Friday, 5 August 2011

New Honours Student in the Lab

Citra Jewson-Brown has joined the Lab.

Citra will investigate how herbivory affects fitness in snow gum seedlings. Upslope advance of snow gums in the Australian alps are thought to be mostly due to increases in temperature, but we think herbivory also plays a role.

The basic starting point for this project is the observation that herbivory on eucalypt saplings varies dramatically in the high country. Some saplings (e.g. near treeline) have high levels of defoliation whereas other seedlings (in subalpine woodlands and snowplains) do not suffer as much. Why? Do ants ‘defend’ saplings against defoliation – many saplings have ant nests at the base of saplings and these tend scale insects. Hence, as elsewhere, perhaps the ants 'protect' the scale and in the process, defend saplings from defoliators.
There are three basics steps that will be undertaken in this project:
Step 1 – quantify the nature of herbivory across sites that vary in altitude, within a plant, within a season
Step 2 – quantify the abundance of ants and scale on saplings – and how this varies with altitude
Step 3 – experiment by excluding ants (and/or scale) from a number of saplings and compare to unexcluded saplings (where there is an obvious utilization)
What we hope to learn – controls on eucalypt ‘performance’  (a key species in the alpine) are driven by factors other than climate; one may be an interaction with another key species (ants) which may themselves be affected by climate and non-climate factors (scale).

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