Assessing Ecoregional-Scale Habitat Suitability Index Models for Priority Landbirds

ABSTRACT Emerging methods in habitat and wildlife population modeling promise new horizons in conservation but only if these methods provide robust population-habitat linkages. We used Breeding Bird Survey (BBS) data to verify and validate newly developed habitat suitability index (HSI) models for 40 priority landbird species in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions. We considered a species’ HSI model verified if there was a significant rank correlation between mean predicted HSI score and mean observed BBS abundance across the 88 ecological subsections within these Bird Conservation Regions. When we included all subsections, correlations verified 37 models. Models for 3 species were unverified. Rank correlations for an additional 5 species were not significant when analyses included only subsections with BBS abundance >0. To validate models, we developed generalized linear models with mean observed BBS abundance as the response variable and mean HSI score and Bird Conservation Region as predictor variables. We considered verified models validated if the overall model was an improvement over an intercept-only null model and the coefficient on the HSI variable in the model was >0. Validation provided a more rigorous assessment of model performance than verification, and models for 12 species that we verified failed validation. Species whose models failed validation were either poorly sampled by BBS protocols or associated with woodland and shrubland habitats embedded within predominantly open landscapes. We validated models for 25 species. Habitat specialists and species reaching their highest densities in predominantly forested landscapes were more likely to have validated models. In their current form, validated models are useful for conservation planning of priority landbirds and offer both insight into limiting factors at ecoregional scales and a framework for monitoring priority landbird populations from readily available national data sets.     

Can limited dispersal or biotic interaction explain the declining abundance of the whelk,Morula marginalba,at the edge of its range?

The southern range limit of the planktotrophic, intertidal whelk, Morula marginalba, occurs immediately to the north of the south‐east Australian biogeographical barrier and we predict that its range may be limited by dispersal and biotic interactions. The barrier includes several hundred kilometers without suitable habitat and is the convergence zone of major ocean currents. Within the barrier region, along‐shore larval transport is expected to be erratic, with water moving offshore to form long‐lived eddies. Through comparison of central and range edge populations, we test for evidence of recruitment limitation and interspecific competition with the whelk, Haustrum vinosum, which occurs sympatrically at the range edge. We found similar levels of recruitment and allozyme genetic variation within centre and edge populations where H. vinosum was absent, implying that populations are strongly interconnected. Nevertheless, recruitment and abundance of M. marginalba were lower at its extreme range limit, where it occurs with H. vinosum. Indeed, we detected significant inverse correlations between the abundance of these species, although their habitat use was similar and they consumed similar prey. These lines of evidence suggest a restricted recruitment across the barrier limits the range of M. marginalba but emphasize that multiple factors may act to set species range limits. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 849–862.     

Foggy days and dry nights determine crown‐level water balance in a seasonal tropical montane cloud forest

The ecophysiology of tropical montane cloud forest (TMCF) trees is influenced by crown‐level microclimate factors including regular mist/fog water inputs, and large variations in evaporative demand, which in turn can significantly impact water balance. We investigated the effect of such microclimatic factors on canopy ecophysiology and branch‐level water balance in the dry season of a seasonal TMCF in Veracruz, Mexico, by quantifying both water inputs (via foliar uptake, FU) and outputs (day‐ and night‐time transpiration, NT). Measurements of sap flow, stomatal conductance, leaf water potential and pressure–volume relations were obtained in Quercus lanceifolia, a canopy‐dominant tree species. Our results indicate that FU occurred 34% of the time and led to the recovery of 9% (24 ± 9.1 L) of all the dry‐season water transpired from individual branches. Capacity for FU was independently verified for seven additional common tree species. NT accounted for approximately 17% (46 L) of dry‐season water loss. There was a strong correlation between FU and the duration of leaf wetness events (fog and/or rain), as well as between NT and the night‐time vapour pressure deficit. Our results show the clear importance of fog and NT for the canopy water relations of Q. lanceifolia.     

Changes in Ribonuclease Activity of Wheat Plants during Water Stress

RNases from control and water-stressed wheat seedlings were purified by ion exchange chromatography, gel filtration and gel electrophoresis. The enzyme appeared to be identical from both treatments and only one species was found. Subcellular distribution between soluble and particulate fractions was not changed by water stress treatment. Total quantity of RNase per plant was similar in control and water-stressed plants, although since the dry weight of treated plants was less, the activity per gram was significantly higher. Crude homogenates of leaf extracts contained an RNase inhibitor with a greater amount being present in control leaves. No evidence was found to indicate that new types of RNases are synthesized during water stress.     

Assessment of Canada Lynx Research and Conservation Needs in the Southern Range: Another Kick at the Cat

Abstract The ecology of Canada lynx (Lynx canadensis) and their main prey, snowshoe hares (Lepus americanus), is poorly understood in southern Canada and the contiguous United States compared to the boreal forest of Canada and Alaska, USA, where both species are well studied. However, given recent listing of lynx under the Endangered Species Act, accurate understanding of lynx and snowshoe hare ecology and conservation requirements in the United States is a high priority. We critically examined unchallenged perceptions and important research needs related to lynx and hare ecology and conservation at the southern extent of their range. Contrary to popular dogma, lynx do not require old-growth forest for denning, but further research on lynx and hare use of fragmented landscapes at lower latitudes is required. The contention that southern lynx are subject to higher interference or exploitative competition compared to their northern counterparts remains without strong empirical support. Lynx rely more on red squirrels (Tamiasciurus hudsonicus) and possibly other alternate prey at lower latitudes, but hares are the predominant food type for lynx across their range. Southern lynx and hare populations do not exhibit periodic cyclicity, but harvest statistics suggest that lynx abundance in the southern range is highly variable, implying that numerical fluctuations likely are fueled by immigration from Canada. Southern lynx population viability in the absence of ingress is suspect and thus maintaining connectivity with northern areas of occupancy should be a priority. Successful conservation of lynx populations in the contiguous United States will require 1) improved understanding of lynx population and habitat ecology at lower latitudes, 2) protection and management of large tracts of lynx and snowshoe hare habitat, and 3) ensured connectivity between lynx populations at the core and periphery of the species' range. However, in light of the numerous challenges facing conservation of populations of many species at their southern distributional limit, the long-term prognosis for lynx in the southern range currently is uncertain.     

Chemorepellents in Paramecium and Tetrahymena

Although Paramecium has been widely used as a model sensory cell to study the cellular responses to thermal, mechanical and chemoattractant stimuli, little is known about their responses to chemorepellents. We have used a convenient capillary tube repellent bioassay to describe 4 different compounds that are chemorepellents for Paramecium and compared their response with those of Tetrahymena. The classical Paramecium t-maze chemokinesis test was also used to verify that this is a reliable chemorepellent assay. The first two compounds, GTP and the oxidant NBT, are known to be depolarizing chemorepellents in Paramecium but this is the first report of them as repellents in Tetrahymena. The second two compounds, the secretagogue alcian blue and the dye cibacron blue, have not previously been described as chemorepellents in either of these ciliates. Two other compounds, the secretagogue AED and the oxidant cytochrome c, were found to be repellents to Paramecium but not to Tetrahymena. The repellent nature of each of these compounds is not related to toxicity because cells are completely viable in all of them. More importantly, all of these repellents are effective at micromolar to nanomolar concentrations, providing an opportunity to use them as excitatory ligands in future works concerning their membrane receptors and possible receptor operated ion channels.     

Eumelanin and Phaeomelanin Contents of Human Epidermis and Cultured Melanocytes

There are two chemically distinct types of melanin: the red-yellow phaeomelanins and the brown-black eumelanins. While both melanins have been detected in human epidermis and cultured melanocytes, it is unknown how the phaeomelanin/eumelanin ratio in human melanocytes maintained in vitro relates to that in the epidermis from which they were isolated. This study uses high-performance liquid chromatography to quantify the eumelanin and phaeomelanin contents of epidermis and/or cultured melanocytes from 12 Europeans with lightly pigmented skin and 9 non-Europeans with more deeply pigmented skin. Epidermis from non-Europeans contained the highest levels of both eumelanin and phaeomelanin and had the lowest phaeomelanin/eumelanin ratios. In contrast, while cultured melanocytes from non-Europeans also had higher levels of eumelanin and phaeomelanin than melanocytes from Europeans, there was no difference in the phaeomelanin/eumelanin ratios in the two groups. However, the phaeomelanin/eumelanin ratios were higher in the cultured melanocytes than in the corresponding epidermis so that while eumelanin was the predominant melanin in the epidermis, phaeomelanin was the major melanin in the cultured melanocytes. These observations may have important implications for the use of cultured human melanocytes in the study of melanogenesis in man.     

The relationship between land use and physicochemistry, food resources and macroinvertebrate communities in tributaries of the Taieri River, New Zealand: a hierarchically scaled approach

1. The relationship between land use and stream conditions was investigated, including physicochemistry, the availability of primary food resources and species richness, species composition and trophic structure of stream macroinvertebrate communities. The survey involved eight subcatchments of the Taieri River (New Zealand) encompassing reasonably homogeneous examples of four major land uses: native forest, native tussock grassland, plantations of introduced pine and agricultural pasture.
2. Each land use was represented by two subcatchments, each subcatchment by two to four tributaries, and each tributary by two to three sampling sites. These three sampling scales each represent typical designs for stream community studies. By recording responses at all scales, it can be determined explicitly whether the scale of sampling influences interpretation of community structure.
3. Elevation, riffle length, proportion of large substrata in the bed, total phosphorus and alkalinity were significantly related to land use, as were canopy cover and the relative abundance of leaves and wood in the streams. Principal components analysis of invertebrate density data identified nine orthogonal community types, the distributions of two of which were significantly related to land use. The role played by browsers and shredders in the stream community depended on land use.
4. Primary analysis was at the level of the tributary. When it focused on sites within tributaries, more variables were related to land use and at a higher level of significance. This was largely a result of enhanced statistical power due to increased replication. When whole subcatchments were the focus of attention, statistical power was so low, even with six to eleven subsamples to generate overall means, that few significant patterns could be identified. However, the community patterns that were revealed were similar whatever the scale of sampling.     

The relationship between land use and physicochemistry, food resources and macroinvertebrate communities in tributaries of the Taieri River, New Zealand: a hierarchically scaled approach

1. The relationship between land use and stream conditions was investigated, including physicochemistry, the availability of primary food resources and species richness, species composition and trophic structure of stream macroinvertebrate communities. The survey involved eight subcatchments of the Taieri River (New Zealand) encompassing reasonably homogeneous examples of four major land uses: native forest, native tussock grassland, plantations of introduced pine and agricultural pasture.
2. Each land use was represented by two subcatchments, each subcatchment by two to four tributaries, and each tributary by two to three sampling sites. These three sampling scales each represent typical designs for stream community studies. By recording responses at all scales, it can be determined explicitly whether the scale of sampling influences interpretation of community structure.
3. Elevation, riffle length, proportion of large substrata in the bed, total phosphorus and alkalinity were significantly related to land use, as were canopy cover and the relative abundance of leaves and wood in the streams. Principal components analysis of invertebrate density data identified nine orthogonal community types, the distributions of two of which were significantly related to land use. The role played by browsers and shredders in the stream community depended on land use.
4. Primary analysis was at the level of the tributary. When it focused on sites within tributaries, more variables were related to land use and at a higher level of significance. This was largely a result of enhanced statistical power due to increased replication. When whole subcatchments were the focus of attention, statistical power was so low, even with six to eleven subsamples to generate overall means, that few significant patterns could be identified. However, the community patterns that were revealed were similar whatever the scale of sampling.