Congratulations to Katie Smith, Natalie Calder and Skipton Woolley for handing in their postgraduate theses in the last fortnight. All three have done major pieces of research that combined new field studies with Museum Victoria Natural Sciences collections.
For her PhD, Katie Smith assessed the hybrid zone between two closely-related south-eastern Australian tree frogs, Litoria ewingi and Litoria paraewingi. A hybrid zone is an area where the geographic distribution of two species overlap in a narrow contact zone. They subsequently share habitat and sometimes cross-breed.
Top: Litoria ewingi calling. Bottom: Litoria paraewingi. Can you spot the difference between these two species?
Image: Katie Smith | Fran Lyndon-Gee
Source: Museum Victoria
In the 1960s, Murray Littlejohn first reported hybridisation in these species in the Kinglake area, collecting specimens and recordings of the male advertisement calls in the 1960s. Katie built upon Murray's work, performing genetic and acoustic analysis on the original specimens and recordings and recent samples to compare the hybrid zone then and now. Says Katie, "it makes you realise what a good job Murray did! It's amazing that he even worked out they are different species because their appearance and calls are so similar."
Main: Murray Littlejohn recording frog calls in the 1960s. Inset: Katie Smith recording frog calls for her PhD.
Source: Murray Littlejohn | Museum Victoria
Katie found that the hybrid zone is quite stable which is particularly interesting because the Kinglake area has changed dramatically over the decades through agricultural and residential development. Her fieldwork, completed before the 2009 bushfires, can't comment on the effect of fire on the hybrid zone but she hopes that ongoing surveys will keep an eye on the situation. When she handed in her thesis, her colleague Susi made a special batch of hybrid frog cupcakes to celebrate!
Hybrid frog cupcakes for afternoon tea!`
Image: Susi Maldonado
Source: Susi Madonado
Natalie Calder's Masters thesis investigated how larval fishes use tide cycles to disperse in Port Phillip Bay. She worked at Governor Reef, near Indented Head on the Bellarine Peninsula, measuring where these tiny hatchlings place themselves in the water column.
As Nat explains, "Upon hatching larvae are translucent, lack scales and are usually less than 1mm long. Studies throughout the first half of the 20th century assumed that larvae were passive particles, at the mercy of tides and currents, with little or no control over where they dispersed."
Three larval fishes. Top: Zeidae (dory family) without fins, jaws or pigmented eyes. Middle: Hemiramphidae (garfish or halfbeak family) in relatively late stage of development, with visible muscle bands. Bottom: Triglidae (gunard or sea robin family) with partially-developed fins, well-developed eyes but still-visible egg yolk sac.
Image: Natalie Calder
Source: Museum Victoria
Since then, scientists have observed that fish larvae display more complex behaviour, and Nat's research contributes to this body of knowledge. She found that fish larvae are quite selective and effectively 'surf' the tides in and out of Port Phillip Bay by exploiting properties of the currents. They rise in the water column to catch fast-moving surface waters during incoming tides, ensuring they stay in the bay rather than be swept out to sea. This better understanding of how larval fish disperse could help ensure the network of marine protected areas are sufficiently connected to keep fish populations healthy.
Another major piece of Masters research with implications for marine reserves was completed by Skipton Woolley, who used marine worms called polychaetes to model the biodiversity of large-scale ecological systems. Using data from museum collections and from new fieldwork in the Kimberley region of Western Australia, he tested whether polychaetes are a good group to use when assessing biodiversity. The idea is that it's not often practical to count every species in an ecosystem, but if the diversity of one group correlates with biodiversity overall, they become a handy indicator that can be used to compare between regions.
By examining 342 species from seven families, he found that that polychaetes are indeed a useful group, because where you find numerous species of polychaetes, you find numerous species of other animals, such as echinoderms and crustaceans. Thus, concludes Skip, "worms are amazing!"
A scaleworm from Skip's Masters project, Iphione muricata (family Polynoidae). The numerous white hairy structures, or chaetae, are what give this group their name - the polychaetes.
Source: Museum Victoria
Amazing too are our students who contribute so much to the museum's research work. Well done Katie, Nat and Skip!
Information for prospective students
MV News: Victoria frogs and bushfires
WA Museum: Marine Life of the Kimberley Region