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Department of Biological and Medical Sciences
Faculty of Health and Life Sciences
+44 (0)1865 488629
Biological Sciences BSc (Hons)
Animal Biology and Conservation BSc (Hons)
Eco Evo Devo Postgraduate Summer School
Evelyne Mann (Vetmed Uni, Vienna, 2009)
Victoria Steinmann (Vetmed Uni, Vienna, 2011)
Luis Baudouin Gonzalez (second supervisor, Oxford Brookes University, ongoing)
Abigail Bailey (second supervisor, Oxford Brookes University, ongoing)
Anna Schönauer (second supervisor, Oxford Brookes University, 2013-2016)
Christian Bonatto Paese (second supervisor, Oxford Brookes University, 2015-2018)
Michaela Holzem (second supervisor, Oxford Brookes University, 2015-2019)
Joanna Hagen (main supervisor, Oxford Brookes University, 2015-2019)
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)
The paradigm of isolation in southern refugia during glacial periods followed by expansions during interglacials, producing limited genetic differentiation in northern areas, dominates European phylogeography. However, the existence of complex structured populations in formerly glaciated areas, and islands connected to mainland areas during glacial maxima, call for alternative explanations. We reconstructed the mtDNA phylogeography of the widespread Polyommatus icarus butterfly with an emphasis on the formerly glaciated and connected British Isles. We found distinct geographical structuring of CO1 haplogroups, with an ancient lineage restricted to the marginal European areas, including Northern Scotland and Outer Hebrides. Population genomic analyses, using ddRADSeq genomic markers, also reveal substantial genetic structuring within Britain. However, there is negligble mito-nuclear concordance consistent with independent demographic histories of mitochondrial vs. nuclear DNA. While mtDNA-Wolbachia associations in northern Britain could account for the geographic structuring of mtDNA across most of the British Isles, for nuclear DNA markers (derived from ddRADseq data) butterflies from France cluster between northern and southern British populations – an observation consistent with a scenario of multiple recolonisation. Taken together our results suggest that contemporary mtDNA structuring in the British Isles (and potentially elsewhere in Europe) largely results from Wolbachia infections, however, nuclear genomic structuring suggests a history of at least two distinct colonisations. This two-stage colonisation scenario has previously been put forth to explain genetic diversity and structuring in other British flora and fauna. Additionally, we also present preliminary evidence for potential Wolbachia-induced feminization in the Outer Hebrides.
In the last 240,000 years, males of the Drosophila simulans species clade have evolved striking differences in the morphology of their epandrial posterior lobes and claspers (surstyli). These appendages are used for grasping the female during mating and so their divergence is most likely driven by sexual selection. Mapping studies indicate a highly polygenic and generally additive genetic basis for these morphological differences. However, we have limited understanding of the gene regulatory networks that control the development of genital structures and how they evolved to result in this rapid phenotypic diversification. Here, we used new D. simulans/D. mauritiana introgression lines on chromosome 3L to generate higher resolution maps of posterior lobe and clasper differences between these species. We then carried out RNA-seq on the developing genitalia of both species to identify the expressed genes and those that are differentially expressed between the two species. This allowed us to test the function of expressed positional candidates during genital development in D. melanogaster. We identified several new genes involved in the development and possibly the evolution of these genital structures, including the transcription factors Hairy and Grunge. Furthermore, we discovered that during clasper development Hairy negatively regulates tartan (trn), a gene known to contribute to divergence in clasper morphology. Taken together, our results provide new insights into the regulation of genital development and how this has evolved between species.
Male genital structures are among the most rapidly evolving morphological traits and are often the only features that can distinguish closely related species. This process is thought to be driven by sexual selection and may reinforce species separation. However, while the genetic bases of many phenotypic differences have been identified, we still lack knowledge about the genes underlying evolutionary differences in male genital organs and organ size more generally. The claspers (surstyli) are periphallic structures that play an important role in copulation in insects. Here, we show that divergence in clasper size and bristle number between Drosophila mauritiana and Drosophila simulans is caused by evolutionary changes in tartan (trn), which encodes a transmembrane leucine-rich repeat domain protein that mediates cell–cell interactions and affinity. There are no fixed amino acid differences in trn between D. mauritiana and D. simulans, but differences in the expression of this gene in developing genitalia suggest that cis-regulatory changes in trn underlie the evolution of clasper morphology in these species. Finally, analyses of reciprocal hemizygotes that are genetically identical, except for the species from which the functional allele of trn originates, determined that the trn allele of D. mauritiana specifies larger claspers with more bristles than the allele of D. simulans. Therefore, we have identified a gene underlying evolutionary change in the size of a male genital organ, which will help to better understand not only the rapid diversification of these structures, but also the regulation and evolution of organ size more broadly.
Animal terminalia represent some of the most diverse and rapidly evolving structures in the animal kingdom, and for this reason have been a mainstay in the taxonomic description of species. The terminalia of Drosophila melanogaster, with its wide range of experimental tools, have recently become the focus of increased interest in the fields of development, evolution, and behavior. However, studies from different disciplines have often used discrepant terminologies for the same anatomical structures. Consequently, the terminology of genital parts has become a barrier to integrating results from different fields, rendering it difficult to determine what parts are being referenced. We formed a consortium of researchers studying the genitalia of D. melanogaster to help establish a set of naming conventions. Here, we present a detailed visual anatomy of male genital parts, including a list of synonymous terms, and suggest practices to avoid confusion when referring to anatomical parts in future studies. The goal of this effort is to facilitate interdisciplinary communication and help newcomers orient themselves within the exciting field of Drosophila genitalia.
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.