Habitat selection of resident and non-resident gray wolves: implications for habitat connectivity.

Habitat selection studies facilitate assessing and predicting species distributions and habitat connectivity, but habitat selection can vary temporally and among individuals, which is often ignored. We used GPS telemetry data from 96 Gray wolves (Canis lupus) in the western Great Lakes region of the USA to assess differences in habitat selection while wolves exhibited resident (territorial) or non-resident (dispersing or floating) movements and discuss implications for habitat connectivity. We used a step-selection function (SSF) to assess habitat selection by wolves exhibiting resident or non-resident movements, and modeled circuit connectivity throughout the western Great Lakes region. Wolves selected for natural land cover and against areas with high road densities, with no differences in selection among wolves when resident, dispersing, or floating. Similar habitat selection between resident and non-resident wolves may be due to similarity in environmental conditions, when non-resident movements occur largely within established wolf range rather than near the periphery or beyond the species range. Alternatively, non-resident wolves may travel through occupied territories because higher food availability or lower human disturbance outweighs risks posed by conspecifics. Finally, an absence of differences in habitat selection between resident and non-resident wolf movements may be due to other unknown reasons. We recommend considering context-dependency when evaluating differences in movements and habitat use between resident and non-resident individuals. Our results also provide independent validation of a previous species distribution model and connectivity analysis suggesting most potential wolf habitat in the western Great Lakes region is occupied, with limited connectivity to unoccupied habitat.

Distribution model transferability for a wide-ranging species, the Gray Wolf.

Using existing data can be a reliable and cost-effective way to predict species distributions, and particularly useful for recovering or expanding species. We developed a current gray wolf (Canis lupus) distribution model for the western Great Lakes region, USA, and evaluated the spatial transferability of single-state models to the region. This study is the first assessment of transferability in a wide-ranging carnivore, as well as one of few developed for large spatial extents. We collected 3500 wolf locations from winter surveys in Minnesota (2017-2019), Wisconsin (2019-2020), and Michigan (2017-2020). We included 10 variables: proportion of natural cover, pastures, and crops; distance to natural cover, agriculture, developed land, and water; major and minor road density; and snowfall (1-km res.). We created a regional ensemble distribution by weight-averaging eight models based on their performance. We also developed single-state models, and estimated spatial transferability using two approaches: state cross-validation and extrapolation. We assessed performance by quantifying correlations, receiver operating characteristic curves (ROC), sensitivities, and two niche similarity indices. The regional area estimated to be most suitable for wolves during winter (threshold = maximum sensitivity/specificity) was 106,465 km2 (MN = 48,083 km2, WI = 27,757 km2, MI = 30,625 km2) and correctly predicted 88% of wolf locations analyzed. Increasing natural cover and distance to crops were consistently important for determining regional and single-state wolf distribution. Extrapolation (vs. cross-validation) produced results with the greatest performance metrics, and were most similar to the regional model, yet good internal performance was unrelated to greater extrapolation performance. Factors influencing species distributions are scale-dependent and can vary across areas due to behavioral plasticity. When extending inferences beyond the current occurrence of individuals, assessing variation in ecology such as habitat selection, as well as methodological factors including model performance, will be critical to avoid poor scientific interpretations and develop effective conservation applications. In particular, accurate distribution models for recovering or recovered carnivores can be used to develop plans for habitat management, quantify potential of unoccupied habitat, assess connectivity modeling, and mitigate conflict, facilitating long-term species persistence.

Abiotic Soil Factors and Plant-parasitic Nematode Communities.

A natural community of plant-parasitic nematodes is usually polyspecific. The host plant is the most important driving force in nematode populations, but abiotic factors are important in maintaining the steady state. Nematode communities often separate by abiotic soil factors. In any continuous habitat, including crop plants, generally there is a consistency of the most abundant species, which are largely predictable. Data on single species provide little information about community patterns. Although certain nematode species might be indicators of certain environments, only when we discuss such aspects as diversity and ordination do we relate to communities irrespective of any interactions among component species. Only if plant-parasitic nematodes act independently of each other do autecological studies have validity in polyspecific communities.

Morphometric Variation and Biogeography of Ogwa menzeli and Criconema sphagni.

Morphometrics of Ogma menzeli from woodlands in the Adirondack Mountains of New York State and in Iowa were compared. Specimens from the Adirondacks were significantly greater in mean total body length, stylet length, the b, R, and RV values, body width, and esophagus length than specimens from Iowa. The V value was significantly greater in the Iowa than in the Adirondack specimens. The two populations are considered ecotypes of O. menzeli. Criconema sphagni morphometric measurements differed significantly for the RV value (negative) and V value (positive) relative to elevation in the Adirondacks. There was a positive regression correlation for the RV value of O. menzeli and elevation in the Adirondack Mountains.

Distribution patterns of some criconematinae in different forest associations.

A total of 243 samples from Hemlock-Hardwood, Boreal Forest, and Alpine Tundra associations of New York, Vermont, New Hampshire, and Maine were analyzed for species of Bakernema, Criconema, and Criconemoides and for selected edaphic factors. The Hemlock-Hardwood formation contained 13 species of these genera, but the Boreal Forest and Alpine Tundra contained only Criconema menzeli and Criconemoides sphagni. Criconemoides axeste, C. rusticum, and C. xenoplax were associated primarily with mineral soils that have high pH, low moisture after drainage, and organic matter content of less than 15%. Criconemoides sphagni was associated with organic soils that had low pH, high moisture after drainage, and organic matter content greater than 15%.

Survival and reproduction of some nematodes as affected by muck and organic acids.

Fulvic, humic, acetic, N-bulyric, formic, lactic, and propionic acids were inhibitory to the survival or reproduction of Aphelenchus avenae, Aphelenchoides goodeyi, Helicotylenchus pseudorobustus, Meloidogyne hapla or Xiphinema americanum. Reproduction of H. pseudorobustus and M. hapla significantly increased with increasing amounts of muck added to sand, and with the initial amount of nematode inoculum. All acids except humic and fulvic were lethal, in vitro, to all nematode species tested. When A. goodeyi was treated with fulvic acid, reproduction was reduced significantly when compared with sodium humate or water treatments. Treatment of H. pseudorobustus with fulvic acid (pH 3.5) resulted in a greater reduction in reproduction in soil than did treatment with humic acid (pH 3.5).

Relationships of plant parasitic nematodes to sites in native iowa prairies.

Soil samples were collected from three native Iowa prairies and analyzed for plant paiasitic nematodes and selected soil properties. Sites or nematodes were clustered with similarities related to habitat by a cluster analysis of site by nematode species and of nematodes by site. Some nematodes occurred in a wide range of prairie habitats, whereas others were more restricted. For example, greater numbers of Xiphinema americanum were in the low, well-drained sites than in the low wet sites or upland dry sites. Wet sites contained fewer nematodes than well-drained sites. Well-drained sites contained mainly Tylenchorhynchus maximus, Helicotylenchus pseudorobustus, and X. americanum. Wetter sites contained almost exclusively X. chambersi, H. hydrophilus, Telylenchus joctus, and an undescribed species of Tylenchorhynchus.

Community analyses of plant-parasitic nematodes in the Kalsow Prairie, Iowa.

Twenty-one species of plant-parasitic nematodes were recovered from 15 sites in the Kalsow Prairie, Iowa. Nematode communities were analyzed by prominence and importance values of the nematode species and also by diversity and concentration of dominance. The use of numbers and biomass were compared in indices of diversity and concentration of dominance. Tylenchorhynchus maximns ranked first in mean density/site, prominence value, and importance value, although it was not found as frequently as many other nematodes. Xiphinema americanum and T. maximus were among the dominant nematodes in 11 of 15 sites when biomass was used in the concentration-of-dominance index, but they were dominant in only five sites when numbers were used.

Age structure and community diversity of nematodes associated with maize in iowa sandy soils.

Age structure of nematode populations around maize growing in sandy soils in Iowa was studied at soil depths of 0-15and 15-30 cm for 2 years. Numbers of Longidorus breviannulatus were generally greater at 0-15 cm than at 15-30 cm deep until mid to late season. The decline in numbers of females as the season progressed indicates that fecundity slowed and is evidence of only one generation per year. Peak populations of Pratylenchus scribneri and Xiphinema americanum occurred in late August or early September. Adults of Hoplolaimus galeatus were few in the roots but common in the soil, indicating that fertilization occurred mostly in the soil. Numbers of P. scribneri were generally greater at the lower depth, especially late in the season. Community diversity (H') was less when nematode biomass was used instead of numbers. Numbers of H. galeatus did not decline over the winter. Numbers of L. breviannulatus, P. scribneri, and X. americanum declined significantly over the winter, but not between spring cultivation and planting.

Colonization and Sex Ratios of Pratylenchus alleni in Soybean Roots under Two Soil Moisture Regimes.

Population size and sex ratios of Pratylenchus alleni in soybeans were studied trader two different moisture regimes in Hagener loamy fine sand. Soil moisture was maintained from field capacity to 50% below field capacity in the dry regime and from field capacity to 25% above field capacity in the wet regime. The initial peak of colonization of soybeans by P. alleni was in the top 5-cm of taproot 14 days after seeding. There were more P. alleni per unit length of taproot in the dry than in the wet regime during the first 7 days, and this trend continued in the top 5-cm of the taproot for 21 days. Nematode density was greater in taproots than in fibrous roots. The ratio of males to females recovered from roots was significantly higher in the dry than in the wet regime.

Distribution of selected plant parasitic nematodes relative to vegetation and edaphic factors.

The occurrence of selected plant-parasitic nematodes in the hemlock-hardwood-white pine, boreal forest, tundra, and oak-hickory associations in some northern states was compared. Helicotylenchus platyurus and Xiphinema americanum were not found in the boreal forest and tundra, and occurred infrequently in the hemlock-hardwood-white pine areas. They were found frequently, however, in the oak-hickory forest of Iowa. It is questioned that vegetational differences among the areas account directly for the major differences in nematode occurrence. Presence and absence of nematodes and their numbers in the oak-hickory association were clustered by similarity coefficients by sites and correlated with soil pH, percentage organic matter, percentage sand-silt-clay, and field capacity. Of the soil factors measured, pH gave the strongest correlations with nematode numbers. Xiphinema chambersi was found only in soils with a pH between 4.5 and 6.4 while the largest numbers of H. platyurus, H. pseudorobustus, and X. americanum occurred in soil above pH 6.0.

Plant-parasitic Nematodes in Loess Toposequences Planted with Corn.

Populations of plant-parasitic nematodes in an Iowa cornfield were studied along north- and west-facing toposequences. Samples were collected monthly during the growing season. The greatest biomass for Xiphinema americanum occurred at the footslope on the north face. Paratylenchus microdorus had its greatest biomass at the summit position, generally more in the west- than in the north-facing slope. Pratylenchus spp. in the roots peaked at the toeslope in the north-facing slope, but at the footslope in the west-facing slope. Helicotylenchus pseudorobustus peaked at the backslope and the toeslope along the north- and west-facing slopes, respectively. Diversity, as computed for each plot by the Shannon-Weiner diversity index, was highest at the backslope in both toposequences.

Com yield increases relative to nonfumigant chemical control of nematodes.

Corn yields were measured after application of nematicides in 16 experiments, mostly in medium-to-heavily textured soil, at 12 locations in Iowa during 1973-1976. The average maximum yield increase in plots treated with nematicides was 21% over yields in untreated plots. Yields were correlated negatively with nematode numbers or nematode biomass in nearly all comparisons. Correlations of nematode numbers in the soil with yield averaged -0.56 for Helicotylenchus pseudorobustus, -0.45 for Hoplolaimus galeatus, -0.51 for Pratylenchus spp., and -0.64 for Xiphinema americanum. Correlation coefficients for numbers of nematodes in the roots and yield averaged -0.63 for Pratylenchus spp. and -0.56 H. galeatus. Correlation coefficients for yield and total number of nematodes averaged -0.65 in roots and -0.55 in soils. Negative correlations also were greater for comparisons of yield with total parasitic-nematode biomass than with numbers of individual nematodes of a species or total numbers of parasitic nematodes.

Population Increase of Pratylenchus hexincisus on Corn as Related to Soil Temperature and Type.

Population increase of Pratylenchus hexincisus on corn was tested over 3 months at 15, 20, 25, and 30 C in Marshall silt loam, Clarion silt loam, Buckner coarse sand, and Haig silty clay loam soils. The optimum temperature for increase was 30 C in all soils. The nematode population was significantly larger in Buckner coarse sand than in other soil types at 50 C. The recovered P. hexincisus populations equaled or exceeded initial inoculum levels at the two higher temperatures in Marshall silt loam and Haig silty clay loam and at 30 C in Clarion silt loam and Buckner coarse sand. P. hexincisus required 32,400 heat units in Haig silty clay loam and more than 40,000 heat units in the three other soil types to reach a level that is known to cause significant height and biomass reduction in corn under controlled condition.

Correlations of nematodes and soil properties in soybean fields.

Soil samples from 40 soybean fields were collected in 1967 and 1968 and analyzed for nematodes and soil properties. Correlations o f total nematodes, non-stylet nematodes, Dorylaimoidea (excluding Xiphinema americanum), X. americanum, Helicotylenchus pseudorobustus, Tylenchus spp., Aphelenchus avenae, and other groupings of nematodes were made with pH; percentage sand, silt, and clay; percentage organic matter; cation exchange capacity; saturation percentage, and percentage saturation. Organic matter, pH, and cation exchange capacity were most consistently highly correlated with the nematodes. H. pseudorobustus had the most consistently significant correlations with the soil factors. Correlations of nematodes were with more soil factors and were stronger in a wet than in a dry year. The highest numbers of nematodes were usually found in the lighter soils, except in the loamy sand where moisture probably was limiting. In general, soil moisture levels below 20% saturation were probably limiting for most nematodes studied, except for the dorylaims which survived in large numbers in soils with less than 20% saturation.