Climate Relicts: Past, Present, Future Hampe, Arndt; Jump, Alistair S
Annual review of ecology, evolution, and systematics,
01/2011, Letnik:
42, Številka:
1
Journal Article
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Odprti dostop
Populations left behind during climate-driven range shifts can persist in enclaves of benign environmental conditions within an inhospitable regional climate. Such climate relicts exist in numerous ...plant and animal species worldwide, yet our knowledge of them is fragmented and lacks a general framework. Here we synthesize the empirical evidence considering (
a
) relict habitats, (
b
) abiotic and biotic constraints on population dynamics, (
c
) mechanisms promoting population persistence, and (
d
) uncertainties concerning their future prospects. We identify three major types of climate relicts: (
a
) those constrained primarily by climate-driven abiotic factors, (
b
) those restricted to areas that are inaccessible to antagonistic species for climatic reasons, and (
c
) those requiring a host or mutualistic species that is itself limited by climate. Understanding the formation and functioning of climate relicts is essential for their conservation and for our understanding of the response of species and populations to climate change.
Forest microclimates contrast strongly with the climate outside forests. To fully understand and better predict how forests' biodiversity and functions relate to climate and climate change, ...microclimates need to be integrated into ecological research. Despite the potentially broad impact of microclimates on the response of forest ecosystems to global change, our understanding of how microclimates within and below tree canopies modulate biotic responses to global change at the species, community and ecosystem level is still limited. Here, we review how spatial and temporal variation in forest microclimates result from an interplay of forest features, local water balance, topography and landscape composition. We first stress and exemplify the importance of considering forest microclimates to understand variation in biodiversity and ecosystem functions across forest landscapes. Next, we explain how macroclimate warming (of the free atmosphere) can affect microclimates, and vice versa, via interactions with land‐use changes across different biomes. Finally, we perform a priority ranking of future research avenues at the interface of microclimate ecology and global change biology, with a specific focus on three key themes: (1) disentangling the abiotic and biotic drivers and feedbacks of forest microclimates; (2) global and regional mapping and predictions of forest microclimates; and (3) the impacts of microclimate on forest biodiversity and ecosystem functioning in the face of climate change. The availability of microclimatic data will significantly increase in the coming decades, characterizing climate variability at unprecedented spatial and temporal scales relevant to biological processes in forests. This will revolutionize our understanding of the dynamics, drivers and implications of forest microclimates on biodiversity and ecological functions, and the impacts of global changes. In order to support the sustainable use of forests and to secure their biodiversity and ecosystem services for future generations, microclimates cannot be ignored.
Below‐canopy forest microclimates contrast strongly with the climate outside forests due to the presence of trees and shrubs. Here we review the drivers and the importance of forest microclimates in the face of climate change, and perform a priority ranking of future research avenues.
The surface of plant leaves, or the phyllosphere, harbors hyperdiverse microbial communities. These communities mediate foliar functional traits, influence plant fitness, and contribute to several ...ecosystem functions, including nutrient and water cycling. In this review, we briefly recall the history of phyllosphere research and present the features of this microbial habitat. Adopting a recent framework for evolutionary community ecology, we then review evidence for each of the four major processes shaping phyllosphere microbial communities: dispersal, evolutionary diversification, selection, and drift. We show how these processes are influenced by the host plant, the surrounding atmospheric conditions, and microbial interactions. Rapidly growing evidence indicates that phyllosphere microbial communities are altered by global change, with potential cascading effects on plant performance, plant evolution, and ecosystem functioning. We propose future avenues for phyllosphere research aimed at improving plant adaptation and ecosystem resilience to environmental changes.
Modern climate change is producing poleward range shifts of numerous taxa, communities and ecosystems worldwide. The response of species to changing environments is likely to be determined largely by ...population responses at range margins. In contrast to the expanding edge, the low‐latitude limit (rear edge) of species ranges remains understudied, and the critical importance of rear edge populations as long‐term stores of species’ genetic diversity and foci of speciation has been little acknowledged. We review recent findings from the fossil record, phylogeography and ecology to illustrate that rear edge populations are often disproportionately important for the survival and evolution of biota. Their ecological features, dynamics and conservation requirements differ from those of populations in other parts of the range, and some commonly recommended conservation practices might therefore be of little use or even counterproductive for rear edge populations.
Trees do not form a natural group but share attributes such as great size, longevity, and high reproductive output that affect their mode and tempo of evolution. In particular, trees are unique in ...that they maintain high levels of diversity while accumulating new mutations only slowly. They are also capable of rapid local adaptation and can evolve quickly from nontree ancestors, but most existing tree lineages typically experience low speciation and extinction rates. We discuss why the tree growth habit should lead to these seemingly paradoxical features.
•We investigated mating system and pollen dispersal of a refugial beech population.•Most mating occurred between neighbouring trees.•Strong spatial genetic structure indicated that these are ...sibs.•Such a behaviour is very rare in wind-pollinated forest trees.•It has important implications for the conservation of forest genetic resources.
Many temperate and boreal tree species have small and scattered populations near the low-latitude margins of their range that have persisted over extended periods of time in microrefugia. It remains poorly understood how patterns of mating and gene flow influence key components for their long-term persistence such as effective population size or genetic diversity. Yet such information is critical for designing effective protection measures and informing programs for the conservation of forest genetic resources.
Here we investigate the mating system and pollen dispersal of a long-term refugial population of beech (Fagus sylvatica), a major European forest tree. This population stretches over ca. 7km along the ravines of a small lowland river in SW France. We exhaustively mapped the adult population (n=932 trees) and collected seed families (n=450 seeds) from 30mother trees spread across the stand. All individuals were genotyped at 113 SNP markers and submitted to paternity analyses. We estimated various mating parameters and tested whether among-individual variation was related with the ecological neighbourhood of the mother tree.
A unique father could be identified for all seeds analysed. We detected neither pollen immigration nor selfing events. Instead, we observed extensive mating between neighbouring trees that resulted in a very steep decline of the pollen dispersal kernel and a low effective number of fathers (median Nep=7.9). In turn, male fecundity was tightly related with the distance between mates. The adult population showed an exceptionally strong and far-reaching spatial genetic structure indicating that neighbouring trees are most often sibs. The predominant mating between these neighbours suggests that patterns of reproduction and pollen flow are not constrained by cross-compatibility issues. Instead, dense conspecific neighbourhoods even tend to bar long-distance pollen flow by saturating the stigmas of mother trees through pollen swamping. The observed patterns are a direct consequence of the refugial habitat that imposes the population’s linear distribution and whose dense vegetation represents a further obstacle to pollen dispersal. The elevated capacity of sib-mating might be a microevolutionary consequence of the population’s long-term persistence in isolation. The resulting spatial genetic structure and the critical role of tree density in assuring an effective reproduction have important consequences for the design of forest genetic resources programs as well as for the conservation management of refugial and other riparian tree populations.
Key message
Analyses of dendrochronological data from 15 recently established tablished stands of pedunculate oak (
Quercus robur
L.) revealed that functions describing potential tree growth in the ...absence of neighbours varied more between stands than functions describing competitive effects of conspecific neighbours. This suggests that competition functions can more easily be transferred among stands than potential growth functions.
Context
The variability inherent in the natural establishment of tree stands raises the question whether one can find general models for potential growth and competition that hold across stands.
Aims
We investigated variation in potential growth and competition among recently established stands of
Q. robur
and tested whether this variation depends on stand structure. We also tested whether competition is symmetric or asymmetric and whether it is density-dependent or size-dependent. Lastly, we examined whether between-year growth variation is synchronous among stands.
Methods
Potential growth, competition and between-year growth variation were quantified with statistical neighbourhood models. Model parameters were estimated separately for each stand using exhaustive mapping and dendrochronology data.
Results
Competition was best described with an asymmetric size-dependent model. Functions describing potential growth varied more among forest stands than competition functions. Parameters determining these functions could not be explained by stand structure. Moreover, annual growth rates showed only moderate synchrony across stands.
Conclusion
The substantial between-stand variability in potential growth needs to be considered when assessing the functioning, ecosystem services and management of recently established
Q. robur
stands. In contrast, the relative constancy of competition functions should facilitate their extrapolation across stands.
Key message
Few studies have linked the origin of dispersed tree seeds with their post-dispersal fate. We show that habitat-dependent mortality in a pedunculate oak (
Quercus robur
L.) seedling ...cohort reshapes the effective fecundity of individual mother trees but has little effect on the cohort’s genetic diversity.
Context
Initial tree recruitment plays a key role in forest regeneration, yet little is known on how patterns of recruit mortality feed back on the fecundity of reproducing trees.
Aims
To investigate how among-habitat variation in seedling arrival and survival alters initial patterns of genetic diversity and maternal reproductive success.
Methods
We genotyped a pedunculate oak seedling cohort (
n
= 809) and monitored it over 3 years. The mother trees of 81% of the seedlings were identified through parentage analysis. Seedlings were assigned to one of three habitats (broadleaved forest, pine plantation, or open area).
Results
Broadleaved forest received most seedlings (≈ 65%) but their survival was reduced by a third compared with pine plantations or open areas. Thus, mother trees dispersing many descendants to broadleaved forest suffered a disproportionate reduction of their reproductive success. Genetic diversity did not vary among habitats, nor over the monitoring period.
Conclusion
The quality of seed dispersal, in terms of delivery sites, can considerably influence the reproductive success of individual mother trees without affecting the overall genetic diversity of the recruits.
•
Key message
This special issue gathers articles arising from the ERA-NET BiodivERsA3 research project “Unraveling the Potential of Spontaneous Forest Establishment for Improving Ecosystem Functions ...and Services in Dynamic Landscapes (SPONFOREST)”. Using a broad spectrum of research approaches, they provide detailed insights into how new forest stands establish and which consequences the establishment process has for their character and functioning.
CONTENTS: 38 I. 38 II. Approaches for reconstructing refugia: strengths, limitations and recent advances 39 III. 46 IV. 47 V. 48 VI. 49 49 References 49 SUMMARY: Climate refugia, locations where taxa ...survive periods of regionally adverse climate, are thought to be critical for maintaining biodiversity through the glacial–interglacial climate changes of the Quaternary. A critical research need is to better integrate and reconcile the three major lines of evidence used to infer the existence of past refugia – fossil records, species distribution models and phylogeographic surveys – in order to characterize the complex spatiotemporal trajectories of species and populations in and out of refugia. Here we review the complementary strengths, limitations and new advances for these three approaches. We provide case studies to illustrate their combined application, and point the way towards new opportunities for synthesizing these disparate lines of evidence. Case studies with European beech, Qinghai spruce and Douglas‐fir illustrate how the combination of these three approaches successfully resolves complex species histories not attainable from any one approach. Promising new statistical techniques can capitalize on the strengths of each method and provide a robust quantitative reconstruction of species history. Studying past refugia can help identify contemporary refugia and clarify their conservation significance, in particular by elucidating the fine‐scale processes and the particular geographic locations that buffer species against rapidly changing climate.
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