North Gradient Research Articles

Territory size of wolvesCanis lupus: linking local (Białowieża Primeval Forest, Poland) and Holarctic‐scale patterns

Factors affecting territory size in wolvesCanis lupuswere studied at 2 scales, the local population (Białowieża Primeval Forest (BPF), eastern Poland) and the geographic range of species (literature review from 14 localities in the Holarctic). Four packs of wolves were studied by radio‐tracking in BPF from 1994 to 1999. The annual territories of packs (Minimum convex polygons with 95% of locations) averaged 201 km2(SD 63, range 116–310). Core areas of territories (50% MCP) covered from 14 to 78 km2(mean 35). Territory sizes and core areas both were negatively correlated to the encounter rates of ungulates (mean number of ungulates seen per unit time spent in the forest by human observers). Pack size (3–8 wolves) did not influence territory size. Home ranges of individual wolves from the same pack varied with season as well as the age, sex, and reproductive status of the wolf. Review of literature from North America and Europe (42–66oN), showed that latitude and prey biomass were essential factors shaping the biogeographic variation in wolf territory size. Territories increased with latitude and declined with growing biomass of prey. The analysis showed that latitude acted partly independently of the south–north gradient in prey abundance. At similar standing crop of ungulate biomass (100 kg km−2), wolf territories would average 140 km2at 40oN, 370 km2at 50oN, and 950 km2at 60oN. Pack size was larger at northern latitudes, but the increase did not keep pace with enlargement of territories. Within‐territory density of wolves declined from 2.5–3 wolves 100 km−2at 40–45oN to 0.7 wolves 100 km−2at 60oN. Our analyses documented similarities regarding the role of prey resources in shaping wolf territoriality at the different scales. Furthermore, a macroecological approach revealed additional factors affecting wolf territory size that were not emergent from knowledge of local population.

Shifting N and P limitation along a north-south gradient of mangrove estuaries in South Florida

A multivariate statistical analysis was applied to a 10 year, multiparameter data set in an effort to describe the spatial dependence and inherent variation of water quality patterns in the mangrove estuaries of Ten Thousand Islands – Whitewater Bay area. Principal component analysis (PCA) of 16 water quality parameters collected monthly resulted in five groupings, which explained 72.5% of the variance of the original variables. The ‘‘Organic’’ component (PCI) was composed of alkaline phosphatase activity, total organic nitrogen, and total organic carbon; the ‘‘Dissolved Inorganic N’’ component (PCII) contained NO3 ,N O 2 , and NH4 ; the ‘‘Phytoplankton’’ component (PCIII) was made up of total phosphorus, chlorophyll a, and turbidity; dissolved oxygen and temperature were inversely related (PCIV); and salinity and soluble reactive phosphorus made up PCV. A cluster analysis of the mean and SD of PC scores resulted in the spatial aggregation of the 47 fixed stations into six classes having similar water quality, which we defined as: Mangrove Rivers, Whitewater Bay, Gulf Islands, Coot Bay, Blackwater River, and Inland Waterway. Marked differences in physical, chemical, and biological characteristics among classes were illustrated by this technique. Comparison of medians and variability of parameters among classes allowed large scale generalizations as to underlying differences in water quality in these regions. A strong south to north gradient in estuaries from high N - low P to low N - high P was ascribed to marked differences in landuse, freshwater input, geomorphology, and sedimentary geology along this tract. The ecological significance of this gradient discussed along with potential effects of future restoration plans.

Aluminum dynamics in forest soil waters in Norway

We report on weekly aluminum (Al) concentration measurements in soil water from forested catchments monitored throughout Norway since 1986. Originating in acidification research, and thus accompanied by many other chemical variables, they constitute a comprehensive data set suited for analysis of short- as well as long-term variations in a geographic perspective. The Al time series at 21 sites are characterized by high temporal variability, seasonal behavior, and episodic events with peak values in the range 200–800 μmol/l, mostly caused by sea salts blown inland in storms, with a subsequent release of Al after cation exchange. Despite a clear south–north gradient in possible acidification over Norway, we found no indication of such south–north trends in Al chemistry, neither in mean values, maximum values, nor time trends. We identified two main drivers for variation in Al concentrations. The first one was sea salts, where Al was released to the soil solution after cation exchange. The second driver was high production of DOC, where Al was driven into the soil solution by complexation with DOC. There appears to be little risk for aluminum toxicity to trees in Norwegian forests. Except during occasional episodes, aluminum concentrations generally lay far below the supposed threshold values for toxic effects on Norway spruce, Scots pine and birch. Much dissolved aluminum was non-labile, and thus relatively non-toxic. Although the Ca 2+ / labile Al ratio was often below 1.0, considerable doubt exists as to the applicability of this variable in the field.

Commentary: Seeing the light

Cedric and Frank Garland 1 observed that metropolitan states in the south-west of the US had lower mortality rates from colon cancer in 1959–61, on average ~10 per 100 000 per year ageadjusted in white males, than metropolitan states in the northwest, on average ~15 per 100 000. They reported that the rank order coefficient of correlation between colon cancer mortality and solar irradiance across the metropolitan states was 0.7. It was 0.6 across non-metropolitan states and the same values were obtained when cancer mortality rates for US counties in 1950–69 were used instead of the whole-of-state values. They noted, from broad regional data, that the probably mainly south to north gradient in colon cancer mortality did not appear to correlate well with patterns of dietary meat, fruit, or vegetable intake but acknowledged that its correlationwith solar irradiance might still be due to confounding with some other dietary, behavioural, or, perhaps, genetic factor. Apperly 2 had reported an association between mortality from all cancers and solar irradiance across the states of the US 40 years earlier and suggested ‘it may be possible to reduce our cancer deaths by exposing suitable skin areas to sunlight . . . insufficient to cause skin cancer’. While the Garlands did not acknowledge this work they can be reasonably excused for not having uncovered it. Unsurprisingly, the Garlands advanced the possibility that photolytic production of vitamin D in the skin might explain the correlation between colorectal cancer mortality and solar irradiance. This is the major source of vitamin D for most human populations. They advanced an argument about antiinflammatory effects of calcium (the absorption of which is promoted by vitamin D) in the bowel mucosa and evidence of a protective effect of milk against colon cancer in one US study (milk was and is mandatorily fortified with vitamin D in the US) in support of this possibility. The Garlands and others published papers reporting on correlations in the US between solar irradiance and cancers of the breast, 3 prostate, 4 and ovary 5 over the subsequent decade or so. None of these, or the original paper on colon cancer, initially attracted much attention. Indeed, the International Agency for Research on Cancer’s 1992 monograph on the carcinogenic risk of solar and ultraviolet radiation to humans stated that ‘no adequate data were available to the Working Group’ when referring to all cancers other than skin, lip, and ocular cancers. 6

Geographic Variation in Suicide Rates: Relationships to Social Factors, Migration, and Ethnic History

Geographic variation in suicide rates is thought to be the result of interactions between two major components: the social organization combined with cultural tradition and biological or genetic factors. The present study examined regional patterns of suicide rates in European Russia. Our study looked at ethnic and national formations with respect to suicide patterns. The results indicated that the suicide rates vary greatly among the regions of the Russian Federation, with suicides more common in the northern regions of European Russia than in the south of the country. The south and north gradient of suicide distributions in Russia resemble that of other European countries. Throughout the Middle ages the north and northwest territory of present-day Russia has been an area of intensive interethnic contacts between the Old Slavs, which have colonized this territory, and native people of Finno-Ugrian and Baltic origin. The results indicated that the historical prevalence of the Finno-Ugrian component in the north of the country has possibly led to its higher suicide rate.

Bayesian approach to study the temporal trend and the geographical variation in the risk of type 1 diabetes. The Sardinian Conscript Type 1 Diabetes Registry.

A previous analysis of the Sardinian Conscript Type 1 Diabetes Registry indicated an abrupt increase in the risk for type 1 diabetes (T1D) among Sardinian male cohorts starting from the 1946 one. The aim of this study was to update the point prevalence of T1D among Sardinian male army conscripts aged 18 yr from 1992 to 1997 described in the previous survey and to update its secular trend. It also looked at the geographical distribution of prevalence. All male Italian citizens must appear before the Conscript Board for a clinical examination prior to military service. T1D patients are rejected with T1D listed as the reason. We examined, retrospectively, a total of 83807 Sardinian males aged 18, born between 1 January 1974 and 31 December 1979. They virtually represent the whole Sardinian population of that age and sex. A total of 307 subjects with T1D were identified. T1D point prevalence for the birth cohorts 1974-1979 was 3.66/1000 (95% CI 3.28-4.09). Bayesian analysis of the geographical distribution of prevalence shows the highest rate in the Southern part of the island (Cagliari province) and the lowest in the north-western part (Sassari province). A similar picture was produced by data from the Eurodiab Registry in Sardinia (1989 ongoing). No significant temporal trend of prevalence was seen in the 6 yr examined in the current study; pooling these recent birth cohorts with the previous ones, the increasing trend of prevalence was confirmed. Our data confirmed the South to North gradient of T1D and the progressive increase of T1D risk among males in Sardinia.

A modern pollen–climate calibration set from northern Europe: developing and testing a tool for palaeoclimatological reconstructions

AbstractAims and location The potential of pollen records in quantitative climate reconstructions has been widely debated but seldom tested. Our aim is to develop a pollen–climate transfer function for northern Europe and test its performance and inference power by numerical cross‐validation with modern climate data. Annual mean temperature (Tann) was assessed as the critical climatic variable becauseTannhas a distinct south–north gradient (5.5 to −4.7 °C) in the study region with a corresponding zonal vegetation gradient from the hemiboreal zone in the south to the northern boreal zone in the north.Methods We collected 137 pollen surface samples from small‐ to medium size lakes from southern Estonia to northern Finland. The transfer function forTannwas developed with weighted averaging partial least squares (WA‐PLS) regression. All 102 terrestrial pollen and spore types were included in the calculation sum and all 137 surface samples and all 102 taxa were included in the transfer function. The performance of the WA‐PLS transfer function was evaluated by leave‐one‐out cross‐validation.Results A cross‐validated root mean square error of prediction (RMSEP) of our model is 0.89 °C and the coefficient of determination (r2) between the observed meteorologicalTannvalues and those predicted by the model in leave‐one‐out cross‐validation is 0.88. The RMSEP as a percentage of the gradient length ofTannis 8.8%. These figures indicate high performance statistics for our transfer function compared with other inference models. This is probably because of standardization of our surface‐sampling and pollen‐analytical procedures, careful selection of the surface sample sites with consideration of the relevant pollen source area, the simple patterns of vegetation zones and climate in the study area, and the mostly natural floristic composition of the forests in northern Europe. However, we also demonstrate the limitations of our model in reliably detecting fine‐scale climatic variability.Main conclusions The study shows the strong influence ofTannon modern pollen composition and demonstrates the potential of pollen data for long‐term climate reconstructions in northern Europe. It also provides evidence against simple interpretations of fine‐scale variations in a single climate reconstruction. In particular, our results highlight the importance of careful study design and implementation in the construction of pollen–climate transfer functions.

Are taxonomic details of relevance to ecologists? An example from oncaeid microcopepods of the Red Sea

The marine microcopepod family Oncaeidae in the Red Sea has been the subject of comprehensive ecological studies over the past 15 years, providing for the first time insights into their community structure, vertical distribution and feeding ecology. Owing to taxonomic problems in species identification, however, many of the earlier ecological results were based on provisionally named species or morphotypes. A recent, ongoing taxonomic study of Red Sea Oncaeidae resulted in a considerable increase in the estimated numbers of species, since many of the species had not been described before. The present paper focuses on the potential significance of an improved taxonomic resolution of oncaeids with respect to various ecological aspects in this area, such as indicator species, community analysis and vertical distribution. The progress in our knowledge of the diversity of Red Sea Oncaeidae is summarized, including latest findings on the taxonomy and zoogeography of very small species (<0.5 mm), and the importance of sibling species in the family is pointed out. The south–north gradient in species diversity of Oncaeidae within the Red Sea appears to be greater than previously assumed, since several of the newly described species were restricted to the southern part. The number of endemic species among Red Sea oncaeids is very low, however, most of the new species being also recorded outside the Red Sea. New quantitative data on the abundance and vertical distribution of selected oncaeid siblings obtained during a recent cruise in the northern Red Sea are provided to exemplify the changes in the knowledge of oncaeid community structure attributable to the improved taxonomic resolution. The potential ecological importance of a more differentiated consideration of oncaeid species in marine microcopepod communities is discussed

Prolonged Lag in Population Outbreak of an Invasive Mussel: A Shifting-Habitat Model

Biological invasions pose a great threat to the integrity of natural communities. Some invasive species demonstrate a population explosion shortly after arrival while in other cases a prolonged lag between arrival and population outbreak is evident. This paper describes a case of a prolonged lag and explores the possible mechanism for this lag. The Red Sea mussel Brachidontes pharaonis, a Lessepsian migrant, was first recorded in the Mediterranean seven years after the opening of the Suez Canal in 1869. Since then it spread along the Israeli coast and as far northwest as Sicily. Studies conducted in the late 1970s, when B. pharaonis was still rare, predicted that it would not establish dense populations along the Israeli coast and would not outcompete the indigenous mussel Mytilaster minimus, although it has strong negative effects on survival and growth of the native species. It was attributed to the invader’s low intrinsic rate of increase relative to that of the native species, and to strong density-independent mortality generated by exposure to high wave action and sedimentation. In contrast to these predictions, we found massive formations of B. pharaonis beds after lag of about 120 years. We looked for distributional patterns that may explain this lag and found no south–north gradient but a strong habitat-dependent colonization. Most apparent are dense B. pharaonis mussel beds (density >300 per 100 cm 2 ) on rocky platforms where mussel beds were absent in the past. These platforms lack the vermetid rim that is typical to this formation. In platforms protected by a biogenic rim, sediment accumulation is high and perennial algae flourish. None of the mussel species form beds in such habitats. We suggest that the delayed formation of B. pharaonis beds along the Israeli coast is a consequence of a recent shift in habitat conditions on some platforms. It is possible that receding of the biogenic rim at the edge of these platforms allowed more effective washing, reduced sediment accumulation, and reduced perennial algae cover making platforms more suitable for the mussels. Lower density-independent mortality allowed B. pharaonis to dominate on such platforms over the indigenous species. On beachrock, a habitat previously dominated by M. minimus, we recorded a rapid shift in numerical domination to B. pharaonis (from 1 : 7 to 1.4 : 1 Brachidontes/Mytilaster individuals) over a period of 4 years (1995–1999). This is probably a result of saturation of the habitat by B. pharaonis recruits originating from the established populations on platforms. Salinity changes and a potential genetic shift may also have contributed to the invasive mussel outbreak.

Characterization and comparison of phytoplankton in selected lakes of five Great Lakes area National Parks

Phytoplankton species have been widely used as indicators of lake conditions, and they may be useful for detecting changes in overall lake condition. In an attempt to inventory and monitor its natural resources, the National Park Service wants to establish a monitoring program for aquatic resources in the Great Lakes Cluster National Parks. This study sought to establish baseline information on the phytoplankton and water chemistry of selected lakes in five national parks in a preliminary effort toward establishing a long-term monitoring program. Phytoplankton and water chemistry samples were collected from ten lakes in five national parks over a two-year period. A total of 176 taxa were identified during the study. Northern lakes generally had higher Shannon-Wiener diversity and clustered together in similarity. Lakes exhibited a south to north gradient of many water chemistry variables, with northern lakes having lower hardness, sulfate, turbidity, and temperature and higher dissolved oxygen. Chloride and sulfate concentrations were the variables that best explained variation among phytoplankton in the ten lakes. A monitoring plan will have to incorporate the differences among lakes, but by coordinating the effort, comparisons within and among parks and other regions will prove useful for determining environmental change.

Operational mapping of atmospheric nitrogen deposition to the Baltic Sea

Abstract. A new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been developed. The system is based on the Lagrangian variable scale transport-chemistry model ACDEP (Atmospheric Chemistry and Deposition model), and aims at delivering deposition estimates to be used as input to marine ecosystem models. The system is tested by comparison of model results to measurements from monitoring stations around the Baltic Sea. The comparison shows that observed annual mean ambient air concentrations and wet depositions are well reproduced by the model. Diurnal mean concentrations of NHx (sum of NH3 and NH4+) and NO2 are fairly well reproduced, whereas concentrations of total nitrate (sum of HNO3 and NO3-) are somewhat overestimated. Wet depositions of nitrate and ammonia are fairly well described for annual mean values, whereas the discrepancy is high for the monthly mean values and the wet depositions are rather poorly described concerning the diurnal mean values. The model calculations show that the annual atmospheric nitrogen deposition has a pronounced south--north gradient with depositions in the range about 1.0 T N km-2 in the south and 0.2 T N km-2 in the north. The results show that in 1999 the maximum diurnal mean deposition to the Danish waters appeared during the summer in the algae growth season. For the northern parts of the Baltic the highest depositions were distributed over most of the year. Total deposition to the Baltic Sea was for the year 1999 estimated to 318 kT N for an area of 464 406 km2 equivalent to an average deposition of 684 kg N/km2.

Reconciliation of sea-level observations in the Western North Atlantic during the last glacial cycle

A south to north gradient of increasing marine isotope substage (MIS) 5a (∼80 ka BP) sea level has been recorded across the Caribbean and surrounding region. Relative to present, MIS-5a sea levels range from −19 m to more than +3 m between Barbados, Haiti, the Bahamas, Florida, Bermuda and the US Atlantic Coast. In contrast, no gradient in sea level is observed for the last interglacial period MIS-5e (∼128–118 ka BP) at tectonically stable localities in the same region, with deposits generally lying several metres above present. We demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the Earth to glacial loading and unloading – a fundamental effect that is commonly overlooked in the interpretation of sea-level observations from different locations to define a ‘global sea-level curve’. Furthermore, the observed gradient can be used to place constraints on Earth rheology and is an important indicator of the behaviour of the North American ice sheets during the last glacial cycle.

Ecology and use of arctic fox Alopex lagopus dens in Norway: tradition overtaken by interspecific competition?

Arctic fox Alopex lagopus dens in Norway are mostly large and well-defined structures of great age. Examinations of these dens have been used in surveys of the breeding and population status of the arctic fox in Fennoscandia. In this study, dens all over north Norway and in some parts of south Norway were surveyed ( n=214), and several aspects of den characteristics, localisation and use were recorded. Red fox Vulpes vulpes dens were also recorded whenever found, including red fox use of arctic fox dens (total n=211). Most of the arctic fox dens were of the “classic” type dug out in sandy soil ( n=210). The average number (±1 SD) of open entrances (at least half open) was 27.4±19.0, and the average size was 363.1±288.7 m 2. Regional variation was found in both these measurements, as well as in two variables classifying the vegetation at the den. However, no consistent south–north gradient was found, although the most southern and the most northern regions were extremes in several respects. A positive correlation was found between den size and the number of entrances, as well as between these two variables and the two vegetation variables. For each arctic fox den, height above the tree line, distance to the tree line, distance between arctic fox dens, distance to the nearest red fox den, distance to a main road and distance to other human activity were estimated. Regional variation was found in all these variables, but no consistent south–north gradient. Again, the most southern region deviated most. There were large differences in the proportion of dens used by arctic foxes between the nine regions, with one region outstanding in its production of arctic fox litters and paucity of red foxes. The proportion sum of arctic fox entrances to sum of red fox entrances reliably, but not perfectly, identified the best arctic fox regions. Arctic fox dens that were known to have produced litters at least once during 1980–2001 had about twice as many entrances as dens without pups, were 32% larger and had a more lush vegetation. They were also situated further from a red fox den. Distance to red fox dens and height above the tree line were the most important factors regarding arctic fox use of dens. Thus, the red fox was identified as a threat to the arctic fox population.

Characterization of Legume Cover Crops for Weed Suppression in the Moist Savanna of Nigeria1

Multilocational characterization of selected herbaceous and shrub legumes was carried out over a 3-yr period at lowland and midlatitude sites in the moist savanna agroecological zone in Nigeria where a south–north gradient exists for rainfall, length of growing season, and insolation. One study site each was located in coastal–derived savanna (DS), southern Guinea savanna (SGS), and northern Guinea savanna (NGS). A fourth site was located in the plateau of the NGS. Only one legume cover crop, lablab, produced adequate ground cover and good weed suppression in three locations irrespective of rainfall amount, duration, and distribution. Velvetbean was superior to other legume cover crops in the lowland savanna locations where rainfall exceeded 1,100 mm/yr but not in the plateau of the NGS where rainfall was less than 1,000 mm. Pigeonpea grew luxuriantly and produced canopy cover that effectively suppressed weeds in the DS where rainfall was high. Centurion grew well and suppressed weeds effectively only in the SGS site where rainfall of 1,120 mm was well distributed over a 5-mo period. Sunnhemp grew well and suppressed weeds only in the NGS study sites where rainfall duration was 4 mo and the length of the growing period was short. Weed density was negatively correlated (P < 0.05) with percentage ground cover of those legume cover crops that were effective in weed suppression in all locations. Redundancy analysis revealed significant associations between weed species and cover crops at each of the locations.Nomenclature: Centurion, Centrosema pascuorum Mart. Ex Benth. #3 CENPA; lablab, Lablab purpureus (L.) Sweet # LABPU; pigeonpea, Cajanus cajan (L.) Millsp. # CAJCA; sunnhemp, Crotalaria ochroleuca G. Don # CROOC; velvetbean, Mucuna pruriens (L.) DC. var. utilis (Wright) Burck # MUCPR.Additional index words: Legume ground cover, weed density, weed species composition.Abbreviation: WAP, weeks after planting; DS, coastal–derived savanna; SGS, southern Guinea savanna; NGS, northern Guinea savanna; RDA, redundancy analysis.

Pollen viability of Scots pine ( Pinus sylvestris) in different temperature conditions: high levels of variation among and within latitudes

We examined the viability of pollen in a widely distributed anemophilous species, Scots pine ( Pinus sylvestris L.), along a south–north gradient from 60 up to 69°N in Finland. It was hypothesised that problems in the reproduction cycle of Scots pine in northern marginal areas are partly due to the poor adaptedness of pollen at low temperatures. The pollen was collected directly from the male strobili and germinated in vitro at different temperatures. The results revealed marked variation in pollen viability both among and within latitudes and also among different temperature treatments. A contrast between southern and northern pollen was found in each year: in 1997–1999, southern pollen performed better, but an opposite contrast was observed in 1998. Pollen germination at the smaller temperatures was low across all the study areas, but very good at the highest temperature which was 20 °C. Variation in pollen viability among stands may lead to differential success of pollen of different origin. Variation among years was also high; thus different pollen might be favoured in different years. Finally, the possibility of gene flow from south to north was assessed.

Trends in savanna structure and composition along an aridity gradient in the Kalahari

Abstract. The Kalahari sand sheet occupies 2.5 million ha in southern Africa. It is an area with relatively similar deep aeolian soils, and a strong south to north gradient in rainfall, from 200 to 1000 mm mean annual precipitation (MAP) in the region studied. This provides an excellent basis for gradient studies at the subcontinental scale. This paper briefly reviews the literature on the vegetation of the Kalahari and describes the vegetation structure and composition at 11 new sites. There is a clear gradient in woody plant biomass (as indexed by basal area) from south to north. Above the minimum level of 200 mm MAP, the woody basal area increases at a rate of ca. 2.5 m2.ha‐1 per 100 mm MAP. Mean maximum tree height also increases along the gradient, reaching 20 m at ca. 800 mm MAP. The number of species to contribute &gt; 95% of the woody basal area increases from one at 200 mm to 16 at 1000 mm MAP. Members of the Mimosaceae (mainly Acacia) dominate the tree layer up to 400 mm MAP. They are replaced by either the Combretaceae (Combretum or Terminalia) or Colophospermum mopane of the Caesalpinaceae between 400 and 600 mm MAP, and by other representatives of the Caesalpinaceae above 600 mm MAP. The vegetation is largely deciduous up to 1000 mm MAP, except for species that apparently have access to groundwater, which may be locally dominant above about 600 mm MAP.

Trends in savanna structure and composition along an aridity gradient in the Kalahari

Abstract The Kalahari sand sheet occupies 2.5 million ha in southern Africa. It is an area with relatively similar deep aeolian soils, and a strong south to north gradient in rainfall, from 200 to 1000 mm mean annual precipitation (MAP) in the region studied. This provides an excellent basis for gradient studies at the subcontinental scale. This paper briefly reviews the literature on the vegetation of the Kalahari and describes the vegetation structure and composition at 11 new sites. There is a clear gradient in woody plant biomass (as indexed by basal area) from south to north. Above the minimum level of 200 mm MAP, the woody basal area increases at a rate of ca. 2.5 m2.ha−1 per 100 mm MAP. Mean maximum tree height also increases along the gradient, reaching 20 m at ca. 800 mm MAP. The number of species to contribute > 95% of the woody basal area increases from one at 200 mm to 16 at 1000 mm MAP. Members of the Mimosaceae (mainly Acacia) dominate the tree layer up to 400 mm MAP. They are replaced by ei...

Habitat preferences of red-listed fungi and bryophytes in woodland key habitats in southern Sweden – analyses of data from a national survey

The aim of this study was to identify habitat preferences of red-listedepiphytic and epixylic bryophyte, lichenized and non-lichenized fungi speciesinwoodland key habitats (WKHS) (areas less than 10 ha, where foreststructures indicate occurrence of red-listed species) in southern Sweden. Therelative importance of different groups of environmental factors was assessedwith partial canonical correspondence analysis techniques and across-validationapproach using data from 7196 selected WKHs. Different woody substrates (oldtrees, logs and snags) made up the most important variable group for occurrenceof red-listed species (30% unique explainable variation). Species associatedwith Fagus sylvatica and Picea abieshabitats, but also species associated with Quercus spp.andPopulus tremula habitats showed distinct habitatpreferences. The second most important variable group (16% unique explainablevariation) was geographical location. A west–east gradient was identified, andspecies concentrated to Baltic islands in the east were separated from otherspecies. This gradient, and an identified south–north gradient, probablyreflect differences in temperatures and rainfall between different regions.Among the remaining variable groups, historical land-use, ground conditions andforest stand composition were of similar importance (5–7% uniqueexplainable variation). Traditional management regimes resulting in semi-openforest habitats (leaf harvesting, forest grazing and selective cutting) wereassociated with the occurrence of many species, probably due to differences inmicroclimate between sites of different openness. Furthermore, a groundmoisturegradient extending from species associated with dry sites (mainly lichenizedfungi) to species associated with wet sites (mainly bryophytes), and a nutrientgradient from species associated with nutrient-poor sites to species occurringat nutrient-rich sites, were identified. Thus, conservation measures are neededin a broad spectrum of habitats with different substrates. Also sites withsimilar substrates, but situated in different regions (and climates), or withdifferent ground moisture and nutrient conditions are needed to cover the fullspectrum of habitat conditions suitable for different red-listed bryophytes andfungi.

Patterns in polychaete abundance and diversity from the Madeira Abyssal Plain, northeast Atlantic

Polychaete abundance and diversity patterns from the Madeira Abyssal Plain (MAP) were studied together with data from three other sites on the northeastern Atlantic abyssal plains. Polychaete abundance at MAP was significantly lower than at any of the other sites, including those lying under comparable productivity regimes. Analysis of diversity, using rarefaction and species counts per unit area, suggests that MAP is extremely species poor and shows dominance by a few common species. The MAP site is characterised by a superficial layer of turbidite sediment, and the hypothesis is put forward that the unusual sediment characteristics at MAP have affected macrofaunal abundance over a vast area (>2000 km 2). Analysis of species composition indicates that the MAP site is not faunistically unique; rather it contains a high proportion of widespread, abundant, cosmopolitan species. We suggest that these are the opportunists of the abyssal benthic habitat. Differences in abundance between the other abyssal sites are the result of both productivity and local environmental conditions. Equitability at the other north Atlantic sites is not affected by productivity, although the actual number of species per unit area is affected, showing a south–north gradient.

Distribution and Abundance of Leaf Galling and Foliar Sexual Morphs of Grape Phylloxera (Hemiptera: Phylloxeridae) andVitisSpecies in the Central and Eastern United States

To better understand the host range and factors acting on the population structure of native grape phylloxera, Daktulosphaira vitifoliae (Fitch), Vitis species in 22 central and eastern U.S. states were surveyed for grape phylloxera presence and abundance. Data for frequency of attack and mean number of galled leaves per vine were compared among Vitis species and among six geographic regions defined according to topographic, ecological, and heuristic criteria. Four of the seven Vitis species that were identified had been attacked by grape phylloxera and both the frequency of vines that were attacked and the mean number of galled leaves differed among species and regions. In general, V. riparia (Michaux) and V. vulpina (L.) were attacked more frequently than expected and V. cinerea (Englemann) less than expected. The distributions of three of these species, V. vulpina, V. aestivalis (Michaux), and V. cinerea, were largely overlapping, but the distribution of V. riparia was not. It was found, to the near exclusion of other species in the northern United States, in the region formerly occupied by the Laurentide Icesheet. An increasing south to north gradient in phylloxera abundance was observed. Fourteen per cent of the surveyed vines were attacked in the Gulf Coast, 34% in the Central region, and 66 and 64% in the Northcentral and Northeastern regions. The mean number of galled leaves per vine conformed to this trend. In addition, sexual morphs were produced by apterous gallicolae in galls on V. cinerea but not on other Vitis species. This life cycle variant has previously been described only in the southwest United States. These data will be useful for future molecular phylogeographic studies and in the understanding, evaluation, and deployment of phylloxera resistant germplasm.