Specimen‐tailored ‘lived’ climate reveals precipitation onset and amount best predict specimen phenology, but only weakly predict estimated reproduction across a clade

Herbarium specimens are widely distributed in space and time, thereby capturing diverse conditions. We reconstructed specimen 'lived' climate from knowledge of germination cues and collection dates for 14 annual species in the Streptanthus (s.l.) clade (Brassicaceae) to ask: which climate attributes best explain specimen phenological stage and estimated reproduction? Are climate effects on phenology and reproduction evolutionarily conserved? We used climate data geolocated to collection sites to reconstruct the climate experienced by specimens and to ask which aspects of climate best explain specimen reproductive traits. We mapped slopes of climate relationships with these traits on the phylogeny to explore evolutionary constraint and models of evolution. Precipitation amount and onset, more than temperature, best predicted specimen phenology, but weakly predicted reproduction. Earlier rainfall was associated with more phenological advancement, a relationship that showed phylogenetic signal. Few climate predictors explained specimen reproduction. Phenological compensation, interactions with other species, or challenges in estimating total reproduction from specimens may reduce the signal between climate and reproduction. We highlight the value of specimen-tailored growing season estimates for reconstructing climate, incorporating evolutionary relationships in assessing responses to climate. We propose supplemental collection protocols to increase the utility of specimens for understanding climate impacts.