How functional traits, herbivory, and genetic diversity interact in<i>Echinacea</i>: implications for fragmented populations

Kittelson, Pamela M.; Wagenius, Stuart; Nielsen, Reina; Qazi, Sanjive; Howe, Michael; Kiefer, Gretel; Shaw, Ruth G.

doi:10.1890/14-1687.1

Cited by 13 publications

(6 citation statements)

References 85 publications

(80 reference statements)

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“…sponhemica from fragmented populations, found that most population trait means were significantly related to climate gradients, suggesting adaptive genetic differentiation in quantitative traits (see also Weber and Kolb, 2014; Ye et al, 2014). Likewise, Kittelson et al (2015) found that inbreeding significantly affected the expression of 12 functional traits in populations of the prairie forb Echinacea angustifolia , and Mannouris and Byers (2013) found a significant effect of genetic drift load on populations of Chamaecrista fasciculata from small fragments. In our study, lack of population differentiation in functional traits suggests a low impact of genetic drift and inbreeding on plant traits, and/or similar selective pressures acting on our populations due to similar microclimatic conditions (see also Ellmer et al, 2011).…”

Section: Discussionmentioning

confidence: 97%

Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic

et al. 2017

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Habitat fragmentation, i.e., fragment size and isolation, can differentially alter patterns of neutral and quantitative genetic variation, fitness and phenotypic plasticity of plant populations, but their effects have rarely been tested simultaneously. We assessed the combined effects of size and connectivity on these aspects of genetic and phenotypic variation in populations of Centaurea hyssopifolia, a narrow endemic gypsophile that previously showed performance differences associated with fragmentation. We grew 111 maternal families sampled from 10 populations that differed in their fragment size and connectivity in a common garden, and characterized quantitative genetic variation, phenotypic plasticity to drought for key functional traits, and plant survival, as a measure of population fitness. We also assessed neutral genetic variation within and among populations using eight microsatellite markers. Although C. hyssopifolia is a narrow endemic gypsophile, we found substantial neutral genetic variation and quantitative variation for key functional traits. The partition of genetic variance indicated that a higher proportion of variation was found within populations, which is also consistent with low population differentiation in molecular markers, functional traits and their plasticity. This, combined with the generally small effect of habitat fragmentation suggests that gene flow among populations is not restricted, despite large differences in fragment size and isolation. Importantly, population’s similarities in genetic variation and plasticity did not reflect the lower survival observed in isolated populations. Overall, our results indicate that, although the species consists of genetically variable populations able to express functional plasticity, such aspects of adaptive potential may not always reflect populations’ survival. Given the differential effects of habitat connectivity on functional traits, genetic variation and fitness, our study highlights the need to shift the focus of fragmentation studies to the mechanisms that regulate connectivity effects, and call for caution on the use of genetic variation and plasticity to forecast population performance.

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Section: Discussionmentioning

confidence: 97%

Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic

et al. 2017

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“…In small habitat patches, plant inbreeding may occur more frequently as population sizes diminish (Honnay et al, 2005;Leimu et al, 2010). Inbred plants may have altered nutritional quality and defensive responses (Ridley et al, 2011;Kittelson et al, 2015). Therefore, plant inbreeding has the potential to alter herbivore performance (Hull-Sanders and Eubanks, 2005).…”

Section: Bottom-up Mechanismsmentioning

confidence: 99%

Bottom-Up and Top-Down Effects of Forest Fragmentation Differ Between Dietary Generalist and Specialist Caterpillars

Anderson¹,

Dallar²,

Pirtel³

et al. 2019

Front. Ecol. Evol.

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Ecological interactions increasingly occur in the context of anthropogenic landscape alteration, such as landscape fragmentation, which engenders numerous changes to abiotic and biotic processes. Theory and empirical evidence suggest that species that are ecologically specialized or positioned at higher trophic levels are most sensitive to the effects of landscape fragmentation, yet the mechanisms underlying this sensitivity remain hypothetical. Here we present an initial test of the hypothesis that landscape fragmentation affects tri-trophic interactions more severely for dietary specialist than for generalist insect herbivores. We specifically tested a bottom-up hypothesis, that fragmentation reduces hostplant food quality to herbivores, with the most pronounced effects for dietary specialists. We also tested a top-down hypothesis, that fragmentation reduces parasitism of caterpillars, with the most pronounced effects on dietary specialists. We studied interactions among trees, caterpillars, and parasitoids in forest fragments (3-1013 ha) in Connecticut, U.S.A. in 2017 and 2018. To address the bottom-up hypothesis, we measured the growth performance of multiple dietary specialist and generalist caterpillar species fed leaves from red maple and witch hazel trees sampled from large or small forest patches. We assessed the top-down hypothesis by quantifying mortality from insect parasitoids of many of the same caterpillar species on these tree species sampled from a range of forest patch sizes. Fragmentation did not reduce herbivore growth performance for either dietary specialist or generalist caterpillars even though it accelerated desiccation rates of leaves of both tree species over the growing season. However, dietary specialization increased herbivore sensitivity to yearly variation in food quality, as the growth efficiency of specialist caterpillars varied between 2017 and 2018, while that of generalist caterpillars did not. As predicted, parasitism rates of dietary specialist caterpillars declined as forest fragment size declined, whereas parasitism of generalists was independent of fragment size. Therefore, interactions involving dietary specialist herbivores were most sensitive to top-down environmental variation. Assuming that dietary specialist caterpillars are primarily attacked by host-specific parasitoids, this Anderson et al. Effects of Forest Fragmentation on Tri-trophic Interactions top-down effect is consistent with the trophic theory of island biogeography, which predicts the sharpest declines of ecologically specialized predators and parasites in small habitat patches.

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“…More recently, Kittelson et al . () found numerous physiological differences among plants attributable to genotypic class, including lower photosynthetic rates, water use efficiencies, and specific leaf areas, as well as higher trichome numbers, % C and % N of inbreds compared to outbred individuals. The abundance of aphids in the year of that study was too low to detect associations with these plant attributes.…”

Section: Discussionmentioning

confidence: 99%

The susceptibility of Echinacea angustifolia to a specialist aphid: eco‐evolutionary perspective on genotypic variation and demographic consequences

2015

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Summary1. Plants and their herbivores may influence each other's fitness and, hence, genetic dynamics, as well as their demography. Conversely, variation in fitness-related traits may influence the occurrence or intensity of the interaction. Disentangling the fitness consequences of an interaction in nature from the influence of fitness variation on it is challenging, but important to clarifying the ecological and evolutionary dynamics of plants with their herbivores. 2. As part of a larger effort to elucidate eco-evolutionary dynamics in a population of Echinacea angustifolia that is subject to severe fragmentation, we initiated an experiment in 2001 to evaluate differences in fitness among plants of three genotypic classes resulting from matings of plants from different remnant populations ('between', B), plants randomly chosen from the same remnant ('within', W) and maternal siblings ('inbreds', I). The experiment was planted into a field undergoing restoration to a prairie community. Fitness components of individual plants were recorded through 2012. During 2004-2010, each plant was also monitored for its load of Aphis echinaceae, a specialist insect herbivore. 3. Within a season, aphid-load depended consistently on a plant's location and on its load the previous season. Further, flowering individuals generally harboured more aphids than non-flowering plants. In analyses of overall plant fitness, within each genotypic class, fitness was greatest for plants with the greatest aphid-loads, consistent with the preference of aphids for flowering individuals. Inbreeding depression was severe, with I plants producing 60% fewer achenes than W or B plants, and varied with aphid-load. To distinguish the role of aphid choice from the effect of aphid herbivory in the relationship between plant fitness and aphid-load, we evaluated how components of fitness varied with prior aphid-load. Notably, genotype I plants with high aphid-loads the previous year produced far fewer achenes per flower head than those that carried fewer aphids. 4. Synthesis. Sibmating reduces individuals' demographic contribution by 60% over the first 12 years. Outbred individuals tolerate this aphid; each produces on average about 200 achenes per head in a year, despite a heavy aphid-load the previous year. However, inbreeding, which is greater in severely fragmented prairie habitat, results in poor tolerance. Aphid herbivory exacerbates inbreeding depression, further reducing the contribution of those individuals to population growth. This study illustrates an approach that helps to distinguish fitness-dependent attraction of herbivores from the effects of herbivory on plant fitness and demography, a goal that is critically important to eco-evolutionary understanding.

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How functional traits, herbivory, and genetic diversity interact inEchinacea: implications for fragmented populations

Cited by 13 publications

References 85 publications

Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic

Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic

Bottom-Up and Top-Down Effects of Forest Fragmentation Differ Between Dietary Generalist and Specialist Caterpillars

The susceptibility of Echinacea angustifolia to a specialist aphid: eco‐evolutionary perspective on genotypic variation and demographic consequences

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