Inflorescences of Neotropical herbs as a newly discovered microhabitat for myxomycetes

An assemblage of myxomycetes associated with inflorescences of large Neotropical herbs, a microhabitat not previously known to support these organisms, is described and characterized ecologically from a number of study sites in Costa Rica, Ecuador, and Puerto Rico. Thirty-one different taxa were found among 652 specimens of myxomycetes recorded in the field or obtained from 358 moist chamber cultures prepared with decaying floral parts. A comparison with the results of 696 moist chamber cultures prepared with various other litter substrates showed that thirteen myxomycete taxa occurred more often on inflorescences. Six taxa had a strong preference for this microhabitat, and three of those seem to be new for the Neotropics. Correspondence analysis of the data set compiled for inflorescences indicated that the assemblage of myxomycetes was relatively consistent across all of the various study sites. The actual myxomycete substrates were the rapidly decaying floral parts enclosed by the massive, still living bracts. Richest in myxomycetes were species of Heliconia and Costus. Here, nectar residuals probably promoted a rapidly developing community of yeasts and bacteria. A high density of these organisms was indicated by the frequent occurrence of myxobacteria in the moist chamber cultures prepared with floral parts. Results from canonical correspondence analysis suggested that a substrate pH between 8 and 9 and the presence of massive, compact inflorescences on plants occurring at lower elevations in localities with moderate annual rainfall provide optimal conditions for inflorescence-inhabiting myxomycetes. An incidental dispersal of myxomycete spores by birds that pollinate the flowers or feed upon the fruits seems possible and may have accounted for the high degree of preference exhibited by some of the inflorescence-inhabiting myxomycetes, for which the term "floricolous" is proposed.     

Checklist of the helminth parasites of vertebrates in Costa Rica

Helminth parasites of vertebrates have been studied in Costa Rica for more than 50 years. Survey work on this group of parasites is far from complete. We assembled a database with all the records of helminth parasites of wild and domestic vertebrates in Costa Rica. Information was obtained from different sources such as literature search (all published accounts) and parasite collections. Here we present a checklist with a parasite-host list as well as a host-parasite list. Up to now, 303 species have been recorded, including 81 species of digeneans, 23 monogeneans, 63 cestodes, 12 acanthocephalans, and 124 nematodes. In total, 108 species of vertebrates have been studied for helminths in Costa Rica (31 species of fishes, 7 amphibians, 14 reptiles, 20 birds, and 36 mammals). This represents only 3.8% of the vertebrate fauna of Costa Rica since about 2,855 species of vertebrates occur in the country. Interestingly, 58 species (19.1 %) were recorded as new species from Costa Rica and most of them are endemic to particular regions. Considering the valuable information that parasites provide because it is synergistic with all the information about the natural history of the hosts, helminth parasites of vertebrates in Costa Rica should be considered within any initiatives to accomplish the national inventory of biological resources. Starting with this compilation work, the Colección de Helmintos de Costa Rica (CHCR), hosted at the Facultad de Microbiología, Universidad de Costa Rica, has re-emerged and it is our hope that it will have the standards of quality to assure that it will become the national depository of helminths in the country.     

The genera of Chrysomelinae (Coleoptera: Chrysomelidae) in Costa Rica

Keys in Spanish and English are given for the genera of Chrysomelinae known from Costa Rica. For each genus, a list of species compiled from collections in the University of Costa Rica, the National Biodiversity Institute, and the entomological literature is presented. The genus Planagetes Chevrolat 1843 is recorded for the first time from Central America, and the genus Leptinotarsa St?l 1858 is synonymized with Stilodes Chevrolat 1843.     

陕西周至老县城自然保护区天然林物种组成及主要种群生态位

采用样方法对陕西周至老县城自然保护区森林植物群落进行调查,运用生态位宽度(B)、生态位重叠值(L)及生态位相似比例(C)指标对主要乔木种群的生态位特征进行测定与分析,探讨植物种群在群落中的地位和作用以及彼此间的竞争关系。结果表明:(1)经调查老县城自然保护区共记录到植物物种243种,隶属于64科159属;分为3个植被型、9个群系。(2)主要乔木种群中,华山松和锐齿槲栎的生态位宽度较大,其Bi、Ba值分别为0.654、0.699和0.534、0.460;短柄枹栎和兴山榆的生态位宽度较小,其Bi、Ba值分别为0.064、0.023和0.049、0.016。(3)白桦和太白杨、糙皮桦和山杨种对的生态位重叠值和生态位相似性比例均较大,其Lij、Lji分别为0.108、0.114和0.089、0.128,Cij分别为0.939和0.744。优势种间的生态位重叠值和生态位相似比例总体较小,表明在现阶段群落演替中,植物对环境资源的竞争不激烈,物种空间异质性低。     

Diversity of the free-living marine and freshwater Copepoda (Crustacea) in Costa Rica: a review

The studies on marine copepods of Costa Rica started in the 1990’s and focused on the largest coastal-estuarine systems in the country, particularly along the Pacific coast. Diversity is widely variable among these systems: 40 species have been recorded in the Culebra Bay influenced by upwelling, northern Pacific coast, only 12 in the Gulf of Nicoya estuarine system, and 38 in Golfo Dulce, an anoxic basin in the southern Pacific coast of the country. Freshwater environments of Costa Rica are known to harbor a moderate diversity of continental copepods (25 species), which includes 6 calanoids, 17 cyclopoids and only two harpacticoids. Of the +100 freshwater species recorded in Central America, six are known only from Costa Rica, and one appears to be endemic to this country. The freshwater copepod fauna of Costa Rica is clearly the best known in Central America. Overall, six of the 10 orders of Copepoda are reported from Costa Rica. A previous summary by 2001 of the free-living copepod diversity in the country included 80 marine species (67 pelagic, 13 benthic). By 2009, the number of marine species increased to 209: 164 from the Pacific (49% of the copepod fauna from the Eastern Tropical Pacific) and 45 from the Caribbean coast (8% of species known from the Caribbean Basin). Both the Caribbean and Pacific species lists are growing. Additional collections of copepods at Cocos Island, an oceanic island 530 km away of the Pacific coast, have revealed many new records, including five new marine species from Costa Rica. Currently, the known diversity of marine copepods of Costa Rica is still in development and represents up to 52.6% of the total marine microcrustaceans recorded in the country. Future sampling and taxonomic efforts in the marine habitats should emphasize oceanic environments including deep waters but also littoral communities. Several Costa Rican records of freshwater copepods are likely to represent undescribed species. Also, the biogeographic relevance of the inland copepod fauna of Costa Rica requires more detailed surveys.     

Distribution and occurrence of myxomycetes on agricultural ground litter and forest floor litter in Thailand

The ecological distribution and seasonal patterns of occurrence of myxomycetes associated with the microhabitats represented by agricultural ground litter and forest floor litter were investigated in six study sites in northern Thailand during Oct 2004-Oct 2005. Both specimens that developed under natural conditions in the field and specimens obtained in moist chamber cultures were considered. Agricultural study sites were a banana plantation, a mango orchard and a sweet corn farm, whereas forest study sites consisted of a lowland forest, a midelevation forest and a highland forest. Seventy species of myxomycetes representing 20 genera were collected, with 34 species recorded during the dry season and 58 species recorded during the rainy season. Distinct differences were apparent for numbers of positive moist chambers, numbers of species recorded from moist chambers, numbers of species recorded as field collections and numbers of field collections when data obtained for the two seasons were compared. In the dry season only three species were collected in the field, but the percentage of positive moist chamber cultures (129/180 or 72%) and number of species recorded (33) from these cultures were high. In contrast, during the rainy season, 52 species of myxomycetes were collected in the field but only 15 species were recorded from the much lower percentage (75/180 or 42%) of positive moist chambers cultures.     

The effect of social dominance on foraging by the Three-toed Woodpecker Picoides tridactylus

During the winter, female Three-toed Woodpeckers Picoides tridactylus , when unaccompanied by the male, foraged at a lower height above the ground and on tree trunks of greater diameter than when foraging together with a male. Among males, however, no such differences were found between those birds foraging in the absence of, or in company with, a female. The niche breadth of the males was less than that of the females, indicating a higher degree of specialization by the males. The niche overlap between the sexes was less when the birds foraged together in pairs, especially as regards foraging height and foraging site diameter. The intersexual segregation of foraging niche recorded for the Three-toed Woodpecker is therefore probably not determined genetically, but is due to social dominance by males which obliges the females to occupy the less preferred niche. Both sexes spent less time being vigilant when foraging together, than when alone.     

Contrasting Effects of Intraspecific Trait Variation on Trait-Based Niches and Performance of Legumes in Plant Mixtures

Niche differentiation, assumed to be a key mechanism of species coexistence, requires that species differ in their functional traits. So far it remains unclear to which extent trait plasticity leads to niche shifts of species at higher plant diversity, thereby increasing or decreasing niche overlap between species. To analyse this question it is convenient to measure niches indirectly via the variation in resource-uptake traits rather than directly via the resources used. We provisionally call these indirectly measured niches trait-based niches. We studied shoot- and leaf-morphological characteristics in seven legume species in monoculture and multi-species mixture in experimental grassland. Legume species varied in the extent of trait variation in response to plant diversity. Trait plasticity led to significant shifts in species niches in multiple dimensions. Single-species niches in several traits associated with height growth and filling of canopy space were expanded, while other niche dimensions were compressed or did not change with plant diversity. Niche separation among legumes decreased in dimensions related to height growth and space filling, but increased in dimensions related to leaf size and morphology. The total extent of occupied niche space was larger in mixture than in the combined monocultures for dimensions related to leaf morphology and smaller for dimensions related to whole-plant architecture. Taller growth, greater space filling and greater plasticity in shoot height were positively, while larger values and greater plasticity in specific leaf area were negatively related with increased performance of species in mixture. Our study shows that trait variation in response to plant diversity shifts species niches along trait axes. Plastically increased niche differentiation is restricted to niche dimensions that are apparently not related to size-dependent differences between species, but functional equivalence (convergence in height growth) rather than complementarity (divergence in traits associated with light acquisition) explains increased performance of legumes in mixture.     

Addendum to the checklist of the helminth parasites of vertebrates in Costa Rica

In this work, we present an addendum to the "Checklist of the helminth parasites of vertebrates in Costa Rica" with a parasite-host list as well as a host-parasite list. This addendum updates the available information on this group of parasites in Costa Rica, since very recently a new input has been made to describe the helminth fauna of vertebrates, particularly at the Area de Conservación de Guanacaste. In this paper, we add 33 records, representing 23 species. This raises the number of helminth species described in vertebrates from Costa Rica to 325, represented by 89 species of digeneans, 23 of monogeneans. 63 of cestodes, 13 of acanthocephalans, and 137 of nematodes. In total, 133 species of vertebrates have been studied for helminths in Costa Rica (31 species of fishes. 7 amphibians, 18 reptiles, 40 birds, and 37 mammals). Currently, 67 species (20.6 %) have been recorded as new species from Costa Rica and most of them are endemic to particular regions. The Colecci6n de Helmintos de Costa Rica, housed at the Universidad de Costa Rica (UCR), San José, is the depositary of only 23% of the species recorded so far; however this situation is changing and people recognizes.     

Rapid assessment of the distribution of myxomycetes in a southwestern Amazon forest

The distribution of fruit bodies of myxomycetes under different ecological conditions at the Los Amigos Biological Station in southeastern Peru was studied. Six study areas were surveyed using a combined field-laboratory methodology under different climatic conditions. Sixty species were recorded and differences in fruit body abundance and structure of the assemblages were found among collecting periods. A diversity analysis based on fruit bodies showed that values were predominantly higher during the dry period. An analysis of microenvironmental conditions applied to a subset of data collected in the field showed that pH and substratum diameter accounted for most of the variation. In addition, the most abundant myxomycetes based on fruit body occurrence showed a multivariate arrangement that suggests the existence of functional groups.     

Spatiotemporal distribution and dynamic changes of myxomycetes in subtropical forests of China

The spatiotemporal distribution and dynamic changes of species composition of myxomycetes in humid subtropical forests of Houhe National Nature Reserve in southern China were studied by collecting samples of bark and ground litter within four seasons for isolation of myxomycetes in moist chamber cultures and by collecting fruiting bodies in the field from June to October. A total of 725 specimens of myxomycete fruiting bodies representing 77 species of 25 genera were registered, among them 302 records/51 species from field collections and 423 records obtained from 600 moist chamber cultures of ground litter and bark of living trees, which resulted in 35 and 39 species, respectively. Cornuvia serpula and Perichaena microspora were recorded for the first time in China. Both myxomycete species richness and diversity were significantly different in ground litter among sites and field collections among months. NMDS combined with Permanova indicated that the site had a greater impact on the myxomycete community of bark and litter than the season, while the month of field collections had a greater impact than the sampling sites. CCA and VPA analysis showed that the bark-inhabiting myxomycete species were mainly affected by spatial variables, while the litter-inhabiting and field collected species were more affected by climatic factors.     

A preliminary survey of the Chironomidae (Diptera) of Costa Rica,with emphasis on the lotic fauna

Extensive collections of Chironomidae were made in Costa Rica, Central America, during 1986 and 1987. Fifty-five genera and at least 148 species belonging to the subfamilies Podonominae, Tanypodinae, Orthocladiinae and Chironomidae were found. Chironominae and Orthocladiinae predominated. Only one species of Podonominae was collected. Tanypodinae was represented by many genera, but species richness was low.Cricotopus was the most widespread and diverse genus of Orthocladiinae. Among the Chironominae the generaPolypedilum, Pseudochironomus, Tanytarsus andRheotanytarsus showed high species richness. Several species were collected that could not be assigned to genus. A number of range extensions were recorded for taxa found in the Neotropical region for the first time and for Neotropical taxa recorded outside of South America for the first time. The Costa Rican chironomid fauna consists of cosmopolitan, holarctic and neotropical components. There is probably an endemic Central American chironomid fauna at the species level.     

Food niche overlap among neotropical frugivorous bats in Costa Rica

Food habits of 15 species of frugivorous bats were studied at La Selva Biological Station, Costa Rica. Eight hundred and fifty-four (854) fecal samples and 169 samples from fruit parts and seeds discarded by bats beneath feeding roosts were analyzed. During eight months of study, 47 fruit species consumed by bats were identified. Five plant genera (Cecropia, Ficus, Piper Solanum, and Vismia) constituted 85% of all plants found in fecal samples. Feeding niche breadth differed significantly among the six most common species of frugivorous bats (Artibeus jamaicensis, Carollia sowelli, C. castanea, C. perspicillata, Dermanura sp., and Glossophaga commissarisi). All species, except for Dermanura sp., showed a diet dominated by one or two plant species. This suggests a pattern of resource partitioning at a generic level, in which Carollia consumed mainly Piper, Artibeus consumed Ficus and Cecropia, and Glossophaga consumed Vismia. Cluster analysis revealed higher values of food niche overlap in congeneric species than among species of different genera. Results show that if food is a limiting factor, mechanisms other than trophic selection must reduce interspecific interference or competition for food in this frugivorous bat guild.     

福建三明钩栲种群与主要伴生树种生态位研究

采用Levins生态位宽度及重叠、Shannon-Wiener生态位宽度测度式,定量分析福建三明钩栲群落8个主要伴生树种的生态位宽度、生态位重叠。结果表明,该群落中优势种的生态位宽度值均普遍较大;生态位宽的种群对生态位窄的种群可能有较大的重叠值,反之则低;揭示钩栲的生态位特征及空间分布格局,对今后生产实践具有一定的参考价值。     

渔山岛岩礁基质潮间带大型底栖动物优势种生态位

2009年3月至2010年1月期间对渔山岛岩礁基质潮间带大型底栖动物进行定量采样调查,并获得大型底栖动物85种,筛选出全年取样获得优势种30种,隶属5门7纲24科。对获得的30个优势种以Shannon—Wiener指数为基础进行了生态位宽度测定,以Pianka重叠指数为基础进行了生态位重叠值分析,结果显示：潮间带大型底栖动物群落中优势种生态位宽度变化范围为0.18~1.94,值较高的有条纹隔贻贝、覆瓦小蛇螺、角偏顶蛤、日本笠藤壶、鳞笠藤壶和马氏毛粒蟹,均大于1.00,它们对环境适应的能力较强;各优势种的生态位重叠程度不均匀,在0~0.97之间,它们对群落环境资源的利用存在着交叉,潜在的种间竞争压力较大。以密度数据四次开方为基础,利用欧氏距离进行群落物种的系统聚类分析和非度量多维标度排序分析,结果均表明30个优势种可以分为三大类,即狭布种、泛化种和特有种。优势种生态位宽度、优势种之间的生态位重叠值与物种的分布与数量密切相关,生境相似程度高的物种聚类和排序距离就小,大型底栖动物主要通过在资源位上的分布、摄食类群和生活型等的差异缓解竞争。     

Niche conservatism among non‐native vertebrates in Europe and North America

Niche conservatism, the hypothesis that niches remain constant through time and space, is crucial for the study of biological invasions as it underlies native‐range based predictions of invasion risk. Niche changes between native and non‐native populations are increasingly reported. However, it has been argued that these changes arise mainly because in their novel range, species occupy only a subset of the environments they inhabit in their native range, and not because they expand into environments entirely novel to them. Here, using occurrences of 29 vertebrate species native to either Europe or North America and introduced into the other continent, we assess the prevalence of niche changes between native and non‐native populations and assess whether the changes detected are caused primarily by native niche unfilling in the non‐native range rather than by expansion into novel environments. We show that niche overlap between native and non‐native populations is generally low because of a large degree of niche unfilling in the non‐native range. This most probably reflects an ongoing colonization of the novel range, as niche changes were smaller for species that were introduced longer ago and into a larger number of locations. Niche expansion was rare, and for the few species exhibiting larger amounts of niche overlap, an unfilling of the niche in the native range (e.g. through competition or dispersal limitations) is the most probable explanation. The fact that for most species, the realized non‐native niche is a subset of the realized native niche allows native‐range based niche models to generate accurate predictions of invasion risk. These results suggest that niche changes arising during biological invasions are strongly influenced by propagule pressure and colonization processes, and we argue that introduction history should be taken into account when evaluating niche conservatism in the context of biological invasions.     

鼢鼠土丘植被演替过程中的种的生态位分析

一、引言在甘南亚高山草甸草场上,鼢鼠掘洞,其抛出物形成土丘,破坏了草场自然植被,同时也开始了恢复演替的过程。此演替过程主要由两种因子促成:一是由人畜践踏和自然落实而致的土丘紧实度的增加;二是先后侵入土丘的群落组分种的种间竞争。整个演替系列,以萼果香薷等相对的r 对策种的侵入开始,最后嵩     

青海省海东地区小型兽空间生态位分析

采用Shannon-Wiener生态位宽度指数和Pianka生态位重叠指数对青海省海东地区不同生境的小型兽类群落进行研究.结果发现,捕获的18种小型兽中,柴达木根田鼠(Microtus limnophilus)的生态位宽度值最大(0.940),洮州绒孵(Caryomys eva)、黑线姬鼠(Apodemus agrar...     

Niche and Neutral Processes Together Determine Diversity Loss in Response to Fertilization in an Alpine Meadow Community

Fertilization via nutrient deposition and agricultural inputs is one of the most important factors driving decreases in plant diversity. However, we still do not fully understand which processes (niche process or neutral process) are more important in leading to decreases in plant diversity caused by fertilization. A hypothesis-based approach was used to test the relative importance of niche versus neutral processes along a fertilization gradient in an alpine meadow community on the eastern Tibetan plateau, China. Niche overlap values were calculated for species biomass, and the null model was used to generate the values of niche overlap expected at random. A linear regression modeling was used to evaluate the relationship between functional traits (specific leaf area, leaf dry matter content, and leaf total nitrogen concentration) and species relative abundance. Our results demonstrated that observed niche overlap for species biomass was significantly higher than expected at lower fertilization gradients. Moreover, we also found a significantly negative correlation between species relative abundance and specific leaf area and leaf dry matter content, but a significantly positive correlation between relative abundance and leaf nitrogen concentration at lower fertilization gradients. However, these relationships were not significant at higher fertilization gradients. We concluded that community assembly is dynamic progression along the environmental gradients, and niche and neutral processes may together determine species diversity loss in response to fertilization.