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Phylogenetic Systematics and Evolution

Diversity and speciation of marine gastropods

The high diversity and recognition of congruent distributions of taxa in the Oceans have long puzzled researchers. Despite the growing body of knowledge many questions involving speciation and biogeography of marine invertebrates still lack a clear answer.

High dispersal potential conferred by long-lived pelagic larvae together with lack of obvious barriers to gene flow makes understanding speciation in the ocean particularly challenging. Marine speciation should be expected to be uncommon and slow, yet this is not the case and some groups particularly of tropical shallow-water gastropods are remarkably diverse.

It is widely recognised that molluscs provide excellent models to study evolutionary processes, since they are readily collected and often have an extensive fossil record. By looking into the systematics, geography, and phylogeny of several groups of gastropods we aim to unravel questions such as: Why is diversity higher in some geographical areas? Do tropical molluscs have higher rates of evolution? What was the impact of major vicariant Cenozoic tectonic events such as the closure of the Tethys Sea, uplift of the Isthmus of Panama, northwards drift of the Indian and Australia plates, etc., on the diversity, speciation and extinction of regional faunas? Is speciation achieved mainly sympatrically or allopatrically? What is the role of ecology on speciation? What is the time of origin of extant faunas? Did Plio-Pleistocene transient allopatry led to the formation of species?

To answer these questions molecular phylogenetic hypotheses are generated and correlated with the systematics of the group, tectonic events, past and present ocean-circulation patterns, ecology, and fossil record. The use of gastropod groups as a model requires first a well established systematic framework, ideally resulting from a combination of morphology, anatomy and DNA data.

At present systematics and evolutionary research is carried out on five worldwide genera of opisthobranchs gastropods: Aplysia, Bulla, Haminoea, Hypselodoris, and Scaphander.

 

Global systematic revision of the genus Aplysia: speciation and biogeography

Aplysia (sea-hares) are among the largest opisthobranch organisms with about 60 species worldwide. Morphological similarities lead to an extremely confused taxonomy. This project will revise the systematics of the genus based on anatomy, morphology of the internal shells, and molecular sequence data. A molecular phylogeny will be inferred and used to support species delineation and to understand speciation and biogeographical patterns.

 

Phylogeography of Bulla occidentalis in the tropical western Atlantic

The biogeography of the tropical western Atlantic, particularly the Caribbean Sea, is of great interest and fascinating complexity. The Pliocene closure of the Panamanian isthmus, the network of islands of different ages, coupled with Pleistocene transient allopatry caused by sea-level changes potentially generated a unique setting for recent biological diversification and extinction. A recent systematic review of the gastropod genus Bulla revealed that the western Atlantic species B. occidentalis is made up of at least three independent lineages. This project seeks the answers that may explain this phylogenetic pattern.

The systematics, biogeography and evolution of the genus Haminoea.

Haminoea are bubble-shell marine snails with an estimated 40 living species worldwide. This is the first attempt to incorporate all previously available and new data from shell structure, anatomy and molecular sequences in a systematic revision, phylogenetic and biogeographic analysis of the genus. The main objectives are to review and clarify the systematics of the worldwide species, and to produce a phylogeny of the family as a basis for hypotheses of speciation, diversity and biogeography;

 

The Hypselodoris “blue-complex” in the Atlantic Ocean: an extreme case of sympatric speciation or evolutionary convergence?

Hypselodoris are sea-slugs exhibiting very bright and attractive coloration. A growing body of evidence shows that speciation in the marine realm often occurs in allopatry driven by specialization into tropical/temperate and eutrophic/oligotrophic gradients, but the nudibranch genus Hypselodoris in the Atlantic challenge this view with at least 8 sympatric species belonging to the so called “blue-complex group”, which are all morphologically and chromatically extremely similar. The main objectives of this project are to produce a molecular phylogeny of the Atlantic and Eastern Pacific species of the genus Hypselodoris, and to understand the patterns and processes of speciation within the “blue-complex” species.

 

Systematics revision, phylogenetic relationships, and trophic relationships of the genus Scaphander in the North Atlantic Ocean

Scaphander are “deep-sea” bubble-shell cephalaspidean gastropods occurring worldwide. In a first stage this project will address the systematics and phylogeny of the North Atlantic species through molecular sequencing of mitochondrial and nuclear genes and fine-scale anatomical dissections complemented by scanning electron microscopy. Trophic interactions are assessed by gut content analysis of all species.

 

Principal investigator: Manuel Malaquias (Bergen Museum). Collaborators: David Reid (Natural History Museum, London), Terry Gosliner (California Academy of Sciences), and Juan Lucas Cervera (University of Cadiz, Spain).