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Phenological trends among Australian Alpine species: Using Herbarium records to identify climate-change indicators

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Global temperatures are increasing at an unprecedented rate and the analysis of long-term phenological records has provided some of the most compelling evidence for the effect of these changes on species. In regions where systematically 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 strengths of using herbarium specimens to detect changes in flowering phenology, to select potential indicator species, and to 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 1500 m. By the use of gridded temperature data within the study region, we identified an increase in mean annual temperature of 0.74 C between 1950 and 2007. We then matched the spatial locations of 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 negatively associated with earlier flowering in each of these species (a = 0.05). We also found a significant (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.
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... However, we know much less about how southern hemisphere species, particularly plants, have responded to warming climates (Chambers et al., 2013(Chambers et al., , 2016. We currently have data for long-term flowering phenology shifts through time for just 195 of the ~21,000 (Chapman, 2009) flowering plant species in Australia (Gallagher et al., 2009;Keatley et al., 2004;Keatley & Hudson, 2007;Rawal et al., 2014;Rumpff et al., 2010). These data come from just five studies in four different ecosystems (alpine, Eucalypt woodland, sclerophyll woodland and coastal vegetation). ...
... These data come from just five studies in four different ecosystems (alpine, Eucalypt woodland, sclerophyll woodland and coastal vegetation). These studies in the southern hemisphere show relatively few species advancing their flowering and some species delaying their flowering (Gallagher et al., 2009;Rumpff et al., 2010). The present study complements these existing studies by providing new data for 37 species from 19 families from sclerophyll woodland in northern Sydney, testing the hypothesis that Australian species have shifted to earlier flowering times over the last 177 years. ...
... Differences in both the rate of warming (Friedman et al., 2013) and the taxa (Box, 2002;Sanmartín & Ronquist, 2004) between the two hemispheres could drive differences in responses between northern and southern hemisphere species. Studies in the southern hemisphere have found limited shifts in species' flowering phenology (Gallagher et al., 2009;Rumpff et al., 2010), and we hypothesised that species may be less likely to show shifts in flowering timing than northern hemispheric species. Thus, our final aim was to determine whether a lower proportion of species have advanced their flowering phenology in the southern hemisphere than in the northern hemisphere. ...
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Shifts in flowering phenology have been studied in detail in the northern hemisphere and are a key plant response to climate change. However, there are relatively fewer data on species’ phenological shifts in the southern hemisphere. We combined historic field data, data from herbarium specimens dating back to 1842, and modern field data for 37 Australian species to determine whether species were flowering earlier in the year than they had in the past. We also combined our results with data compiled in the southern and northern hemispheres respectively, to determine if southern hemisphere species are showing fewer advances in flowering phenology through time. Across our study species, we found that 12 species had undergone significant shifts in flowering time, with four species advancing their flowering and eight species delaying their flowering. The remaining 25 species showed no significant shifts in their flowering phenology. These findings are important because delays or lack of shifts in flowering phenology can lead to mismatches in trophic interactions between plants and pollinators or seed dispersers, which can have substantial impacts on ecosystem functioning and primary productivity. Combining our field results with data compiled from the literature showed that only 58.5% of southern hemisphere species were advancing their flowering time, compared with 81.6% of species that were advancing their flowering time in the northern hemisphere. Our study provides further evidence that it is not adequate for ecologists to assume that southern hemisphere ecosystems will respond to future climate change in the same way as ecosystems north of the Equator. Synthesis. Field data and data from the literature indicate that southern hemisphere species are showing fewer advances in their flowering phenology through time, especially in comparison to northern hemisphere species.
... Australia's montane biome covers a small proportion of the country's terrestrial surface area (~0.16%, Figure 1) and is a centre of floral endemism in Australia (Crisp et al., 2001). (Gallagher et al., 2009;Green, 2010). ...
... Thus, one would expect greater climate-induced changes in the currently concentrated community flowering periods of Australian Montane or Temperate Forest communities, as they shift towards the longer, more responsive flowering periods of Desert communities (Figure 3). There are already reports that lower and less predictable rainfall is affecting plant community composition through dieback in southwest Australia (Hoffmann et al., 2019), and that higher temperatures are shifting flowering dates in alpine southeast Australia (Gallagher et al., 2009;Hoffmann et al., 2019). ...
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Climate shapes the composition and function of plant communities globally, but it remains unclear how this influence extends to floral traits. Flowering phenology, or the time period in which a species flowers, has well‐studied relationships with climatic signals at the species level but has rarely been explored at a cross‐community and continental scale. Here, we characterise the distribution of flowering periods (months of flowering) across continental plant communities encompassing six biomes, and determine the influence of climate on community flowering period lengths. Australia. Flowering plants. We combined plant composition and abundance data from 629 standardised floristic surveys (AusPlots) with data on flowering period from the AusTraits database and additional primary literature for 2983 species. We assessed abundance‐weighted community mean flowering periods across biomes and tested their relationship with climatic annual means and the predictability of climate conditions using regression models. Combined, temperature and precipitation (annual mean and predictability) explain 29% of variation in continental community flowering period. Plant communities with higher mean temperatures and lower mean precipitation have longer mean flowering periods. Moreover, plant communities in climates with predictable temperatures and, to a lesser extent, predictable precipitation have shorter mean flowering periods. Flowering period varies by biome, being longest in deserts and shortest in alpine and montane communities. For instance, desert communities experience low and unpredictable precipitation and high, unpredictable temperatures and have longer mean flowering periods, with desert species typically flowering at any time of year in response to rain. Current climate conditions shape flowering periods across biomes, with implications for phenology under climate change. Shifts in flowering periods across climatic gradients reflect changes in plant strategies, affecting patterns of plant growth and reproduction as well as the availability of floral resources for pollinators across the landscape.
... niphophila at lower elevations since 1970, which may lead to downhill range shifts in this species (Green & Venn, 2012). Studies have also found changes in species composition including increased shrub cover and decreased graminoid cover with experimental warming in this region (Wahren et al., 2013); as well as observed shifts in species' phenology with a few species flowering earlier in the year than in the past (Gallagher et al., 2009) and increases in the invasion of non-native species (Scherrer & Pickering, 2001). However, our study is the first to test for elevational range shifts across a wide range of Australian alpine plant species. ...
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Aim Alpine plant species’ distributions are thought to have been shifting to higher elevations in response to climate change. By moving upslope, species can occupy cooler and more suitable environments as climate change warms their current ranges. Despite evidence of upslope migration in the northern hemisphere, there is limited evidence for elevational shifts in southern hemisphere plants. Our study aimed to determine if alpine plants in Australia have migrated upslope in the last 2 to 6 decades. Location Kosciuszko National Park, NSW, Australia. Methods We collated historic occurrence data for 36 Australian alpine plant species from herbarium specimens and historic field observations and combined these historic data with modern occurrence data collected in the field. Results Eleven of the thirty‐six species had shifted upslope in mean elevation and four species showed downslope elevational shifts. The rate of change for upslope shifts varied between 4 and 10 m per year and the rate of change for most downslope shifts was between 4 and 8 m per year, with one species shifting downslope at a high rate of 18 m per year. Additionally, some species showed shifts upward in their upper range edge and/or upward or downward shifts in their lower range edge. Five species also showed range contractions in the difference between their lower and upper range edges over time, while two showed range expansions. We found no significant differences in elevational shifts through time among herbaceous dicotyledons, herbaceous monocotyledons and shrubs. Main Conclusions Plant elevational shifts are occurring rapidly in the Australian alpine zone. This may allow species to persist under climate change. However, if current warming trends continue, several species within the Australian alpine zone will likely run out of suitable habitat within a century.
... Because most of the collections are dated and geolocated, they constitute a valuable source of information for (i) determining the proven or potential distribution areas of species [21][22][23], whether native or exotic (dynamics of biological invasions), with direct applications in conservation biology [24], and for (ii) determining the reproductive phenological patterns of species (e.g., date and duration of flowering and fruiting periods) [25][26][27][28]. Research in these fields has been particularly stimulated by questions related to climate change and its effect on the range of species distribution [29,30] or their biological rhythms [31][32][33][34][35][36][37][38][39]. More original aspects have been addressed such as changes over time in (i) herbivory [40,41], (ii) the concentration of isotopes (δC13, δO18) related to water use efficiency or photosynthetic efficiency [42], or (iii) the diversity of endophytic fungi present in leaves [43]. ...
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A better knowledge of tree vegetative growth phenology and its relationship to environmental variables is crucial to understanding forest growth dynamics and how climate change may affect it. Less studied than reproductive structures, vegetative growth phenology focuses primarily on the analysis of growing shoots, from buds to leaf fall. In temperate regions, low winter temperatures impose a cessation of vegetative growth shoots and lead to a well-known annual growth cycle pattern for most species. The humid tropics, on the other hand, have less seasonality and contain many more tree species, leading to a diversity of patterns that is still poorly known and understood. The work in this study aims to advance knowledge in this area, focusing specifically on herbarium scans, as herbariums offer the promise of tracking phenology over long periods of time. However, such a study requires a large number of shoots to be able to draw statistically relevant conclusions. We propose to investigate the extent to which the use of deep learning can help detect and type-classify these relatively rare vegetative structures in herbarium collections. Our results demonstrate the relevance of using herbarium data in vegetative phenology research as well as the potential of deep learning approaches for growing shoot detection.
... A few years later, Houle (2007) compared the flowering dates of vernal plants in deciduous forests in Quebec and found that they flowered two to six days earlier at the end of the 20th century than at the beginning. More recently, a study in the Australian mountains used herbarium samples to identify alpine (Australian) species whose altered phenology may reflect climate change (Gallagher et al. 2009). ...
... A few years later, Houle (2007) compared the flowering dates of vernal plants in deciduous forests in Quebec and found that they flowered two to six days earlier at the end of the 20th century than at the beginning. More recently, a study in the Australian mountains used herbarium samples to identify alpine (Australian) species whose altered phenology may reflect climate change (Gallagher et al. 2009). ...
Chapter
Herbaria can contribute to the evaluation of the floristic knowledge of territories and to the identification of “hotspots” of plant biodiversity; to the characterization of floristic regressions of certain species; and to the study of the history of introductions and expansion of invasive exotic species or of symbionts collected unintentionally with the plant samples. Herbarium specimens can also be used to characterize environmental changes in territories such as air, water and soil quality, as well as the impacts of climate change on the phenology and possibly the morphology of plant species. This chapter repeats, completes and updates a first note on the use of herbaria in highlighting environmental change presented at the international conference Botanists of the Twenty‐first Century Roles, Challenges and Opportunities, organized by UNESCO in September 2014 and published in the proceedings of this conference.
... Quelques années plus tard, Houle (2007) a comparé les dates de floraison des plantes vernales des forêts décidues du Québec et mis en évidence une floraison plus précoce de 2-6 jours à la fin du XX e siècle par rapport au début. Plus récemment, une étude a été réalisée dans les montagnes australiennes et a utilisé des échantillons d'herbier pour identifier des espèces de l'étage alpin (australien) dont la modification de phénologie pouvait traduire des changements climatiques (Gallagher et al. 2009). ...
Chapter
The “cyanobacteria and microalgae” collection of the Muséum national d'Histoire naturelle includes, respectively, 870 and 890 living strains maintained in the laboratory. This collection supports fundamental research, particularly in taxonomy and ecophysiology, but also numerous activities for the development of bioactive molecules and expertise in environmental diagnosis. These different activities benefit from the emergence of high‐throughput “‐omics” approaches, which now offer new possibilities to enable such a collection to respond to the current challenges of both fundamental and targeted research, and of the conservation of biological resources. The conservation of organisms in living collections allows us to explore their biological properties. Among these, the production of bioactive metabolites is a rapidly developing theme. The “cyanobacteria and microalgae” collection is a reference collection for environmental diagnosis.
... A few years later, Houle (2007) compared the flowering dates of vernal plants in deciduous forests in Quebec and found that they flowered two to six days earlier at the end of the 20th century than at the beginning. More recently, a study in the Australian mountains used herbarium samples to identify alpine (Australian) species whose altered phenology may reflect climate change (Gallagher et al. 2009). ...
Chapter
This chapter assesses the feasibility of using natural history collections to trace temporal changes in species distribution and community composition using the example of macroalgae that are preserved as herbaria. The preservation of plants in herbaria began during the Renaissance. This technique required paper and became widespread in the 18th century thanks to technical advances in paper production. Plant classifications have been developed on the basis of the diversity of forms of reproductive organs. The algal herbarium of the Dinard maritime laboratory has been recently transferred to the Herbier national du Muséum national d'Histoire naturelle de Paris in the cryptogamy section. It is possible to explore temporal changes in species distribution from collections under certain conditions, either by using only the observations or by using those observations to model species distribution. Algal community composition and species distribution are being impacted by global change and in particular by increasing seawater temperatures and heat waves.
Article
To date, most herbarium-based studies of phenological sensitivity to climate and of climate-driven phenological shifts fall into two categories: detailed species-specific studies vs. multi-species investigations designed to explain inter-specific variation in sensitivity to climate and/or the magnitude and direction of their long-term phenological shifts. Few herbarium-based studies, however, have compared the phenological responses of closely related taxa to detect: (1) phenological divergence, which may result from selection for the avoidance of heterospecific pollen transfer or competition for pollinators, or (2) phenological similarity, which may result from phylogenetic niche conservatism, parallel or convergent adaptive evolution, or genetic constraints that prevent divergence. Here, we compare two widespread Clarkia species in California with respect to: the climates that they occupy; mean flowering date, controlling for local climate; the degree and direction of climate change to which they have been exposed over the last 115 yr; the sensitivity of flowering date to inter-annual and to long-term mean maximum spring temperature and annual precipitation across their ranges; and their phenological change over time. Specimens of C. cylindrica were sampled from sites that were chronically cooler and drier than those of C. unguiculata, although their climate envelopes broadly overlapped. Clarkia cylindrica flowers 3.5 d earlier than C. unguiculata when controlling for the effects of local climatic conditions and for quantitative variation in the phenological status of specimens. However, the congeners did not differ in their sensitivities to the climatic variables examined here; cumulative annual precipitation delayed flowering and higher spring temperatures advanced flowering. In spite of significant spring warming over the sampling period, neither species exhibited a long-term phenological shift. Precipitation and spring temperature interacted to influence flowering date: the advancing effect on flowering date of high spring temperatures was greater in dry than in mesic regions, and the delaying effect of high precipitation was greater in warm than in cool regions. The similarities between these species in their phenological sensitivity and behavior are consistent with the interpretation that facilitation by pollinators and/or shared environmental conditions generate similar patterns of selection, or that limited genetic variation in flowering time prevents evolutionary divergence between these species.
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Aim Climate shapes the composition and function of plant communities globally, but it remains unclear how this influence extends to floral traits. Flowering phenology, or the time period in which a species flowers, has well-studied relationships with climatic signals at the species level but has rarely been explored at a cross-community and continental scale. Here, we characterise the distribution of flowering periods (months of flowering) across continental plant communities encompassing six biomes, and determine the influence of climate on community flowering period lengths. Location Australia Taxon Flowering plants Methods We combined plant composition and abundance data from 629 standardised floristic surveys (AusPlots) with data on flowering period from the AusTraits database and additional primary literature for 2,983 species. We assessed abundance-weighted community mean flowering periods across biomes and tested their relationship with climatic annual means and the predictability of climate conditions using regression models. Results Combined, temperature and precipitation (annual mean and predictability) explain 29% of variation in continental community flowering period. Plant communities with higher mean temperatures and lower mean precipitation have longer mean flowering periods. Moreover, plant communities in climates with predictable temperatures and, to a lesser extent, predictable precipitation have shorter mean flowering periods. Flowering period varies by biome, being longest in deserts and shortest in alpine and montane communities. For instance, desert communities experience low and unpredictable precipitation and high, unpredictable temperatures and have longer mean flowering periods, with desert species typically flowering at any time of year in response to rain. Main conclusions Our findings demonstrate the role of current climate conditions in shaping flowering periods across biomes, with implications under climate change. Shifts in flowering periods across climatic gradients reflect changes in plant strategies, affecting patterns of plant growth and reproduction as well as the availability of floral resources across the landscape.
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Information from natural history collections (NHCs) about the diversity, taxonomy and historical distributions of species worldwide is becoming increasingly available over the Internet. In light of this relatively new and rapidly increasing resource, we critically review its utility and limitations for addressing a diverse array of applications. When integrated with spatial environmental data, NHC data can be used to study a broad range of topics, from aspects of ecological and evolutionary theory, to applications in conservation, agriculture and human health. There are challenges inherent to using NHC data, such as taxonomic inaccuracies and biases in the spatial coverage of data, which require consideration. Promising research frontiers include the integration of NHC data with information from comparative genomics and phylogenetics, and stronger connections between the environmental analysis of NHC data and experimental and field-based tests of hypotheses.
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The iconic summer tourism destination in the Australian Alps National Parks is the summit area of continental Australia's highest mountain, Mt Kosciuszko. Currently 70,000 people visit the alpine area during the snow-free period each year, and about 21,000 of these take a day-walk to the summit and back. The environmental impacts of summer tourism include: soil compaction and erosion; introduction and spread of weeds; fecal contamination of lakes and creeks; increased feral animals; and vegetation clearance. The principal management responses have been: hardening of tracks; provision of toilets; education, including minimum-impact codes; and restrictions on activities such as camping in the catchment areas of glacial lakes. Currently, only the access tracks and immediate alpine area around the summit of Mt Kosciuszko receive so many visitors in such a small area. The summit area has become a honeypot focusing tourism and its impacts at one site. Effective management is needed to ensure that the summit along with the rest of the Kosciuszko alpine area remains viable for conservation and outdoor recreation.
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To examine the potential contribution of herbarium material to the description and analysis of tropical tree phenology, flowering times and geographical distribution were graphed for 1673 flowering collections from 18 species native to Neotropical dry forests and phenological differences between species were analysed. These include the timing and duration of flowering as well as morphological differences such as flowering on leafless twigs vs flowering on shoots bearing old or new foliage. Species-specific flowering periods of herbarium collections are similar to those observed in phenological field studies, but are often longer because of the larger geographical and temporal sampling range. Conspecific collections of different geographical origin show distinct differences in flowering periodicity, which are correlated with differences in the timing and intensity of the dry season. Interspecific differences in the timing of phenology relative to the dry season indicate differences in the control of phenology by seasonal drought. Herbaria thus represent a large potential source of phenological information which can either supplement and extend phenological field studies or provide phenological information for dry forest species not studied in the field but well represented in herbarium collections.