Native and Invading Yellow Starthistle (Centaurea solstitialis) Microbiomes Differ in Composition and Diversity of Bacteria.

Invasive species could benefit from being introduced to locations with more favorable species interactions, including the loss of enemies, the gain of mutualists, or the simplification of complex interaction networks. Microbiomes are an important source of species interactions with strong fitness effects on multicellular organisms, and these interactions are known to vary across regions. The highly invasive plant yellow starthistle () has been shown to experience more favorable microbial interactions in its invasions of the Americas, but the microbiome that must contribute to this variation in interactions is unknown.

Development of 15 microsatellite loci in the endangered subsp. (Brassicaceae).

Premise Of The Study: The endangered subsp. (Brassicaceae) is endemic to a single peninsula in California and threatened by fragmentation. We developed microsatellite markers to investigate genetic diversity in the two extant populations and the degree to which they have diverged from one another.

Population genomic analyses reveal a history of range expansion and trait evolution across the native and invaded range of yellow starthistle (Centaurea solstitialis).

Identifying sources of genetic variation and reconstructing invasion routes for non-native introduced species is central to understanding the circumstances under which they may evolve increased invasiveness. In this study, we used genome-wide single nucleotide polymorphisms to study the colonization history of Centaurea solstitialis in its native range in Eurasia and invasions into the Americas. We leveraged this information to pinpoint key evolutionary shifts in plant size, a focal trait associated with invasiveness in this species.

Evolution of invasiveness through increased resource use in a vacant niche.

Non-native plants are now a pervasive feature of ecosystems across the globe. One hypothesis for this pattern is that introduced species occupy open niches in recipient communities. If true, then non-native plants should often benefit from low competition for limiting resources that define niches.

Biocontrol attack increases pollen limitation under some circumstances in the invasive plant Centaurea solstitialis.

Herbivore damage often deters pollinator visitation and many invasive plants in North America are pollinator-dependent. This has important implications for the biological control of invasive plants because it means that agents that deter pollinators may have a larger than expected impact on the plant. Yet interactions between pollinators and biocontrol agents are rarely evaluated.

Complex interactions among biocontrol agents, pollinators, and an invasive weed: a structural equation modeling approach.

Herbivores, seed predators, and pollinators can exert strong impacts on their host plants. They can also affect the strength of each other's impact by modifying traits in their shared host, producing super- or sub-additive outcomes. This phenomenon is especially relevant to biological control of invasive plants because most invaders are attacked by multiple agents.

Variable effects of a generalist parasitoid on a biocontrol seed predator and its target weed.

Biological control (the importation of enemies from an invader's native range) is often considered our best chance of controlling the most widespread invaders. Ideally, the agent reduces invader abundance to some acceptably low level, and the two coexist at low density with the agent providing continuous control over the long-term. But the outcome may be complicated when the agent is attacked by native predators and parasites.

Trait-mediated interactions and lifetime fitness of the invasive plant Centaurea solstitialis.

Plants interact with numerous enemies and mutualists simultaneously and sequentially. Such multispecies interactions can give rise to trait-mediated indirect effects that are likely to be common in nature but which are also inherently difficult to predict. Understanding multispecies interactions is also important in the use of biological control agents to control invasive plants because modern approaches to biocontrol rely on releasing multiple agents for each target weed.

Widespread seed limitation affects plant density but not population trajectory in the invasive plant Centaurea solstitialis.

In some plant populations, the availability of seeds strongly regulates recruitment. However, a scarcity of germination microsites, granivory or density-dependent mortality can reduce the number of plants that germinate or survive to flower. The relative strengths of these controls are unknown for most plant populations and for exotic invaders in particular.