Rare plants in a Succulent – Nama Karoo ecotone in southern Africa

Phylogenetic patterns, adaptations and conservation status of the rare species flora of a winter–summer rainfall ecotone in southern Africa were investigated to shed light on the species' evolutionary history and conservation requirements. Some 11% (93 species) of the Greater Fish River Canyon Landscape in Namibia were classified as rare species, more than half currently not receiving formal protection in Namibia. The rare species flora does not present a subset of the overall species pool, but a unique assemblage of plant species, over‐represented by members of the family Mesembryanthemaceae, Crassulaceae, Asphodelaceae and Hyacinthaceae. Low growth forms (dwarf leaf‐succulent shrubs, dwarf stem succulents and dwarf deciduous shrubs) as well as bulbs are more common amongst rare species. Multiple factors and processes, likely interlinked, are believed to be responsible for determining the rare species flora, indicating that individual species respond differently to the challenges posed by this arid environment. Some plants are likely remnants of wetter conditions in the past, which have retained viable populations in the mountainous terrain of this landscape, others may have evolved in situ.     

Preliminary Report on the Courtedoux Dinosaur Tracksite from the Kimmeridgian of Switzerland

In 2002 a new dinosaur tracksite was discovered in calcareous laminites of early Late Kimmeridgian age along the future course of the “Transjurane” highway in Courtedoux, Canton Jura, Northern Switzerland. The site has an extraordinary scientific potential, as the laminites, which have been deposited in an intertidal to supratidal environment, contain at least 6 track-bearing levels in a total thickness of about 1 m. The laminites are being systematically excavated by the “Section de paleontologie” over an area of approximately 1500 m². So far the main track level has been uncovered over an area of about 650 m², which reveals 2 trackways of theropods and 17 trackways of sauropods. The sauropod tracks are the smallest known in the Kimmeridgian so far, and the trackways belong to the ichnogenus Parabrontopodus, which has been revealed for the first time in Switzerland. The tracksite belongs to the “Middle Kimmeridgian megatracksite” sensu Meyer (2000), and represents the most important dinosaur tracksite in Switzerland, perhaps with the potential for development into one of the world's largest sauropod tracksites. It will be protected in situ underneath an especially constructed highway-bridge, thus offering opportunities for future research and the development of an interpretative center for education and tourism.     

Co-ordination between xylem anatomy,plant architecture and leaf functional traits in response to abiotic and biotic drivers in a nurse cushion plant

Background and AimsPlants in dry Mediterranean mountains experience a double climatic stress: at low elevations, high temperatures coincide with water shortage during summer, while at high elevations temperature decreases and water availability increases. Cushion plants often act as nurses by improving the microclimate underneath their canopies, hosting beneficiary species that may reciprocally modify their benefactors’ microenvironment. We assess how the nurse cushion plant Arenaria tetraquetra subsp. amabilis adjusts its hydraulic system to face these complex abiotic and biotic constraints.MethodsWe evaluated intra-specific variation and co-ordination of stem xylem anatomy, leaf functional traits and plant architecture in response to elevation, aspect and the presence of beneficiary species in four A. tetraquetra subsp. amabilis populations in the Sierra Nevada mountains, southern Spain.Key ResultsXylem anatomical and plant architectural traits were the most responsive to environmental conditions, showing the highest mutual co-ordination. Cushions were more compact and had smaller, more isolated conductive vessels in the southern than in the northern aspect, which allow minimization of the negative impacts of more intense drought. Only vessel size, leaf mass per area and terminal branch length varied with elevation. Nurse cushions co-ordinated plant architecture and xylem traits, having higher canopy compactness, fewer leaves per branch and fewer, more isolated vessels than non-nurse cushions, which reflects the negative effects of beneficiary plants on nurse water status. In non-nurse cushions, plant architecture co-ordinated with leaf traits instead. The interacting effects of aspect and elevation on xylem traits showed that stress due to frost at high elevation constrained xylem anatomy in the north, whereas stress due to drought had a parallel effect in the south.ConclusionsTrait co-ordination was weaker under more demanding environmental conditions, which agrees with the hypothesis that trait independence allows plants to better optimize different functions, probably entailing higher adjustment potential against future environmental changes.     

Assessing the threat to montane biodiversity from discordant shifts in temperature and precipitation in a changing climate

Mountains are centres of global biodiversity, endemism and threatened species. Elevational gradients present opportunities for species currently living near their upper thermal limits to track cooler temperatures upslope in warming climates, but only if changes in precipitation are sufficiently in step with temperature. We model local population extirpation risk for a range of temperature and precipitation scenarios over the next 100 years for 16 848 vertebrate species populations distributed along 156 elevational gradients. Average population extirpation risks due to warming alone were < 5%, but increased 10-fold, on average, when changes in precipitation were also considered. Under the driest scenarios (minimum predicted precipitation), local extirpation risks increased sharply (50-60%) and were especially worrisome for hydrophilic amphibians and montane Latin America (c. 80%). Realistic assessment of risks urgently requires improved monitoring of precipitation, better regional precipitation models and more research on the effects of changes in precipitation on montane distributions.     

Below-ground response of Norway spruce to climate conditions at Mt. Brocken (Germany)—A re-assessment of Central Europe's northernmost treeline

Alpine treelines at medium high mountains are less abundant and thus have been less frequently studied than at high-elevation mountain ranges of the world. We studied mature Norway spruce stands along an extended elevation transect at Mt. Brocken (Harz Mountains, Central Germany) to analyse the altitudinal changes in climate-related growth conditions, and to evaluate the prevailing climate conditions at the treeline of medium high Mt. Brocken. A particular aim was to analyse the change in fine root biomass partitioning along the transect towards the treeline. Microclimate conditions at the treeline of Mt. Brocken were very similar to other treeline sites worldwide. Tree height and stem biomass strongly decreased from middle elevations towards the treeline. On the contrary, fine root biomass and the ratio of fine root/stem biomass strongly increased towards the treeline indicating a marked shift in carbon allocation in favour of the fine root system with elevation. A meta-analysis of literature data revealed that the elevation-related increase in dry mass partitioning to the fine root system is a general phenomenon for Norway spruce stands in northern and central European mountains. We conclude that the particularly large fine root system of Norway spruce at cold sites represents a mechanism to cope with unfavourable soil conditions such as reduced or temporally variable nutrient supply.     

Changes in aquatic insect emergence in response to whole-lake experimental manipulations of introduced trout

1. Insects emerging from mountain lakes provide an important food source for many terrestrial predators. The amount of insect subsidy that emerges from lakes is influenced by predator composition, but predator effects could be ameliorated by greater habitat complexity. We conducted a replicated whole‐lake experiment to test the effects of introduced fish predators on the abundance and composition of aquatic insects within and emerging from the littoral zone of 16 mountain lakes in the Trinity Alps Wilderness in northwestern California. 2. Study treatments matched the fisheries management options being implemented in California’s wilderness areas: (i) continued stocking with non‐native trout, (ii) suspension of stocking, and (iii) suspension of stocking and removal of fish. We also included four naturally fishless ‘reference’ lakes. We compared abundances and biomass of emerging aquatic insects before treatments were initiated and for 3 years following their establishment. Abundances of benthic insects were also compared in the third year post‐treatment. 3. Trout removal rapidly increased abundances of mayflies, caddisflies, and insect predators, and overall insect biomass emerging from lakes. No significant differences were found between the suspension of stocking lakes and continued stocking lakes. Fish density was a more important predictor of aquatic insect emergence than habitat complexity. 4. Mayfly larvae responded positively to fish removal and caddisfly larvae tended to be more abundant in lakes without fish, but we did not detect effects on abundance of predatory insects. However, we found large insect predators in shallower water in lakes with fish compared to fish removal or fish‐free reference lakes. 5. These results provide insights into the continuing effects of past and current fish stocking practices on the flow of insect prey from mountain lakes into the neighbouring terrestrial environment. We also show that these consequences can rapidly be reversed by removing non‐native fishes.     

Global analysis of bird elevational diversity

Aim Elevational gradients distributed across the globe are a powerful test system for understanding biodiversity. Here I use a comprehensive set of bird elevational gradients to test the main drivers of diversity, including sampling, area, mid‐domain effect, temperature, temperature and water availability, and hypotheses of evolutionary history. Location Seventy‐eight elevational gradients of bird diversity from mountains in both hemispheres spanning 24.5° S to 48.2° N, including gradients from various climates, biogeographical regions and habitat types. Methods Data on bird elevational diversity were taken from the literature. Of the 150 datasets found or compiled, only those with a high, unbiased sampling effort were used in analyses. Datasets sampled all birds, all breeding birds or all forest birds; a few studies detailed seasonal, elevational shifts. Eighteen predictions of diversity theory were tested, including three sets of interactions. Results Birds display four distinct diversity patterns in nearly equal frequency on mountains: decreasing diversity, low‐elevation plateaus, low‐elevation plateaus with mid‐peaks, and unimodal mid‐elevational peaks. Bird elevational diversity strongly supports current climate as the main driver of diversity, particularly combined trends in temperature and water availability. Bird diversity on humid mountains is either decreasing or shows a low‐elevation plateau in diversity, while on dry mountains it is unimodal or a broad, low‐elevation plateau usually with a mid‐elevation maximum. The predictions of sampling, area and mid‐domain effect were not consistently supported globally. The only evolutionary hypothesis with preliminary support was niche conservatism. Main conclusions Both water and temperature variables are needed to comprehensively predict elevational diversity patterns for birds. This result is consistent for breeding and forest birds, for both hemispheres, and for local‐ or regional‐scale montane gradients. More analyses are needed to discern whether the mechanism underlying these relationships is ecological, based on direct physiological limitations or indirect food resource limitations, or historical, based on phylogenetic niche conservation or other evolutionary trends related to climate. The species–area and mid‐domain effects are not supported as primary drivers of elevational diversity in birds.     

Multivariate analysis of morphological variation in Cineraria deltoidea (Asteraceae, Senecioneae)

Cluster analysis and principal coordinates analysis were used to investigate phenetic variation in Cineraria deltoidea , a species that ranges from near sea level in KwaZulu-Natal, South Africa, to 4300 m a.s.l. on the mountains of East Africa and Ethiopia. Earlier taxonomic revisions reduced nine previously recognized species to synonyms of C. deltoidea . Two closely related species, C. decipiens and C. atriplicifolia , were also included in the analyses. Thirty-six morphological characters were examined on 111 specimens. Phenograms and scattergrams show partial clusters of specimens of C. deltoidea from individual mountains or geographical regions, but no groups are sufficiently distinct to warrant formal recognition at any rank. The East African specimens from 3000 m a.s.l. and higher tend to cluster together. Growth at high altitude in East Africa is correlated with fewer, larger capitula on longer peduncles, and an absence of a cobwebby indumentum comprising long, narrow-based trichomes. Cineraria deltoidea is thus a highly variable species with geographical and clinal variation evident throughout its range. Cineraria atriplicifolia and C. decipiens are maintained as distinct species, distinguished from C. deltoidea by their growth form, life span and auricle shape.  © 2007 University of the Witwatersrand, Johannesburg. Journal compilation © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 497–521.     

Declining population trends of European mountain birds

Mountain areas often hold special species communities, and they are high on the list of conservation concern. Global warming and changes in human land use, such as grazing pressure and afforestation, have been suggested to be major threats for biodiversity in the mountain areas, affecting species abundance and causing distribution shifts towards mountaintops. Population shifts towards poles and mountaintops have been documented in several areas, indicating that climate change is one of the key drivers of species’ distribution changes. Despite the high conservation concern, relatively little is known about the population trends of species in mountain areas due to low accessibility and difficult working conditions. Thanks to the recent improvement of bird monitoring schemes around Europe, we can here report a first account of population trends of 44 bird species from four major European mountain regions: Fennoscandia, UK upland, south‐western (Iberia) and south‐central mountains (Alps), covering 12 countries. Overall, the mountain bird species declined significantly (?7%) during 2002–2014, which is similar to the declining rate in common birds in Europe during the same period. Mountain specialists showed a significant ?10% decline in population numbers. The slope for mountain generalists was also negative, but not significantly so. The slopes of specialists and generalists did not differ from each other. Fennoscandian and Iberian populations were on average declining, while in United Kingdom and Alps, trends were nonsignificant. Temperature change or migratory behaviour was not significantly associated with regional population trends of species. Alpine habitats are highly vulnerable to climate change, and this is certainly one of the main drivers of mountain bird population trends. However, observed declines can also be partly linked with local land use practices. More efforts should be undertaken to identify the causes of decline and to increase conservation efforts for these populations.