Biology subjects

Obregon, D.

Publications and source records attributed to Obregon, D..

6 recordsLinked to original sources

bioRxiv2025

Squash flowers as microhabitats: the effects of floral temperature and humidity on pollen viability and visitor behavior

Flowers represent intricate microcosms shaped by their chemical and micrometeorological properties. Notable examples include thermogenic flowers that create a warm microclimate for visitors and residents. We document a distinct microclimate within the large flowers of both wild and domesticated squashes (Cucurbita spp.). Unlike thermogenic flowers, squash flower temperatures remain near ambient, but their humidity consistently exceeds ambient levels from bud to senescence, resulting from stomatal and petal transpiration rather than nectar evaporation. Experimentally reducing humidity in greenhouse-grown male squash flowers results in significant pollen tube rupture, directly impacting plant fitness. To explore the role of floral humidity within a broader ecological context, we performed similar humidity manipulations on squash farms to assess impacts on the behavior of their specialist squash bee pollinator (Xenoglossa pruinosa), generalist pollinators (bumblebees, honeybees), and specialist herbivores (cucurbit beetles). Experimentally reduced floral humidity lower visitation frequency by squash bees but have no effect on generalist pollinators. Manipulation of floral humidity did not influence the foraging duration of any pollinators but impacted the residence of male squash bees in wilted flowers compared with unmanipulated flowers. Finally, there was a positive correlation between the dryness of the ambient air and the abundance of squash bees and cucurbit beetles residing in the humid wilted floral chambers. In conclusion, our findings showcase squash flowers as a humid microhabitat that influences reproductive success directly by affecting pollen viability and indirectly by altering interactions with squash bees, their specialist pollinators.

ecology↗

bioRxiv2024

Complex responses of soil prokaryotes, fungi and protists to prairie restoration on retired agricultural lands

Restoring native ecosystems on marginal croplands has many benefits but the impacts on belowground biodiversity are less clear, in part because the limiting factors regulating soil biota are complex and poorly described. Here, we studied how grassland prairie restoration of marginal croplands affected the diversity and composition of soil microbiota on 5 conventional farms from Ontario, Canada. Soil samples (0-15 cm) were collected from annually cultivated fields and adjacent planted perennial grassland where cultivation and chemical inputs had ceased several years previously. Following DNA extraction, we estimated bacterial and fungal abundance using quantitative PCR, and microbial diversity of prokaryotes, fungi and protists using amplicon high-throughput sequencing. Under both land uses, prokaryotic communities were dominated by Proteobacteria, Actinobacteria and Acidobacteria, fungal communities by Ascomycota, and protist communities by Rhizaria (TSAR), Evosea (Amoebozoa) and Chlorophyta (Archaeplastida). Prairie restoration did not have a consistent effect on soil microbial abundance, richness or evenness, which responses varied across farms. Microbial genetic and taxonomic community composition (i.e., sequence variant and genus level) were affected by land use, farm and the interaction between these two factors. Generally, prairie soils had higher relative abundance of Latescibacterota, Desulfobacterota, Acidobacteriota and Glomeromycota, and lower of Deinococcota, Chytridiomycota and Amoebozoa_X. In terms of differentially abundant fungal genera, prairies promoted more fungal plant symbionts, less saprotrophs and no plant pathogens. Interkingdom networks revealed changes in potential microbe-microbe associations with prairie restoration, with only 8 associations in common between land uses. The relationship between soil microbial diversity and physicochemical properties varied across microbial groups, diversity metrics and land uses. Our results evidence the complexity associated with restoring soils from agricultural land to natural ecosystems, with unspecified farm-specific factors (e.g., soil type, prairie species, management history) strongly modulating the response of different microbial groups and variables.

microbiology↗

bioRxiv2024

Liming pasture soils in the Amazon region promotes low-affinity methane oxidation by type I and II methanotrophs

In the Amazon Forest region, cattle pastures are the main land use subsequent to deforestation. This land-use change affects the soil microbial community and methane fluxes, shifting the soil from a methane sink to a source. Soil physical and chemical attributes are changed due to slash-and-burn processes, including an increased soil pH after forest-to-pasture conversion. Without amendments, the pasture soils can become acidic again resulting in many cases in soil degradation. Liming is a standard management practice to increase soil pH while decreasing Al3+ availability. Liming is important to recover these degraded lands and increase soil fertility, but its impact on soil methane cycling in tropical soils is unknown. Here we investigated the role of soil pH on methane uptake under high concentrations of the gas. The top layer of forest (pH 4.1) and adjacent pasture soils (pH 4.8) from the Eastern Amazon were subjected to liming treatment (final pH 5.8) and incubated with [~]10,000 ppm of 13CH4 for 24 days to label DNA with 13C. Soil DNA was evaluated with Stable Isotopic Probing (SIP-DNA), methanotrophic abundance was quantified (pmoA gene), and high throughput sequencing of 16S rRNA was performed. Liming increased the methane uptake in both forest ([~]10%) and pasture ([~]25%) soils. Methanotrophs Methylocaldum sp. (type I) and Beijerinckaceae (type II) were identified to actively incorporate carbon from methane in limed pasture soils. In limed forest soils, Nitrososphaeraceae, Lysobacter sp., and Acidothermus sp. were identified as 13C-enriched taxa. The enrichment of the archaeal family Nitrososphaeraceae, known as ammonia oxidizers, is correlated with an increase of ammonia monooxygenase genes, which code for an enzyme complex with wide substrate specificity that can also perform methane oxidation. In conclusion, liming Amazonian pasture soils not only contributes to the fertility and recovery of degraded areas but also has the potential to improve the oxidation of methane at high concentrations of this gas.

ecology↗

bioRxiv2022

Dynamics of methane cycling microbiome during methane flux hot moments from riparian buffer systems

Riparian buffer systems (RBS) are a common agroforestry practice that consists of keeping a forested boundary adjacent to water bodies in agricultural landscapes, thus helping to protect aquatic ecosystems from adverse impacts. Nevertheless, despite the multiple benefits they provide, RBSs can be hotspots of methane emissions since abundant organic carbon and high-water tables are often found in these soils. In southern Ontario, Canada, the rehabilitation of Washington Creeks streambank occurred in 1985. In a recent study, methane (CH4) fluxes were measured biweekly for two years (2017-2018) in four different vegetative riparian areas alongside Washington creek: a rehabilitated tree buffer (RH), a grassed buffer (GRB), an undisturbed deciduous forest (UNF), an undisturbed coniferous forest (CF), and an adjacent agricultural field (AGR) for comparison. Based on methane fluxes in 2018 and hot moments identified, we selected two dates from summer (July 04 and August 15) and use soil sampling from those days to assess the CH4 cycling microbial communities in these RBS. We used qPCR and high-throughput sequencing from both DNA and cDNA to measure the diversity and activity of the methanogen and methanotroph communities. Methanogens were abundant in all riparian soils, including the archaeal genera Methanosaeta, Methanosarcina, Methanomassiliicoccus Methanoreggula, but they were mostly active in UNF soils. Among methanotrophs, Methylocystis was the most abundant taxon in all the riparian sites, except for AGR soils where the methanotrophs community mostly comprised members of rice paddy clusters (RPCs and RPC-1) and upland soil clusters (TUSC and USC). In summary, these results indicate that differences in CH4 fluxes between RBS at Washington creek are influenced by differences in the presence and activity of methanogens, which were higher in the deciduous forest (UNF) soils during hot moments CH4 flux, likely due to high water content in that soils. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/517857v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@1dcde21org.highwire.dtl.DTLVardef@17b59e5org.highwire.dtl.DTLVardef@14adfb0org.highwire.dtl.DTLVardef@a3b411_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Anti-microbiota vaccines modulate the tick microbiome in a taxon-specific manner

Anti-tick microbiota vaccines have been shown to impact tick feeding but its specificity has not been demonstrated. In this study we aimed to investigate the impact of immune targeting of keystone microbiota bacteria on tick performance, and tick microbiota structure and function. Vaccination against Escherichia coli, the selected keystone taxon, increased tick engorgement weight and reduced bacterial diversity in Ixodes ricinus ticks compared to those that fed on mice immunized against Leuconostoc mesenteroides, a non-keystone taxon or mock-immunized group. The abundance of Escherichia-Shigella, but not Leuconostoc was significantly reduced in ticks fed on E. coli-immunized mice and this reduction was correlated with a significant increase in host antibodies (Abs) of the isotype IgM and IgG specific to E. coli proteins. This negative correlation was not observed between the abundance of Leuconostoc in ticks and anti-L. mesenteroides Abs in mice. We also demonstrated by co-occurrence network analysis, that immunization against the keystone bacterium restructure the hierarchy of the microbial community in ticks and that anti-tick microbiota vaccines reduced the resistance of networks to directed removal of taxa. Functional pathways analysis showed that immunization with a live bacterial vaccine can also induce taxon-specific changes in the abundance of pathways. Our results demonstrated that anti-tick microbiota vaccines can modulate the tick microbiome and that the modification is specific to the taxon chosen for host immunization. These results guide interventions for the control of tick infestations and pathogen infection/transmission.

immunology↗

bioRxiv2021

Complex landscapes partially mitigate negative pesticide effects on tropical pollinator communities

Land-use change and pesticides have been identified as two of the main causes behind pollinator decline. Understanding how these factors affect crop pollinator communities is crucial to inform practices that generate optimal pollination and ensure sustainable food production. In this study, we investigated the effects of landscape composition and pesticide residues on bee communities and their pollination services in Solanum quitoense "lulo" crops in Colombia. On 10 farms, located along a gradient of landscape complexity that varied from 0.15 to 0.62 in their natural habitat proportion, we characterized the bee community visiting the crop, and carried out pollination experiments with bagged and open inflorescences to later estimate fruit set, weight, and diameter at every site. Additionally, we performed pesticide analysis on collected anthers through liquid chromatography to estimate pesticide risk coming from the crop fields using hazard quotients (HQ). Bee abundance and species richness decreased with increased HQ, but these negative pesticide effects were less detrimental in farms with higher natural habitat proportions. However, this buffer effect was lost at sites with very high HQs. Imidacloprid was frequently found in the anthers and there were extremely high concentrations in some farms (0.6 to 13063 g/kg), representing the molecule of greater risk for bees in this context. Pollinators importance to crop yield was demonstrated in the exclusion experiments, where we found a reduction in fruit set (51%), weight (39%), and diameter (25%). We found a significant effect of bee richness on fruit set, while landscape composition and HQ had no significant effect on fruit set, suggesting that the last two factors do not affect yield directly, but indirectly through a decrease in pollinator diversity. Our results provide novel evidence that the natural habitat loss due to the expansion of pastures for cattle ranching and pesticide residues in anthers reduce bee diversity and abundance in this Andean cropping system, but strategies to protect and restore natural habitat can help to buffer, until certain levels, these negative effects. Highlights- We explored how landscape composition and pesticide residues impact bee communities and pollination services in Solanum quitoense crops. - As the proportion of natural habitat in the landscape increased, bee richness also increased. While as pesticide hazard quotients in S. quitoense anthers increased, bee diversity and abundance decreased. - The natural habitat surrounding farms mitigates the negative pesticide effects on bees when hazard quotients are low/medium, but not when they are high. - S. quitoense crops are highly dependent on bees for optimum yield.

ecology↗