Responses Of Different Species Research Articles

Pervasive impacts of climate change on the woodiness and ecological generalism of dry forest plant assemblages

Abstract Climate emergency is a significant threat to biodiversity in the 21st century, but species will not be equally affected. In summing up the responses of different species at the local scale, we can assess changes in the species quantity and composition of biotic assemblages. We used more than 420K curated occurrence records of 3060 plant species to model current and future patterns of plant species distribution in one of the world's largest tropical dry forests—the Caatinga. While allowing different model extrapolation scenarios, we estimated potential changes in the species richness and composition of dryland plant assemblages in response to projected climate change, and assessed how the ecological generalism and woodiness of plant assemblages can be impacted by the climate crisis. More than 99% of plant assemblages were projected to lose species by 2060, with biotic homogenisation—the decrease in spatial beta diversity—forecasted in 40% of the Caatinga. The replacement of narrow‐range woody species by wide‐range non‐woody ones should impact at least 90% of Caatinga plant assemblages. The exacerbated species loss in the dryland plant assemblages was connected to the heterogenisation and homogenisation of biotic assemblages. Still, the magnitude of climate change impacts on ecological generalism and woodiness patterns of dryland plant assemblages differ according to the direction of the biotic change process. Synthesis. The future increase in aridity will change the patterns of woodiness and ecological generalism of tropical dry forest plant assemblages by decreasing vegetation diversity and complexity. The projected biotic changes in dryland plant assemblages indicate the erosion of ecosystem services linked to biomass productivity and carbon storage. We highlight the importance of long‐term conservation planning for maintaining tropical dry forests.

Phenology advances uniformly in spring but diverges in autumn among three temperate tree species in response to warming

Predicting the length of growing season to further warming relies on both spring and autumn phenological responses of different species, but with little experimental evidence under different levels of warming. Here, the timing of spring phenology including budburst and leaf unfolding, and autumn phenology including leaf coloration and leaf fall, were examined in 2-year-old seedlings of three temperate tree species (Fraxinus mandschurica, Quercus mongolica, and Juglans mandshurica) that were grown in the field under warming conditions (W0, ambient; W2, +2°C; W4, +4°C). Our study showed that warming advanced budburst and leaf unfolding by 9 and 8 days in the W2 treatments and by 13 and 15 days in the W4 treatments, respectively, with the magnitude varied greatly among species. However, we found a delayed autumn leaf senescence only for Q. mongolica, for which leaf coloration and leaf fall delayed by 19 and 6 days and by 17 and 12 days in the W2 and W4 treatments, respectively. The temperature sensitivity of budburst declined with increasing temperature in Q. mongolica. The growing season was extended by 7–18 and 10–25 days in W2 and W4, primarily through the advancement of spring phenology. Warming increased budburst synchrony, such that J. mandshurica, which typically has the earliest leaf emergence, lost its growth and competitive advantages over the more phenologically plastic species, F. mandschurica and Q. mongolica. Our results provide new insights into the effects of elevated temperatures on phenological shifts and their potential influences on tree species recruitment and forest structure and composition.

Differential response of seabird species to warm- and cold-water events in a heterogeneous cross-shelf environment in the Gulf of Alaska

We used seabird surveys and concurrent oceanographic observations in the Northern Gulf of Alaska during spring 1998-2019 to evaluate how seabirds responded to temperature variability, including a protracted marine heatwave, in a highly heterogeneous ecosystem. We examined temporally changing distributions of seabirds along the Seward Line, a 220 km transect across the shelf and slope, and evaluated relationships between water-mass properties and seabird abundance. Environmental factors associated with abundance include depth, water-column temperature and salinity, and surface-current velocities. Environmental responses of alcids and gulls contrasted with those of procellariiform (tubenose) seabirds, and their trajectories suggest a possible shift in community composition under future climate warming. Changes in seabird distribution and abundance associated with a shift from cold to warm conditions were especially pronounced over the middle- and outer-shelf domains, which are transitional between coastal and oceanic water masses. The abundance of tubenoses increased during and after the heatwave, whereas alcids and gulls shifted inshore, exhibited reproductive failures, and experienced mass mortalities due to starvation. Tubenoses appear well-adapted to periods of lower productivity during warming events because of their flight efficiency, allowing them to search widely to locate prey patches. In contrast, alcids, which forage by diving and have energetically expensive flight, appear sensitive to such conditions.

Species portfolio effects dominate seasonal zooplankton stabilization within a large temperate lake.

Portfolio effects (PEs) in ecology refer to the suite of phenomenon where the temporal variation of aggregate ecosystem properties (i.e., abundance) is lower than that of their ecosystem components. An example of this is where differential responses of species to environmental variation generate stability at higher levels of ecological organization (e.g., local community, metapopulation, metacommunity). Most of the research examining such PEs has focused on spatial or interannual variation of ecosystems; however, as global change continues to alter seasonality and ecosystem functioning, understanding the underlying food web structures that help maintain stability at multiple spatial and temporal scales is critical to managing ecological systems. Recent advances investigating diversity-stability relationships has led to the development of frameworks that incorporate a metacommunity perspective which allows for the partitioning of PEs across organizational scales (i.e., local community, metapopulation, cross-community, metacommunity) from local population dynamics (total). This partitioning yields insights into the mechanisms that generate observed PEs in nature. Here, we employed one of these recently developed frameworks on a temporally (1986-1999, 2008-2019) and spatially (five sampling stations, local communities) extensive data set of zooplankton abundance (e.g., density) within a large temperate lake to investigate how temporal (seasonal) and spatial (among site) PEs influence stability within the zooplankton metacommunity. We found that seasonal asynchrony of different zooplankton species within local communities and across communities generated the vast majority of stabilization, while spatial (i.e., metapopulation) dynamics were more synchronous and contributed little to overall system stability. Furthermore, significantly positive diversity-asynchrony relationships at the total, local- and cross-community scales were found as asynchrony was positively correlated with local Shannon diversity. Last, a comparison of PEs over the time periods, during which significant local and global changes (i.e., climate warming, invasive species) have occurred suggests that PEs may be eroding, as increasingly synchronous dynamics and declining diversity in recent years have led to a rise in metacommunity variability. We end by arguing for the critical importance of understanding seasonally driven stabilizing mechanisms as local and global changes threaten to fundamentally alter seasonal signals with potentially strong implications for the structures that lend stability to ecosystems.

Molecular Defense Response of Pine Trees (Pinus spp.) to the Parasitic Nematode Bursaphelenchus xylophilus.

Pine wilt disease (PWD) is a severe environmental problem in Eastern Asia and Western Europe, devastating large forest areas and causing significant economic losses. This disease is caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus, a parasitic migratory nematode that infects the stem of conifer trees. Here we review what is currently known about the molecular defense response in pine trees after infection with PWN, focusing on common responses in different species. By giving particular emphasis to resistance mechanisms reported for selected varieties and families, we identified shared genes and pathways associated with resistance, including the activation of oxidative stress response, cell wall lignification, and biosynthesis of terpenoids and phenylpropanoids. The role of post-transcriptional regulation by small RNAs in pine response to PWN infection is also discussed, as well as the possible implementation of innovative RNA-interference technologies, with a focus on trans-kingdom small RNAs. Finally, the defense response induced by elicitors applied to pine plants before PWN infection to prompt resistance is reviewed. Perspectives about the impact of these findings and future research approaches are discussed.

Differential Physiological Responses Of Copper-Sensitive and Copper-Tolerant Elsholtzia Species to Copper Toxicity: the Character of Cell Walls and their Subfractions

Differential Physiological Responses Of Copper-Sensitive and Copper-Tolerant Elsholtzia Species to Copper Toxicity: the Character of Cell Walls and their Subfractions

High Atmospheric CO2 Concentration Mitigates Drought Effects on Acanthostyles buniifolius an Important Grassland Weed in South America.

The differential growth and yield response of plant species to rising carbon dioxide concentrations and climatic change may alter species diversity within biomes. The Pampa Biome in South America is an important grassland biome of agronomic and environmental importance. Acanthostyles buniifolius (Chirca) is one of the most important weeds in natural pasture areas widely distributed in southern South America and can adversely affect livestock production. The current study was designed to identify possible responses of Chirca to CO2 concentration ([CO2]) and drought that would indicate higher adaptation and potential proliferation within the Pampa Biome. Chirca plants were cultivated at two CO2 concentrations (400 (a[CO2]) and 700 (e[CO2]) µmol mol−1) and two water conditions (under water restriction—15% of the pot capacity; and plants without water restriction—pot capacity). Besides growth parameters, we also determined water potential (ѱw), relative water contents (RWC), proline, glycine betaine, total soluble sugars, hydrogen peroxide, lipid peroxidation, superoxide dismutase (SOD), ascorbate peroxidase (APX) activity, chlorophyll A and B, carotenoids and root dry mass (RDM). Plants exposed to e[CO2] are more efficient in water use and have a greater increase in root dry mass, enabling greater adaptation to climate-induced droughts. Among the biochemical changes observed in the plants under drought stress, the accumulation of proline, glycine betaine, and total soluble sugars were the most evident mechanisms allowing plants to tolerate drought stress by osmotic adjustment.

Taxonomic and functional components of avian metacommunity structure along an urban gradient.

Identifying biological processes that structure natural communities has long interested ecologists. Community structure may be determined by various processes, including differential responses of species to environmental characteristics, regional-level spatial influences such as dispersal, or stochasticity generated from ecological drift. Few studies have used the metacommunity paradigm (interacting communities linked by dispersal) to investigate avian community composition along an urban gradient, yet such a theoretical construct may provide insights into species turnover even in unnatural settings such as rural to urban gradients. We measured the influence of spatial and environmental characteristics on two aspects of avian community structure across a gradient of urbanization: 1) taxonomic composition and 2) functional richness based on diet, foraging strategies, nesting locations and morphology. We also measured the relationship between species traits and environmental variables with an RLQ-fourth corner analysis. Together, environmental and spatial processes were significantly related to taxonomic structure and functional richness, but spatial variables accounted for more variation than environmental variables. Fine spatial scales were positively correlated with insectivorous birds and negatively correlated with body and wing size. Urbanization was positively correlated with birds that forage at the canopy level, while emergent wetlands were negatively correlated with birds that nested in cliffs and frugivorous birds. Functional richness and urbanization were significantly related to fine spatial variables. Spatial and environmental factors played an important role in taxonomic and functional structure in avian metacommunity structure. This study highlights the importance of studying multiple aspects of biodiversity, such as taxonomic and functional dimensions, especially when examining effects of complementary spatial and environmental processes.

Rapid evolution of a coastal marsh ecosystem engineer in response to global change

There is increasing evidence that global change can alter ecosystems by eliciting rapid evolution of foundational plants capable of shaping vital attributes and processes. Here we describe results of a field-scale exposure experiment and multilocus assays illustrating that elevated CO2 (eCO2) and nitrogen (N) enrichment can result in rapid shifts in genetic and genotypic variation in Phragmites australis, an ecologically dominant plant that acts as an ecosystem engineer in coastal marshes worldwide. Compared to control treatments, genotypic diversity declined over three years of exposure, especially to N enrichment. The magnitude of loss also increased over time under conditions of N enrichment. Comparisons of genotype frequencies revealed that proportional abundances shifted with exposure to eCO2 and N in a manner consistent with expected responses to selection. Comparisons also revealed evidence of tradeoffs that constrained exposure responses, where any particular genotype responded favorably to one factor rather than to different factors or to combinations of factors. These findings challenge the prevailing view that plant-mediated ecosystem outcomes of global change are governed primarily by differences in species responses to shifting environmental pressures and highlight the value of accounting for organismal evolution in predictive models to improve forecasts of ecosystem responses to global change.

Species differences in temporal response to urbanization alters predator-prey and human overlap in northern Utah

Wildlife are under continuous pressure to adapt to new environments as more land area is converted for human use and human populations continue to concentrate in suburban and exurban areas. This is especially the case for terrestrial mammals, which are forced to navigate these habitat matrices on foot. One way in which mammals may occupy urbanized landscapes is by altering their temporal activity behavior. Typically, studies have found that mammals increase their nocturnal activity within urbanized environments to avoid overlap with humans. However, to date, the majority of studies on this topic have focused on single species, and studying whether this trend holds across an entire community has important ecological implications. Specifically, understanding how differences in species temporal activity response alters predator-prey dynamics and sympatric interspecies competition can provide insight into urban wildlife community assembly and provide a mechanistic understanding of species co-occurrence within these systems. In this study, we used data from a community science camera trapping project in northern Utah to elucidate how human influence alters the temporal activity behavior of five medium- to large-sized mammals and how differences in species response affect predator-prey, human, and sympatric competitor temporal niche overlap. We found community-wide changes in activity across study sites, with increases in late night and midday activity and decreases in crepuscular activity within the more-urbanized site. However, species-specific behavioral changes varied, and these changes resulted in reduced overlap, especially between coyotes (Canis latrans) and their potential prey species. These results provide information on how human influence may alter community assembly and species-species interactions within a wildland-urban interface.

The health risk assessment of heavy metals to human health through the consumption of Tilapia spp and catfish caught from Lake Mariut, Egypt

This work assesses the concentration of As, Cd, Pb, Hg, and Al in three of Tilapia species and catfish caught from Lake Mariut. As well as the human health risk and muscle biochemical composition. Besides, the antioxidant responses of different species. The average metal concentration order was Pb> As> Cd> Al> Hg. The Cd and Pb levels in all species; besides, the Hg levels in Oreochromis niloticus and Oreochromis aureus exceeded the maximum limits set by FAO, European legislation, and FAO/WHO. The human health risk was assessed using estimated dietary intakes, the target hazard quotient (THQ), and the carcinogenic risk (CR). THQAs was >1 in all examined fishes and closer to 1 in THQCd, Hg. As well, CR level for As was higher than the permissible value. Tilapia zillii showed significant decreases in carbohydrates compared to Clarias gariepinus; also, ash content compared to C. gariepinus, O. niloticus, and O. aureus. Furthermore, water content compared to O. aureus. In contrast, significant increases of SOD in O. niloticus compared to C. gariepinus. In addition, CAT and GPx in O. aureus compared to C. gariepinus. Also, GR in both O. niloticus and O. aureus compared to C. gariepinus, and GSH in all of Tilapia spp. compared to C. gariepinus. Data obtained provide evidence of health risks to the consumers. Therefore, more caution is required.

Differential response of tree species from Brazilian tropical dry Forest (Caatinga) to phosphorus doses associated with organic matter

The availability of phosphorus (P) and organic matter in Chromic Luvisols, predominant in the Caatinga biome, is generally low and makes it difficult to reintroduce native plants in forest recovery projects. The objective was to evaluate the production of dry mass, accumulation a and use efficiency of P by three tree species native from Caatinga biome with application of doses of P and organic matter. This experiment was carried out in a greenhouse in a completely randomized design in a 2 × 3 × 5 factorial scheme, consisting of with two doses of organic matter (0 and 50 g kg−1), three species of plants (Tabebuia aurea (Silva Manso) Benth. & Hook.f. ex S Moore, Amburana cearensis, Allemão AC Smith and Caesalpinia ferrea Mart. Ex Tul.) and five doses of P (0, 50, 100, 150 and 200 mg dm−3). At 120 days after transplanting, concentrations of P available in the soil and leaf soluble P fractions increased linearly with the P doses. The availability of P in the soil and, consequently, the accumulation of soluble and total P in the plant tissues were greater with organic matter application. The studied species use different P compartmentalization strategies depending on their dry mass production capacity. Phosphate and or organic matter application is necessary in the initial growth phase of the studied species, notably T. aurea and C. ferrea. The dry mass of T. aurea was greater than that of C. ferrea and A. cearensis.

Responses to Climate Change of Maximum Latewood Density from Larix speciosa Cheng et Law and Abies delavayi Franch. in the Northwest of Yunnan Province, China

Tree-ring density has been used for climate-response analysis and climate reconstruction for many species. However, our knowledge of wood density for the responses of different species to climate remains very limited and inconclusive. To determine the relationship between maximum latewood density (MXD) and climate for deciduous and evergreen coniferous species, MXD chronologies were developed from Larix speciosa Cheng et Law and Abies delavayi Franch. growing at 3200–3300 m a.s.l. in Gongshan county, northwestern Yunnan, in China. Significant positive correlations with late summer mean temperature were found for the MXD chronologies of both species. However, the highest correlation occurred in August–September for L. speciosa (r = 0.551, p < 0.01) and in September–October for A. delavayi (r = 0.575, p < 0.01), which may be associated with the physiological habits of trees. Linear model can describe relationships between late-summer temperature and MXD index for L. speciosa (MXD = 0.0506T8–9 − 0.0509, R2 = 30.3%) and A. delavay (MXD = 0.0317T9–10 + 0.4066, R2 = 33.0%). The composite chronology from the two species can reveal a late summer temperature (August−October) signal with the explained variance 32.2% for its response model. However, in dry areas and or at high altitudes close to upper tree line, the responses of wood densities to climate require further investigation for deciduous and evergreen coniferous species.

The shape of root systems in a mountain meadow: plastic responses or species-specific architectural blueprints?

The efficient uptake of nutrients depends on the ability of roots to respond to gradients of these resources. Although pot experiments have shown that species differ in their ability to proliferate their roots in nutrient-rich patches, the role of such differences in determining root shapes in the field is unclear. We used fine-scale quantitative (q)PCR-based species-specific mapping of roots in a grassland community to reconstruct species-specific root system shapes. We linked them with data from pot experiments on the ability of these species to proliferate in nutrient-rich patches and their rooting depth. We found remarkable diversity in root system shapes, from cylindrical to conical. Interspecific differences in rooting depths in pots were the main determinant of rooting depths in the field, whereas differences in foraging ability played only a minor role. Although some species with strong foraging ability did place their roots into nutrient-rich soil layers, it was not a universal pattern. The results imply that although the vertical differentiation of grassland species is pronounced, it is primarily not driven by the differential plastic response of species to soil nutrient gradients. This may constrain the coexistence of species with similar rooting depths and may instead favour coexistence of species differing in their architectural blueprints.

Изменение климата и его влияние на адаптацию и внутривидовую изменчивость хвойных пород Европейского Севера России

Current climate change is affecting forests and requires a specific forest management strategy. The review aims to analyze the impact of observed and projected climate change on the tree species adaptation response with regard to their intraspecific differentiation to determine the potential for further research and develop forest management adjustments in the Russian European North. The article shows that long-term responses in forest ecosystems are related not only to thermal shifts, but also to changes in moisture regime, insolation, distribution of pathogens, etc. Changes in forest ecosystems may involve physiological and genetic mutations in all species and be extended over several generations. Species must undergo evolutionary adaptation due to genetic mutations. With steady warming and changes in air and soil moisture regimes, forest productivity may increase due to a change in the growing season length, increasing photosynthetic activity. On the other hand, productivity is likely to decrease as a result of reduced precipitation and drought. Climatic changes over the vast territory of Russia will occur gradually, and their level will be different in geographically diverse regions. The forest-forming tree species will exhibit various short-term responses associated with the geographical location of the population and the climatic conditions under which the plants evolved during the stable climatic period following their dispersal in the Holocene. At the same time, inherited growth and development parameters will respond to changing climatic conditions, which will be determined by the geographical location of the forest species and their population characteristics. The differential response of tree species needs to be considered when planning forest management measures, adapting them to possible climatic changes.

Pith Eccentricity, Basal Area Increments and Disturbances Inferred from Tree-Ring Growth

Forest management constantly seeks tools that can optimize the production of goods and services. As natural archives, tree rings have proven to be effective in terms of refining the dynamics of growth on a temporal basis. This study evaluates the application of these tree rings in estimating the effect of pith eccentricity on forest growth, modeling the increase in basal area (BAI) and identifying disturbances in five coexisting species in northern Mexico. A Wilcoxon rank sum test showed significant differences, with higher radial growth in the north direction compared to the other directions. A mixed model analysis revealed two patterns of BAI growth, fast and slow growing. The former includes P. arizonica, P. engelmannii and P. leiophylla, whereas the latter comprises P. durangensis and P. lumholtzii. The fast-growing group shows a higher increment during the sapling stage. However, during subsequent stages, it presents growth rates similar to those of the slow-growing group. Finally, the percentage growth change (PGC) filter approach identified species disturbances with differential species responses, which temporarily cause uneven-aged forest. We conclude that tree rings can provide valuable information for forest management, and their temporal amplitude can be supported with information from permanent plots.

Multifaceted roles of mitochondrial stress responses under ETC dysfunction - repair, destruction and pathogenesis.

Electron transport chain (ETC) dysfunction is a common feature of mitochondrial diseases and induces severe cellular stresses, including mitochondrial membrane potential (Δψm ) reduction, mitochondrial matrix acidification, metabolic derangements and proteostatic stresses. Extensive studies of ETC dysfunction in yeast, Caenorhabditis elegans, cultured cells and mouse models have revealed multiple mitochondrial stress response pathways. Here, we summarise the current understanding of the triggers, sensors, signalling mechanisms and the functional outcomes of mitochondrial stress responses in different species. We highlight Δψm reduction as a major trigger of stress responses in different species, but the responses are species-specific and the outcomes are context-dependent. ETC dysfunction elicits a mitochondrial unfolded protein response (UPRmt ) to repair damaged mitochondria in C. elegans, and activates a global adaptive programme to maintain Δψm in yeast. Yeast and C. elegans responses are remarkably similar at the downstream responses, although they are activated by different signalling mechanisms. UPRmt generally protects ETC-defective worms, but its constitutive activation is toxic for wildtype worms and worms carrying mutant mtDNA. In contrast to lower organisms, ETC dysfunction in mammals mainly activates a mitochondrial integrated stress response (ISRmt ) to reprogramme metabolism and a PINK1-Parkin mitophagy pathway to degrade damaged mitochondria. Accumulating in vivo results suggest that the ATF4 branch of ISRmt exacerbates metabolic derangements to accelerate mitochondrial disease progression. The in vivo roles of mitophagy in mitochondrial diseases are also context-dependent. These results thus reveal the common and unique aspects of mitochondrial stress responses in different species and highlight their multifaceted roles in mitochondrial diseases.

The effects of crop tree thinning intensity on the ability of dominant tree species to sequester carbon in a temperate deciduous mixed forest, northeastern China

Forest management is one of the important nature-based solutions for climate mitigation. Thinning can indirectly influence tree physiology by changing the microclimate and directly change the stand biomass, which can impact forest carbon sequestration. However, previous results about how thinning might influence carbon stocks remain inconsistent regarding post-thinning carbon accretion. In this study, crop tree release (CTR) thinning in four intensities (CK: 0% of basal area removal, LT: 17.25%, MT: 34.73%, and HT: 51.87%) were conducted in a temperate deciduous forest in Jiaohe, northeastern China in 2011. Plot inventories in 2011, 2013, 2015, 2018 and 2021 and tree cores collected in 2017 and 2018 offered the opportunity to examine how are the interannual carbon sequestration ability of Korean pine and Manchurian ash responded to CTR thinning in four intensities. We quantify the carbon sequestration ability of trees by calculating individual stem carbon stock and annual carbon stock rate to examine whether the previous inconsistency was attributed to different responses of species, and the ignorance of frozen carbon content. The results show: (1) after thinning, the underestimation of carbon stocks of Manchurian ash decreased with the increasing thinning intensity. The greatest underestimation of Manchurian ash reaches 2922 kg ha−1, while that of Korean pine only reaches 283 kg ha−1. Compared with Manchurian ash, the conventional carbon fraction of 0.5 for Korean pine is more appropriate, and the misestimation of Korean pine didn't show an obvious pattern with the intensity of thinning. (2) Under light thinning, both species maintained a stable carbon stock growth, and the frozen carbon content of Korean pine was significantly increased. During the 10 years after light thinning, the individual stem carbon of Korean pine increased from 57 kg to 81 kg, and Manchurian ash increased from 201 kg to 268 kg. The average rate of increase of individual stem carbon is positively related to tree size. Removing such large-diameter trees from the stand is likely to decrease carbon stock rate. Therefore, it is essential to design carbon-friendly silviculture prescriptions worldwide under the consideration of species, sizes, and intensities.

Geographic and ecological segregation in an extinct guild of flightless birds: New Zealand’s moa

The nine currently recognized species of moa (Order – Dinornithiformes; Bonaparte 1853) suffered extinction soon after New Zealand was settled by humans.  They were the result of an evolutionary radiation that produced a unique guild of birds – giant, and totally wingless species that evolved in the absence of non-volant mammals.   Recent advances in dating and paleoclimatology, and compilations of data on distributions of the nine species of moa, along with information on the geographic, topographic, climatic and edaphic characteristics of sites from which moa remains have been recovered, enabled us to test whether their evolutionary radiation truly was ‘adaptive’, producing ecologically distinct species.  Randomization, resampling analyses of moa distributions across North and South Islands revealed highly significant geographic and ecological segregation, with different species tending to occupy different islands, regions within islands, or elevations within regions.  Quadratic Discriminant Analyses demonstrated niche segregation at even finer scales, including that based on vegetation-defined habitats and on local climatic, topographic and edaphic conditions.  Moa distributions also appear to have been dynamic over time, shifting in their upper elevational limits as climatic conditions changed and vegetative zones shifted upward during the Holocene Epoch.  Our ongoing studies are building on the results presented here to explore the temporal dynamics of moa distributions, assess differential responses of moa species to natural and anthropogenic drivers, and determine how these forces may have combined to cause the extinction of moa just a few centuries ago.

The combined effects of climate and canopy cover changes on understorey plants of the Hyrcanian forest biodiversity hotspot in northern Iran.

Understanding forest understorey community response to environmental change, including management actions, is vital given the understorey's importance for biodiversity conservation and ecosystem functioning. The Natural World Heritage Hyrcanian temperate forests (Iran) provide an ideal template for furnishing an appreciation of how management actions can mitigate undesired climate change effects, due to the forests' broad environmental gradients, isolation from colonization sources and varied light environments. We used records of 95 understorey plant species from 512 plots to model their probability of occurrence as a function of contemporary climate and soil variables, and canopy cover. For 65species with good predictive accuracy, we then projected two climate scenarios in the context of either increasing or decreasing canopy cover, to assess whether overstorey management could mitigate or aggravate climate change effects. Climate variables were the most important predictors for the distribution of all species. Soil and canopy cover varied in importance depending on understorey growth form. Climate change was projected to negatively affect future probabilities of occurrence. However, management, here represented by canopy cover change, is predicted to modify this trajectory for some species groups. Models predict increases in light-adapted and generalist forbs with reduced canopy cover, while graminoids and ferns still decline. Increased canopy cover is projected to buffer an otherwise significant decreasing response of cold-adapted species to climate change. However, increasing canopy cover is not projected to buffer the predicted negative impact of climate change on shade-adapted forest specialists. Inconsistent responses of different species and/or growth forms to climate change and canopy cover reflect their complicated life histories and habitat preferences. Canopy cover management may help prevent the climate change induced loss of some important groups for biodiversity conservation. However, for shade-adapted forest specialists, our results imply a need to adopt other conservation measures in the face of anticipated climate change.