Other papers consider the adaptive significance of various floral features, such as flower lifespan, flower size dimorphisms, deceitfully nectarless flowers and heterostyly
. The approaches are diverse, ranging from careful observation and measurement as in Barrett et al.'s study of Narcissus heterostyly
, to the elegant field experiments of Schemske et al., to the use of electrophoretic markers in artificial arrays of plants by Snow et al., to the comparative and/or phylogenetic approach of Delph and Armbruster, to the mathematical models grounded in field work of Ashman and Schoen and of Harder and Barrett.