Evolution and extinction risks of sharks, rays, and skates

(FWF-Project 33820)

Primary Investigator: Univ.-Prof. Dr. Jürgen Kriwet

Team

• Univ.-Prof. Dr. Jürgen Kriwet (PI)

• Julia Türtscher, MSc (PhD student)

• Patrick L. Jambura, MSc (PhD student)

Collaborators

• Prof. Dr. Gavin Naylor, Florida Museum of Natural History, University of Florida, USA

• Dr. G. Marramà, Dipartimento di Scienze della Terra, Università degli Studi di Torino, Italy

Abstract

Wider research context/theoretical framework

Sharks, rays, and skates (Elasmobranchii) and ratfishes (Holocephali) are the last extant members of chondrichthyans, being sister to all other living jawed vertebrates. This ancient lineage survived five mass extinctions and developed diverse morphological and biological traits allowing them to occupy a variety of different ecological niches as meso- or apex predators in aquatic food webs. Despite their evolutionary success, ca. 30% of all species are currently threatened by anthropogenically impacts. Extinction of only few species of this evolutionary distinctive clade can cause significant pruning of the tree of life with subsequent loss of millions of years of evolutionary history.

Hypotheses/research questions/objectives

The main goal is to disentangle the reasons underlying their success by examining the evolution of morphological and ecological traits. Questions addressed are: (1) What are the systematic positions and phylogenetic interrelationships of extinct taxa? (2) How do morphological traits and body shapes evolve through time? (3) What are the reasons for the many homoplastic characters in morphology-based phylogenies? (4) What is the timing and tempo of morphological trait and phenotypic evolution? (5) What are their future perspectives and which traits may increase their evolutionary fitness?

Approach/methods

A reliable and robust time-calibrated tree for extinct taxa within a phylogenetic framework of extant taxa will be built employing meta-analytical approaches, based on supermatrix approaches combining morphological and molecular data sets of fossil and extant taxa, within parsimony and Bayesian frameworks. This procedure (1) allows performing phylogenetic analyses and to analyse the nature of homoplastic character distribution, (2) provides tools for modelling complex origination, diversification and extinction dynamics, (3) enables to reconstruct macroevolutionary patterns through time, and (4) forms the scaffold for a revised EDGE analysis to determine vulnerable clades.

Level of originality/innovation

Originality and innovation of this project arise from the multidisciplinary approach combining morphology, molecular biology, palaeobiology, ecology, and conservation biology with a set of new statistical approaches. The combined approaches will profoundly inform about the evolution and success of elasmobranchs, and by including deep-time perspectives will allow identifying clades for which effective conservation priorities are necessary to maintain this unique evolutionary line of vertebrates.