Biology subjects

Pinkert, S.

Publications and source records attributed to Pinkert, S..

5 recordsLinked to original sources

bioRxiv2026

Introducing entropy-based metrics for quantifying edge- and macro-shape complexity in leaves and beyond

Leaf shape is a fundamental trait of plant ecological strategies, influencing biotic interactions and ecosystem functioning. However, established quantitative metrics fail to capture subtle variations and irregularities, require user-based reference points or are challenging to compare among taxa with broadly different leaf shapes. In addition, established metrics typically conflate (aggregate) leaf edge complexity and macro-shape complexity, despite their independent functional significance and genetic foundations. Here, we introduce an entropy-based framework to quantify two new complexity metrics: edge complexity and macro-shape complexity. Based on three case studies, we show that these metrics outperform aggregate metrics in predicting Quercus robur chemical traits, provide more intuitive interspecific classifications, and strongly align with human perception. In addition, edge and macro-shape complexity show high complementarity, while aggregate metrics are highly redundant and typically strongly related to leaf area. Emerging as the strongest predictor of leaf chemistry and key visual cue for complexity as perceived by humans, the effects of edge complexity highlight the under-appreciated functional significance of leaf margins. Our framework and the proposed entropy-based complexity metrics thus promise to help unlock the potential of growing digital image archives of leaves, including images from herbaria and fossils, and are technically readily applicable to shapes of algae, bacteria, pollen, and beyond. The accompanying package ShapeComplexity enables the broad application of entropy-based metrics, providing a powerful tool to explore how the shape of organisms and biological structures influences ecological strategies, biotic interactions, and ecosystem functioning while tracking spatial and temporal variation.

ecology↗

bioRxiv2026

Intra-individual variation in leaf microbiota matches within-crown environmental heterogeneity and promotes tree performance

Plant-associated microbial communities exhibit pronounced specificity across biological and spatial scales. While the patterns and accompanied functions have been well documented across and within plant species, the functional importance of intra-individual variation remains underexplored. Particularly in trees that experience strong environmental gradients within single crowns, stratum-specific microbiota may significantly contribute to plant performance. We experimentally tested whether variation in microbiota within the crown of Quercus robur is related to host performance. In mesocosm experiments, we transferred microbial communities derived from sun and shade leaves to germ-reduced clonal individuals of the same species and applied UV radiation simulating conditions that matched or mismatched the origin of the microbial inoculum (environmental matching). Our results demonstrate that matching microbiota-environment combinations increased plant performance compared to mismatching combinations. We infer that pronounced intra-individual variation of leaf-associated microbial communities not only reflects environmental heterogeneity along canopy strata but is functionally relevant for the plant host.

ecology↗

bioRxiv2026

Small stream restoration increases habitat and plant diversity across scales

A majority of stream restoration efforts in central Europe focus on streams that are less than five meters wide. Restoration aims to increase structural complexity, thereby enhancing habitat heterogeneity, promoting biodiversity, and reestablishing aquatic-terrestrial linkages that can drive responses in adjacent terrestrial communities. However, the effects of small stream restoration on terrestrial biodiversity remain poorly understood because research focuses mainly on large rivers. Here, we investigated the effects of restoration on the structural complexity of the stream channel as well as the terrestrial habitat and plant diversity on a local and landscape scale across 55 small streams in an agricultural landscape. We compared restored stream sections with non-restored ones that were similar to the conditions before restoration. We also assessed how restored sections changed over time since restoration. Restored stream sections showed a higher stream structural complexity and habitat diversity, both of which are targets of active restoration measures. Restoration also increased riparian plant diversity, both directly and indirectly through structural complexity and habitat diversity. Although time since restoration did not influence structural complexity, it drove successional changes in plant communities that became increasingly associated with wetland habitat conditions. Our results demonstrate that small stream restoration effectively increases floodplain habitat and plant diversity in agricultural landscapes, primarily by enhancing water availability in the floodplain. Restoration actions on small streams support biodiversity if they improve stream channel complexity, connect the stream with its floodplain, and create floodplain habitats.

ecology↗

bioRxiv2026

Size- and colour-based mechanisms shape the phenological structure of butterfly communities

O_LISeasonal patterns of species appearances constitute a major component of diversity variation. Theory attributes this phenological structuring of communities to the alignment of life cycles to suitable moments and to constraints of seasonality on development, yet the specific mechanisms operating across taxa remain largely unresolved. In insects, body size and colour are key functional traits that contribute to driving spatial community assembly through their link to thermoregulatory performance and development. C_LIO_LIHere we analyse variation in mean body size and colour lightness of 483 butterfly assemblages across Great Britain and throughout the season to test whether trait alignment with seasonal environment and developmental constraints may shape the phenological structuring of communities. C_LIO_LIBoth body size and body colour varied more along season than across space, emphasizing the importance of phenology on diversity variation. Body size was larger early and late in the season, i.e. under conditions of low temperature and solar radiation. This pattern contrasted with the spatial trends found and was driven by species overwintering as adults, which we interpret as being likely due to energetic constraints. Body colour, conversely, was darker early and late in the season, mirroring the spatial pattern found, and suggesting a thermoregulatory alignment with seasonal conditions. Furthermore, covariation between body size and colour suggests a thermoregulatory interaction between both traits. C_LIO_LIOur findings suggest that life-cycle constraints and seasonal thermoregulatory alignment contribute to shaping the phenological structure of insect communities. C_LI

ecology↗

bioRxiv2025

Metabolic ecology and habitat stability explain the disproportionately high species richness in standing waters

The Metabolic Theory of Ecology (MTE) conceptualizes that temperature is the primary driver of species richness, a pattern well supported in terrestrial taxa but less certain for freshwater organisms. Limited global-scale evidence and frequent violations of MTEs assumptions, particularly the stationarity of body size and abundance, further obscure its applicability. In freshwater systems, body size and abundance are tightly linked to dispersal and range size, which differ markedly between running-water (lotic) and standing-water (lentic) species, as proposed by the Habitat-Stability-Dispersal Hypothesis (HSDH). Adaptations to habitat stability may therefore generate distinct biogeographical trait patterns and modify richness-temperature relationships predicted by MTE. Utilizing comprehensive global functional, phylogenetic, and distributional data on dragonfly and damselfly species (83%) and habitat information (46%), we tested MTE predictions for lentic versus lotic species. Lotic species richness followed MTE expectations (slope: -0.469) more closely than lentic species richness (slope: -0.283). The proportion of lentic species in an assemblage was the strongest predictor of deviation in the species richness-temperature relationship (R2 = 38%). Assemblages dominated by lentic species clustered in climatically unstable regions and mainly including smaller-bodied species with larger ranges. Phylogenetic comparative analysis shows a strong phylogenetic signal in habitat preference, with the most species rich and northernly distributed families comprising predominately lentic species. Our findings suggest that adaptations to habitat stability facilitated the colonization and persistence of lentic species in harsh and fluctuating climates both past and present causing largely divergent species richness patterns of lentic and lotic odonates. Integrating HSDH-related traits (body and range size) not only substantially improves the explanatory power of the MTE, but also reveals a trait syndrome with broad implications for the biogeography and climate change responses of freshwater communities.

ecology↗