Fig. 1

Proportion of studies linked to study type classification (n = 409) and the number of publications on cultural keystone species over time (2003–2016) available from Publish or Perish software (n = 409). a Study type classifications include (1) studies that solely mention the cultural keystone species concept, (2) studies that mention a given species as a cultural keystone species without a direct test or measure of species cultural keystone status, (3) studies that cite a paper on or that discusses the cultural keystone concept, (4) studies that review the cultural keystone species concept, and (5) studies that provide a direct test or measure of species cultural keystone status. b Publication types include (1) studies that solely mention the cultural keystone species concept, (2) studies that mention a given species as a cultural keystone species without a direct test or measure of species cultural keystone status, (3) studies that cite a paper on or that discusses the cultural keystone concept, (4) studies that review the cultural keystone species concept, and (5) studies that provide a direct test or measure of species cultural keystone status