Thanks for getting back to me on this.
The earliest reference for "charismatic megavertebrates" that I found
was from an April 22, 1985 issue of Newsweek magazine:
April 22, 1985
Saving 'Charismatic' Animals
The latest tactic acknowledges that public support cannot be mobilized
to save the snake mite -- or thousands of other homely beasts.
Instead, within the past year many wildlife conservationists have
forged a policy of preserving and promoting "charismatic
megavertebrates," the pandas, tigers, okapis and other glamorous
rarities that rivet public sentiment. If this is a rude repudiation of
the conservation purist's all-or-nothing creed, it's also a deftly
plotted political practicality. "There is a sense of mission now, and
of encouragement," says eminent Harvard zoologist E. O. Wilson. "Our
most easily appreciated species can call attention to the plight of
our entire ecosystem."
A similar excerpt can be seen from a 1988 NY Times article on the
Endangered Species Act:
The New York Times
November 27, 1988
15-Year Scorecard; The Law Saves A Few Species From Oblivion
M. Rupert Cutler, president of Defenders of Wildlife...While the
species that Dr. Cutler called ''charismatic megafauna,'' such as
whales and grizzly bears, get most of the public attention, he said
the law is supposed to provide equal protection for ''enigmatic
microfauna and flora,'' including insects, plants, fish and mollusks.
What is needed, he said, are programs that protect the habitats of
whole communities of living creatures.
By the way, I *almost* found you a 1979 reference as well:
The Washington Post
April 2, 1979
'Scarlet Letter': TV Takes on 'A' Moral
If Hauser's intent was somehow to translate Howthorne's writing style
into appropriate visual term, the aim has been realized at the cost of
dramatic and emotional credibility. As Hester Prynne, the indisputably
charismatic Meg Foster spends so much of the first two hours glaring
wide-eyed into air that she suggests a near-sighted knockout adjusting
her peeners to newly fitted contact lenses.
Of course, that still leaves us with the question of what, exactly,
Hope this is the information you needed.
Before rating this answer, please let me know if anything here needs
search strategy: searched a variety of full text newspaper and
magazine databases to identify early uses of the phrases in question.