Abutilon theophrasti: a comparison of two climate niche models for estimating the species’ potential distribution in New Zealand

Abutilon theophrasti (velvetleaf, butterprint), a problematic weed of crops in some temperate countries, was introduced into New Zealand in 1948 as a potential fibre crop. It has naturalised in the North Island in the Waikato and Auckland regions but its status at the many sites where it was inadvertently sown in 2015 as a contaminant of fodder beet seed lines remains unknown. To determine the potential distribution of the species in New Zealand we used an existing and a newly developed climate niche model, both constructed using the modelling software CLIMEX and a current global climate dataset. The Holt & Boose model, published in 2000, fitted only 54% of the known 3,825 global occurrences of the species. It predicts that most of the North Island is climatically optimal and that most of the South Island is unsuitable. By contrast, the new model, parameterised using a geographically wider set of global occurrences, fitted 98% of the global occurrences. This more robust model predicts that almost all of New Zealand, including all agricultural land, is currently climatically suitable for the species indicating that A. theophrasti could become a weed throughout the country.