I am interested in the evolutionary mechanisms and dynamics of small populations, particularly those involved in invasive plant populations. Most of my research focuses on molecular ecology; using population genetic and phylogenetic approaches to better understand these evolutionary processes that underpin biological invasions.
Current and ongoing research projects
Molecular ecology of plant invasions
Invasive species represent an interesting paradox as they are often genetically depauperate and highly inbred, but seemingly so, without impediment on fitness. Reasons for this paradox are numerous and normally act in different combinations, such as release from natural enemies, pre-adaptations to the new environment, etc. Numerous research projects in my lab (mostly in collaboration with Prof. Dave Richardson and Dr. John Wilson ) are investigating the consequences of invasion histories (human usage, number of independent introductions, propagule pressure, etc.) on population genetic signatures left behind by various species that are naturalized, moderately or highly invasive in South Africa. This research aims to shed light on the genetic consequences faced by invasive species in general.
Plant-microbe interactions during the invasion process
Interactions, such as competition with native species, have been fairly well-studied for many invasive taxa. However, surprisingly little is known about below-ground interactions associated with invasive plants. One of my research interests includes the interactions between nitrogen-fixing bacteria, commonly known as rhizobia, and invasive legumes. The rhizobia - legume relationship could, in some instances, be very taxon-specific and in other very promiscuous. This level of specificity may therefore dictate whether invasive legumes can find suitable bacteria in their newly introduced ranges.
Epigenetic variation and phenotypic plasticity
The Modern Evolutionary Synthesis is based on the assumption that only heritable genetic variation and its random mutational origin explain evolution by natural selection. However, the line between genetic and environmental interactions is blurred by processes such as phenotypic plasticity and epigenetic variation and not well understood. To date no research has been directed towards understanding the importance of epigenetic variation (biochemical modification of DNA building blocks without changes in the actual DNA sequence) in the evolution of natural populations. This may in part be because of the difficulty to disentangle the relative contributions of epigenetic- vs. genetic variation in local adaptation. Ongoing research in my lab is aimed at partially addressing some of these issues.
Molecular Ecology Lab
- Ms. Genevieve Thompson (co-supervisor) — Project title: Molecular ecology of Australian wattles
- Ms. Joice Ndlovu (co-supervisor) — Project title: Molecular ecology of Acacia pycnantha, its antagonists and mutualists.
- Ms. Enelge Gildenhuys — Project title: Unravelling biogeographic uncertainties in the genus Cardiospermum: a multiple species concept approach
- Ms. Haylee Kaplan (co-supervisor) — Project title: Assessing the invasiveness of Acacia stricta in South Africa
- Mr. Dickson Mazibuko (co-supervisor) — Project title: Incidence and distribution of hybrid swarms in Prosopis species in South Africa
- Ms. Nokuthula Mbanyana — Project title: Phylogeography of the Southern African ant genus Ocymyrmex
- Ms. Wafeeka Vardien — Project title: Invasion genetics of Lantana camara in Kruger National Park
- Le Roux, J.J., Hall A.N., Jaftha J.B. and Steyn, P.L. (2001) A Novel Bacillus species isolated from leguminous root-nodules. In: Proceedings of the 40th Annual Conference of the Microscopy Society of Southern Africa: Microscopy Society of Southern Africa, pp. 43-44.
- Le Roux, J.J., Wieczorek, A.M., Ramadan, M.M. and Tran, C.T. (2006) The native provenance of invasive fireweed (Senecio madagascariensis Poir.) in the Hawaiian islands as inferred from phylogenetic analysis. Diversity and Distributions 12: 694–702.
- Le Roux, J.J. and Wieczorek, A.M. (2006) Isolation and characterization of polymorphic microsatellite markers from fireweed, Senecio madagascariensis Poir. (Asteraceae). Molecular Ecology Notes 7: 327-329.
- Le Roux, J.J., Wieczorek, A.M., Wright, M.G. and Tran, C.T. (2007) Super-genotype, global monoclonality defies the odds of nature. PLoS ONE 2(7): e590.
- Le Roux, J.J. and Wieczorek, A.M. (2008) Isolation and characterization of polymorphic microsatellite markers from velvet tree, Miconia calvescens DC. (Melastomataceae). Molecular Ecology Resources 8: 961-964.
- Le Roux, J.J., Meyer J-Y, and Wieczorek A.M. (2008) Genetic diversity and structure of the invasive tree Miconia calvescens in Pacific islands. Diversity and Distributions 14: 935-948.
- Rubinoff, D. and Le Roux, J.J. (2008) Evidence of Repeated and Independent Saltational Evolution in a Peculiar Genus of Sphinx Moths (Proserpinus: Sphingidae). PLoS ONE 3: e4035.
- Le Roux, J.J. and Wieczorek, A.M. (2009) Molecular systematics and population genetics of biological invasions: towards a better understanding of invasive species management. Annals of Applied Biology 154: 1- 17.
- Le Roux, J.J. and Rubinoff, D. (2009) Molecular data reveals California as the potential source of an invasive leafhopper species, Macrosteles sp. nr. severini Hamilton, transmitting the aster yellows phytoplasma in Hawaii. Annals of Applied Biology 154: 429-439.
- Zenni, R.D., Wilson, J.R.U., Le Roux, J.J. and Richardson, D.M. (2009) Evaluating the invasiveness of Acacia paradoxa in South Africa. South African Journal of Botany 75: 485-496.
- Thompson, G.D. Le Roux, J.J., Millar, M.A., Wilson, J.R., Richardson, D.M., Byrne, M. (2009) The Port Jackson 5. South African Journal of Botany 75: 441-442.
- Le Roux, J.J., Wieczorek, A.M., Tran, C.T. and Vorsino, A. (2010) Disentangling the dynamics of invasive fireweed (Senecio madagascariensis Poir. species complex) in the Hawaiian Islands. Biological Invasions 12: 2251-2264.
- Le Roux, J.J., Geerts, S., Ivey, P., Krauss, S., Richardson, D.M., Suda, J. and Wilson, J.R.U. (2010) Molecular systematics and ecology of invasive Kangaroo Paws in South Africa: management implications for a horticulturally important genus. Biological Invasions 12: 3989-4002.
- Gibson, M., Richardson, D.M. Marchante, E., Marchante, H., Rodger, J.G., Stone, G.N., Byrne, M., Fuentes-Ramírez, A., George, N., Harris, C., Johnson, S.D., Le Roux, J.J., Miller, J.T., Murphy, D.J. Pauw, A., Prescott, M.N., Wandrag, E.M. and Wilson, J.R.U. (2011) Reproductive ecology of Australian acacias: important mediator of invasive success? Diversity and Distributions 17: 911-933.
- Le Roux J.J., Brown G., Byrne M., Ndlovu, J., Richardson, D.M., Thompson, G.D. and Wilson, J.R.U. (2011) Phylogeographic consequences of different introduction histories of invasive Australian Acacia species and Paraserianthes lophantha (Fabaceae) in South Africa. Diversity and Distributions 17: 861-871.
- Richardson, D.M., Carruthers, J., Hui, C., Impson, F.A.C., Miller, J.T., Robertson, M.P., Rouget, M., Le Roux, J.J. and Wilson, J.R.U. (2011) Human-mediated introductions of Australian acacias — a global experiment in biogeography. Diversity and Distributions 17: 771-787.
- Rodríguez-Echeverría, S., Le Roux, J.J., Crisóstomo, J.A. and Ndlovu, J. (2011) Jack-of-all-trades and master of many? How does associated rhizobial diversity influence the colonization success of Australian Acacia species? Diversity and Distributions 17: 946-957.
- Thompson, G.D., Robertson, M.P., Webber, B.L., Richardson, D.M., Le Roux, J.J. and Wilson, J.R.U. (2011) Predicting the sub-specific identity of invasive species using distribution models: Acacia saligna as an example. Diversity and Distributions 17: 1001-1014.
- Webber, B.L., Yates, C.J., Le Maitre, D.C., Scott, J.K., Kriticos, D.J., Ota, N., McNeill, A., Le Roux, J.J. and Midgley, G.F. (2011) Modelling horses for novel climate courses: insights from projecting potential distributions of native and alien Australian acacias with correlative and mechanistic models. Diversity and Distributions 17: 978-1000.
- Berthouly-Salazar, Janse van Rensburg, B., Le Roux, J.J., Jansen van Vuuren, B. and Hui, C. (2012) Spatial sorting drives morphological variation in the invasive bird, Acridotheris tristis. PLoS ONE 7: e38145.
- Berthouly-Salazar, C., Cassey, P., Jansen van Vuuren, B., Janse van Rensburg, B., Hui, C., Gardner, M.G. and Le Roux, J.J. (2012) Development and characterization of 13 new, and cross amplification of 3, polymorphic nuclear microsatellite loci in the common myna (Acridotheres tristis). Conservation Genetic Resources 4: 621–624.
- Hardesty B.D., Le Roux, J.J., Rocha, O.J., Meyer, J-Y,Westcott, D. and Wieczorek, A.M. (2012) Getting here from there: testing the paradigm of invasion success. Diversity and Distributions 18: 147-157.
- Harris, C.J., Dormontt, E.E., Le Roux, J.J., Lowe, A. and Leishman, M.R. (2012) No consistent association between changes in genetic diversity and adaptive responses of Australian acacias in novel ranges. Evolutionary Ecology 26: 1345–1360.
- Kaplan, H., Van Zyl, H.W.F., Le Roux, J.J., Richardson, D.M. and Wilson, J.R.U. (2012) Distribution and management of Acacia implexa (Fabaceae) in South Africa: is eradication an option? South African Journal of Botany 83: 23-35.
- te Beest, M. , Le Roux, J.J. , Richardson, D.M. , Brysting, A.K. , Suda, J. , Kubesová, M. and Pyšek, P. (2012). The more the better? The role of polyploidy in facilitating plant invasions. Annals of Botany 109: 19–45.
- Thompson, G.D., Bellstedt, D.U., Byrne, M., Millar, M.A., Richardson, D.M., Wilson, J.R.U. and Le Roux, J.J. (2012) Cultivation shapes genetic novelty in a globally important invader. Molecular Ecology 21: 3187-3199.
- Vardien, W., Richardson, D.M., Foxcroft, L.C., Thompson, G.D, Wilson, J.R.U. and Le Roux, J.J. (2012) Invasion dynamics of Lantana camara L. (sensu lato) in South Africa. South African Journal of Botany 81: 81-94.
- Vardien, W., Richardson, D.M., Foxcroft, L.C., Wilson, J.R.U. and Le Roux, J.J. (2013) Management history determines gene flow in a prominent invader. Ecography (In Press: DOI: 10.1111/j.1600-0587.2012.00120.x)
- Ndlovu, J., Richardson, D.M., Wilson, J.R.U. and Le Roux, J.J. (2013) Co-invasion of South African ecosystems by an Australian legume and its rhizobial symbionts. Journal of Biogeography (In Press)
- Ndlovu, J., Richardson, D.M., O’Leary, M., Wilson, J.R.U. and Le Roux, J.J. (2013) Elucidating the native sources of an invasive tree species reveals unexpected native range diversity and structure. Annals of Botany (In Press).
- Blignaut, M., Ellis, A.G. and Le Roux, J.J. (2013) Towards an universal plant Amplified Fragment Length Polymorphism (AFLP) protocol. PLoS ONE (Accepted pending minor revisions)