Novel urban ecosystems, biodiversity, and conservation.

A great challenge for ecology in the coming decades is to understand the role humans play in eco-evolutionary dynamics. If, as emerging evidence shows, rapid evolutionary change affects ecosystem functioning and stability, current rapid environmental change and its evolutionary effects might have significant implications for ecological and human wellbeing on a relatively short time scale. Humans are major selective agents with potential for unprecedented evolutionary consequences for Earth's ecosystems, especially as cities expand rapidly. In this review, I identify emerging hypotheses on how urbanization drives eco-evolutionary dynamics. Studying how human-driven micro-evolutionary changes interact with ecological processes offers us the chance to advance our understanding of eco-evolutionary feedbacks and will provide new insights for maintaining biodiversity and ecosystem function over the long term.

https://www.cell.com/trends/ecology-evolution/pdf/S0169-5347(14)00249-3.pdf

Eco-evolutionary dynamics in an urbanizing planet.

Human-mediated seed dispersal is recognised as an important, but under-researched, issue. To assess the potential for tourists to act as unintentional seed dispersal agents, we reviewed published and unpublished data on seed dispersal via clothing, vehicles (cars) and in/on horses and donkeys, all of which can be used by tourists. Seeds from 754 species of terrestrial plants have been collected from these vectors, 15% of which are internationally recognised environmental weeds. Seeds were collected from personal clothing and equipment (228 species), the fur of donkeys and horses (42 species), horse dung (216 species) and vehicles (505 species). Most were herbs (429 species) or graminoids (237 species) and native to Europe. Annual Poa, White Clover, Kentucky Bluegrass and Yorkshire Fog were the most frequent species. There have been eight studies specifically on tourists, which identified 12 species on clothing, 26 on vehicles and 133 from horse dung. Methods that minimise the risk of tourists as human-med...

Do tourists disperse weed seed? A global review of unintentional human-mediated terrestrial seed dispersal on clothing, vehicles and horses

Urban rivers as dispersal corridors for primarily wind-dispersed invasive tree species

Aim Patterns of high biodiversity among less mobile organisms throughout isolated locations suggest that passive dispersal importantly contributes to biodiversity We examined the contribution of waterbirds to the dispersal of plant seeds and macroinvertebrates between aquatic wetlands Birds are renowned vectors for seeds of terrestrial plants, but less is known about their role in more dispersal-dependent aquatic systems We therefore performed a meta-analysis on bird-mediated endozoochorous dispersal of aquatic species Location Our review included studies that collected data world-wide Methods We analysed data from 81 peer-reviewed publications on endozoochorous dispersal of aquatic plant seeds and macroinvertebrates by waterbirds Results In total, 36% of 1581 waterbird droppings collected in the field contained one or more intact propagules, with macroinvertebrates found almost as frequently as plant seeds Positive droppings contained on average 33 intact propagules, of which one-third were viable In 728 trials from 17 published feeding experiments 24% of the ingested propagules were retrieved intact, with c 65% both viable and intact As many as 17 species of Anatidae and Rallidae were involved in the dispersal of at least 39 species of macroinvertebrates and seeds from 97 species of plants across a wide taxonomic range Smaller propagules seemed less affected by digestion than larger ones We provide a first quantitative model that can be used to estimate waterbird-mediated dispersal of propagules between wetlands This model indicates that an average waterbird has the potential to disperse five viable propagules after flying more than 100 km, and one additional propagule after flying 300 km Main conclusions We demonstrate that waterbirds have the potential to transport a wide variety of aquatic plants and animals over several hundreds of kilometres High survival of propagules might be explained by propagule adaptations or by the digestive adaptations of birds, whereby energy absorption is thought to be maximized rather than assimilation efficiency Our meta-analysis suggests that waterbirds might contribute significantly to wetland biodiversity around the world, despite several limitations to our current knowledge We outline avenues for future research to address these knowledge gaps

Gut travellers: Internal dispersal of aquatic organisms by waterfowl

Human activities have fundamental impacts on the distribution of species through altered land use, but also directly by dispersal of propagules. Rare long-distance dispersal events have a disproportionate importance for the spread of species including invasions. While it is widely accepted that humans may act as vectors of long-distance dispersal, there are few studies that quantify this process. We studied in detail a mechanism of human-mediated dispersal (HMD). For two plant species we measured, over a wide range of distances, how many seeds are carried by humans on shoes. While over half of the seeds fell off within 5 m, seeds were regularly still attached to shoes after 5 km. Semi-mechanistic models were fitted, and these suggested that long-distance dispersal on shoes is facilitated by decreasing seed detachment probability with distance. Mechanistic modelling showed that the primary vector, wind, was less important as an agent of long-distance dispersal, dispersing seeds less than 250 m. Full dispersal kernels were derived by combining the models for primary dispersal by wind and secondary dispersal by humans. These suggest that walking humans can disperse seeds to very long distances, up to at least 10 km, and provide some of the first quantified dispersal kernels for HMD.

Robert Gould

Papers

Human-mediated dispersal of seeds over long distances