Estimating human-mediated dispersal of seeds within an Australian protected area

Abstract

Dispersal is critical step in plant invasions but there is limited information about human-mediated long distance seed dispersal, including in protected areas. Seed dispersal by hikers was quantified for five invasive species (the native Acaena novae-zelandiae, and the non-native weeds Rumex acetosella Anthoxanthum odoratum, Dactylis glomerata and Festuca rubra) in part of Australia's Kosciuszko National Park. The proportion of seeds remaining attached to trousers and socks was quantified for replicated short (150 m) and long (5,000 m) distance walks. Functions were fitted for each dataset, and parameters compared among species and between trousers and socks. Dispersal data were combined with attachment rates and the number of people undertaking walks to estimate the total number of weed seeds that might be dispersed. The power exponential function gave the best fit for the majority of datasets, indicating that detachment probability decreased with distance. Seeds of all five species were more tightly attached to socks than trousers, with some seeds still present on socks at 5,000 m. Anthoxanthum and Acaena seeds were more tightly attached to clothing than the other species. Theoretically 1.9 million seeds could be dispersed on socks or 2.4 million seeds on trousers through a season but the actual numbers are likely to be much lower because of limited weed seed at the start of the walks. Because of differences in attachment and detachment rates, seeds from Acaena were more likely to be dispersed longer distances. Long distance humanmediated seed dispersal is potentially a major cause of spread of invasive weeds into protected areas that favours some invasive species over others.

Human-mediated dispersal of aquatic invertebrates with waterproof footwear

“…In addition, they may represent a new dispersal mechanism in the metacommunity dynamics for patched zones or for a set of isolated habitats in the same protected area (Auffret et al 2014). In both cases, human-mediated dispersal can represent a significant problem to the preservation of the pristine conditions in areas with high conservation value (Pickering et al 2011). Examples of documented invasions in inland waters include the case of North American Great Lakes (Mills et al 1994) but also others by crustaceans such as Daphnia lumholtzi G.O.…”

“…However, few studies focused specifically on the impact of clothes and footwear usage as unintentional dispersal vectors. A representative example is the study by Pickering et al (2011), who investigated the impact of tourism as a dispersal vector of plants in a protected area of Australia. Similar experiments support the importance of clothes and car wheels in seed dispersal (Pickering and Mount 2010).…”

Weed seeds on clothing: A global review

“…By 5 m it ranged from 58% for Brassica nigra (Black mustard) to 65% for Brassica oleracea (Cabbage) for seeds on shoes (Wichmann et al, 2009). For seeds on trousers and socks, by 5 m it ranged from 19% for Heteropogon contortus (Black peargrass) to 80% for Festuca rubra (Red Fescue) on trousers and 16% for H. contortus to 76% for Paspalum urvillei (Vasey Grass) on socks across the 14 species compared using the same basic protocol (Pickering et al, 2011;Ansong and Pickering, 2013c;Ansong and Pickering, unpublished data). By 5 km, nearly all seeds have fallen off clothing, with values ranging from 55% to 100% from trousers, 52%e99% on socks and 99%e100% from shoes (Wichmann et al, 2009;Pickering et al, 2011;Ansong and Pickering, 2013c).…”

“…For seeds on trousers and socks, by 5 m it ranged from 19% for Heteropogon contortus (Black peargrass) to 80% for Festuca rubra (Red Fescue) on trousers and 16% for H. contortus to 76% for Paspalum urvillei (Vasey Grass) on socks across the 14 species compared using the same basic protocol (Pickering et al, 2011;Ansong and Pickering, 2013c;Ansong and Pickering, unpublished data). By 5 km, nearly all seeds have fallen off clothing, with values ranging from 55% to 100% from trousers, 52%e99% on socks and 99%e100% from shoes (Wichmann et al, 2009;Pickering et al, 2011;Ansong and Pickering, 2013c). Some seed can be carried even further, with an average potential dispersal distance of 13 km for seeds collected from the clothing of people cutting meadows in Sweden (Auffret and Cousins, 2013).…”

“…For example 73% of visitors to a national park in Australia carried seeds on their clothing, and modelling indicates that they could collectively carry millions of seeds each year (Pickering et al, 2011). Visitors to even more remote protected areas can still carry large amounts of seeds (Chown et al, 2012;Ware et al, 2012).…”