Accelerated seedling emergence in interspecific competitive neighbourhoods

Dyer, Andrew R.; Fenech, Alan Paul; Rice, Kevin J.

doi:10.1111/j.1461-0248.2000.00187.x

Cited by 75 publications

(111 citation statements)

References 35 publications

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“…In this particular invasive species, the evidence concurs with field studies describing the importance of life-history traits and the seed biology of C. solstitialis in California in that a large proportion of seeds can germinate and frequently do so very quickly [18]. While not measured directly here, it is likely that C. solstitialis can express the phenomenon described as adaptive acceleration in competitive contexts [42]. In this study, increased germination by seeds from California was detected, and acceleration was potentially expressed via an increased relative growth rate similar to field studies [13].…”

Section: Discussionsupporting

confidence: 82%

Cage Matching: Head to Head Competition Experiments of an Invasive Plant Species from Different Regions as a Means to Test for Differentiation

et al. 2009

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Many hypotheses are prevalent in the literature predicting why some plant species can become invasive. However, in some respects, we lack a standard approach to compare the breadth of various studies and differentiate between alternative explanations. Furthermore, most of these hypotheses rely on ‘changes in density’ of an introduced species to infer invasiveness. Here, we propose a simple method to screen invasive plant species for potential differences in density effects between novel regions. Studies of plant competition using density series are a fundamental tool applied to virtually every aspect of plant population ecology to better understand evolution. Hence, we use a simple density series with substitution contrasting the performance of Centaurea solstitialis in monoculture (from one region) to mixtures (seeds from two regions). All else being equal, if there is no difference between the introduced species in the two novel regions compared, Argentina and California, then there should be no competitive differences between intra and inter-regional competition series. Using a replicated regression design, seeds of each species were sown in the greenhouse at 5 densities in monoculture and mixed and grown till onset of flowering. Centaurea seeds from California had higher germination while seedlings had significantly greater survival than Argentina. There was no evidence for density dependence in any measure for the California region but negative density dependence was detected in the germination of seeds from Argentina. The relative differences in competition also differed between regions with no evidence of differential competitive effects of seeds from Argentina in mixture versus monoculture while seeds from California expressed a relative cost in germination and relative growth rate in mixtures with Argentina. In the former instance, lack of difference does not mean ‘no ecological differences’ but does suggest that local adaptation in competitive abilities has not occurred. Importantly, this method successfully detected differences in the response of an invasive species to changes in density between novel regions which suggests that it is a useful preliminary means to explore invasiveness.

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Section: Discussionsupporting

confidence: 82%

Cage Matching: Head to Head Competition Experiments of an Invasive Plant Species from Different Regions as a Means to Test for Differentiation

et al. 2009

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“…Variation in emergence time can potentially amplify the effect of size and reproductive hierarchies and their evolutionary consequences (Fowler 1984;Weiner 1990;Miller et al 1994;Dyer et al 2000). In our study, early germination was observed primarily in riparian sites where competition is presumably more intense.…”

Section: Patterns Of Local Adaptationmentioning

confidence: 64%

Local Adaptation, Patterns of Selection, and Gene Flow in the Californian Serpentine Sunflower (Helianthus Exilis)

Sambatti

Rice²

2006

Evolution

173

154

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The traditional view of the species as the fundamental unit of evolution has been challenged by observations that in heterogeneous environments, gene flow may be too restricted to overcome the effects of local selection. Whether a species evolves as a cohesive unit depends critically on the dynamic balance between homogenizing gene flow among populations and potentially disruptive local adaptation. To examine this evolutionary balance between "global" gene flow and local selection, we studied northern Californian populations of Helianthus exilis, the serpentine sunflower, within a mosaic of contrasting serpentine and nonserpentine areas that differ considerably in soil chemistry and water availability. Local adaptation to riparian and serpentine habitats was studied in Helianthus exilis along with an analysis of gene flow patterns among populations within these habitats. Local adaptation was assessed in H. exilis during 2002 and 2003 using reciprocal transplant experiments at multiple locations within serpentine and riparian habitats. Effects of competition and germination date on the expression of local adaptation were also examined within the reciprocal transplant experiments. Local adaptation was detected in both years at the local site level and at the level of habitat. The analysis of the transplanted populations indicated that the patterns of selection differed considerably between riparian and serpentine sites. Differential survivorship occurred in serpentine habitats, whereas selection on reproductive output predominated in riparian habitats. Local adaptation was expressed only in the absence of competition. Local adaptation in terms of survivorship was most strongly expressed in treatments with delayed seed germination. Microsatellite markers were used to quantify population genetic parameters and examine the patterns of gene flow among sampled populations. Analysis of molecular markers revealed a system of population patches that freely exchange genes with each other. Strong selection seems to maintain ecotypic variation within this endemic sunflower species, while extensive gene flow among populations prevents local speciation between serpentine and riparian ecotypes.

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“…These over-estimates might stem from all the possible risks or factors that may select for greater bet-hedging, e.g. seed predation, interspecific competition, variable temperature, and disease [21][22][23][24][25][26][27], which aren't included in our model. Furthermore, 30 years of precipitation may not fully capture the long-term variation in precipitation that has shaped the evolution of germination timing in these species.…”

Section: Discussionmentioning

confidence: 99%

Predicting Evolutionarily Stable Strategies from Functional Responses of Sonoran Desert Annuals to Precipitation

Cuello

Gremer

Trimmer³

et al. 2018

Preprint

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For many decades, researchers have studied how plants use bet-hedging strategies to insure against unpredictable, unfavorable conditions. We consider how the survival rates of dormant seeds (in a 'seed bank') interact with functional trade-offs to influence optimal germination strategies. Specifically, we explore the functional trade-offs between resource-use capacity and low-resource tolerance, i.e., being able to generate high yield following high rainfall versus maintain performance during a drought. We develop a model that explicitly includes these trade-offs to model fitness as a function of precipitation, and identifies evolutionarily stable strategies (ESS), using data from 10 Sonoran Desert annual plant species. We use our estimated ESS values to predict observed germination fractions. We then explore the relative importance of seed survival and functional trade-offs in driving optimal germination strategies by regressing ESS values and observed germination fractions against these traits.We find survival rates and functional trade-offs to be significant drivers for bet-hedging with survival rates having the strongest influence. Our results offer insight into drivers of bethedging strategies in an iconic system, as well as provide the analytical framework to explore how current or future environmental conditions will impact life history evolution.

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Accelerated seedling emergence in interspecific competitive neighbourhoods

Cited by 75 publications

References 35 publications

Cage Matching: Head to Head Competition Experiments of an Invasive Plant Species from Different Regions as a Means to Test for Differentiation

Cage Matching: Head to Head Competition Experiments of an Invasive Plant Species from Different Regions as a Means to Test for Differentiation

Local Adaptation, Patterns of Selection, and Gene Flow in the Californian Serpentine Sunflower (Helianthus Exilis)

Predicting Evolutionarily Stable Strategies from Functional Responses of Sonoran Desert Annuals to Precipitation

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