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Department of Biological and Medical Sciences
Faculty of Health and Life Sciences
+44 (0)1865 484191
Biology BSc (Hons) single
Animal Biology and Conservation BSc (Hons) single
Eco Evo Devo Postgraduate Summer School
Evelyne Mann (Vetmed Uni, Vienna, 2009)
Victoria Steinmann (Vetmed Uni, Vienna, 2011)
Anna Schönauer (second supervisor, Oxford Brookes University, ongoing)
Abigail Bailey (second supervisor, Oxford Brookes University, ongoing)
Christian Bonatto Paese (second supervisor, Oxford Brookes University, ongoing)
Michaela Holzem (second supervisor, Oxford Brookes University, ongoing)
Joanna Hagen (main supervisor, Oxford Brookes University, ongoing)
Dr. Rachel Wade (co-supervisor, main supervisor: Professor Tim Shreeve)
We are an Evolutionary Biology Group with a particular focus on Molecular evolution, Population Genetics and Evolutionary Developmental Biology.
Currently, our research aims to provide a better understanding of the genetic basis of complex quantitative traits and the evolutionary processes responsible for their evolution.
September 2015- September 2018. Nigel Groome Research Studentship to sponsor Joanna Hagen PhD work.
January 2015- December 2017. ‘Characterising the genetic architecture and fitness effects of rapid morphological diversification.’ NERC. £417,670. (as Researcher Co-investigator)
Identifying the genetic mechanisms underlying phenotypic change is essential to understanding how gene regulatory networks and ultimately the genotype-to-phenotype map evolve. It is recognized that microRNAs (miRNAs) have the potential to facilitate evolutionary change [1, 2and3]; however, there are no known examples of natural morphological variation caused by evolutionary changes in miRNA expression. Therefore, the contribution of miRNAs to evolutionary change remains unknown [1and4]. Drosophila melanogaster subgroup species display a portion of trichome-free cuticle on the femur of the second leg called the "naked valley." It was previously shown that Ultrabithorax (Ubx) is involved in naked valley variation between D.melanogaster and D.simulans [ 5and6]. However, naked valley size also varies among populations of D.melanogaster, ranging from 1,000 up to 30,000μm2. We investigated the genetic basis of intraspecific differences in the naked valley in D.melanogaster and found that neither Ubx nor shavenbaby (svb) [ 7and8] contributes to this morphological difference. Instead, we show that changes in mir-92a expression underlie the evolution of naked valley size in D.melanogaster through repression of shavenoid (sha) . Therefore, our results reveala novel mechanism for morphological evolution and suggest that modulation of the expression of miRNAs potentially plays a prominent role in generating organismal diversity.
Eye and head morphology vary considerably among insects and even between closely related species of Drosophila. Species of the D. melanogaster subgroup, and other Drosophila species, exhibit a negative correlation between eye size and face width (FW); for example, D. mauritiana generally has bigger eyes composed of larger ommatidia and conversely a narrower face than its sibling species. To better understand the evolution of eye and head morphology, we investigated the genetic and developmental basis of differences in eye size and FW between male D. mauritiana and D. simulans. QTL mapping of eye size and FW showed that the major loci responsible for the interspecific variation in these traits are localized to different genomic regions. Introgression of the largest effect QTL underlying the difference in eye size resulted in flies with larger eyes but no significant difference in FW. Moreover, introgression of a QTL region on the third chromosome that contributes to the FW difference between these species affected FW, but not eye size. We also observed that this difference in FW is detectable earlier in the development of the eye-antennal disc than the difference in the size of the retinal field. Our results suggest that different loci that act at different developmental stages underlie changes in eye size and FW. Therefore, while there is a negative correlation between these traits in Drosophila, we show genetically that they also have the potential to evolve independently and this may help to explain the evolution of these traits in other insects.
A striking diversity of compound eye size and shape has evolved among insects. The number of ommatidia and their size are major determinants of the visual sensitivity and acuity of the compound eye. Each ommatidium is composed of eight photoreceptor cells that facilitate the discrimination of different colours via the expression of various light sensitive Rhodopsin proteins. It follows that variation in eye size, shape, and opsin composition is likely to directly influence vision. We analyzed variation in these three traits in D. melanogaster, D. simulans and D. mauritiana. We show that D. mauritiana generally has larger eyes than its sibling species, which is due to a combination of larger ommatidia and more ommatidia. In addition, intra- and inter-specific differences in eye size among D. simulans and D. melanogaster strains are mainly caused by variation in ommatidia number. By applying a geometric morphometrics approach to assess whether the formation of larger eyes influences other parts of the head capsule, we found that an increase in eye size is associated with a reduction in the adjacent face cuticle. Our shape analysis also demonstrates that D. mauritiana eyes are specifically enlarged in the dorsal region. Intriguingly, this dorsal enlargement is associated with enhanced expression of rhodopsin 3 in D. mauritiana. In summary, our data suggests that the morphology and functional properties of the compound eyes vary considerably within and among these closely related Drosophila species and may be part of coordinated morphological changes affecting the head capsule.
The study of speciation has advanced considerably in the last decades because of the increased application of molecular tools. In particular, the quantification of gene flow between recently diverged species could be addressed. Drosophila simulans and Drosophila mauritiana diverged, probably allopatrically, from a common ancestor approximately 250000years ago. However, these species share one mitochondrial DNA (mtDNA) haplotype indicative of a recent episode of introgression. To study the extent of gene flow between these species, we took advantage of a large sample of D.mauritiana and employed a range of different markers, i.e. nuclear and mitochondrial sequences, and microsatellites. This allowed us to detect two new mtDNA haplotypes (MAU3 and MAU4). These haplotypes diverged quite recently from haplotypes of the siII group present in cosmopolitan populations of D.simulans. The mean divergence time of the most diverged haplotype (MAU4) is approximately 127000years, which is more than 100000years before the assumed speciation time. Interestingly, we also found some evidence for gene flow at the nuclear level because an excess of putatively neutral loci shows significantly reduced differentiation between D.simulans and D.mauritiana. Our results suggest that these species are exchanging genes more frequently than previously thought.