Lahcen Campbell
Web page for Lahcen Campbell. PhD student.
Lahcen obtained a B.Sc. degree in Biology at the The National University of Ireland, Maynooth. His undergraduate thesis focused on the evolution of Arthropoda using mitogenomic data. He began his PhD (funded by Science Foundation Ireland) in September 2008.
Broad interests:
My main interests focus on the evolution of major animal radiations, specifically the understanding the processes that lead to speciation, genome evolution and adaptation. Studying the evolution of mechanisms and tempo of early animal evolution is fundamental to many different areas of biological understanding. It could be said that, in order to fully gain true insight into any underlying biological process for example, you must first view the driving forces of evolutionary processes in terms of a solid phylogenetic framework. My main area of interest revolves around the evolution of the major invertebrate group known as the Arthropoda, and also other deep branching non-bilaterian groups such as Porifera (Sponges) and Cnidaria (Corals & Jellyfish etc.). Animal groups such as arthropods provide an excellent platform in which to understand the emergence of many of the higher-level animal characteristics e.g. bilateral symmetry, gene regulation, vision and body plan form.
The phylum Arthropoda represents the largest and most bio diverse group of animals to ever live, not only in terms of shear numbers of species but also ecological niche filling, and can trace their evolutionary history back hundreds of millions of years to a time of major animal radiation (Cambrian period, 543-490 mya). The arthropods contain some of the most well understood biological model organisms; (e.g. Drosophila) and also contain many ecologically and economically important animals groups (e.g. Honey bee, Mosquito, Marine krill). Aside from their direct ecological impact, the arthropods represent one of the best groups of Metazoans to study in order to gain insight into fundamental processes of evolution. In terms of phylogenetic understanding, the arthropods are one of the best ‘case studies’ in which to improve our understanding of the processes of evolution. Features of arthropod evolution, such as: deep branching, rapid diversification, large species number and hugely diverse bauplan make understanding arthropod evolution very fruitful, yet challenging.
Research Focus:
My PhD research focuses on the evolution of deep branching points within Arthropoda, specifically the four extant sub-phyla (Crustacea, Hexapoda, Myriapoda, Chelicerata). Arthropoda have stirred up much scientific attention and debate since the turn of the 20th century (Charles Darwin spent much time examining the ability of Honey bee’s to construct near perfect hexagonal honey combs), since then the group has amassed a huge amount of different hypotheses on their evolutionary history. Many hypotheses steamed from morphological studies, but since the advent of the molecular era many previously accepted hypotheses have been called into question.
Currently one of the major problems in arthropod Systematics (main focus of my PhD) is the problem of the position of Myriapods. The Myriapoda sub phylum has been posited to lie with crustaceans and insects in a clade referred to as Mandibulata (Snodgrass 1938). All groups within Mandibulata are united by the presence of a biting mouthpart known as the mandible, with Mandibulate arthropods united with many other uniting homologies. Recently, molecular sequence data has however inferred their position to be more closely related to Chelicerates (e.g. Spiders, Scorpions, Ticks), in a clade referred to as Myriochelata (Pisani et al. 2004) or paradoxopoda (Mallatt et al. 2004), this latter name referring to the apparent lack of uniting morphological synapomorphies. It is apparent now, due to the rapid diversification of early stem branch arthropods and long evolutionary history, much of the phylogenetic signal present for internal deep branches within Arthropoda has become difficult to uncover.
In order to try and provide additional sources of data in which to test the position of Myriapoda within Arthropoda we have applied next generation sequence technology to sequence small RNA libraries. These small RNA libraries were constructed in order to identify small RNA regulatory elements called microRNAs. MicroRNAs, first discovered to be important regulators of developmental timing in the model organism C. elegans (Lee et al. 1993) are short non-protein coding regulatory elements that function in mRNA regulation throughout development and the adult lifecycle. MicroRNAs have been shown to be useful indicators of phylogenetic history (Wheeler et al. 2009) due to the unique properties of their evolution (e.g. High rate of gain, low secondary mutation rate once a acquired in a genome and low probability of convergent evolution). Due to their unique properties, miRNAs are therefore a useful independent data source in which to test between competing phylogenetic hypotheses and we therefore are interested in their use as phylogenetic markers. Additionally, we have applied genomic scale data sets to the problem of Arthropod phylogenetics, with reanalyses and expansions of previously published phylogenomic studies (e.g. Dunn et al. 2008).
Additionally, miRNA and phylogenomic approaches have also recently been applied to the problem of rooting the arthropod tree in relation to its more recent common ancestors, the Onychophora (Velvet worms) and Tardigrada (Water-Bears). These three phyla together have long been referred to as Panarthropoda (Neilsen 2001), with common uniting morphological synapomorphies such as paired ventrolateral walking appendages, segmental organization and a cuticle composed of alpha-chitin. Although strong evidence supporting the grouping of tardigrades within Panarthropoda exists, many recent phylogenetic and large-scale phylogenomic analyses have placed tardigrades within the Cycloneuralia sister group to Nematoda (Round-worms). This grouping has however been tenuous as tardigrades have been shown to have a high rate of evolution and so may represent an artifactual grouping due to systematic artifacts such as Long-branch attraction.
Publications:
2011:
Campbell, L.I., Rota-Stabelli, O., Edgecombe, G.D., Marchioro, T., Longhorn, S.J., Telford, M.J., Philippe, H., Rebecchi, L., Peterson, K.J., and Pisani D. (2011) MicroRNAs and phylogenomics resolve the relationships of Tardigrada and suggest that velvet worms are the sister group of Arthropoda.Proceedings of the National Academy of Science, USA. doi: 10.1073/pnas.1105499108 [LINK]
Rota-Stabelli, O., Campbell, L., Brinkmann, H., Edgecombe, G.D., Longhorn, S.J., Peterson, K.J., Pisani, D., Philippe, H., and Telford, M.J. (2011) A congruent solution to arthropod phylogeny: phylogenomics, microRNAs and morphology support monophyletic Mandibulata. Proceedings of the Royal Society: B series, 278:1703 298-306. doi: 10.1098/rspb.2010.0590 [LINK] See nature news article here.
Other Articles:
2011:
http://communications.nuim.ie/press/060911.shtml
http://www.pikaia.eu/EasyNe2/Notizie/Uniti_per_le_gambe.aspx
2010:
http://communications.nuim.ie/press/250810.shtml
Conference Presentations
8th biennial meeting of The Systematics association. Belfast, 2011
Title: Minuscule tardigrades, microRNAs and phylogenomics reveal velvet worms as the Arthropod sister group. Lahcen Campbell, Omar Rota-Stabelli ,Trevor Marchioro, Stuart Longhorn, Gregory Edgecombe, Max Telford, Herve Philippe, Lorena Rebecchi, Kevin Peterson, Davide Pisani.
Evolution 2011. Oklahoma, 2011
Title: Minuscule tardigrades, microRNAs and phylogenomics reveal velvet worms as the Arthropod sister group. Lahcen Campbell, Omar Rota-Stabelli ,Trevor Marchioro, Stuart Longhorn, Gregory Edgecombe, Max Telford, Herve Philippe, Lorena Rebecchi, Kevin Peterson, Davide Pisani.
Young Systematists forum. London, 2010
Title: Minuscule tardigrades, microRNAs and phylogenomics reveal velvet worms as the Arthropod sister group. Lahcen Campbell, Omar Rota-Stabelli ,Trevor Marchioro, Stuart Longhorn, Gregory Edgecombe, Max Telford, Herve Philippe, Lorena Rebecchi, Kevin Peterson, Davide Pisani.
Posters:
Society for Molecular biology and Evolution. Lyon, 2010.
MicroRNAs provide additional evidence for the traditional Mandibulata hypothesis within the Arthropoda. LI Campbell, SJ Longhorn, O Rota-Stabelli, MJ Telford, KJ Peterson, D Pisani. [LINK]
Systematics. Leiden, 2010.
Sponges are not Eumetazoans: Complete Mitochondrial genomes support a sister group relationship between the sponges and the other animals. Lahcen I. Campbell & Davide Pisani.
Young Systematists forum. London, 2009.
Sponges are not Eumetazoans: Complete Mitochondrial genomes support a sister group relationship between the sponges and the other animals. Lahcen I. Campbell & Davide Pisani.
