Phenological trends among Australian alpine species: using herbarium records to identify climate-change indicators

Globaltemperatures areincreasingat anunprecedentedrateandthe analysisof long-termphenological records hasprovidedsomeofthemostcompellingevidencefortheeffectofthesechangesonspecies.Inregionswheresystematically collected data on the timing of life-cycle events is scarce, such as Australia, researchers must seek alternative sources of information from which climate-change signals can be identified. In the present paper, we explore the limitations and strengthsofusingherbariumspecimenstodetectchangesin floweringphenology,toselectpotentialindicatorspecies,andto pinpoint locations for potential monitoring schemes of native plants in Australia's subalpine and alpine zone. We selected 20 species on the basis of a range of selection criteria, including a flowering duration of 3 months or less and the number of herbarium records available in the areas above 1500m. By the use of gridded temperature data within the study region, we identifiedanincreaseinmeanannualtemperatureof0.74 Cbetween1950and2007.Wethenmatchedthespatiallocationsof the herbarium specimens to these temperature data and, by using linear regression models, identified five species whose flowering response may be sensitive to temperature. Higher mean annual temperatures at the point of collection were negativelyassociatedwithearlier floweringineachofthesespecies(a=0.05).Wealsofoundasignificant(P=0.02)negative relationship between year and flowering observation for Alpine groundsel, Senecio pectinatus var. major. This species is potentially a suitable candidate for monitoring responses of species to future climate change, owing to the accessibility of populations and its conspicuous flowers. It is also likely that with ongoing warming the other four species identified (Colobanthus affinis, Ewartia nubigena, Prasophyllum tadgellianum and Wahlenbergia ceracea) in the present study may show the same response.