ON SPECIES and OTHER TAXA

Abstract— It is argued that taxa, whether Linnaean or phylogenetic, belong to Popper's worlds 2 and 3, the worlds of knowledge, but that they represent entities residing in world 1, the world of objects, namely, classes of living beings. The Linnaean taxa are concepts, and thus untestable, whereas phylogenetic taxa are statements, the monophyletic taxa being true, and the paraphyletic and polyphyletic ones false statements. The taxa are neither strictly nor numerically universal statements, but probabilistic ones which cannot be falsified by single observations. It is suggested that the classical "species problem" is due to the fact that "species" has been used in three different senses. First, traditionally it has been assumed that the specific "essence" of an organism is that by which it is what it is. When we know the species, we know the organism. Second, the species are terminal taxa in the phylogenetic hierarchy. This implies that it is only a very small part of the "essence" of the organism which distinguishes the species. The remaining part characterizes the succession of superior taxa in the phylogenetic lineage which ends with the species in question. Third, the species has been regarded to be the "evolutionary unit." This idea may be refuted for two reasons: (1) since concepts and statements cannot evolve, species cannot evolve either, and (2) it is generally in very small isolated populations that evolutionary innovations are first established. In Linnean systematics the superior taxa are allotted categorical rank. The fact that the classification is constrained by this conventional stipulation implies that the superior taxa are often man-made artifacts. In the phylogenetic hierarchy, composed of monophyletic taxa, the ontological states of the taxa is completely independent of their numerical rank; the kingdom is as "real" as the species.     

Indicator taxa revisited: useful for conservation planning?

Aim Indicators for biodiversity are needed to facilitate the identification of complementary reserve networks for biodiversity conservation. One widely adopted approach is to use indicator taxa, i.e. a single taxon such as birds or butterflies, despite the ongoing debate regarding their usefulness as indicators of broader biodiversity. Here we assess several aspects, such as influence of species number, of indicator taxa for three extensive data sets to improve our insight into the effectiveness of indicator taxa. Location Denmark, sub‐Saharan Africa and Uganda. Methods First, we investigate to what extent variation in species number between indicator taxa (e.g. 488 mammal spp. vs. 210 snake spp.) is causing the differences in effectiveness between indicator taxa. Second, we investigate whether indicator taxa are capable of outperforming indicator groups composed of random sets of species chosen among all taxa. Finally, we assess the correlation of specific properties such as mean range size of the indicator taxa to their effectiveness. We investigate these aspects of the effectiveness of indicator taxa through the separate analysis of three distinct distributional species data sets: sub‐Saharan Africa (4,039 spp.), Denmark (847 spp.) and Uganda (2,822 spp.). Results We overall found that indicator taxa comprising a greater number of species tend to perform better than indicator taxa with fewer species (e.g. 488 mammal spp. outperform 210 snake spp.), although there are some exceptions. Second, we found most indicator taxa to perform worse than indicator groups consisting of a comparable number of species selected among all taxa. Finally, the effectiveness of indicator taxa was seen to correlate poorly with selected distributional properties such as mean range size of the indicator taxa, suggesting that it is difficult to predict which taxa are efficient biodiversity indicators. Main conclusions Overall, these findings might suggest that focus should simply be on increasing the number of species among all taxa as basis for priority setting, rather than striving to obtain the ‘perfect’ indicator taxa.     

高黎贡山兰花的多样性

对高黎贡山兰科植物的生物地理学和多样性进行了研究。1.兰科是高黎贡山种子植物中最大的科,包括75属265种。2.高黎贡山兰花起源于新、旧世界的热带和温带, 热带属占60%(45属),温带属占38.67%(29属),包括2个云南特有属。但是,高黎贡山兰科植物与地中海地区和中亚地区的联系十分微弱。3.高黎贡山的兰花以地生兰为主。这里,57.33%(43属)为地生兰,而附生兰和腐生兰仅分别为31属和3属。4.兰花物种的分布区式样表明高黎贡山兰花以温带兰为主 温带兰占总种数的69.43%(184种),包括东亚成分即滇西高黎贡山-东喜马拉雅分布的种和中国西南部特有种,它们是高黎贡山兰花区系的核心。5.高黎贡山兰科的特有现象在于1)具有云南二个特有属蜂腰兰Bulleyia和反唇兰Smithorchis;2)有高黎贡山特有种21个,如泸水兜兰Paphiopedilum markianum,贡山风兰Cymbidium gongshanense,贡山贝母兰Coelogyne gongshanense,热带附生兰——万带兰亚科在高黎贡山没有形成特有种;3)高黎贡山北段的特有种比南段丰富贡山有14种,腾冲仅有4种; 海拔1800～2100 m的梯度带特有种最多(13种);4)高黎贡山有云南特有种10种,其中小花槽舌兰Holcoglossum junceum是一个热带种,因为板块位移而来到了亚热带地域;5)高黎贡山的兰科植物中有19.25%(51种)是中国特有种,它们出现在高黎贡山,分布在云南其他地区和西南的一些省区。高黎贡山特有种,分布到高黎贡山的云南特有种和分布到高黎贡山的中国特有种一共为82种,占高黎贡山兰科总种数的30.91%, 兰科在高黎贡山是一个特有化程度很高的类群。     

A meta-analysis of spatial relationships in species richness across taxa: Birds as indicators of wider biodiversity in temperate regions

AimIndicators are an important tool by which conservationists monitor biodiversity because resources and expertise needed to survey biodiversity in a more direct way are often lacking. We aim to examine the effectiveness of species richness in birds as an indicator of species richness in other taxa. Birds are perhaps the most widely monitored species group so it is important to understand whether they can act as surrogates for distribution and abundance of other taxa.MethodsWe use a meta-analytical approach to assess the effectiveness of birds as indicators of cross-taxonomic species richness on spatial data from terrestrial temperate studies.ResultsThe literature showed mixed results but, in general, species richness in birds only weakly reflected species richness in other taxa. On average 19% of the variation in total species richness in other taxa was explained by species richness in birds. This is marginally higher than results found in a previous meta-analysis of species richness correlations between all taxa. Birds were more effective at reflecting cross-taxa species richness in study areas that were dominated by agricultural mosaics or mixtures of habitat types; they were less effective in forests and grassland environments. Overall, birds were better at reflecting species richness in mammals than other taxa, and relationships were more effective at larger spatial scales.Main conclusionsSpecies richness in birds only weakly reflected that of other taxa. Birds might be most useful as indicators of spatial variation in wider biodiversity in relatively patchy environments and for taxa that have similar spatial requirements. Species richness is one of many potential metrics for measuring biodiversity. There is a need to assess whether temporal change in bird populations and assemblages, as opposed to spatial variation, reflects change in other taxa and to identify elements of biodiversity for which birds could be the most effective surrogates.     

Vulnerable taxa of European Plecoptera (Insecta) in the context of climate change

We evaluated 516 species and/or subspecies of European stoneflies for vulnerability to climate change according to autoecological data. The variables considered were stream zonation preference, altitude preference, current preference, temperature range preference, endemism and rare species. Presence in ecoregions was used to analyse the vulnerability of taxa in relation to their distribution. We selected the variables that provided information on vulnerability to change in climate. Thus, we chose strictly crenal taxa, high-altitude taxa, rheobionts, cold stenotherm taxa, micro-endemic taxa and rare taxa. Our analysis showed that at least 324 taxa (62.79%) can be included in one or more categories of vulnerability to climate change. Of these, 43 taxa would be included in three or more vulnerability categories, representing the most threatened taxa. The most threatened species and the main factors affecting their distribution are discussed. Endangered potamal species, with populations that have decreased mainly as a consequence of habitat alteration, also could suffer from the effects of climate change. Thus, the total number of taxa at risk is particularly high. Not only are a great diversity of European stoneflies concentrated in the Alps, Pyrenees and Iberian Peninsula, but so are the most vulnerable taxa. These places are likely to be greatly affected by climate change according to climate models. In general, an impoverishment of European Plecoptera taxa will probably occur as a consequence of climate change, and only taxa with wide tolerance ranges will increase in abundance, resulting in lower overall faunal diversity.     

Assessment of available anatomical characters for linking living mammals to fossil taxa in phylogenetic analyses

Analyses of living and fossil taxa are crucial for understanding biodiversity through time. The total evidence method allows living and fossil taxa to be combined in phylogenies, using molecular data for living taxa and morphological data for living and fossil taxa. With this method, substantial overlap of coded anatomical characters among living and fossil taxa is vital for accurately inferring topology. However, although molecular data for living species are widely available, scientists generating morphological data mainly focus on fossils. Therefore, there are fewer coded anatomical characters in living taxa, even in well-studied groups such as mammals. We investigated the number of coded anatomical characters available in phylogenetic matrices for living mammals and how these were phylogenetically distributed across orders. Eleven of 28 mammalian orders have less than 25% species with available characters; this has implications for the accurate placement of fossils, although the issue is less pronounced at higher taxonomic levels. In most orders, species with available characters are randomly distributed across the phylogeny, which may reduce the impact of the problem. We suggest that increased morphological data collection efforts for living taxa are needed to produce accurate total evidence phylogenies.     

Body size trends in a Holocene island bird assemblage

Despite the robust observation in macroecology that there are many small-bodied species, recent comparative studies have found little evidence for elevated net rates of diversification among small-bodied species within taxa. Here we examine the relationship between body size and species richness using the New Zealand land bird fauna, a well resolved palaeoecological Holocene assemblage. We test whether there is any evidence that net cladogenesis depended on body size in an assemblage prior to the impact of human-induced extinction. We also test whether net cladogenesis depends on the level at which taxa are endemic to New Zealand, to see whether there is evidence for bursts of cladogenesis following taxon establishment, and examine how the body sizes of New Zealand land birds relate to those in Australia, the most likely source pool for colonising taxa. Most New Zealand land bird species are small-bodied. We find no evidence, however, that this is due to higher net cladogenesis in small-bodied taxa. The body mass distributions of endemic and recent colonist species do not differ statistically, but recent colonists tend to be smaller-bodied than their closest endemic relative. This tendency is more marked for small-bodied than large-bodied taxa. More endemic taxa do not tend to be more species rich in New Zealand, although there is a positive relationship between level of endemism and species richness for forest taxa. The body mass distribution of New Zealand birds is very similar to that for Australia. Body mass does not dictate the likelihood that a family has colonised New Zealand from Australia, but the number of species in the family does: it is the species rich Australian families that have successfully colonised. We discuss the implications of these results for the evolution of body size distributions, and for the "island rule" of body size evolution on islands.     

Species monophyly

In biological systematics, as well as in the philosophy of biology, species and higher taxa are individuated through their unique evolutionary origin. This is taken by some authors to mean that monophyly is a (relational) property not only of higher taxa, but also of species. A species is said to originate through speciation, and to go extinct when it splits into two daughter species (or through terminal extinction). Its unique evolutionary origin is said to bestow identity on a species through time and change, and to render species names rigid designators. Species names are thus believed to function just like names of supraspecific taxa. However, large parts of the Web of Life are composed of species that do not have a unique evolutionary origin from a single population, lineage or stem-species. Further, monophyly is an ambiguous concept if it is defined simply in terms of 'unique evolutionary origin'. Disambiguating the concept by defining a monophyletic taxon as 'a taxon that includes the ancestor and all, and only, its descendant' renders monophyly inapplicable to species. At the heart of the problem lies a fundamental distinction between species and monophyletic taxa, where species form mutually exclusive reticulated systems, while higher taxa form inclusive hierarchical systems. Examples are given both at the species level and below to illustrate the problems that result from the application of the monophyly criterion to species. The conclusion is that the concepts of exclusivity and monophyly should be treated as non-overlapping: exclusivity marks out a species synchronistically, i.e. in the present time. Monophyly marks out clades (groups of species) diachronistically, i.e. within an historical dimension.     

Chromosome numbers in the tribe Anthemideae (Asteraceae) from north-east Anatolia

Twenty-two chromosome counts of 19 taxa in the tribe Anthemideae of the family Asteraceae are reported from north-east Anatolia, Turkey. The taxa belong to the subtribes Achilleinae (four Achillea taxa), Anthemidinae (five Anthemis taxa), Artemisiinae (two Artemisia species), Leucantheminae (one Lecanthemum species), Matricariinae (two Tripleurospermum species) and Tanacetinae (five Tanacetum taxa). Six counts are new reports, seven are not consistent with previous counts, and the remainder are confirmations of very limited previous data. Most of the populations of Anthemideae studied have the basic number x  = 9, with ploidy levels ranging from 2 x to 7 to 8 x , but dysploidy is also present, with one diploid species, Artemisia austriaca , having x  = 8.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 203–211.     

Species distributions, surrogacy, and important conservation regions in Canada

Conservation actions could be more efficient if there is congruence among taxa in the distribution of species. Patterns in the geographical distribution of five taxa were used to identify nationally important regions for conservation in Canada. Two measures of surrogacy were significantly and positively correlated among taxa, and conservation areas selected for one taxon represented other taxa significantly better than random selections. However, few large protected areas exist in the sites of highest conservation value in southern Canada; these regions are therefore a priority for future conservation regard. By focusing this effort on threatened and endangered species, which are a national priority in Canada, most other species could also benefit.     

Testing for equal rates of cladogenesis in diverse taxa

Taxa differ widely in numbers of species, which may be due either to chance alone or to factors that cause differences in speciation and extinction rates between taxa. To test whether an observed distribution of species over taxa differs from the distribution expected from chance alone, one must take into account that neither speciation nor extinction rates are known. This paper introduces a way to estimate speciation and extinction probabilities from the distribution of extant species over families and to test whether the observed distribution is different from expected. Application of this procedure to the distributions of bird, hexapod, primate, and angiosperm species over taxa provides statistical evidence of differences in rates of cladogenesis between taxa.     

A phylogenetic study of the generic relationships within the subtribe Leucophoropterina Schuh (Miridae: Phylinae: Leucophoropterini)

The subtribe Leucophoropterina (Miridae: Phylinae: Leucophoropterini) is a relatively small lineage of mirids comprising 23 genera and 104 species. Most of the species are endemic to the Indo‐Pacific and Australia, and many are considered ant mimics. A phylogenetic analysis including both the Australian and the Indo‐Pacific taxa was conducted for the first time with a dataset of 137 morphological characters coded for all but two known species of Leucophoropterina. The hypothesis by Schuh ( 1984 ) of at least two major lineages of ant‐mimicking taxa based on his analysis of the Indo‐Pacific taxa continues to be supported with our inclusion of Australian taxa. The Australian taxa and Indo‐Pacific taxa of Leucophoropterina do not form independent, geographically based lineages, but instead comprise several lineages containing taxa from both regions. This study provides a basis for future detailed studies of biogeography and ant mimicry in the group.     

Biosystematics of the genus Piperia Rydb. (Orchidaceae)

Piperia is a North American segregate of Habenaria consisting of 5 taxa (4 species and 1 subspecies). The genus is defined and differentiated from other North American genera of the Habenaria alliance by its morphology and pollination mechanism. All taxa have n = 21 chromosomes. Thin-layer chromatography of fresh leaf extracts and a morphological assessment revealed discrete, but variable, taxa. All species are partially interfertile; however, a high degree of sympatry suggests these species are reproductively isolated. One new combination is proposed: P. elongata subsp. michaelii.     

江苏野菜资源的利用与开发

江苏野菜资源丰富,共计１９２种,隶属４４科１０８属,其中蕨类植物７科１５属５１种,种子植物３７科９３属１４１种。江苏野菜利用历史悠久,近年已发展成为规模种植,产生良好的经济效益和社会效益。     

Ectomycorrhizal fungi associated with ponderosa pine and Douglas-fir: a comparison of species richness in native western North American forests and Patagonian plantations from Argentina

The putative ectomycorrhizal fungal species registered from sporocarps associated with ponderosa pine and Douglas-fir forests in their natural range distribution (i.e., western Canada, USA, and Mexico) and from plantations in south Argentina and other parts of the world are listed. One hundred and fifty seven taxa are reported for native ponderosa pine forests and 514 taxa for native Douglas-fir forests based on available literature and databases. A small group of genera comprises a high proportion of the species richness for native Douglas-fir (i.e., Cortinarius, Inocybe, and Russula), whereas in native ponderosa pine, the species richness is more evenly distributed among several genera. The comparison between ectomycorrhizal species richness associated with both trees in native forests and in Patagonia (Argentina) shows far fewer species in the latter, with 18 taxa for the ponderosa pine and 15 for the Douglas-fir. Epigeous species richness is clearly dominant in native Douglas-fir, whereas a more balanced relation epigeous/hypogeous richness is observed for native ponderosa pine; a similar trend was observed for Patagonian plantations. Most fungi in Patagonian Douglas-fir plantations have not been recorded in plantations elsewhere, except Suillus lakei and Thelephora terrestris, and only 56% of the fungal taxa recorded in Douglas-fir plantations around the world are known from native forests, the other taxa being new associations for this host, suggesting that new tree + ectomycorrhizal fungal taxa associations are favored in artificial situations as plantations.     

Co-occurrence patterns of common and rare leaf-litter frogs, epiphytic ferns and dung beetles across a gradient of human disturbance

Indicator taxa are commonly used to identify priority areas for conservation or to measure biological responses to environmental change. Despite their widespread use, there is no general consensus about the ability of indicator taxa to predict wider trends in biodiversity. Many studies have focused on large-scale patterns of species co-occurrence to identify areas of high biodiversity, threat or endemism, but there is much less information about patterns of species co-occurrence at local scales. In this study, we assess fine-scale co-occurrence patterns of three indicator taxa (epiphytic ferns, leaf litter frogs and dung beetles) across a remotely sensed gradient of human disturbance in the Ecuadorian Amazon. We measure the relative contribution of rare and common species to patterns of total richness in each taxon and determine the ability of common and rare species to act as surrogate measures of human disturbance and each other. We find that the species richness of indicator taxa changed across the human disturbance gradient but that the response differed among taxa, and between rare and common species. Although we find several patterns of co-occurrence, these patterns differed between common and rare species. Despite showing complex patterns of species co-occurrence, our results suggest that species or taxa can act as reliable indicators of each other but that this relationship must be established and not assumed.     

Global analysis reveals that cryptic diversity is linked with habitat but not mode of life

The ubiquity of genetically distinct, cryptic species is limiting any attempt to estimate local or global biodiversity as well as impeding efforts to conserve species or control pests and diseases. Environmental factors or biological traits promoting rapid diversification into morphologically similar species remain unclear. Here, using a meta‐analysis of 1230 studies using DNA sequences to search for cryptic diversity in metazoan taxa, we test two hypotheses regarding the frequency of cryptic taxa based on mode of life and habitat. First, after correcting for study effort and accounting for higher taxonomic affinities and biogeographical region of origins, our results do not support the hypothesis that cryptic taxa are more frequent among parasitic than free‐living taxa. Second, in contrast, the results support the hypothesis that cryptic taxa are more common in certain habitats than others: for a given study effort, more cryptic taxa are found in freshwater than in terrestrial or marine taxa. These findings suggest that the greater heterogeneity and fragmentation of freshwater habitats may promote higher rates of genetic differentiation among its inhabitants, a general pattern with serious implications for freshwater conservation biology.