Floral traits variation in Oenothera drummondii subsp. drummondii across a wide latitudinal range of native and non-native populations.
Plant species with specialized pollination and wide geographic distribution can show variation in the size of floral traits related to environmental local conditions. We studied the floral traits of native and non-native populations of Oenothera drummondii under greenhouse conditions to test if their variation is related to latitude, or their native or non-native origin but displaying similar floral integration. Plants were obtained from seeds collected in six native and six non-native populations distributed across five continents. Eight floral traits were recorded in the flowers produced and examined across latitudinal variation between native and non-native ranges. The floral traits differed between the native and non-native populations, with corolla size the main contributor. Although each floral feature varied independently in response to the latitude and environmental conditions of the populations, there is a clear tendency for size reduction of the structures with latitudinal increase. In contrast, floral integration and flower lifetime remained similar across latitude. The floral traits variation of O. drummondii throughout its native and non-native distribution is the result of the latitudinal gradient and the local population environment. The similarity in floral integration and flower lifespan may favor the specialized reproduction in native populations, whereas flower size-reduction suggests potential local adaptation for pollinators in the non-native populations. The study of flower visitors will help to understand the local adaptation of Oenothera drummondii in each population.