Determining Species Richness Research Articles

Presence and abundance of macrophytes in Lake Slivniško jezero

Macrophytes are an important part of the lake biota. They are also bioindicators of environmental conditions. The goal of the present research was to determine species richness and abundance as well as longitudinal and depth distribution of macrophytes in Lake Slivniško jezero. A survey of macrophytes in the whole lake littoral was made, the minimum and maximum depth of taxa were measured and their abundance was estimated as well. We also assessed selected environmental parameters of the littoral and catchment. 22 macrophyte taxa: 9 emergent, 9 submerged and 4 natant macrophytes were determined. The most frequent species were Phragmites australis, Najas marina, Myriophyllum spicatum and Potamogeton nodosus. The maximum depth of colonisation was achieved by Nymphaea alba (to 2.4 m), while M. spicatum and N. marina grown to the depth of 1.9 m. According to CCA the distribution of macrophytes was significantly influenced by exposition, bottom slope, sediment type, slope of riparian zone, macroalgae abundance, type of riparian vegetation, completeness of riparian zone, land-use beyond the riparian zone and water turbidity.

Cyanobacteria Diversity In Kamanos Raised Bog (North-West Lithuania)

Abstract The current study summarised the diversity of cyanobacteria found in various habitats of the second largest raised bog of Lithuania. A total of 56 cyanobacteria species that comprise 19% of all phycoflora diversity in Kamanos raised bog were recorded. Species from the Chroococcales (32 species) order and the Chroococcus (7), Aphanothece (7) genera were the most numerous. Twenty one cyanobacteria species were found in Lithuania for the first time. Most of species recorded in Kamanos raised bog were cosmopolite or distributed in temperate zone. One third of the species were characteristic particularly of the peat bogs. Thirty nine species of cyanobacteria were specific to the particular water body and occurred only in 1–3 of the studied localities. Only five species, i.e. Chroococcus turgidus, Aphanocapsa grevillei, Aphanothece elabens, Cyanosarcina sp. and Hapalosiphon sp. were common. Peculiarities of the habitat were the most important drivers determining species richness and composition of cyanobacteria in a particular locality.

A review of contemporary patterns of endemism for shallow water reef fauna in the Red Sea

AbstractAimThe Red Sea is characterised by a unique fauna and historical periods of desiccation, hypersalinity and intermittent isolation. The origin and contemporary composition of reef‐associated taxa in this region can illuminate biogeographical principles about vicariance and the establishment (or local extirpation) of existing species. Here we aim to: (1) outline the distribution of shallow water fauna between the Red Sea and adjacent regions, (2) explore mechanisms for maintaining these distributions and (3) propose hypotheses to test these mechanisms.LocationRed Sea, Gulf of Aden, Arabian Sea, Arabian Gulf and Indian Ocean.MethodsUpdated checklists for scleractinian corals, fishes and non‐coral invertebrates were used to determine species richness in the Red Sea and the rest of the Arabian Peninsula and assess levels of endemism. Fine‐scale diversity and abundance of reef fishes within the Red Sea were explored using ecological survey data.ResultsWithin the Red Sea, we recorded 346 zooxanthellate and azooxanthellate scleractinian coral species of which 19 are endemic (5.5%). Currently 635 species of polychaetes, 211 echinoderms and 79 ascidians have been documented, with endemism rates of 12.6%, 8.1% and 16.5% respectively. A preliminary compilation of 231 species of crustaceans and 137 species of molluscs include 10.0% and 6.6% endemism respectively. We documented 1071 shallow fish species, with 12.9% endemic in the entire Red Sea and 14.1% endemic in the Red Sea and Gulf of Aden. Based on ecological survey data of endemic fishes, there were no major changes in species richness or abundance across 1100 km of Saudi Arabian coastline.Main conclusionsThe Red Sea biota appears resilient to major environmental fluctuations and is characterized by high rates of endemism with variable degrees of incursion into the Gulf of Aden. The nearby Omani and Arabian Gulfs also have variable environments and high levels of endemism, but these are not consistently distinct across taxa. The presence of physical barriers does not appear to explain species distributions, which are more likely determined by ecological plasticity and genetic diversity.

Calling for a new strategy to measure environmental (habitat) diversity in Island Biogeography: a case study of Mediterranean tenebrionids (Coleoptera: Tenebrionidae)

Many recent researches in island biogeography attempted to disentangle the effects of area <em>per se</em> and “habitat diversity” on species richness. However, the expression “habitat diversity” in this context should be avoided, because habitats can be only recognized by referring to the resources needed by a particular species. What is really measured in such researches is some form of “environmental heterogeneity”. Although habitat heterogeneity can be measured in various ways, most researches in island biogeography simply used the number of biotopes (typically classified as land cover categories). However, not all biotopes have the same surface. On the basis of the area occupied by each land cover category, it is possible to calculate indices of environmental diversity, evenness and dominance, as commonly done in community ecology research. These indices can be used to investigate the role of environmental diversity in determining species richness. We used the tenebrionid beetles inhabiting twenty-five small islands around Sicily (Central Mediterranean) to illustrate these concepts. We found that both area per se and environmental heterogeneity contributed to determine species richness. Moreover, we found that the relationship between species richness and environmental homogeneity followed a power function model. This indicates that environmental homogenization may determine a rapid, non linear decline in species richness.

The impacts of climate change on Antarctic nearshore mega-epifaunal benthic assemblages in a glacial fjord on King George Island: Responses and implications

We examined the impacts of climate change on Antarctic nearshore marine benthic communities on the West Antarctic Peninsula, one of the most rapidly warming regions on earth. We surveyed the epibenthic megafaunal assemblages of Marian Cove, a representative fjord on King George Island. We collected specimens by SCUBA diving at varying distances from the retreating glacier front during the 2013/2014 austral summer. Based on presence/absence data from the collected taxa, we determined species richness (S), taxonomic distinctness (TD) and functional diversity (FD) and further analyzed differences in assemblages in relation to environmental characteristics. Faunal assemblages in the inner cove (ice-proximal zone) were compositionally distinct from those in the outer cove. Species number and FD were also lower in the inner cove and tended to increase toward the outer cove. Nonetheless, TD values were similar among sites, indicating that all sites were distinct taxonomically. This may be because glacier retreat affected organisms of lower taxonomic levels the most. Multivariate and univariate analyses demonstrated that these differences were significantly related to distance from the glacier, substrate grain size, and organic content. The high correlation (R=0.909, P<0.01) of assemblages with distance from the glacier front suggests that physical disturbance by ice is a major process shaping benthic communities. Thus, we provide evidence that glacier retreat and its consequent processes impact the structure and function of communities. With their spatial pattern significantly associated with environmental suites, nearshore megabenthic communities respond sensitively and measurably to climate-induced impacts, suggesting their utility as long-term biomonitors. As a small but confined glacial cove with very distinct environmental gradients related to climate-induced processes, Marian Cove could serve as a model ecosystem for assessing climate impacts on Antarctic nearshore benthic communities.

Simple mechanistic models can partially explain local but not range-wide co-occurrence of African mammals

Aim One hypothesis to explain strong biodiversity–climate correlations is that climate gradients determine individual species ranges, which then sum up to form species richness patterns. If this is true, then climate gradients should not only predict the local occurrence of species (i.e. patterns in the local community) but also co-occurrence of species across the entirety of their ranges (i.e. the regional community concept). We test this hypothesis for African mammals. Location Sub-Saharan Africa. Methods We quantified species richness of African mammals in 10,000-km2 quadrats to assess local community patterns and developed a new metric for range overlap in the assemblage dispersion field to quantify the range-wide overlap of species ranges. To identify potential underlying processes, we used a mechanistic modelling approach to simulate the effects of environmental determinism, dispersal limitation and range positioning on species co-occurrence patterns in both local and regional communities. Results Although mechanistic models that included climate gradients, dispersal limitation and range positioning could emulate local patterns of mammal richness accurately, they were poor predictors of the co-occurrence of species across their entire ranges. In the regional community, patterns of mammal co-occurrence were more closely linked to biogeographical regions in Africa. Conclusions We found little support for the hypothesis that climate modulates individual species ranges, which then sum up to determine species richness. Instead, climate may determine how many mammal species can persist locally, whereas historical processes and species interactions ultimately determine more general patterns of species co-occurrence.

Geographical patterns of butterfly species diversity in the subtropical Ryukyu Islands: the importance of a unidirectional filter between two source islands

AbstractAimTo examine the roles of geohistorical and ecological factors in the development of butterfly assemblages on continental islands with multiple source pools.LocationThe Ryukyu Islands, Japan. This arc of continental islands is located between two source islands, Kyushu and Taiwan, and contains two major straits, the Tokara and Kerama gaps.MethodsA total of 489 butterfly species were identified on 59 islands, including the two source islands. The influences on species richness and rarity of latitude, area, elevation, and distances from the nearest source and from the nearest larger island were analysed using generalized linear models. The relationships between differences in area, elevation, and distance and dissimilarity between island butterfly faunas were evaluated by multiple regressions on distance matrices. The relationships between area, elevation, and distance from the source and dissimilarity to the source fauna were examined using linear models. The dissimilarity was based on the Sørensen index and its nestedness and turnover components.ResultsLatitude, area and isolation determined species richness and rarity, whereas differences in elevation and distance regulated species turnover between islands. The gaps between islands were associated with nestedness between island faunas. Area consistently had a negative relationship with the total dissimilarity to source fauna. The overall dissimilarity to Kyushu decreased with the distance from Kyushu, whereas dissimilarity to Taiwan increased with distance from Taiwan.Main conclusionsBoth environmental filtering and dispersal limitation determine the geographical patterns of butterfly assemblages in the Ryukyus. The present study focuses on the unique pattern wherein migration from Kyushu is facilitated on islands farther from Kyushu, while migration from Taiwan is inhibited on islands farther from Taiwan. The two source islands have contrasting roles that affect butterfly distributions unidirectionally. This study highlights the importance of resolving dissimilarity into nestedness and turnover components to elucidate the formation of island biota.

NEPENTHES DIVERSITY AND ABUNDANCE IN FIVE HABITATS IN BRUNEI DARUSSALAM

LATIFF, N. A., SUKRI, R. S., &amp; METALI, F. Nepenthes diversity and abundance in five habitats in Brunei Darussalam. Reinwardtia 14(1): 67 – 71. -- The genus Nepenthes is known to be diverse in Bornean forests and has been recorded in Brunei Darussalam in various forest types. We aim to investigate variation in Nepenthes species richness and abundance at five forest types throughout Brunei Darussalam: open secondary, heath, peat swamp, white sand and mixed dipterocarp forests. A total of thirty-nine 5 x 5 m2 plots were set up in these forest types. Within each plot, Nepenthes species abundance was quantified, with Nepenthes voucher specimens collected and identified to determine species richness. No significant differences were detected either for Nepenthes species richness or abundance between the five forest types, despite records of Nepenthes in Brunei showing preferences for particular habitat types. We suggest that average species richness and abundance remained constant regardless of forest types in this study, but that these results would likely change if sampling intensity is increased in future studies.

Environmental heterogeneity predicts species richness of freshwater mollusks in sub-Saharan Africa

Species diversity and how it is structured on a continental scale is influenced by stochastic, ecological, and evolutionary driving forces, but hypotheses on determining factors have been mainly examined for terrestrial and marine organisms. The extant diversity of African freshwater mollusks is in general well assessed to facilitate conservation strategies and because of the medical importance of several taxa as intermediate hosts for tropical parasites. This historical accumulation of knowledge has, however, not resulted in substantial macroecological studies on the spatial distribution of freshwater mollusks. Here, we use continental distribution data and a recently developed method of random and cohesive allocation of species distribution ranges to test the relative importance of various factors in shaping species richness of Bivalvia and Gastropoda. We show that the mid-domain effect, that is, a hump-shaped richness gradient in a geographically bounded system despite the absence of environmental gradients, plays a minor role in determining species richness of freshwater mollusks in sub-Saharan Africa. The western branch of the East African Rift System was included as dispersal barrier in richness models, but these simulation results did not fit observed diversity patterns significantly better than models where this effect was not included, which suggests that the rift has played a more complex role in generating diversity patterns. Present-day precipitation and temperature explain richness patterns better than Eemian climatic condition. Therefore, the availability of water and energy for primary productivity during the past does not influence current species richness patterns much, and observed diversity patterns appear to be in equilibrium with contemporary climate. The availability of surface waters was the best predictor of bivalve and gastropod richness. Our data indicate that habitat diversity causes the observed species–area relationship, and hence, that environmental heterogeneity is a principal driver of freshwater mollusk richness on a continental scale.

Disentangling the drivers of understorey species richness in eutrophic forest patches

AbstractQuestionsWhat are the driving factors for the species richness of understorey herbs of isolated forest patches? How can the relative direct and indirect effects of patch area, site quality, habitat isolation and continuity be disentangled? What are the effects on different species groups?LocationEutrophic hardwood forest patches in northwestern Germany. The isolation of these patches results from extensive agricultural land use and prevailing poor soil conditions in the surrounding landscape. Thus, the patches are embedded within a matrix of both open habitats and species‐poor acidic forests.MethodsWe surveyed 76 eutrophic forest patches and recorded all understorey herb species. Several measured site variables were divided into soil and structural components, and into variables describing mean site conditions and site heterogeneity. Partial least squares structural equation modelling (PLS‐SEM) was employed to determine the direct and indirect effects of patch area, site heterogeneity, mean site conditions, isolation and habitat continuity on species richness of several species groups.ResultsThe most important factor determining species richness was patch area, which showed the strongest direct effect on eutrophic forest specialist species. Richness of forest matrix species, which also occur in the surrounding forest areas, was not directly influenced by area. Soil heterogeneity as well as structural heterogeneity increased with area, but only soil heterogeneity was relevant for species richness. Soil heterogeneity was more important for forest species in general and stress tolerators than for generalist species, open habitat species, competitors and ruderals. Mean site conditions influenced species richness of generalists, open habitat species, competitors and nutrient‐demanding species. Isolation had a (negative) effect only on habitat specialists.ConclusionsThe relative effects of driving factors varied considerably between species groups. From our results for eutrophic forest specialists, we conclude that large and well‐connected habitat patches are especially important for the successful conservation of the unique and partly endangered flora of eutrophic hardwood forests.

Environment and biogeography drive aquatic plant and cladoceran species richness across Europe

Summary The relative role of environmental and regional processes in determining patterns of biodiversity may vary across spatial scales. In inland aquatic communities, macrophytes and zooplankton have the potential to disperse over large spatial scales (hundreds of kilometres), but the role of environmental and regional processes in determining species richness (SR) at different spatial scales is poorly understood. To assess the relative importance of environmental and regional processes acting on both regional (within‐region) and continental (among‐region) scales, we surveyed 139 waterbodies in five geographic regions (Spain, Italy, the Netherlands, Scotland and Norway) and in each region measured environmental variables, descriptors of connectivity and SR of two aquatic taxa, namely aquatic plants and cladocerans. Analyses using boosted regression trees and generalised linear models, integrated with multiple imputation of missing data, indicated that both environmental and regional processes were related to local SR. Total phosphorus was the main environmental correlate of SR, showing a unimodal relationship with both taxonomic groups. Conductivity and lake depth were also related to cladoceran SR, and Secchi depth was related to aquatic plant richness. The SR of aquatic plants and cladocerans were significantly correlated, but this relationship was mainly indirect (i.e. determined by the effect of common environmental variables). The limited role of connectivity and space (lack of spatial autocorrelation in model residuals) relative to environment suggests that dispersal limitation is not as important as the environment in explaining richness patterns for both groups within regions. However, region identity strongly influenced SR, which suggests an important effect of biogeographic factors (e.g. the level of endemicity; the number of unique species in each region) and/or dispersal limitation at the continental scale. We conclude that environmental factors and biogeographic processes largely determine the patterns of local and regional SR in aquatic plants and zooplankton.

Responses of alpine meadow seed bank and vegetation to nine consecutive years of soil fertilization

Decline in aboveground species diversity in response to nutrient enrichment has been demonstrated by many studies. However, information on the soil seed bank also is important for restoration of species-rich vegetation, but this subject has received little attention. The aim of this study was to investigate the relationship between the aboveground vegetation and the soil seed bank of an alpine meadow along a fertilization gradient that can germinate in spring. We determined species richness, density, life form and functional groups in the soil seed bank and in the aboveground vegetation along an N–P fertilization gradient from 0 to Fer120 (120g/m2; i.e. 25.4gN and 28.2Pm2/yr). Non-metric multidimensional scaling was used to test the similarity between soil seed bank and aboveground vegetation. Species richness of both soil seed bank and vegetation declined in response to 9 years of fertilization, but rate of decline in the seed bank was slower than that in the vegetation. Seed density did not differ along the fertilization gradient except for Fer30, which had the highest seed density. Plant density in the vegetation declined along the fertilization gradient. Proportion of annuals increased both in the vegetation and the soil seed bank along a fertilization gradient. Percentage of different functional groups in the soil seed bank changed but less than that in the vegetation. The similarity between soil seed bank and vegetation increased from Fer0 to Fer90 and then decreased in Fer120. Fertilization influenced species composition of the soil seed bank, but the effect was smaller than that on the aboveground vegetation. The seed bank present in spring provides high species richness and high seed densities for restoration, but restoration to the non-fertilized state would be difficult due to the shift to a higher proportion of annuals and to a low proportion of sedges along the fertilization gradient.

KELIMPAHAN CHRYSOPHYTA PADA MEDIA BUDIDAYA IKAN NILA YANG DIBERI PAKAN FERMENTASI DENGAN PENAMBAHAN TEPUNG KULIT UBI KAYU DAN PROBIOTIK

Chrysophyta is also known as golden-yellow algae because of the yellow dominant pigment of carotene and xanthophyll. This study aimed to determine species richness and abundance of Chrysophyta in the Tilapia culture media which was fed with the addition of cassava peel flour and probiotic. The method applied in this study was the experimental method with 4 treatments, i.e.: the use of fermented feed with the addition of cassava peel flour (0%, 25%, 50%, and 75%) and probiotic in Tilapia culture media. Each treatment was replicated 4 times. Sampling was carried out 6 times at intervals of 2 weeks. The observed parameters were the main parameters, i.e.: the number of Chrysophyta species and individuals; and supporting parameters, i.e.: water temperature, pH, TDS, TSS, NO3, NO2, BOD5, DO, and total of phosphate. Species richness and abundance of Chrysophyta data were analyzed using cluster analysis based on Bray-Curtis similarity coefficient. The analysis continued with Similarity Percentages (SIMPER) analysis to determine the contribution of species to the similarity index in each group or to dissimilarity index amongst groups. The results showed that the species richness found in the Tilapia media culture which was fed with the addition of cassava peel flour and probiotic consist of 20 species belonging to a class namely Bacillariophyceae. Abundance of Chrysophyta obtained was ranged from 5.160-13.292 individuals/liter. The cluster analysis showed that Chrysophyta amongst treatments have a quite high similarity level (&gt; 50%) was ranged between 65.56% -83.99%. Contributions of species which contribute the highest similarity index were Diatoma vulgare (49.80%), Navicula brachysira (70.50%) and Navicula platystoma (82%).

Terrain and vegetation structural influences on local avian species richness in two mixed-conifer forests

Using remotely-sensed metrics to identify regions containing high animal diversity and/or specific animal species or guilds can help prioritize forest management and conservation objectives across actively managed landscapes. We predicted avian species richness in two mixed conifer forests, Moscow Mountain and Slate Creek, containing different management contexts and located in north-central Idaho. We utilized general linear models and an AIC model selection approach to examine the relative importance of a wide range of remotely-sensed ecological variables, including LiDAR-derived metrics of vertical and horizontal structural heterogeneities of both vegetation and terrain, and Landsat-derived vegetation reflectance indices. We also examined the relative importance of these remotely sensed variables in predicting nesting guild distributions of ground/understory nesters, mid-upper canopy nesters, and cavity nesters. All top models were statistically significant, with adjusted R2s ranging from 0.05 to 0.42. Regardless of study area, the density of the understory was positively associated with total species richness and the ground/understory nesting guild. However, the relative importance of ecological predictors generally differed between the study areas and among the nesting guilds. For example, for mid-upper canopy nester richness, the best predictors at Moscow Mountain included height variability and canopy density whereas at Slate Creek they included slope, elevation, patch diversity and height variability. Topographic variables were not found to influence species richness at Moscow Mountain but were strong predictors of avian species richness at the higher elevation Slate Creek, where species richness decreased with increasing slope and elevation. A variance in responses between focal areas suggests that we expand such studies to determine the relative importance of different factors in determining species richness. It is also important to note that managers using predictive maps should realize that models from one region may not adequately represent communities in other areas.

How might sea level change affect arthropod biodiversity in anchialine caves: a comparison of Remipedia and Atyidae taxa (Arthropoda: Altocrustacea)

Sea level change influences biodiversity of endemic cave fauna to varying degrees. In anchialine systems, a marine layer flows under less saline layers, each with differing associated fauna. We assess the role of present and historic (last glacial maximum – 18,000 years ago) distance from the ocean in determining species richness and phylogenetic diversity patterns for two groups of anchialine crustaceans: the marine-restricted Remipedia and a subset of groundwater-inhabiting atyid shrimp with greater tolerance for salinity variation. We calculated species richness and phylogenetic diversity per cave based on records of remipede and atyid diversity at 137 locations in the Yucatan Peninsula, Caribbean, Australia, and the Canary Islands. After calculating the distance of each cave’s surface opening from the past and present shoreline, we evaluated how species richness and phylogenetic diversity change with distance from the present and historic ocean. Remipede species richness and phylogenetic diversity declined rapidly with distance from the ocean. Ninety-five percent of the remipedes surveyed were located within 7 km of the present ocean and 18 km of the historic ocean. Atyid species richness and phylogenetic diversity declined more slowly with distance from the ocean than that of remipedes. Atyid shrimp were also distributed over a broader range: 95 % were located within 100 km of the present ocean and 240 km of the historic ocean. Our findings indicate that coastal geomorphology and salinity tolerance influence a clade’s distribution with respect to its distance from the ocean. We also report a possible latent response to sea level change.

Using citizen science to estimate lichen diversity

Lack of field time, access to experts, and the challenges associated with research permits make traditional approaches for determining species richness (comprehensive collection and determination of biological specimens) impractical in many situations. To accelerate local biodiversity assessments for conservation and resource management, scientists need both cost-effective survey methods and validated statistical models that link sample data to estimates of true species richness. Lichen communities are reliable indicators for the condition of many different terrestrial ecosystems because they are sensitive to environmental stress and represent a promising system in which to develop alternative approaches to biodiversity monitoring. We propose a citizen scientist-based survey methodology for macrolichen diversity in which parataxonomic units (PUs), as identified in lichen photographs, serve as species surrogates to estimate lichen diversity. We validate this method by photographically surveying lichens at five park units previously surveyed as part of the Lichen Biomonitoring Project (LBP) at George Mason University. Using the Chao2 metric to account for variation in sampling effort, we compared observed (raw PU counts) and estimated (effort-corrected) PU and species richnesses and found that, for all park units, our methodology gave similar diversity estimates to those obtained by the LBP. While PUs provide rapid assessment of diversity within a sample, they do not address the challenge of upscaling from samples to estimate total species diversity in an area. We propose a statistical method to estimate PU richness that, unlike phenomenological methods like Chao2, can exploit replication in our sampling design to explicitly model PU occupancy and detection probability. In sum, we present new methods for both surveying diversity and extrapolating sample data that can be widely applied for rapid assessment of biodiversity.

Does disturbance regime change community assembly of angiosperm plant communities in the boreal forest?

To examine if and how species and phylogenetic diversity change in relation to disturbance, we conducted a review of ecological literature by testing the consistency of the relationship between phylogenetic diversity and disturbance and compared taxonomic groups, type of disturbance and ecosystem/habitat context. We provide a case study of the phylogenetic diversity–disturbance relationship in angiosperm plant communities of a boreal forest region, compared with types of natural and anthropogenic disturbances and plant growth forms. Using a large-scale sampling plot network along a complete (0–100%) anthropogenic disturbance gradient in the boreal biome, we compared the changes of angiosperm plant community structure and composition across plots. We estimated natural disturbance with historical records of major fires. We then calculated phylogenetic diversity indexes and determined species richness in order to compare linear and polynomial trends along disturbance gradients. We also compared the changes of community structure for different types of anthropogenic disturbances and examined how the relationships between species and phylogenetic diversity and disturbance regimes vary among three different life forms (i.e. forbs, graminoids and woody plants). Phylogenetic diversity was inconsistently related to disturbance in previous studies, regardless of taxon, disturbance type or ecosystem context. In the understudied boreal ecosystem, angiosperm plant communities varied greatly in species richness and phylogenetic diversity along anthropogenic disturbance gradients and among different disturbance types. In general, a quadratic curve described the relationship between species richness and anthropogenic disturbance, with the highest richness at intermediate anthropogenic disturbance levels. However, phylogenetic diversity was not related to disturbance in any consistent manner and species richness was not correlated with phylogenetic diversity. Phylogenetic relatedness was also inconsistent across plant growth forms and different anthropogenic disturbance types. Unlike the inconsistent patterns observed for anthropogenic disturbance, community assembly among localities varying in time since natural disturbance exhibited a distinct signature of phylogenetic relatedness, although those trends varied among plant growth forms.

Species richness and community structure of class Polyplacophora at the intertidal rocky shore on the marine priority region no. 33, Mexico

Marine Priority Region No. 33 (MPR 33) lies in the State of Guerrero, where the National Commission for Knowledge and Use of Biodiversity has declared a lack of information on marine species, Class POLYPLACOPHORA among others. This program was carried out on the rocky intertidal zone of MPR 33 with the objectives to: 1) determine species richness, 2) community composition based on families represented, 3) estimate the density, 4) index of diversity, 5) analyze body proportions and 6) geographic distribution of species. Three surveys on five sites were conducted during 2009 and 2012, using one mt2 quadrant for systematic sampling procedure; collecting all POLYPLACOPHORA specimens found within the quadrants, then proceeding with their preservation. 441 organisms were analyzed where 17 species were identified, on nine genera within six families. Fifteen new species were recorded for the MPR 33. Family ISCHNOCHITONIDAE Dall, 1889 was the best represented in species richness and CHITONIDAE Rafinesque, 1815 in abundance. Density of 8.82 organisms/m2, the H′ index was 2.38 bits/individuals and J′ = 0.57. The species Chiton (Chiton) articulatus Sowerby, 1832 showed the highest density, greater size and was found in all five collection sites. Three species, (Chiton (C.) articulatus, Ischnochiton (Ischnochiton) muscarius (Reeve, 1847) and Chiton (Chiton) alboli-neatus Broderip & Sowerby, 1829), were considered wide. Intertidal species richness was associated with habitat stability and wave intensity; the more unstable sites had greater richness while most stable sites lower. Species inventory and understanding the communities’ interactions of the marine fauna of the State of Guerrero are important; therefore these efforts must be continued.

The Environment, Not Space, Dominantly Structures the Landscape Patterns of the Richness and Composition of the Tropical Understory Vegetation

The mechanisms driving the spatial patterns of species richness and composition are essential to the understanding of biodiversity. Numerous studies separately identify the contributions of the environment (niche process) and space (neutral process) to the species richness or composition at different scales, but few studies have investigated the contributions of both types of processes in the two types of data at the landscape scale. In this study, we partitioned the spatial variations in all, exotic and native understory plant species richness and composition constrained by environmental variables and space in 134 plots that were spread across 10 counties in Hainan Island in southern China. The 134 plots included 70 rubber (Hevea brasiliensis) plantation plots, 50 eucalyptus (Eucalyptus urophylla) plantation plots, and 14 secondary forest plots. RDA based variation partitioning was run to assess the contribution of environment and space to species richness and composition. The results showed that the environmental variables alone explained a large proportion of the variations in both the species richness and composition of all, native, and exotic species. The RDA results indicated that overstory composition (forest type here) plays a leading role in determining species richness and composition patterns. The alpha and beta diversities of the secondary forest plots were markedly higher than that of the two plantations. In conclusion, niche differentiation processes are the principal mechanisms that shape the alpha and beta diversities of understory plant species in Hainan Island.

Benthic macrofauna of an estuarine lake during a drought: spatio-temporal drivers under different hydrological states

Mouth state is a key determinant of estuarine processes in arid and semi-arid regions. While this factor is well researched for periodically open systems, it is much less researched for estuarine lakes. Here we used a 4-year data set to determine spatio-temporal patterns in responses of benthic macrofauna to changes in mouth state in a subtropical estuarine lake system during a drought cycle, with a focus on understanding the ecological mechanisms driving community change. We also assessed the effects of changes in mean levels of environmental factors relative to their statistical variability (measured as standard deviation, SD) in driving changes in species richness and abundance of dominant macrofauna. Results showed that greatest variability in physico-chemical factors and macrofaunal assemblages occurred in the upper lake sections, especially under closed mouth conditions. At the community level, changes in salinity under different mouth states played an important structuring role, but were less important at the level of individual species, being important for only 1 of the 6 dominant species. Low oxygen levels under closed mouth conditions, particularly in the lake complex, were also an important determinant of macrofaunal community structure and species richness. A major finding was that variability (SD) in environmental factors was more important in determining species richness and abundance of dominant macrofauna than changes in mean levels. This suggests that, while dominant species in the systems can tolerate significant environmental changes, the rate and magnitude of change exert an important control over species abundance.