Biology subjects

Medina, N.

Publications and source records attributed to Medina, N..

7 recordsLinked to original sources

bioRxiv2026

Diversifying stocking practices within rangelands supports diverse plant-pollinator communities and interactions

Understanding how management alters species' biodiversity and interactions is critical for sustainable agriculture. This can be especially important for rangelands, grasslands used for livestock grazing that cover 30% of land worldwide. In rangelands, ranchers need to maximize livestock production while supporting healthy ecosystems. Grazing management can alter the impact of livestock by varying grazing timing and intensity, but its ecological impacts remain poorly understood. One critical function that may be supported in these systems is pollination; how rangeland management may alter this ecosystem service is not systematically understood. We investigated how rotational stocking, where livestock are rotated among pastures, affected plant and pollinator communities and plant-pollinator interactions using working ranches in the Southern Great Plains. Sites were managed through continuous stocking or rotation with low or high frequency. We found that high-frequency livestock rotation supported greater flower abundance, and consequently greater pollinator abundance. Pollinator orders varied in their responses to management with Hymenoptera directly responding to management, and Coleoptera and Lepidoptera responding indirectly via changes in flower abundance. Community-level changes produced more specialized interaction networks and higher interaction diversity. These community changes, and resulting species turnover, led to high interaction turnover across rangeland sites. This suggests that a mosaic of management strategies likely diversifies habitat and helps support plant and pollinator biodiversity at the landscape scale. This study demonstrates that rangelands can support plants, pollinators, and their interactions, particularly when managed with high-frequency rotational stocking.

ecology↗

bioRxiv2025

Temporal dynamics of ectomycorrhizal fungi: Leaf habit and exploration strategy explain seasonal variation in community abundance and composition

Ectomycorrhizal (EcM) fungi are well-recognized symbionts impacting tree health and ecosystem functioning globally, yet understanding of their timing of proliferation in soils across seasons and years remains limited. We analyzed monthly patterns of EcM fungal abundance and community structure over two years in five temperate monodominant forest plots via quantitative PCR and Illumina sequencing. We found that the phenological dynamics of EcM fungi differed significantly by host tree leaf habit, fungal exploration type, fungal genus, and soil moisture. Overall, total EcM fungal abundances based on qPCR consistently peaked in autumn, and were more dynamic in evergreen than deciduous plots, supporting ideas of surplus carbon and asymmetric above-belowground dynamics. Longer-distance exploration types peaked earlier and were more stable than shorter-distance types, suggesting an independent and supportive role in releasing spring nutrients. About half of 20 focal taxa consistently peaked in either autumn, summer, or spring, while others were either host- and/or year-dependent. Our findings highlight that phenology is a key EcM fungal trait best explained by both host and fungal contributions, and future studies across biomes should consider seasonal shifts and sampling to elucidate phenological traits. Summary- The timing of belowground production and seasonal community dynamics remain poorly understood for ectomycorrhizal (EcM) fungi. - We collected soils monthly for two years from five temperate monodominant forest plots. - Fungal production peaked in autumn, shorter-distance and evergreen-associated spanned wider ranges, and half of focal fungal genera showed seasonal preference, emphasizing autumn surplus carbon and spring nutrients from long-distance types. - Future studies should consider seasonal shifts when sampling EcM fungal communities, and forest carbon models should include asymmetric above-belowground phenology. Translated Summary (Spanish)- La fenologia de la produccion y composicion de comunidades de hongos ectomicorrizicos (EcM) es poco estudiada. - Recolectamos suelos mensualmente por dos anos de cinco parcelas mono-dominantes templados. - Produccion maxima de hongos ocurrio en otono, hongos asociados con arboles siempreverdes y de exploracion de corta-distancia observaron rangos mas amplios, y la mitad de generos de hongos focales observaron preferencia estacional, enfatizando extra carbono en otono y nutrientes en primavera de tipos larga-distancia. - Estudios deben considerar cambios estacionales para el muestreo de hongos EcM, y modelos de carbono deben incluir fenologia asimetrica entre hojas y hongos. Plain language summaryEctomycorrhizal fungi are critical for the global carbon cycle, but their seasonal and inter-annual growth patterns remain unclear. We sample soil DNA monthly over two years across five different monodominant temperate forest stands. We find an overall belowground peak in autumn, with significantly later growth under wetter conditions, more dynamism with evergreen trees, and distinct spring growth by longer-distance fungi.

ecology↗

bioRxiv2024

Bursts from the past: Intrinsic properties link a network model to zebra finch song

Neuronal intrinsic excitability is a mechanism implicated in learning and memory that is distinct from synaptic plasticity. Prior work in songbirds established that intrinsic properties (IPs) of premotor basal-ganglia-projecting neurons (HVCX) relate to learned song. Here we find that temporal song structure is related to specific HVCX IPs: HVCX from birds who sang longer songs including longer invariant vocalizations (harmonic stacks) had IPs that reflected increased post-inhibitory rebound. This suggests a rebound excitation mechanism underlying the ability of HVCX neurons to integrate over long periods of time throughout the song and represent sequence information. To explore this, we constructed a network model of realistic neurons showing how in-vivo HVC bursting properties link rebound excitation to network structure and behavior. These results demonstrate an explicit link between neuronal IPs and learned behavior. We propose that sequential behaviors exhibiting temporal regularity require IPs to be included in realistic network-level descriptions.

neuroscience↗

bioRxiv2023

Above- and below-ground links mediated by arboreal ants and host tree modify soil aggregation scaling, infiltration, and chemistry

Soils are increasingly recognized as complex systems, emphasizing a need to study unique properties such as long-tailed scaling laws and the role of indirect interactions among arboreal above- and below-ground soil invertebrates. However, few studies consider the above-below-ground connections mediated by invertebrates activity and behavior compared to mediated by tree physiology. Given previous work showing that arboreal ants can compete and affect ground foragers as well as alter foraging behavior on different host trees, it is plausible that persistent above-ground ant nesting could extend to affect soil properties including structure and chemistry, mediated by ground ant exclusion. This study analyzes soil aggregation, water infiltration, and macro-chemical data associated with longer-term (5+ year) ant nesting in a rustic tropical agroforest. Results show that, 1) ant nesting maintained scaling law exponents or fractal dimensions of soil aggregate size distributions, and was significantly associated with relatively larger micro-aggregate diameters and log-normal variance in macro-aggregate size distributions, suggesting more consistent (less variable) underlying aggregation processes similar to host tree species effects; 2) areas in the vicinity of trees with no dominant ant nests had three-times faster water infiltration than in the vicinity of trees with dominant ant nests; and 3) a tendency toward changes in soil carbon and nitrogen stocks by one-quarter depending on host tree. These patterns are consistent with expected effects of ground ant suppression by an aggressive keystone arboreal ant, and are supported by previous studies reporting positive ground ant nest effects on soil chemistry and documenting ground ant foraging as a source of soil aggregate fragmentation. This study presents new ecological processes affecting ecosystem-scale functions, and suggests that future research on indirect interaction cascades would be beneficial to advance fundamental understanding of whole-ecosystem processes.

ecology↗

bioRxiv2023

Comparative analysis of myoglobin in Cetaceans and humans reveals novel regulatory elements and evolutionary flexibility

Cetacea and other diving mammals have undergone numerous adaptations to their aquatic environment, among them high levels of the oxygen-carrying intracellular hemoprotein myoglobin in skeletal muscles, especially those responsible for swimming. Hypotheses regarding the mechanisms leading to these high myoglobin levels often invoke exercise, hypoxia, and other physiological pathways that impact gene regulation, and increase myoglobin gene expression. Here we explore an alternative hypothesis: that Cetacean myoglobin genes have evolved high levels of transcription driven by the intrinsic developmental mechanisms that drive muscle cell differentiation. We have used luciferase assays in differentiated C2C12 cells to test this hypothesis. Contrary to our hypothesis, we find that the myoglobin gene from the minke whale, Balaenoptera acutorostrata, has a low level of expression, less than 10% that of humans. This low expression level is broadly shared among Cetaceans, and Artiodactylans. Previous work on regulation of the human gene has identified a core muscle-specific enhancer comprised of two regions, the "AT element" and a C-rich sequence 5 of the AT element termed the "CCAC-box". Comparative analysis of the minke whale gene supports the importance of the AT element, but the minke whale CCAC-box ortholog has little effect. Instead, critical positive input has been identified in a G-rich region 3 of the AT element. Also, a conserved E-box in exon 1 positively affects expression, despite having been assigned a repressive role in the human gene. Last, a novel region 5 of the core enhancer has been identified, which we hypothesize may function as a boundary element. These results illustrate regulatory flexibility during evolution. They also support the hypothesis that the induction of transcription by physiological signaling pathways, and evolved protein stability are important in leading to the high myoglobin protein levels found in Cetaceans.

molecular biology↗

bioRxiv2022

Habitat edges affect tree diversity more than biomass regeneration in a reforested wet neotropical timber plantation

About half of all forests are tropical and secondary, making tropical forest regeneration integral to future forests. Tree stand biomass and taxonomic richness can recover in a few decades, but relative abundances may lag indefinitely. Since most forests are within a km of a habitat edge, edge effects likely affect community composition regeneration. However, most studies assess how degraded edges affect intact forests, leaving it unclear whether higher-quality edges could facilitate regeneration of nearby degraded forests. Notably, higher quality edges near intact forests could promote processes like dispersal and wood biomass accumulation that effectively accelerate succession, leading to better performance of shade-tolerant taxa compared to pioneer taxa in the early stages of forested plantation regeneration. This study addressed how wet tropical forested plantation regeneration was affected by distance to adjacent intact forest edge. It was hypothesized that old timber plantations facilitate regeneration by increasing available shade, favoring the presence and biomass of later-successional taxa, ultimately changing community composition overall. A wet neotropical timber plantation reforested after 20 years and adjacent to primary forest was censused for trees along a 300 m edge distance gradient, and analysis matched identified taxa to broad dispersal mode and wood density traits using relevant literature. As distance from primary forest edge increased, stem and wood density tended to increase significantly, with ~10% variation explained, while biomass and canopy light surprisingly tended to stay the same. Stand tree richness also tended to increase significantly, but diversity decreased steeply and non-linearly, explained in part by wood density, and taxonomic composition varied notably. Finally, tree taxa associated with both early and late successional stages decreased significantly, as well as genus Ficus, but biomass by dispersal mode did not tend to change. Overall this study supports that stand composition is less resilient and more subject to edge effects than biomass and richness, suggesting that global forests will likely be distinctly new assemblages in the future, with timber and biodiversity trade-offs occurring based on local and regional management activity.

ecology↗

bioRxiv2018

From Metapopulation to Metacommunity and the Complications of Community Structure

The metacommunity, as it evolved from Levins metapopulation, provides a framework to consider the spatial organization of species interactions. Arguably the most fundamental feature of metapopu-lations and metacommunities are that demes are connected via migration. An important result from Levins metapopulation work--that increasing migration lowers regional extinction probability--is often incorporated into conceptions of metacommunities. We first use a toy model to show how this result from Levins metapopulation does not necessarily hold when considering community interactions in a metacommunity context. We also report results from a metacommunity field experiment conducted with a tropical terrestrial leaf litter community and show that migration induces the extinction of predators in the metacommunity. Our result corroborates the findings of a prior metacommunity experiment in a temperate terrestrial leaf litter community. The concordance between these experiments even with vastly different communities highlights the importance of considering trophic and non-trophic community structure to understand metacommunity dynamics.

ecology↗