Biology subjects

Ruka, A. T.

Publications and source records attributed to Ruka, A. T..

3 recordsLinked to original sources

bioRxiv2026

Holobiomes in succession: post-glacial microbial communities are structured by hosts, time and habitat heterogeneity

O_LIGlacier forefields in the high-desert region of Ladakh (northwestern Himalaya) are colonized by a variety of interdependent organisms, including lichens, prokaryotes, fungi, mosses, and vascular plants, along a successional gradient. Together with bulk soil, these hosts and their associated microorganisms form a broader microbial metacommunity (holobiome) whose structure, interactions and functions remain poorly underexplored in one of the Earths most extreme and climate-sensitive environments. C_LIO_LIUsing a multidisciplinary approach combining glacial chronosequence transects, GIS-derived topographic variables, soil properties, and plot cover measurements, we assessed the abiotic and biotic factors influencing bacterial and fungal communities sequenced from different hosts and bulk soil (hereafter sources). Microbial composition was primarily shaped by source identity, though certain sources, such as biological soil crusts (BSCs), mosses, and plant rhizospheres, also showed relationships with moraine age in either bacterial or fungal communities. C_LIO_LIBacterial and fungal community congruence was tested using Procrustes analyses, revealing that mosses maintained tightly coupled inter-kingdom relationships throughout the glacier forefields. However, the degree of congruence in plant rhizospheres and bulk soils was influenced by topographic variation and moraine age, respectively. C_LIO_LICo-occurrence network analyses revealed that early successional microbial communities were assembled more stochastically, with bacteria being more interconnected than fungi. In contrast, late successional stages were more compartmentalized, being more structurally stabile, likely driven by increased plant cover and functional redundancy among microbial taxa. C_LIO_LIKeystone bacterial and fungal taxa were identified in plant rhizospheres and bulk soil using a dual-criteria approach related to inter-kingdom congruence and network node eigenvalues. Furthermore, some of these taxa were associated with environmental factors, suggesting topographic heterogeneity and successional age can promote or deter the influence of keystone taxa. C_LIO_LISynthesis: This study reveals the impact of both macroorganism colonization (i.e. plants, mosses, and lichens) and microcommunity establishment (BSCs and bulk soil), as abiotic and biotic sources, on microbial metacommunity assembly in glacier forefields. By adopting a broader approach across different spatial scales, we demonstrate that while plant colonization plays a central role in shaping microbial metacommunities, its effects are modulated by topographic variation along the chronosequence. C_LI

microbiology↗

bioRxiv2025

Elevational Shifts in Tropical Tree Leaf Traits: Interactions Between Soil, Climate, Light, and Phylogeny

Understanding how tropical trees respond to complex environmental gradients is essential for predicting forest resilience under climate change. We examined variation in key leaf traits, including specific leaf area (SLA), foliar nitrogen (N) and phosphorus (P), C:N and N:P ratios, and stable isotope composition ({delta}13C, {delta}15N), in 160 tree species along a 3,200-m elevational transect on Mount Cameroon. This gradient spans hyper-humid coastal rainforests to arid Afroalpine savannas, capturing sharp transitions in climate, soils, and forest structure. Leaf traits shifted nonlinearly with elevation, from acquisitive strategies at mid-elevations to conservative syndromes in lowlands and highlands. Mid-elevation forests ([~]1,000-1,500 m), characterized by moderate climate and canopy disturbance by elephants, supported nutrient-rich, high-SLA foliage. In contrast, high-elevation forests (>2,000 m) exhibited low SLA, high C:N, and enriched {delta}13C, consistent with stress tolerance under cold, dry, and fire-prone conditions. The strongest phosphorus limitation occurred in hyper-humid lowlands, where extreme rainfall (>12,000 mm/year) drives leaching losses. Foliar {delta}15N declined markedly with elevation (from +5{per thousand} to -5{per thousand}), indicating a shift from mineral N uptake and N-fixation in lowland Fabaceae to ecto- and ericoid mycorrhizal associations in montane Ericaceae. A bimodal {delta}15N pattern, with enrichment in both lowland and upper montane forests, reflects N-fixation under leaching and fire-driven N scarcity, respectively. Phylogenetic analyses showed that climate, soils, forest structure, and lineage jointly shaped trait-environment relationships. Traits related to {delta}13C, C:N, and {delta}15N exhibited strong phylogenetic signal, highlighting evolutionary constraints. These findings underscore the value of integrating functional traits, isotopes, and phylogeny to predict tropical forest responses to global change.

plant biology↗

bioRxiv2025

Year-round rhythms: alpine plant species modulate soil and microbial dynamics during the growing season and under the snow.

O_LISoil-plant-microbe interactions are integral throughout most terrestrial ecosystems, yet the importance of plant phenology and seasonal dynamism upon these relationships remains unknown. Given the pronounced seasonality of alpine environments, we sampled 8 plant species occurring in two habitats (alpine meadow and subnival zone) across four seasons (including snow-covered winter) in the Central Eastern Alps to determine the plant growth strategies and plant nutrient parameters which closely couple with rhizosphere microbial parameters. C_LIO_LIIn subnival locations, plants exhibited stronger seasonal changes among leaf and root tissue nutrient concentrations and non-structural carbohydrates (NSCs) compared to those in lower elevation alpine meadows. However, rhizosphere microbial parameters (microbial biomass (MBC), extracellular enzymes, and community composition) demonstrated more seasonal changes in the alpine meadow locations. C_LIO_LIA phenological delay was observed in bacterial and fungal communities of the subnival zone, with peak plant rhizosphere differentiation occurring later in the season than in alpine meadows. Therefore, the prolonged cold conditions and shorter growing season in higher elevations likely add a temporal aspect to the commonly used elevational gradient approach, which is not often considered. C_LIO_LIMBC and enzymatic potential within the rhizosphere were high across all plant species in the alpine meadow during the winter sampling, despite notable differences in microbial community composition. In contrast, winter rhizosphere communities did not differ between plant species in subnival locations, although one species, Oxyria digyna, demonstrated much higher microbial activity along with higher NSCs and root N, suggesting some alpine plant species may acquire nutrients through microbial interactions during snow-covered winter periods. C_LIO_LISynthesis: This study provides the first look at the annual phenology of multiple alpine plant species and their associated rhizosphere microbiome. Our results demonstrate that seasonal microbial dynamics are highly influenced by abiotic factors (soil and microclimatic conditions), but plants are able to modulate these conditions through growth and nutrient acquisition strategies. Taken together, seasonality and independent plant species effects cannot be overlooked when assessing habitat nutrient cycling and ecosystem stability. C_LI

microbiology↗