Grassland Populations Research Articles

Himantoglossum hircinum(Lizard Orchid) reviewed in the light of new morphological and molecular observations

Himantoglossum hircinum is one of the rarer and more charismatic orchids in the British flora. Morphometric comparison of the two largest and best-known populations in southern England – the coastal dune population at Sandwich and the chalk grassland population at Newmarket – using 46 characters showed that they differ only subtly, the Sandwich plants being on average more vegetatively robust and slightly more darkly pigmented, but possessing less extensive lip-spots and substantially longer ‘arms’. A comparatively morphologically divergent semi-desert population from Ifrane, Morocco differs from the English populations in having broader stems, less recurved ‘arms’, a more strongly down-curved spur and in lacking near-circular spots within the sepals. Molecular comparison of 46 plants, representing 13 English populations and 18 populations from Continental Europe and Morocco, revealed only subtle distinctions in the high-copy nuclear region ITS, and smaller-scale comparisons of the low-copy nuclear (LEAFY) and plastid (four intron) regions proved to be even less discriminatory. These results reinforce prior morphological inferences that H. hircinum is a cohesive species. Scanning electron microscopy elucidated the ontogeny of these remarkable flowers, suggesting that the exceptionally elongate central labellar lobe originated by accelerated heterochronic growth and showing that the characteristic spiral torsion always runs counter-clockwise. Lateral fusion of the paired viscidia is convergent with several other lineages of subtribe Orchidinae. Review of pollination and life-history features of H. hircinum suggest that they are typical of food-deceptive species within Orchidinae. The Lizard Orchid is infamous for geographic mobility; its cycles of expansion and contraction through the last century have been interpreted as reflecting a net northward migration in response to recent climate change. Our data tentatively suggest relatively recent colonisation of Morocco at high altitudes and an overall northwestward direction of migration into the UK. ITS ribotypes indicate multiple immigration events leading to levels of genetic diversity in England comparable with those on the Continent. A non-recent origin is inferred for H. hircinum which, despite recent systematic revisions, may harbour further cryptic species; the taxonomic status of supposed outlying populations in southern Italy in particular is questioned by the present genetic data.

Potential roles of small and linear habitat fragments in satoyama landscapes for conservation of grassland plant species

By comparing with the historic semi-natural grassland and woodland vegetation data compiled in the 1970s and 1980s, we aimed to reveal potential roles of small and linear habitat fragments remaining in the urbanized satoyama landscape (i.e., agricultural landscape) in Japan for conservation of grassland plant species. TWINSPAN cluster analysis differentiated the current vegetation from historic one. Current vegetation of Miscanthus grassland was classified into two different groups and one of the two was equivalent to current understory vegetation of fragmented woodland. The linear woodland edge vegetation along the roads was classified into one group and separated from the other current vegetation groups. The current vegetation groups were characterized by higher richness of exotic species than historic vegetation groups. Detrended correspondence analysis (DCA) revealed that there were no groups of current vegetation that is equivalent to historic woodland understory vegetation. The vegetation quality of the current group of Miscanthus grassland and secondary woodland remaining on urban public properties, and the group of linear roadside vegetation were almost equivalent to that of historic semi-natural grassland. Both of the small and linear habitat fragments might have functioned as habitats for grassland species under regular mowing management. Although small and linear habitat fragments would not be sufficient for sustaining grassland populations in the future, these habitats can serve as key reservoirs for grassland species recovery in the conservation and restoration of grassland communities in the urbanized satoyama landscape.

Which plant traits predict species loss in calcareous grasslands with extinction debt?

AbstractAim Habitat loss and degradation pose a major threat to biodiversity, which can result in the extinction of habitat characteristic species. However, many species exhibit a delayed response to environmental changes because of the slow intrinsic dynamics of populations, resulting in extinction debt. We assess directly the changes in habitat characteristic species composition by comparing historical (1923) and current inventories in highly fragmented grasslands. We aim to characterize the species that constitute extinction debt in European calcareous grasslands.Location Europe, Estonia, 59–60° N, 24–25° E.Methods We related eleven life‐history traits and selected habitat preferences to local extinctions of populations in grasslands where extinction debt has been largely paid. Traits were chosen to describe species dispersal and persistence abilities and were quantified from databases.Results The studied grasslands have lost 90% of their area and 30% of their characteristic plant populations in 90 years. Species more prone to local population extinction were characterized by shorter life span, self‐pollination, a lack of clonal growth, fewer seeds per shoot, lower average height, lower soil nitrogen preference and higher requirements for light, indicating a limited ability to tolerate the range of changes in biotic and abiotic conditions of the sites. Locally extinct populations were also characterized by wind‐dispersed seeds, lower seed weight and lower terminal velocity of seeds, suggesting that species strategies for long‐distance dispersal are not favoured in highly fragmented landscapes. Thus, both increased habitat isolation and decreased habitat quality are important in determining local population extinction.Main conclusions Populations more prone to local extinction were characterized by a number of life‐history traits, demonstrating a greater extinction risk for species with poorer abilities for local persistence and competition. Our results can be applied to less degraded grasslands where the extinction debt is not yet paid to determine those species most susceptible to future extinction.

Species richness and density of earthworm populations in grasslands of western Uttar Pradesh, India

This study presents the first survey of earthworm species from the grasslands of Uttar Pradesh, a northern state of India. The study was conducted in all five political regions (e.g., Agra, Bareilly, Meerut, Moradabad and Saharanpur) of western Uttar Pradesh, during different climatic seasons from the year 2007 till 2009. Seven species belonging to two earthworm families were recorded: Metaphire posthuma (Vaillant), Lampito mauritii (Kinberg, 1867) and Perionyx excavatus (Perrier, 1872) from Megascolecidae and Eutyphoeus i.e. E. waltoni (Michaelsen, 1907), E. gigas (Stephenson, 1917), E. orientalis (Beddard, 1883) and E. pharpingianus (Michaelsen, 1907) from Octochaetidae. Moradabad was identified as the region of western Uttar Pradesh showing the highest species richness of earthworms during rainy season (July to October). Species richness and density of worms were assessed the maximum in Moradabad and the minimum density in Saharanpur during peak winter months i.e. from November to February. However, species richness of worms was found the least in Meerut region during winter and summer months and Saharanpur during summers (March to June). M. posthuma was found in all the regions round the years but L. mauritii and E.waltoni have been reported from all the regions only during the rainy season. P. excavatus was next in occurrence pattern, as it was recorded from all the regions except from Meerut. E. pharpingianus was found in all the regions except Meerut. Occurrence of E.orientalis and E. gigas was recorded rarely.

How do sheep affect plant communities and arthropod populations in temperate grasslands?

Grasslands being used in sheep farming systems are managed under a variety of agricultural production, recreational and conservational objectives. Although sheep grazing is rarely considered the best method for delivering conservation objectives in seminatural temperate grasslands, the literature does not provide unequivocal evidence on the impact of sheep grazing on pasture biodiversity. Our aim was therefore to review evidence of the impacts of stocking rate, grazing period and soil fertility on plant communities and arthropod populations in both mesotrophic grasslands typical of agriculturally improved areas and in native plant communities. We therefore conducted a literature search of articles published up to the end of the year 2010 using ‘sheep’ and ‘grazing’ as keywords, together with variables describing grassland management, plant community structure or arthropod taxa. The filtering process led to the selection of 48 articles, with 42 included in the stocking rate dataset, 9 in the grazing period dataset and 10 in the soil fertility dataset. The meta-analysis did not reveal any significant trends for plant species richness or plant community evenness along a wide stocking rate gradient. However, we found frequent shifts in functional groups or plant species abundance that could be explained by the functional properties of the plants in the community. The meta-analysis confirmed that increasing soil fertility decreased plant species richness. Despite the very limited dataset, plant species richness was significantly greater in autumn-grazed pastures than in ungrazed areas, which suggests that choosing an appropriate grazing period would be a promising option for preserving biodiversity in sheep farming systems. Qualitative review indicated that low grazing intensity had positive effects on Orthoptera, Hemiptera (especially phytophagous Auchenorrhyncha) and, despite a diverse range of feeding strategies, for the species richness of Coleoptera. Lepidoptera, which were favoured by more abundant flowering plants, also benefited from low grazing intensities. Spider abundance and species richness were higher in ungrazed than in grazed pastures. In contrast, there are insufficient published studies to draw any firm conclusions on the benefits of late grazing or stopping fertilization on insect diversity, and no grounds for including any of this information in decision support tools at this stage.

Impact of climatic factors on genetic diversity of Stipa breviflora populations in Inner Mongolia

Genetic diversity of Stipa breviflora populations in the Inner Mongolian grasslands of China and its possible correlation with climatic factors was examined using geographic information systems and random amplified polymorphism DNA analysis. A total of 308 bands were produced with 28 arbitrary decamer oligonucleotide. Three major findings were demonstrated. First, the genetic diversity of S. breviflora was high but lower than that of Stipa grandis and Stipa krylovii. Second, genetic distances between the populations analyzed using the unweighted pair group method and the Mantel test had a highly positive correlation with geographical distances, indicating that spatial separation of this species in the studied area produced genetic shift in the population. Finally, both canonical correspondence and Pearson's analyses revealed strong correlations between genetic differentiation and temperature in the area. We therefore conclude that temperature variations play an important role in genetic differentiations among the investigated S. breviflora populations.

The heat is on: frequent high intensity fire in bracken (Pteridium aquilinum) drives mortality of the sprouting tree Protea caffra in temperate grasslands

We examined the effect of fire frequency and intensity on a Protea caffra tree population in the temperate montane grasslands of north-western KwaZulu-Natal, South Africa. We assessed the effect of fire by comparing the population structure of the resprouter P. caffra in discrete bracken (Pteridium aquilinum) patches with that in the surrounding grassland matrix. Fuel biomass did not differ between grassland and bracken, but bracken fuel was significantly drier than grass. Above-ground fire temperatures and fireline intensity, measured by P. caffra char height, were significantly higher in the bracken habitat. Forty-two percent of the P. caffra population in grassland and in bracken persisted by coppice resprouts, having lost their original stem to fire damage. Exposure to higher intensity bracken fire suppressed P. caffra regeneration and caused greater adult mortality compared with trees in grassland. Consequently, the P. caffra population in bracken was skewed towards old age with most trees severely fire damaged. The high incidence of small trees in grassland indicates that a regular fire interval of 2–3 years does not negatively affect regeneration of P. caffra. However, in bracken patches regular high intensity fires cause high mortality among all P. caffra size classes and will ultimately result in local extinction. Bracken thus has the potential to significantly alter tree–grass interactions in these montane grasslands.

Stochastic LTRE analysis of the effects of herbivory on the population dynamics of a perennial grassland herb

Herbivores can have strong deleterious effects on vital rates (growth, reproduction, and survival) and thus negatively impact the population dynamics of plant species. In practice, however, these effects might be strongly correlated, for example as a result of tradeoffs between vital rates. To get better insights into the effects of herbivory on the population dynamics of the long‐lived grassland plant Primula veris population projection matrices were constructed from demographic data collected between 1999 and 2008 (nine annual transitions). Data were collected in two large grassland populations, each of which was subjected to two treatments (grazing by cattle versus a mowing treatment), yielding a total of 36 matrices. We applied a lower‐level vital rate life table response experiment (LTRE) using the small noise approximation (SNA) of the stochastic population growth rate to disentangle the contributions of changes in mean vital rates, variability in vital rates, correlations between vital rates and vital rate elasticities to the difference in the stochastic growth rate. Stochastic growth rates (a= log λS) were significantly lower in grazed than in mown plots (a= 0.0185 and 0.1019, respectively). SNA LTRE analysis showed that contributions of mean vital rates by far made the largest contribution to the observed difference in a between grazed and control plots. In particular, changes in sexual reproduction rates made the largest contributions to lower the stochastic growth rate in grazed plots: both adult flowering probabilities and flower and seed production were importantly lower in grazed populations, but these negative effects were largely buffered by increased establishment and seedling survival rates. Among the stochastic terms of the SNA decomposition, contributions of covariance and correlations between vital rates had the largest impact, whereas contributions of elasticities were smaller. The strongest correlation driver was the association between adult survival and seedling establishment, suggesting that environmental conditions favouring adult survival also are beneficial for seedling establishment. Overall, our results show that herbivory had a strong negative effect on the long‐term population growth rate of P. veris that was primarily mediated by differences in fecundity (flower and seed production) and germination.

The community ecology of barley/ cereal yellow dwarf viruses in Western US grasslands

Research on plant viruses in natural ecosystems has been increasing rapidly over the past decade. This paper reviews recent research on the barley and cereal yellow dwarf viruses (B/CYDVs) in grasslands of the western US, beginning with the evidence that the disease caused by these viruses facilitated the invasion of western US grasslands by European annual grasses. Observational and experimental studies of B/CYDVs were carried out along a latitudinal gradient (33.8–48.8°N) from southern California to southern Canada. The prevalence and community composition of B/CYDVs were assessed over a variety of scales and under a range of biotic and abiotic conditions. The findings indicate that both biotic and abiotic factors are important influences on virus ecology and epidemiology. Introduced annual grasses are high-quality hosts that amplify both virus and vector populations in this system, but our research suggests that endemic perennial grasses are critically important for sustaining virus populations in contemporary grasslands largely composed of introduced species. Experiments indicated that increased phosphorus supply to hosts resulted in greater host biomass and higher virus prevalence. Using experimental exclosures, it was found that the presence of grazing vertebrate herbivores increased the abundance of annual grasses, resulting in increased virus prevalence. The results of these studies suggest that patterns of B/CYDV prevalence and coinfection in western US grasslands are strongly shaped by the interactions of host plants, vectors, vertebrate herbivores, and abiotic drivers including nutrients.

Effect of competition on niche dynamics of syntopic grazing ungulates: contrasting the predictions of habitat selection models using stable isotope analysis

Background: Theories of density-dependent habitat selection provide two solutions for co-existence of competing species. The niche compression hypothesis predicts that species reduce their respective niche breadths in response to inter-specific competition. Alternatively, if the species have similar resource preferences, the subordinate species may be forced to expand its niche to incorporate secondary resources. Aim: Determine whether grazing ungulate species partition the resource by compression or expansion of dietary niches. Organisms: Black wildebeest (Connochaetes gnou) and blue wildebeest (C. taurinus). Methods: Stable carbon and nitrogen isotope analysis of faeces. Isotopic niche breadths are compared across allopatric and sympatric wildebeest populations in South African grasslands. Results: Stable carbon and nitrogen isotope niche breadths of the two wildebeest species were virtually identical. In sympatry, however, black wildebeest had a narrower δ13C niche breadth (indicating almost exclusive use of C4 grass), whereas blue wildebeest had a wider δ13C niche breadth (indicating significant contributions from C3 sources). Blue wildebeest also had a wider δ15N niche breadth than sympatric black wildebeest. Moreover, the δ13C niche breadths of sympatric black wildebeest and blue wildebeest were narrower and wider, respectively, than those of allopatric populations of either species. Conclusions: Isotope niche dynamics across allopatric and sympatric populations arise due to the combined effects of competition and habitat heterogeneity on resource use. Although results for black wildebeest resemble niche compression, this hypothesis cannot explain patterns observed in blue wildebeest. Expansion of the blue wildebeest niche, and restricted niche breadth of black wildebeest, is consistent with predictions of a shared preference model in which black wildebeest are the dominant competitor. When competition is operating, differences in the way species use secondary resources can have an important role in structuring grazer assemblages.

Historical Land Use Explains Current Distribution of Calcareous Grassland Species

In this study we analyzed if characteristic calcareous grassland species persist in forest habitats after land use change. Furthermore, we investigated whether the current distribution of such species is related to historical land use of the mid-19th century. Current distributions of nine calcareous grassland species were recorded in a region of Upper Franconia, Germany. Historical (up to 1850) and current land-use data were analyzed using historical maps and aerial photographs. To study the effects of historical land use in current species distributions, we used Generalized Estimating Equations (GEE) and ANOVA, accounting for spatial autocorrelation. Variance partitioning was applied to separate the influence of historical versus current land use. On average 26% of the recorded grassland species occurrences are located in sub-optimal forest habitats. Grassland populations are likely to persist in forest for at least 50 years. Even though current land use explains a higher proportion of the variation in species distribution than historical land use alone, model fit could be significantly improved (P < 0.001) considering the historical component. We conclude that consideration of historical land use is essential to understand the current grassland species distributions and may be of general importance for perennial species of temperate grasslands. In addition, historical legacy has far-reaching implications for conservation biology in terms of realistic assessments of species threat status in present landscapes.

Fine-scale spatial patterns of Stellera chamaejasme population in degraded alpine grassland in upper reaches of Heihe, China

Aims The formation and changes of patches has an important effect on population patterns. Our objectives are to determine 1) how patches are formed during the process of Stellera chamaejasme population dispersion, 2) what is the effect on pattern during forming and changing of the patch and 3) what roles the formation and changes of the patches play in population dispersion. Methods We studied five 2 m × 2 m plots of different S. chamaejasme cover in the upper reaches of Heihe, China, using the point pattern method to analyze population pattern, size and density. Important findings With increasing cover, the population density and territory density tended to increase, decrease, and then increase and the number of the S. chamaejasme population tended to increase and decrease in turn. In the study area, the pattern under 31%–40% cover at all scales was a random distribution. Under the cover of 41%–50%, 51%–60%, 61%–70% and 71%–80%, the distribution pattern was random—clumped—random or regular—random—clumped—random and the clumped density was different. It formed patches during the process of S. chamaejasme population dispersion, which was clumped for external and random or regular for internal S. chamaejasme population dispersion through which patches combine and annex.

Age at puberty in male African striped mice: the impact of food, population density and the presence of the father

Summary 1. The time at which animals enter puberty and become sexually mature is a significant life‐history trait, influencing lifetime reproductive success. Great variation exists both between and within species. 2. The proximate mechanisms regulating the time at which a male enters puberty are not well‐understood. Environmental cues are predicted to provide the relevant information on resource availability and opportunities for reproduction. When these are good the onset of puberty begins whereas at other times investment in survival becomes more important. 3. Male African striped mice (Rhabdomys pumilio) demonstrate large variation in the age at which they enter puberty, with grassland populations starting at 4 weeks old and semi‐desert populations at over 10 weeks old. 4. We predicted that differences in the availability of food, social organization and population density could explain these differences. 5. Using data on 170 individual males from 4 years of field studies in a semi‐desert population, we found that males became scrotal at a younger age when no breeding male was present in their group and when food was abundant, while population density had no effect. 6. In laboratory experiments we demonstrated that males fed with poor protein food, that regularly encounter larger unfamiliar males (mimicking high population density), and that live in family groups with their father present, become scrotal at a significantly later age, independent of their growth rate. 7. Males housed in family groups have lower testosterone but higher corticosterone levels than singly housed males, indicating they are sexually suppressed. When they become scrotal in their family group, their testes are only half as large as those of their singly housed brothers, and they contained significantly less sperm. 8. We conclude that male striped mice have a flexible response to the onset of puberty, and that the onset of sexual maturity is dependent on several environmental cues. Our results indicate that there is no threshold body mass, which, when reached, would automatically trigger puberty in male striped mice. 9. Male helpers in some species are reproductively suppressed, but ours is the first study that demonstrated the importance of different ecological factors in the timing of puberty in male helpers in a facultative cooperatively breeding species.

Cross‐species amplification tests and diversity analysis using 56 PCR markers in Dactylis glomerata and Lolium perenne

We report results of cross-species amplification in Dactylis glomerata and Lolium perenne of 12 simple sequence repeats (SSRs) isolated from Lolium multiflorum×Festuca glaucescens, 42 SSRs from Festuca arundinacea and two sequence tagged sites from Oryza sativa. We compared the transferability and diversity between D. glomerata and L. perenne, which are important forage crops. While Nei's gene diversity values were equivalent in both species (from 0.14 to 0.92), the mean number of allele per locus was more important in D. glomerata than in L. perenne (5.45 vs. 4.50). These markers will be used for analysing population structure in grassland populations under agronomic practices.

Social transmission of information about novel food in two populations of the African striped mouse, Rhabdomys pumilio

Social learning involves the transmission of information from demonstrators to conspecifics. The mother is expected to be the main demonstrator in solitary species, whereas several individuals can be demonstrators in group-living species. We studied social learning about novel food in two populations of the African striped mouse, with different social systems: a desert population (group living with paternal care and natal philopatry) and a grassland population (solitary, paternal care in captivity only and natal dispersal). We predicted that both parents would be reliable demonstrators for desert striped mice but only the mother would be a demonstrator for grassland striped mice. Adults and unweaned young were assigned to one of five treatments in captivity: (1) father or (2) mother fed novel food away from young; (3) novel food fed to both adults with young present; and (4) father or (5) mother fed mouse cubes (control) away from young. Juveniles from all treatments individually received novel food after weaning. The responses of juveniles to novel food were greater (shorter latency, more sniffs) when the mother was the demonstrator, regardless of population. Mothers may be more reliable demonstrators than fathers because information can be transmitted using multiple channels (olfaction, lactation). Our study also showed that fathers were more reliable demonstrators and responses to the novel food were greater in desert than grassland striped mice. These population differences reflect the different social organization of the populations and the unpredictable availability of highly nutritious food in the desert.

Reproductive strategy of an invasive thistle: effects of adults on seedling survival

Invasive species are known for their ability to form monocultures that exclude native species, yet intraspecific interactions among invasives have not been well studied. Cynara cardunculus (L.) is an invasive perennial thistle that establishes high-density populations in coastal California grasslands. We examined the natural distribution of C. cardunculus seedlings in an established population and found that nearly 100% of seedlings grew within 2 m of adults despite an expected distribution peak at 3 m from source plants based on measured dispersal distances. We then investigated the role of mature plants in seedling survival and establishment with regard to live vegetation, litter, and seedling distance by planting seedlings at increasing distances around adults and applying removal treatments to the focal adult rosettes. We applied control (no removal), adult rosette removal (live leaves), litter removal (dead leaves), and adult rosette plus litter removal (all aboveground plant material) treatments. Seedlings experienced a higher rate of survival, measured by senescence date, and establishment, measured by return rate the following year, with all adult rosette removal treatments. Inhibition by adult rosettes was reduced with distance to 60–80 cm from the rosette, and there was little effect of adult plants between 80 and 200 cm. These results suggest that adult rosettes may inhibit conspecific seedlings at very close distances but provide a favorable environment for seedlings within nearby interspaces. This pattern may contribute to the creation and maintenance of high-density populations in C. cardunculus. Land managers seeking to control this species may improve long-term effectiveness by expanding management efforts to include a 2 m radius around adult plants and treating within 5 months of seedling emergence to prevent recruitment rather than treating adults alone.

Cattle grazing, raptor abundance and small mammal communities in Mediterranean grasslands

Abundance and diversity of small mammals are usually affected strongly by grazing either due to decreased food availability or quality, decreased suitability of soil for building burrow systems due to trampling and/or due to increased predation risk in the structurally simpler grazed areas. We estimated the effects of grazing-induced changes in vegetation and soil and of increased predation on small mammals in a Mediterranean grassland landscape. We measured vegetation structure, soil compaction and small mammal abundance and species composition in 22 plots of 8 Sherman live traps each, arranged according to an unbalanced two-way ANOVA design with two grazing levels (grazed areas and cattle exclosures) and two predator abundance levels (increased densities of Eurasian kestrels Falco tinnunculus by means of nest boxes and control). Plots were sampled during 2 consecutive years in early summer and early fall. Exclosure from cattle increased significantly vegetation height and volume and decreased soil compaction. Grazing-induced changes in vegetation height and volume and in soil compaction produced strong effects on small mammal abundance and species richness. Increased kestrel densities did not have significant additive or interactive effects, with the effects of grazing-induced vegetation and soil gradients on abundance or richness of small mammals. Our results suggest that the effects of grazing on small mammal communities in Mediterranean montane grasslands were mainly due to reduced food availability and by negative effects of trampling on the suitability of soils for building burrow systems. Decreased food quality and increased predation in grazed areas seemed to play a minor role, if any. Reductions in stock densities would then favor generalist predator populations in Mediterranean grasslands through the expected positive effects of such reductions on the availability of food and burrows for small mammals.

Litter species composition influences the performance of seedlings of grassland herbs

Summary 1 This study examines the impacts of plant litter species identity and the composition of litter mixtures on seedling recruitment in the context of land-use change (abandonment) in conservationally important southern Swedish semi-natural grasslands. 2 We found that plant litter had marked positive effects on the seedling recruitment of two common grassland species, and that these effects varied strongly with the species identity of the litter. 3 There was no consistent evidence that litters of species typical of earlier succession had a greater positive impact on recruitment than those typical of late succession. 4 The impact of mixtures of the five litter types examined was generally as expected based on the impacts of single-species litters and their contribution to the litter mixture, as predicted by the biomass ratio hypothesis. However, this was not the case for all litter and seedling species combinations, and some interactions were evident. 5 Species identity of litter is important even in multispecies litter mixtures. Changes in plant species dominance (and hence the proportions of litter of different species), as a result of shifts in land use, are likely to result in changes in seedling performance, with potential consequences for the persistence of plant populations in former semi-natural grasslands.

Habitat Edge, Land Management, And Rates Of Brood Parasitism In Tallgrass Prairie

Bird populations in North America's grasslands have declined sharply in recent decades. These declines are traceable, in large part, to habitat loss, but management of tallgrass prairie also has an impact. An indirect source of decline potentially associated with management is brood parasitism by the Brown-headed Cowbird (Molothrus ater), which has had substantial negative impacts on many passerine hosts. Using a novel application of regression trees, we analyzed an extensive five-year set of nest data to test how management of tallgrass prairie affected rates of brood parasitism. We examined seven landscape features that may have been associated with parasitism: presence of edge, burning, or grazing, and distance of the nest from woody vegetation, water, roads, or fences. All five grassland passerines that we included in the analyses exhibited evidence of an edge effect: the Grasshopper Sparrow (Ammodramus savannarum), Henslow's Sparrow (A. henslowii), Dickcissel (Spiza americana), Red-winged Blackbird (Agelaius phoeniceus), and Eastern Meadowlark (Sturnella magna). The edge was represented by narrow strips of woody vegetation occurring along roadsides cut through tallgrass prairie. The sparrows avoided nesting along these woody edges, whereas the other three species experienced significantly higher (1.9-5.3x) rates of parasitism along edges than in prairie. The edge effect could be related directly to increase in parasitism rate with decreased distance from woody vegetation. After accounting for edge effect in these three species, we found evidence for significantly higher (2.5-10.5x) rates of parasitism in grazed plots, particularly those burned in spring to increase forage, than in undisturbed prairie. Regression tree analysis proved to be an important tool for hierarchically parsing various landscape features that affect parasitism rates. We conclude that, on the Great Plains, rates of brood parasitism are strongly associated with relatively recent road cuts, in that edge effects manifest themselves through the presence of trees, a novel habitat component in much of the tallgrass prairie. Grazing is also a key associate of increased parasitism. Areas managed with prescribed fire, used frequently to increase forage for grazing cattle, may experience higher rates of brood parasitism. Regardless, removing trees and shrubs along roadsides and refraining from planting them along new roads may benefit grassland birds.

Ceropegia macmasteri (Apocynaceae–Asclepiadoideae–Ceropegieae), a new species from Eastern Cape, South Africa

Ceropegia macmasteri, a new species from Cathcart in the Eastern Cape Province of South Africa, is only known from a single population in Dohne sourveld grassland where it occurs with another rare local endemic species of the Ceropegieae, Brachystelma cathcartense R.A.Dyer. The new species, an herbaceous grassland plant with a tuberous rootstock, most closely resembles C. stentiae E.A.Bruce, but is distinguished by its linear-erect corona lobes and inner corona conniving to form a central column.