Are Spiders Getting Bigger?

Increasing rates of urbanization have detrimental effects on animals living within an ecosystem. This is no wonder since concrete is not as hospitable to jungle dwelling animals as vegetation. Although most animals do not fare well in the city, there are some animals that absolutely thrive in urban environments. One example of this phenomena is well demonstrated in the Golden Orb Weaver Spider, which is becoming a little meatier in its physique. Not all GOW Spiders are becoming larger. For example, researchers in Australia measured the body size of the type of GOW Spider that lives in the Australian outback, and they found that the country spiders were noticeably smaller in stature than their city dwelling counterparts.

A group of GOW Spiders that were collected at an inner city park had an average weight of 1.6 grams. While a group of bush dwelling spiders collected from the outback had an average weight of only half a gram. So the city spiders had a body weight that clocked in at three times that of the country spiders, that is pretty significant. Strangely enough, the largest spiders came from wealthier areas of the city, and nobody knows why, but the researchers believe that this weight disparity is happening all over the world.

What possible reasons can you think of that would suggest why city spiders are much larger than country spiders?