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

Swope, Sarah M.; Parker, Ingrid M.

doi:10.1007/s00442-010-1641-1

Cited by 23 publications

(34 citation statements)

References 39 publications

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“…By the mid 20th century, the species was rapidly expanding through California's Central Valley and Sierra Nevada foothill grasslands, and the current leading edge of this invasion lies above 4,000 m in elevation along the west side of the Sierra Nevada Mountains (Pitcairn, Schoenig, Yacoub, & Gendron, ). In the North American invasion, habitat quality is often linked to the climatic environment, with warmer and drier habitats frequently supporting the densest C. solstitialis populations (Pitcairn et al, ; Swope & Parker, ). During expansion, C. solstitialis has crossed climatic gradients that are largely independent in direction from the pathway of colonization (Figure ), allowing us to quantify the influence of both climatic environment and expansion history (time since founding) on estimates of N e across populations.…”

Section: Introductionmentioning

confidence: 99%

Expansion history and environmental suitability shape effective population size in a plant invasion

2019

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The margins of an expanding range are predicted to be challenging environments for adaptation. Marginal populations should often experience low effective population sizes (Ne) where genetic drift is high due to demographic expansion and/or census population size is low due to unfavourable environmental conditions. Nevertheless, invasive species demonstrate increasing evidence of rapid evolution and potential adaptation to novel environments encountered during colonization, calling into question whether significant reductions in Ne are realized during range expansions in nature. Here we report one of the first empirical tests of the joint effects of expansion dynamics and environment on effective population size variation during invasive range expansion. We estimate contemporary values of Ne using rates of linkage disequilibrium among genome‐wide markers within introduced populations of the highly invasive plant Centaurea solstitialis (yellow starthistle) in North America (California, USA), and within native Eurasian populations. As predicted, we find that Ne within the invaded range is positively correlated with both expansion history (time since founding) and habitat quality (abiotic climate). History and climate had independent additive effects with similar effect sizes, indicating an important role for both factors in this invasion. These results support theoretical expectations for the population genetics of range expansion, though whether these processes can ultimately arrest the spread of an invasive species remains an unanswered question.

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Section: Introductionmentioning

confidence: 99%

Expansion history and environmental suitability shape effective population size in a plant invasion

2019

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“…Seed limitation influences recruitment of many native (Turnbull et al 2000, Clark et al 2007) and non-native species (Jongejans et al 2007, Swope and Parker 2010, Connolly et al 2014. Seed limitation can be the product of 1) a paucity of reproducing plants, 2) poor seed dispersal, 3) biotic agents that directly reduce seed number, 4) poor propagule viability, or 5) some combination thereof (Harper 1977, Seabloom et al 2003, Davis 2009).…”

Section: Seed Limitation Disturbance and Naturalizationsmentioning

confidence: 99%

Biotic constraints on the establishment and performance of native, naturalized, and invasive plants in Pacific Northwest (USA) steppe and forest

Connolly¹,

Powers²

2017

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Factors that cause differential establishment among naturalized, invasive, and native species are inadequately documented, much less often quantified among different communities. We evaluated the effects of seed addition and disturbance (i.e., understory canopy removal) on the establishment and seedling biomass among two naturalized, two invasive, and two native species (1 forb, 1 grass in each group) within steppe and low elevation forest communities in eastern Washington, USA. Establishment within each plant immigrant class was enhanced by seed addition: naturalized species showed the greatest difference in establishment between seed addition and no seed addition plots, native and invasive species establishment also increased following seed addition but not to the same magnitude as naturalized species. Within seed addition plots, understory canopy disturbance resulted in significant increases in plant establishment (regardless of plant immigration class) relative to undisturbed plots and the magnitude of this effect was comparable between steppe and adjacent forest. However, regardless of disturbance treatment fewer invasive plants established in the forest than in the steppe, whereas native and naturalized plant establishment did not differ between the habitats. Individual biomass of naturalized species were consistently greater in disturbed (canopy removed) versus undisturbed control plots and naturalized species were also larger in the steppe than in the forest at the time of harvest. Similar trends in plant size were observed for the native and invasive species, but the differences in biomass for these two immigration classes between disturbance treatments and between habitats were not significant. We found that strong limitations of non-native species is correlated with intact canopy cover within the forest understory, likely driven by the direct or indirect consequences of low light transmittance through the arboreal and understory canopy. Connolly et al. / NeoBiota 34: 21-40 (2017) 22 Considered collectively, our results demonstrate how seed limitation and intact plant ground cover can limit the abundance and performance of naturalized species in Pacific Northwest steppe and low elevation forest, suggesting that local disturbance in both habitats creates microsites for these species to establish and survive. Future studies evaluating interactions between multiple barriers to establishment using more representatives from each immigration class will further reveal how biotic interactions ultimately influence the demography and distribution of non-native plants within these communities.

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“…This is somewhat unfortunate given that in our previous work we detected the strongest seedlimited recruitment and no microsite limitation at this site compared to the others (Swope and Parker 2010b). This is somewhat unfortunate given that in our previous work we detected the strongest seedlimited recruitment and no microsite limitation at this site compared to the others (Swope and Parker 2010b).…”

Section: Impact Vs Effective Controlmentioning

confidence: 56%

“…Elsewhere we have shown that recruitment at the Coast and the Interior will vary between being seed-limited and microsite-limited at spatial scales relevant to dispersal, which for this species is a matter of meters or less (Swope and Parker 2010b). But it can be difficult to predict how effectively agents will control populations of their target weed based on their impacts on individual plants.…”

Section: Impact Vs Effective Controlmentioning

confidence: 99%

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

Swope

Parker

2012

Ecological Applications

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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. Unfortunately, complex interactions among agents are rarely studied. We used structural equation modeling (SEM) to quantify the effect of two biocontrol agents and generalist pollinators on the invasive weed Centaurea solstitialis, and to identify and quantify the direct and indirect interaction pathways among them. The weevil Eustenopus villosus is both a bud herbivore and a predispersal seed predator; the fly Chaetorellia succinea is also a predispersal seed predator; Apis mellifera is the primary pollinator. We conducted this work at three sites spanning the longitudinal range of C. solstitialis in California (USA) from the coast to the Sierra Nevada Mountains. SEM revealed that bud herbivory had the largest total effect on the weed's fecundity. The direct effect of bud herbivory on final seed set was 2-4 times larger in magnitude than the direct effect of seed predation by both agents combined. SEM also revealed important indirect interactions; by reducing the number of inflorescences plants produced, bud herbivory indirectly reduced the plant's attractiveness to ovipositing seed predators. This indirect, positive pathway reduced bud herbivory's direct negative effect by 11-25%. In the same way, bud herbivory also reduced pollinator visitation, although the magnitude of this pathway was relatively small. E. villosus oviposition deterred C. succinea oviposition, which is unfortunate because C. succinea is the more voracious of the seed predators. Finally, C. succinea oviposition indirectly deterred pollinator visitation, thereby enhancing its net effect on the plant. This study demonstrates the powerful insights that can be gained from the SEM approach in understanding the multiple direct and indirect interactions among agents and pollinators and their effects on an invasive weed. Such an approach may improve our ability to manage weeds with biocontrol agents by identifying pathways that could be exploited by future agents and minimizing the possibility of interference with established agents.

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

Cited by 23 publications

References 39 publications

Expansion history and environmental suitability shape effective population size in a plant invasion

Expansion history and environmental suitability shape effective population size in a plant invasion

Biotic constraints on the establishment and performance of native, naturalized, and invasive plants in Pacific Northwest (USA) steppe and forest

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

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