Plant species with larger extrafloral nectaries produce better quality nectar only when needed and favour interactions with best ant partners

The research was carried out in a seasonally dry tropical forest area in the Caatinga domain, Vale do Curu Experimental Farm (3º48'43''S and 39º20'42''W, 80 m asl), municipality of Pentecoste, State of Ceará, Brazil. Three species of Chamaecrista native to the Brazilian northeastern semiarid region were selected: Chamaecrista diphylla (L.) (Fig. 1I-L); Chamaecrista duckeana (P. Bezerra & Afr. Fern.) H. S. Irwin & Barneby (Fig. 1M-R) and Chamaecrista calycioides (DC. ex Collad.) Greene. Field collection on the three Chamaecrista species was carried out between January and June of 2020.