Global change and shifts in non-native and native species distributions

Abstract/Description

Mountain ecosystems, celebrated for their high biodiversity and endemism, are experiencing rapid ecological shifts due to global change drivers. Both climate and land-use changes are increasingly altering species distributions, yet the scale at which these changes occur is often overlooked. Spatial heterogeneity in mountains arises not only from topography but is further amplified by bedrock and soil conditions, vegetation, and human activities, leading to high species turnover over small distances. To effectively assess biodiversity responses to climate and land-use change, it is crucial to capture these dynamics at appropriate spatiotemporal scales.

In this presentation, I will showcase insights from several global and regional long-term monitoring initiatives designed to quantify biodiversity variation across scales. The MicroFracNet project examines beta diversity patterns at multiple spatial resolutions, helping to disentangle the key drivers of species turnover. Complementary studies from the Mountain Invasion Research Network (MIREN) provide high-resolution assessments of shifting species distributions in space and time, including a fast trail survey that tracks the elevational range shifts of non-native species at a 5-meter resolution and the MIREN Rocks survey, which investigates the localized impacts of recreational climbing – interacting with extreme cliff microclimates – on cliff-face vegetation. Finally, I will discuss a unique long-term phenological survey in northern Scandinavia, where vegetation and its seasonal dynamics have been monitored every five days for the past decade, as well as in historical surveys dating back 110 years. This study provides rare insights into the temporal scale of biodiversity change and highlights the frequency of observations needed to accurately track the complexity of species redistributions.

By integrating these diverse monitoring efforts, this talk will highlight how fine-scale spatial and temporal variations shape species redistributions in mountain ecosystems. These insights are crucial for understanding the ecological mechanisms driving range shifts, ultimately informing conservation strategies to mitigate the impacts of global change on mountain biodiversity.

Abstract/Description

Climate change is shifting species distributions, leading to changes in community composition and novel species assemblages worldwide. However, the responses of tropical forests to climate change across large-scale environmental gradients remain largely unexplored. Using long-term field inventory data collected for over 66,000 trees of more than 2,500 species occurring over 3,500 m elevation along the hyper-diverse Amazon-to-Andes elevational gradient, we assessed community-level shifts in species composition over a 44-year time span. We tested for the predicted increase in relative abundances of species from warmer climates (thermophilization) along the Amazon-to-Andes elevational gradients in Peru and Bolivia. Additionally, we examined the relative contributions of tree mortality, recruitment, and growth to observed compositional changes. Mean thermophilization rates across the Amazon-to-Andes gradient were slow relative to concordant changes in regional temperatures. Thermophilization rates were positive and more variable among Andean forest plots compared to Amazonian plots but were fastest at mid-elevations around the cloud base. Across all elevations, thermophilization rates were driven primarily by tree mortality and decreased growth of highland species rather than an influx of lowland species with higher thermal optima. Given the high variability of community-level responses to warming along the elevational gradients and the generally slower-than-warming rates of compositional change, we conclude that most tropical tree species, and especially Amazonian tree species, will not be able to escape current or future climate change through upward range shifts.

Abstract/Description

Studies on how functional characteristics of plant communities respond to elevation and the associated climatic gradient have so far been spatially restricted and performed over single slopes or mountain ranges. These studies also vary in their designs, objectives and coverage of traits sampled. Here we present the first global study of community trait patterns (including community mean traits and functional diversity of the community) along elevational climatic gradients in natural vegetation and disturbed roadside habitats. Moreover, we analyze how functional changes in response to climate differ between communities when considering native plant species versus all community members. To do so, we compiled a unique database of primary data, including standardized vegetation surveys and in-situ trait collection from over 1000 species (within the scope of the Mountain Invasion Research Network) in 18 mountain ranges around the world. We measured nine key functional traits related to resource acquisition and growth, then calculated community weighted trait means and five measures of functional diversity. We observed a switch from conservative plant communities in natural habitats to acquisitive in roadside habitats, which was further enhanced by the presence of non-natives. Whereas, plant size economic traits were driven by abiotic characteristics (i.e., elevation and habitat type) rather than non-natives. The presence of non-natives reduced functional diversity, and this reduction was particularly noticeable in roadside habitats. Higher elevations are associated with communities with smaller plants and host lower functional richness. Press disturbance in roadside habitats seems to facilitate the introduction and spread of non-native plants, and likely selects for acquisitive plants, thereby reducing functional diversity. Our models explain three quarters of the variation in global functional traits, and 60-86% of the variation in functional diversity measures. Our results corroborate a growing body of literature showing that non-native plants alter native community structure in plant communities, we extend this to show that functioning is also reduced. We present how these relationships change regionally. Our results provide a baseline for predicting how plant communities respond to the interactive effects of global change drivers.

Abstract/Description

Cirsium arvense is a perennial weedy plant species found in most parts of the temperate world, including mountain ecosystems. In both the native and non-native ranges C. arvense impacts forage production and reduces crop yield. Puccinia punctiformis is a fungal pathogen specific to C. arvense that has been shown to impact its host and is naturalized in the non-native range of C. arvense. However, in the non-native range, P. punctiformis is less common than C. arvense and there is interest in increasing its presence as a biocontrol agent. There is a need to better understand the abiotic factors shaping its distribution in its non-native range. Using data from 197 sites, some intentionally inoculated, across six states in the western USA, this study aimed to 1) identify climate variables important for P. punctiformis presence on C. arvense and model its distribution/climate envelope in the western USA. (2) Assess P. punctiformis along an elevation gradient, and (3) quantify the effect of inoculation with P. punctiformis on C. arvense individuals and patches through time. Mean annual temperature of the driest quarter, and mean annual temperatures were important variables predicting the occurrence of P. punctiformis. Habitat suitability was greatest in mid montane elevations in mountainous regions. Consistent with these findings, we also found that P. punctiformis probability of occurrence increased up to upper range limit of C. arvense. Infection increased with time since inoculation, and as the number of infected stems increased the average C. arvense stem size decreased. We also observed that as P. punctiformis infected stems increased in a patch through time there was an associated decrease in mean C. arvense cover and stem density within the patches, and in those patches where infection was present the negative relationship between native cover and C. arvense stem density was greater. These findings highlight the importance of a niche based perspective when considering use of biocontrol. Niche overlap between the host and pathogen can vary along an elevation gradient, affect population dynamics, and inform intervention opportunities.

Abstract/Description

Altitudinal range shifts due to global warming create novel plant species communities and interactions, which have been shown to be stronger pressures on the autochthonous alpine plant communities than warming itself. However, it seems unlikely that this effect simply stems from the lowland identity of the colonizing species but rather from the morphological and functional characteristics of certain colonizing plant species that render these superior competitors in a warmed alpine environment. To investigate this hypothesis, we performed a full-factorial warming and transplant experiment in four subalpine grassland sites in Southern Norway, using OTCs to warm vegetation plots by ca. 0.8 °C and individual transplants of three lowland species with novel and more competitive trait values compared to the autochthonous alpine vegetation and three lowland species with extant alpine trait values. In the vegetation plots, we monitored the plant community composition as well as the population dynamics of two alpine target species of low competitiveness, Veronica alpina and Sibbaldia procumbens. We found that the overall plant community at the plot-scale increased in richness in the presence of warming and lowland colonizers, irrespective of their traits, as some species became more common while some few, rare species disappeared. For our target alpine species populations, warming alone was positive but the combination of warming with lowland colonizers was detrimental, and especially so with novel traits colonizers. These results point in the direction of a homogenization of alpine vegetation under warming and colonization, leading to a plot-scale increase of richness, and thus masking the disappearance of species which are outcompeted especially by colonizers with novel and more competitive traits.