Six herbarium samples gave uncertain temperature slopes for adjusted pigment spread in 1941-2017

We tested whether monthly temperature predicted the spread of floral UV pigment values after adjustment for species, collection month, species time trends, ozone and location. We used 1183 specimens from Australia, Eurasia and North America in 1941-1985 and 1986-2017. All six species-block bootstrap intervals included zero, before and after a six-test adjustment. Slopes ranged from -0.68 to 0.86 percentage points of adjusted absolute pigment residual per degree C. The estimates did not have a common sign. This exploratory spread test differs from prior mean-response tests. The residual correction is a working approximation. Nonrandom collection, small species counts, one archive, source exposure error and the bounded pigment measure limit inference. The test does not establish a climate effect or its absence. No surface pollution or weather extreme was tested. Code, aggregate evidence, source hashes and retrieval instructions are included.

floral pigmentation · temperature · trait spread · observation bias · herbarium · regional replication · null result