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1

Does topography of rocky intertidal habitat affect aggregation of cerithiid gastropods and co-occurring macroinvertebrates?

Jethva Soniya, Liversage Kiran, Kundu Rahul

Oceanologia

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2022

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No. 64 (2)

387--395

EN

Species aggregation has important implications for population survivorship and ecological functioning in many habitats, including rocky intertidal shores, which have been valuable to research for understanding ecological patterns and process. Intertidal gastropods of the family Cerithiidae often form extensive aggregations for which the driving mechanism may be positive thigmotaxis, i.e. movement occurring until an obstructing surface is contacted, then cessation of movement. However, it is unknown if thigmotaxis may occur by cerithiids contacting and aggregating around uneven surfaces of the rock topography, or by contacting other conspecific individuals. We quantified aggregation patterns in invertebrate assemblages and topographic complexity at intertidal rock platforms in NW India with extensive cerithiid populations. The cerithiids Clypeomorus moniliferus and Cerithium caeruleum were the most common species. Distribution analysis confirmed significant over-dispersion indicative of aggregation (densities were often around zero but occasionally reached up to 680 dm−2). Multivariate correlation analyses showed that topographic complexity contributes to overall species assemblage variability, but there was no evidence that topographic complexity correlates with cerithiid abundances or was likely to affect their aggregation. Thus the thigmotaxis producing cerithiid aggregation is probably associated with individuals contacting each other rather than any feature of the rock surface such as crevices or raised areas. Overall, while some components of species assemblages were associated with complex topography, regarding the abundant cerithiids, potential population benefits from aggregation (e.g. reduced desiccation and temperature) may be expected on rocky shores with any level of topographic complexity.

2

Influence of habitat structure and conditions in floodplain forests on mollusc assemblages

Kappes H., Kopeć D., Sulikowska-Drozd A.

Polish Journal of Ecology

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2014

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Vol. 62, nr 4

739--750

EN

Alder floodplain forests are a rare and threatened forest type in Europe. These forests can be very rich in mollusc species. The intermediate disturbance hypothesis predicts that species richness should peak at intermediate inundation frequency, that is, at intermediate elevation above the river level. We additionally hypothesized that constantly high soil moisture can distort the usually positive correlation between the amounts of downed deadwood and snail richness, and that tree stems might be more favourable than deadwood because their vertical structure provides a better refuge during inundation events. To this end, we sampled molluscs from a core area of 20 × 20 m from eight alluvial forests with black alder in the surroundings of Łódź, Central Poland. In each core area, substrate was collected from eight random plots (0.25 m2 each). We also recorded soil pH, vascular plant species and mosses diversity, along with other structural variables. Plant indicator values were calculated according to Ellenberg. Soil quality (amongst others: soil pH, reactivity value, nutrient and moisture availability) decreased with increasing elevation above the river level. In the plot samples, we found a total of 18,497 individuals from 52 species. Mollusc species richness dropped stronger than densities with an increasing elevation above the river level. Main influences on mollusc richness and abundance originated from positive correlations with soil pH and moisture. An additional hand sampling campaign on tree stems and deadwood items in the core area revealed that coarse woody debris items on average carried twice as many individuals as did tree stems. Deadwood and tree stems supported similar numbers of snail species per item, but beta-diversity was higher on deadwood. Consequently, Jackknife 2 predicted that deadwood is utilized by about 46 species, whereas tree stems only support about 39 species. Our results indicate (1) that mollusc richness peaks at low elevations above normal water level in this type of forest, (2) that intact hydrological regimes are associated with high soil quality and mollusc biodiversity, and (3) suggest that coarse woody debris adds resources, refuges and a dispersal agent for the alder forest floor fauna.

3

Determinants of plant species richness in different wetland types along a hydrological gradient: implication for conservation

Shi J., Ma K., Wang J., Zhang Y., Zhao J.

Polish Journal of Ecology

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2013

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Vol. 61, nr 4

645--654

EN

The loss of biodiversity caused by wetland degradation is a hot issue in ecology. It is known that hydrological degradation is the primary reason resulting in wetland degradation, but little is known about the relationship between plant species richness and environmental factors in different wetland types along a hydrological gradient. According to the gradient from high to low water level, wetland remnants in the Sanjiang Plain of northeast China were classified into three wetland types, which were permanently inundated marshes (PIM), seasonally inundated marshes (SIM) and wet meadows (WM) respectively. In this paper, we aimed to identify the determinants of plant species richness in the three wetland types and discern the transition of the determinants along a hydrological gradient. Plant species richness as well as area, habitat heterogeneity and resource availability was investigated in 51 wetland remnants, which were composed of 6 PIM, 25 SIM and 20 WM. Averagely, the area of wetland remnants occupied by PIM, SIM and WM was 0.35 ± 0.17 ha, 2.81 ± 2.88 ha and 1.34 ± 1.18 ha respectively. Aggregating the species in each wetland type, there were 67, 244 and 170 species recorded in PIM, SIM and WM. The determinants of species richness varied in different wetland types: standing water depth in PIM, area and water heterogeneity in SIM, and soil fertility and area in WM. With the decreasing water level, the influence of hydrological condition on species richness in the three wetland types declined while the impact of area and soil fertility gradually increased. Thus, hydrological condition was probably responsible for the transition of the determinants of species richness in different wetland types. Moreover, the habitat specialists of wetland would be lost when PIM or SIM degraded to WM. In order to conserve and restore plant diversity, specific measures should be taken including preventing area loss for all wetland remnants, managing the hydrological process for PIM and SIM, and regulating soil nutrient for WM.

4

Benefits of low-intensive grazing : co-occurrence of umbelliferous plant (Hladnikia pastinacifolia Rchb.) and opilionid species (Phalangium opilio. L) in dry, calcareous grassland

Sajna N., Kusar P., Slana Novak L. L., Novak T.

Polish Journal of Ecology

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2011

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Vol. 59, nr 4

777-786

EN

The impact of grazing has been discussed in many organisms, and it has been shown that it has considerable influence on the structural variation of vegetation, resulting in its tussocky appearance. Such spatial heterogeneity results in plants formations that facilitate other species by providing safe sites against predation and physical stress. On the Trnovski gozd plateau in western Slovenia, a secondary habitat of the rare, monotypic endemic umbelliferous species, Hladnikia pastinacifolia, was colonized by a relatively isolated population of the wide spread opilionid species, Phalangium opilio. We hypothesized that in this stony pasture, the impact of the structurally heterogenous vegetation that results from low-intensity grazing benefits both species on hot summer days. For this purpose, we classified vegetation formation types (VFT) and measured temperature and relative humidity in places settled by Ph. opilio individuals during their daily rest. According to the predominant species, we recognized six VFTs: Carlina acaulis, Ruta divaricata, Koeleria pyramidata, Juniperus communis, understory vegetation and grazed turf. Only the spiny C. acaulis and unpalatable R. divaricata facilitated H. pastinacifolia, while also acting as nurse plants. On the other hand, Ph. opilio preferred the understory, but also settled on the other VFts, except Ruta. During the highest daily temperature of about 38[degrees]C, Ph. opilio avoided the grazed turf. Temperature preferences refer to frequencies of individuals rather than to absolute temperature values. The frequencies were independent of sex and the VFTs. Females were more frequently found in tussocks showing higher temperature profiles (Juniperus, Koeleria). During the hot daytime, Ph. opilio was most sensitive to relative humidity, and less so to temperature, whilst the height of settlement varied in adjusting these two environmental factors. The distribution of males significantly differed between the subsequent morning, midday and evening series, but not between the morning and evening ones, while in females it differed between all the three time series. In habitats, such as stony dry pastures, low grazing intensity can maintain persistent populations of H. pastinacifolia and Ph. opilio even in extremely hot weather. Such grazing is the most convenient measure for protecting both species, especially the highly endangered Hladnikia. The major threat to such habitats is afforestation by Pinus nigra, which deserves additional management. We found that in stony pastures, low grazing intensity assures the structural heterogeneity of vegetation required to maintain persistent populations, of both H. pastinacifolia and Ph. opilio.

5

Does charophyte meadow induce the spatial heterogeneity of water abiotic properties of a tachymictic Lake?

Pełechaty M.

Ekologia i Technika

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2007

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R. 15, nr 1

24-29

EN

The study objective was to find out whether extensively developed charophyte meadow (built by Chora tomentosa) induce the spatial heterogeneity of basie physical-chemical water properties of a large, clearwater and tachymictic Lake and, so, with a long period of water overturn (Lake Lednica, Wielkopolska Region, mid-Western Poland) . Current trophic state might be assumed as moderately eutrophic with impressive water clariry. Submersed vegetation is well developed and predominated by charophytes forming dense beds. In the period of intense development of vegetation (between 17th May and 6th July 2004) physical-chemical analyses (water temperature, pH, oxygen concentration, conductMty, total dissolved substances) were performed five times at five sampling sites. Three of them were macrophyte-free open water regions (with varied contribution of charophytes in the phytolit-toral zone) and two further were shallow littoral sites: one close to a bathing place with sparse Tolypella glomerata specimens and the other in dense Chora tomentosa bed. The results showed lower conductivity and TDS values, and higher pH and the concentration of oxygen inside charophyte meadow as compared to the rest of sampling sites. By contrast, at the other littoral site but without plant cover conductivity and TDS revealed the highest values. Results are discussed in the light of habitat forming power of charophytes contrasted with long water overturned the Lake is subject to.

6

Population dynamics and demography of deermice (Peromyscus maniculatus) in heterogeneous habitat : role of coarse woody debris

Lee S. D.

Polish Journal of Ecology

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2004

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Vol. 52, nr 1

55-62

EN

I tested the hypothesis that habitat heterogeneity increases with increasing amounts of coarse woody debris (CWD) by comparing Peromyscus maniculatus populations in sites with high and low amounts of CWD. Sherman live-trapping technique was applied to monitor population fluctuation and to measure demographic parameters. In sites with high amount of CWD density was higher, populations fluctuated less, survivorship was better and residency time was longer. These results were in accordance with predictions of habitat heterogeneity and CWD played an important role for demography of P. maniculatus in managed coniferous forests.