The potentially global reach of social media networks is among their defining characteristics. For the first time in history, it is as easy to video-chat and share everyday news with friends on the other side of the planet as with friends in the same city.

Yet the actual penetration of social media networks differs markedly from place to place. According to data from Reach in June 2013, for example, WhatsApp is installed on over 90% of iPhones in Latin America, but under 10% in the United States; Line is on 44% of Spanish handsets yet 1% of French ones; and KakaoTalk is practically universal in South Korea, but nearly unknown beyond East Asia.

Asia’s social login scene is dominated by Facebook, with 82% of the market, Google+ scoring just 2%; in North America, the figures are much closer at 47% and 31%, respectively.

Then there’s China, with a social media scene all of its own. With global behemoths Facebook and Twitter kept out by the Great Firewall, their niches in the social media ecosystem are divided among the likes of Sina Weibo, Tencent Weibo, Renren and Qzone. Despite barely penetrating beyond China, WeChat has more total number of users than WhatsApp, Line, Viber or Skype.

In the same way that isolation allowed different creatures to evolve on the Galapagos Islands and Madagascar, the equivalence between Chinese networks and their global counterparts is far from exact. While Weibo resembles Twitter in limiting posts to 140 characters, it resembles Facebook in allowing threaded comments and likes.

Some of the differences in use of social media networks are driven by cultural circumstances. Unlike on Twitter, for example, it is common for users of Sina Weibo to post jpegs of longer chunks of text – because images are more likely to escape the censors, who are searching text for keywords. It is also because Chinese users usually do not have the patience to follow the links inside Weibo messages.

Censorship shapes the Chinese social media scene in other ways. Following a 2013 crackdown which saw several social commentators on Weibo arrested and the accounts of some political opinion leaders erased, there has been a shift to WeChat; the facility to broadcast some things publicly and share others privately with small groups is increasingly being used for social organizing, as well as for sports team fans to connect and for teachers to get together with students.

Beyond the unique circumstances of the Chinese market, there are examples of how companies have failed to adapt sufficiently to local circumstances to create a critical mass. But, in general, the extent to which cultural differences underlie social media differences should not be overstated.

Many of the current differences in social media use are best explained not by culture, but by historical trends in device use. In Europe and North America, for example, many people were accustomed to accessing social networks on PCs before buying smartphones as a supplementary device; across Asia, it is more common for people’s first experience of the internet and social media to be on a smartphone.

Mobile optimization underlies why, for example, Skype has been caught quickly by the likes of WhatsApp, Line and Viber, despite having a six or seven year head start – Skype was optimized for the PC and has had to adapt to mobile use, while its newer competitors launched with mobile in mind.

Skype is not alone: all social media networks which evolved in a context where PCs dominated, and mobile internet access was based on WAP, have had to re-customize for a smartphone-dominated world. The extent of their success in doing so – or in buying up more mobile-savvy upstarts – will determine how much market share they can hold on to against younger competitors.

As the same smartphone devices become ubiquitous around the world, it is arguable that the social media landscape will gradually converge. Whichever culture they were brought up in, young people with an iPhone tend to find the same features useful.

Part of a series on the top ten trends in social media

Authors: Hu Yong is Associate Professor of Journalism and Communication at Peking University, People’s Republic of China. Takeshi Natsuno is a guest professor at Keio University, Japan.

Image: Icons of messaging applications WhatsApp of Facebook (L), Laiwang of Alibaba Group (C) and WeChat, or Weixin, of Tencent Group, are seen on the screen of a smart phone on this photo illustration taken in Beijing February 24, 2014.