A window into key events of spider evolution: Tracking the phylogenetic history of a phenotypically dynamic clade of spiders - the Austral marronoids

• Applicant: Dr. Jonas Wolff
• Subject Area: Systematics and Morphology (Zoology) ; Evolution, Anthropology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451087507

Evolutionary key events, such as the emergence of an ecologically important trait (‘novelty’) or long distance colonization, can deliver explanations for faunal turnovers and diversification events in deep time. Key events can radically change the evolutionary dynamics (i.e. frequency and rates of changes) of traits of a lineage by extending or constraining phenotypic evolvability. However, deep time key events are poorly understood as they are often masked by ongoing evolution. This project will assess a rare exemption, a group of spiders – the Austral marronoids (Araneae: Desidae, Stiphidiidae, Cycloctenidae, Toxopidae), in which usually invariable key traits exhibit an outstanding variation, providing an opportunity to unravel how punctuated changes in the morphology of key traits change phenotypic diversification patterns.By addressing the phylogenetic history of the diverse Austral marronoids, this project will explore the evolutionary mode and dynamics of a major shift in the composition of the spinning apparatus (i.e. loss of the cribellum), the emergence of aerial webs and the loss of foraging webs, all of which are regarded as ‘key innovations’ that have shaped the extant fauna of spiders. It will uncover how these punctuated key events correlate with shifts in the evolutionary rates of phenotypic traits like body size and shape, eye arrangement and cuticular features. To achieve this, the project will build the first comprehensive genus-level phylogeny of Austral marronoid spiders using a combination of target capture and amplicon sequencing techniques. A database of morphometric and behavioural traits will be built based on microscopy and field observations. Based on the phylogenetic and morphological investigation the so far highly unstable systematics of marronoid spiders will be revised, re-defining the Austral families and re-assessing cladistics concepts of previous authors. By integrating the phylogenetic, morphological and behavioural information in a cutting-edge phylogenetic comparative framework, it will be assessed if the repeated cribellum reduction followed similar evolutionary trajectories in different lineages and how these changes interacted with the evolutionary dynamics of somatic and behavioural traits. Similar analyses will be performed on the key traits ‘aerial web’ and ‘web loss’, which are widely assumed to be homoplasic, too. This approach has a strong potential to uncover general patterns of correlated evolution and will advance the understanding of evolutionary constraints, trait evolvability and the role of extended phenotypes in organismic evolution. In addition, this project highlights the enormous scientific value of the invertebrate fauna of ancient ecosystems such as the temperate Gondwanan rainforest in Australia that is threatened by climate change driven droughts and wildfires.

• DFG Programme: Research Grants