Author
Khethani Vincent Mawela
mawelak@arc.agric.za
Agricultural Research Council– Plant Health and Protection,
Pretoria
Coauthors
David Simelane, Agricultural Research Council– Plant Health and Protection, Pretoria , South Africa
Terence Olckers, School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, South Africa, Scottsville, South Africa
Abstract
Two Mexican defoliating chrysomelid beetles, Zygogramma piceicollis and Z. signatipennis were released in South Africa for the biological control of Tithonia rotundifolia (Asteraceae: Heliantheae). The aim was to predict the potential of these beetles to establish and spread in South Africa, using MaxEnt climate modelling. Locality data from 2008-2019 Mexican surveys and the Global Biodiversity Information Facility were used. Surveys revealed that Z. signatipennis was more widespread than Z. piceicollis in Mexico, with some overlap. The average receiver operating characteristic curves for Z. piceicollis and Z. signatipennis predicted high mean area under curve (AUC) values of 0.910 and 0.885, respectively. Jackknife tests showed that mean annual temperature had the highest gain when used in isolation for Z. piceicollis, compared with minimum precipitation of the driest month for Z. signatipennis. The main contributing environmental variables for Z. piceicollis and Z. signatipennis were minimum precipitation of the driest month (37.9 and 46.7%) and the least were maximum annual temperature of the warmest month (3.8 and 12.3%), respectively. MaxEnt modelling predicted that, at least six of South Africa’s nine provinces provides regions that are suitable for establishment of both beetle species, but best suited for Z. piceicollis. Although both beetles are predicted to establish across T. rotundifolia’s range in South Africa, their actual establishment has been poor.
keywords
Agent establishment
Climate matching
MaxEnt modelling
Zygogramma
Weed biocontrol
Highlights
Mean area under curve values for Z. piceicollis and Z. signatipenni were 0.910 and 0.885,
mean annual temperature had the highest gain when used in isolation for Z. piceicollis
The model predicted that six of South Africa’s provinces are suitable for establishment of Zygogramm