Biology subjects

Bracco, A.

Publications and source records attributed to Bracco, A..

4 recordsLinked to original sources

bioRxiv2026

Stepping-stone population structure and sidespread clonality of the mesophotic octocoral Swiftia exserta in the warm temperate northwest Atlantic

Isolated mesophotic banks form spatially discrete networks of patchy ecosystems along continental shelves. Their long-term persistence depends on connectivity among populations of the dominant coral species that structure these communities. Yet the scale of larval-mediated gene flow across these networks remains poorly characterized. Similarly, the extent to which clonal propagation shapes local population dynamics is unresolved, leaving the relative contributions of sexual and asexual reproduction to population maintenance an open question. Here, population genomics and high-resolution (1km) biophysical larval dispersal modeling are integrated to resolve the genetic connectivity and clonal dynamics of Swiftia exserta, a key habitat-forming octocoral, across 13 mesophotic banks spanning the U.S. Gulf and eastern coast within the Warm Temperate Northwest Atlantic (WTNWA) coastal and shelf biogeographic province. Genome-wide SNP markers derived from Restriction-site Associated Sequencing (RADseq) were genotyped across 288 individuals. About 40% of individuals belonged to clonal genets confined to single banks within meters of one another, indicating that asexual propagation sustains local density but plays no detectable role in inter-bank connectivity. Population genetic analyses pointed to isolation by distance as the primary structuring force, with the majority of molecular variance residing within rather than among populations. The west-most population, East Flower Garden Banks, was the most differentiated population in the WTNWA Northern Gulf ecoregion, reflecting its peripheral position within the bank network. The Edisto population from the WTNWA Carolinian ecoregion, was distinct from all others, implicating the Florida Peninsula as a phylogeographic barrier. Biophysical particle-tracking simulations independently recovered the same spatial structure, with modeled larval exchange consistent with the genomic signal across the bank network. These findings reveal that S. exserta persists across the northern WTNWA province through a dual reproductive strategy of clonality at the bank scale and episodic larval exchange at the network scale, with implications for the conservation and management of mesophotic octocoral metacommunities.

ecology↗

bioRxiv2026

Behavior-Driven Marine Larval Dispersal and Settlement with AI Agent-Based Modeling

Larval dispersal models are central to mapping and predicting ichthyoplankton dynamics in the ocean, yet despite decades of refinement they remain fundamentally limited by their ability to represent adaptive behaviors, relying instead on static trait parameterizations. This deficiency constrains our capacity to design effective restoration and mitigation strategies in an increasingly stressed ocean. SWARM (Simulating Waterborne Agent Routes for Marine connectivity) overcomes this barrier by integrating Large Language Model (LLM)-based behavioral agents with a standard biophysical model to simulate active decision-making during the pelagic larval stage. In both idealized and realistic conditions focusing on Red Snapper larvae in the Gulf of Mexico, agents develop adaptive behaviors that improve settlement and generate explainable vertical distribution patterns. SWARM demonstrates that LLMs can overcome long-standing limitations in dispersal modelling by explicitly representing behavioral drivers of movement, opening new pathways for predicting connectivity and designing effective marine-ecosystem restoration.

ecology↗

bioRxiv2025

Environmental filtering shapes patch dynamics across isolated mesophotic reefs

Mesophotic coral ecosystems (MCEs; [~]30-150 m) are major but poorly understood benthic habitats. We used Autonomous Reef Monitoring Structures (ARMS) and integrated metabarcoding (mtCOI, 18S), image analysis, and hydrodynamic modeling across six mesophotic banks in the Gulf of Mexico to test whether community assembly is governed by environmental filtering or dispersal limitation. Local environmental conditions explained nearly twice as much compositional variance as geographic effects. Differences in depth and turbidity predicted community dissimilarity up to tenfold better than geographic distance. Turbidity, driven by the benthic nepheloid layer (BNL), was the dominant filter, while depth effects were weaker and taxon-specific. Hydrodynamic simulations revealed dispersal is variable but not limiting. These findings identify the BNL as a key physical driver linking shelf oceanography, biodiversity, and ecosystem function. Suspended particle dynamics associated with BNLs merit integration into conservation planning as critical mediators of ecological connectivity in mesophotic and other patchy reef systems globally. TeaserSuspended particle layers, not dispersal barriers, determines which species colonize mesophotic coral reefs on the TX-LA continental shelf.

ecology↗

bioRxiv2021

Seascape genomics reveals metapopulation connectivity network of Paramuricea biscaya in the northern Gulf of Mexico

The degree of connectivity among populations influences their ability to respond to natural and anthropogenic stressors. In marine systems, determining the scale, rate, and directionality of larval dispersal is therefore central to understanding how coral metapopulations are interconnected and the degree of resiliency in the event of a localized disturbance. Understanding these source-sink dynamics is essential to guide restoration efforts and for the study of ecology and evolution in the ocean. The patterns and mechanisms of connectivity in the deep-sea (> 200 meters deep) are largely understudied. In this study, we investigated the spatial diversity patterns and metapopulation connectivity of the octocoral Paramuricea biscaya throughout the northern Gulf of Mexico (GoM). Paramuricea biscaya is one of the most abundant corals on the lower continental slope (between 1200 and 2500 m) in the GoM. The 2010 Deepwater Horizon oil spill (DWH) directly impacted populations of this species and thus are considered primary targets for restoration. We used a combination of seascape genomic analyses, high-resolution ocean circulation modeling, and larval dispersal simulations to quantify the degree of population structuring and connectivity among P. biscaya populations. Evidence supports the hypotheses that the genetic diversity of P. biscaya is predominantly structured by depth, and that larval dispersal among connected populations is asymmetric due to dominant ocean circulation patterns. Our results suggest that there are intermediate unsampled populations in the central GoM that serve as stepping stones for dispersal. The data suggest that the DeSoto Canyon area, and possibly the West Florida Escarpment, critically act as sources of larvae for areas impacted by the DWH oil spill in the Mississippi Canyon. This work illustrates that the management of deep-sea marine protected areas should incorporate knowledge of connectivity networks and depth-dependent processes throughout the water column.

ecology↗