title: Geographic mosaic of plant evolution: extrafloral nectary variation mediated by ant and herbivore assemblages.
abstract: Herbivory is an ecological process that is known to generate different patterns of selection on defensive plant traits across populations. Studies on this topic could greatly benefit from the general framework of the Geographic Mosaic Theory of Coevolution (GMT). Here, we hypothesize that herbivory represents a strong pressure for extrafloral nectary (EFN) bearing plants, with differences in herbivore and ant visitor assemblages leading to different evolutionary pressures among localities and ultimately to differences in EFN abundance and function. In this study, we investigate this hypothesis by analyzing 10 populations of Anemopaegma album (30 individuals per population) distributed through ca. 600 km of Neotropical savanna and covering most of the geographic range of this plant species. A common garden experiment revealed a phenotypic differentiation in EFN abundance, in which field and experimental plants showed a similar pattern of EFN variation among populations. We also did not find significant correlations between EFN traits and ant abundance, herbivory and plant performance across localities. Instead, a more complex pattern of ant-EFN variation, a geographic mosaic, emerged throughout the geographical range of A. album. We modeled the functional relationship between EFNs and ant traits across ant species and extended this phenotypic interface to characterize local situations of phenotypic matching and mismatching at the population level. Two distinct types of phenotypic matching emerged throughout populations: (1) a population with smaller ants (Crematogaster crinosa) matched with low abundance of EFNs; and (2) seven populations with bigger ants (Camponotus species) matched with higher EFN abundances. Three matched populations showed the highest plant performance and narrower variance of EFN abundance, representing potential plant evolutionary hotspots. Cases of mismatched and matched populations with the lowest performance were associated with abundant and highly detrimental herbivores. Our findings provide insights on the ecology and evolution of plant-ant guarding systems, and suggest new directions to research on facultative mutualistic interactions at wide geographic scales.
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Anselmo
authors.initials: A
authors.lastname: Nogueira
authors.affiliation: Departamento de Biología Animal, Biología Vegetal y Ecología, Facultad de Ciencias Experimentales, Universidad de Jaén, Jaén, Andalucia, Spain.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Rey
authors.affiliation: Departamento de Biología Animal, Biología Vegetal y Ecología, Facultad de Ciencias Experimentales, Universidad de Jaén, Jaén, Andalucia, Spain.
authors.forename: Julio M
authors.initials: JM
authors.lastname: Alcántara
authors.affiliation: Departamento de Zoologia, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba, Paraná, Brazil.
authors.forename: Rodrigo M
authors.initials: RM
authors.lastname: Feitosa
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Lúcia G
authors.initials: LG
authors.lastname: Lohmann
mesh_terms: D000818:Animals; D001000:Ants; D029402:Bignoniaceae; D005075:Biological Evolution; D060434:Herbivory; D010641:Phenotype; D057048:Plant Nectar; D013559:Symbiosis
chemical_list: D057048:Plant Nectar