Dr Toby Bolton, School of Biological Sciences, Flinders University

	School of Biological Sciences Faculty of Science & Engineering

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Dr Toby Bolton

Research

Reproduction and development of marine invertebrates

I am interested in the ecological consequences of differences in reproductive strategies among marine invertebrates. Early career funding will be used to establish a research program examining the relationship between different reproductive strategies of marine invertebrates (i.e. direct development, brooding offspring, lecithotrophic larval development, planktotrophic larval development) and their population genetic structure around Southern Australia. This research will also facilitate a range of other investigations into the biology and ecology of marine invertebrates around Southern Australia.

Invasive species

I have active research into the ecology of marine invasive species and will soon be establishing collaborations with researchers at SARDI to investigate invasive species in South Australian waters. Ongoing work includes collaboration with Assoc. Prof. Monty Graham at the Dauphin Island Sea Lab, Alabama, on a project that incorporates both marine biogeography and molecular ecology. We are investigating the invasive history and biology of the Australian Spotted Jellyfish, Phyllorhiza punctata, through molecular studies of native and non-native populations. Phyllorhiza punctata (Australian Spotted Jellyfish) has a 200-year history of invading tropical environments.

My current work seeks answer three questions:

did the invasion of the Gulf of Mexico by P. punctata represent mass invasion by medusae from other populations (Northern Caribbean) mediated by the Caribbean Loop Current or delayed propagation of cryptic benthic polyp life-history stages that may have been present in the Gulf for a considerable time
are the morphological differences apparent among populations of Phyllorhiza independent of genotypic variation (i.e. plastic responses to environment that may enhance the probability of successful invasion by overcoming genetic bottlenecks associated with bioinvasions) and
how do both time-dependent genetic differentiation and phenotypic plasticity influence our perception of how invasive species are defined and ultimately linked to, or masked from, it’s source population.

This aspect of the project is its most intriguing since species identification and mode of introduction become very complex when a species exhibiting morphological plasticity is introduced to a novel environment. This project is employing a molecular approach to resolve population isolation and dispersal patterns that are poorly known for the vast majority of invasive species. In addition, genotypes derived from the molecular study are being compared to phenotypes. Phenotypes are being derived from detailed macro-morphological measurements of specimens from all persisting populations of P. punctata globally and compared using multivariate statistical techniques.

Functional Ecology and Biomechanics

I am also interested in the structure, function and evolution of biological materials and organism designs. My PhD research partitioned the physiological and mechanical (viscosity-induced) components of reduced water temperature on the functional performance of marine invertebrate larvae. The broader question being examined was whether temperature-mediated differences in water viscosity could act as a selective pressure on the evolution of reproductive strategies of marine invertebrates (i.e. larval form and development mode) across latitudinal gradients by influencing their functional performance.

Recent research has included investigations into the functional roles of complex extracellular structures that surround the eggs of many marine invertebrates. During spawning, eggs are sheared between the walls of the oviduct and these forces have the potential to destroy the eggs. We have estimated shear stresses imposed on the eggs of echinoids during spawning using modified equations (to account for the non-Newtonian behaviour eggs in a fluid) describing laminar fluid flow through pipes. We have also measured the responses of these extracellular layers to compressive forces applied using micro-mechanical methods. These measurements, in conjunction with estimates of the forces that the eggs experience during spawning, suggest that there is a causal relationship between the levels of force that the eggs experience and the evolution of the structure and mechanical properties of the extracellular layers.

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