Simbiosi tra animali: osservazioni e inferenza sui processi

Responsabili di progetto

Diego Fontaneto, Viatcheslav Ivanenko

Accordo

RUSSIA - RFBR-suspended - Russian Foundation for Basic Research

Bando

CNR/RFBR 2015-2017

Dipartimento

Scienze del sistema terra e tecnologie per l'ambiente

Area tematica

Scienze del sistema Terra e tecnologie per l'ambiente

Stato del progetto

Nuovo

Proposta di ricerca

We aim at understanding the processes driving, generating and maintaining one of the most intriguing relationships in the animal kingdom: the symbiosis between animals of different groups. We will explore the generalities of the process by targeting two completely different model systems, in which we will target repeated test cases in different habitats and in different geographic areas.
The two focal groups will be: one in which symbiotic relationships with other animals are common, the Crustacea Copepoda, and one in which the symbiotic relationships with other animals are rare, the Rotifera Bdelloidea. Symbiotic copepod crustaceans are an abundant and poorly investigated ecological group of Cyclopoida, Harpacticoida, Monstrilloida, Poecilostomatoida, and Siphonostomatoida. Copepods of these orders are found in symbiosis with representatives of most taxa of invertebrates inhabiting shallow and deep-water communities, both in freshwater and in the marine habitats, e.g. sponges, cnidarians, and echinoderms. Symbiotic bdelloid rotifers are rare both in freshwater and in the sea, and are found on hosts such as crustaceans, echinoderms, and annelids. By comparing the evolutionary trajectories in the symbiotic relationships in two groups (copepods and bdelloids), in which the symbioses are fundamentally different, we will be able to support the strength of the generalities that will be found in common between them.
The main approaches that we will follow to answer our question are: (1) field trips to obtain samples of different hosts and symbionts; (2) DNA amplification of target regions from hosts and symbionts to infer the co-evolutionary relationships; (3) statistical modelling to infer the mechanisms of the origin and maintenance of symbiosis.
(1) Field trips and samples
We will visit two different areas in Russia (Lake Baikal and Japan Sea) and two different areas in Italy (Lake Maggiore and Sardinia): all four areas are known to host several examples of symbionts on both groups. The areas also represent well studied marine and freshwater sites, for which several additional information on animal communities and environmental parameters are easy to obtain. Samples will be collected, sorted, isolated, and preserved directly on site, given the availability of reliable laboratory facilities nearby.
(2) Co-evolutionary relationships
We will extract DNA from both hosts and symbionts, amplify a set of commonly used molecular markers (e.g. COI, ITS1, 28S, 18S, etc.); produce phylogenetic reconstructions with Maximum Likelihood and Bayesian Inference (e.g. with RAxML and BEAST); assess species limits with different methods from DNA taxonomy (e.g. ABGD, GMYC, BP&P, etc.); infer the strength and the shape of the co-evolutionary relationships between hosts and symbionts, separately for copepod crustaceans and bdelloid rotifers. In order to provide a larger phylogenetic background, we will include in our phylogenetic reconstructions all the genetic information available on online repositories (e.g. GenBank) for closely related species of all groups.
(3) Inference on the origin of symbiosis
We will use statistical tools to compare the parameters from the shape of the co-evolutionary relationships. We can forecast the use of two sets of statistical tools: (i) generalised linear mixed effect models or other extensions of linear models to account for potential confounding factors in the analysed drivers included in the analyses; (ii) comparative phylogenetic analyses to incorporate the shape of the phylogenies in our inference on the parameters. We will use mostly R as a statistical platform, with specific packages devoted to mixed effect models (e.g. lme4) and comparative phylogenetic analyses (e.g. caper).
We predict that the outcome of the project will be published in several papers dealing with different approaches. The most important one will be also the one with the broadest view on the co-evolutionary relationships; several additional papers will focus on more detailed questions and analyses, such as: species delimitation from DNA taxonomy in specific groups; local species lists with description of new species for science; phylogenetic reconstructions for several groups; eco-evolutionary inference on specific groups with peculiar features; etc.

Obiettivi della ricerca

Understanding the generality of the processes that drive the occurrence of diversification in nature is a pivotal question in evolutionary ecology and biodiversity studies. Biological diversity is at risk in our changing environment and we should understand the basic processes of it, before it is too late and useful model systems will disappear. By focusing on a specific case of diversification and potential co-evolution (symbiosis), studied with two radically different model systems, one in which symbiosis is common (copepod crustaceans) and one in which it is rare (bdelloid rotifers), we will understand the generality of the processes driving and maintaining symbiosis as a peculiar example of diversification.
The two proponents are among the most important scientists working on the two groups of animals (copepods for the Russian partner and rotifers for the Italian partner) and have complementary skills and approaches in the way they analyse scientific questions and arguments. Thus, an additional aim is to gain new insights and new knowledge from this collaboration. The two partners have already worked together, but only superficially in previous projects on marine diversity and in teaching in international schools. This project will further strengthen and consolidate the interaction.

Ultimo aggiornamento: 25/04/2024