Dataset Information

Genetic and functional variation in denitrifier populations along a short-term restoration chronosequence.

ABSTRACT: Complete removal of plants and soil to exposed bedrock, in order to eradicate the Hole-in-the-Donut (HID) region of the Everglades National Park, FL, of exotic invasive plants, presented the opportunity to monitor the redevelopment of soil and the associated microbial communities along a short-term restoration chronosequence. Sampling plots were established for sites restored in 1989, 1997, 2000, 2001, and 2003. The goal of this study was to characterize the activity and diversity of denitrifying bacterial populations in developing HID soils in an effort to understand changes in nitrogen (N) cycling during short-term primary succession. Denitrifying enzyme activity (DEA) was detected in soils from all sites, indicating a potential for N loss via denitrification. However, no correlation between DEA and time since disturbance was observed. Diversity of bacterial denitrifiers in soils was characterized by sequence analysis of nitrite reductase genes (nirK and nirS) in DNA extracts from soils ranging in nitrate concentrations from 1.8 to 7.8 mg kg(-1). High levels of diversity were observed in both nirK and nirS clone libraries. Statistical analyses of clone libraries suggest a different response of nirS- and nirK-type denitrifiers to factors associated with soil redevelopment. nirS populations demonstrated a linear pattern of succession, with individual lineages represented at each site, while multiple levels of analysis suggest nirK populations respond in a grouped pattern. These findings suggest that nirK communities are more sensitive than nirS communities to environmental gradients in these soils.

SUBMITTER: Smith JM

PROVIDER: S-EPMC2547028 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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Genetic and functional variation in denitrifier populations along a short-term restoration chronosequence.

Smith Jason M JM Ogram Andrew A

Applied and environmental microbiology 20080718 18

Complete removal of plants and soil to exposed bedrock, in order to eradicate the Hole-in-the-Donut (HID) region of the Everglades National Park, FL, of exotic invasive plants, presented the opportunity to monitor the redevelopment of soil and the associated microbial communities along a short-term restoration chronosequence. Sampling plots were established for sites restored in 1989, 1997, 2000, 2001, and 2003. The goal of this study was to characterize the activity and diversity of denitrifyin ...[more]

PMID: 18641159

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Project description:With the increasing frequency of large-scale restoration efforts, the need to understand the adaptive genetic structure of natural plant populations and their relation to heavily utilized cultivars is critical. Bouteloua gracilis (blue grama) is a wind-dispersed, perennial grass consisting of several cytotypes (2n = 2×-6×) with a widespread distribution in western North America. The species is locally dominant and used regularly in restoration treatments. Using amplified fragment length polymorphism (AFLP) and cpDNA analyses, we assessed the genetic variability and adaptive genetic structure of blue grama within and among 44 sampling sites that are representative of the species' environmental and habitat diversity in the southwestern United States. Five cultivars were also included to investigate genetic diversity and differentiation in natural versus cultivated populations. Three main findings resulted from this study: (a) Ninety-four polymorphic AFLP markers distinguished two population clusters defined largely by samples on and off the Colorado Plateau; (b) substructure of samples on the Colorado Plateau was indicated by genetic divergence between boundary and interior regions, and was supported by cytotype distribution and cpDNA analysis; and (c) six AFLP markers were identified as "outliers," consistent with being under selection. These loci were significantly correlated to mean annual temperature, mean annual precipitation, precipitation of driest quarter, and precipitation of wettest quarter in natural populations, but not in cultivated samples. Marker × environment relationships were found to be largely influenced by cytotype and cultivar development. Our results demonstrate that blue grama is genetically variable, and exhibits genetic structure, which is shaped, in part, by environmental variability across the Colorado Plateau. Information from our study can be used to guide the selection of seed source populations for commercial development and long-term conservation management of B. gracilis, which could include genetic assessments of diversity and the adaptive potential of both natural and cultivated populations for wildland restoration.

Project description:Offspring size is a key functional trait that can affect subsequent life history stages; in many species, it exhibits both local adaptation and phenotypic plasticity. Variation among populations in offspring size may be explained by various factors, including local climatic conditions. However, geographic variation in climate may be partitioned into long-term and interannual sources of variation, which may differ in their effects on population mean offspring size. To assess environmental correlates of offspring size, we evaluated geographic variation in seed mass among 88 populations representing 6 species of Streptanthus (Brassicaceae) distributed across a broad climatic gradient in California. We examined the effects of temperature-mediated growing season length and precipitation on population mean seed mass to determine whether it is best explained by (1) long-term mean climatic conditions; (2) interannual climate anomalies (i.e., deviations in climate from long-term means) during the year of seed development, or (3) interactions between climate variables. Both long-term mean climate and climate anomalies in the year of collection were associated with population mean seed mass, but their effects differed in direction and magnitude. Relatively large seeds were produced at chronically wet sites but also during drier-than-average years. This contrast indicates that these associations may be generated by different mechanisms (i.e., adaptive evolution vs. phenotypic plasticity) and may be evidence of countergradient plasticity in seed mass. In addition, populations occurring in locations characterized by relatively long growing seasons produced comparatively large seeds, particularly among chronically dry sites. This study highlights the need to consider that the responses of seed mass to long-term versus recent climatic conditions may differ and that climate variables may interact to predict seed mass. Such considerations are especially important when using these patterns to forecast the long- and short-term responses of seed mass to climate change. The results presented here also contribute to our broader understanding of how climate drives long-term (e.g., local adaptation) and short-term (e.g., phenotypic plasticity) variation in functional traits, such as offspring size across landscapes.

Dataset Information

Genetic and functional variation in denitrifier populations along a short-term restoration chronosequence.

Publications

Genetic and functional variation in denitrifier populations along a short-term restoration chronosequence.

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