Genotypic diversity, reproductive strategies, and natural selection in non-native populations of Mimulus guttatus

The success of non-native species exposed to environmental conditions may depend on how the species adapt to new conditions. For this reason, non-native species offer the opportunity to understand evolutionary mechanisms such as natural selection that can promote adaptive evolution in new conditions, and also to investigate whether intraspecific admixture may serve as a stimulus for invasion by increasing fitness or a cost to fitness due to outbreeding depression. In addition, high performance of introduced species may be accomplished by a combination of multiple reproductive strategies (e.g., vegetative and sexual reproduction) that can contribute to dispersal and colonization ability. In this research, the herbaceous Mimulus guttatus native to North America and naturalized in United Kingdom (UK) is used to investigate: (1) the level of genotypic (clonal) diversity and genetic variation in non-native populations; (2) the effect of resource availability on the relative investment of sexual and clonal reproduction; (3) the level of phenotypic variation among non-native populations; and (4) patterns of natural selection in its introduced range, and evidence of outbreeding depression in admixed experimental populations. The genotyping study using single nucleotide polymorphisms reveals that non-native populations show a wide variation of genotypic diversity and that the largest percentage of genetic variation is within populations either in native or introduced ranges. A common garden glasshouse experiment with non-native populations indicates that limited space intensifies the trade-off between sexual and clonal lateral spread, and suggests that populations under limited space conditions (e.g., high-density population) may have to invest less in sexual reproduction than in clonal lateral expansion. A survey of natural M. guttatus populations in UK indicates that production of flowers is favoured in places with low precipitation and high temperatures where production of stolons is limited in M. guttatus. The field experiment with F2 individuals from three crosses between introduced and native populations shows that admixed individuals from introduced populations have higher population growth rate due to increased survival, clonality, and seed production than admixed individuals from introduced and native populations, consistent with outbreeding depression. Selection through sexual fitness favours large floral displays, large vegetative traits, clonal spread, and early flowering in the non-native range. The results presented in this thesis indicate that clonal and sexual reproduction are integrated strategies that contribute to population growth rate, and the alternative investment in both traits in different environments may contribute to the colonization of the species in different habitats. Natural selection has an important role in the naturalization of a highly diverse species such as M. guttatus, and intraspecific admixture is not always beneficial in the introduced range as it may result in outbreeding depression, which further suggests the potential of non-native populations to evolve by adaptation

Genetic variation and clonal diversity in introduced populations of Mimulus guttatus assessed by genotyping at 62 single nucleotide polymorphism loci

Background: Single nucleotide polymorphisms (SNPs) are increasingly being used to study non-native populations. SNPs are relatively information poor on a per locus basis, but allow genotyping more loci than others markers (e.g., microsatellites) and have the advantage of consistent allele calls between studies.Aims: We investigated the utility of a newly developed set of SNP markers, suitable for high throughput genotyping to characterise genotypic variation and population structure in non-native populations of the facultative clonal herb Mimulus guttatus in the United Kingdom (UK).Methods: We analysed 62 SNP markers and using a high throughput platform genotyped 383 individuals from 10 populations from the native range in North America and 14 populations in the UK.Results: We found wide variation in genotypic diversity within UK populations, indicating reproductive strategies that vary from mostly clonal to mostly sexual. All but one UK population were, on average, more closely related to each other than to North American populations, and the exceptional UK population showed strong affinity to native Alaskan plants.Conclusions: A small number of SNPs can detect patterns of clonality and broad-scale relationships between native and introduced populations. However, elucidating population structure at a finer scale will require genotyping individuals at greater depth

Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F2 crosses between native and introduced populations of Mimulus guttatus to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F2s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate owing to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture

SNP genotypes for native and introduced populations of Mimulus guttatus

375 SNP genotypes at 62 SNP loci for native (North America) and introduced (United Kingdom) populations

Figure S5 from Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F2 crosses between native and introduced populations of <i>Mimulus guttatus</i> to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F2s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate due to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture

Figure S4 from Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F₂ crosses between native and introduced populations of <i>Mimulus guttatus</i> to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F₂s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate owing to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture

SUPPLEMENTAL METHODS from Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F2 crosses between native and introduced populations of <i>Mimulus guttatus</i> to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F2s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate due to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture

Figure S2 from Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F₂ crosses between native and introduced populations of <i>Mimulus guttatus</i> to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F₂s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate owing to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture

Figure S1 from Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F2 crosses between native and introduced populations of <i>Mimulus guttatus</i> to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F2s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate due to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture

Figure S5 from Natural selection and outbreeding depression suggest adaptive differentiation in the invasive range of a clonal plant

Analyses of phenotypic selection and demography in field populations are powerful ways to establishing the potential role of natural selection in shaping evolution during biological invasions. Here we use experimental F₂ crosses between native and introduced populations of <i>Mimulus guttatus</i> to estimate the pattern of natural selection in part of its introduced range, and to seek evidence of outbreeding depression of colonists. The F₂s combined the genome of an introduced population with the genome of either native or introduced populations. We found that the introduced × introduced cross had the fastest population growth rate owing to increased winter survival, clonality and seed production. Our analysis also revealed that selection through sexual fitness favoured large floral displays, large vegetative and flower size, lateral spread and early flowering. Our results indicate a source-of-origin effect, consistent with outbreeding depression exposed by mating between introduced and native populations. Our findings suggest that well-established non-native populations may pay a high fitness cost during subsequent bouts of admixture with native populations, and reveal that processes such as local adaptation in the invasive range can mediate the fitness consequences of admixture