1. Agostinelli C, Lund U (2017) R package “circular”: Circular Statistics (version 0.4–93). URL https://r-forge.r-project.org/projects/circular/. CA: Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University, Venice, Italy. UL: Department of Statistics, California Polytechnic State University, San Luis Obispo, California, US
2. Alexandersson R, Johnson SD (2002) Pollinator–mediated selection on flower–tube length in a hawkmoth–pollinated Gladiolus (Iridaceae). Proc R Soc Lond B Biol Sci 269:631–636
3. Armbruster WS (1990) Estimating and testing the shapes of adaptive surfaces: the morphology and pollination of dalechampia blossoms. Am Nat 135:14–31
4. Armbruster WS, Pélabon C, Hansen TF, Mulder CPH (2004) Floral integration, modularity, and accuracy: distinguishing complex adaptations from genetic constraints. In: Pigliucci M, Preston K (eds) Phenotypic integration: studying the ecology and evolution of complex phenotypes. Oxford University Press, Oxford, UK, pp 23–49
5. Armbruster WS, Hansen TF, Pelabon C, Perez-Barrales R, Maad J (2009a) The adaptive accuracy of flowers: measurement and microevolutionary patterns. Ann Bot 103:1529–1545