Tri-trophic interactions affect density dependence of seed fate in a tropical forest palm

Natural enemies, especially host-specific enemies, are hypothesised to facilitate the coexistence of plant species by disproportionately inflicting more damage at increasing host abundance. However, few studies have assessed such Janzen-Connell mechanisms on a scale relevant for coexistence and no study has evaluated potential top-down influences on the specialized pests. We quantified seed predation by specialist invertebrates and generalist vertebrates, as well as larval predation on these invertebrates, for the Neotropical palm Attalea butyracea across ten 4-ha plots spanning 20-fold variation in palm density. As palm density increased, seed attack by bruchid beetles increased, whereas seed predation by rodents held constant. But because rodent predation on bruchid larvae increased disproportionately with increasing palm density, bruchid emergence rates and total seed predation by rodents and bruchids combined were both density-independent. Our results demonstrate that top-down effects can limit the potential of host-specific insects to induce negative-density dependence in plant populations.     

The enigma of guanacos in the Falkland Islands: the legacy of John Hamilton

Aim To address the biogeographical enigma of why guanacos (Lama guanicoe) are in the Falkland Islands we investigated the following questions: (1) What was the origin of the introduced guanacos? (2) What were the initial population sizes? (3) Why are they found only on one island? and (4) Who was John Hamilton and what role did he play? Location The Falkland Islands are located in the South Atlantic Ocean 600 km east of Patagonia at the southern end of South America. While dominated by East and West Falkland Islands, the archipelago is composed of some 750 islands. Sedge and Staats Islands, two small outlying islands of West Falkland, are the focus of this paper. Methods Historical information was collected from known relevant documents housed at the Falkland Islands Government Archives in Stanley, and personal interviews conducted with past and present residents of West Falklands. Research expeditions were made to Staats Island in 1999, 2002 and 2003 to assess the guanaco population size, distribution and social structure. Results Guanacos were unsuccessfully introduced in 1862 to East Falkland south of Mt Pleasant where Prince Alfred hunted them in 1871. John Hamilton, Scottish immigrant to the Falklands and Patagonia of southern Argentina and Chile, was the driving force in the introduction of guanacos from the region of Rio Gallegos, Argentina during the 1930s. The guanaco was one of several wildlife species he introduced, however, only the guanaco, Patagonia grey fox (Dusicyon griseus) and perhaps the sea otter (Lutra felina) survive. Hamilton's acting agent, Jimmy Miller, imported four shipments totalling 26 guanacos from 1934 to 1939. In 1934 the Falkland Government authorized Miller to introduce guanacos to Sedge Island, all 11 of which disappeared. Whether intentional or accidental, 15 guanacos were taken to Staats Island, an islet of 500 ha on the western edge of the archipelago. Historically, guanacos are unexpected on Staats Island because documentation authorizing their introduction is unknown. Guanaco numbers have fluctuated widely on Staats Island for 65 years primarily due to culling. In 1959 the population was dangerously close to extirpation, but today 400 thrive there. A severely reduced gene pool and genetic bottlenecking were suggested by recent field studies, revealing preliminary evidence of deleterious consequences of inbreeding. Main conclusions John Hamilton, spirited and visionary Scottish immigrant to the Falklands in the early 1880s, was responsible for the introduction of guanacos into the Falkland Islands. While there are some gaps in the historical events, the enigma of how and why guanacos were introduced to a single island in the South Atlantic Ocean is understood. Today, Staats Island, as a closed system, is a rare natural experiment in progress. It offers unique opportunities for addressing advanced questions in ungulate population, behavioural and genetic ecology. The population potentially also represents breeding stock for farming the guanaco's highly valuable wool on other islands. Thus, among his many efforts to practice land stewardship and promote economic diversity through the introduction of Patagonian wildlife, a remaining legacy of John Hamilton to the Falkland Islands is unmistakably the guanacos of Staats Island.     

MORPHOLOGICAL VARIABILITY OF EUNOTIA PECTINALIS (BACILLARIOPHYCEAE) IN A SOFTWATER RHODE ISLAND STREAM AND IN CULTURE1

The diatom Eunotia pectinalis (O. F. Müll.?) Rabh. exhibited considerable morphological variability in samples collected over a 13-month period from a softwater Rhode Island stream. All observed morphotypes were classified into three main complexes based upon their valve configuration. These groupings were confirmed by discriminant analysis using quantitative valve characteristics and were named in accordance with their associated varieties: minor (Kütz.) Rabh., pectinalis and ventricosa Grun. Clonal cultures were subjected to a defined series of temperatures, agitation rates and light intensities in order to assess inherent morphological variability. Similar trends were evident for all complexes. Over time, valve length decreased, valve breadth enlarged, and striae number per 10 μm at valve center and apex increased. Morphological plasticity was evident in culture and appeared to be more a function of the clone genotype than the environmental conditions to which it was subjected. One clone originally identified as E. pectinalis var. minor assumed certain morphological features of E. vanheurckii Patr. after four months in culture.     

Allozyme variation in the endangered insular endemic Castilleja grisea

BACKGROUND AND AIMS: Genetic diversity in Castilleja grisea, an endangered, perennial herb endemic to San Clemente Island, California was investigated. Subsequent to the elimination of goats from the island in 1992, many populations of C. grisea have reappeared and have been increasing in size. METHODS: Nineteen populations were surveyed for their genotype at 19 allozyme loci. KEY RESULTS: At the taxon level, 57.9 % of loci are polymorphic with A(P) = 3.09 and H(E) = 0.137. Populations averaged 33.0 % polymorphic loci with A(P) = 2.43 and H(E) = 0.099. Most variation is found within rather than among populations (G(ST) = 0.128), although differentiation among populations is significant. Genetic identities range from I = 0.960 to I = 1.000 with mean I = 0.990. There is no significant relationship between genetic and geographic distance. Gene flow among populations is Nm = 2.50 based on private alleles and Nm = 1.70 based on F(ST). Outcrossing rates based on fixation indices average t = 1.01, indicating a primarily out-crossed mating system. CONCLUSIONS: The observed genetic variation is moderately high, unusually so for an insular endemic species, suggesting that C. grisea may not have lost substantial genetic variation during 150 years of overgrazing, and indicating that it is unlikely to be endangered by genetic factors.     

A novel microsatellite locus isolated from an AFLP fragment in the mangrove species Kandelia obovata (Rhizophoraceae)

The study of AFLP analysis in Kandelia obovata, one of the major mangrove species in Japan, revealed the existence of a unique fragment showing stuttered peaks. We cloned this fragment and found a novel microsatellite locus. We report the method used for isolation and the polymorphic nature of this locus among the populations on Iriomote Island.     

Relationship between diet and helminths in Gallotia caesaris (Sauria: Lacertidae)

Diet and helminth fauna were analysed in Gallotia caesaris, a small lacertid lizard endemic to El Hierro (Canary Islands, Spain) in order to study the evolutionary and functional relationships between the two traits. This species is omnivorous but consumed a high proportion (82.13%) of plant matter including not only seeds but also leaves and other vegetative parts. Helminth fauna included many helminth species typical of herbivorous reptiles. Both herbivory and helminth presence were higher than expected for a lizard of its size. Comparison with other lacertids suggests that both traits result from an adaptation to insular conditions but that some "evolutionary time" to develop them is needed. Canarian Gallotia lizards, a separate lineage evolving for a long time in insularity, constitutes the most advanced lacertid group in this way. Nevertheless, results for G. caesaris indicate that helminth fauna also changes seasonally tracking variation in diet (and herbivory) throughout the year, which suggests a dynamic interaction between diet and helminth parasites.     

Limnology of Crater Lakes in Los Tuxtlas,Mexico

Investigations on the abundance, biomass and position of heterotrophic flagellates (HF) in the benthic microbial food web of a melt water stream on King George Island, Antarctic Peninsula, were undertaken during the Antarctic summer from 23rd December 1997 until 13th March 1998. Abundance and biomass of potential HF resources (picophotoautotrophic and non-photoautotrophic bacteria) as well as potential predators on HF (ciliates and meiofauna) were also investigated. HF abundance ranged from approximately 9 × 10³ to 81 × 10³ cells cm^–3, values which fall into the same range as those found in lower latitudes. Numerically important benthic HF were euglenids, kinetoplastids, thaumatomastigids and especially chrysomonads. Most species identified have been shown to have a worldwide distribution. Abundance of the benthic ciliates ranged from 27 to 950 cells cm^–3. Mean bacterial abundance was 1.9 × 10⁷ and 5.2 × 10⁸ cells cm^–3 for picophotoautotrophic and non-photoautotrophic benthos, respectively. The well-developed microbial community was able to support the large number of nematods, gastotrichs, tardigrads and rotifers with abundances reaching more than 1000 individuals cm^–3. The largest portion of heterotrophic biomass was formed by the meiofauna with a mean of 63 g C cm^–3, followed by that of the heterotrophic bacteria with 4.80 g C cm^–3. Picophotoautotrophic bacteria contributed a mean of 1.37 g C cm^–3. HF and ciliates mean biomass was 0.61 and 1.99 g C cm^–3, respectively, with the HF biomass comprising between <10 and 70% of the total protozoan biomass. The data obtained in this study identify the melt water stream as a hot-spot of heterotrophic microbial and meiofaunal activity during the austral summer. The HF in the melt water stream formed a diverse group in terms of taxa and potential feeding types. Chrysomonads, kinetoplastids, euglenids and thaumatomastigida were the most abundant taxa. A classification into feeding types identified an average of 34% of the total HF as bacterivorous while all others were able to utilise other, larger organisms as resources. Potential trophic interactions between HF and bacteria and higher trophic levels are discussed.     

Nectar and Pollen Sources for Honeybee （Apis cerana cerana Fabr.） in Qinglan Mangrove Area, Hainan Island, China

In the present study, nectar and pollen sources for honeybee （Apls cerana cerana Fabr.） were studied in Qlnglan mangrove area, Hainan Island, China, based on microscopic analysis of honey and pollen load （corblcular and gut contents） from honeybees collected In October and November 2004. Qualitative and quantitative melittopalynologlcal analysis of the natural honey sample showed that the honey is of unlfloral type with Mimosa pudlca L. （Mlmosaceae） as the predominant （89.14%） source of nectar and pollen for A. cerana cerana In October. Members of Araceae are an Important minor （3%-15%） pollen type, whereas those of Arecaceae are a minor （〈3%） pollen type. Pollen grains of Nypa fruticans Wurmb., Rhlzophora spp., Excoecarla agallocha L., Lumnitzera spp., Brugulera spp., Kandella candel Druce, and Ceriops tagal （Perr.） C. B. Rob. are among the notable mangrove texa growing In Qinglan mangrove area recorded as minor taxa In the honey. The absolute pollen count （I.e. the number of pollen grains/10 g honey sample） suggests that the honey belongs to Group V （〉1 000 000）. Pollen analysis from the corblcular and gut contents of A. cerana cerana revealed the highest representation （95.60%） of members of Sonneratia spp. （Sonneratlaceae）, followed by Bruguiera spp. （Rhizophoraceae）, Euphorblaceae, Poaceae, Fabaceae, Arecaceae, Araceae, Anacardlaceae, and Rublaceae. Of these plants, those belonging to Sonneratla plants are the most Important nectar and pollen sources for A. cerana cerana and are frequently foraged and pollinated by these bees in November.     

Effect of Hillslope Gradient on Vegetation Recovery on Abandoned Land of Shifting Cultivation in Hainan Island, South China

In the present study, we investigated the effect of hillslope gradient on vegetation recovery on abandoned land of shifting cultivation In Hainan Island, south China, by measuring community composition and structure of 25-year-old secondary forest fallows along a hillslope gradient （up-, middle-, and down-slope position）. A total of 49 733 free-standing woody plant stems higher than 10 cm and belonging to 170 species, 112 genera, and 57 families was found in the three l-hm2 investigation plots. Stem density was highest in the down-slope stand and lowest in the up-slope stand. Species richness and the Shannon-Wiener Index were both highest in the middle-slope stand, and lower In the down-slope and up-slope stands. The recovery forest fallows on different hiUslope positions were all dominated by a few species. The five most abundant species accounted for 70.1%, 58.8%, and 72.9% of total stem densities in stands in the up-, middle-, and down-slope positions, respectively. The five species with the greatest basal areas accounted for 74.5%, 84.3%, and 74.7% of total stem basal area for the up-, middle-, and down-slope positions, respectively. The number of low-density species （stem abundance less than five） Increased from the up-slope position downward. Of the nine local common species among three different functional groups, the short-lived pioneer species dominated the up-slope position, but long-lived pioneer species dominated the middle- and down-slope positions. The climax species of primary tropical lowland rain forest was found in the downslope position. Both the mean diameter at breast height （DBH） and mean height of the trees Increased with decreasing hillslope gradient. The stem density and basal area in different size classes were significantly different in stands In different slope positions. Our results indicated that the rate of secondary succession varies, even over small spatial scales caused by the hlllslope gradient, in early vegetation recovery.     

海南霸王岭不同森林类型附生兰科植物的多样性和分布

附生兰科植物是热带林附生植物的主要类群之一,对于维持热带林生态系统的物种多样性及生态功能具有重要的作用。以海南岛霸王岭国家级自然保护区内的6种热带原始林类型(热带季雨林、低地雨林、热带针叶林、山地雨林、山地常绿林及山顶矮林)中的附生兰科植物为研究对象,通过样带调查(每个森林类型设置12个10m×50m的样带,记录每个样带内胸径(DBH)≥5cm的树木及藤本上附生兰科植物的物种名称、株数及附生位置)分析了附生兰科植物的物种多样性、附生位置及其在不同森林类型中的分布规律。结果表明:1)3.6hm2森林调查样带内共记录到附生兰科植物9634株,分属于26属60种;2)除趋势对应分析(DCA)结果表明,6种森林类型中的附生兰科植物可分成5组(其中,山地常绿林与山顶矮林内的附生兰科植物归为一组);3)分布海拔范围相临近的森林类型的附生兰科植物具有较高的相似性,山地常绿林和山顶矮林附生兰科植物的相似性最高(88.9%);4)6种森林类型中,较高海拔的3种森林类型(山地雨林、山地常绿林和山顶矮林)中,附生兰科植物的丰富度和多度均显著高于其在较低海拔的3种森林类型(热带季雨林、低地雨林和热带针叶林),其中,附生兰科植物在山地常绿林内的丰富度和多度均最高;5)热带季雨林、低地雨林、热带针叶林及山地雨林内,宿主冠区附生兰科植物的多度均高于干区;山地常绿林内两者之间无显著差异;而山顶矮林干区的附生兰科植物的多度高于冠区;6)调查木上附生兰科植物的发生率在高海拔森林类型均高于其在低海拔森林类型,各森林类型内附生兰科植物的多度及物种丰富度与宿主胸径均存在显著正相关关系。