Department of Biological Sciences

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Upcoming Lab Presentations:

 

 

Kemp DJ, Barry K (2010) “Sex, symbiosis and she-males: Evolutionary interactions between butterflies and Wolbachia, a reproductively parasitic endosymbiont”. Poster accepted for presentation at the International Society for Behavioral Ecology, Perth 26 Sept 2010.

Sex, symbiosis and “she-males”: Evolutionary interactions between butterflies and Wolbachia, a reproductively parasitic endosymbiont

 

Wolbachia is an extremely widespread bacterial endosymbiont of invertebrates, which often manipulates its hosts’ reproduction to facilitate its own maternal transmission. One of the more intriguing manipulations is feminisation, whereby Wolbachia hijacks its hosts sex-determining machinery to cause genetic males to develop into viable female phenotypes (se-called “she-males”). While benefiting the bacteria, this disrupts host sex ratios from the Fisherian ideal (50:50), which sets the scene for an evolutionary arms race between host and endosymbiont. One possible weapon in the host’s armoury is mate-choice: males in feminised populations should be advantaged by selecting real female mates rather than she-males.

 

We investigated this aspect of host-endosymbiont evolutionary dynamics using Australian Eurema butterflies. One species, Eurema hecabe, has recently been discovered to suffer Wolbachia feminisation. We report the broader prevalence of Wolbachia infections within this genus, characterise female and she-female phenotypes (focussing upon sexual trait expression), and characterise the mating preferences of infected, cleansed and non-infected populations. Our results suggest a history of rich evolutionary interaction between these butterflies and their reproductively parasitic bacterial endosymbionts.

 

 

Davis J, Kemp DJ, Donald J, Sgro C (2010) “A quantitative genetic analysis of ecological limits to species distribution in Eurema butterflies”. Poster accepted for presentation at the Genetics Society of Australasia meeting, Canberra 4-8 July 2010.

 

A quantitative genetic analysis of ecological limits to species distribution in Eurema butterflies

 

Species often do not extend as far as geographical barriers allow. There is a positive correlation between latitude and species latitudinal range which has been termed Rapoport’s rule. Where this phenomenon occurs climatic conditions may be the limiting factors. The climatic variability hypothesis contends that species at higher latitudes need greater ability to cope with a wider range of climatic conditions.  If this is true then some species may be limited in their capacity to adapt to ecological conditions beyond their range. Tropical species, in particular, are thought to be less tolerant of climatic changes than temperate species, which may be due to specialisation to a constant environment, and which would be evident in low genetic variation for ecological stress traits. To test this we aimed to compare the cold tolerance and desiccation resistance of several species of butterflies of the genus Eurema from Cairns, North Queensland. We compared phenotypic values across a range of species, and then used a quantitative genetic analysis to compare genetic variances for cold tolerance between a broadly distributed (E. hecabe) and a restricted tropical species (E. laeta). Here we present preliminary data on our contrasts and interpret them in relation to key predictions of the climate variability hypothesis.

 

Kemp DJ (2010) Oral Presentation: “Nutrient stress exacerbates genetic variance for development in a butterfly”, abstract accepted for presentation at: Genetics Society of Australasia annual conference, Canberra July4-8, 2010.

 

Nutrient stress exacerbates genetic variance for development in a butterfly

 

Models of adaptive evolution are based on the premise that the different genomes spread across individuals in a population are differentially viable. By definition, individuals in possession of a genotype of high average viability (i.e., ‘good genes’) should, on average, achieve higher levels of performance in fitness-related tasks such as growth and development. However, performance may depend on the environment in a way that no one genotype is the best under all conditions. Alternatively, the relative scaling of performance may vary across environments, such that the differences among genotypes is exacerbated under some conditions. I set out to investigate these issues by rearing full sibling families of the butterfly Eurema hecabe under several environments of differing nutritional quality, and examining their growth and development. The data show a striking interaction between genotype and environment. Whereas all genotypes developed relatively fast under the good and medium quality environment, only some could achieve similar rates of development under the lowest nutritional treatment. Variance in a key component of larval performance in this species is therefore exacerbated under stress, which suggests that the opportunity for natural selection to act on viability in the wild would be greatest under this environment.

 

 

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