A pinboard by
Maquel Brandimarti

PhD Candidate, The University of Sydney


How do parasites and disease influence population dynamics of overabundant kangaroos

Understanding how parasites and disease influence population dynamics is becoming increasingly important given the overabundance of kangaroos in urban spaces. This project aims to conduct a large field based investigation to shed light on the impact of ectoparasites and gastrointestinal nematodes on host fitness in peri urban eastern grey kangaroos at four populations along the NSW coast. Host fitness will be assessed by measuring individual reproductive success, survival, body condition and blood parameters. The experiment will manipulate parasitism and reproductive hormones in wild kangaroos to estimate the effect hormones play in parasitism and in kangaroo mate selection. Research aims to examine the potential for kangaroos as reservoirs of disease focussing on Q fever, a re-emerging disease that affects humans. A laboratory based disease investigation will be carried out to determine seroprevalence of Q fever in kangaroos in NSW and attempt to ascertain transmission dynamics and subclinical effects Q fever.


Differing impact of a major biogeographic barrier on genetic structure in two large kangaroos from the monsoon tropics of Northern Australia.

Abstract: Tropical savannas cover 20-30% of the world's land surface and exhibit high levels of regional endemism, but the evolutionary histories of their biota remain poorly studied. The most extensive and unmodified tropical savannas occur in Northern Australia, and recent studies suggest this region supports high levels of previously undetected genetic diversity. To examine the importance of barriers to gene flow and the environmental history of Northern Australia in influencing patterns of diversity, we investigated the phylogeography of two closely related, large, vagile macropodid marsupials, the antilopine wallaroo (Macropus antilopinus; n = 78), and the common wallaroo (Macropus robustus; n = 21). Both species are widespread across the tropical savannas of Australia except across the Carpentarian Barrier (CB) where there is a break in the distribution of M. antilopinus. We determined sequence variation in the hypervariable Domain I of the mitochondrial DNA control region and genotyped individuals at 12 polymorphic microsatellite loci to assess the historical and contemporary influence of the CB on these species. Surprisingly, we detected only limited differentiation between the disjunct Northern Territory and QueenslandM. antilopinus populations. In contrast, the continuously distributedM. robustus was highly divergent across the CB. Although unexpected, these contrasting responses appear related to minor differences in species biology. Our results suggest that vicariance may not explain well the phylogeographic patterns in Australia's dynamic monsoonal environments. This is because Quaternary environmental changes in this region have been complex, and diverse individual species' biologies have resulted in less predictable and idiosyncratic responses.

Pub.: 19 Jul '14, Pinned: 25 Aug '17

Measuring the immune system of the three‐spined stickleback – investigating natural variation by quantifying immune expression in the laboratory and the wild

Abstract: Current understanding of the immune system comes primarily from laboratory‐based studies. There has been substantial interest in examining how it functions in the wild, but studies have been limited by a lack of appropriate assays and study species. The three‐spined stickleback (Gasterosteus aculeatus L.) provides an ideal system in which to advance the study of wild immunology, but requires the development of suitable immune assays. We demonstrate that meaningful variation in the immune response of stickleback can be measured using real‐time PCR to quantify the expression of eight genes, representing the innate response and Th1‐, Th2‐ and Treg‐type adaptive responses. Assays are validated by comparing the immune expression profiles of wild and laboratory‐raised stickleback, and by examining variation across populations on North Uist, Scotland. We also compare the immune response potential of laboratory‐raised individuals from two Icelandic populations by stimulating cells in culture. Immune profiles of wild fish differed from laboratory‐raised fish from the same parental population, with immune expression patterns in the wild converging relative to those in the laboratory. Innate measures differed between wild populations, whilst the adaptive response was associated with variation in age, relative size of fish, reproductive status and S. solidus infection levels. Laboratory‐raised individuals from different populations showed markedly different innate immune response potential. The ability to combine studies in the laboratory and in the wild underlines the potential of this toolkit to advance our understanding of the ecological and evolutionary relevance of immune system variation in a natural setting.

Pub.: 21 Dec '15, Pinned: 25 Aug '17

Host Competence: An Organismal Trait to Integrate Immunology and Epidemiology.

Abstract: The new fields of ecological immunology and disease ecology have begun to merge, and the classic fields of immunology and epidemiology are beginning to blend with them. This merger is occurring because the integrative study of host-parasite interactions is providing insights into disease in ways that traditional methods have not. With the advent of new tools, mathematical and technological, we could be on the verge of developing a unified theory of infectious disease, one that supersedes the barriers of jargon and tradition. Here we argue that a cornerstone of any such synthesis will be host competence, the propensity of an individual host to generate new infections in other susceptible hosts. In the last few years, the emergence of systems immunology has led to novel insight into how hosts control or eliminate pathogens. Most such efforts have stopped short of considering transmission and the requisite behaviors of infected individuals that mediate it, and few have explicitly incorporated ecological and evolutionary principles. Ultimately though, we expect that the use of a systems immunology perspective will help link suborganismal processes (i.e., health of hosts and selection on genes) to superorganismal outcomes (i.e., community-level disease dynamics and host-parasite coevolution). Recently, physiological regulatory networks (PRNs) were cast as whole-organism regulatory systems that mediate homeostasis and hence link suborganismal processes with the fitness of individuals. Here, we use the PRN construct to develop a roadmap for studying host competence, taking guidance from systems immunology and evolutionary ecology research. We argue that PRN variation underlies heterogeneity in individual host competence and hence host-parasite dynamics.

Pub.: 13 Dec '16, Pinned: 25 Aug '17