  Collaborations are pervasive in current science. Collaborations have been
studied and encouraged in many disciplines. However, little is known how a team
really functions from the detailed division of labor within. In this research,
we investigate the patterns of scientific collaboration and division of labor
within individual scholarly articles by analyzing their co-contributorship
networks. Co-contributorship networks are constructed by performing the
one-mode projection of the author-task bipartite networks obtained from 138,787
papers published in PLoS journals. Given a paper, we define three types of
contributors: Specialists, Team-players, and Versatiles. Specialists are those
who contribute to all their tasks alone; team-players are those who contribute
to every task with other collaborators; and versatiles are those who do both.
We find that team-players are the majority and they tend to contribute to the
five most common tasks as expected, such as "data analysis" and "performing
experiments". The specialists and versatiles are more prevalent than expected
by a random-graph null model. Versatiles tend to be senior authors associated
with funding and supervisions. Specialists are associated with two contrasting
roles: the supervising role as team leaders or marginal and specialized
contributions.
