Browsing by Autor "Stephan Halloy"

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Latitudinal and altitudinal patterns of plant community diversity on mountain summits across the tropical Andes
(Wiley, 2016) Francisco Cuesta; Priscilla Muriel; Luis D. Llambí; Stephan Halloy; Nikolay Aguirre; Stephan Beck; Julieta Carilla; Rosa Isela Meneses; Soledad Cuello; Alfredo Grau
The high tropical Andes host one of the richest alpine floras of the world, with exceptionally high levels of endemism and turnover rates. Yet, little is known about the patterns and processes that structure altitudinal and latitudinal variation in plant community diversity. Herein we present the first continental‐scale comparative study of plant community diversity on summits of the tropical Andes. Data were obtained from 792 permanent vegetation plots (1 m 2 ) within 50 summits, distributed along a 4200 km transect; summit elevations ranged between 3220 and 5498 m a.s.l. We analyzed the plant community data to assess: 1) differences in species abundance patterns in summits across the region, 2) the role of geographic distance in explaining floristic similarity and 3) the importance of altitudinal and latitudinal environmental gradients in explaining plant community composition and richness. On the basis of species abundance patterns, our summit communities were separated into two major groups: Puna and Páramo. Floristic similarity declined with increasing geographic distance between study‐sites, the correlation being stronger in the more insular Páramo than in the Puna (corresponding to higher species turnover rates within the Páramo). Ordination analysis (CCA) showed that precipitation, maximum temperature and rock cover were the strongest predictors of community similarity across all summits. Generalized linear model (GLM) quasi‐Poisson regression indicated that across all summits species richness increased with maximum air temperature and above‐ground necromass and decreased on summits where scree was the dominant substrate. Our results point to different environmental variables as key factors for explaining vertical and latitudinal species turnover and species richness patterns on high Andean summits, offering a powerful tool to detect contrasting latitudinal and altitudinal effects of climate change across the tropical Andes.
Mycorrhizal and Dark-Septate Fungi in Plant Roots Above 4270 Meters Elevation in the Andes and Rocky Mountains
(Institute of Arctic and Alpine Research, 2008) Steven K. Schmidt; L. C. Sobieniak-Wiseman; Stacie A. Kageyama; Stephan Halloy; Christopher W. Schadt
Arbuscular mycorrhizal (AM) and dark-septate endophytic (DSE) fungi were quantified in plant roots from high-elevation sites in the Cordillera Vilcanota of the Andes (Perú) and the Front Range of the Colorado Rocky Mountains (U.S.A.). At the highest sites in the Andes (5391 m) AM fungi were absent in the two species of plants sampled (both Compositae) but roots of both were heavily colonized by DSE fungi. At slightly lower elevations (5240–5250 m) AM fungi were present in roots while DSE fungi were rare in plants outside of the composite family. At the highest sites sampled in Colorado (4300 m) AM fungi were present, but at very low levels and all plants sampled contained DSE fungi. Hyphae of coarse AM fungi decreased significantly in plant roots at higher altitude in Colorado, but no other structures showed significant decreases with altitude. These new findings indicate that the altitudinal distribution of mycorrhizal fungi observed for European mountains do not necessarily apply to higher and drier mountains that cover much of the Earth (e.g. the Himalaya, Hindu Kush, Andes, and Rockies) where plant growth is more limited by nutrients and water than in European mountains. This paper describes the highest altitudinal records for both AM and DSE fungi, surpassing previous reported altitudinal maxima by about 1500 meters.
Plant dispersal strategies of high tropical alpine communities across the Andes
(Wiley, 2020) Carolina Tovar; Inga M. Melcher; Buntarou Kusumoto; Francisco Cuesta; A.M. Cleef; Rosa Isela Meneses; Stephan Halloy; Luis D. Llambí; Stephan Beck; Priscilla Muriel
Abstract Dispersal is a key ecological process that influences plant community assembly. Therefore, understanding whether dispersal strategies are associated with climate is of utmost importance, particularly in areas greatly exposed to climate change. We examined alpine plant communities located in the mountain summits of the tropical Andes across a 4,000‐km latitudinal gradient. We investigated species dispersal strategies and tested their association with climatic conditions and their evolutionary history. We used dispersal‐related traits (dispersal mode and growth form) to characterize dispersal strategies for 486 species recorded on 49 mountain summits. Then we analysed the phylogenetic signal of traits and investigated the association between dispersal traits, phylogeny, climate and space using structural equation modelling and fourth‐corner analysis together with RLQ ordination. A median of 36% species in the communities was anemochorous (wind‐dispersed) and herbaceous. This dispersal strategy was followed by the barochory‐herb combination (herbaceous with unspecialized seeds, dispersed by gravity) with a median of 26.3% species in the communities. The latter strategy was common among species with distributions restricted to alpine environments. While trait states were phylogenetically conserved, they were significantly associated with a temperature gradient. Low minimum air temperatures, found at higher latitudes/elevations, were correlated with the prevalence of barochory and the herb growth form, traits that are common among Caryophyllales, Brassicaceae and Poaceae. Milder temperatures, found at lower latitudes/elevations, were associated with endozoochorous, shrub species mostly from the Ericaceae family. Anemochorous species were found all along the temperature gradient, possibly due to the success of anemochorous Compositae species in alpine regions. We also found that trait state dominance was more associated with the climatic conditions of the summit than with community phylogenetic structure. Although the evolutionary history of the tropical Andean flora has also shaped dispersal strategies, our results suggest that the environment had a more predominant role. Synthesis . We showed that dispersal‐related traits are strongly associated with a gradient of minimum air temperatures in the Andes. Global warming may weaken this key filter at tropical alpine summits, potentially altering community dispersal strategies in this region and thus, plant community structure and composition.
Recent Observation of a Proliferation of Ranunculus trichophyllus Chaix. in High-altitude Lakes of the Mount Everest Region: Comment
(Institute of Arctic and Alpine Research, 2007) Anton Seimon; Stephan Halloy; Tracie A. Seimon
The record altitudes at which organisms have been found are widely dispersed in the literature. Because of their anecdotal nature—a record altitude is often discovered by chance, rarely by specifically looking for it—such records often go unpublished, or are buried within publications dealing with wider subjects. However, the distributional limits at which organisms grow (maximum or minimum altitudes as well as other limits) are critical to our understanding of numerous basic biogeographic, ecological and physiological issues (Korner, 1999). With current awareness of global warming, records of maximum altitudes for organisms have taken on an even more pressing importance: variations in the actual maximum altitudes may indicate species responses to warming (Gottfried et al., 2002; Pauli et al., 2001; Parmesan and Yohe, 2003), and fragility of life at maximum altitudes has important management consequences (Halloy, 1989; Korner, 2000). We therefore welcome Lacoul and Freedman’s (2006) observations on Ranunculus trichophyllus at a maximum altitude of 4760 m (4750 m and 4780 m are also specified in the publication) in the Nepal Himalaya, which they quote as the highest altitude from which an aquatic angiosperm has been recorded. The authors consider this to represent a range expansion likely facilitated by climatic warming, given previous record altitudes quoted for the area of only around 4000 m. However, it is worth complementing this information. The recorded altitude is considerably lower than those routinely surpassed by several vascular plants in numerous lakes in the South American Andes from latitudes 13uS to 27uS, and probably elsewhere along the cordillera, too. A few examples from above 4800 m are given here from our own experience and the literature to place the Ranunculus trichophyllus record from Nepal in perspective. Vouchers for the species cited are at LIL herbarium, Tucuman, Argentina; LPB herbarium, La Paz, Bolivia; and CUZ herbarium, Cuzco, Peru. N Cerro Condor, Argentina, 5350–5400 m. On the border between Tucuman and Catamarca province, this lake harbors a dense population of Zanichellia sp. despite being partly ice covered, even in mid-summer (Halloy, 1981, 1983; Kuhn and Rohmeder, 1943). As far as we are aware, this is the highest published record for an aquatic vascular plant. N Lago Sibinacocha, Peru, 4880 m. This large high-altitude lake harbors diverse submerged communities, including Potamogeton, Myriophyllum, Isoetes, and Nitella (an algae but with an almost vascular plant-like life form). Being largely unexplored, it is likely to harbor a number of other species known from lower lakes such as Titicaca. Upward range expansion in this area is being documented for diverse organisms from amphibians to plants (Halloy et al., 2005; Seimon et al., 2007). N High Andean pools and tarns often linked to peat bogs harbor a variety of submerged vascular plants, e.g. Callitriche (4800 m, Sajama, Bolivia), Myriophyllum cf. elatinoides (4600–5244 m), Potamotegon cf. pectinatus (4600–5244 m), and Isoetes spp. (4400–5030 m); the latter three are in the Sibinacocha lake region, Peru. A large number of semi-aquatic vascular plants also characterize these communities (Carex spp., Distichia muscoides, Oxychloe andina, and many more) throughout the Andes, often reaching well above 5200 m. Previously recognized altitudinal limits for other organisms (e.g. clams, amphibians) are also being breached in the Sibinacocha area (Krajick and Peter, 2006; Seimon et al., 2007).
Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming
(Wiley, 2019) Francisco Cuesta; Carolina Tovar; Luis D. Llambí; William D. Gosling; Stephan Halloy; Julieta Carilla; Priscilla Muriel; Rosa Isela Meneses; Stephan Beck; Carmen Ulloa Ulloa
Abstract Aim The climate variability hypothesis (CVH) predicts that locations with reduced seasonal temperature variation select for species with narrower thermal ranges. Here we (a) test the CVH by assessing the effect of latitude and elevation on the thermal ranges of Andean vascular plant species and communities, and (b) assess tropical alpine plants vulnerability to warming based on their thermal traits. Location High tropical Andes. Taxon Vascular plants. Methods Temperature data for 505 vascular plant species from alpine communities on 49 summits, were extracted from 29,627 georeferenced occurrences. Species thermal niche traits (TNTs) were estimated using bootstrapping for: minimum temperature, optimum (mean) temperature and breadth (maximum‐minimum). Plant community‐weighted scores were estimated using the TNTs of their constituent species. CVH was tested for species, biogeographical species groups and communities. Vulnerability to global warming was assessed for species, biogeographical species groups and communities. Results Species restricted to the equator showed narrower thermal niche breadth than species whose ranges stretch far from the equator, however, no difference in niche breadth was found across summits’ elevation. Biogeographical species groups distributed close to the equator and restricted to alpine regions showed narrower niche breadth than those with broader ranges. Community‐weighted scores of thermal niche breadth were positively related to distance from equator but not to elevation. Based on their TNTs, species restricted to equatorial latitudes and plant communities dominated by these species were identified as the most vulnerable to the projected 1.5°C warming, due to a potentially higher risk of losing thermal niche space. Main conclusions Our study confirms that the CVH applies to high tropical Andean plant species and communities, where latitude has a strong effect on the thermal niche breadth. TNTs are identified as suitable indicators of species’ vulnerability to warming and are suggested to be included in long‐term biodiversity monitoring in the Andes.
Two GLORIA long‐term alpine monitoring sites established in New Zealand as part of a global network
(Taylor & Francis, 2006) A. F. Mark; Katharine J. M. Dickinson; Tanja Maegli; Stephan Halloy
Abstract Recent information on climatic warming is reviewed in both the global and New Zealand contexts, with emphasis on the relatively sensitive plants of the alpine zone. Also discussed is the initiation in 2001 of the Global Observation Research Initiative in Alpine Environments (GLORIA) project to establish a long‐term vegetation/environment monitoring network in Europe, using standardised criteria and methods, and which is now being extended to the global level. Two sites (“target regions”) have been selected and established on conservation land in New Zealand, using the standardised procedure. One target region with a single summit is on Mt Burns in the perhumid Fiord Ecological Region, the other with two summits is on the upper slopes of the Pisa Range, the highest in the subcontinental Central Otago Ecological Region. These are briefly characterised in terms of their floras and plant cover, as well as their current temperature (air and soil) environments, based on 2‐year records.
Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciation
(Wiley, 2006) Tracie A. Seimon; Anton Seimon; Peter Daszak; Stephan Halloy; Lisa M. Schloegel; César Aguilar; Preston Sowell; Alex D. Hyatt; Bronwen Konecky; John Simmons
Abstract High‐alpine life forms and ecosystems exist at the limits of habitable environments, and thus, are especially sensitive to environmental change. Here we report a recent increase in the elevational limit of anurans following glacial retreat in the tropical Peruvian Andes. Three species have colonized ponds in recently deglaciated terrain at new record elevations for amphibians worldwide (5244–5400 m). Two of these species were also found to be infected with Batrachochytrium dendrobatidis ( Bd ), an emerging fungal pathogen causally associated with global amphibian declines, including the disappearance of several Latin American species. The presence of this pathogen was associated with elevated mortality rates of at least one species. These results represent the first evidence of upward expansion of anurans to newly available habitat brought about by recent deglaciation. Furthermore, the large increase in the upper limit of known Bd infections, previously reported as 4112 m in Ecuador, to 5348 m in this study, also expands the spatial domain of potential Bd pathogenicity to encompass virtually all high elevation anuran habitats in the tropical Andes.