Comparison of intraspecific nest usurpation between two haplometrotic paper wasp species (Hymenoptera: Vespidae:Polistes)

Intraspecific nest usurpation by foundresses was studied in 2 haplometrotic (solitary founding) species of different subgenera,Polistes (P.) riparius andP. (Polistella) snelleni, in areas where they cohabited. The overall probability for a nest to be usurped by a foreign foundress during the season was about twice as large inP. snelleni as inP. riparius. In both, however, probability of usurpation was largest on late pre-emergence nests, or in late June and early July. InP. riparius, all the usurpers of known origins were those foundresses that had lost their pre-emergence nests to destruction probably by some vertebrates; inP. snelleni, some usurpers had the same history as above, while the others had lost many of all larvae to predation by unknown agents before worker emergence. Usurpers of both species destroyed eggs and younger larvae to much greater extents than older larvae or pupae, and they produced fewer numbers of reproductives in comparison with non-usurping foundresses. We concluded that usurpation behavior has been maintained despite its relatively low productivity because renesting would lead to even lower or no reproductive production.     

中国吴茱萸属(广义)叶结构特征及其分类学意义北大核心CSCD

该研究以中国产芸香科广义吴茱萸属18种3变种为材料,于体视显微镜下观察叶结构特征。结果发现:(1)吴茱萸属叶脉为羽状脉。(2)二级脉有花环状弓形脉和简单弓形脉两种类型,极少数存在内二级脉,间二级脉存在或缺失。(3)三级脉不规则网状或极少数弱贯穿,边缘三级脉环状。(4)四级脉不规则网状或自由分支。(5)五级脉不规则网状或自由分支,脉间区发育差或中等,游离端小脉末端简单或管状异形,边缘末级脉大多数不完整,极少数环状。(6)基于重要的外部形态学特征和叶结构特征观察结果,编制了广义吴茱萸属植物的分组检索表。研究表明,吴茱萸属这些类群的二级脉与更高级脉序形成的结构极为稳定,同时又存在种间差异,故广义吴茱萸属植物叶结构特征可以为更准确地鉴定一些疑难种和混淆种提供佐证,具有重要的系统分类学价值。     

Evidence for divergent selection between the molecular forms of <Emphasis Type="Italic">Anopheles gambiae</Emphasis>: role of predation

Background  

The molecular forms of Anopheles gambiae are undergoing speciation. They are characterized by a strong assortative mating and they display partial habitat segregation. The M form is mostly found in flooded/irrigated areas whereas the S form dominates in the surrounding areas, but the ecological factors that shape this habitat segregation are not known. Resource competition has been demonstrated between species undergoing divergent selection, but resource competition is not the only factor that can lead to divergence.     

Nutritional benefits of the leaf-mining behaviour of two grass miners: a test of the selective feeding hypothesis

1. The selective feeding hypothesis predicts that miners prefer tissues high in nutrient content and low in chemical and structural defence content. This hypothesis was tested for two dipteran grass miners, Chromatomyia milii and C. nigra, feeding on Holcus lanatus. 2. Leaf sections revealed that both miners preferred to feed on the mesophyll layer, minimised the intake of veinal tissues, and never fed on the epidermal layer. Nutritional quality analyses showed that the mesophyll had a higher nutrient content and a lower structural defence content than the epidermal and veinal tissues. 3. The nutritional quality of mined leaf areas was lower than that of unmined leaf areas, suggesting that the mining larvae remove the most nutritious tissues; however this commonly used approach for studying the selective feeding hypothesis is questioned in this study. 4. Larval feeding rates were higher on the mesophyll than on the veinal tissues, probably due to a higher structural defence content of the veins. Feeding rates were higher on the small veins than on the larger and more sclerified, strengthened veins. 5. This study supports the selective feeding hypothesis as both species concentrated their feeding on the mesophyll, which is the most nutritious and least tough tissue within a H. lanatus leaf.     

Bundle sheath lignification mediates the linkage of leaf hydraulics and venation

The lignification of the leaf vein bundle sheath (BS) has been observed in many species and would reduce conductance from xylem to mesophyll. We hypothesized that lignification of the BS in lower‐order veins would provide benefits for water delivery through the vein hierarchy but that the lignification of higher‐order veins would limit transport capacity from xylem to mesophyll and leaf hydraulic conductance (K_leaf). We further hypothesized that BS lignification would mediate the relationship of K_leaf to vein length per area. We analysed the dependence of K_leaf, and its light response, on the lignification of the BS across vein orders for 11 angiosperm tree species. Eight of 11 species had lignin deposits in the BS of the midrib, and two species additionally only in their secondary veins, and for six species up to their minor veins. Species with lignification of minor veins had a lower hydraulic conductance of xylem and outside‐xylem pathways and lower K_leaf. K_leaf could be strongly predicted by vein length per area and highest lignified vein order (R² = .69). The light‐response of K_leaf was statistically independent of BS lignification. The lignification of the BS is an important determinant of species variation in leaf and thus whole plant water transport.     

Bats benefit from beavers: a facilitative link between aquatic and terrestrial food webs

Bat populations are declining in many areas, partly because up to two-thirds of their wetland habitats have been lost. One natural agent creating wetlands is the beaver, which is recolonizing its former range. Beaver flowages are known for their high production of aquatic invertebrates. We tested the hypothesis that the high numbers of insects emerging from beaver flowages influences their use by foraging bats. We compared bat use and bat numbers above flowages of introduced Canadian beavers Castor canadensis and in nearby control ponds where beavers were absent. The two bat species detected, Eptesicus nilssoni and Myotis daubentoni, used beaver flowages more than non-beaver ponds. This is especially the case for Eptesicus nilssoni. Bats also seemed to forage in larger groups while above beaver ponds compared to the control ponds. Beaver flowages appeared to improve bat habitats. A plausible reason for this could be the high number of insects emerging from beaver ponds. Favouring the beaver in habitat management is a tool for creating suitable conditions for many other species, such as bats. In areas not suited for the beaver, insect production can be achieved by imitating the beaver with man-made impoundments. This is especially important in areas which have lost most of their wetlands.     

Quantitative survey of sieve tube distribution in foliar terminal veins of ten dicot species

Quantitative data on sieve tubes in foliar terminal veins (vein endings) were added to the meager published information from only five dicot species. Correlations with other minor vein configurations were also explored. Leaf samples from ten species of dicots (Oxalis nelsonii, O. pes-capri, O. rubra, O. stricta [Oxalidaceae], Caesalpinia pulcherrima. Glycine max, Trifolium repens [Leguminosae], Ampelamus albidus [Asclepidaceae], Eupatorium rugosum [Asteraceae], and Polygonum convolvulus [Polygonaceae]) were selected for two quantitative procedures: 1) a survey of the arrangement of terminal veins and distribution of sieve tubes in terminal veins in 100 areoles per species using stained leaf clearings; and 2) a search for correlations of sieve tube distribution with number and branching patterns of terminal veins, and with sizes of areoles using image analysis. Two Oxalis species (O. pes-capri and O. stricta) had the smallest areoles and virtually no sieve tubes in any terminal vein. Polygonum convolvulus, at the other extreme, had sieve tubes extending to the tips of most terminal veins. The other species had various intermediate sieve tube configurations. The data indicate that species with few or no sieve tubes associated with their terminal veins, regardless of the number of terminal veins per areole, have smaller areoles. These results may have implications regarding the entry of leaf photosynthates into the vascular system.     

Water temperatures influence the marine area use of Salvelinus alpinus and Salmo trutta

The migratory behaviour and spatial area use of sympatric Arctic charr Salvelinus alpinus and brown trout Salmo trutta were investigated during their marine feeding migration. The likelihood of finding individuals of both species in the inner or outer fjord areas was dependent on water temperature in the inner area (especially for S. alpinus), the temperature difference between the inner and outer areas (especially for S. trutta) and fish fork length (both species). The strongest predictor was the water temperature in the inner area, and particularly S. alpinus left this area and moved to the outer areas with increasing temperatures in the inner area. At 8° C in the inner area, the likelihood of finding S. alpinus in the outer areas was >50%. This predictor had a smaller effect on S. trutta, and the likelihood of finding S. trutta in the outer areas only started to increase at around 14° C. The relationships between temperature and area use did not correspond to the species' optimal growth temperatures, but to their previously documented temperature preferences. Individuals of both species used mainly the littoral fjord areas, and to a lesser extent the pelagic areas. In conclusion, temperature differences between the inner and outer marine areas probably resulted in the segregated area use between the species, because water temperatures or factors influenced by temperature affected their migratory behaviour and habitat use differently. The results indicate that increased marine temperatures with global warming may lead to increased spatial overlap between S. trutta and S. alpinus, which again may lead to increased interspecific competition during their marine phase, and with S. alpinus probably being the more negatively affected.     

First fossil evidence of samaras of Ventilago Gaertn. (Rhamnaceae) from India and its implications

The Ventilago Gaertn. (Rhamnaceae) is widely distributed in pantropical areas of Africa, Asia, and Australia. However, fossil records of this taxon are sparse, which limits understanding of the evolution and biogeographic history of the genus. In the present study, we report and describe two new fossil species of Ventilago, V. siwalika sp. nov. from the Miocene sediments of Himachal Pradesh, western Himalaya, and V. pliocenica sp. nov. from the Pliocene sediments of Jharkhand, eastern India based on single-winged samaras. Ventilago pliocenica is characterized by a prominent midvein, obtuse to sub-round apex with mucronate tip, longitudinal secondary veins extending the full length of the fruit, and reticulate nature of higher-order veins, the presence of equatorial rim, the hypanthium, and short pedicel. On the other hand, V. siwalika is characterized by a prominent midvein, obtuse to sub-round apex with mucronate tip, longitudinal secondary veins extending the full length of the fruit, and reticulate nature of higher-order veins. Our discovery represents the first unambiguous fossil record of single-winged samara of Ventilago from India and provides valuable insights into the evolution of this genus. In this paper, we also review its biogeographic history and add new information to understand its hypothetical migration route. Present and earlier records of Ventilago also suggest that this genus was a common forest element during Neogene (Miocene time) in Asia.     

The Rete tibiotarsale and Arteriovenous Association in the Hind Limb of Birds: A Compartive Morphological Study on Counter-current Heat Exchange Systems

Arterio-venous association was investigated in the tibial region of 66 bird species representing 21 orders. An intermingled network of arteries and veins (rete tibiotarsale) was found in all stages of complication, ranging from the most simple with only 3 arteries and 5–7 veins (tinamou and owl) to the most elaborate types with more than 60 arteries and 40 veins (flamingo). As opposed to what has hitherto been believed, elaborate retia are present in many short-legged species, while most of the long-legged wading birds only have retia of a very simple type. Arctic forms of eider ducks were found to possess elaborate retia comparable to those in other ducks. In species lacking the rete tibiotarsale, the single artery and its counter-current veins are forming a venae comitantes system. The number of counter-current veins increases with foot size and in ravens and crows up to 8 veins were surrounding the artery, resembling the pattern described in the fins of whales. In species of gulls and guillemots, the contact surface between the veins and the artery appeared to be higher in arctic forms than in more southerly distributed birds. The findings are discussed in relation to heat economy, foot size, and ecology of the species. Further, theories for the evolution of the different types of heat exchange systems are presented. It is concluded that no single selective factor can explain the evolution and occurrence of the rete tibiotarsale.     

Action of mephosfolan on anthocorid predators of Phorodon humuli

In glasshouse and field studies, soil drenches of the systemic insecticide mephosfolan were applied to hop plants to control the aphid Phorodon humuli, and to study the toxicity to anthocorid predators. The mortality of Anthocoris nemorum and A. nemoralis eggs in the leaf tissues increased with the dosage of mephosfolan while A. confusus eggs, which were laid in the petioles and veins, appeared to be unaffected at the dosages used, up to 2 g a.i./plant. Mortality of A. nemorum eggs, which were laid mainly in the leaf margins, was higher than in A. nemoralis eggs, which were laid mainly in the interveinal areas. For both species mortality was highest for the eggs laid in the leaf margins, and susceptibilities appeared similar. It is suggested that mephosfolan becomes unevenly distributed within the leaves, being most concentrated in the leaf margins and least concentrated in the veins and petioles. No species showed any preference when offered mephosfolan-treated and untreated leaves for oviposition, and the oviposition rates were unaffected by various mephosfolan dosages. Oviposition rates, larval mortality and duration of larval development were unaffected when specimens of each species were reared from eclosion to maturity on a diet of either mephosfolan-killed or heat-killed P. humuli.     

Impatiens pingxiangensis sp. nov. (Balsaminaceae) from the limestone areas in Guangxi,China

Impatiens pingxiangensis H. Y. Bi & S. X. Yu (Balsaminaceae), a new species from the limestone areas in Guangxi, China, is described and illustrated. The new species is similar to I. obesa in having succulent stems, subsessile peduncle, tufted pedicel and the lower petal in each pair of lateral united petals being connate, but differs from the latter by having perennial stems, leaf blades with 7–9 pairs of lateral veins, 1–2‐flowered racemes, ovate inner lateral sepals, and elliptic capsule. Moreover, the pollen and seed coat characters also support the recognition of the new species.     

Effect of chronological addition of records to species distribution maps: The case of Tonatia saurophila maresi (Chiroptera,Phyllostomidae) in South America

Ecological niche models have become very popular for analysing the potential distribution of species. Nevertheless, models are strongly influenced by many factors, such as spatial resolution, environmental variables and the quality of distribution records. In this paper, we evaluated how ecological niche models changed with the addition of records accumulated over four decades. Our model species was the stripe‐headed round‐eared bat (Tonatia saurophila). Thus, with data organized in chronological order, we could observe how the models changed in predicting distributions over time in comparison with all known point locations. We tested if partial models could predict the occurrence of new unpublished records for savannah areas in central Brazil, considering that the species is typically associated with forest environments. Our results indicate a high omission rate for models built with point localities from the 1970s and 1980s (58.5% and 50.0% of all known points respectively), and predicted that the species could occur in central Brazil. Although T. saurophila has indeed been recorded recently in central Brazil, it was found in places different from those predicted by the models using these restricted earlier data. Nevertheless, the environmental suitability of such areas is significantly different from sites largely described in earlier records from the Amazonia region, as shown by principal components analysis. We argue that populations of T. saurophila that occupy open habitats in central South America (including Caatinga, Cerrado, Chaco and semi‐deciduous interior forests) deserve further study at the genetic level to determine if bats in these very different habitats are taxonomically distinct from Amazonian populations. Our results also suggest that models based on very limited datasets for species occurrence can lead conservationists or decision makers to wrong conclusions.     

Geographical distribution of the black howler (Alouatta pigra) in Central America

The geographic range of the black howler,Alouatta pigra in Mexico, Guatemala, and Belize was investigated by travelling through and visiting 65 locations within or close to the expected range. The existence of the species was noted through first hand observations or was documented by talking with residents and knowledgeable people in the area. Observations were made on captive animals as well. All sites and probable sites ofA. pigra were noted to be under 1,300 ft in altitude and in areas with a mean annual temperature above 25°C and a mean annual rainfall over 1,000 mm per year. This area coincides with tropical rain forest areas, including both tropical evergreen and semievergreen rain forests.A. pigra was most plentiful in riverine areas which showed flooding for some part of the year. Two areas of possible sympatry withA. palliata were noted. In all cases, the troop sizes ofA. pigra were extremely small, under ten individuals, and infants could easily be sexed, in contrast toA. palliata which is known to occur in troops of 15–18 and is difficult to sex at an early age. Finally, a very gross method for population estimation from searching time emerged from the study.     

The role of different slug species in damage to oilseed rape bordering on sown wildflower strips

Damage caused by different slug species on above and below ground parts of young oilseed rape bordering on sown wildfower strips was studied. Slug densities and damage were recorded in the field and damage rates for each slug species were measured in the laboratory. Severe slug damage was observed in rape areas 1 m from the wildflower strips. Damage rates of slug species feeding above ground were distinctly higher than those feeding below ground. The estimated damage caused by above-ground feeding in all four study fields ranged between 72% and 89 % and was always distinctly higher than damage caused by below-ground feeding (11% to 28 %). The estimated damage caused by Arion lusitanicus above ground was between 54% and 69 %, followed by Deroceras reticulatum (3% to 26 %). Thus A. lusitanicus was responsible for the majority of damage in the rape crops studied.     

The effects of grazing and nutrient inputs on grass-heather competition

Summary

A combination of field and pot experiments was used to investigate the relative importance of grazing pressure and resource availability in grass-heather competition. In pots where nutrients were added, Nardus acquired the additional nutrients more rapidly than Calluna and increased its above-ground biomass to a greater extent. However, in the field, when fencing and fertilizer treatments were applied to a fine-scale mosaic of Calluna and grasses, including Nardus, nutrient addition only benefited Nardus in unfenced areas. In areas where sheep and deer were excluded, nitrogen addition increased heather cover; Nardus cover declined despite the added nutrients, possibly because the absence of grazing allowed heather to close its canopy above the Nardus, a shade-intolerant species. Effects were site dependent, with fencing increasing heather cover more rapidly on some plots than others; sites where grass cover was declining were the ones where grasses showed the smallest uptake of fertilizer. The results demonstrate that nitrogen additions well above the suggested critical load for heather moorland do not lead to a significant loss of heather cover if herbivory is absent, at least not within three years. It is suggested that the loss of heather moorlands to grass-dominated vegetation in Scotland may principally be driven by grazing, rather than nutrients.     

EVOLSONIA,A NEW GENUS OF GIGANTOPTERIDACEAE FROM THE LOWER PERMIAN VALE FORMATION,NORTH-CENTRAL TEXAS

Evolsonia is a new gigantopterid genus (type-species: E. texana), based on leaf impressions from 3 widely separated localities in north-central Texas. The leaves are associated with terrestrial vertebrates in floodplain sediments of the Vale Formation in the Clear Fork Group, of late Leonardian (Early Permian) age. Evolsonia leaves are simple, with very large elliptic laminae reaching 27 cm in width and 80 cm, possibly more, in length. Leaf margins are sinuate to crenate, with mostly shallow concavities. Venation is pinnate, in 4 orders; all but the ultimate veins are very thick and protrude below the lamina, creating deep impressions in the matrix. The secondary and tertiary veins form a precise herringbone pattern, with the secondaries and exmedial tertiaries ending at the leaf margin between concavities. The other tertiary veins are either simple or divided into 2 nearly equal divisions; they produce simple or variously divided quaternary veins that end at a thin sutural vein, forming a dense reticulum; some of the terminally branched tertiaries delimit areolelike areas that enclose several quaternaries and meshes. One of 6 presently known American gigantopterids, Evolsonia most closely resembles the younger Delnortea in gross architecture; with its sutures and dichotomously divided veins, however, Evolsonia is architecturally intermediate between Delnortea and the older American gigantopterids with forked leaves. Sedimentary features indicate deposition under alternating periods of flooding and drought. Their huge size invites comparison of Evolsonia leaves with those of modern tropical plants, whereas their thick veins and preservational features suggest thick, coriaceous texture.     

Taxonomic studies in the Miconieae (Melastomataceae). VII. Miconia howardiana,a new speices from Hispaniola

Miconia howardiana, which is known only from a diverse moist montane forest in the vicinity of Loma Trocha de Pey (or “Monteada Nueva”), the easternmost peak of the Sierra de Baoruco, is described and illustrated. It is compared to phenetically similar (and probably phylogenetically related) species of theMiconia favosa complex, i.e.,M. favosa, M. xenotricha, M. campanensis M. Sintenisii, M. foveolata, andM. pycnoneura. The species of this complex are characterized by bullate leaves with frequently cordate bases and often six secondary veins. Most species also have large berries and flowers, 5-locular ovaries, large inflorescence bracts and bracteoles, and more or less dendritic multicellular hairs.     

Farming with native bees (<Emphasis Type="Italic">Apis mellifera</Emphasis> subsp. <Emphasis Type="Italic">capensis</Emphasis> Esch.) has varied effects on nectar-feeding bird communities in South African fynbos vegetation

Outside their natural range, honeybees (Apis mellifera) are known to have detrimental effects on indigenous pollinators through exploitative or interference competition, but little is known about the effect of honeybee farming in areas where honeybees occur naturally. In the Cape Floristic Region of South Africa, where honeybees are indigenous, managed hives potentially elevate the abundance of honeybees far above natural levels, but impacts on other floral resource-dependent species have not been studied. Here we use experimental manipulation of honeybee density to test whether honeybee farming affects nectar-feeding birds. We selected the common sugarbush (Protea repens), utilized by both birds and bees, and analysed the time (before/after) by treatment (control/experiment) interaction to explore changes in bee abundance, nectar availability and bird abundance at three sites. Hive addition increased honeybee abundance in inflorescences of P. repens above expected levels. Despite experimental increase in honeybee numbers, there is no reduction in nectar sugar availability relative to the control areas. Where honeybee density was highest, sugarbird (Promerops cafer) numbers declined relative to expected, but sunbirds (Nectarinidae) were not affected at any of the sites. We conclude that stocking rates of more than one honey bee per P. repens inflorescence have detrimental effects on bird abundance due to interference, rather than resource competition.