Bright lights, big city a great lifestyle for these spiders
20 August 2014
City life does not suit everyone but golden orb-weaving spiders thrive in urban landscapes, a University of Sydney study shows.
"City-dwelling orb-weaving spiders grow larger and could produce more offspring than their country cousins our research shows," said Elizabeth Lowe, a PhD candidate in the University's School of Biological Sciences and lead author of a study published in the journal PLOS today.
This study shows invertebrates are sensitive to urbanisation but that not all species are negatively affected by living in cities.
"Our findings show the impact urbanisation can have on local wildlife. While many species do not survive encroaching urbanisation and the consequent loss of native habitat, others have a more complex relationship with man-made changes to the landscape.
The researchers collected golden orb-weaving spiders (Nephila plumipes) from across the Sydney city region. The spiders are abundant on Australia's coast in both urban and natural environments and, once matured, remain in the same location for the rest of their lives.
"We quantified the degree of urbanisation of 20 sites then looked at changes in the spiders' body size, fat reserves and ovary weight," Ms Lowe said.
The results show spiders in areas with more vegetation cover had smaller bodies and larger bodies when located in urbanised areas, characterised by increased housing and population density and hard surfaces such as roads and buildings.
The authors also found that the spiders' reproductive ability, measured by increased ovary weight, appeared to increase in urban areas.
"Two reasons likely to explain the differences between these spiders in urban and non-urban environments are temperature and prey availability. Hard surfaces and lack of vegetation lead to the well-known 'urban heat island' effect with more heat retained than in areas with continuous vegetation. Higher temperature is associated with increased growth and size in invertebrates.
"Urban lighting also may be a contributing factor as it attracts insects and means more food for spiders in those environments. This increase in prey would result in bigger, heavier, more fecund spiders.
Associate Professor Dieter Hochuli from the School of Biological Sciences and Professor Shawn Wilder, now at Oklahoma State University, are corresponding authors on the paper.
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