Temperature curvature was uncertain in six adjusted exposed-anther herbarium samples from 1943 to 2017

We tested whether floral UV pigment had a curved temperature response after controls for collection season and species trends. We used 934 exposed-anther specimens from Australia, Eurasia and North America, split at 1985. Each model allowed a separate linear temperature slope for each species. All six species-cluster intervals for the shared quadratic term included zero after six-test correction. Estimates ranged from -5.79 to +0.18 percentage points per C squared. Only 2-17 specimens supplied half of the remaining quadratic exposure information in each sample. Equal-species weights, a transformed response and common linear slopes also gave uncertain curvature. The early Australian fit had only ten residual degrees of freedom. These records do not establish a thermal optimum or its absence. Nonrandom collection, few species, uncertain source exposures and one archive limit inference. This is a new model contrast on previously studied records, not independent confirmation. The package includes code, a panel, exact source hashes, numeric checks and retrieval instructions. It tests no surface air pollutant or weather extreme.

floral pigmentation · temperature curvature · herbarium · observation bias · species slopes · regional replication · null result