Southwestern Limit Of Distribution Research Articles

Are fibrocement slabs a useful tool for monitoring reptiles? The case of Hierophis viridiflavus in its south-western limit of distribution

Are fibrocement slabs a useful tool for monitoring reptiles? The case of Hierophis viridiflavus in its south-western limit of distribution

Delineating vulnerability to drought using a process-based growth model in Pyrenean silver fir forests

Assessing tree growth patterns and deviations from expected climate baselines across wide environmental gradients is fundamental to determine forest vulnerability to drought. This need is particularly compelling for the southernmost limit of the tree species distribution where hot droughts often trigger forest dieback processes. This is the case of some silver fir (Abies alba) populations located in southwestern Europe (Spanish Pyrenees) which present ongoing dieback processes since the 1980s. We sampled 21 silver fir stands showing different dieback intensity, assessed using defoliation levels, quantified their growth patterns and characterized their responses to climate. Then, we assessed growth deviations from climatic predictions using the process-based Vaganov-Shashkin (VS) growth model. The forests showing most intense dieback, i.e. highest defoliation levels, were mainly located in low-elevation sites of the western Pyrenees. Trees in these stands displayed the lowest growth rates and the highest year-to-year variability in growth and their growth was limited by late-summer evaporative demand. In eastern and central Pyrenees, we detected a mild growth limitation by low soil moisture during the late growing season and positive growth recovery in recent years with respect to a climate baseline. Decreasing growth trajectories were the most common pattern, while rising trends were common in stands with low dieback in eastern and central Pyrenees. Our results portend systematic spatial variability of growth trends across the Pyrenean silver fir populations forming the south-western distribution limit of the species in Europe. Decoupling of growth between eastern and western populations observed in the recent decades suggests contrasting vulnerability to climate change, and more importantly, the decoupling of growth patterns in western clusters could be used as an early-warning signal of impending dieback. Consequently, we foresee future dieback events to have more detrimental effects in the western compared with the eastern Pyrenees.

One hundred years later, resurrection of Tydemania gardineri A. Gepp & E. Gepp (Udoteaceae, Chlorophyta) based on molecular and morphological data

ABSTRACT Tydemania Weber-van Bosse is a genus belonging to the family Udoteaceae (Bryopsidales, Chlorophyta) and currently thought to be monospecific throughout its distribution range in the Indo-Pacific. We tested the assumption that Tydemania is a single species using species delimitation methods, morphological observations and phylogenetic reconstructions of large datasets. Our molecular and morphological data recovered two distinct groups, which we argue are the type species T. expeditionis Weber-van Bosse and T. gardineri A. Gepp & E. Gepp. The latter is currently considered a synonym of the former and we resurrect this name from synonymy. T. gardineri is distinguished morphologically from T. expeditionis by the complete absence of glomeruli, whereas T. expeditionis can have glomeruli and flabella, glomeruli alone, or flabella alone. The two species can also be distinguished by the shape and length of the stalks at the base of the flabellum, the diameter of the main axis and of the flabella siphons at the apices. In addition, they have different geographic distributions, with T. gardineri restricted to the Western Indian Ocean, and T. expeditionis extending from the Red Sea, throughout the Indian Ocean and into the West Pacific, including the Coral Triangle, the Philippines and Japan. From our dataset and literature search, we hypothesize that its south-western distribution limit is in northern Madagascar. Finally, we confirm the synonymization of T. mabahithae with T. expeditionis based on specimens from the type locality of the former and the lack of flabella in several other specimens of T. expeditionis.

Role of geographical provenance in the response of silver fir seedlings to experimental warming and drought.

Changes in climate can alter the distribution and population dynamics of tree species by altering their recruitment patterns, especially at range edges. However, geographical patterns of genetic diversity could buffer the negative consequences of changing climate at rear range edges where populations might also harbour individuals with drought-adapted genotypes. Silver fir (Abies alba Mill.) reaches its south-western distribution limit in the Spanish Pyrenees, where recent climatic dieback events have disproportionately affected westernmost populations. We hypothesized that silver fir populations from the eastern Pyrenees are less vulnerable to the expected changing climate due to the inclusion of drought-resistant genotypes. We performed an experiment under strictly controlled conditions simulating projected warming and drought compared with current conditions and analysed physiology, growth and survival of silver fir seedlings collected from eastern and western Pyrenean populations. Genetic analyses separated eastern and western provenances in two different lineages. Climate treatments affected seedling morphology and survival of both lineages in an overall similar way: elevated drought diminished survival and induced a higher biomass allocation to roots. Increased temperature and drought provoked more negative stem water potentials and increased δ13C ratios in leaves. Warming reduced nitrogen concentration and increased soluble sugar content in leaves, whereas drought increased nitrogen concentration. Lineage affected these physiological parameters, with western seedlings being more sensitive to warming and drought increase in terms of δ13C, nitrogen and content of soluble sugars. Our results demonstrate that, in A. alba, differences in the physiological response of this species to drought are also associated with differences in biogeographical history.

Экологии длиннохвостой неясыти на юго-западной границе своего распространения (Словения)

In Slovenia the Ural Owl ( Strix uralensis) is on its south-western limit of distribution and belongs to the southern subspecies Strix uralensis macroura . Dark coloured owls are characteristic for this subspecies and represent between 5 to 15% of the population. Slovenian breeding population size is estimated at 400 to 700 pairs. The densities of territories ranges between 0.9 to 13.4 territories per 10 km 2 , and the highest are reached in mountain forests of southern Dinaric region. In the forests with dominant deciduous trees, e.g. Beech ( Fagus sylvatica) and Pedinculate Oak ( Quercus robur) , the breeding densities are significantly higher than in the forests with higher proportion of coniferous trees, e.g. Norway Spruce ( Picea abies) . The species does not select specific altitude and throughout Slovenia it occurs between 150 and 1600 m a.s.l. The most of the nest found at natural nest-sites were in tree holes or semi-holes (56%) and at the tree stumps (20%). Nest boxes were occupied less frequently in Slovenia with occupancy rate of 29%. At least in mountain regions breeding begins quite late, between 15 March to 21 June. Average clutch size is 3.3 ± 1.0 eggs per nest. About 80% of all nests are successful raising at least one young. The diet shifts significantly between breeding and non-breeding period due to the seasonality in prey availability. According to the biomass the most important prey in breeding period are mice (Muridae), voles (Arvicollidae) and mole ( Talpa europaea ), but in the non-breeding period voles and dormice (Gliridae) predominate. Large Fat Dormouse ( Glis glis) seems to have very important role in the post-breeding period, but not in the breeding period due to its dormancy. As a large forest-dwelling predator the Ural Owl shapes the raptor community in the forest by excluding mezopredator species, as Tawny Owl ( Strix aluco) , what allows smaller raptors, e.g. Boreal Owl ( Aegolius funereus) to expend their ranges to lower elevations. However, this pattern is not general through the whole Ural Owl range since species ecology and morphology could be regionally quite different, therefore ecological studies from different parts of Ural Owl range are needed.

Uncoupled spatiotemporal patterns of seed dispersal and regeneration in Pyrenean silver fir populations

Silver fir (Abies alba) reaches its southwestern distribution limit (rear edge) in the Pyrenees, where it forms highly fragmented populations threatened by drought-induced die-off. Therefore, we need a better knowledge of regeneration patterns and processes (seed production and dispersal, regeneration niche) of such rear-edge stands to assist their long-term conservation. Seed rain patterns were studied in two structurally contrasting sites: an even-aged pure stand (Las Eras) and an uneven-aged mixed silver fir-beech (Fagus sylvatica) stand (Gamueta) over 8 and 12years, respectively. Seed production experienced a greater synchrony in years of high seed production than when crops were low, suggesting masting behavior in both sites. Seed inverse modeling methods resulted in dispersal curves differing between sites, with estimates of mean dispersal distances of 9.9 and 21.5m for the pure and mixed stands, respectively. Long-term sampling of seed dispersal and production was complemented with an analysis of silver fir regeneration niche. Seed and seedling patterns were spatially uncoupled, emphasizing the relevance of microsite filtering of regeneration. Understory light environment was the main factor explaining seedling emergence and mortality. Our study provides a mechanistic basis and a methodological approach for understanding the colonization ability of Pyrenean rear-edge silver fir stands and similar tree populations.

El complex <i>Euphorbia esula-E. virgata</i> (Euphorbiaceae) al nord-est de la península Ibèrica: precisions corològiques, ecològiques i taxonòmiques

The recent discovery in the north-east of the Iberian Peninsula (southern and central Catalonia) of three populations belonging to the Euphorbia esula–E. virgata complex (Euphorbiaceae) prompted us to conduct a macro- and micromorphological study to ascertain their taxonomic identity. Only two previous records of plants from this complex existed in the area and these were gathered in 1908/1909 (previously identified as E. esula subsp. saratoi ) and in 1930 ( E. esula s. l. ). Our results indicate that all the material examined (both recent and old samples) can be attributed to E. virgata , a taxon whose main distribution area lies in eastern Europe, and whose southwestern distribution limit lies in northeastern Iberian Peninsula. The macromorphological characteristics vary somewhat between populations and some individual plants bear a strong resemblance to forms that are usually referred to E. ×pseudovirgata , a supposed hybrid of E. virgata and E. esula . It is not possible, however, to confirm the presence of this hybrid in the region without further studies. After this study, E. esula subsp. esula should be excluded from Catalonia, Valencia and Aragon. The present-day populations we attribute to E. virgata are highly localized but dense. They are found in herbaceous habitats with clear anthropic influence (abandoned fields and the edges of roads and tracks), on deep, fairly dry soils. These habitats are similar to those typical of E. virgata in eastern and central Europe. It is likely that the populations are temporal and indeed in two of the three recent localities it has been confirmed that they date from after 2005. Current data suggest that this is a non-indigenous species, but in view of the fact that it was detected a century ago, the possibility that it is a rare indigenous species with itinerant populations cannot be ruled out.

Structural and climatic determinants of demographic rates of Scots pine forests across the Iberian Peninsula

The demographic rates of tree species typically show large spatial variation across their range. Understanding the environmental factors underlying this variation is a key topic in forest ecology, with far-reaching management implications. Scots pine (Pinus sylvestris L.) covers large areas of the Northern Hemisphere, the Iberian Peninsula being its southwestern distribution limit. In recent decades, an increase in severe droughts and a densification of forests as a result of changes in forest uses have occurred in this region. Our aim was to use climate and stand structure data to explain mortality and growth patterns of Scots pine forests across the Iberian Peninsula. We used data from 2392 plots dominated by Scots pine, sampled for the National Forest Inventory of Spain. Plots were sampled from 1986 to 1996 (IFN2) and were resampled from 1997 to 2007 (IFN3), allowing for the calculation of growth and mortality rates. We fitted linear models to assess the response of growth and mortality rates to the spatial variability of climate, climatic anomalies, and forest structure. Over the period of approximately 10 years between the IFN2 and IFN3, the amount of standing dead trees increased 11-fold. Higher mortality rates were related to dryness, and growth was reduced with increasing dryness and temperature, but results also suggested that effects of climatic stressors were not restricted to dry sites only. Forest structure was strongly related to demographic rates, suggesting that stand development and competition are the main factors associated with demography. In the case of mortality, forest structure interacted with climate, suggesting that competition for water resources induces tree mortality in dry sites. A slight negative relationship was found between mortality and growth, indicating that both rates are likely to be affected by the same stress factors. Additionally, regeneration tended to be lower in plots with higher mortality. Taken together, our results suggest a large-scale self-thinning related to the recent densification of Scots pine forests. This process appears to be enhanced by dry conditions and may lead to a mismatch in forest turnover. Forest management may be an essential adaptive tool under the drier conditions predicted by most climate models.

Physiological performance of silver-fir ( Abies alba Mill.) populations under contrasting climates near the south-western distribution limit of the species

Silver-fir ( Abies alba Mill.) populations located at the south side of the main Pyrenean axis and Pre-Pyrenees constitute the south-western distribution limit of the species and, therefore, may be responding more noticeably to climate change than those in the centre of the range. The increasing aridity detected in the Pyrenees during the 20th century should affect more negatively the physiological performance of the southernmost silver-fir stand growing under more xeric conditions in comparison with stands growing within the main distribution area under mesic conditions. To evaluate the climatic influence on the performance of silver fir near its distribution limit, we studied several physiological and growth variables in shoots and needles from two silver fir populations located in nearby but climatically contrasting sites: Paco Ezpela (site E) and Gamueta (site G). Site E showed a stronger Mediterranean influence than site G, i.e. the former site was characterized by higher temperatures and leaf-to-air water vapour pressure difference and lower precipitation in summer than the latter site. Silver firs from site E showed lower values of primary and secondary growth, needle length, stomatal conductance, net photosynthesis and photosystem II (PSII) efficiency than individuals from site G. The reduction in net photosynthesis could be ascribed to a low CO 2 availability and to a lower PSII efficiency. We conclude that the physiological differences found between both sites were caused by the more xeric conditions of site E as compared with the more mesic environment in site G. The predicted increase of severe droughts in the southern Pyrenees might cause a decrease in photosynthesis and growth in those silver-fir stands located near the ecological limit of the species.

Genetic differentiation of an endangered capercaillie (Tetrao urogallus) population at the Southern edge of the species range

The low-latitude limits of species ranges are thought to be particularly important as long-term stores of genetic diversity and hot spots for speciation. The Iberian Peninsula, one of the main glacial refugia in Europe, houses the southern distribution limits of a number of boreal species. The capercaillie is one such species with a range extending northwards to cover most of Europe from Iberia to Scandinavia and East to Siberia. The Cantabrian Range, in North Spain, constitutes the contemporary south-western distribution limit of the species. In contrast to all other populations, which live in pure or mixed coniferous forests, the Cantabrian population is unique in inhabiting pure deciduous forests. We have assessed the existence of genetic differentiation between this and other European populations using microsatellite and mitochondrial DNA (mtDNA) extracted from capercaillie feathers. Samples were collected between 2001 and 2004 across most of the current distribution of the Cantabrian population. Mitochondrial DNA analysis showed that the Cantabrian birds form a distinct clade with respect to all the other European populations analysed, including the Alps, Black Forest, Scandinavia and Russia, which are all members of a discrete clade. Microsatellite DNA from Cantabrian birds reveals the lowest genetic variation within the species in Europe. The existence of birds from both mtDNA clades in the Pyrenees and evidence from microsatellite frequencies for two different groups, points to the existence of a Pyrenean contact zone between European and Cantabrian type birds. The ecological and genetic differences of the Cantabrian capercaillies qualify them as an Evolutionarily Significant Unit and support the idea of the importance of the rear edge for speciation. Implications for capercaillie taxonomy and conservation are discussed.

Increasing Aridity is Enhancing Silver Fir Abies Alba Mill.) Water Stress in its South-Western Distribution Limit

Tree populations located at the geographical distribution limit of the species may provide valuable information about the response of tree growth to climate warming across climatic gradients. Dendroclimatic information was extracted from a network of 10 silver-fir (Abies alba) populations in the south-western distribution limit of the species (Pyrenees, NE Iberian Peninsula). Ring-width chronologies were built for five stands sampled in mesic sites from the Main Range in the Pyrenees, and for five forests located in the southern Peripheral Ranges where summer drought is more pronounced. The radial growth of silver-fir in this region is constrained by water stress during the summer previous to growth, as suggested by the negative relationship with previous September temperature and, to a lesser degree, by a positive relationship with previous end of summer precipitation. Climatic data showed a warming trend since the 1970s across the Pyrenees, with more severe summer droughts. The recent warming changed the climate-growth relationships, causing higher growth synchrony among sites, and a higher year-to-year growth variation, especially in the southernmost forests. Moving-interval response functions suggested an increasing water-stress effect on radial growth during the last half of the 20th century. The growth period under water stress has extended from summer up to early autumn. Forests located in the southern Peripheral Ranges experienced a more intense water stress, as seen in a shift of their response to precipitation and temperature. The Main-Range sites mainly showed a response to warming. The intensification of water-stress during the late 20th century might affect the future growth performance of the highly-fragmented A. alba populations in the southwestern distribution limit of the species.

The impact of a needleminer (Epinotia subsequana) outbreak on radial growth of silver fir (Abies alba) in the Aragón Pyrenees: A dendrochronological assessment

Summary We report the first dendrochronological assessment on the effects of the Epinotia subsequana (Lepidoptera: Tortricidae) needleminer on Abies alba forests in the Aragon Pyrenees (northeastern Spain), near the southwestern distribution limit of A. alba. We built local residual ring-width chronologies, in fifteen A. alba stands, using dendrochronological techniques. We found a strong decrease in radial growth in the 20th century, during the 1996–98 period, only at the sites AS (Paco Asieso, 42°39' N, 00°17' W) and DI (Diazas, 42°38' N, 00°06' W). There were previous surveys of E. subsequana outbreaks and fir defoliation, in the studied sites area, in 1995–96. They showed that the radial-growth suppression was caused by E. subsequana. We compared radial growth in the non-defoliated stands with mean regional chronology. The greatest decline in radial growth was in 1996–97. Thus, there was a 1–2 year lag in radial growth suppression following the defoliation. The recovery of radial growth occurred in 1998–99.

New Pteridophyte Records from Missouri

While botanizing a deeply dissected area of La Motte sandstone topography in Ste. Genevieve county in the southeastern portion of the Ozark Mountains, the junior author, in company with Dr. Robert Thorne, of the University of Iowa, discovered nearly fifty plants of Lycopodium obscurum var. dendroideum. The dark green, erect branches stood out in sharp contrast to the pale green color of the thick bed of Sphagnum compactum in which the plants were growing on the upper, shaded, steep slopes of one of the narrow bluff-rimmed sandstone gorges of the headwaters of the River aux Vases. The collection data are: Steyermark 72506, La Motte sandstone bluffs along upper reaches of River aux Vases, T 35 N, R 7 E, west part of sect. 34 and east half of sect. 33, 3?-4 miles northwest of Avon, Ste. Genevieve Co., August 30, 1951. This discovery marks a new southwestern limit of distribution for the species and its variety, hitherto known southwestward to Georgia and Tennessee. The sandstone region in which the discovery was made is famous for its harboring of other eastern and northern relics, such as Lycopodium complanatum var. flabelliforme, Dennstaedtia punctilobula, Goodyera pubescens, and Bryoxiphium norvegicum, which are isolated here at or near their southwestern limits of dispersal. The addition of this species of Lycopodium brings to four the total number of this genus known from Missouri. The others 61