Fine-Scale Heterogeneity in Crossover Rate in the garnet-scalloped Region of the Drosophila melanogaster X Chromosome

Homologous recombination affects myriad aspects of genome evolution, from standing levels of nucleotide diversity to the efficacy of natural selection. Rates of crossing over show marked variability at all scales surveyed, including species-, population-, and individual-level differences. Even within genomes, crossovers are nonrandomly distributed in a wide diversity of taxa. Although intra- and intergenomic heterogeneities in crossover distribution have been documented in Drosophila, the scale and degree of crossover rate heterogeneity remain unclear. In addition, the genetic features mediating this heterogeneity are unknown. Here we quantify fine-scale heterogeneity in crossover distribution in a 2.1-Mb region of the Drosophila melanogaster X chromosome by localizing crossover breakpoints in 2500 individuals, each containing a single crossover in this specific X chromosome region. We show 90-fold variation in rates of crossing over at a 5-kb scale, place this variation in the context of several aspects of genome evolution, and identify several genetic features associated with crossover rates. Our results shed new light on the scale and magnitude of crossover rate heterogeneity in D. melanogaster and highlight potential features mediating this heterogeneity.     

Fine-Scale Habitat Selection by Breeding White-Tailed Ptarmigan in Colorado

Species distributions are influenced by climate and topography in alpine ecosystems, yet resource selection studies of alpine species are uncommon. Basic characteristics of habitats used by alpine-endemic white-tailed ptarmigan (Lagopus leucura) have been described to explain foraging behavior, morphology, and survival in many alpine regions; however, there is a lack of information about fine-scale habitat selection for nesting and brood-rearing, particularly in the southern extent of the species’ range. Few studies have tested whether nest and brood-site selection by white-tailed ptarmigan are influenced by fine-scale components such as vegetation and arthropod communities. We assessed these fine-scale habitat characteristics analyzing paired use-available resource selection for nest (n = 61) and brood (n = 54) sites. We used conditional logistic regression for data collected in 2 alpine areas along the Front Range of Colorado, USA, during 2014 and 2015. We evaluated resource selection at larger (patch) and finer (nest site) scales. Nest-site selection at the patch scale was best predicted by cover (%) of forage forbs, rock and gravel, and shrubs. Forage forb cover explained more variation in our top nest model at the patch scale when compared to models with specific vegetation species. Females placed their nests along elevational gradients but more so at lower elevations and selected for less graminoid cover at the nest-site scale. Brood habitat selection at the patch level was influenced by cover (%) of rock and gravel and proximity to shrubs (m). Analysis of a subset of our brood data (n = 34) revealed females selected brood habitat that contained high arthropod abundance (e.g., Cicadellidae) over high vegetation cover, likely as a response to meet dietary requirements of chicks. Our results demonstrate how and where white-tailed ptarmigan are currently selecting these different breeding sites in Colorado's alpine, giving us insight into consequences this alpine-endemic bird may face if their breeding habitat is altered. © 2019 The Wildlife Society.     

Fine-Scale Habitat Associations of Red-Backed Voles in Boreal Mixedwood Stands

Abstract: To provide habitat for late-successional wildlife species, new ecosystem-based forest management practices aim to retain elements of complex stand structure, including live residual trees, dead wood legacies, and advanced regeneration, within managed stands. Predicting the effectiveness of these strategies is a challenge for species whose habitat relationships may involve multiple factors and can vary among sites. For 2 years, we live-trapped a common, late-successional microtine rodent, the southern red-backed vole (Myodes [formerly Clethrionomys] gapperi), in 40 1.4-ha boreal mixedwood sites in Ontario, Canada. Using a neighborhood-scale modeling approach, we related red-backed vole capture locations to spatially referenced measures of overstory trees, shrubs and saplings, downed woody debris (DWD), and forest floor substrate. We further assessed how associations with these features varied with availability of the features within a site and as a function of stand management history. In spring, red-backed voles were associated with trap stations that had, within a 26-m radius, a dense shrub layer, abundant late-decay DWD, coniferous understory and litter, and possibly, understory vegetation associated with moist conditions. Positive associations with shrub cover, late-decay DWD, and a moisture-associated understory were most apparent in sites in which these elements were scarce (e.g., <1,500 stems/ha of hardwood saplings and short shrubs; <0.8% projected ground cover of late-decay DWD). The importance of late-decay DWD; shade-tolerant, coniferous understory composition; and substrate varied depending on a site's management history, with each feature having a strong positive effect in 47–64-year-old stands that were harvested using horse skidding and weaker effects in both 31–40-year-old stands that were clearcut with mechanical skidding and >80-year-old fire-origin stands. Our models of fine-scale habitat relationships for red-backed voles may be useful in establishing structural retention guidelines suitable for wildlife species dependent on late-successional habitat structure. In this regard, retaining abundant DWD and 10–30% live trees at harvest may be effective management strategies for providing favorable habitat conditions at localized scales.     

Fine-Scale Analysis of Mount Graham Red Squirrel Habitat Following Disturbance

ABSTRACT Habitat destruction and degradation are major factors in reducing abundance, placing populations and species in jeopardy. Monitoring changes to habitat and identifying locations of habitat for a species, after disturbance, can assist mitigation of the effects of human-caused or -amplified habitat disturbance. Like many areas in the western United States, the Pinaleño Mountains of southeastern Arizona, USA, have suffered catastrophic fire and large-scale insect outbreaks in the last decade. The federally endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is only found in the Pinaleño Mountains, and to assess effects of forest disturbance on habitat we modeled their potential habitat by identifying characteristics of cover surrounding their centrally defended middens. We classified high-spatial resolution satellite imagery into ground cover classes, and we used logistic regression to determine areas used by squirrels. We also used known midden locations in conjunction with slope, elevation, and aspect to create a predictive habitat map. Squirrels selected areas of denser forest with higher seedfall for midden sites. Among active middens, those in the densest and least damaged forests were occupied in more seasons than those in more fragmented and damaged areas. The future conservation of red squirrels and the return of healthy mature forests to the Pinaleño Mountains will rely on preservation of mixed conifer zones of the mountain and active restoration of spruce-fir forests to return them to squirrel habitat. Our ability to evaluate the spectrum of fine- to coarse-scale disturbance effects (individual tree mortality to area wide boundaries of a disturbance) with high-resolution satellite imagery shows the utility of this technique for monitoring future disturbances to habitat of imperiled species.     

Terrestrial Mammal Occupancy in the Context of Widespread Forest Loss and a Proposed Interoceanic Canal in Nicaragua's Decreasingly Remote South Caribbean Region

Central America is experiencing rapid forest loss and habitat degradation both inside and outside of protected areas. Despite increasing deforestation, the Caribbean region of Nicaragua plays an important role in the survival or extinction of large mammal populations in Central America given that it still retains core areas of habitat for large mammal species. The proposed interoceanic canal project that would bisect the southern half of this Caribbean region represents a new threat that, combined with an advancing agricultural frontier, could affect populations of large mammal species such as jaguars, white-lipped peccaries, and Baird’s tapirs. We used occupancy models to examine the relative occupancy probabilities for an assemblage of terrestrial mammals in the south Caribbean region of Nicaragua to identify current core areas for our study species and conduct a preliminary evaluation of the potential impacts of the proposed interoceanic canal. We modeled a community level distribution of eight species with varying levels of sensitivity to human encroachment and a range of habitat associations. Our model results reveal three priority areas for terrestrial mammal conservation in our study area. The mapped predictions show that the only remaining area of suitable habitat for large mammals in the path of the proposed interoceanic canal is a relatively thin strip of forest that runs along the Caribbean Coast. In light of these findings, we propose five recommendations that will help ensure the conservation of this area of the proposed canal route as suitable habitat for our study species.     

Evolutionary Transitions in the Fossil Record of Terrestrial Hoofed Mammals

In the past few decades, many new discoveries have provided numerous transitional fossils that show the evolution of hoofed mammals from their primitive ancestors. We can now document the origin of the odd-toed perissodactyls, their early evolution when horses, brontotheres, rhinoceroses, and tapirs can barely be distinguished, and the subsequent evolution and radiation of these groups into distinctive lineages with many different species and interesting evolutionary transformations through time. Similarly, we can document the evolution of the even-toed artiodactyls from their earliest roots and their great radiation into pigs, peccaries, hippos, camels, and ruminants. We can trace the complex family histories in the camels and giraffes, whose earliest ancestors did not have humps or long necks and looked nothing like the modern descendants. Even the Proboscidea and Sirenia show many transitional fossils linking them to ancient ancestors that look nothing like modern elephants or manatees. All these facts show that creationist attacks on the fossil record of horses and other hoofed mammals are completely erroneous and deceptive. Their critiques of the evidence of hoofed mammal evolution are based entirely on reading trade books and quoting them out of context, not on any firsthand knowledge or training in paleontology or looking at the actual fossils.     

江苏盐城自然保护区陆生兽类资源调查研究

2005年3月～2007年9月期间,在查阅相关文献的基础上,采用实地涮查与访问调查相结合的方法,对盐城自然保护区的陆,七兽类资源进行了初步调查.报道兽类共31种,分属6日13科.其中有国家重点保护兽类3种:I级1种,Ⅱ级2种;国家保护的有益的或者有重要经济、科学研究价值的陆牛兽类10种;有4种兽类被列入<中国濒危动物红皮书>,1种兽类被列入世界自然保护联盟(IUCN)<濒危物种红色名录>,2种兽类被列入<濒危野生动植物种国际贸易公约>(CITES)附录.对盐城自然保护区陆牛兽类资源的生态分布和保护现状等进行了研究,并分析了该区陆牛兽类资源数量减少的原因,提出了保护和管理对策.     

Occupancy Models of Nesting-Season Habitat Associations of Red-Shouldered Hawks in Central Minnesota

ABSTRACT Red-shouldered hawks (Buteo lineatus) are a species of special conservation concern in much of the Great Lakes region, and apparent population declines are thought to be primarily due to habitat loss and alteration. To evaluate red-shouldered hawk-habitat associations during the nesting season and at the landscape scale, we conducted repeated call-broadcast surveys in central Minnesota, USA, across 3 landscapes that represented a range of landscape conditions as a result of differing management practices. In 2004, we conducted repeated call-broadcast surveys at 131 locations in 2 study areas, and in 2005, we surveyed 238 locations in 3 study areas. We developed models relating habitat characteristics at 2 spatial scales to red-shouldered hawk occupancy and assessed support for these models in an information-theoretic framework. Overall, a small proportion of nonforest (grass, clear-cut area, forest <5 yr old), and a large proportion of mature deciduous forest (>40 yr old), had the strongest association with red-shouldered hawk occupancy (proportion of sites occupied) at both spatial scales. The landscape conditions we examined appeared to contain a habitat transition important to red-shouldered hawks. We found, in predominately forest landscapes, the amount of open habitat was most strongly associated with red-shouldered hawk occupancy, but in landscapes that included slightly less mature forest and more extensive open habitats, the extent of mature deciduous forest was most strongly associated with red-shouldered hawk occupancy. Our results suggested that relatively small (<5 ha) patches of open habitat (clear-cuts) in otherwise forested landscapes did not appear to influence red-shouldered hawk occupancy. Whereas, in an otherwise similar landscape, with smaller amounts of mature deciduous forest and larger (>15 ha) patches of open habitat, red-shouldered hawk occupancy decreased, suggesting a threshold in landscape composition, based on both the amount of mature forest and open area, is important in managing forest landscapes for red-shouldered hawks. Our results show that during the nesting season, red-shouldered hawks in central Minnesota occupy at similar rates landscapes with different habitat compositions resulting from different management strategies and that management strategies that create small openings may not negatively affect red-shouldered hawk occupancy.     

Intramolecular Heterogeneity of the Deoxyribonucleic Acid of Temperate Bacteriophages

Spectral changes accompanying the thermal denaturation of phage deoxyribonucleic acid suggested that λ is not unique in possessing large-scale intramolecular heterogeneity and nucleotide clustering; instead, λ seems to share this property with other enteric phages.     

The Spatial-Temporal Heterogeneity of Understory Light Availability in a Temperate Forest of North China

The spatial-temporal variation of understory light availability has important influences on species diversity and community assembly. However, the distribution characteristics and influencing factors of understory light availability have not been fully elucidated, especially in temperate deciduous, broad-leaved forests. In this study, the understory light availability was monitored monthly (May–October) in a temperate deciduous, broad-leaved forest in Henan Province, China. Differences in the light availability among different months and habitat types were statistically analyzed using Kruskal–Wallis method, respectively. Partial least squares path modeling (PLS-PM) was used to explore the direct and/or indirect effects of stand structure, dominant species and topographic factors on the light environment. Results showed that there were differences in light environments among the four habitat types and during the studied six months. The PLS-PM results showed that the stand structure and the dominant species were negatively correlated with the light environment, and the path coefficient values were −0.089 (P = 0.042) and −0.130 (P = 0.004), respectively. Our result indicated that the understory light availability exhibit a distinct spatial and temporal heterogeneity in temperate deciduous, broad-leaved forest of north China. The characteristics of woody plant community, especially the abundance of one of the dominant plant species, were the important factors affecting the understory light availability.     

The Gut Bacterial Community of Mammals from Marine and Terrestrial Habitats

After birth, mammals acquire a community of bacteria in their gastro-intestinal tract, which harvests energy and provides nutrients for the host. Comparative studies of numerous terrestrial mammal hosts have identified host phylogeny, diet and gut morphology as primary drivers of the gut bacterial community composition. To date, marine mammals have been excluded from these comparative studies, yet they represent distinct examples of evolutionary history, diet and lifestyle traits. To provide an updated understanding of the gut bacterial community of mammals, we compared bacterial 16S rRNA gene sequence data generated from faecal material of 151 marine and terrestrial mammal hosts. This included 42 hosts from a marine habitat. When compared to terrestrial mammals, marine mammals clustered separately and displayed a significantly greater average relative abundance of the phylum Fusobacteria. The marine carnivores (Antarctic and Arctic seals) and the marine herbivore (dugong) possessed significantly richer gut bacterial community than terrestrial carnivores and terrestrial herbivores, respectively. This suggests that evolutionary history and dietary items specific to the marine environment may have resulted in a gut bacterial community distinct to that identified in terrestrial mammals. Finally we hypothesize that reduced marine trophic webs, whereby marine carnivores (and herbivores) feed directly on lower trophic levels, may expose this group to high levels of secondary metabolites and influence gut microbial community richness.     

Impact of Non-Native Terrestrial Mammals on the Structure of the Terrestrial Mammal Food Web of Newfoundland,Canada

The island of Newfoundland is unique because it has as many non-native terrestrial mammals as native ones. The impacts of non-native species on native flora and fauna can be profound and invasive species have been identified as one of the primary drivers of species extinction. Few studies, however, have investigated the effects of a non-native species assemblage on community and ecosystem properties. We reviewed the literature to build the first terrestrial mammal food web for the island of Newfoundland and then used network analyses to investigate how the timing of introductions and trophic position of non-native species has affected the structure of the terrestrial mammal food web in Newfoundland. The first non-native mammals (house mouse and brown rat) became established in Newfoundland with human settlement in the late 15^th and early 16^th centuries. Coyotes and southern red-backed voles are the most recent mammals to establish themselves on the island in 1985 and 1998, respectively. The fraction of intermediate species increased with the addition of non-native mammals over time whereas the fraction of basal and top species declined over time. This increase in intermediate species mediated by non-native species arrivals led to an overall increase in the terrestrial mammal food web connectance and generality (i.e. mean number of prey per predator). This diverse prey base and sources of carrion may have facilitated the natural establishment of coyotes on the island. Also, there is some evidence that the introduction of non-native prey species such as the southern red-backed vole has contributed to the recovery of the threatened American marten. Long-term monitoring of the food web is required to understand and predict the impacts of the diverse novel interactions that are developing in the terrestrial mammal food web of Newfoundland.     

Influences of Multi-Scale Habitat on Metabolism in a Coastal Great Lakes Watershed

Spatial heterogeneity influences ecosystem structure and function across multiple habitat scales. Although primary production and respiration are fundamental to energy cycling in aquatic ecosystems, we know relatively little about how habitat scale influences metabolism. In this study, we adopted a multi-scale habitat approach to evaluate primary production and respiration in a coastal Great Lakes watershed that is experiencing pressure from past, present, and anticipated future human activities. We divided the watershed into five macrohabitats (stream, river, wetland, drowned-river mouth lake, and Great Lake), two mesohabitats (benthic and water column), and four microhabitats (periphytic substrates: sand/sediment, rock, wood, and plant) for evaluation of spatial patterns and synchrony in metabolism. Factors that influenced patterns of metabolism were scale dependent. Algal biomass strongly influenced spatial patterns in metabolism at the meso- and microhabitat scales; greater algal biomass translated to higher areal-specific and lower chlorophyll-specific metabolism at benthic mesohabitat and sand/sediment and rock microhabitats. Benthic metabolism overwhelmed water column metabolism, irrespective of location or time of year. Watershed position was important at the macrohabitat scale, with greater overall metabolism in macrohabitats located lower in the watershed. Average synchrony in metabolism rates was greatest at the macrohabitat scale, suggesting metabolic patterns that are evident at finer scales may become integrated at coarser scales. Our results (1) show that spatial and temporal patterns in metabolism are shaped by factors that are dependent upon habitat scale; (2) highlight the importance of benthic productivity across habitat and season; and (3) suggest that hydrologic connectivity strongly influences ecosystem processes, although physical factors can affect these responses as evidenced by the low levels of synchrony between Lake Michigan and the other macrohabitats.     

Landscape Management of Fire and Grazing Regimes Alters the Fine-Scale Habitat Utilisation by Feral Cats

Intensification of fires and grazing by large herbivores has caused population declines in small vertebrates in many ecosystems worldwide. Impacts are rarely direct, and usually appear driven via indirect pathways, such as changes to predator-prey dynamics. Fire events and grazing may improve habitat and/or hunting success for the predators of small mammals, however, such impacts have not been documented. To test for such an interaction, we investigated fine-scale habitat selection by feral cats in relation to fire, grazing and small-mammal abundance. Our study was conducted in north-western Australia, where small mammal populations are sensitive to changes in fire and grazing management. We deployed GPS collars on 32 cats in landscapes with contrasting fire and grazing treatments. Fine-scale habitat selection was determined using discrete choice modelling of cat movements. We found that cats selected areas with open grass cover, including heavily-grazed areas. They strongly selected for areas recently burnt by intense fires, but only in habitats that typically support high abundance of small mammals. Intense fires and grazing by introduced herbivores created conditions that are favoured by cats, probably because their hunting success is improved. This mechanism could explain why, in northern Australia, impacts of feral cats on small mammals might have increased. Our results suggest the impact of feral cats could be reduced in most ecosystems by maximising grass cover, minimising the incidence of intense fires, and reducing grazing by large herbivores.     

Spatial Heterogeneity in Habitat Quality and Cross-Scale Interactions in Metapopulations

Abstract Integration of habitat heterogeneity into spatially realistic metapopulation approaches reveals the potential for key cross-scale interactions. Broad-scale environmental gradients and land-use practices can create autocorrelation of habitat quality of suitable patches at intermediate spatial scales. Patch occupancy then depends not only on habitat quality at the patch scale but also on feedbacks from surrounding neighborhoods of autocorrelated patches. Metapopulation dynamics emerge from how demographic and dispersal processes interact with relevant habitat heterogeneity. We provide an empirical example from a metapopulation of round-tailed muskrats (Neofiber alleni) in which habitat quality of suitable patches was spatially autocorrelated most strongly within 1,000 m, which was within the expected dispersal range of the species. After controlling for factors typically considered in metapopulation studies—patch size, local patch quality, patch connectivity—we use a cross-variogram analysis to demonstrate that patch occupancy by muskrats was correlated with habitat quality across scales ≤1,171 m. We also discuss general consequences of spatial heterogeneity of habitat quality for metapopulations related to potential cross-scale interactions. We focus on spatially correlated extinctions and metapopulation persistence, hierarchical scaling of source–sink dynamics, and dispersal decisions by individuals in relation to information constraints.