Multiple introductions and gene flow in subtropical South American populations of the fireweed, Senecio madagascariensis(Asteraceae)

Mäder, Geraldo; Castro, Luana; Bonatto, Sandro L.; Freitas, Loreta B.

doi:10.1590/1678-4685-gmb-2015-0167

Cited by 14 publications

(8 citation statements)

References 61 publications

(87 reference statements)

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“…Due to spatial sorting, the invasion front may be inhabited exclusively by the individuals with the highest dispersal rates (even if they are less fit than individuals with low dispersal rates) because they have arrived first and can only breed with each other (Shine et al, 2011), resulting in a geographic separation of phenotypes (Shine et al, 2011; Hudson et al, 2016). 3) Admixture or hybridization may occur between individuals from different introductions or sources (Mader et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Increased Adaptive Variation Despite Reduced Overall Genetic Diversity in a Rapidly Adapting Invader

et al. 2019

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Invasive species often evolve rapidly following introduction despite genetic bottlenecks that may result from small numbers of founders; however, some invasions may not fit this “genetic paradox”. The invasive cane toad (Rhinella marina) displays high phenotypic variation across its introduced Australian range. Here, we used three genome-wide datasets to characterize their population structure and genetic diversity. We found that toads form three genetic clusters: 1) native range toads, 2) toads from the source population in Hawaii and long-established areas near introduction sites in Australia, and 3) toads from more recently established northern Australian sites. Although we find an overall reduction in genetic diversity following introduction, we do not see this reduction in loci putatively under selection, suggesting that genetic diversity may have been maintained at ecologically relevant traits, or that mutation rates were high enough to maintain adaptive potential. Nonetheless, toads encounter novel environmental challenges in Australia, and the transition between genetic clusters occurs at a point along the invasion transect where temperature rises and rainfall decreases. We identify environmentally associated loci known to be involved in resistance to heat and dehydration. This study highlights that natural selection occurs rapidly and plays a vital role in shaping the structure of invasive populations.

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Section: Introductionmentioning

confidence: 99%

Increased Adaptive Variation Despite Reduced Overall Genetic Diversity in a Rapidly Adapting Invader

et al. 2019

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“…(c) Admixture between individuals from different introductions or sources, as well as hybridization, may also drive evolutionary change in some invasive populations (Mader, Castro, Bonatto, & Freitas, 2016). Alternatively, some traits differ simply due to heightened environmental variability experienced by invaders and do not reflect evolutionary change.…”

Section: Introductionmentioning

confidence: 99%

Immune and environment‐driven gene expression during invasion: An eco‐immunological application of RNA‐Seq

Selechnik

Richardson

Shine

et al. 2019

Ecology and Evolution

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Host–pathogen associations change rapidly during a biological invasion and are predicted to impose strong selection on immune function. It has been proposed that the invader may experience an abrupt reduction in pathogen‐mediated selection (“enemy release”), thereby favoring decreased investment into “costly” immune responses. Across plants and animals, there is mixed support for this prediction. Pathogens are not the only form of selection imposed on invaders; differences in abiotic environmental conditions between native and introduced ranges are also expected to drive rapid evolution. Here, we use RNA‐Seq to assess the expression patterns of immune and environmentally associated genes in the cane toad (Rhinella marina) across its invasive Australian range. Transcripts encoding mediators of costly immune responses (inflammation, cytotoxicity) showed a curvilinear relationship with invasion history, with highest expression in toads from oldest and newest colonized areas. This pattern is surprising given theoretical expectations of density dynamics in invasive species and may be because density influences both intraspecific competition and parasite transmission, generating conflicting effects on the strength of immune responses. Alternatively, this expression pattern may be the result of other evolutionary forces, such as spatial sorting and genetic drift, working simultaneously with natural selection. Our findings do not support predictions about immune function based on the enemy release hypothesis and suggest instead that the effects of enemy release are difficult to isolate in wild populations, especially in the absence of information regarding parasite and pathogen infection. Additionally, expression patterns of genes underlying putatively environmentally associated traits are consistent with previous genetic studies, providing further support that Australian cane toads have adapted to novel abiotic challenges.

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“…Those events stimulated the rapid evolution and phenotypic plasticity, facilitating range expansion 30 . Likewise, the multiple introductions of S. madagascariensis in Brazil are a gene source that might ensure a higher variability in dispersal traits of the invasive populations 31 .…”

Section: Discussionmentioning

confidence: 99%

Morphological differentiation across the invasive range in Senecio madagascariensis populations

Dematteis

Ferrucci

Coulleri

2020

Sci Rep

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Invasive species are characterized by their ability to colonize new habitats and establish populations away from their native range. In this sense, these plants are expected to have plastic responses to adapt to the environmental pressures during the invasion process. Hence, the role of natural selection is essential because it might favor the occurrence of advantageous traits. However, gene flow can counteract natural selection because immigrants introduce genes adapted to different conditions, with these introductions tending to homogenize allelic frequencies. In this work, we explore the effect of natural selection in invasive populations of S. madagascariensis in Argentina. We quantified leaf area, head number, and length of internodes and inflorescence from material spanning 54 years (1962–2016) and then compared between the edge versus established ranges. Our results show differences in all the measured plant traits among the sampled areas. However, only leaf area was statistically significant, which evidences different responses under the same environmental pressures in the areas located in the edge and established ranges. On the other hand, unlike homogeneous areas, the areas characterized by phenotypically diverse individuals were related to higher dispersal ability. In this sense, long-distance dispersal between neighboring areas may have had an important role in the recorded values. Furthermore, the implications of natural selection and founder effect in the invasion of S. madagascariensis are discussed.

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Multiple introductions and gene flow in subtropical South American populations of the fireweed, Senecio madagascariensis(Asteraceae)

Cited by 14 publications

References 61 publications

Increased Adaptive Variation Despite Reduced Overall Genetic Diversity in a Rapidly Adapting Invader

Increased Adaptive Variation Despite Reduced Overall Genetic Diversity in a Rapidly Adapting Invader

Immune and environment‐driven gene expression during invasion: An eco‐immunological application of RNA‐Seq

Morphological differentiation across the invasive range in Senecio madagascariensis populations

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