Meghan has a fun old post asking what is, or will be, your “old school science cred“. The scientific thing you’ve done, or will do, that will one day cause future grad students to look at you and think “Jeez, you’re old.”
Here’s a way to get “old school science cred” that didn’t make it into that post: cite a “personal communication” from someone. Citing “personal communication” was a thing back in the day–but not so much any more.
Here’s a table of the number of papers in Ecology that include at least one instance of the phrase “personal communication”, in 5-year chunks (sorry, too lazy to make a graph):
1981-1985: 403 papers in Ecology cite at least one “personal communication”
Notice that the number of Ecology papers containing the phrase “personal communication” has dropped by well over 50% since the early ’80s, even though the number of papers published by Ecology has increased a lot since the early ’80s. So the percentage of Ecology papers citing “personal communication” has cratered, just within the professional careers of active senior ecological researchers.
I highly doubt this trend is specific to Ecology, I’m sure you’d get similar results if you looked at Am Nat or JAE or Oikos or whatever.
I can think of a few not-mutually-exclusive hypotheses to explain this. Ecology journals publish less natural historical work than they used to (though there’s been a bit of a rebound in recent years). I feel like natural historical papers are particularly likely to cite personal communications for natural historical information that is stored in the heads of natural historians rather than written down in a citable source. Maybe there’s also just a growing expectation on the part of reviewers, editors, and graduate advisors that authors will cite written sources whenever possible. Perhaps because written sources are thought to be easier for others to check for themselves. And maybe there’s a feedback loop–people stop citing “personal communication” because they don’t see anyone else doing it.
I don’t know that this is all that important in itself. I don’t think the decline in “personal communication citations” is either a problem to be solved or a victory to be celebrated. Times change, and one little symptom of changing times is that ecologists mostly don’t cite “personal communication” anymore.