Gilbert, J. D. J. | bioRxiv Science

bioRxiv2025

Multi-tool monitoring: integrating non-invasive methods to assess vertebrate diversity and trophic complexity in terrestrial rewilding

O_LIRewilding, the restoration of natural processes to create self-sustaining and resilient ecosystems, is an increasingly popular conservation approach. However, outcomes are often unpredictable, and effective ecological monitoring is critical for understanding impacts. Integrating environmental DNA (eDNA) metabarcoding with other non-invasive tools may help provide more comprehensive assessments of taxonomic and functional diversity and trophic complexity. C_LIO_LIWe applied an integrated monitoring approach at a rewilding site in Scotland, comparing vertebrate diversity detected by metabarcoding four eDNA sample types (water, soil, tree rolling, scat) with passive acoustic monitoring (PAM) and camera trapping. Each method was evaluated for taxonomic richness, community composition, functional diversity using trait-based analyses, and trophic complexity through co-occurrence networks. The comparative effectiveness of these methods is rarely explored beyond basic taxonomic diversity metrics. C_LIO_LIIn total, 79 vertebrate taxa were detected: PAM captured 52 taxa, eDNA 44, and camera traps 17. Of the eDNA substrates, water and tree-rolling samples had the highest richness. Each method detected unique species, with birds and bats best covered by PAM, and small mammals by eDNA. Community composition varied between methods, with eDNA substrates capturing broader communities. PAM revealed the most pronounced community differences between wooded and open habitats. C_LIO_LITree rolling and water eDNA captured the greatest functional diversity, while PAM showed higher redundancy, detecting species with similar ecological roles. No single method captured all functional traits. Integrating eDNA methods with PAM produced the most complete trophic network. PAM provided the most complete network but missed key terrestrial interactions that were filled by eDNA. C_LIO_LISynthesis and applications: Our findings highlight the necessity of an integrated multi-method toolkit for practitioners to comprehensively capture vertebrate richness, functional diversity, and trophic complexity, particularly in rewilding contexts. We recommend combining PAM with either tree rolling or water eDNA sampling as an optimal monitoring strategy, balancing their complementary strengths in taxonomic and functional coverage. C_LI

ecology↗

bioRxiv2018

The geometry of dependence: solitary bee larvae prioritize carbohydrate over protein in parentally provided pollen

O_LIMost organisms must regulate their nutritional intake in an environment full of complex food choices. While this process is well understood for self-sufficient organisms, dependent offspring, such as bee larvae, in practice have limited food choices because food is provided by parents. Nutrient balancing may therefore be achieved by offspring, by parents on offsprings behalf, or by both, whether cooperatively or in conflict. C_LIO_LIWe used the Geometric Framework to investigate the capacity of dependent larval mason bees (Osmia bicornis) to regulate their intake of protein and carbohydrate. Female Osmia seal eggs individually inside cells they have provisioned with pollen, and have no contact with developing offspring, allowing offspring choices to be studied in isolation. Herbivorous insect larvae are typically expected to balance protein and carbohydrate to maximise growth and reproduction. C_LIO_LIContrary to prediction, carbohydrate and not protein mediated both growth and survival to pupation. Accordingly, larvae prioritised maintaining a constant intake of carbohydrate and self-selected a relatively carbohydrate biased diet compared to other hymenopterans, while tolerating wide excesses and deficiencies of protein, rendering them potentially vulnerable to dietary change or manipulation. Reasons for prioritising carbohydrate may include (1) the relative abundance of protein in their normal pollen diet, (2) the relative paucity of nectar in parental provisions making carbohydrate a scarce resource, or (3) the requirement for diapause for all O. bicornis larvae. Larvae were intolerant of moderate dietary dilution, likely reflecting an evolutionary history of nutrient-dense food. C_LIO_LIOur results demonstrate that dependent offspring can remain active participants in balancing their own nutrients even when sedentary, and, moreover, even in mass provisioning systems where parents and offspring have no physical contact. Research should now focus on whether and how evolutionary interests of parent and dependent offspring coincide or conflict with respect to food composition, and the implications for species resilience to changing environments. C_LI

animal behavior and cognition↗