What is a collective author? You might have noticed that the authors of some of your citations are not individual researchers, but instead a group. For example, in this paper, in addition to 3 individual authors, there are also 6 groups listed as authors (e.g. Darwin Tree of Life Consortium).
Collective authors are also called group or corporate authors. They are relatively rare (1%) in scientific publications compared to individual authors, but the trend is growing. According to NIH, the percentage of papers containing collective authors has been increasing in the past 20 years (Figure below).
The rising of collective authorship indicates that there are more and more large-scale collaborations between organizations involving many individual researchers.