abstract

Background and Aims Traditionally, local adaptation has been seen as the outcome of a long evolutionary history, particularly with regard to sexual lineages. By contrast, phenotypic plasticity has been thought to be most important during the initial stages of population establishment and in asexual species. We evaluated the roles of adaptive evolution and phenotypic plasticity in the invasive success of two closely related species of invasive monkeyflowers (Mimulus) in the UK that have contrasting reproductive strategies: M. guttatus combines sexual (seeds) and asexual (clonal growth) reproduction while M. × robertsii is entirely asexual. Methods We compared the clonality (number of stolons), floral and vegetative phenotype, and phenotypic plasticity of native (M. guttatus) and invasive (M. guttatus and M. × robertsii) populations grown in controlled environment chambers under the environmental conditions at each latitudinal extreme of the UK. The goal was to discern the roles of temperature and photoperiod on the expression of phenotypic traits. Next, we tested the existence of local adaptation in the two species within the invasive range with a reciprocal transplant experiment at two field sites in the latitudinal extremes of the UK, and analysed which phenotypic traits underlie potential local fitness advantages in each species. Key Results Populations of M. guttatus in the UK showed local adaptation through sexual function (fruit production), while M. × robertsii showed local adaptation via asexual function (stolon production). Phenotypic selection analyses revealed that different traits are associated with fitness in each species. Invasive and native populations of M. guttatus had similar phenotypic plasticity and clonality. M. × robertsii presents greater plasticity and clonality than native M. guttatus, but most populations have restricted clonality under the warm conditions of the south of the UK. Conclusions This study provides experimental evidence of local adaptation in a strictly asexual invasive species with high clonality and phenotypic plasticity. This indicates that even asexual taxa can rapidly (<200 years) adapt to novel environmental conditions in which alternative strategies may not ensure the persistence of populations.

Autopolyploid establishment depends on life‐history strategy and the mating outcomes of clonal architecture

“…Additionally, there are examples of sterile allopolyploids persisting solely via clonal reproduction for many generations, and even evidence of local adaptation in these lineages (e.g., triploid Mimulus × robertsii ; Simón‐Porcar et al. 2021), potentially due to high heterozygosity in polyploids of hybrid origin.…”

“…Nonetheless, spreading architectures may perform well in environments with high temporal variability or frequent disturbance where slower expansion could result in the stochastic loss of all polyploids ( Čertner et al 2017), especially if genetic uniformity is counteracted by recurrent polyploid formation, immigration, or high rates of vegetative somatic mutation between ramets (Yu et al 2020). Additionally, there are examples of sterile allopolyploids persisting solely via clonal reproduction for many generations, and even evidence of local adaptation in these lineages (e.g., triploid Mimulus × robertsii; Simón-Porcar et al 2021), potentially due to high heterozygosity in polyploids of hybrid origin.…”

Rapid evolution of flower phenology and clonality in restored populations of multiple grassland species

“…Clonal propagation in general is a common adaptation of species that grow in frequently mown or grazed habitats (Wellstein & Kuss, 2011), yet within-species adaptive differentiation in ability of clonal reproduction was so-far only rarely documented (e.g. Simon-Porcar et al, 2021; Wang et al, 2016).…”

The power of observation: Eugen Warming (1918) Om Jordudløbere (‘Underground runners') and the ecology and evolution of clonal plants

“…Such plants, while potentially disadvantageous in the early dispersal phase (due to less reliance on seeds) are more persistent once established (Pyšek 1997). Indeed, some studies have found clonality important for maintaining populations in non‐native ranges, even if they remain completely or dominantly clonal (Geng et al 2016, Simón‐Porcar et al 2021).…”