Disturbance Alters the Phylogenetic Composition and Structure of Plant Communities in an Old Field System

Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
PLoS ONE (Impact Factor: 3.23). 09/2009; 4(9):e7071. DOI: 10.1371/journal.pone.0007071
Source: PubMed


The changes in phylogenetic composition and structure of communities during succession following disturbance can give us insights into the forces that are shaping communities over time. In abandoned agricultural fields, community composition changes rapidly when a field is plowed, and is thought to reflect a relaxation of competition due to the elimination of dominant species which take time to re-establish. Competition can drive phylogenetic overdispersion, due to phylogenetic conservation of 'niche' traits that allow species to partition resources. Therefore, undisturbed old field communities should exhibit higher phylogenetic dispersion than recently disturbed systems, which should be relatively 'clustered' with respect to phylogenetic relationships. Several measures of phylogenetic structure between plant communities were measured in recently plowed areas and nearby 'undisturbed' sites. There was no difference in the absolute values of these measures between disturbed and 'undisturbed' sites. However, there was a difference in the 'expected' phylogenetic structure between habitats, leading to significantly lower than expected phylogenetic diversity in disturbed plots, and no difference from random expectation in 'undisturbed' plots. This suggests that plant species characteristic of each habitat are fairly evenly distributed on the shared species pool phylogeny, but that once the initial sorting of species into the two habitat types has occurred, the processes operating on them affect each habitat differently. These results were consistent with an analysis of correlation between phylogenetic distance and co-occurrence indices of species pairs in the two habitat types. This study supports the notion that disturbed plots are more clustered than expected, rather than 'undisturbed' plots being more overdispersed, suggesting that disturbed plant communities are being more strongly influenced by environmental filtering of conserved niche traits.

    • "We discuss whether dispersal traits mark transitions from one successional stage to the next and we discuss the mechanisms governing changes in dispersal traits over time. At our study sites, progressive succession resulted in species rich plant assemblages within a relatively short time span and therefore provides ideal means for studying patterns and processes of community assembly (Dinnage, 2009). "
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    ABSTRACT: Succession is a key ecological process that supports our understanding of community assembly and biotic interactions. Dispersal potential and dispersal strategies, such as wind- or animal-dispersal, have been assumed to be highly relevant for the success of plant species during succession. However, research yielded varying results on changes in dispersal modes between successional stages. Here, we test the hypotheses that (a) vascular plant species that use a number of dispersal modes dominate in early stages of succession while species specialized on one/few dispersal modes increase in abundance towards later stages of succession; (b) species well adapted to wind-dispersal (anemochory) will peak in abundance in early successional stages and (c) species well adapted to adhesive dispersal (epizoochory) will increase with proceeding succession. We test these hypotheses in four sites within agriculturally dominated landscapes in Germany. Agricultural use in these sites was abandoned 20–28 years ago, leaving them to secondary succession. Sites have been monitored for plant biodiversity ever since. We analyze changes in plant species richness and abundance, number of dispersal modes and two ranking indices for wind- and adhesive dispersal by applying generalized linear mixed-effect models. We used both abundance-weighted and unweighted dispersal traits in order to gain a comprehensive picture of successional developments. Hypothesis (a) was supported by unweighted but not abundance-weighted data. Anemochory showed no consistent changes across sites. In contrast, epizoochory (especially when not weighted by abundance) turned out to be an indicator of the transition from early to mid-successional stages. It increased for the first 9–16 years of succession but declined afterwards. Species richness showed an opposing pattern, while species abundance increased asymptotically. We suggest that plant-animal interactions play a key role in mediating these processes: By importing seeds of highly competitive plant species, animals are likely to promote the increasing abundance of a few dominant, highly epizoochorous species. These species outcompete weak competitors and species richness decreases. However, animals should as well promote the subsequent increase of species richness by disturbing the sites and creating small open patches. These patches are colonized by weaker competitors that are not necessarily dispersed by animals. The changes in the presence of epizoochorous species indicate the importance of plant traits and related plant–animal interactions in the succession of plant communities.
    No preview · Article · Nov 2015 · Ecological Indicators
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    • "This method was first used in the studies of plant communities (e.g. Webb, 2000; Dinnage, 2009; Parmentier et al., 2014; de Freitas et al., 2014), but is now increasingly used to analyze the community assembly of mycorrhizal fungi (e.g. Lim and Berbee, 2013; Grilli et al., 2014; Horn et al., 2014; Rinc on et al., 2014; Shi et al., 2014). "
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    ABSTRACT: Understanding the underlying mechanisms driving responses of belowground communities to increasing soil fertility will facilitate predictions of ecosystem responses to anthropogenic eutrophication of terrestrial systems. We studied the impact of fertilization of an alpine meadow on arbuscular mycorrhizal (AM) fungi, a group of root-associated microorganisms that are important in maintaining sustainable ecosystems. Species and phylogenetic composition of AM fungal communities in soils were compared across a soil fertility gradient generated by 8 years of combined nitrogen and phosphorus fertilization. Phylogenetic patterns were used to infer the ecological processes structuring the fungal communities. We identified 37 AM fungal virtual taxa, mostly in the genus Glomus. High fertilizer treatments caused a dramatic loss of Glomus species, but a significant increase in genus richness and a shift towards dominance of the lineage of Diversispora. AM fungal communities were phylogenetically clustered in unfertilized soil, random in the low fertilizer treatment and over-dispersed in the high fertilizer treatments, suggesting that the primary ecological process structuring communities shifted from environmental filtering (selection by host plants and fungal niches) to a stochastic process and finally to competitive exclusion across the fertilization gradient. Our findings elucidate the community shifts associated with increased soil fertility, and suggest that high fertilizer inputs may change the dominant ecological processes responsible for the assembly of AM fungal communities towards increased competition as photosynthate from host plants becomes an increasingly limited resource.
    Full-text · Article · Oct 2015 · Soil Biology and Biochemistry
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    • "Under the assumption of phylogenetic niche conservatism (the niche-related traits are similar among closely related lineages), in theory, the environmental filtering and competitive exclusion should generate patterns of phylogenetical clustering and overdispersion, respectively (Webb et al. 2002). This method was widely used in the studies of plant community (Dinnage 2009; Yang et al. 2012; Parmentier et al. 2014), but in recent years it has been increasingly used to analyze the communities of mycorrhizal fungi (Kivlin et al. 2011; Lim and Berbee 2013; Horn et al. 2014; Rincón et al. 2014; Saks et al. 2014; Shi et al. 2014b) and other microbes (Pontarp et al. 2012; Wang et al. 2013). Since the functional traits of AMF have been shown to be conserved (Powell et al. 2009; Maherali and Klironomos 2012), the ecological processes driving AMF assemblages can be efficiently inferred from the community phylogenetic structure (e.g. "
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    ABSTRACT: Background and aims Understanding the role of resource availability in structuring biotic communities is of importance in community ecology. This study investigates how light and soil nutrient availability drive assemblages of both plants and their root-associated arbuscular mycorrhizal fungi (AMF). Methods We conducted a 4-year light [full light or shade] and soil fertility [unfertilized or fertilized with (NH4)2HPO4] interactive manipulations in an alpine meadow ecosystem. Species and phylogenetic compositions of plant and AMF communities were simultaneously measured, and the primary ecological processes structuring both communities were inferred from the community phylogenetic analysis. Results Reducing light and/or increasing soil fertility significantly reduced species richness and changed community compositions of both plant and AMF. Plant community phylogenetic structure shifted from random in untreated control to overdispersion in other treatments, whereas AMF communities were phylogenetically clustered and random in unfertilized and fertilized plots, respectively. These results suggest that plant communities in treated plots were mainly determined by competitive exclusion, and that AMF communities in unfertilized and fertilized plots were determined by environmental filtering and random process, respectively. Conclusions We observed strong effects of light and soil nutrient availability on both plant and AMF communities, and our findings highlight that the primary ecological processes that drive plant and AMF assemblages should be highly dependent on the level of resource availability.
    Full-text · Article · Sep 2014 · Plant and Soil
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