Long-term Climate Stability Research Articles

Managing the Global Wetland Methane-Climate Feedback: A Review of Potential Options.

Methane emissions by global wetlands are anticipated to increase due to climate warming. The increase in methane represents a sizable emissions source (32-68 Tg CH4 year-1 greater in 2099 than 2010, for RCP2.6-4.5) that threatens long-term climate stability and poses a significant positive feedback that magnifies climate warming. However, management of this feedback, which is ultimately driven by human-caused warming and thus "indirectly" anthropogenic, has been largely unexplored. Here, we review the known range of options for direct management of rising wetland methane emissions, outline contexts for their application, and explore a global scale thought experiment to gauge their potential impact. Among potential management options for methane emissions from wetlands, substrate amendments, particularly sulfate, are the most well studied, although the majority have only been tested in laboratory settings and without considering potential environmental externalities. Using published models, we find that the bulk (64%-80%) of additional wetland methane will arise from hotspots making up only about 8% of global wetland extent, primarily occurring in the tropics and subtropics. If applied to these hotspots, sulfate might suppress 10%-21% of the total additional wetland methane emissions, but this treatment comes with considerable negative consequences for the environment. This thought experiment leverages results from experimental simulations of sulfate from acid rain, as there is essentially no research on the use of sulfate for intentional suppression of additional wetland methane emissions. Given the magnitude of the potential climate forcing feedback of methane from wetlands, it is critical to explore management options and their impacts to ensure that decisions made to directly manage-or not manage-this process be made with the best available science.

Sensitive response of erosion and weathering to the Indian Summer Monsoon changes in South Asia during Dansgaard-Oeschger oscillations

Continental weathering plays a key role in regulating the long-term climate stability via negative feedback. However, whether and how erosion and weathering respond to rapid climate change (e.g millennial scale) in large river basins remains unclear, partly due to the lack of archives with robust age models and high sampling resolution. As one of the largest sediment source-to-sink systems, the Himalaya-Ganga/Brahmaputra River-Bay of Bengal system is considered as an ideal laboratory for examining the weathering-climate relationships over the past. Here we present the elemental and mineralogical data from well age-constrained core sediments in the Bay of Bengal, which document the erosion and weathering conditions in South Asia during the last glacial period. All proxies generally show larger values during glacial interstadials than the stadials, consistent with the millennial variabilities of regional sea surface temperature (SST) and the Indian Summer Monsoon (ISM) strength. We confirm that the erosion and chemical weathering signals in Ganga/Brahmaputra River basins, which sensitively respond to the ISM strength and/or temperature change, could be propagated through the large river systems and faithfully preserved in the South Asian marginal seas, without noticeable time lag on a millennial scale. Our findings provide valuable data for response of erosion and weathering dynamics in a large river basin to rapid climate changes, and highlight the immense potential of monsoon-driven continental silicate weathering in floodplains as a substantial short-term carbon sink, thus underscoring a pivotal natural carbon sequestration mechanism amidst the escalating threat of global warming.

Long-term climatic stability drives accumulation and maintenance of divergent freshwater fish lineages in a temperate biodiversity hotspot

Anthropogenic climate change is forecast to drive regional climate disruption and instability across the globe. These impacts are likely to be exacerbated within biodiversity hotspots, both due to the greater potential for species loss but also to the possibility that endemic lineages might not have experienced significant climatic variation in the past, limiting their evolutionary potential to respond to rapid climate change. We assessed the role of climatic stability on the accumulation and persistence of lineages in an obligate freshwater fish group endemic to the southwest Western Australia (SWWA) biodiversity hotspot. Using 19,426 genomic (ddRAD-seq) markers and species distribution modelling, we explored the phylogeographic history of western (Nannoperca vittata) and little (Nannoperca pygmaea) pygmy perches, assessing population divergence and phylogenetic relationships, delimiting species and estimating changes in species distributions from the Pliocene to 2100. We identified two deep phylogroups comprising three divergent clusters, which showed no historical connectivity since the Pliocene. We conservatively suggest these represent three isolated species with additional intraspecific structure within one widespread species. All lineages showed long-term patterns of isolation and persistence owing to climatic stability but with significant range contractions likely under future climate change. Our results highlighted the role of climatic stability in allowing the persistence of isolated lineages in the SWWA. This biodiversity hotspot is under compounding threat from ongoing climate change and habitat modification, which may further threaten previously undetected cryptic diversity across the region.

Quantitative evaluation of the drivers of species richness in a Mediterranean ecosystem (Cape, South Africa).

Mediterranean ecosystems have a high vascular plant species richness (SR) relative to their surface area. This SR, representing the balance between speciation and extinction, has been attributed to multiple mechanisms that result in both high rates of speciation and/or low rates of extinction. An abiding question is, however, what is special about Mediterranean ecosystems that enables this high SR? Apart from the long-term climatic stability of the region, SR has also been related to resource availability, the many individuals hypothesis, resource spatial heterogeneity, temporal heterogeneity and biotic feedbacks. Spatial patterns of species richness were related to climatic, edaphic and biotic variables and to spatial variability within the Greater Cape Floristic Region (GCFR) of South Africa. Boosted regression tree models were used to explore the strength of relationships between SR and environmental predictors related to each hypothesized mechanism. Water availability (i.e. precipitation) was a stronger predictor of SR than potential evapotranspiration or temperature. Scarcity of nutrients was also related to SR. There was no indication that SR was related to the density of individuals and only temporal heterogeneity induced by fire was related to SR. Spatial heterogeneities of climatic, edaphic and biotic variables were strongly associated with SR. Biotic interactions remain difficult to assess, although we have some evidence for a putative role in regulating SR. While the lack of ecosystem-resetting disturbances (e.g. glaciation) is undoubtedly a key requirement for high species accumulation, predictably, no one explanation holds the key to understanding SR. In the GCFR high SR is the product of a combination of adequate water, nutrient scarcity, spatial and temporal heterogeneity, and possibly biotic feedbacks.

Impact of the climatic changes in the Pliocene-Pleistocene transition on Irano-Turanian species. The radiation of genus Jurinea (Compositae)

The Irano-Turanian region is one of the world’s richest floristic regions and the centre of diversity for numerous xerophytic plant lineages. However, we still have limited knowledge on the timing of evolution and biogeographic history of its flora, and potential drivers of diversification remain underexplored. To fill this knowledge gap, we focus on the Eurasian genus Jurinea (ca. 200 species), one of the largest plant radiations that diversified in the region. We applied a macroevolutionary integrative approach to explicitly test diversification hypotheses and investigate the relative roles of geography vs. ecology and niche conservatism vs. niche lability in speciation processes. To do so, we gathered a sample comprising 77% of total genus richness and obtained data about (1) its phylogenetic history, recovering 502 nuclear loci sequences; (2) growth forms; (3) ecological niche, compiling data of 21 variables for more than 2500 occurrences; and (4) paleoclimatic conditions, to estimate climatic stability. Our results revealed that climate was a key factor in the evolutionary dynamics of Jurinea. The main diversification and biogeographic events that occurred during past climate changes, which led to colder and drier conditions, are the following: (1) the origin of the genus (10.7 Ma); (2) long-distance dispersals from the Iranian Plateau to adjacent regions (∼7–4 Ma); and (3) the diversification shift during Pliocene-Pleistocene Transition (ca. 3 Ma), when net diversification rate almost doubled. Our results supported the pre-adaptation hypothesis, i.e., the evolutionary success of Jurinea was linked to the retention of the ancestral niche adapted to aridity. Interestingly, the paleoclimatic analyses revealed that in the Iranian Plateau long-term climatic stability favoured old-lineage persistence, resulting in current high species richness of semi-arid and cold adapted clades; whereas moderate climate oscillations stimulated allopatric diversification in the lineages distributed in the Circumboreal region. In contrast, growth form lability and high niche disparity among closely related species in the Central Asian clade suggest adaptive radiation to mountain habitats. In sum, the radiation of Jurinea is the result of both adaptive and non-adaptive processes influenced by climatic, orogenic and ecological factors.

Climatic stability and geological history shape global centers of neo- and paleoendemism in seed plants.

Assessing the distribution of geographically restricted and evolutionarily unique species and their underlying drivers is key to understanding biogeographical processes and critical for global conservation prioritization. Here, we quantified the geographic distribution and drivers of phylogenetic endemism for ~320,000 seed plants worldwide and identified centers and drivers of evolutionarily young (neoendemism) and evolutionarily old endemism (paleoendemism). Tropical and subtropical islands as well as tropical mountain regions displayed the world's highest phylogenetic endemism. Most tropical rainforest regions emerged as centers of paleoendemism, while most Mediterranean-climate regions showed high neoendemism. Centers where high neo- and paleoendemism coincide emerged on some oceanic and continental fragment islands, in Mediterranean-climate regions and parts of the Irano-Turanian floristic region. Global variation in phylogenetic endemism was well explained by a combination of past and present environmental factors (79.8 to 87.7% of variance explained) and most strongly related to environmental heterogeneity. Also, warm and wet climates, geographic isolation, and long-term climatic stability emerged as key drivers of phylogenetic endemism. Neo- and paleoendemism were jointly explained by climatic and geological history. Long-term climatic stability promoted the persistence of paleoendemics, while the isolation of oceanic islands and their unique geological histories promoted neoendemism. Mountainous regions promoted both neo- and paleoendemism, reflecting both diversification and persistence over time. Our study provides insights into the evolutionary underpinnings of biogeographical patterns in seed plants and identifies the areas on Earth with the highest evolutionary and biogeographical uniqueness-key information for setting global conservation priorities.

The prospect of direct air capture for energy security and climate stability

Energy policies aim at securing energy supply through domestic production or imports have significant consequences for climate change and its long-term impacts on the economy. Recent European energy crisis as a result of extensive reliance on imported Russian natural gas has highlighted the European Union (EU) energy vulnerability and has challenged its climate change commitments. While switching to alternative domestic fossil fuel sources such as coal in some member states has put the EU climate ambitions in jeopardy, it has also provided new opportunities for up-scaling renewable technologies as well as climate stability measures such as direct air capture (DAC). This paper examines the interaction between energy policy and climate stability by considering imported natural gas, domestic coal production, and possible DAC deployment in the EU under two scenarios of full cooperation and full competition among the EU member states. The results suggest that while cooperation induces higher reliance on imported energy, it also provides a strong incentive for DAC uptake. Competition on the other hand, may result in more reliance on domestic coal production and worse climate change outcomes despite the availability of DAC. Therefore, as the EU is striving for a more perfect union, it should consider better alignment of its short-term energy security policies with long-term climate stability ambitions.

Hydrochemistry, chemical weathering and their significance on carbon cycle in the Heilong (Amur) River Basin, Northeast China

Chemical weathering is regarded as a “geological thermostat”, affecting the global carbon cycle and long-term climate stability, and hydrochemistry of river is the important way to study weathering. The Heilong River (Amur River), as one of the largest rivers in the temperate/cool temperate zone, has received few studies on the chemical weathering rate and its contribution to the global carbon cycle in the entire Chinese section. This paper presents the hydrochemistry of river water, lake water, and groundwater from the arid upper reaches, the Greater Hinggan Mountains in the middle reaches, and the fluvial plain in the lower reaches of the Heilong River. TDS values range from 26.8 mg/l to 1141 mg/l with an average of 189 mg/l. The arid upper reaches are affected by strong evaporation and/or evaporite minerals dissolution, and the ion contents of some surface water and underground water exceed the quality standard for drinking water. Although the downstream flood plain area is highly industrial and agricultural, water chemistry shows that anthropogenic activities have not significantly deteriorated water quality. The chemical weathering rate of the small granitic and basaltic watersheds in the Heilong River Basin is within the lowest range in the world, which further demonstrates the control of climate factors on chemical weathering. The calculated CO2 consumption flux from silicate weathering in the Heilong River Basin is from 82.3 × 109 to 196 × 109 mol/y, accounting for 0.95%–2.25% of the global consumption values with a proportion of area of ∼1.2%. Compared with other temperate/cool temperate rivers worldwide, it is comparable to the Yenisei River in Siberia, but much higher than the Ob River and Lena River in Siberia, Mackenzie River and Yukon River in North America.

Centres of neo- and paleo-endemism for Chinese woody flora and their environmental features

Separating centres of neo- and paleo-endemism on the clade level from the tree of life could infer their evolutionary history and further pinpoint conservation priorities. Yet, centres of neo- and paleo-endemism in mega-biodiversity China are controversial as their environmental features are unclear. Here, we used a comprehensive species occurrence dataset (4509 woody endemics with 158,028 occurrences) and phylogenetic approach categorical analyses of neo- and paleo-endemism (CANAPE) to identify endemic centres of woody flora in China. A total of 22 major and several minor centres of endemism have been successfully identified, covering 13.36 % of China's total land area, yet capturing 89.60 % of woody endemics. They were roughly in accordance with the previously known centres of endemism. New areas with conservation importance such as northern Xinjiang, eastern Heilongjiang, and western Himalayas were identified. Different centres of endemism presented their preferred environmental features. Centres of neo-endemism were associated with higher elevation, concentrated in central-southeastern Himalaya, southwestern Hengduan (“evolutionary front”) and the northern Altai Mountains. In contrast, centres of paleo-endemism preferred favorable climates (high temperature and precipitation) and long-term climate stability. They were concentrated in southernmost China, in coincidence with one of the world's biodiversity hotspots (Indo-Burma). Centres of mixed-endemism were regarded as a transition type of neo- and paleo-endemism, concentrated in areas with moderate temperature and precipitation. Therefore, highlighting those centres of paleo-endemism should be considered as conservation priority areas due to dominating by old lineages with important evolutionary history and vulnerability to global drought.

Augusto Ruschi Biological Reserve vascular epiphytes: a hotspot in the mountains of the Atlantic Forest of Southeastern Brazil

The Atlantic Forest (AF) is globally known as a hotspot of biodiversity, with high levels of endemism and richness. However, within the AF, different localities may differ in their diversity values; in Southeastern Brazil, the mountainous region of Espírito Santo state is one of these highly biodiverse areas. Here, we present the first comprehensive checklist of the Augusto Ruschi Biological Reserve (ARBR) vascular epiphytes, a national protected area in the mountainous region of the state. Based on field expeditions carried out between 2018 and 2020 and extant herbarium collections, we reported a total of 359 species, 110 genera, and 20 families. Epidendrum henschenii Barb.Rodr. and Thysanoglossa organensis Brade are new records to the state. The richness recorded here is outstanding for the AF and one of the highest recorded in the Neotropical Region. The climatic conditions in the ARBR may help us understand this high species-richness, as well as the long-term climatic stability perhaps since the Miocene. Besides, the heterogeneity of the mountain habitats, driven mainly by erosion of the highlands since the early Cenozoic, resulted in the actual mountain’s configuration of eastern Brazil, synchronously with most taxa diversification occurred in the Atlantic Forest. The present study demonstrated the importance of protected areas and pristine forests for the conservation and maintenance of biodiversity and the importance of floristic studies to fill knowledge gaps in the Atlantic Forest, mainly in mountainous regions.

Long-term floristic and climatic stability of northern Indochina: Evidence from the Oligocene Ha Long flora, Vietnam

The antiquity of the tropical Asian flora is being revealed by recent detailed work on a number of Cenozoic plant megafossil sites, some of which have been radiometrically dated for the first time, but our knowledge of how the highly diverse modern biota came into being remains poor due to a sparsity of records. In this paper, we describe fossil plant assemblages from the Oligocene Dong Ho Formation of the Ha Long region, northern Vietnam. The Oligocene Ha Long megafossil flora has so far yielded 38 species, including conifers and angiosperms mainly belonging to Fagaceae, Lauraceae and Dipterocarpaceae, all with significant tropical Asian kinship. The Ha Long flora is similar to other Paleogene floras from southern China, especially those from the Pan Gulf of Tonkin region. The Ha Long floral composition is typical of a tropical-subtropical ecotone and the vegetation is reconstructed as a lowland tropical evergreen forest mixed with calcicole (limestone-loving) taxa. These taxa and the vegetation type they comprise still exist in this area. Palaeoclimate reconstruction made using both the Coexistence Approach and the Climate Leaf Analysis Multivariate Program indicate a mean annual temperature of ~20 °C, a coldest month mean temperature around 10 °C, and yearly precipitation averaging almost 2000 mm. These results suggest a warm and humid peripheral tropical environment. Floristic and climatic comparison within the Ha Long and other southern China palaeofloras reveals a long-term environmental, floristic and vegetational stability in this region since the Paleogene. This long-maintained plant diversity also provided a source for populating the East Asian flora and vegetation after the late Paleogene East Asian arid belt retreat.

Habitats hold an evolutionary signal of past climatic refugia

Climatic refugia have often been associated with hotspots of richness and endemism, and identified on the basis of molecular or paleobotanical information. Here, we apply a phylogenetic analysis to 18,000 plant communities distributed across the Pyrenees, a south European mountain range, to identify climatic refugia from imprints of relictuality inferred from species’ evolutionary distinctiveness (ED). We produced a genus-level phylogenetic tree to calculate the standardized mean ED value of plant communities (cED). Then, we explored which habitats concentrate the plant communities with the highest cED and the interrelated effect of past (long-term climatic stability) and present (topographic and spatial position) factors. Results show strong differences of cED among habitats: forests ranked first, followed by some open habitats like high altitude wetlands. Climate stability and roughness positively influenced cED. A weak negative association resulted between the two diversity measurements (richness and endemism rate) and also with cED. We propose that forests acted as “mobile refugia” during the glacial-interglacial periods, supported by paleoenvironmental reconstructions revealing continuous presence at regional scale of key broadleaved trees at that time. Azonal habitats like the endemic-poor humid communities at high elevation would have also played an important role as more permanent microrefugia. Our approach identifies a variety of habitats and plant assemblages that have successfully withstood past climate change in different ways, and therefore would hold an important evolutionary potential to cope with current climate change. Given their potential role in preserving biodiversity, they should be integrated in future conservation agendas.

Accurate lithium isotopic analysis of twenty geological reference materials by multi-collector inductively coupled plasma mass spectrometry

The lithium (Li) isotopes can be used to track the evolution of continental silicate weathering, which has an important role in maintaining Earth's long-term climate stability. At present, complex separation procedures and analytical mass bias restrict the accurate determination of Li isotopic compositions in various geological samples with different Li concentrations and matrix/Li ratios. Here, an optimization of dual-column chromatography achieves high Li recovery, low procedural blank, and low Na/Li ratio (< 1) after purification, allowing the acquisition of high precision Li isotope ratios by a Nu Plasma 3 multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). In order to evaluate the accuracy of new method, the δ7Li values of BHVO-2, BCR-2, AGV-2, JG-2, RGM-2, SGR-1b, GSR-6, GSR-12, and seawater, are repeatedly analyzed more than 3 times each and are consistent with the published data within the uncertainty. The long-term external reproducibility of δ7Li based on L-SVEC and IRMM-016 pure solutions is about ±0.2‰ (2SD), and is suitable for analysis of geological samples. These results suggest that new dual-column method is reproducible and reliable. We also report ten new reference materials including two USGS rocks (SDC-1: 1.8 ± 0.4‰; W-2a: 2.9 ± 0.3‰), four soils (GSS-3: 1.3 ± 0.2‰; GSS-4: −5.1 ± 0.4‰; GSS-6: −1.9 ± 0.3‰; GSS-8: 0.4 ± 0.3‰), and four stream sediments (GSD-6: −1.0 ± 0.4‰; GSD-11: 1.1 ± 0.3‰; GSD-12: 1.8 ± 0.2‰; GSD-14: 1.6 ± 0.4‰), all previously analyzed for K isotopes. There is significantly fractionation of Li and K isotopes during silicate weathering. Compared to the K isotopes, Li isotopes have more promising as an isotope tool for weathering due to its larger fractionation and its abiotic property.

Phylogenetic Endemism Hotspots of North American Birds Are Associated With Warm Temperatures and Long- and Short-Term Climate Stability

Human activities have dramatically altered the distribution and abundance of species, and our impacts are likely to increase in the near future. Conservation efforts are typically faced with scarce resources, forcing us to prioritize areas based in part on estimates of their conservation value. Two major factors in conservation value are a species uniqueness and its extinction risk. Though these ideas are multidimensional, one important component of uniqueness is evolutionary distinctness, while risk is strongly related to geographic range size. These components are combined in an assemblage-level measure called phylogenetic endemism (PE), which measures the degree to which the species in an assemblage are small-ranged and phylogenetically distinct. Broad-scale patterns and correlates of PE are becoming better known for a variety of groups, and have been shown to depend on current climate, geographic isolation and long-term climate stability. Human impacts (e.g., land cover changes), are likely to shape PE as well, though the coarse resolution of most previous studies may make this difficult to detect. Overall, PE patterns at fine spatial and temporal resolutions are not well understood. Here, we fill this gap using data from the North American Breeding Bird Survey. These data comprise a long-term annual record with fine spatial resolution and a near-continental extent. We assess geographic patterns and trends in PE, and relate these to a range of putative predictor variables including measures of current climate, land cover, long-term and recent climate change. Bird PE is concentrated in three main hotspots: the west coast, the southeast and south-central Canada east of the Rockies. High PE values tended to occur in regions with high temperatures and stability in temperature, both in the long (21,000 year) and short (35 year) time scales. PE patterns are driven more strongly by patterns of range size than phylogenetic distinctiveness, and are trending gradually upward, driven by increasingly frequent sightings of small-ranged species. These results indicate the importance of climate stability on multiple time scales in influencing endemism patterns and suggest a surprisingly minor influence of direct human land use. The increase in PE through time may reflect successful conservation efforts that have led to population recoveries of some small-ranged species.

Insights into the importance of areas of climatic stability in the evolution and maintenance of avian diversity in the Mesoamerican dry forests

AbstractWe analysed the phylogeographic structure of five resident bird lineages distributed in the seasonally dry tropical forests (SDTF) of Mesoamerica to test whether they show patterns of synchronous and geographically coincident genetic divergence during the Quaternary. We generated phylogenetic trees, estimated divergence times and analysed the genetic structure of populations (based on sequences of mitochondrial genes), as well as estimating historical distributions (range extension and areas of long-term climate stability) during the Late Pleistocene. We tested and selected the phylogeographic divergence scenarios that best explain the current divergence patterns of taxa using the Approximate Bayesian Computation (ABC) approach. For most species, phylogenetic trees and haplotype networks showed a clear genetic structure associated with geographical distribution. Overall, the divergence times ranged from 0.29–2.0 Mya, suggesting that diversification of populations occurred at different times during the Pleistocene. The palaeodistribution models predicted at least two areas of climatic stability within the current SDTF that probably allowed glacial-interglacial persistence of isolated bird populations along the Mexican Pacific, thus promoting their genetic divergence. The results provide information relevant to the identification of diversification hotspots for the Mesoamerican SDTF avifauna.

Accumulation over evolutionary time as a major cause of biodiversity hotspots in conifers.

Biodiversity hotspots are important for understanding how areas of high species richness form, but disentangling the processes that produce them is difficult. We combine geographical ranges, phylogenetic relationships and trait data for 606 conifer species in order to explore the mechanisms underlying richness hotspot formation. We identify eight richness hotspots that overlap known centres of plant endemism and diversity, and find that conifer richness hotspots occur in mountainous areas within broader regions of long-term climate stability. Conifer hotspots are not unique in their species composition, traits or phylogenetic structure; however, a large percentage of their species are not restricted to hotspots and they rarely show either a preponderance of new radiating lineages or old relictual lineages. We suggest that conifer hotspots have primarily formed as a result of lineages accumulating over evolutionary time scales in stable mountainous areas rather than through high origination, preferential retention of relictual lineages or radiation of species with unique traits, although such processes may contribute to nuanced differences among hotspots. Conifers suggest that a simple accumulation of regional diversity can generate high species richness without additional processes and that geography rather than biology may play a primary role in hotspot formation.

Extreme hydroclimate response gradients within the western Cape Floristic region of South Africa since the Last Glacial Maximum

The Cape Floristic Region (CFR) is one of the world's major biodiversity hotspots, and much work has gone into identifying the drivers of this diversity. Considered regionally in the context of Quaternary climate change, climate stability is generally accepted as being one of the major factors promoting the abundance of species now present in the CFR. However, little direct evidence is available from the region, and responses to changes in global boundary conditions have been difficult to assess. In this paper, we present new high-resolution stable isotope data from Pakhuis Pass, in the species-rich western CFR, and contextualise our findings through comparison with other records from the region. Combined, they indicate clear, coherent changes in regional hydroclimate, which we relate to broader forcing mechanisms. However, while these climate change events share similar timings (indicating shared macro-scale drivers), the responses are distinct between sites, in some cases expressing opposing trends over very short spatial gradients (<50 km). We describe the evolution of these trends, and propose that while long-term (105 yr) general climatic stability may have fostered high diversity in the region through low extinction rates, the strong, abrupt changes in hydroclimate gradients observed in our records may have driven a form of allopatric speciation pump, promoting the diversification of plant lineages through the periodic isolation and recombination of plant populations.

Insights into the evolutionary dynamics of Neotropical biomes from the phylogeography and paleodistribution modeling of Bromelia balansae.

Historical abiotic and biotic factors have strongly affected species diversification and speciation. Although pre-Pleistocene events have been linked to the divergence of several Neotropical organisms, studies have highlighted a more prominent role of Pleistocene climatic oscillations in shaping current patterns of genetic variation of plants. We performed phylogeographic analyses based on plastidial markers and modeled the current distribution and paleodistribution of Bromelia balansae (Bromeliaceae), an herbaceous species with a wide geographical distribution in South America, to infer the processes underlying its evolutionary history. Combined molecular and paleodistributional modeling analyses indicated retraction during the Last Glacial Maximum followed by interglacial expansion. Populations occurring in the semideciduous Atlantic Forest and the Cerrado formed two distinct genetic clusters, which have been historically or ecologically isolated since late Pliocene to early Pleistocene. Populations located in the transition zone had higher levels of genetic diversity, as expected by the long-term climatic stability in the region detected in our ecological niche models. Our study adds important information on how herbaceous species have been affected by past climate in Central and Southeast Brazil, helping to disentangle the complex processes that have triggered the evolution of Neotropical biota.

The fate of endemic insects of the Andean region under the effect of global warming.

Three independent but complementary lines of research have provided evidence for the recognition of refugia: paleontology, phylogeography and species distributional modelling (SDM). SDM assesses the ecological requirements of a species based on its known occurrences and enables its distribution to be projected on past climatological reconstructions. One advantage over the other two approaches is that it provides an explicit link to environment and geography, thereby enabling the analysis of a large number of taxa in the search for more general refugia patterns. We propose a methodology for using SDM to recognize biogeographical patterns of endemic insects from Southern South America. We built species distributional models for 59 insect species using Maxent. The species analyzed in the study have narrow niche breadth and were classified into four assemblages according to the ecoregion they inhabit. Models were built for the Late Pleistocene, Mid-Holocene and Present. Through the procedure developed for this study we used the models to recognize: Late Pleistocene refugia; areas with high species richness during all three periods; climatically constant areas (in situ refugia); consistent patterns among in situ refugia, Pleistocene refugia and current distribution of endemic species. We recognized two adjacent Pleistocene refugia with distinct climates; four in situ refugia, some of which are undergoing a process of fragmentation and retraction or enlargement. Interestingly, we found a congruent pattern among in situ refugia, Pleistocene refugia and endemic species. Our results seem to be consistent with the idea that long-term climate stability is known to have a key role in promoting persistence of biodiversity in an area. Our Pleistocene and in situ refugia are consistent with refugia identified in studies focusing on different taxa and applying other methodologies, showing that the method developed can be used to identify such areas and prove their importance for conservation.

A 5000-yr record of Afromontane vegetation dynamics from the Drakensberg Escarpment, South Africa

Afromontane environments are sensitive to climatic and environmental change as a consequence of their inherent altitudinal and latitudinal gradients. Palaeoecological investigations have been used in these areas to track ecosystem response to climatic and anthropogenic drivers, and have gained prominence in recent years in the context of the need to understand faunal and floral response to future climate uncertainty. This paper focusses on long-term vegetation history in the Drakensberg Escarpment of South Africa, an area with a long history of human habitation, that is internationally recognised for its conservation importance. Ecologists have hypothesised that human-induced burning during the late Quaternary may have been responsible for the expansion of Afromontane grasslands at the expense of forests, which currently exist as refugial patches within fire-protected valleys. Here we test this argument using empirical palaeoecological evidence derived from a subalpine wetland in the Cathedral Peak area of the Drakensberg Escarpment. An age model derived from eight AMS radiocarbon ages, and supported by a pollen time-marker, is used to provide chronological control. Fossil pollen, and carbon and nitrogen isotope analyses, are combined to reconstruct past vegetation dynamics. Results indicate a lack of major compositional vegetation change over the past 5000 years, suggesting long-term vegetation and climatic stability throughout the record. The pollen data show that grasslands have dominated the region, while forests expanded during the late Holocene, thereby refuting the notion of recent forest reduction in the Drakensberg.