Pablo González-Moreno1,2, Muhammad Usman3, Ahtisham Akbar3, Hamza Khan3, Saad Khan3, Tim Beale4, Julien Lamontagne-Godwin2, Joseph Fennell5, Abdul Rehman3 and Rene P. Breton5
1ERSAF, University of Cordoba, 14014, Spain
2CABI, Bakeham Lane, Egham, Surrey, TW20 9TY, UK
3CABI Data Gunj Baksh Road, Satellite Town, PO Box 8, Rawalpindi, Pakistan
4CABI, Nosworthy Way, Wallingford, Oxfordshire, OX10 8DE, UK
5Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
Understanding the factors shaping the distribution of invasive plants is a key aspect to efficiently manage them. For example, this information can be used as a tool to predict the likelihood of presence or potential abundance of an invasive plant impacting agriculture, informing policy and managers on where to act to avoid further spread or the locations where more intense management is required. Despite the relevance of this tool, little is known about the factors that influence the occurrence and abundance of agricultural and environmental invasive species at different temporal (seasons) and spatial scales (e.g. regional, landscape and local). We use Parthenium weed (P. hysterophorus) in Pakistan as study case to explore these questions. Parthenium weed is an herbaceous plant native to the American continent and is highly invasive in both disturbed and natural habitats around the world, particularly in south-east Asia, Australia and east Africa. Parthenium weed reduces local plant biodiversity; crop and pasture yields through aggressive competition and allelopathy; and poses health hazards to livestock and humans. Parthenium weed was introduced into Pakistan in the 1980s and is spreading rapidly from the Gujrat district in the Northern part of Punjab Province, where it was first reported. We carried out stratified road sampling across Punjab and KPK provinces of Pakistan collecting 1400 sampling points across two seasons (Autumn 2018 and Winter 2019) including information on the abundance of Parthenium weed at each habitat type. Parthenium showed higher probability of occurrence in the North of Punjab, reducing its likelihood of occurrence towards the north of KPK (lower temperature) and south of Punjab (drier areas). Besides climate suitability, this pattern also reflects the spread of Parthenium from its first introduction point in Pakistan. Regarding habitats, Parthenium had higher probability of occurrence in field crop margins and natural vegetation in wet areas, while planted field crops and forest areas showed the lowest probability. The abundance of Parthenium in field crops increased towards maturity and harvest of the crop indicating the high abundance of Parthenium seed in the soil bank likely suppressed by herbicides. Parthenium also showed higher probability of occurrence in national and district roads (i.e. higher vehicle frequency) in comparison to local and unpaved roads. This pattern reflects the association of Parthenium with higher disturbances, but also the likelihood of higher dispersal rates on roads with higher use. Considering the current distribution pattern, it is likely that Parthenium will continue spreading towards the south of Punjab and Sindh provinces taking advantage of the fertile and irrigated areas following the Indus river.