Jaco Le Roux

Research interests

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

Cardiospermum grandiflorum (Balloon vine) invasions outside Kruger National Park. My lab is currently investigating the phylogeography of numerous species within Cardiospermum.

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.

Dave Richardson sampling Lantana camara in Kruger National Park.

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.

Pennisetum setaceum on the slopes of Table Mountain.

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. PhD student, Marguerite Blignaut , is inferring population epi-genetic structure in Pennisetum setaceum, a plant with a known lack of genetic diversity in its invasive ranges in South Africa.

Molecular Ecology Lab

PhD students

Ms. Marguerite Blignaut — Project title: Epigenetic structure in a monoclonal grass
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.

MSc students

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

Publications

Peer-reviewed publications

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 40 th 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(12): 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. and 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.
Hardesty B.D., Le Roux, J.J., Rocha, O.J., Meyer, J-Y,Westcott, D. and Wieczorek, A.M. (2011) Getting here from there: testing the paradigm of invasion success. Diversity and Distributions, (in press).
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.

Profile: Dr Jaco J. Le Roux