"Species solidarity" was a term coined by Nathaniel Branden in one of his "official" Objectivist essays back in the day. I cannot recall which one but he used it as a justification for benevolence. So I thought I would float the question.
I agree that the concept is sketchy which probably explains why it only gained one single mention in the entire Objectivist corpus and was never fleshed into an integral part of Objectivism.
The bottom line is that benevolence is separate and distinct from love as Ayn Rand described it.
EDIT: Ayn Rand made reference to "species solidarity" in "The Ethics of Emergencies" in The Virtue of Selfishness:
“The respect and good will that men of self-esteem feel toward other human beings is profoundly egoistic; they feel, in effect: ‘Other men are of value because they are of the same species as myself.’ In revering living entities, they are revering their own life. This is the psychological base of any emotion of sympathy and any feeling of species solidarity.”4
Rand, Ayn (1964-11-01). The Virtue of Selfishness (Signet) (pp. 41-42). Penguin Group US. Kindle Edition.
Note 4 refers to:
Nathaniel Branden, “Benevolence versus Altruism,” The Objectivist Newsletter, July 1962.
(Edited by Luke Setzer on 6/13, 9:25am)