Microhabitat size distribution affects local difference in community structure: Metazoan communities in treeholes

I studied the effect of treehole (microhabitat) size distribution in local habitats on geographic difference in aquatic metazoan community structure by comparing differences between two sites on Iriomote Island, and between Iriomote Island (subtropical) and Tsushima Island (temperate), in southwestern Japan. In treeholes at each local site, the amount of litter, the species richness and total biomass of metazoa were positively correlated with treehole capacity. Between the two sites on Iriomote Island (Shirahama and Komi), the amount of litter, biomass and species number per treehole was greater at Komi where the mean and variance of treehole size were greater, while the dependencies of these parameters on treehole capacity were common to both sites. Total species number was larger at Komi (2 predators and 20 saprophages) than at Shirahama (1 predator and 19 saprophages). Most of the dominant taxa colonized larger treeholes with higher probabilities, although one taxa showed the opposite trend. Treeholes on Tsushima were smaller than those on Iriomote. The metazoan fauna in treeholes consisted of 15 saprophages on Tsushima, being less richer than that on Iriomote Island which had 2 predators and 21 saprophages. However, the dependencies of litter amount and biomass on treehole capacity did not differ significantly between the islands, although treeholes on Iriomote harbored a greater number of species per treehole than those on Tsushima. This study indicated that there are general correlates between community structure within individual treeholes (infracommunity structure) and treehole capacity (microhabitat size). Therefore, microhabitat-size distribution is potentially a significant constraint of local community structure, and its variation may contribute to the variation in local and regional species richness.     

Species richness and altitudinal variation in the aquatic metazoan community in bamboo phytotelmata from north Sulawesi

We compared the aquatic metazoan community structure in bamboo stumps between a lowland (Kosinggolan; 200 m a.s.l.) and a highland site (Moat; 1030–1050 m a.s.l.) in North Sulawesi. The lowland bamboo stumps harbored 38 taxa including 2 predators, and the highland stumps harbored 35 taxa including 2 predators. In total 45 taxa were recorded, including 3 predators. Dominant detritivores were Tipulidae, Scirtidae, Chironomidae, Culicidae and Ceratopogonidae. The sole dominant predators wereToxorhynchites mosquito larvae, which occurred in 67% and 28% of stumps at the lowland and the highland sites, respectively. Although the mean biomass per stump did not differ significantly between the sites, the mean number of species per stump was significantly smaller at the lowland site. In addition, the variation in species composition among stumps was greater at the lowland site than at the highland site. Among dominant taxonomic groups, the number of non-predatory culicid species per stump was smaller at the lowland site where their predator,Toxorhynchites, was more abundant, although both sites had the same number of culicid species. In the presence ofToxorhynchites, the density and biomass of other culicids per stump were reduced significantly. The difference in predator density might affect differences in the local-scale community structure of individual bamboo stumps.     

Local and Regional-Scale Food Web Structure in Nepenthes alata Pitchers1

Tropical Nepenthes pitcher plants provide small, isolated aquatic habitats. We examined inter-pitcher variation in the community structure of the inhabitants of Nepenthes alata Blanco in West Sumatra, focusing on the conditions of the pitchers, bacterial density in the pitcher fluid, density and biomass of metazoan inhabitants, and the frequencies of interspecific encounters. Older pitchers contained more insect carcasses. The bacterial density increased with the age of the pitchers, but decreased in withered pitchers that contained finely decomposed detritus. In live pitchers, the bacterial density, the density, mass and species richness of metazoa, and the number of trophic levels per pitcher were positively correlated with detrital mass, which was correlated with volume of pitcher fluid. The metazoan fauna from N. alata consisted of 4 predators and 12 saprophages, among the richest known for Nepenthes species. However, each individual pitcher harbored a limited numbers of species, owing to (1) the low incidence of many species, and (2) the aggregated distribution and different temporal colonization pattern of major species. Six dipteran taxa (one predator and five saprophages) accounted for the bulk of metazoan inhabitant biomass. Of 48 combinations of predator-prey encountered, only four occurred frequently (in > 30% of pitchers), which included two predators and three saprophages. Thus, individual pitchers harbored relatively simple communities despite the regional species richness, and only limited kinds of predator-prey encounters seemed to occur frequently in the regional food web. The local-scale properties of the subdivided communities presented here provide the basic information for understanding the maintenance of regional species richness and food web complexity.     

Habitat stability and the larval mosquito community in treeholes and other containers on a temperate Island

The temporal fluctuation of water levels and the presence of mosquito larvae were investigated for four types of small container habitats (treeholes, bamboo stumps, cemetery stone vases, and cemetery stone vessels) on Kabeshima Island in Kyushu, southwestern Japan. The probability that containers held water was positively correlated with the quantity of the preceding rainfall and with the depth and volume of the containers. It was estimated that dehydration occurred more regularly in autumn and winter than in summer. The probability that mosquito larvae were present in each type of container was positively correlated with habitat stability in terms of the probability of the existence of standing water and the coefficient of variation of the water level. Twelve species of mosquito larvae, including two rare predators, were found. Species composition differed between the different types of container. Although 4 to 10 species used each type of container, the median number of species per container was two for treeholes and bamboo stumps, and one for the others. The dominant species wasTripteroides bambusa in treeholes and bamboo stumps,Aedes albopictus in stone vases, andA. japonicus in stone vessels. The larval mosquito community, which lacked major predators, possessed the following features that may facilitate the coexistence of many species: (1) niche segregation amongst species in terms of their selection of container types; (2) an aggregated distribution of the individual species among containers of the same type; (3) high intraspecific mean crowding (and hence probably intense intraspecific competition) in the dominant species in each type of container; (4) independent species associations within the same type of container; and (5) low interspecific mean crowding (and hence probablynot intense interspecific competition) between species in the same type of container.     

Insect species interactions and resource effects in treeholes: are helodid beetles bottom-up facilitators of midge populations?

The insect community living in central Pennsylvania treeholes in autumn consists primarily of larvae of two species of helodid beetles, Prionocyphon discoideus and Helodes pulchella, and larvae of one species of ceratopogonid midge,Culicoides guttipennis. We manipulated treehole volume and the densities of these insects in laboratory microcosms. We hypothesized that: (1) helodid beetle larvae, which are shredders, would enhance growth and survival of ceratopogonid midge larvae (deposit feeders) in a processing chain commensalism, and (2) the quantity of resources expressed as water volume plus leaf litter would affect helodids and protozoans directly. Intraspecific competition was not found in midges, nor was interspecific competition between the two helodid species. Protozoan population densities decreased or grew slower in the presence of insects and in smaller microcosms. Development time and adult wing length of the midge (C. guttipennis) were affected by both total microcosm volume and insect species combination. Under resource limitation, midges grew larger in the presence of helodids, and in general, midges were larger in treatments with higher ratios of helodids to midges. Water chemistry in the microcosms was affected both temporally and by insect presence. Hydrogen ion levels decreased over time, and microcosms with no insects had lower hydrogen ion levels. Specific conductance increased in all treatments over time, and microcosms with no insects had lower conductivity than most treatments. Helodid larvae have a positive effect on midges, possibly due to a processing chain facilitation. If helodids are keystone decomposers in this system, their presence could affect resource availability and affect other organisms in the community. Similar processing chain commensalisms occur in other phytotelmata. These types of interactions may therefore be important in the structure and function of detritus-based communities. Received: 31 January 1996 /Accepted: 7 August 1996     

Diversity and endemism of ciliates inhabiting Neotropical phytotelmata

While the diversity and distribution of macro-organisms living in phytotelmata (plant-container habitats) is well known, detailed taxonomic work on micro-organisms living in the same environments is limited. As a model clade of microbial eukaryotes, sampling of ciliates in Neotropical bromeliad tanks increased, and Neotropical phytotelmata such as bamboo stumps and tree holes were newly sampled. Thirty-three isolates from Brazil, Costa Rica, Dominican Republic, Jamaica and Mexico were sequenced for small subunit rDNA, and placed into a phylogenetic context using non-phytotelmata GenBank accessions. This and the morphological investigations discovered 45 undescribed, possibly endemic ciliate species. The potential endemics are from throughout most clades of the ciliate tree of life, and there is evidence of speciation within the Neotropical phytotelmata habitat. Our data show the number of potential Neotropical phytotelmata-endemic ciliate species increasing as more phytotelmata are sampled. While the new data show that the supposed endemics are mainly recruited from moss and ephemeral limnetic habitats, the bromeliad ciliate fauna is quite distinct from those of other limnetic habitats, lacking many typical and common freshwater genera, such as Coleps, Colpidium, Frontonia, Paramecium, Glaucoma, Nassula, Stylonychia and Trithigmostoma. There is no indication that specific ciliates are confined to specific bromeliads.     

Distributions of larval mosquitoes among bamboo-stump pools which vary in persistence and resource input

We studied the seasonal occurrence and the distribution patterns of larval mosquitoes in a bamboo grove in northern Kyushu, Japan. The number of pools was large from June to August and was small in winter. Deep stumps and semi-closed-type stumps held water more persistently than shallow and open-type stumps, respectively. Open-type stumps trapped more leaves than semi-closed-type stumps and the number of leaves trapped in the open-type stump was positively correlated with the area of the pool. The incidences ofTripteroides bambusa andAedes albopictus were low early in their breeding season and gradually increased thereafter. In August, the density ofT. bambusa larvae per pool was higher in the old (>2 months) pools than in the new pools and was positively correlated with the depth of the stumps. In contrast, the density ofA. albopictus did not differ significantly between the new-and old pools and was not significantly correlated with the depth of the stump. The density ofA. albopictus was positively correlated with the number of leaves that had been trapped in the stump, whereas the density ofT. bambusa was not. In addition to the seasonal fluctuation in habitat-patch availability, the variations in habitat persistence and resource input among bamboo stumps may facilitate the coexistence of the two mosquitoes that were differentially limited by these factors.     

How effective are non-destructive sampling methods to assess aquatic invertebrate diversity in bromeliads?

With the growing interest in small aquatic water bodies, especially as naturally replicated model systems for ecological research, aquatic invertebrate communities in phytotelmata are increasingly receiving attention these days. The recognition of the substantial contribution to the regional species pool of specialised species draws further attention to these small and often temporary habitats. The methods currently used for studying communities in some types of phytotelma, such as bromeliads, tend to be destructive, typically involving complete dissection of the plant. The expected increase in sampling intensity associated with the increasing interest in phytotelmata may result in a negative impact on plant populations in some areas, decreasing numbers in an unsustainable way, especially in locations with ongoing, intensive research. We therefore aimed to investigate whether less-destructive sampling methods can achieve sufficient data quality to allow their use as alternatives to complete plant dissection. We tested the effectiveness of three such methods in measuring the aquatic invertebrate communities in tank bromeliads (Tillandsia guatemalensis) in Cusuco National Park, Honduras. The three methods were pipetting the water out of the bromeliad, turning the bromeliad upside down and dissecting only the outer part of the plant (the oldest, often deteriorating leaves). Overall, we found that these methods were poor predictors of richness and abundance of the organisms in communities. However, we found big differences between taxonomic groups, depending in part on the ecology of the organisms, and we suggest that some less-destructive alternative methods may be appropriate for studying some specific groups (e.g. Culicidae). Based on these results and a rapid survey of the abundance of bromeliads in the national park, we question whether intensive, ongoing research into aquatic invertebrate communities in similar phytotelma populations is sustainable. From the point of view of conservation, alternative model systems need to be found.     

Specialized breeding in plants affects diversification trajectories in Neotropical frogs

Many animals breed exclusively in plants that accumulate rainwater (phytotelma; e.g., bromeliad, bamboo, fruit husk, and tree hole), to which they are either physiologically or behaviorally specialized for this microhabitat. Of the numerous life-history modes observed in frogs, few are as striking or potentially consequential as the transition from pond- or stream-breeding to the deposition of eggs or larvae in phytotelmata. Such specialization can increase offspring survivorship due to reduced competition and predation, representing potential ecological opportunity for adaptive radiation, yet few lineages of phytotelma-breeding frogs appear to have diversified extensively after such a transition, at least in the New World. We use a phylogeny of Neotropical frogs and data on breeding microhabitat to understand the evolutionary transitions involved with specialized phytotelma-breeding. First, we find that phytotelma-breeding is present in at least 168 species in 10 families of frogs. Across the phylogeny, we estimate 14 origins of phytotelma-breeding and 115 reversals, showing that phytotelma-breeding is a highly labile character. Second, phytotelma-breeding lineages overall have higher net diversification than nonphytotelma-breeding ones. This specialization represents an ecological opportunity resulting in increased diversification in most families with phytotelma-breeding lineages, whereas phytotelma-breeding toads have restricted diversification histories.     

Larval Planktotrophy—A Primitive Trait in the Bilateria?

The concept of Gösta Jägersten of a primary biphasic metazoan life-cycle, consisting of a planktotrophic larva and a benthic adult, forms the basis for several theories on metazoan phylogeny. In this paper the assumed planktotrophic life-style of the larva is critically analyzed and reconsidered. It is shown, in particular for the Mollusca, that a biphasic life-cycle with a lecithotrophic larva is probably the plesiomorphic condition. Character distribution and structural data suggest a parallel evolution of the downstream collecting system used in planktotrophic larvae or filter-feeding adults of gastropods, bivalves and other spiralian or aschelminth taxa. In the basic metazoans (Parazoa, Placozoa, coelenterates) direct or lecithotrophic development dominates by far. For the acoelomate (Platyhelminthes, Gnathostomulida) and pseudocoelomate taxa direct development is probably the plesiomorphic condition. The structural similarities of the upstream collecting system in tentaculate and deuterostome phyla may also be explained by parallel events of heterochrony out of an ancestor with adult filter-feeding. The main conclusion of this survey is that larval planktotrophy is likely to be secondary and not a plesiomorphic condition among the Bilateria. Accordingly, theories which are based on the assumed plesiomorphy of larval planktotrophy of the Bilateria, need careful reevaluation.     

Surplus Killing by Predatory Larvae of <Emphasis Type="Italic">Corethrella appendiculata</Emphasis>: Prepupal Timing and Site-Specific Attack on Mosquito Prey

Surplus or ‘wasteful’ killing of uneaten prey has been documented in the fourth larval instar of various species of the mosquito genus Toxorhynchites that occur in treeholes and other phytotelmata. Here we document surplus killing by the predatory midge Corethrella appendiculata, which in Florida cohabits treeholes and artificial containers with larvae of Toxorhynchites rutilus. Provided with a surfeit of larval mosquito prey, surplus killing was observed only in the fourth instar of C. appendiculata, peaking in intensity in the final 24 h prior to pupation, as observed for Toxorhynchites spp. Attack sites identified from videotaped encounters with mosquito prey were divided among head, thorax, abdomen, and siphon. Consumed mosquito larvae (n = 70) were attacked primarily on the head (46%) or siphon (34%), but surplus-killed prey (n = 30) were attacked predominantly on the thorax (83%). Despite its independent evolution among different insect species in aquatic container habitats, the functional significance of prepupal surplus killing remains unclear.     

Mosquito community structure in phytotelmata from a South American temperate wetland

Phytotelmata, or plant-held waters, are considered to be good model systems for the study of community ecology. The fauna of these natural container habitats, particularly the mosquitoes, have been extensively investigated in tropical regions, but there is little known about them in temperate South America. We assessed the structure of immature mosquito communities in leaf axils, tree holes, and bamboo stumps from a temperate wetland of Argentina. A total of 4,330 immature mosquitoes were collected among the 2,606 phytotelmata inspected. Leaf axils of eight plant species and tree holes were larval habitats for nine mosquito species belonging to the genus Culex, Wyeomyia, Isostomyia, and Toxorhynchites. The mosquito communities showed richness ranging from one to four species. Marked differences were detected in the plant specificity for the species collected. Some of them were exclusively found in one plant species (Isostomyia paranensis in Scirpus giganteus), whereas others were collected in up to five plant species but belonging to the same phytotelm class, the leaf axils. Those from tree holes are well-known dwellers of artificial containers and ground water habitats, such as Culex pipiens. Our results support the idea of low mosquito richness in phytotelmata from temperate regions in comparison with tropical areas, but the observed specificity patterns echo the findings of tropical forests.     

Distribution and turnover of a mosquito (Tripteroides bambusa) metapopulation among bamboo groves

We surveyed the distribution of a mosquito, Tripteroides bambusa (Yamada), among patchily distributed bamboo groves from 1994 to 1997 in an area of 4 km × 4 km in Saga, south-western Japan. In the study area, this mosquito uses mainly water-filled bamboo stumps as its larval habitat. In 1994, a year with little rainfall in the summer, T. bambusa larvae were found in 30 of the 60 groves that contained water-filled bamboo stumps. By 1997, the number of occupied groves increased to 64, and the number of groves with water-filled stumps increased to 109. Tripteroides bambusa was found frequently in the area covered by an orange orchard where bamboo groves were dense, and rarely in the open land where bamboo groves were sparse. Colonization of T. bambusa occurred in groves in the orchard and the open land which were less than 0.57 km away from the nearest occupied grove. Large groves were more likely to be occupied, and extinction occurred only in small groves ( 0.104 ha). Groves without water-filled stumps in 1994 were less likely to be occupied in the following period than those with water-filled stumps in 1994. These findings suggest that the T. bambusa metapopulation will not extend its distribution into all of the bamboo groves in the study area, but will not become extinct because of some highly persistent populations.     

Carbon Accumulation and Carbon Forms in Tissues During the Growth of Young Bamboo (<Emphasis Type="Italic">Phyllostachy pubescens</Emphasis>)

Moso bamboo (Phyllostachys pubescens) is an important non-timber forest product (NTFP) in the forest ecological system of subtropical China. In this study of young bamboo, dynamic changes in height, biomass, and carbon accumulation were determined and tissue samples were analyzed by ¹³C-nuclear magnetic resonance (NMR) technology. Results showed that the time from the bamboo shoots sprouting to the formation of young bamboo was 35–40 d. Accumulation of biomass and carbon in young bamboos depended mainly on ground diameter and the length of time after the bamboo shoots sprouted. NMR spectroscopy of tissue samples showed that O-alkyl carbon was found to dominate the tissue carbon, and it accounted for approximately 70%. The relative ratios of different carbon forms did not significantly change with the growth of young bamboo, suggesting that different carbon forms were stable with the carbon accumulation in the growth period of young bamboo.     

Are Bogs Reservoirs for Emerging Disease Vectors? Evaluation of Culicoides Populations in the Hautes Fagnes Nature Reserve (Belgium)

Several species of Culicoides (Diptera: Ceratopogonidae) biting midges serve as biological vectors for the bluetongue virus (BTV) and the recently described Schmallenberg virus (SBV) in northern Europe. Since their recent emergence in this part of the continent, these diseases have caused considerable economic losses to the sheep and cattle industries. Much data is now available that describe the distribution, population dynamics, and feeding habits of these insects. However, little is known regarding the presence of Culicoides in unusual habitats such as peaty marshes, nor their potential vector capacity. This study evaluated Culicoides biting midges present in the bogs of a Belgian nature reserve compared to those residing at a nearby cattle farm. Culicoides were trapped in 2011 at four different sites (broadleaved and coniferous forested areas, open environments, and at a scientific station) located in the Hautes Fagnes Nature Reserve (Belgium). An additional light trap was operated on a nearby cattle farm. Very high numbers of biting midges were captured in the marshy area and most of them (70 to 95%) were Culicoides impunctatus, a potential vector of BTV and other pathogens. In addition, fewer numbers of C. obsoletus/C. scoticus species, C. chiopterus, and C. dewulfi were observed in the bogs compared to the farm. The wet environment and oligotrophic nature of the soil were probably responsible for these changes in the respective populations. A total of 297,808 Culicoides midges belonging to 27 species were identified during this study and 3 of these species (C. sphagnumensis, C. clintoni and C. comosioculatus) were described in Belgium for the first time.     

Searching clusters of community composition along multiple spatial scales: a case study on aquatic invertebrate communities in bamboo stumps in West Timor

We examined spatial heterogeneity at multiple scales in composition of the aquatic invertebrate communities in bamboo stumps in a mountainous area of West Timor. We partitioned the study area (ca. 15,000 m²) at five levels of patchiness: two sites, four sub-sites, eight super-clumps, 14 clumps, and 84 stumps. Similarity of community composition between stumps varied more than expected from independent occurrence of each taxon in comparisons within any levels of patches. Negative association was frequently detected among taxa. These results indicate heterogeneity in community composition at a stump level. At higher levels, similarity among stumps within each site was greater than expected from null models which assumed no spatial heterogeneity, and similarities among super-clumps, sub-sites and between sites in a whole area were lower than expected from the null models. The observed patterns in similarities among subsets of the community and distribution of each taxon were mostly consistent with the models which assumed site-level heterogeneity. Therefore, we conclude that the community in this area was spatially heterogeneous at stump and site levels. The relationship between mean intra- and inter-specific crowding suggested that the site level habitat heterogeneity might reduce the chance of encounters between two predators, the larvae of the Toxorhynchites mosquito and the Brachyceran fly.     

Attraction and Repellent Behaviors of Culicoides Biting Midges toward Cow Dung,Carbon Dioxide,and Essential Oils

Culicoides biting midges (Diptera: Ceratopogonidae) are hematophagous arthropod vectors that transmit epizootic arthropod-borne viruses (arboviruses). Arboviruses are recognized as causes of pregnancy loss, encephalomyelitis, and congenital malformations in ruminants. Therefore, continuous monitoring and control of Culicoides, which causes significant damage to industrial animals are necessary. We performed attraction and repellent tests in Culicoides using various essential oils, cow dung, and carbon dioxide (CO₂). Culicoides tended to move more to cow dung (60.8%, P<0.0001) and CO₂ (63.8%, P<0.01). To the essential oils as repellents, 26.1% (P<0.0001), 18.7% (P<0.001), and 25.5% (P<0.01) of the Culicoides moved to the lavender, lemongrass, and eucalyptus chamber, respectively. The Culicoides that moved to the 3 essential oils chambers showed markedly low activity. Collectively, it was showed that Culicoides tended to be attractive to cow dung and CO₂, and repellent from the 3 essential oils.     

Bamboo stumps as mosquito larval habitats in Darjeeling Himalayas, India: A spatial scale analysis

Bamboo stumps can be a congenial breeding habitat of the mosquitoes. In view of this, a preliminary assessment of the dipteran immatures inhabiting the stumps of bamboo groves in the Darjeeling Himalayas was carried out at a spatial scale. Of the 104 stumps of Dendrocalamus hamiltoni surveyed, 70 were found to host immatures of three dipteran species, the mosquitoes Aedes aegypti and Culex quinquefasciatus and the midges Chironomus sp. in varying densities. Though the stumps varied in diameter, in each stump on average 12. 1 immatures were found. The abundance of the immatures was positively correlated with the diameter of the stumps (r=+0.382; P < 0.001) but negatively with the pH of the water present in the stumps (r=–0.336; P < 0.01). The coefficient of association was found to be +8.4 for the Ae. aegypti and Chironomus immatures, while in the rest of the species pair the association seemed to be independent. Thus it can be concluded that the stumps in the bamboo groves of Darjeeling Himalayas provides a favourable habitat for the mosquito and chironomid immatures.     

The systematics of clarkia bottae,C. Cylindrica,and a related new species,C. Rostrata

Populations ofClarkia cylindrica andC. bottae were studied in the field and in the garden. Seed from which the garden progenies were grown was collected in the wild. Experimental crosses were made between and within taxa. Fertility and chromosome pairing were observed in the hybrids. A maternal influence on seed set was found in crosses between C.cylindrica andC. bottae. Two taxa are described as new:Clarkia rostrata andC. cylindrica ssp.clavicarpa.     

Contribution to the phytogeography of kashmir himalaya I.Ranunculaceae andPaeoniaceae

The affinities and endemism of Kashmir HimalayaRanunculaceae andPaeoniceae reveal some interesting distribution patterns in some taxa. Isoflor maps, revealing the affinities ofAconitum, Aquilegia, Delphinium andRanunculus, are given. A high degree of endemism exists in the study area. About 41% of the total taxa show restricted distribution which is discussed. The floristic relationships of the wides show close links with Central Asia than any other phytogeographical unit. The significance of altitudinal amplitude of some taxa vis-a-vis their distribution pattern is discussed.