Values Of Taxonomic Distinctness Research Articles

Diversity and composition of volant and non-volant small mammals in northern Selangor State Park and adjacent forest of Peninsular Malaysia.

Volant and non-volant small mammals from three forest reserves, located inside and outside Selangor State Park, Malaysia, were trapped and documented. A total of five-line transects, each 200 m long and a total of 100 collapsible cage traps, three harp traps and ten mist nets were deployed at each study site to capture rodents and bats species. The presence of 47 species of volant and non-volant mammals was documented with the highest abundant species being Leopoldamys sabanus (n = 61). The Family Vespertilionidae was the most diverse, while Muridae was the most abundant species. Diversity indices have shown forest reserves - Gading Forest Reserve (FR) and Bukit Kutu FR – located in the State Park, have a higher species composition than the impaired adjacent forest reserve, Bukit Tarek FR extension. The taxonomic diversity and taxonomic distinctness of the three forest reserves ranged between 2.433 and 2.610, while the taxonomic distinctness values ranged between 2.638 and 2.748. Even though Gading FR recorded the highest number of species diversity, the Chao 1 diversity estimator and the rarefaction accumulation curve indicated that Bukit Kutu comprised more species. Comparisons between other state parks and national parks in Peninsular Malaysia indicated that Selangor State Park indeed harbours relatively more species of small mammals. Northern Selangor State Park and adjacent forest should be recognised as a conservation priority area, although there are comparatively more species harboured in other regions of the State Park. With the current information on fauna diversity, proper management should be formulated to preserve the existing ecosystems in order to ensure the continuity of fauna diversity in Malaysia.

Richness and taxonomic distinctness of cave invertebrates from the northeastern state of Goiás, central Brazil: a vulnerable and singular area

The karst area of the northeastern state of Goiás comprises two main municipalities: São Domingos and Posse. São Domingos is inside the limits of a Full Protection Conservation Unit known as Parque Estadual de Terra Ronca (PETeR), where a high number of caves occurs, some of them surpassing 10 km in length. Despite their protection by law, uncontrolled tourism has been threatening the integrity of the unique and fragile cave systems of São Domingos. On the other hand, the caves of Posse are much less visited, with its subterranean fauna poorly unknown and are strongly threatened by the urban areas and mining activities in the vicinity. We conducted six systematic surveys of invertebrates in 12 caves, seven of which are located in São Domingos and five in Posse, between 2010 and 2012. Immediately outside the caves, we sampled several microhabitats for comparison. We estimated richness, abundance, and taxonomic distinctness of the communities. We recorded 1,941 individuals of 344 morphospecies. Caves from São Domingos showed a higher species richness and were more taxonomic distinct than caves from Posse. Most morphospecies were considered troglophiles (188). We also found one trogloxene and one troglobite, as well as nine troglomorphic taxa that possibly are troglobitic as well. Both regions have markedly singular caves regarding its subterranean fauna, with high values of taxonomic distinctness. However, the richer caves were not necessarily the most taxonomic distinct. Conservation measures are especially necessary in the region of Posse, where caves are not legally protected and are within an area of significant urbanization. Cave entrances of Posse are near deforested vicinities, in some cases with domestic wastes and cement plants nearby.

Can land use indicate wetland floristic quality and taxonomic distinctness?

Biological integrity is continuously threatened by human activity. Impacts to biological health may be inferred directly (i.e. bioassessment), or estimated indirectly using rapidly collected field data or computer-based data layer analysis. This study tests whether surrounding land cover alteration (crops, pasture, and development in 200-m buffer) can predict and classify wetland biological health as represented by floristic quality (FQ) and taxonomic distinctness (TD). From surveys of 106 non-forested wetlands in Oklahoma during 2012–2015, we found a limited ability for land use to estimate site-specific FQ and TD values. Although the combined land uses were not a strong predictor overall, pasture land use by itself provided a weak to moderate surrogate when precipitation and ecoregion were taken into account. Floristic quality metrics and average TD decreased with increasing pasture in the 200-m buffer. Land use performed fairly well in classifying sites as biologically intact or not different from a least-altered state (5% FQ and 9% TD misclassification rate), but performed poorly in classifying sites as biologically impaired or deviating from a least-altered state (36% FQ and 24% TD misclassification rate). Importantly, classification analysis suggested that limited land use may separate higher FQ from moderate and lower FQ, whereas more intensive land use may separate lower average TD from moderate and higher average TD. This suggests that both measures (FQ and average TD) are needed for a more complete classification of wetland biological response to anthropogenic disturbance. Despite growing interest in relatively rapid or low-cost methods of wetland assessment, our results do not support using such methods in lieu of direct bioassessment.

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.

Taxonomic Diversity and Taxonomic Dominance: The Example of Forest Plantations in South-Central Chile

The study describes an analysis of the impact of plantation forestry on the taxonomic diversity of plants in south-central Chile. In this biodiversity hotspot, plantations of non-native species like Pinus radiata D. Don, Eucalyptus globules Labill. and Populus nigra L. have largely replaced native deciduous and sclerophyllous forests. The study compares taxonomic diversity of commercial plantations and native forests using taxonomic distinctness and diversity and the Simpson diversity index. Most of these indexes attest a considerably reduced taxonomic diversity to plantations. However, taxonomic distinctness values for P. radiata plantations seem to contradict other indexes at first glance. It is shown that the higher values of taxonomic distinctness of P. radiata plantations come from taxonomic dominance. Taxonomic dominance describes the fact that P. radiate—a member of the infradivison of Gymnospermae-bears only little taxonomic resemblance to other plants, which are Angiospermae. Thus, it strongly dominates the taxonomic distinctness index and the high taxonomic resemblance of other plant within its plots is neglected. Indexes are developed that identify such dominant species and adjust for taxonomic dominance in taxonomic diversity analyses. After this adjustment, all indexes provide a coherent image on taxonomic diversity. Plantation forestry produces a considerable decline of taxonomic diversity. Taxonomic diversity analysis provides valuable insights in biodiversity impacts and complements standard analyses.

山西平陆黄河湿地植物分类学多样性研究

PDF HTML阅读 XML下载 导出引用 引用提醒 山西平陆黄河湿地植物分类学多样性 DOI: 10.5846/stxb201312032872 作者: 作者单位: 山西大学 生命科学学院 太原,山西大学 生命科学学院 太原,山西大学黄土高原研究所 太原;山西大学 生命科学学院 太原 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省回国留学人员科研项目(20100012); 山西省自然科学基金项目(2013011037-1); 科技部科技基础性工作专项资助(2011FY110300) Plant taxonomic diversity in Yellow River Wetland in Pinglu, Shanxi Author: Affiliation: School of Life Science,Shanxi University,,Institute of Loss Plateau,School of Life Science,Shanxi University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:传统的物种多样性通常使用物种数量指标α和β等多样性指数进行测度,由于其对取样和样本大小有依赖关系且极其敏感,因此取样方法的不同会对多样性的结果产生显著影响。分类学多样性方法基于分类学系统关系测量物种多样性,弥补了传统方法的不足,同时面对各种变量和不受控制的取样具有稳健性,同时也考虑了集合的分类学均匀度。不仅能反映植物群落多样性,还能间接反映环境与扰动间的关系,用于识别生态系统或生境是否处于退化阶段。为了探究平陆黄河湿地的物种多样性,检验分类学多样性方法在植物生态学方面的应用,选取了16个样地进行植物调查,并结合历史资料整理了种子植物名录,结果表明平陆黄河湿地共有植物368种,隶属于36目67科213属。含种最多的科为菊科和禾本科,分别为54种和45种。应用平均分类学差异指数(Δ+)和分类学差异变异指数(Λ+)研究了各样地的植物物种多样性:Δ+和Λ+的理论平均值分别为74.24和480;位于三门峡大坝上游和下游的样地和不同群落类型的分类学多样性均没有显著差异(P>0.05)。受人类干扰较大的车村和鳖干平均分类学差异指数值显著较低, Δ+分别为62.28和67.41,位于95%的置信漏斗外;而水分条件较好且人为干扰较少的南沟渡口和三湾湖平均分类学差异指数值最高为分别81.30和79.94。车村的分类差异变异指数值最高为814.44,其物种在不同分类阶元分布最不均一,涧北的分类差异变异指数值最低为423.31,其物种分布相对较均一。传统的多样性方法难以全面的反映某个区域的物种组成、分布和多样性,此外分类学多样性的高低与物种数量的多少没有一定的相关关系, Δ+与S、Λ+与S的相关关系分别为-0.257和-0.187(P > 0.05)。耕作、生态旅游、日常活动等人为干扰因素可能是造成平陆黄河湿地分类学多样性降低及物种在不同分类等级间分布不均匀的主要原因。 Abstract:A study of traditional diversity study focuses on the number of species in a given ecosystem. Traditional indices are extremely sensitive to the sampling method and sample size; changes in sampling efforts often significantly impact on the level of diversity in an ecosystem, and it is difficult to compare data sets collected at different times and regions. Taxonomic diversity is used to measure species diversity, and not only species abundances and distribution but also taxonomic relatedness are considered. Furthermore, this method is robust and minimally influenced by variables or uncontrolled sampling efforts. On the other hand, taxonomic evenness of an assemblage should also be considered. It not only reflects community diversity; but also provides information on the relationship between environmental factors and indirect disturbance, which are often applied to identify whether the ecological system or environment is undergoing degradation. To explore the species diversity in Yellow River Wetlands, Pinglu,Shanxi, and to test the application of taxonomic diversity in plant ecology, 16 sites were chosen around the Sanmenxia Dam, Pinglu and a species list was established. In the present study, 368 species belonging to 213 genera, 67 families and 36 orders were recorded in this region. Most of the species belonged to the families Compositae (54 species) and Poaceae (45 species). Plant species diversity was studied using average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) and a confidence funnel was obtained. The expected value of Δ+ and Λ+ were 74.24 and 480, respectively. No significant difference were observed among the different stands both upstream and downstream of Sanmenxia Dam and various community types (P>0.05). The average taxonomic distinctness values of Checun (62.28) and Biegan (67.41), which severely disturbed by human activities, were lower and below the confidence limit. The average taxonomic distinctness values for Nangou Ferry and Sanwan Lake, which were sites with better water availability and less disturbance, were higher, (81.30 and 79.94,respectively). The value of Λ+in Checun (814.44) was the highest, suggesting that the species distribution in this site was less homogeneous. The value of Λ+ in Jianbei (423.31) was the lowest, with species distribution being homogeneous. Traditional diversity methods hardly reflect species composition, distribution and diversity; and there is no certain correlations between taxonomic diversity and species number. The correlation coefficient between Δ+ and S was 0.257(P > 0.05), and that between Λ+ and S was -0.187(P > 0.05). Anthropogenic activites such as cultivation and tourism are dominant factors that have caused the significant decrease in taxonomic diversity and non-uniform sapatial distribution of species of different taxa in Yellow River Wetlands. 参考文献 相似文献 引证文献

Taxonomic Diversity, Distinctness, and Abundance of Tree and Shrub Species in Kasagala Forest Reserve in Uganda: Implications for Management and Conservation Policy Decisions

The successful management of natural resources requires access to adequate information on social, economic, ecological, and cultural changes in order to mitigate their impacts through conservation interventions. In most cases, such information is provided in the form of simple diversity indices, which may not predict the complex nature of species functioning in ecosystems. In this study, we used rank abundance, analysis of similarities (ANOSIM), similarity percentages (SIMPER), and taxonomic-diversity and distinctness indices to show the status of tree and shrub species in Kasagala forest reserve in central Uganda. Four 100 × 100 m plots were established in four vegetation strata of the strict nature reserve of the forest, and diameter at breast height (DBH) of trees and shrubs ≥ 5 cm measured. There was no significant difference in species abundance in the four vegetation strata (Kruskal Wallis H = 2.614, p = 0.453; ANOSIM: R = −0.334, p = 0.995). The taxonomic diversity and distinctness of the four vegetation types ranged between 2.414 and 2.786 while the taxonomic distinctness values ranged between 2.897 and 2.978. The taxonomic diversity of the forest is generally even, suggesting a homogeneous community. We suggest that the managers of the forest constitute a continuous monitoring program aimed at controlling the impact of anthropogenic factors, one of the main influences for such low taxonomic distinctness values observed for this forest.

Measures of taxonomic distinctness do not reliably assess anthropogenic impacts on intertidal mollusc communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 413:81-93 (2010) - DOI: https://doi.org/10.3354/meps08713 Measures of taxonomic distinctness do not reliably assess anthropogenic impacts on intertidal mollusc communities Trudy L. Costa1,2,3, Timothy D. O'Hara1,*, Michael J. Keough2 1Sciences Department, Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia 2Department of Zoology, University of Melbourne, Victoria 3010, Australia 3Present address: School of Biological Sciences, University of Wollongong, New South Wales 2500, Australia *Corresponding author. Email: tohara@museum.vic.gov.au ABSTRACT: Indices of taxonomic distinctness measure the taxonomic breadth of a community and may be more sensitive to human impacts than conventional diversity indices. They have the advantage of being, in theory, insensitive to sampling effort and can be calculated using presence/absence data. The average taxonomic distinctness index and variation in taxonomic distinctness index were used to assess the effects of putative human impacts on molluscan community composition at 63 rocky intertidal platforms on the coast of Victoria, Australia. The use of 2 sampling techniques, viz. timed searches and quadrats, was compared. Sites exposed to sewage discharge maintained high taxonomic distinctness, and those exposed to high levels of human visitation did not have consistently lower values than controls. Results varied, sometimes markedly, depending on which survey technique was used. Neither average taxonomic distinctness nor its variance were strongly correlated with large-scale environmental gradients, small-scale habitat differences or other diversity indices. It is most likely that taxonomic distinctness measures did not discriminate sites exposed to putative disturbance because of the high taxonomic diversity of intertidal mollusc assemblages, and because low values of taxonomic distinctness were not exclusive of impacted conditions. KEY WORDS: Trampling · Sewage · Disturbance · TAXDTEST · Community composition · Invertebrate · Diversity Full text in pdf format PreviousNextCite this article as: Costa TL, O'Hara TD, Keough MJ (2010) Measures of taxonomic distinctness do not reliably assess anthropogenic impacts on intertidal mollusc communities. Mar Ecol Prog Ser 413:81-93. https://doi.org/10.3354/meps08713Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 413. Online publication date: August 26, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Spatial patterns of biodiversity in the Black Sea: An assessment using benthic polychaetes

The current study broadens the biodiversity information available for the Black Sea and neighbouring regions and improves our knowledge about the polychaete biogeographic patterns to be discerned in them. There appears to be a well-defined zoogeocline from the Marmara Sea and Bosphorus Strait to the inner parts of the region (Azov Sea), depicted both as a multivariate pattern and in terms of species (or taxa) numbers. The emergent multivariate pattern complies, to a certain extent, with Jakubova’s (1935) views: three main sectors can be defined in the basin: (a) Prebosphoric, (b) the Black Sea and, (c) the Azov Sea, whereas the Bosphorus Strait and Marmara Sea show less faunal affinities with the afore-mentioned sectors. Patterns derived both from the cosmopolitan and Atlanto-Mediterranean species closely follow the one coming from the polychaete species and genera inventories. As a general trend, species numbers decrease along with the decrease in salinity towards the inner parts of the region. The trend is homologous to that seen in the benthic invertebrate inventories of all the major European semi-enclosed regional seas. Salinity and food availability appear to be the dominant abiotic factors correlated, though weakly, with the various patterns deriving from the taxonomic/zoogeographic categories. With the exception of the Anatolia, polychaete inventories from all sectors appear to be random samples of the total inventory of the region, in terms of taxonomic distinctness values. Therefore, these sectoral inventories can be used for future biodiversity/environmental impact assessment studies. A massive invasion of Mediterranean species after the opening of the Black Sea, in the lower Quaternary period, appears to be the likely biogeographic mechanism through which the old Sarmatic fauna was almost completely replaced by species of marine origin.

A Retrospective Analysis and Comparative Study of Stony Coral Assemblages in Biscayne National Park, FL (1977–2000)

The hardbottom, patch, and bank reefs of Biscayne National Park (BNP) are among the most northern reef communities in the Florida Keys reef tract. The close proximity of BNP reefs to highly developed areas (i.e., the greater Miami metropolitan area) make them both heavily used and susceptible to a multitude of anthropogenic stresses. This study analyzes a unique 1977–1981 data set on stony-coral abundances and percent cover, collected from eight reefs in BNP, and compares this more than 25-year old data set with published data from surveys conducted from 1994–1996 and 1998–2000. In 1977–81, stony-coral cover on the eight reefs ranged between 8% and 28%, whereas coral cover reported from surveys in 1998–2000 ranged between 0.4% and 10%. Significant declines in cover of all coral species were seen at BNP reefs in the ? 20 years between data sets, although few changes were observed in species richness and taxonomic distinctness values. Spatial differences were observed between lagoonal patch reefs and outer bank reefs, consistent with previous reports of greater loss of coral cover on offshore reefs. Previous reports have suggested that high juvenile coral mortality due to fish predation, physical stresses, and thermal stresses have contributed to reduced cover at offshore BNP reefs.

Biodiversity of benthic assemblages on the Arctic continental shelf: historical data from Canada

This study describes patterns of abundance, diversity, and assemblages of benthic macrofauna within the Canadian Arctic Archipelago. A review of data reports and the published literature yielded 219 stations and 947 taxa from 7 sources in various regions of the Canadian Arctic Archipelago (i.e. Beaufort Sea and Mackenzie Shelf, Victoria Island, Hudson and James Bays, Frobisher Bay, Ungava Bay, and Southern Davis Strait). In general, we observed that eastern regions of the Canadian Arctic Archipelago showed greater values of species richness (or α diversity) than the western and central regions, whereas no specific patterns were observed for Shannon-Wiener's diversity (H') and Pielou's evenness (J') indices. The Beaufort Sea and Mackenzie Shelf region exhib- ited high values of taxonomic distinctness (Δ + ), whereas Hudson Bay showed low values. However, the Hudson Bay region showed high values of turnover (βW) diversity. A non-metric multi-dimen- sional scaling plot of similarity (Bray-Curtis index) and analysis of similarity revealed that species composition differed among regions, even those located in close proximity to one another. These investigations were conducted at different levels of taxonomic resolution (Species, Order, Class and Phyla) and the results demonstrated that most patterns were maintained up to the Order and Class level. A relatively small number of taxa, mainly annelids, were responsible for most of the dissimilar- ity among regions. Bottom salinity and temperature were the most important environmental variables (among depth of site, bottom temperature, salinity, physical and chemical sediment characteristics) for determining these assemblage patterns. Multiple regression analyses also demonstrated that vari- ance in species richness and diversity (H') was best explained by variance in salinity (55 and 43% respectively). The analysis of a time series from Frobisher Bay revealed that the temporal (mo/yr- scale) variability of assemblages was of the same order as the spatial (km-scale) variability among sites.

Is the Arabian Gulf really such a lowspot of biodiversity?: Scaling effects and management implications

Analysis of echinoderm datasets for the Arabian Gulf and Red Sea region reveals lower species richness in the Gulf at 4 different spatial scales: Point, Sample, Large area and Biogeographical province. Species richness correlates positively with spatial scale in both regions, as does endemism, although levels of the latter are comparable for both regions. Values of taxonomic distinctness (Δ*), a relatedness measure based on average properties, are very similar for the Gulf and the Red Sea over all spatial scales. This might seem surprising, given that (i) the Gulf's environment is highly stressful, and (ii) the Red Sea is one the world's top 10 coral reef high diversity areas, and the habitat associated with most echinoderm records for this region, but not for the Gulf. These findings may partly reflect the behaviour of Δ* to ‘saturate’ (reach maximal values as sampling/spatial scale increases) much sooner than species richness, endemism and other ‘species’ measures. Our results suggest the Gulf may not be the lowspot of biodiversity generally acclaimed, especially if a broad set of measures is utilised. Biodiversity is an important constituent of ecosystem health and criterion for determining where conservation attention should be targeted. Until the functional/ecological significance of Δ* is better understood, management implications of our study's findings remain unclear. Further attention should also be given to β-diversity, the change in species composition along a gradient. We also stress that any conclusions drawn from the study are tentative, pending compilation and analysis of datasets for other groups.

Mediterranean Lagoons Revisited: Weakness and Efficiency of the Rapid Biodiversity Assessment Techniques in a Severely Fluctuating Environment

The purpose of this paper is to test the performance of rapid biodiversity assessment techniques in the lagoonal environment at the pan-Mediterranean scale. The multivariate techniques can produce patterns of lagoonal biodiversity along the Mediterranean. Additionally, it is shown that the polychaete inventory can preferably be used rather than the aggregation of information at the family level for the purposes of rapid biodiversity assessment. These techniques, however, appear to be weak for the environmental assessment because they cannot detect differences between the naturally disturbed and the anthropogenically impacted lagoons. Both taxonomic distinctness indices are found to be robust in providing meaningful results for rapid biodiversity/environmental assessment when the crustacean inventory and the polychaete and molluscan ones are used for the estimation of the average taxonomic distinctness and of the variation in taxonomic distinctness values, correspondingly. Conversely, information on the distribution of the macrofaunal species to the Mediterranean lagoons appears to be inadequate for the needs of such rapid biodiversity assessment at a regional scale. It is suggested that information on ecological convergence of the macrofaunal species would probably provide biodiversity indices with additional power, at least in the lagoonal environment.

An assessment of two taxonomic distinctness indices for detecting seaweed assemblage responses to environmental stress

We tested the efficacy of two biodiversity indices, average taxonomic distinctness and variation in average taxonomic distinctness, for indicating environmental stress in seaweed assemblages from the Bay of Fundy, New Brunswick, Canada. These indices, which measure the average number of taxonomic levels between species in a sample, offer a potential panacea for biomonitoring because their calculation requires only a species list and a regional taxonomic hierarchy, they offer a statistical framework for testing whether assemblages deviate from an expected taxonomic breadth, and previous studies involving animal assemblages have demonstrated an independence from sampling effort. However, our results were not consistent with previously published studies or with our perception of site conditions. Specifically, putatively impacted sites scored above-average taxonomic distinctness values, while sites otherwise regarded as healthy were indicated as environmentally degraded. We also demonstrate that average taxonomic distinctness values can be negatively correlated with species richness, Shannon diversity and with functional diversity. Further, increasing the breadth of the regional species list to which specific sites were compared resulted in a more conservative test of impact. We recommend that a qualitative understanding of how specific biotic assemblages respond to stress is a necessary prerequisite to use the taxonomic distinctness indices for environmental stress assessments.

Host introductions and the geography of parasite taxonomic diversity

AbstractAim Geographical variation in parasite diversity is examined among populations of fish in their original heartland and in areas where they have been introduced. The diversity in heartland and introduced populations is contrasted, and also compared with the expectations of a null model.Location Data on the parasite communities of two salmonid fish species were obtained: the rainbow trout Oncorhynchus mykiss in its British Columbia heartland and in introduced populations in North America, Great Britain, South America and New Zealand; and the brown trout Salmo trutta in heartland populations from Great Britain, and in introduced populations in North America, South America and New Zealand.Methods The average taxonomic distinctness and its variance were computed for each parasite community, and used as measures of the taxonomic diversity of parasite species in each fish population. Observed values of taxonomic distinctness were also compared with those expected if each community was a random selection from the world list of parasite species known for each of the two host species.Results Few parasite communities departed from the expectations of the null model, i.e. few had a taxonomic diversity of parasites greater or lower than that expected from a random selection of parasite species. However, these departures were not more or less likely among heartland fish populations than among introduced ones. In both fish species, parasite communities in introduced populations tended to be a little more taxonomically diverse than in the heartland populations.Main conclusions Overall, the results suggest that the accumulation of parasite species in introduced hosts over short (ecological) periods of time can result in parasite assemblages that are just as, or even more, taxonomically diverse than those developed over much longer (evolutionary) time frames in the host species geographical heartland. This finding highlights the importance of ecological factors in parasite biodiversity in addition to coevolutionary processes.

The taxonomic distinctness measure of biodiversity:weighting of step lengths between hierarchical levels

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 184:21-29 (1999) - doi:10.3354/meps184021 The taxonomic distinctness measure of biodiversity: weighting of step lengths between hierarchical levels K. R. Clarke*, R. M. Warwick Centre for Coastal and Marine Sciences, Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL1 3DH, United Kingdom *E-mail: b.clarke@pml.ac.uk ABSTRACT: Taxonomic distinctness is a univariate (bio)diversity index which, in its simplest form, calculates the average 'distance' between all pairs of species in a community sample, where this distance is defined as the path length through a standard Linnean or phylogenetic tree connecting these species. It has some appealing properties: it attempts to capture phylogenetic diversity rather than simple richness of species and is more closely linked to functional diversity; it is robust to variation in sampling effort and there exists a statistical framework for assessing its departure from 'expectation'; it appears to decline monotonically in response to environmental degradation whilst being relatively insensitive to major habitat differences; and, in its simplest form, it utilises only simple species lists (presence/ absence data). Many of its practical characteristics remain to be explored, however, and this paper concentrates on the assumptions made about the weighting of step lengths between successive taxonomic levels (species to genera, genera to families etc.), which when accumulated give the overall path lengths. Using data on free-living marine nematodes from 16 localities/habitat types in the UK, it is shown that the relative values of taxonomic distinctness for the 16 sets are robust to variation in the definition of step length. For example, there is a near perfect linear relationship between values calculated using a constant increment at each level and a natural alternative in which the step lengths are proportional to the number of species per genus, genera per family, family per suborder etc. These weightings are then manipulated in more extreme ways, to capture the structure of phylogenetic diversity in more detail, and a contrast is drawn between the biodiversity of island (the Isles of Scilly) and mainland (UK) locations and habitats. This paper concludes with a discussion of some of the strengths and weaknesses of taxonomic distinctness as a practical tool for assessing biodiversity. KEY WORDS: Biodiversity · Taxonomic distinctness · Nematodes · Island biogeography · Isles of Scilly · Mainland Britain Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 184. Publication date: July 28, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Taxonomic distinctness and environmental assessment

Summary The objectives of this paper are to test the performance of the taxonomic distinctness index, δ+, in a number of environmental impact scenarios, to examine its relationship with functional diversity and to examine the influence of habitat type and diversity on the index. The index was applied to data on free‐living marine nematodes from the coasts of Britain and Chile. The taxonomic distinctness of nematodes from environmentally degraded locations was generally reduced in comparison with that of more pristine locations, often significantly so. Some habitat types may have naturally lower values of taxonomic distinctness than others. However, unless the habitats are degraded in some way the δ+ values do not generally fall below the lower 95% confidence limit of the simulated distribution under a null hypothesis that the assemblages behave as if they are a random selection from the regional species pool. This ameliorates the problem encountered with species richness measures of biodiversity, which are much more strongly affected by habitat type and complexity, thus making comparisons difficult between data sets from different habitats or where habitat type is uncontrolled. Taxonomic distinctness in marine nematodes is shown to be related to trophic diversity: a reduction in trophic diversity will lead to a reduction in taxonomic distinctness, although not necessarily to a reduction in species richness. Trophic composition itself is clearly affected by pollution, but is also strongly responsive to the major influence of habitat type. These features of the taxonomic distinctness index, coupled with its lack of dependence on sampling effort or differences in taxonomic rigour between workers and a statistical framework for the assessment of the significance of departure from expectation, suggest that it may prove to be a biologically and ecologically relevant measure of biodiversity. This paper demonstrates that the taxonomic distinctness index has a number of theoretical and logistical advantages over measures of species richness for the purposes of environmental assessment.