Plant population and community ecologist. Interests in grasslands and forests, invasive species, restoration, phylogenetics. Just so long as I don't have to get my feet wet.
In 2009, a derecho occurred in southern Illinois affecting large areas of the regional forest sys... more In 2009, a derecho occurred in southern Illinois affecting large areas of the regional forest systems. Previous research reported multi-strata species compositional shifts post-derecho at LaRue Pine Hills/Otter Pond Research Natural Area (LPH/OP RNA). Here, we expand these observations to include phylogenetic and spatial relationships, including elevation as a covariate. Surveys were conducted before and after the derecho. Univariate and multivariate analyses documented diversity and compositional shifts. Spatial analyses identified distinct spatial patterns in taxonomic (TSR) and phylogenetic (PSR) species richness, and metrics of phylogenetic clustering and overdispersion (net relatedness index and nearest taxon index; NRI and NTI, respectively), in seedling, sapling, and tree communities. Decreases in tree TSR and PSR and sapling PSR, and increases in sapling NTI occurred post-derecho. Seedling diversity-elevational relationships exhibited a humped-backed relationship in all case...
Pollinator declines have been documented globally, but little information is available about nati... more Pollinator declines have been documented globally, but little information is available about native bee ecology in Midwestern U.S. agriculture. This project seeks to optimize pollinator support and weed suppression in a 3-yr crop rotation with a fallow growing season. During fallow, one of five cover crop treatments (T1: crimson, red, and ladino clover and Bob oats [Fabales: Fabaceae - Trifolium incarnatum L., Trifolium pratense L., Trifolium repens L., and Cyperales: Poaceae - Avena sativa]; T2: crimson clover and oats; T3: red clover and oats; T4: ladino clover and oats; T5: no cover crop; T6/control: winter wheat [Cyperales: Poaceae - Triticum aestivum] L.) was seeded in one-half of 25 agricultural fields, whereas wheat was left unharvested in the other half as a comparison. Treatments that provide season-long floral resources support the greatest bee diversity and abundance (T1), and treatments with red clover support declining (Hymenoptera: Apidae) Bombus species (T1 and T3). L...
Two dominant species, Andropogon gerardii and Sorghastrum nutans, have a wide distribution across... more Two dominant species, Andropogon gerardii and Sorghastrum nutans, have a wide distribution across the Great Plains (USA) and are widely used in restorations. We ask: Do dominant species' ecotypes influence community diversity and structure evenly across a longitudinal aridity gradient? We established reciprocal common gardens at four sites across the gradient. Ecotypes of the two dominant species were seeded along with a prairie seed mix according to a randomized complete block design. Species composition was measured after 3 and 10 years. We used linear mixed models to analyze the effect of the ecotype and year on community diversity. NMDS and PERMANOVA were applied to examine the contribution of ecotype to community structure. Results showed that ecotype significantly affected species richness and shaped taxonomic, phylogenetic, and functional diversity. Accordingly, restorations should consider ecotypic variation as a critical biological filter to community assembly in grassl...
Background Few studies have incorporated the evolutionary insights provided by analysis of phylog... more Background Few studies have incorporated the evolutionary insights provided by analysis of phylogenetic structure along with community composition to assess the effects of exotic invasion on freshwater wetlands. Here, we assess the taxonomic and phylogenetic relationships among acid seep springs to investigate the potential homogenization or resistance of communities due to invasion of an exotic grass. Results Multivariate community analyses indicated differences in community and phylogenetic composition and dispersion among acid seep springs, associated with gradients in soil moisture, canopy cover, and phylogenetic diversity. By contrast, univariate analyses showed differences in taxonomic diversity but not phylogenetic diversity among acid seep springs. Conclusions Despite exotic invasion, individual acid seep springs remained taxonomically and phylogenetically distinct from each other. Taxonomic and phylogenetic diversity metrics revealed different aspects of composition, reinfo...
AimsThe productivity–plant diversity relationship is a central subject in ecology under debate fo... more AimsThe productivity–plant diversity relationship is a central subject in ecology under debate for decades. Anthropogenic disturbances have been demonstrated to affect productivity and plant diversity. However, the impact of disturbances on the productivity–diversity relationship is poorly understood.LocationAn old‐field located at the Touch of Nature Environmental Center in Jackson County, Illinois, USA.MethodsA manipulative experiment with fertilizer (unfertilized, fertilized annually, fertilized every five years) and mowing (unmowed, mowed in spring only, mowed in spring and fall) in a successional old‐field began in 1996 to examine disturbance effects on above‐ground net primary productivity (ANPP)–plant diversity relationships. Taxonomic (species richness, T0) and phylogenetic (net relatedness index, NRI) diversity were selected as potential plant diversity metrics.ResultsA unimodal relationship of ANPP with T0 and a negative relationship between ANPP and NRI were found across ...
Amaranthus palmeri S. Watson (Palmer amaranth) is a fast-growing, dioecious, highly competitive a... more Amaranthus palmeri S. Watson (Palmer amaranth) is a fast-growing, dioecious, highly competitive agricultural weed species, which is spreading across the US Midwest. Population sex ratios are an important consideration in the management of A. palmeri populations as this species has become resistant to several herbicide sites of action, and there is need to minimize seed production by female plants. Environmental conditions, particularly stressors, may influence sex ratios, and herbicides act as major stressors and evolutionary filters in agricultural fields. Amaranthus spp. have shown a tendency for rapid evolution of herbicide resistance, with the frequency of protoporphyrinogen oxidase (PPO)-inhibitor resistance increasing across the Midwestern US. A greenhouse experiment was conducted to investigate the effect of two PPO-inhibiting herbicide treatments of either lactofen or fomesafen on four different Illinois populations (Cahokia, Collinsville, Rend Lake, and Massac). Plants rais...
Intraspecific competition is an important plant interaction that has been studied extensively abo... more Intraspecific competition is an important plant interaction that has been studied extensively aboveground, but less so belowground, due to the difficulties in accessing the root system experimentally. Recent in vivo and in situ automatic imaging advances help understand root system architecture. In this study, a portable imaging platform and a scalable transplant technique were applied to test intraspecific competition in Arabidopsis thaliana. A single green fluorescent protein labeled plant was placed in the center of a grid of different planting densities of neighboring unlabeled plants or empty spaces, into which different treatments were made to the media. The root system of the central plant showed changes in the vertical distribution with increasing neighbor density, becoming more positively kurtotic, and developing an increasing negative skew with time. Horizontal root distribution was initially asymmetric, but became more evenly circular with time, and mean direction was not...
Sudden death syndrome (SDS) caused by Fusarium virguliforme is a widespread and economically impo... more Sudden death syndrome (SDS) caused by Fusarium virguliforme is a widespread and economically important disease of soybean. SDS is typically distributed unevenly in patches across soybean fields. While certain spots in fields are highly conducive to the development of severe SDS, other areas appear to be naturally healthy or suppressive to the disease. The role of soil microbial communities and soil physical and chemical properties in SDS development was investigated in 45 soybean fields in Illinois, Iowa, and Minnesota. Soil samples were collected from symptomatic patches in fields and from adjacent areas where SDS foliar symptoms did not develop. Multiple edaphic factors were measured, and markers specific to bacteria, fungi, archaea, oomycete, and nematodes, coupled with Illumina MiSeq sequencing, were used to identify key taxa likely associated with SDS development. A total of 14,200,000 reads were mapped against the National Center for Biotechnology Information nucleotide databa...
Agricultural environments allow study of evolutionary change in plants. An example of evolution w... more Agricultural environments allow study of evolutionary change in plants. An example of evolution within agroecological systems is the selection for resistance to the herbicide glyphosate within the weed, Conyza canadensis. Changes in survivorship and reproduction associated with the development of glyphosate resistance (GR) may impact fitness and influence the frequency of occurrence of the GR trait. We hypothesized that site characteristics and history would affect the occurrence of GR C. canadensis in field margins. We surveyed GR occurrence in field margins and asked whether there were correlations between GR occurrence and location, crop rotation, GR crop trait rotation, crop type, use of tillage, and the diversity of herbicides used. In a field experiment, we hypothesized that there would be no difference in fitness between GR and glyphosate-susceptible (GS) plants. We asked whether there were differences in survivorship, phenology, reproduction, and herbivory between 2 GR and 2...
Random amplified polymorphic DNA (RAPD) analysis was used to characterize genetic diversity and g... more Random amplified polymorphic DNA (RAPD) analysis was used to characterize genetic diversity and genetic distinctiveness of Andropogon gerardii from remnant Arkansas prairies. Six oligonucleotide primers, which generated 37 RAPD bands, were used to analyse 30–32 plants from six Grand Prairie populations, Baker Prairie (Arkansas Ozarks), two Illinois prairies and two cultivars. Genetic diversity of the Arkansas remnants ranged from 82.7 to 99.3%, with 89% of the total genetic variation within and 11% among populations. The partitioning of genetic variation was consistent with that reported for other outcrossing perennial grasses, using the more conservative allozyme markers. Principal component analysis indicated a northern and southern association within Arkansas’ Grand Prairie. Although there was no genetic structuring at the landscape level, the Illinois prairies and cultivars were different from all Arkansas prairies tested. There was significant within‐population structuring in f...
In 2009, a derecho occurred in southern Illinois affecting large areas of the regional forest sys... more In 2009, a derecho occurred in southern Illinois affecting large areas of the regional forest systems. Previous research reported multi-strata species compositional shifts post-derecho at LaRue Pine Hills/Otter Pond Research Natural Area (LPH/OP RNA). Here, we expand these observations to include phylogenetic and spatial relationships, including elevation as a covariate. Surveys were conducted before and after the derecho. Univariate and multivariate analyses documented diversity and compositional shifts. Spatial analyses identified distinct spatial patterns in taxonomic (TSR) and phylogenetic (PSR) species richness, and metrics of phylogenetic clustering and overdispersion (net relatedness index and nearest taxon index; NRI and NTI, respectively), in seedling, sapling, and tree communities. Decreases in tree TSR and PSR and sapling PSR, and increases in sapling NTI occurred post-derecho. Seedling diversity-elevational relationships exhibited a humped-backed relationship in all case...
Pollinator declines have been documented globally, but little information is available about nati... more Pollinator declines have been documented globally, but little information is available about native bee ecology in Midwestern U.S. agriculture. This project seeks to optimize pollinator support and weed suppression in a 3-yr crop rotation with a fallow growing season. During fallow, one of five cover crop treatments (T1: crimson, red, and ladino clover and Bob oats [Fabales: Fabaceae - Trifolium incarnatum L., Trifolium pratense L., Trifolium repens L., and Cyperales: Poaceae - Avena sativa]; T2: crimson clover and oats; T3: red clover and oats; T4: ladino clover and oats; T5: no cover crop; T6/control: winter wheat [Cyperales: Poaceae - Triticum aestivum] L.) was seeded in one-half of 25 agricultural fields, whereas wheat was left unharvested in the other half as a comparison. Treatments that provide season-long floral resources support the greatest bee diversity and abundance (T1), and treatments with red clover support declining (Hymenoptera: Apidae) Bombus species (T1 and T3). L...
Two dominant species, Andropogon gerardii and Sorghastrum nutans, have a wide distribution across... more Two dominant species, Andropogon gerardii and Sorghastrum nutans, have a wide distribution across the Great Plains (USA) and are widely used in restorations. We ask: Do dominant species' ecotypes influence community diversity and structure evenly across a longitudinal aridity gradient? We established reciprocal common gardens at four sites across the gradient. Ecotypes of the two dominant species were seeded along with a prairie seed mix according to a randomized complete block design. Species composition was measured after 3 and 10 years. We used linear mixed models to analyze the effect of the ecotype and year on community diversity. NMDS and PERMANOVA were applied to examine the contribution of ecotype to community structure. Results showed that ecotype significantly affected species richness and shaped taxonomic, phylogenetic, and functional diversity. Accordingly, restorations should consider ecotypic variation as a critical biological filter to community assembly in grassl...
Background Few studies have incorporated the evolutionary insights provided by analysis of phylog... more Background Few studies have incorporated the evolutionary insights provided by analysis of phylogenetic structure along with community composition to assess the effects of exotic invasion on freshwater wetlands. Here, we assess the taxonomic and phylogenetic relationships among acid seep springs to investigate the potential homogenization or resistance of communities due to invasion of an exotic grass. Results Multivariate community analyses indicated differences in community and phylogenetic composition and dispersion among acid seep springs, associated with gradients in soil moisture, canopy cover, and phylogenetic diversity. By contrast, univariate analyses showed differences in taxonomic diversity but not phylogenetic diversity among acid seep springs. Conclusions Despite exotic invasion, individual acid seep springs remained taxonomically and phylogenetically distinct from each other. Taxonomic and phylogenetic diversity metrics revealed different aspects of composition, reinfo...
AimsThe productivity–plant diversity relationship is a central subject in ecology under debate fo... more AimsThe productivity–plant diversity relationship is a central subject in ecology under debate for decades. Anthropogenic disturbances have been demonstrated to affect productivity and plant diversity. However, the impact of disturbances on the productivity–diversity relationship is poorly understood.LocationAn old‐field located at the Touch of Nature Environmental Center in Jackson County, Illinois, USA.MethodsA manipulative experiment with fertilizer (unfertilized, fertilized annually, fertilized every five years) and mowing (unmowed, mowed in spring only, mowed in spring and fall) in a successional old‐field began in 1996 to examine disturbance effects on above‐ground net primary productivity (ANPP)–plant diversity relationships. Taxonomic (species richness, T0) and phylogenetic (net relatedness index, NRI) diversity were selected as potential plant diversity metrics.ResultsA unimodal relationship of ANPP with T0 and a negative relationship between ANPP and NRI were found across ...
Amaranthus palmeri S. Watson (Palmer amaranth) is a fast-growing, dioecious, highly competitive a... more Amaranthus palmeri S. Watson (Palmer amaranth) is a fast-growing, dioecious, highly competitive agricultural weed species, which is spreading across the US Midwest. Population sex ratios are an important consideration in the management of A. palmeri populations as this species has become resistant to several herbicide sites of action, and there is need to minimize seed production by female plants. Environmental conditions, particularly stressors, may influence sex ratios, and herbicides act as major stressors and evolutionary filters in agricultural fields. Amaranthus spp. have shown a tendency for rapid evolution of herbicide resistance, with the frequency of protoporphyrinogen oxidase (PPO)-inhibitor resistance increasing across the Midwestern US. A greenhouse experiment was conducted to investigate the effect of two PPO-inhibiting herbicide treatments of either lactofen or fomesafen on four different Illinois populations (Cahokia, Collinsville, Rend Lake, and Massac). Plants rais...
Intraspecific competition is an important plant interaction that has been studied extensively abo... more Intraspecific competition is an important plant interaction that has been studied extensively aboveground, but less so belowground, due to the difficulties in accessing the root system experimentally. Recent in vivo and in situ automatic imaging advances help understand root system architecture. In this study, a portable imaging platform and a scalable transplant technique were applied to test intraspecific competition in Arabidopsis thaliana. A single green fluorescent protein labeled plant was placed in the center of a grid of different planting densities of neighboring unlabeled plants or empty spaces, into which different treatments were made to the media. The root system of the central plant showed changes in the vertical distribution with increasing neighbor density, becoming more positively kurtotic, and developing an increasing negative skew with time. Horizontal root distribution was initially asymmetric, but became more evenly circular with time, and mean direction was not...
Sudden death syndrome (SDS) caused by Fusarium virguliforme is a widespread and economically impo... more Sudden death syndrome (SDS) caused by Fusarium virguliforme is a widespread and economically important disease of soybean. SDS is typically distributed unevenly in patches across soybean fields. While certain spots in fields are highly conducive to the development of severe SDS, other areas appear to be naturally healthy or suppressive to the disease. The role of soil microbial communities and soil physical and chemical properties in SDS development was investigated in 45 soybean fields in Illinois, Iowa, and Minnesota. Soil samples were collected from symptomatic patches in fields and from adjacent areas where SDS foliar symptoms did not develop. Multiple edaphic factors were measured, and markers specific to bacteria, fungi, archaea, oomycete, and nematodes, coupled with Illumina MiSeq sequencing, were used to identify key taxa likely associated with SDS development. A total of 14,200,000 reads were mapped against the National Center for Biotechnology Information nucleotide databa...
Agricultural environments allow study of evolutionary change in plants. An example of evolution w... more Agricultural environments allow study of evolutionary change in plants. An example of evolution within agroecological systems is the selection for resistance to the herbicide glyphosate within the weed, Conyza canadensis. Changes in survivorship and reproduction associated with the development of glyphosate resistance (GR) may impact fitness and influence the frequency of occurrence of the GR trait. We hypothesized that site characteristics and history would affect the occurrence of GR C. canadensis in field margins. We surveyed GR occurrence in field margins and asked whether there were correlations between GR occurrence and location, crop rotation, GR crop trait rotation, crop type, use of tillage, and the diversity of herbicides used. In a field experiment, we hypothesized that there would be no difference in fitness between GR and glyphosate-susceptible (GS) plants. We asked whether there were differences in survivorship, phenology, reproduction, and herbivory between 2 GR and 2...
Random amplified polymorphic DNA (RAPD) analysis was used to characterize genetic diversity and g... more Random amplified polymorphic DNA (RAPD) analysis was used to characterize genetic diversity and genetic distinctiveness of Andropogon gerardii from remnant Arkansas prairies. Six oligonucleotide primers, which generated 37 RAPD bands, were used to analyse 30–32 plants from six Grand Prairie populations, Baker Prairie (Arkansas Ozarks), two Illinois prairies and two cultivars. Genetic diversity of the Arkansas remnants ranged from 82.7 to 99.3%, with 89% of the total genetic variation within and 11% among populations. The partitioning of genetic variation was consistent with that reported for other outcrossing perennial grasses, using the more conservative allozyme markers. Principal component analysis indicated a northern and southern association within Arkansas’ Grand Prairie. Although there was no genetic structuring at the landscape level, the Illinois prairies and cultivars were different from all Arkansas prairies tested. There was significant within‐population structuring in f...
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Papers by David Gibson