Hereu, B. | Search bioRxiv

bioRxiv2025

Unravelling hidden trophic interactions among sea urchin juveniles and macroinvertebrates by DNA amplification

Rocky reefs may shift between two distinct stable states: productive algal forests, characterized by high abundance and biodiversity of macrofauna, and impoverished barrens, dominated by overgrazing sea urchins. Barren states may persist despite the recovery of adult sea urchin predators, suggesting additional stabilizing mechanisms. Sea urchin settlers rapidly disappear in forests, but they persist in barrens, suggesting that post-settlement predation might play a crucial role in determining sea urchin population density. Visual assessment of predation events in the field is unfeasible due to the microscopic scale of both predators and preys and the complexity of the arena. In this study, we designed and tested specific primers for the detection of mtDNA of settlers of the Mediterranean sympatric sea urchin species Paracentrotus lividus and Arbacia lixula on degraded samples. By testing 360 invertebrates collected in algal forests during an urchin settling event at five mtDNA loci, we identified 60 (17%) samples positive to P. lividus DNA. Presence of urchin DNA was confirmed by sequencing and NGS metabarcoding analyses. Our results suggest that micropredation may represent an important process in controlling sea urchin population density and maintaining the forest state in temperate rocky reefs. StatementsThe data that supports the main findings of this study are available in the supplementary material of this article. Other data are available from the corresponding author upon reasonable request.

ecology↗

bioRxiv2019

Aquatic and terrestrial organisms display contrasting life history strategies as a result of environmental adaptations

AimsAquatic and terrestrial realms display stark differences in key environmental factors and phylogenetic composition. Despite such differences, their consequences for the evolution of species life history strategies remain poorly understood. Here, we examine whether and how life history strategies vary between terrestrial and aquatic species.\n\nLocationGlobal.\n\nTime periodVariable, the earliest year being in 1906 and the most recent in 2015.\n\nMajor taxa studiesMacroscopic animals and plants species.\n\nMethodsWe use demographic information for 638 terrestrial and 117 aquatic animal and plant species, to derive key life history traits capturing their population turnover, and investments in survival, development, and reproduction. We use phylogenetically corrected least squares regression to explore the differences in the trade-offs between life history traits in both realms. We then quantify the life history strategies of aquatic and terrestrial species using a phylogenetically corrected principal component analysis.\n\nResultsWe find that the same trade-offs structure terrestrial and aquatic life histories, resulting in two dominant axes of variation describing species pace- of-life and reproductive spread through time. Life history strategies differ between aquatic and terrestrial environments, with phylogenetic relationships playing a minor role. We show that adaptations of plants and animals to terrestrial environments have resulted in different life history strategies, particularly with their reproductive mode and longevity. Terrestrial plants display a great diversity of life history strategies, including the species with the longest lifespans. Aquatic animals, on the contrary, exhibit higher reproductive frequency than terrestrial animals, likely due to reproductive adaptations (i.e. internal fecundation) of the later to land.\n\nMain conclusionsOur findings show that aquatic and terrestrial species are ruled by the same life history principles, but have evolved different strategies due to distinct selection pressures. Such contrasting life history strategies have important consequences for the conservation and management of aquatic and terrestrial species.

ecology↗