Prosopis invasions in East Africa offer a unique opportunity to investigate whether some Prosopis species or genotypes are more likely to expand their range following their introduction than others, because different Prosopis species were introduced about 40 years ago and the founder trees from which the invasive populations were generated, are still present.

To address this question, PhD student Maria Loreto is conducting a reciprocal transplant experiment in July 2016, using seeds from the first individuals of Prosopis species planted in Kenya as well as seeds from trees growing at the invasion front.

A reciprocal transplant experiment is being carried out to assess differences between offspring from original Prosopis plantations and invasive populations.

One and a half years after the seedlings were planted, only P. juliflora trees from the invasive population reached reproductive maturity. Interestingly, in their native range, the Americas, mesquite trees mature only after 3 years. She also found that under experimental conditions seeds from invasive P. juliflora had a higher germination rate than seeds from the founder populations. Earlier flowering and seed production increase the reproductive output and higher seed germination favours seedling establishment. Hence, these first results indicate that trees from the invasive population have better ability to spread and invade new areas than the originally planted genotypes.