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Southern Limit (southern + limit)
Selected AbstractsClimatic limits for the present distribution of beech (Fagus L.) species in the worldJOURNAL OF BIOGEOGRAPHY, Issue 10 2006Jingyun Fang Abstract Aim, Beech (Fagus L., Fagaceae) species are representative trees of temperate deciduous broadleaf forests in the Northern Hemisphere. We focus on the distributional limits of beech species, in particular on identifying climatic factors associated with their present range limits. Location, Beech species occur in East Asia, Europe and West Asia, and North America. We collated information on both the southern and northern range limits and the lower and upper elevational limits for beech species in each region. Methods, In total, 292 lower/southern limit and 310 upper/northern limit sites with available climatic data for all 11 extant beech species were collected by reviewing the literature, and 13 climatic variables were estimated for each site from climate normals at nearby stations. We used principal components analysis (PCA) to detect climatic variables most strongly associated with the distribution of beech species and to compare the climatic spaces for the different beech species. Results, Statistics for thermal and moisture climatic conditions at the lower/southern and upper/northern limits of all world beech species are presented. The first two PCA components accounted for 70% and 68% of the overall variance in lower/southern and upper/northern range limits, respectively. The first PCA axis represented a thermal gradient, and the second a moisture gradient associated with the world-wide distribution pattern of beech species. Among thermal variables, growing season warmth was most important for beech distribution, but winter low temperature (coldness and mean temperature for the coldest month) and climatic continentality were also coupled with beech occurrence. The moisture gradient, indicated by precipitation and moisture indices, showed regional differences. American beech had the widest thermal range, Japanese beeches the most narrow; European beeches occurred in the driest climate, Japanese beeches the most humid. Climatic spaces for Chinese beech species were between those of American and European species. Main conclusions, The distributional limits of beech species were primarily associated with thermal factors, but moisture regime also played a role. There were some regional differences in the climatic correlates of distribution. The growing season temperature regime was most important in explaining distribution of Chinese beeches, whilst their northward distribution was mainly limited by shortage of precipitation. In Japan, distribution limits of beech species were correlated with summer temperature, but the local dominance of beech was likely to be dependent on snowfall and winter low temperature. High summer temperature was probably a limiting factor for southward extension of American beech, while growing season warmth seemed critical for its northward distribution. Although the present distribution of beech species corresponded well to the contemporary climate in most areas, climatic factors could not account for some distributions, e. g., that of F. mexicana compared to its close relative F. grandifolia. It is likely that historical factors play a secondary role in determining the present distribution of beech species. The lack of F. grandifolia on the island of Newfoundland, Canada, may be due to inadequate growing season warmth. Similarly, the northerly distribution of beech in Britain has not reached its potential limit, perhaps due to insufficient time since deglaciation to expand its range. [source] EVIDENCE FOR HISTORICAL INTROGRESSION ALONG A CONTACT ZONE BETWEEN TWO SPECIES OF CHAR (PISCES: SALMONIDAE) IN NORTHWESTERN NORTH AMERICAEVOLUTION, Issue 5 2002Z. Redenbach Abstract Phylogeographic analyses can yield valuable insights into the geographic and historical contexts of contact and hybridization between taxa. Two species of char (Salmonidae), Dolly Varden (Salvelinus malma) and bull trout (S. confluentus) have largely parapatric distributions in watersheds of northwestern North America. They are, however, sympatric in several localities and hybridization and some introgression occurs across a broad area of contact. We conducted a comparative phylogenetic analysis of Dolly Varden and bull trout to gain a historical perspective of hybridization between these species and to test for footprints of historical introgression. We resolved two major Dolly Varden mitochondrial DNA (mtDNA) clades (with 1.4,2.2% sequence divergence between haplotypes) that had different geographical distributions. Clade N is distributed across most of the range of Dolly Varden, from southern British Columbia through to the Kuril Islands in Asia. Clade S had a much more limited distribution, from Washington state, at the southern limit of the Dolly Varden range, to the middle of Vancouver Island. The distribution and inferred ages of the mtDNA clades suggested that Dolly Varden survived the Wisconsinan glaciation in a previously unsuspected refuge south of the ice sheet, and that Dolly Varden and bull trout were probably in continuous contact over most of the last 100,000 years. When bull trout were included in the phylogenetic analysis, however, the mtDNA of neither species was monophyletic: Clade S Dolly Varden clustered within the bull trout mtDNA clade. This pattern was discordant with two nuclear phylogenies produced (growth hormone 2 and rRNA internal transcribed sequence 1), in which Dolly Varden and bull trout were reciprocally monophyletic. This discordance between mtDNA- and nDNA-based phylogenies indicates that historical introgression of bull trout mtDNA into Dolly Varden occurred. Percent sequence divergence within these introgressed Dolly Varden (clade S) was 0.2,0.6%, implying that the introgression occurred prior to the most recent glaciation. Our analysis and other evidence of contact between divergent lineages in northwestern North America strongly suggests that the area may be the site of previously unsuspected suture zones of aquatic biotas. [source] Stream temperature and the potential growth and survival of juvenile Oncorhynchus mykiss in a southern California creekFRESHWATER BIOLOGY, Issue 7 2007DAVID A. BOUGHTON Summary 1.,We asked whether an increase in food supply in the field would increase the ability of fish populations to withstand climate warming, as predicted by certain bioenergetic models and aquarium experiments. 2.,We subsidised the in situ food supply of wild juvenile steelhead (Oncorhynchus mykiss) in a small stream near the species' southern limit. High-quality food (10% of fish biomass per day) was added to the drift in eight in-stream enclosures along a naturally-occurring thermal gradient. 3.,The temperatures during the experiment were well below the upper thermal limit for the species (means of enclosures ranged from 15.1 to 16.5 °C). Food supplements had no discernible effect on survival, but raised mean (± SD) specific growth rate substantially, from 0.038 ± 0.135 in controls to 2.28 ± 0.51 in feeding treatments. Food supplements doubled the variation in growth among fish. 4.,The mean and variance of water temperature were correlated across the enclosures, and were therefore transformed into principal component scores T1 (which expressed the stream-wide correlation pattern) and T2 (which expressed local departures from the pattern). Even though T1 accounted for 96% of the variation in temperature mean and variance, it was not a significant predictor of fish growth. T2 was a significant predictor of growth. The predicted time to double body mass in an enclosure with a large T2 score (cool-variable) was half that in an enclosure with a low T2 score (warm-stable). 5.,Contrary to expectation, temperature effects were neutral, at least with respect to the main axis of variation among enclosures (cool-stable versus warm-variable). Along the orthogonal axis (cool-variable versus warm-stable), the effect was opposite from expectations, probably because of temperature variation. Subtle patterns of temperature heterogeneity in streams can be important to potential growth of O. mykiss. [source] Rapid climate change-related growth decline at the southern range edge of Fagus sylvaticaGLOBAL CHANGE BIOLOGY, Issue 11 2006ALISTAIR S. JUMP Abstract Studies on Fagus sylvatica show that growth in populations toward the southern limit of this species' distribution is limited strongly by drought. Warming temperatures in the Mediterranean region are expected to exacerbate drought where they are not accompanied by increases in precipitation. We studied levels of annual growth in mature F. sylvatica trees over the last half-century in the Montseny Mountains in Catalonia (northeast Spain). Our results show significantly lower growth of mature trees at the lower limit of this species' distribution when compared with trees at higher altitudes. Growth at the lower Fagus limit is characterized by a rapid recent decline starting in approximately 1975. By 2003, growth of mature trees had fallen by 49% when compared with predecline levels. This is not an age-related phenomenon, nor is it seen in comparable populations at higher altitudes. Analysis of climate-growth relationships suggests that the observed decline in growth is a result of warming temperatures and that, as precipitation in the region has not increased, precipitation is now insufficient to ameliorate the negative effects of increased temperatures on tree growth. As the climate-response of the studied forest is comparable with that of F. sylvatica forests in other southern European regions, it is possible that this growth decline is a more widespread phenomenon. Warming temperatures may lead to a rapid decline in the growth of range-edge populations and a consequent retreat of the species distribution in southern Europe. Assessment of long-term growth trends across the southern range edge of F. sylvatica therefore merits further attention. [source] The biogeography of prediction error: why does the introduced range of the fire ant over-predict its native range?GLOBAL ECOLOGY, Issue 1 2007Matthew C. Fitzpatrick ABSTRACT Aim, The use of species distribution models (SDMs) to predict biological invasions is a rapidly developing area of ecology. However, most studies investigating SDMs typically ignore prediction errors and instead focus on regions where native distributions correctly predict invaded ranges. We investigated the ecological significance of prediction errors using reciprocal comparisons between the predicted invaded and native range of the red imported fire ant (Solenopsis invicta) (hereafter called the fire ant). We questioned whether fire ants occupy similar environments in their native and introduced range, how the environments that fire ants occupy in their introduced range changed through time relative to their native range, and where fire ant propagules are likely to have originated. Location, We developed models for South America and the conterminous United States (US) of America. Methods, We developed models using the Genetic Algorithm for Rule-set Prediction (GARP) and 12 environmental layers. Occurrence data from the native range in South America were used to predict the introduced range in the US and vice versa. Further, time-series data recording the invasion of fire ants in the US were used to predict the native range. Results, Native range occurrences under-predicted the invasive potential of fire ants, whereas occurrence data from the US over-predicted the southern boundary of the native range. Secondly, introduced fire ants initially established in environments similar to those in their native range, but subsequently invaded harsher environments. Time-series data suggest that fire ant propagules originated near the southern limit of their native range. Conclusions, Our findings suggest that fire ants from a peripheral native population established in an environment similar to their native environment, and then ultimately expanded into environments in which they are not found in their native range. We argue that reciprocal comparisons between predicted native and invaded ranges will facilitate a better understanding of the biogeography of invasive and native species and of the role of SDMs in predicting future distributions. [source] Diversity, dynamics and reproduction in a community of small mammals in Upper Guinea, with emphasis on pygmy mice ecologyAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Elisabeth Fichet-Calvet Abstract As part of a large survey on reservoirs of Lassa fever in Guinea, three villages were investigated in high endemic zone, close to Sierra Leone border. Biodiversity of the small mammal community is presented in this study through a standardized trapping in houses, cultivations and forest. Identification of the small mammals was based on morphology and by molecular technique for sibling species. Of the 1123 specimens collected in 2003,2005, we identified seventeen species (thirteen Muridae, four Soricidae), leading to high diversity (Shannon index = 1.6,1.8) and high equitability (evenness index = 0.7,0.8) in cultivations and forest. In houses conversely, the rodent community was dominated by Mastomys natalensis (95,98%), leading to low diversity and equitability. Dynamics and reproduction were investigated in two species of pygmy mice, Mus mattheyi and Mus minutoides, two species of Praomys, P. daltoni and P. rostratus, and in Mastomys erythroleucus. The pygmy mice were abundant in cultivations in early rainy season, and reproduced from rainy to dry season. Praomys daltoni was also found more abundant in cultivations and seemed to reproduce between rainy and dry season, whereas P. rostratus preferred forest and cultivations in late rainy season, and reproduced throughout the year. Finally, M. erythroleucus was more abundant in forest in dry season, and seemed to reproduce from late rainy to dry season. This species had a low occurrence (6.5%) in the Faranah's zone, and probably lived at its southern limit in Guinea. The presence of other Murinae, such as M. natalensis, Praomys spp as possible competitors in the same habitats, is discussed. For the first time, this study relates population biology of pygmy mice with molecular identification. Résumé Dans le cadre d'une vaste étude des réservoirs de la fièvre de Lassa en Guinée, trois villages ont étéétudiés dans une zone de forte endémie près de la frontière de la Sierra Leone. La biodiversité de la communauté de petits mammifères est présentée dans cette étude grâce à un piégeage standardisé dans les maisons, les cultures et les forêts. L'identification des petits mammifères est réalisée sur la base de leur morphologie et de techniques moléculaires dans le cas d'espèces jumelles. Parmi les 1123 spécimens récoltés de 2003 à 2005, nous avons identifié dix-sept espèces (treize Muridae, quatre Soricidae), indiquant une grande diversité (Indice de Shannon = 1,6 à 1,8) et une grande équitabilité (indice d'équitabilité = 0,7 à 0,8) dans les cultures et les forêts. Dans les maisons en revanche, la communauté de rongeurs était dominée par Mastomys natalensis (95 à 98%), conduisant à une faible diversité et équitabilité. La dynamique et la reproduction de deux espèces de souris naines, Mus mattheyi et M. minutoides, deux espèces de Praomys, P. daltoni et P. rostratus, et de Mastomys erythroleucus ont étéétudiées également. Les souris naines étaient abondantes dans les cultures au début de la saison des pluies, se reproduisant de la saison des pluies à la saison sèche. Praomys daltoni fut aussi trouvé en plus grand nombre dans les cultures et semblait se reproduire entre la saison des pluies et la saison sèche alors que P. rostratus préférait les forêts et les cultures à la fin de la saison des pluies et se reproduisait toute l'année. Enfin, M. erythroleucusétait plus abondant en forêt en saison sèche et semblait se reproduire de la fin de la saison des pluies à la saison sèche. Cette espèce était peu présente (6,5%) dans la zone de Faranah et était probablement en Guinée à la limite sud de son aire de répartition. La présence d'autres Murinae, comme M. natalensis et Praomys spp. est discutée en tant que compétiteurs possibles dans les même habitats. Pour la première fois, cette étude relate la biologie des populations de souris naines grâce à une identification moléculaire. [source] Degradation of permafrost in the Xing'anling Mountains, northeastern ChinaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2007Huijun Jin Abstract Permafrost in the Da and Xiao Xing'anling Mountains in northeastern China is warm, thin and sensitive to climatic warming. In the 1970s, the southern limit of permafrost (SLP) was empirically correlated to the ,1 to 0°C isotherms of mean annual air temperature (MAAT) in the western part of the Da Xing'anling Mountains, to about 0°C in the northern part of the Songnen Plain, and to 0 to +1°C in the eastern part of the Xiao Xing'anling Mountains. Climate warming and deforestation have led to permafrost degradation as shown by deepening of the active layer, thinning permafrost, rising ground temperatures, expanding taliks and the disappearance of permafrost patches. The present position of the SLP was estimated using the ,1.0 to +1.0°C MAAT isotherms for 1991,2000. Compared to the SLP in the 1970s, areas of sporadic discontinuous and isolated patchy permafrost have decreased by 90,000,100,000,km2, or 35,37% of their total areal extent (260,000,270,000,km2) in the 1970s. Recent field observations along the Hei'he to Bei'an Highway, the proposed Mo'he to Daqing Crude Oil Pipeline route and the Hai'lar to Daqing Highway confirm these changes. Continuing northward shifting of the SLP is likely to occur during the next 40,50 years under a warming of 1.0,1.5 °C, reducing the permafrost areal extent to an estimated 35% of that in the 1970s and 1980s. Copyright © 2007 John Wiley & Sons, Ltd. [source] Thermal-contraction-crack networks as evidence for late-Pleistocene permafrost in Inner Mongolia, ChinaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2004J. Vandenberghe Abstract Numerous wedges on the Ordos Plateau show typical characteristics of periglacial sand wedges that enable them to be distinguished from desiccation cracks in clayey illuviation soil horizons. The sand wedges are organized in two generations of polygonal networks. The older generation is a large-scale network with a diameter of 8 to 9,m and wedge depths up to more than 2,m. The younger generation has a mean diameter of 3 to 4,m and is formed within the large networks. It consists of shallow (0.6 to 1,m deep) but relatively wide wedges. In contrast to the typical sand wedges that form within continuous permafrost, the shallow wedges formed probably as ,ground wedges' by seasonal freezing. Ice wedges and cryoturbations developed only rarely, and exclusively in the most humid areas. Thermal-contraction cracking occurred mainly between 26 and 20,ka BP, indicating mean annual temperatures at least 13°C lower than present. Before and after that period mean annual temperatures were at least 7 to 8.5° lower than today. The presence of these periglacial phenomena show that the southern limit of continuous permafrost in Inner Mongolia occurred south of 38°N during the Last Glacial Maximum. Copyright © 2004 John Wiley & Sons, Ltd. [source] Habitat fragmentation and population size of the black and gold howler monkey (Alouatta caraya) in a semideciduous forest in Northern ArgentinaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 9 2007Gabriel E. Zunino Abstract A population of black and gold howler monkeys (Alouatta caraya) living near the southern limit of its distribution in a semideciduous forest located in northern Argentina was studied in 2003 to evaluate the possible effects of habitat fragmentation , owing to logging , on its density and social organization within it. Aerial photographs taken in 1982, 1992, and 2001 were used to compare maps of vegetation. These maps were used to evaluate changes in the area covered by forest fragments. From March to June 2003, 10-day monthly surveys of howlers were made in each fragment. A total of 232 individual howlers were counted, belonging to 34 groups plus a solitary adult female. Groups ranged from 2 to 19 individuals (mean = 6.82, SD = 4.23), and 21% of the groups contained more than one adult male. Adults accounted for 55% of the individuals, immatures for 45%, and infants represented 13% of the total. Data obtained were compared with information available for the same population for 1982 and 1995. Results revealed no significant changes in the area of fragments, the crude and ecological density of howlers, and group composition. Group sizes and group composition of howlers suggest that the population remained stable over the past 22 years. The density, number of groups, and individuals appears not to be affected by fragmentation and logging, but crude density was low compared with other less-disturbed habitats. The status of the population remains uncertain owing to isolation, and because there are no protected areas to ensure its stability for the future. Am. J. Primatol. 69:966,975, 2007. © 2007 Wiley-Liss, Inc. [source] Ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus)AMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2004Julie Wieczkowski Abstract I investigated the ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus), one of the world's most endangered primates, with the goal of recommending management strategies. I systematically selected 31 forest fragments throughout the mangabey's 60-km distribution along the lower Tana River in southeastern Kenya. Within the 31 fragments, I measured vegetation structure, food abundance, and human forest product use in 107 belt transects, and conducted 370 mangabey surveys. I used a weighted multiple regression analysis to determine whether there was a dependence between the selected forest attributes and the mean number of mangabey groups per fragment. Fragment area and density of trees ,10 cm diameter at breast height (DBH) were the only variables that significantly correlated with the variation in mangabey abundance. No additional variables were significant when the analysis was limited to forest fragments inside the Tana River Primate National Reserve (TRPNR) or to fragments outside the TRPNR. When I estimated the resources available before recent human forest product use by adding nonharvested and harvested variables, the total basal area of the top 15 food species became significant. This was only within the TRPNR, however. Management, therefore, should focus on increasing forest area, density of trees ,10 cm DBH, and coverage of food trees throughout the mangabey's distribution. Solutions must be found for the problem of forest clearing, and forest product use must be better managed to protect the habitat of this critically endangered primate. The significance of food abundance only within the TRPNR suggests a need to collect dietary data from mangabey groups in fragments toward the southern limit of the mangabey's distribution, where plant species composition differs from that in fragments in which dietary data have been previously collected. Am. J. Primatol. 63:125,138, 2004. © 2004 Wiley-Liss, Inc. [source] Survival rates for a declining population of bottlenose dolphins in Doubtful Sound, New Zealand: an information theoretic approach to assessing the role of human impactsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009Rohan J. C. Currey Abstract 1.The bottlenose dolphins of Doubtful Sound, New Zealand are a declining population at the southern limit of the species' range, exposed to impacts from tourism and habitat modification. Patterns in apparent annual survival were analysed from photographic resightings of naturally marked adults (1990 to 2008) and calves within the first year of life (1994 to 2008) using capture-recapture models. 2.The most parsimonious model for adults provided a time-invariant, sex-invariant estimate of survival (,a(1990,2008)=0.9374; 95% CI: 0.9170,0.9530), marginally lower than prior estimates for wild bottlenose dolphins. 3.The most parsimonious model for calves indicated a significant time-variant decline in survival from an estimate similar to other populations (,c(1994,2001)=0.8621; 95% CI: 0.6851,0.9473) to a current estimate that is, to our knowledge, the lowest recorded for free-ranging bottlenose dolphins (,c(2002,2008)=0.3750; 95% CI: 0.2080,0.5782). 4.Information theoretic evidence ratios suggested that observed patterns in calf survival were 22 times more likely to be explained by a decline coincident with the opening of a second tailrace tunnel for a hydroelectric power station than by a decline in any other year or across multiple years. 5.Projections using an age-structured stochastic population model indicated that the current level of calf survival was unsustainable (population decline: 100% of model runs; population extinction: 41.5% of model runs) and was a key factor in the observed population decline in Doubtful Sound. Copyright © 2008 John Wiley & Sons, Ltd. [source] Reproduction biology of pikeperch (Sander lucioperca (L.)) , a reviewECOLOGY OF FRESHWATER FISH, Issue 2 2003J. Lappalainen Abstract,,, The present review focuses on the reproduction biology of pikeperch (Sander lucioperca (L.)). Aspects like maturity, fecundity, spawning migrations, spawning habitats, onset of spawning, and development time of eggs were reviewed. The onset of maturity is reached at younger age in southern than northern populations due to higher growth rate in the south. Males mature at smaller size and are on average younger than females. Absolute fecundity is closely related to the length and weight, but no clear relationship could be found between relative fecundity and length. Statistically significant relationships were found between the onset of spawning and latitude, and between the duration of the development time of eggs and stable water temperature. Near the southern limits of distribution, the onset of spawning is in February while near the northern limits it is in June. The interannual variability in fecundity and in the onset of maturity and further the factors affecting them have not been studied much. Furthermore, it is not known whether these variations could affect the population dynamics of pikeperch. Little is also known about the actual spawning behaviour of pikeperch in natural habitats. This is probably due to the typical spawning habitats located at 1,3 m depth in waters with high turbidity and low visibility. Even though the homing behaviour to the same spawning areas is well developed in adults, it is not known whether the adults were actually born in the same area. [source] The distribution of South American galaxiid fishes: the role of biological traits and post-glacial historyJOURNAL OF BIOGEOGRAPHY, Issue 1 2004Víctor Cussac Abstract Aim, The aim of this work is to update the distribution data of Galaxiidae in South America, relating extant distribution to physiological and reproductive characteristics of the species, latitude, temperature, and post-glacial opportunities for colonization. Location, Lakes and rivers of Patagonia. Methods, We compared, and eventually reconsidered, general data about distribution based on the original literature about capture sites, incorporating several published and unpublished data to the analysis of the biological traits and distribution of Galaxiidae. Results, The more consistent issue in the comprehension of galaxiid biogeography in South America is the ability to establish landlocked populations. Different founding events in landlocked populations of Galaxias maculatus suggest the possible existence of older and younger landlocked populations. This difference in the time since the establishment of lacustrine populations could have been expressed in their ability for colonization of post-glacial areas. Galaxias maculatus, Aplochiton and Brachygalaxias are more clearly excluded from the post-glacial area than G. platei. For all the species we could note a more abundant record of lake populations at the area of glacial refuges. It could be noted that the most successful species, Galaxias platei, is a specialized deep bottom dweller. Deep bottom dwelling helps to endure winter constraints and it appears to be an alternative to the colonization of the littoral and limnetic zones of post-glacial lakes, the prefered habitat of the other Patagonian fish species. Main conclusions, At the end of this process of post-glacial colonization, in the beginning of twentieth century, man introduced several salmonid species in Patagonia. In addition, antropogenic actions had its more recent consequences in global warming. Nowadays we were able to observe new localities for Brazilian fishes into the Austral Subregion and expect some changes in the distribution of Galaxiidae. Northern limits for all species and southern limits for landlocked G. maculatus, Brachigalaxias bullocki and Aplochiton zebra, could be displaced southward. Probably, the species less affected by the changes will be G. platei. These predictions could be accurately formulated using the model of B.J. Shuter & J.R. Post (1990) Transactions of the American Fisheries Society119, 314,336, when biological database on these species are completed. [source] | |||||||||||||