My PhD was focused on Habitat Cascades (HCs), an unidirectional sequence of positive interactions where a species A provides habitat for a species B, which in turn provide habitat for a species C… and so on. Jointly with the direct interactions occurring (sp. A – sp. B – sp. C), indirect interactions (sp. A – sp. C) are also involved.
Habitat cascades are just a type of facilitation, where the main benefit of the interaction is specifically habitat formation or modification.
In the picture, I show a typical example of HC object of my research, specifically as part a project involving rocky shores canopy-forming seaweeds:
– seaweeds naturally support a very varied and plentiful community of invertebrates of different taxa providing shelter, refuge from predation, stress buffering, resources, etc.
– when a seaweed supports an epiphyte, providing additional settlement space, the chain increases its level and complexity and the invertebrates are additionally facilitated by the epiphyte.
As a result of these interactions, the total amount of invertebrates it is supposed to be higher than the simple summa of the amounts supported by each habitat former independently.
In my PhD I tested the core hypothesis that habitat cascades are key drivers in controlling and maintaining biodiversity in certain marine benthic ecosystems where epibiosis is prevalent.
I investigated, described and demonstrated the positive effects of these interactions in different ecosystems such as canopy-forming seaweeds, soft-bottom estuarines and seagrasses beds.
The methods included a combination of descriptive and experimental field and laboratory studies, morphological analysis, drone surveys and 3D modelling, supported by biostatistics via permutational-based factorial analysis of variance (PERMANOVA).
The final aim of my PhD was to create realistic conceptual, descriptive and predictive ecological models that can be tested and adapted in several habitats, ecosystems and biogeographical regions.
HABITAT CASCADE SYSTEMS
My PhD consisted of 6 projects investigating the role of habitat cascades in a perspective envisaging an increase in ecological complexity in terms of systems and species interactions, from simple low-diversity soft-bottom estuaries (Projects 1-2) to seagrass (Projects 3-4) and high-diversity rocky shores (Projects 5-6).
Each project consisted of:
(i) descriptive local and extensive spatio-temporal surveys: with deep focus on the effects of latitude and seasons, the surveys provided a general description of each habitat cascade system existing in each habitat and the factors affecting its strength;
(ii) general manipulative experiments: specifically testing the habitat cascades with a multifactorial approach, involving multiple levels of different biological and structural features of the actors (such as biomass, alive vs artificial condition, species, morphology);
(iii) specialized manipulative experiments: testing the mechanisms behind the habitat cascades;
(iv) morphological analysis: investigating a potential link between the structural complexity of each habitat former and the benefits able to provide.