Hidden phylogeographic complexity in the Sierra Madre Oriental: the case of the Mexican tulip poppy Hunnemannia fumariifolia (Papaveraceae)

Aim A phylogeographic study of the endemic Mexican tulip poppy Hunnemannia fumariifolia (Papaveraceae) was conducted to determine: (1) the historical processes that influenced its geographical pattern of genetic variation; (2) whether isolation by distance was one of the main factors that caused genetic divergence in populations of this species; and (3) whether genetic flow still exists between populations from northern arid zones (Chihuahuan Desert and Sierra Madre Oriental) and those from southern arid zones (Tehuacán‐Cuicatlán Valley) – populations that are separated by the Transvolcanic Belt. Location Xerophytic vegetation in Mexico. Methods Chloroplast DNA (cpDNA) sequences of three regions, trnH‐psbA, rpl32‐trnL(UAG) and ndhF‐rpl32, were obtained for 85 individuals from 17 populations sampled in the field, covering the entire range of H. fumariifolia. The evolutionary history of these populations was investigated using a nested clade phylogeographic analysis and also by conducting various population genetic analyses. Results In total, 17 haplotypes were detected, 14 of which were found in the Sierra Madre Oriental. Differentiation among populations based on cpDNA variation (G_ST = 0.787, SE 0.0614) indicated population structure in H. fumariifolia, corroborated by a fixation index (F_ST) of 0.907. Results from analysis of molecular variance found that most of the total variation (90.71%, P < 0.001) was explained by differences among populations. Three regions were determined based on geological correspondence – the Chihuahuan Desert, Sierra Madre Oriental and Tehuacán‐Cuicatlán Valley – and the variation between them was significant (43.39%, P < 0.001). Results of a Mantel test showed a significant correlation between genetic and geographic distances (r = 0.511; P = 0.0001), suggesting a pattern of isolation by distance, which was corroborated by nested clade phylogeographic analysis. Mismatch distribution analysis indicated a sudden demographic expansion. Main conclusions Our study found that isolation by distance influenced genetic divergence in populations of H. fumariifolia. The finding that allopatric fragmentation influenced genetic divergence in populations in the Sierra Madre Oriental may be a reflection of the complex geology of the area. Our results suggest that the areas located in the north of the Sierra Madre Oriental acted as post‐glacial refugia for some populations.     

Climate change is the primary driver of white‐tailed deer (Odocoileus virginianus) range expansion at the northern extent of its range; land use is secondary

Quantifying the relative influence of multiple mechanisms driving recent range expansion of non‐native species is essential for predicting future changes and for informing adaptation and management plans to protect native species. White‐tailed deer (Odocoileus virginianus) have been expanding their range into the North American boreal forest over the last half of the 20th century. This has already altered predator–prey dynamics in Alberta, Canada, where the distribution likely reaches the northern extent of its continuous range. Although current white‐tailed deer distribution is explained by both climate and human land use, the influence each factor had on the observed range expansion would depend on the spatial and temporal pattern of these changes. Our objective was to quantify the relative importance of land use and climate change as drivers of white‐tailed deer range expansion and to predict decadal changes in white‐tailed deer distribution in northern Alberta for the first half of the 21st century. An existing species distribution model was used to predict past decadal distributions of white‐tailed deer which were validated using independent data. The effects of climate and land use change were isolated by comparing predictions under theoretical “no‐change between decades” scenarios, for each factor, to predictions under observed climate and land use change. Climate changes led to more than 88%, by area, of the increases in probability of white‐tailed deer presence across all decades. The distribution is predicted to extend 100 km further north across the northeastern Alberta boreal forest as climate continues to change over the first half of the 21st century.     

Molecular evidence for the origin and evolutionary history of the rare American desert monotypic family Setchellanthaceae

Setchellanthus caeruleus, which has disjunct populations in the north of the Chihuahuan Desert and in the Tehuacán-Cuicatlán valley, was selected to understand the evolutionary history of plants in this desert and its southerly relicts. This species constitutes the monotypic family Setchellanthaceae, which forms part of a group of plants that produce mustard-oil glucosides or glucosinolates. Molecular phylogenetic analyses based on DNA plastid sequences of plants of S. caeruleus from both areas, including representative taxa of the order Brassicales, were carried out to estimate the time of origin of the family (based on matK?+?rcbL) and divergence of populations (based on psbI-K, trnh-psbA, trnL-trnF). In addition, comparative ecological niche modelling was performed to detect if climate variables vary significantly in northern and southern populations. Analyses revealed that Setchellanthaceae is an ancient lineage that originated between 78 and 112 Mya during the mid-late Cretaceous—much earlier than the formation of the Chihuahuan Desert. The molecular data matrix displayed a few indel events as the only differences of plastid DNA sequences between northern and southern populations. It is suggested that due to climate changes in this desert in the Pliocene, populations of Setchellanthus remained in the Sierra de Jimulco and in Cuicatlán, in climatically stable locations. Ecological niche models of northern populations predict niches of southern populations and identity niche tests indicate that there are no differences in their ecological niches.     

Impact of white‐tailed deer on the spread of Borrelia burgdorferi

There is a public perception that the white‐tailed deer Odocoileus virginianus (Artiodactyla: Cervidae) is the main reservoir supporting the maintenance and spread of the causative agent of Lyme disease, Borrelia burgdorferi. This study examines the pathogen prevalence rate of Borrelia in adult Ixodes scapularis (Ixodida: Ixodidae), the black‐legged tick, collected from white‐tailed deer and compares it with pathogen prevalence rates in adult ticks gathered by dragging vegetation in two contiguous counties west of the Hudson Valley in upstate New York. In both Broome and Chenango Counties, attached and unattached ticks harvested from white‐tailed deer had significantly lower prevalences of B. burgdorferi than those collected from vegetation. No attached ticks on deer (n = 148) in either county, and only 2.4 and 7.3% of unattached ticks (n = 389) in Broome and Chenango Counties, respectively, were harbouring the pathogen. This contrasts with the finding that 40.8% of ticks in Broome County and 46.8% of ticks in Chenango County collected from vegetation harboured the pathogen. These data suggest that a mechanism in white‐tailed deer may aid in clearing the pathogen from attached deer ticks, although white‐tailed deer do contribute to the spatial distribution of deer tick populations and also serve as deadend host breeding sites for ticks.     

The effect of terrain and female density on survival of neonatal white‐tailed deer and mule deer fawns

Juvenile survival is a highly variable life‐history trait that is critical to population growth. Antipredator tactics, including an animal's use of its physical and social environment, are critical to juvenile survival. Here, we tested the hypothesis that habitat and social characteristics influence coyote (Canis latrans) predation on white‐tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) fawns in similar ways during the neonatal period. This would contrast to winter when the habitat and social characteristics that provide the most safety for each species differ. We monitored seven cohorts of white‐tailed deer and mule deer fawns at a grassland study site in Alberta, Canada. We used logistic regression and a model selection procedure to determine how habitat characteristics, climatic conditions, and female density influenced fawn survival during the first 8 weeks of life. Fawn survival improved after springs with productive vegetation (high integrated Normalized Difference Vegetation Index values). Fawns that used steeper terrain were more likely to survive. Fawns of both species had improved survival in years with higher densities of mule deer females, but not with higher densities of white‐tailed deer females, as predicted if they benefit from protection by mule deer. Our results suggest that topographical variation is a critical resource for neonates of many ungulate species, even species like white‐tailed deer that use more gentle terrain when older. Further, our results raise the possibility that neonatal white‐tailed fawns may benefit from associating with mule deer females, which may contribute to the expansion of white‐tailed deer into areas occupied by mule deer.     

White‐tailed deer as the last megafauna dispersing seeds in Neotropical dry forests: the role of fruit and seed traits

Endozoochory is a prominent form of seed dispersal in tropical dry forests. Most extant megafauna that perform such seed dispersal are ungulates, which can also be seed predators. White‐tailed deer (Odocoileus virginianus) is one of the last extant megafauna of Neotropical dry forests, but whether it serves as a legitimate seed disperser is poorly understood. We studied seed dispersal patterns and germination after white‐tailed deer gut passage in a tropical dry forest in southwest Ecuador. Over 23 mo, we recorded ca 2000 seeds of 11 species in 385 fecal samples. Most seeds belonged to four species of Fabaceae: Chloroleucon mangense, Senna mollissima, Piptadenia flava, and Caesalpinia glabrata. Seeds from eight of the 11 species dispersed by white‐tailed deer germinated under controlled conditions. Ingestion did not affect germination of C. mangense and S. mollissima, whereas C. glabrata showed reduced germination. Nevertheless, the removal of fruit pulp resulting from ingestion by white‐tailed deer could have a deinhibition effect on germination due to seed release. Thus, white‐tailed deer play an important role as legitimate seed dispersers of woody species formerly considered autochorous. Our results suggest that more research is needed to fully understand the ecological and evolutionary effects of the remaining extant megafauna on plant regeneration dynamics in the dry Neotropics.     

Host use patterns of Culicoides spp. biting midges at a big game preserve in Florida,U.S.A., and implications for the transmission of orbiviruses

Culicoides spp. biting midges (Diptera: Ceratopogonidae) are vectors of pathogens that have a significant economic impact on the livestock industry. White‐tailed deer (Odocoileus virginianus), a farmed species in the U.S.A., are susceptible to two Culicoides spp. borne orbiviruses: bluetongue virus and epizootic haemorrhagic disease virus. Elucidating host–vector interactions is an integral step in studying disease transmission. This study investigated the host range of Culicoides spp. present on a big game preserve in Florida on which a variety of Cervidae and Bovidae freely roam. Culicoides were captured with Centers for Disease Control and Prevention (CDC) miniature light traps run twice weekly on the preserve for 18 consecutive months (July 2015–December 2016). Host preference was quantified through forage ratios, based upon PCR‐based bloodmeal analysis of Culicoides spp. and overall animal relative abundance on the preserve. Culicoides stellifer preferentially fed on Cervus spp. and fallow deer (Dama dama) and displayed a relative avoidance of Bovidae and white‐tailed deer. Culicoides debilipalpis preferred white‐tailed deer and avoided all Bovidae. Culicoides pallidicornis and Culicoides biguttatus showed preferences for white‐tailed deer and Père David's deer (Elaphurus davidianus), respectively. These results add to current knowledge of preferred hosts of Florida Culicoides spp. and have implications for the spread of orbiviruses. Copyright © 2018 John Wiley & Sons, Ltd.     

Reproductive biology of Ferocactus recurvus (Mill.) Borg subsp. recurvus (Cactaceae) in the Tehuacán‐Cuicatlán Valley,Mexico

• Mexico has one of the highest diversities of barrel cacti species worldwide; however, all are threatened and require conservation policies. Information on their reproductive biology is crucial, but few studies are available. Ferocactus recurvus subsp. recurvus is a barrel cactus endemic to the Tehuacán‐Cuicatlán Valley. Our research aimed to characterise its floral and pollination biology. We hypothesised bee pollination, as suggested by its floral morphology and behaviour, and self‐incompatibility, like most barrel cacti studied.
• Three study sites were selected in the semiarid Zapotitlán Valley, Mexico. We examined 190 flowers from 180 plants to determine: morphometry and behaviour of flowers, flower visitors and probable pollinators, and breeding system.
• Flowers showed diurnal anthesis, lasting 2–5 days, the stigma being receptive on day 2 or 3 after the start of anthesis. Flowers produced scarce/no nectar and main visitors were bees (Apidae), followed by flies (Muscidae), ants (Formicidae), thrips (Thripidae) and hummingbirds (Throchilidae); however, only native bees and occasionally wasps contacted the stigma and anthers. Pollination experiments revealed that this species is self‐incompatible and xenogamous. In natural conditions, fruit set was 60% and cross‐pollination fruit set was 100%. Percentage seed germination resulting from cross‐pollination was higher than in the control treatment.
• Our results provide ecological information for conservation programmes to ensure a high probability of breeding and seed production in natural populations of F. recurvus.

     

Traditional Knowledge and Useful Plant Richness in the Tehuacán–Cuicatlán Valley,Mexico

Traditional Knowledge and Useful Plant Richness in the Tehuacán–Cuicatlán Valley, Mexico. This study systematizes ethnobotanical information about the interactions between people and plants, ethnofloristic richness, the relative importance of useful species richness in relation to general species richness, and plant management in the Tehuacán–Cuicatlán Valley of central Mexico. The study recorded a total of 1,605 useful vascular plant species (61.2% of the total species richness of the regional vascular flora), this being the region with the highest absolute richness of useful plant species in Mexico. The null hypothesis that plant families with a higher number of useful species would be those having a higher general species richness was analyzed through residuals method. The plant families richest in useful species were Poaceae, Asteraceae, Cactaceae, Cyperaceae, Mimosaceae, and Solanaceae, most of which also have the highest general floristic richness. However, analyses of use categories did not generally corroborate our hypothesis. About 1,335 of the useful species are wild, more than 500 species are submitted to some type of management (62 species are tolerated, 34 protected, 50 enhanced, and 358 cultivated), but only a few have been studied to document their process of domestication. This information can be useful for developing regional strategies of sustainable management of plant resources.     

Asymmetric Contribution of Isotopically Contrasting Food Sources to Vertebrate Consumers in a Subtropical Semi‐arid Ecosystem

Habitat heterogeneity is a primary ecological factor that is particularly pronounced in arid ecosystems. The Tehuacán valley is a subtropical semi‐arid ecosystem in which several species of columnar cacti and agave (i.e., CAM plants) constitute the dominant elements accompanied by patches of trees and shrubs (i.e., C₃ plants). Vegetation in Tehuacán is isotopically heterogenous because CAM plants have less depleted δ¹³C values than C₃ plants. Fruits and flowers of cactus and agaves offer abundant food to vertebrates, but their leaves might be less attractive to insects than the leaves of C₃ plants. Therefore, we use carbon and nitrogen stable isotope analysis to test the hypothesis that C₃ and CAM food would contribute asymmetrically to different guilds of birds and bats. We predict that granivorous and frugivorous birds and nectarivorous and frugivorous bats will consume a CAM diet, whereas insectivorous birds and bats will consume a C₃ diet. Due to omnivory of bird and bat consumers, we predict that the importance of CAM food will decrease as the trophic level of the animal increases. Our results showed that CAM food predominated in plant‐eating birds and in some flower‐visiting bats, whereas C₃ food predominated in insect‐eating bats and birds and frugivorous bats. Habitat heterogeneity in Tehuacán is important for conservation due to the asymmetric role of CAM and C₃ food in the nutrition of different feeding guilds of vertebrates. Our study provides basic information to evaluate the potential impact of habitat loss on functional groups of consumers in a semi‐arid ecosystem.     

甘肃草地4种毒杂草潜在入侵区预测研究

针对4种著名的草原毒杂草:醉马草,黄花棘豆,狼毒和露蕊乌头,应用生态位模型分别研究其在甘肃的潜在扩散区域。首先,通过最近邻体距离法和相关性分析分别选取样本数据和环境变量,接着应用最大熵方法(Maxent)建立生态位模型,预测了4种毒杂草的潜在分布区。最后通过Matlab和ENMTools计算了地理分布重心、平均海拔、等级分布区比例、生态位宽度、生态位重合度和地理分布重合度。研究结果表明:4种毒杂草中醉马草和狼毒的环境适应能力较强,但醉马草的分布范围更为广泛,从祁连山脉一直延伸到甘南草原,扩散重心基本在祁连山西侧,而狼毒分布范围主要在甘肃南部,地理分布重心大致位于兰州地区。黄花棘豆的分布范围主要集中在祁连山脉,而露蕊乌头更偏向甘南草原地区。     

Occupancy and density of a habitat specialist and a sympatric generalist songbird species in Tasmania

Patterns of distribution and abundance of species are dependent on their particular ecological requirements. Taking specialisation into account is important for interpreting population parameters. Here, we evaluate population parameters of an endangered habitat specialist, the forty‐spotted pardalote (Pardalotus quadragintus; dependent on white gum Eucalyptus viminalis in south‐eastern Tasmania), and a sympatric congeneric habitat generalist, the striated pardalote (Pardalotus striatus). We used occupancy models to estimate occupancy of both species, and distance sampling models to estimate population density and size on North Bruny Island. Within their shared habitat (i.e. white gum forest), we also fitted hierarchical distance sampling models to estimate density in relation to fine‐scale habitat features. We show that forty‐spotted pardalotes only occurred in forests where white gums were present, with a mean density of 2.7 birds per hectare. The density of forty‐spotted pardalotes decreased in areas with abundant small trees and trees with dead crowns, but they increased in areas where larger white gums were abundant. The striated pardalote was widespread, but where white gums were present, they occurred at 2.1 birds per hectare, compared to 0.6 birds per hectare in forests where white gums were absent. Within white gum habitat, the relative abundance of forty‐spotted pardalotes and dead trees had a positive effect on the density of striated pardalotes while small trees had a negative effect. Our study reveals that although widespread, the generalist is most abundant in the limited areas of habitat suitable for the specialist, and this indicates the need of future research to look at whether this pattern of occurrence exacerbates competition in resource depleted habitats.     

Opposing deer and caterpillar foraging preferences may prevent reductions in songbird prey biomass in historically overbrowsed forests

Overbrowsing by ungulates decimates plant populations and reduces diversity in a variety of ecosystems, but the mechanisms by which changes to plant community composition influence other trophic levels are poorly understood. In addition to removal of avian nesting habitat, browsing is hypothesized to reduce bird density and diversity through reduction of insect prey on browse‐tolerant hosts left behind by deer. In this study, we excluded birds from branches of six tree species to quantify differences in songbird prey removal across trees that vary in deer browse preference. Early in the breeding season, birds preyed on caterpillars at levels proportional to their abundance on each host. Combining these data with tree species composition data from stands exposed to experimentally controlled deer densities over 30 years ago, we tested whether overbrowsing by white‐tailed deer reduces prey biomass long after deer densities are reduced. Our analysis predicts total prey availability in the canopy of regenerating forests is fairly robust to historic exposure to high deer densities, though distribution of prey available from host species changes dramatically. This predicted compensatory effect was unexpected and is driven by high prey abundance on a single host tree species avoided by browsing deer, Prunus serotina. Thus, while we confirm that prey abundance on host trees can act as a reliable predictor for relative prey availability, this study shows that quantifying prey abundance across host trees is essential to understanding how changes in tree species composition interact with ungulate browse preference to determine prey availability for songbirds.     

Density of Ixodes scapularis ticks on Monhegan Island after complete deer removal: A question of avian importation?

Questing adult blacklegged tick (Ixodes scapularis Say) abundance declined markedly three years after the 1999 removal of white‐tailed deer (Odocoileus virginianus Zimmermann) from Monhegan Island, ME. Since 2000, subadult ticks have not been found on Norway rats (Rattus norvegicus Berkenhout); questing nymphs have not been found since 2002. This suggested I. scapularis was reintroduced annually via bird importation of subadult ticks, but unable to complete its two‐year life cycle on the island due to lack of deer. To investigate this, we used uncertainty analysis to estimate 1) questing adult ticks/ha that would result from avian importation of nymphs, and 2) questing adult ticks/ha on Monhegan Island, using bird capture and tick burden data from Appledore Island, ME, flagged tick data from Monhegan Island, and ten uncertain parameters. During the deer‐fed period (1990–2001), estimated tick density on Monhegan Island was 18 times greater than that of imported ticks. During the post‐deer‐fed period (2002–2008), Monhegan Island tick density was equivalent to imported tick density. This supported the premise that all I. scapularis ticks on Monhegan Island have been bird‐derived since 2002.     

When mechanism matters: Bayesian forecasting using models of ecological diffusion

Ecological diffusion is a theory that can be used to understand and forecast spatio‐temporal processes such as dispersal, invasion, and the spread of disease. Hierarchical Bayesian modelling provides a framework to make statistical inference and probabilistic forecasts, using mechanistic ecological models. To illustrate, we show how hierarchical Bayesian models of ecological diffusion can be implemented for large data sets that are distributed densely across space and time. The hierarchical Bayesian approach is used to understand and forecast the growth and geographic spread in the prevalence of chronic wasting disease in white‐tailed deer (Odocoileus virginianus). We compare statistical inference and forecasts from our hierarchical Bayesian model to phenomenological regression‐based methods that are commonly used to analyse spatial occurrence data. The mechanistic statistical model based on ecological diffusion led to important ecological insights, obviated a commonly ignored type of collinearity, and was the most accurate method for forecasting.     

Refugia and geographic barriers of populations of the desert poppy, Hunnemannia fumariifolia (Papaveraceae)

Phylogeographic data and divergence estimation times as well as current and past ecological niche modeling for the Mexican tulip poppy, Hunnemannia fumariifolia Sweet, were combined in order to understand its biogeographic history. Divergence times were estimated to determine if divergence occurred during the Pleistocene. Ecological niche modelling was used to determine if the last glacial maximum (LGM) was responsible for the southward movement of poppy populations into the Tehuacán-Cuicatlán Valley. Analyses were performed to detect any geographical barriers that might have caused genetic discontinuities among populations across the entire range of distribution. Current and Pleistocene ecological niche models were created for H. fumariifolia using eight environmental variables derived from temperature and precipitation. The evidence shows that divergence of the three main clades in H. fumariifolia occurred from the Early Pleistocene to Mid-Miocene. It was also found that gene flow between the populations of H. fumariifolia could have been limited by the LGM, by climate change during the Quaternary, and by the complex topography of the Sierra Madre Oriental and the Trans-Mexican Volcanic Belt. Furthermore, all of these processes may have resulted in the patchy distribution of suitable microhabitats for H. fumariifolia in its geographical range. Ecological niche models constructed using the MIROC3 model indicated that populations did not move to the north but rather that they had suitable ecological habitats in the Chihuahuan Desert, which harbored Pinus-Juniperus forests during that period.     

Breeding behavior of female white‐tailed deer relative to conception: Evidence for female mate choice

Female white‐tailed deer (Odocoileus virginianus) are thought to choose between two behavioral strategies to maximize the quality of potential mates: sit and wait, characterized by concentrating activity within a restricted area, and excursive behavior, characterized by increased activity and excursions outside the home range. As movement patterns may influence conception, our goal was to examine the patterns of female white‐tailed deer movements to evaluate which breeding strategy was employed. We equipped 36 female white‐tailed deer with GPS collars from August 2013 to December 2015. We found that movement rate and probability of activity were greatest near the peak of the breeding season, and we observed increases in both metrics during the 40 days prior to estimated conception. Peak size of home range and core area occurred in the days surrounding conception. We found that 11 deer performed an excursion, ranging from 43 days before until 36 days after conception, with the peak probability of being outside of an individual home range occurring 1 day prior to conception. Our results suggest that female white‐tailed deer may attempt to maximize the quality of their mates by advertising availability for breeding through excursive behaviors just prior to entering estrus.     

Estimating Neospora caninum prevalence in wildlife populations using Bayesian inference

Prevalence of disease in wildlife populations, which is necessary for developing disease models and conducting epidemiologic analyses, is often understudied. Laboratory tests used to screen for diseases in wildlife populations often are validated only for domestic animals. Consequently, the use of these tests for wildlife populations may lead to inaccurate estimates of disease prevalence. We demonstrate the use of Bayesian latent class analysis (LCA) in determining the specificity and sensitivity of a competitive enzyme‐linked immunosorbent assay (cELISA; VMRD^®, Inc.) serologic test used to identify exposure to Neospora caninum (hereafter N. caninum) in three wildlife populations in southeastern Ohio, USA. True prevalence of N. caninum exposure in these populations was estimated to range from 0.1% to 3.1% in American bison (Bison bison), 51.0% to 53.8% in Père David's deer (Elaphurus davidianus), and 40.0% to 45.9% in white‐tailed deer (Odocoileus virginianus). The accuracy of the cELISA in American bison and Père David's deer was estimated to be close to the 96% sensitivity and 99% specificity reported by the manufacturer. Sensitivity in white‐tailed deer, however, ranged from 78.9% to 99.9%. Apparent prevalence of N. caninum from the test results is not equal to the true prevalence in white‐tailed deer and Père David's deer populations. Even when these species inhabit the same community, the true prevalence in the two deer populations differed from the true prevalence in the American bison population. Variances in prevalence for some species suggest differences in the epidemiology of N. caninum for these colocated populations. Bayesian LCA methods could be used as in this example to overcome some of the constraints on validating tests in wildlife species. The ability to accurately evaluate disease status and prevalence in a population improves our understanding of the epidemiology of multihost pathogen systems at the community level.     

Ungulate browsers promote herbaceous layer diversity in logged temperate forests

Ungulates are leading drivers of plant communities worldwide, with impacts linked to animal density, disturbance and vegetation structure, and site productivity. Many ecosystems have more than one ungulate species; however, few studies have specifically examined the combined effects of two or more species on plant communities. We examined the extent to which two ungulate browsers (moose [Alces americanus]) and white‐tailed deer [Odocoileus virginianus]) have additive (compounding) or compensatory (opposing) effects on herbaceous layer composition and diversity, 5–6 years after timber harvest in Massachusetts, USA. We established three combinations of ungulates using two types of fenced exclosures – none (full exclosure), deer (partial exclosure), and deer + moose (control) in six replicated blocks. Species composition diverged among browser treatments, and changes were generally additive. Plant assemblages characteristic of closed canopy forests were less abundant and assemblages characteristic of open/disturbed habitats were more abundant in deer + moose plots compared with ungulate excluded areas. Browsing by deer + moose resulted in greater herbaceous species richness at the plot scale (169 m²) and greater woody species richness at the subplot scale (1 m²) than ungulate exclusion and deer alone. Browsing by deer + moose resulted in strong changes to the composition, structure, and diversity of forest herbaceous layers, relative to areas free of ungulates and areas browed by white‐tailed deer alone. Our results provide evidence that moderate browsing in forest openings can promote both herbaceous and woody plant diversity. These results are consistent with the classic grazing‐species richness curve, but have rarely been documented in forests.     

Bacterial community in the rhizosphere of the cactus species Mammillaria carnea during dry and rainy seasons assessed by deep sequencing

Background and aims

The Tehuacán-Cuitcatlán reserve is an area of unique plant biodiversity mostly in the form of xerophytes, with exceptionally high numbers of rare and endemic species. This endemism results partly from the characteristics of the climate of this area, with two distinct seasons: rainy and dry seasons. Although rhizosphere communities must be critical in the function of this ecosystem, understanding the structure of these communities is currently limited. This is the first molecular study of the microbial diversity present in the rhizosphere of Mamillaria carnea.

Methods

Total DNA was obtained from soil and rhizosphere samples at three locations in the Tehuacán Cuicatlán Reserve, during dry and rainy seasons. Temperature gradient gel electrophoresisis (TGGE) fingerprinting, 16S rRNA gene libraries and pyrosequencing were used to investigate bacterial diversity in the rhizosphere of Mammillaria carnea and changes in the microbial community between seasons.

Results

Deep sequencing data reveal a higher level of biodiversity in the dry season. Statistical analyses based on these data indicates that the composition of the bacterial community differed between both seasons affecting to members of the phyla Acidobacteria, Cyanobacteria, Gemmatimonadetes, Plantomycetes, Actinobacteria and Firmicutes. In addition, the depth of sequencing performed (>24,000 reads) enables detection of changes in the relative abundance of lower bacterial taxa (novel bacterial phylotypes) indicative of the increase of specific bacterial populations due to the season.

Conclusions

This study states the basis of the bacterial diversity in the rhizosphere of cacti in semi-arid environments and it is a sequence-based demonstration of community shifts in different seasons.