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Conserving the Stage: Climate Change and the Geophysical Underpinnings of Species Diversity
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Conservationists have proposed methods for adapting to climate change that assume species distributions are primarily explained by climate variables. The key idea is to use the understanding of species-climate relationships to map corridors and to identify regions of faunal stability or high species turnover. An alternative approach is to adopt an evolutionary timescale and ask ultimately what factors control total diversity, so that over the long run the major drivers of total species richness can be protected. Within a single climatic region, the temperate area encompassing all of the Northeastern U.S. and Maritime Canada, we hypothesized that geologic factors may take precedence over climate in explaining diversity patterns.
If geophysical diversity does drive regional diversity, then conserving geophysical settings may offer an approach to conservation that protects diversity under both current and future climates. Here we tested how well geology predicts the species diversity of 14 US states and three Canadian provinces, using a comprehensive new spatial dataset. Results of linear regressions of species diversity on all possible combinations of 23 geophysical and climatic variables indicated that four geophysical factors; the number of geological classes, latitude, elevation range and the amount of calcareous bedrock, predicted species diversity with certainty (adj. R2 = 0.94). To confirm the species-geology relationships we ran an
independent test using 18,700 location points for 885 rare species and found that 40% of the species were restricted to a single geology. Moreover, each geology class supported 5–95 endemic species and chi-square tests confirmed that calcareous bedrock and extreme elevations had significantly more rare species than expected by chance (P,0.0001), strongly corroborating the regression model. Our results suggest that protecting geophysical settings will conserve the stage for current and future biodiversity and may be a robust alternative to species-level predictions.
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Correlations among species distributions, human density and human infrastructure across the high biodiversity tropical mountains of Africa
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This paper explores whether spatial variation in the biodiversity values of vertebrates and plants (species richness, range-size rarity and number or proportion of IUCN Red Listed threatened species) of three African tropical mountain ranges (Eastern Arc, Albertine Rift and Cameroon-Nigeria mountains within the Biafran Forests and Highlands) co-vary with proxy measures of threat (human population density and human infrastructure). We find that species richness, range-size rarity, and threatened species scores are all significantly higher in these three tropical African mountain ranges than across the rest of sub-Saharan Africa. When compared with the rest of sub-Saharan Africa, human population density is only significantly higher in the Albertine Rift mountains, whereas human infrastructure is only significantly higher in the Albertine Rift and the Cameroon-Nigeria mountains. Statistically there are strong positive correlations between human density and species richness, endemism and density or proportion of threatened species across the three tropical African mountain ranges, and all of sub-Saharan Africa. Kendall partial rank-order correlation shows that across the African tropical mountains human popula- tion density, but not human infrastructure, best correlates with biodiversity values. This is not the case across all of sub-Saharan Africa where human density and human infra- structure both correlate almost equally well with biodiversity values. The primary conser- vation challenge in the African tropical mountains is a fairly dense and poor rural population that is reliant on farming for their livelihood. Conservation strategies have o address agricultural production and expansion, in some cases across the boundaries and into existing reserves. Strategies also have to maintain, or finalise, an adequate protected area network. Such strategies cannot be implemented in conflict with the local population, but have to find ways to provide benefits to the people living adjacent to the remaining for- ested areas, in return for their assistance in conserving the forest habitats, their biodiver- sity, and their ecosystem functions. Africa Biodiversity Human infrastructure Human population Tropical mountains
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Disturbance−diversity models: what do they really predict and how are they tested?
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The intermediate disturbance hypothesis (IDH) and the dynamic equilibrium model (DEM) are influential theories in ecology. The IDH predicts large species numbers at intermediate levels of disturbance and the DEM predicts that the effect of disturbance depends on the level of productivity. However, various indices of diversity are considered more commonly than the predicted number of species in tests of the hypotheses. This issue reaches beyond the scientific community as the predictions of the IDH and the DEM are used in the management of national parks and reserves. In order to compare responses with disturbance among measures of biodiversity, we used two different approaches of mathematical modelling and conducted an extensive meta-analysis. Two-thirds of the surveyed studies present different results for different diversity measures. Accordingly, the meta-analysis showed a narrow range of negative quadratic regression components for richness, but not evenness. Also, the two models support the IDH and the DEM, respectively, when biodiversity is measured as species richness, but predict evenness to increase with increasing disturbance, for all levels of productivity. Consequently, studies that use compound indices of diversity should present logical arguments, a priori, to why a specific index of diversity should peak in response to disturbance.
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Ecological and Evolutionary Responses to Recent Climate Change
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Ecological changes in the phenology and distribution of plants and animals are occurring in all well-studied marine, freshwater, and terrestrial groups. These observed changes are heavily biased in the directions predicted from global warming and have been linked to local or regional climate change through correlations between climate and biological variation, field and laboratory experiments, and physiological research. Range-restricted species, particularly polar and mountaintop species, show severe range contractions and have been the first groups in which entire species have gone extinct due to recent climate change. Tropical coral reefs and amphibians have been most negatively affected. Predator-prey and plant-insect interactions have been disrupted when interacting species have responded differently to warming. Evolutionary adaptations to warmer conditions have occurred in the interiors of species’ ranges, and resource use and dispersal have evolved rapidly at expanding range margins. Observed genetic shifts modulate local effects of climate change, but there is little evidence that they will mitigate negative effects at the species level.
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Ecological responses to recent climate change
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There is now ample evidence of the ecological impacts of recent climate change, from polar terrestrial to tropical marine environments. The responses of both flora and fauna span an array of ecosystems and organizational hierarchies, from the species to the community levels. Despite continued uncertainty as to community and ecosystem trajectories under global change, our review exposes a coherent pattern of ecological change across systems. Although we are only at an early stage in the projected trends of global warming, ecological responses to recent climate change are already clearly visible.
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EDDMapS: Early Detection and Distribution Mapping System
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EDDMapS is a web-based mapping system for documenting invasive species and pest distribution. It is fast, easy to use, and doesn't require GIS experience. Launched in 2005 by the Center for Invasive Species and Ecosystem Health at the University of Georgia, it was originally designed as a tool for state Exotic Pest Plant Councils to develop more complete distribution data of invasive species. Since then, the program has expanded to include the entire US and Canada as well as to document certain native pest species. EDDMapS' goal is to maximize the effectiveness and accessibility of the immense numbers of invasive species and pest observations recorded each year. As of June 2021, EDDMapS has over 5.2 million records.
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Energetic and biomechanical constraints on animal migration distance
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Animal migration is one of the great wonders of nature, but the factors that determine how far migrants travel remain poorly understood. We present a new quantitative model of animal migration and use it to describe the maximum migration distance of walking, swimming and flying migrants. The model combines biomechanics and metabolic scaling to show how maximum migration distance is constrained by body size for each mode of travel. The model also indicates that the number of body lengths travelled by walking and swimming migrants should be approximately invariant of body size. Data from over 200 species of migratory birds, mammals, fish, and invertebrates support the central conclusion of the model – that body size drives variation in maximum migration distance among species through its effects on metabolism and the cost of locomotion. The model provides a new tool to enhance general understanding of the ecology and evolution of migration.
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Evolution of climate niches in European mammals?
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Our ability to predict consequences of climate change is severely impaired by the lack of knowledge on the ability of species to adapt to changing environmental conditions. We used distribution data for 140 mammal species in Europe, together with data on climate, land cover and topography, to derive a statistical description of their realized climate niche. We then compared climate niche overlap of pairs of species, selected on the basis of phylogenetic information. In contrast to expectations, related species were not similar in their climate niche. Rather, even species pairs that had a common ancestor less than 1Ma already display very high climate niche distances. We interpret our finding as a strong inter- specific competitive constraint on the realized niche, rather than a rapid evolution of the fundamental niche. If correct, our results imply a very limited usefulness of climate niche models for the prediction of future mammal distributions.
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Extreme climatic event drives range contraction of a habitat-forming species
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Species distributions have shifted in response to global warming in all major ecosystems on the Earth. Despite cogent evidence for these changes, the underlying mechanisms are poorly understood and currently imply gradual shifts. Yet there is an increasing appreciation of the role of discrete events in driving ecological change. We show how a marine heat wave (HW) eliminated a prominent habitat-forming seaweed, Scytothalia dorycarpa, at its warm distribution limit, causing a range contraction of approximately 100km (approx. 5% of its global distribution). Seawater temperatures during the HW exceeded the seaweed’s physiological threshold and caused extirpation of marginal populations, which are unlikely to recover owing to life-history traits and oceanographic processes. Scytothalia dorycarpa is an important canopy-forming seaweed in temperate Australia, and loss of the species at its range edge has caused structural changes at the community level and is likely to have ecosystem-level implications. We show that extreme warming events, which are increasing in magnitude and frequency, can force step-wise changes in species distributions in marine ecosystems. As such, return times of these events have major implications for projections of species distributions and ecosystem structure, which have typically been based on gradual warming trends.
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Protected areas in Borneo may fail to conserve tropical forest biodiversity under climate change
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Protected areas (PAs) are key for conserving rainforest species, but many PAs are becoming increasingly
isolated within agricultural landscapes, which may have detrimental consequences for the forest biota
they contain. We examined the vulnerability of PA networks to climate change by examining connectivity
of PAs along elevation gradients. We used the PA network on Borneo as a model system, and examined
changes in the spatial distribution of climate conditions in future. A large proportion of PAs will not
contain analogous climates in future (based on temperature projections for 2061–2080), potentially
requiring organisms to move to cooler PAs at higher elevation, if they are to track climate changes. For
the highest warming scenario (RCP8.5), few (11–12.5%; 27–30/240) PAs were sufficiently topographically
diverse for analogous climate conditions (present-day equivalent or cooler) to remain in situ. For the
remaining 87.5–89% (210–213/240) of PAs, which were often situated at low elevation, analogous climate
will only be available in higher elevation PAs. However, over half (60–82%) of all PAs on Borneo are too
isolated for poor dispersers (<1 km per generation) to reach cooler PAs, because there is a lack of connecting
forest habitat. Even under the lowest warming scenario (RCP2.6), analogous climate conditions will
disappear from 61% (146/240) of PAs, and a large proportion of these are too isolated for poor dispersers
to reach cooler PAs. Our results suggest that low elevation PAs are particularly vulnerable to climate
change, and management to improve linkage of PAs along elevation gradients should be a conservation
priority
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