When is a parasite species a species?

Regrettably, 140 years after the publication of Darwin's Origin of Species, we face the grotesque situation that we still do not know what is a species whose origin Darwin wanted to explain. A generally applicable species definition is not available. Is there a basic unit of biodiversity above the level of individuals? Do we try to define something that does not exist in reality? The strong potential for the evolution of genetic variability in parasites together with the importance of species diagnosis for applied fields of parasite research make biodiversity research a key role in parasitology. Frequent occurrence of sympatric speciation, clonal reproduction, selfing, sib mating or parthenogenesis imply exceptional conditions for the evolution of gene pool diversities in parasites.     

Does a polymorphic species have a ‘polymorphic’ diet? A case study from a lacertid lizard

Lizards are ideal for studying colour polymorphism, because some species are polymorphic and the morphs often have different ecological or reproductive strategies. We studied the feeding habits of six polymorphic populations of Podarcis muralis to test whether morphs differed in their diet. Some taxa were selected in a similar way by all morphs, but selection on other taxa varied and was characteristic of each morph. Diet was most different for the red and yellow morphs. Two hypotheses could explain these differences: active segregation in the trophic niche or active segregation in space dependent on spatial heterogeneity in prey availability. The former is improbable because P. muralis is considered an opportunistic feeder, whereas the latter could occur if the morphs adopted alternative territorial strategies with consequent spatial segregation.     

Is <Emphasis Type="Italic">Testudo werneri</Emphasis> a distinct species?

Sequence variation of a 1066 bp long mtDNA fragment (cytochrome b gene, adjacent part of tRNA-Thr gene) of four known-locality samples of Testudo kleinmanni (Tripolitania, Libya) and of four samples of T. werneri (Negev, Israel) is compared with additional five sequences of pet trade tortoises allegedly representing T. kleinmanni. Four haplotypes, differing in one to four mutation steps occur. The most common haplotype was shared by all known-locality samples of T. kleinmanni and three T. werneri. Sequence variation within each nominal species and in the pooled sample of T. kleinmanni, T. werneri and pet trade tortoises is the lowest known for any Testudo species. We conclude there is no support for the validity of T. werneri Perälä, 2001.     

What is a fish species?

The formal processes of alpha-taxonomy ensure that species have uniquenames and can be identified. No similar process is mandatory forinfraspecific variation, so the species is a uniquely importantpractical term. At present, there is little agreement of the definitionof a species. In the last 30 years, numerous concepts have beenproposed. The nature of fish species is reviewed. Clonal inheritance ofnuclear genes occurs in several lineages. Hybridization is frequent,often leading to introgression, which may lead to extinction of species.Species may have hybrid origins. There is good evidence for parallelspeciation in similar habitats. There are clearly exceptions to thecladistic assumption of dichotomous branching during speciation. Siblingspecies may exist with no discernible niche differentiation.Basic assumptions are violated for the recognition, phylogenetic,ecological and some formulations of the evolutionary species concepts.The most satisfactory definitions are two of the earliest proposed inthe light of evolutionary theory. The Darwinian view is that species arerecognizable entities which are not qualitatively distinct fromvarieties. A restatement of this concept in genetic terms provides ameans of dealing with all forms of species known in present-day fishes.This modified Darwinian concept is operated through the application offuzzy logic rather than rigid definition. This involves a search fordiscontinuities between species, rather than an a priori definition ofhow boundaries are to be determined. A subset of Darwinian species areMayrian or biological species, which are characterized by theirdemonstrable reproductive isolation from other species. The status of apopulation as a Mayrian species is a testable hypothesis. Moleculartechniques allow this hypothesis to be tested more easily thanpreviously, at least when dealing with sympatric populations.     

Two new species of Dacne Latreille (Coleoptera,Erotylidae) from China,with a key to Chinese species?and subspecies of Dacne

Two new species Dacne (Xenodacne) tangliangi sp. n. andDacne (Xenodacne) hujiayaoi sp. n. are described from China. A key to Chinese species and subspecies of genus Dacne Latreille is provided.     

Conservation genetic assessment of four plant species in a small replica of a steppe ecosystem &gt;30 years after establishment

To counter species loss living ex situ collections in botanic gardens became important elements of robust conservation programs. Several limitations, problems, and risks associated with living ex situ collections have been reported such as appropriate cultivation management to maintain genetic diversity and stochastic effects in small isolated populations in artificial habitats. However, not all small and isolated populations exhibit these predicted genetic changes. In a multi-species in situ/ex situ comparison of sand dune steppe- and grassland vegetation >30 years after the ex situ population establishment, we compared four different species’ population genetic diversities (Alyssum montanum ssp. gmelinii, Gypsophila fastigiata, Helianthemum nummularium ssp. obscurum, Onosma arenaria) by means of ISSR. We observed different species-specific genetic responses to quite similar abiotic selective forces concerning different neutral genetic diversities of wild versus botanic garden populations. The genetic divergence was kept relatively low in two of the four investigated species between the model steppe plant community within the botanic garden where human interference was kept at a minimum and the wild population. However, the moderate genetic divergence of the two other species kept under the same conditions highlights the importance of species-specific intrinsic responses and stochastic effects to ecosystem changes and provides data on population genetic dynamics in small and isolated populations. This contributes to further improve recommendations on how to best conserve endangered plant species in ex situ environments (cultivation in near nature-like replicas of the original site with as little human inference as possible over only certain periods of time, >30 years).     

Why does the unimodal species richness–productivity relationship not apply to woody species: a lack of clonality or a legacy of tropical evolutionary history?

Aim  To study how differences in species richness patterns of woody and herbaceous plants may be influenced by ecological and evolutionary factors. Unimodal species richness–productivity relationships (SRPRs) have been of interest to ecologists since they were first described three decades ago for British herbaceous vegetation by J. P. Grime. The decrease in richness at high productivity may be due to competitive exclusion of subordinate species, or diverse factors related to evolution and dispersal. Unimodal SRPRs are most often reported for plants, but there are exceptions. For example, unimodal SRPRs are common in the temperate zone but not in the tropics. Similarly, woody species and forest communities in the Northern Hemisphere do not tend to show unimodal SRPRs.
Location  Global.
Methods  We used data from the literature to test whether a unimodal SRPR applies to woody species and forest communities on a global scale. We explored whether the shape of SRPRs may be related to the lack of clonality in woody species (which may prevent their being competitively superior), or the legacy of evolutionary history (most temperate woody species originate from tropical lineages, and due to niche conservatism they may still demonstrate 'tropical patterns'). We used case studies that reported the names of the dominant or most abundant species for productive sites.
Results  Woody species were indeed less clonal than herbaceous species. Both clonality and the temperate evolutionary background of dominating species were associated with unimodality in SRPRs, with woodiness modifying the clonality effect.
Main conclusions  The unimodal SRPR has been common in the ecological literature because most such studies originate from temperate herbaceous communities with many clonal species. Consequently, both evolutionary and ecological factors may influence species richness patterns.     

Description of a new species of Calliostoma (Gastropoda,Calliostomatidae) from Southeastern?Brazil

Calliostoma tupinamba isa new species from Southeastern Brazil, ranging from southern Rio de Janeiro to northern São Paulo, and found only on coastal islands, on rocks and sessile invertebrates at 3 to 5 meters of depth. Shell and soft part morphology is described here in detail. Calliostoma tupinamba is mainly characterized by a depressed trochoid shell; eight slightly convex whorls; a sharply suprasutural carina starting on the third whorl and forming a peripheral rounded keel; and a whitish, funnel-shaped and deep umbilicus, measuring about 5%–10% of maximum shell width. Calliostoma tupinamba resembles Calliostoma bullisi Clench & Turner, 1960 in shape, but differs from it in being taller and wider, having a smaller umbilicus and lacking a strong and large innermost spiral cord at its base. Finally, an identification key of Brazilian Calliostoma species is presented.     

What makes a species central in a cleaning mutualism network?

Mutualisms often form networks of interacting species, characterized by the existence of a central core of species that potentially drive the ecology and the evolution of the whole community. Centrality measures allow quantification of how central or peripheral a species is within a network, thus informing about the role of each species in network organization, dynamics, and stability. In the present study we addressed the question whether the structural position of species in the network (i.e. their topological importance) relates to their ecological traits. We studied interactions between cleaner and client reef fishes to identify central and peripheral species within a mutualistic network, and investigated five ecological correlates. We used three measures to estimate the level of centrality of a species for distinct structural patterns, such as the number of interactions and the structural proximity to other species. Through the use of a principal component analysis (PCA) we observed that the centrality measures were highly correlated (92.5%) in the studied network, which indicates that the same species plays a similar role for the different structural patterns. Three cleaner and ten client species had positive values of centrality, which suggests that these species are modulating ecological and evolutionary dynamics within the network. Higher centralities were related to higher abundances and feeding habits for client fishes, but not for cleaners. The high correlation between centrality measures in the present study is likely related to the nested structure of the cleaning network. The cleaner species’ set, by having central species that are not necessarily the most abundant ones, bears potentially more vulnerable points for network cohesiveness. Additionally, the present study generalizes previous findings for plant–animal mutualisms, as it shows that the structure of marine mutualisms is also related to a complex interplay between abundance and niche‐related features.     

What is a species? Essences and generation

Arguments against essentialism in biology rely strongly on a claim that modern biology abandoned Aristotle’s notion of a species as a class of necessary and sufficient properties. However, neither his theory of essentialism, nor his logical definition of species and genus (eidos and genos) play much of a role in biological research and taxonomy, including his own. The objections to natural kinds thinking by early twentieth century biologists wrestling with the new genetics overlooked the fact that species have typical developmental cycles and most have a large shared genetic component. These are the “what-it-is-to-be” members of that species. An intrinsic biological essentialism does not commit us to Aristotelian notions, nor even modern notions, of essence. There is a long-standing definition of “species” and its precursor notions that goes back to the Greeks, and which Darwin and pretty well all biologists since him share, that I call the Generative Conception of Species. It relies on there being a shared generative power that makes progeny resemble parents. The “what-it-is-to-be” a member of that species is that developmental type, mistakes in development notwithstanding. Moreover, such “essences” have always been understood to include deviations from the type. Finally, I shall examine some implications of the collapse of the narrative about essences in biology.     

First human-caused extinction of a cetacean species?

The Yangtze River dolphin or baiji (Lipotes vexillifer), an obligate freshwater odontocete known only from the middle-lower Yangtze River system and neighbouring Qiantang River in eastern China, has long been recognized as one of the world's rarest and most threatened mammal species. The status of the baiji has not been investigated since the late 1990s, when the surviving population was estimated to be as low as 13 individuals. An intensive six-week multi-vessel visual and acoustic survey carried out in November-December 2006, covering the entire historical range of the baiji in the main Yangtze channel, failed to find any evidence that the species survives. We are forced to conclude that the baiji is now likely to be extinct, probably due to unsustainable by-catch in local fisheries. This represents the first global extinction of a large vertebrate for over 50 years, only the fourth disappearance of an entire mammal family since AD 1500, and the first cetacean species to be driven to extinction by human activity. Immediate and extreme measures may be necessary to prevent the extinction of other endangered cetaceans, including the sympatric Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis).     

A re-consideration of the taxonomic status of Nebria lacustris Casey (Coleoptera,Carabidae, Nebriini) based on multiple datasets – a single species or a species complex?

This study gathered evidence from principal component analysis (PCA) of morphometric data and molecular analyses of nucleotide sequence data for four nuclear genes (28S, TpI, CAD1, and Wg) and two mitochondrial genes (COI and 16S), using parsimony, maximum likelihood, and Bayesian methods. This evidence was combined with morphological and chorological data to re-evaluate the taxonomic status of Nebria lacustris Casey sensu lato. PCA demonstrated that both body size and one conspicuous aspect of pronotal shape vary simultaneously with elevation, latitude, and longitude and served to distinguish populations from the southern Appalachian highlands, south of the French Broad, from all other populations. Molecular analyses revealed surprisingly low overall genetic diversity within Nebria lacustris sensu lato, with only 0.39% of 4605 bp varied in the concatenated dataset. Evaluation of patterns observed in morphological and genetic variation and distribution led to the following taxonomic conclusions: (1) Nebria lacustris Casey and Nebria bellorum Kavanaugh should be considered distinct species, which is a NEW STATUS for Nebria bellorum. (2) No other distinct taxonomic subunits could be distinguished with the evidence at hand, but samples from northeastern Iowa, in part of the region known as the "Driftless Zone", have unique genetic markers for two genes that hint at descent from a local population surviving at least the last glacial advance. (3) No morphometric or molecular evidence supports taxonomic distinction between lowland populations on the shores of Lake Champlain and upland populations in the adjacent Green Mountains of Vermont, despite evident size and pronotal shape differences between many of their members.     

How many species are infected with Wolbachia? – a statistical analysis of current data

Wolbachia are intracellular bacteria found in many species of arthropods and nematodes. They manipulate the reproduction of their arthropod hosts in various ways, may play a role in host speciation and have potential applications in biological pest control. Estimates suggest that at least 20% of all insect species are infected with Wolbachia . These estimates result from several Wolbachia screenings in which numerous species were tested for infection; however, tests were mostly performed on only one to two individuals per species. The actual percent of species infected will depend on the distribution of infection frequencies among species. We present a meta-analysis that estimates percentage of infected species based on data on the distribution of infection levels among species. We used a beta-binomial model that describes the distribution of infection frequencies of Wolbachia , shedding light on the overall infection rate as well as on the infection frequency within species. Our main findings are that (1) the proportion of Wolbachia -infected species is estimated to be 66%, and that (2) within species the infection frequency follows a 'most-or-few' infection pattern in a sense that the Wolbachia infection frequency within one species is typically either very high (>90%) or very low (<10%).     

How many species of host-specific insects feed on a species of tropical tree?

The assumptions on the host specificity of beetles that led Terry Erwin to suggest that there may be over 30 million arthropod species were tested for 10 species of trees and their insect associates at a rainforest site in Papua New Guinea. The data included 391 species and 4696 individuals of herbivorous beetles collected during a one year period using hand collecting, beating, branch clipping, intercept flight traps and pyrethrum knockdown. Insect host specificity was assessed by feeding trials in captivity. The data suggest that between 23 and 37 monophagous leaf-feeding species are most likely to be present in this system, whereas Erwin's method yields an estimate of 138 monophagous species. The major factors responsible for the discrepancy between our observations and Erwin's assumptions appears to be (a) the importance of transient species; (b) the insect fauna that is shared among tree species; (c) some generalist wood-eating species may inflate the apparent species richness of leaf-feeding beetles; and (d) the proportion of specialist species varies significantly among tree species. We conclude that studies reporting the proportion of specialist insect herbivores associated with particular tropical tree species will yield only a portion of the information needed to estimate global arthropod species richness, but may be useful for elucidating certain aspects of food-web ecology in tropical rain forests.     

Pinguicula rotundiflora—a new species from Mexico

Pinguicula rotundiflora (Lentibulariaceae), a new species from southern Mexico related toP. parvifolia Robinson is described and illustrated.     

Is the originality of a species measurable?

In this paper, we introduce the concept of 'originality of a species within a set' in order to indicate the average rarity of all the features belonging to this species. Using a phylogenetic tree of 70 species of New World terrestrial Carnivora, we suggest measuring the originality by a probability distribution. This maximizes the expected number of features shared by two species randomly drawn from the set. By using this new index, we take account of branch lengths whereas current indices of originality focus on tree topology. As a supplement to Nee and May's optimizing algorithm, we find that originality must be one of the criteria used in conservation planning.     

Is Karenia brevis really a low-light-adapted species?

Despite nearly annual blooms of the neurotoxic dinoflagellate Karenia brevis (Davis) G. Hansen and Moestrup in the Gulf of Mexico, defining the suite of biological traits that explain its proliferation has remained challenging. Studies have described K. brevis as a low-light-adapted species, incapable of sustaining growth under high light, which is at odds with observed surface aggregations sometimes within centimeters of the sea surface and also with short-term experiments showing photosynthetic machinery accommodating high irradiances. Here, growth and photophysiology of three K. brevis isolates were evaluated under a range of environmentally relevant irradiances (10–1500 μmol photons m⁻² s⁻¹) in the laboratory. No differences in growth–irradiance curves were observed among isolates; all sustained maximum growth rates at the highest irradiances examined, even in exposures as long as three weeks. The growth efficiency α of K. brevis under light-limiting conditions appeared mediocre among dinoflagellates, and poorer than that of other phytoplankton (e.g., diatoms, cyanobacteria), implying that K. brevis is not a low-light specialist. This finding substantially alters earlier parameterizations of K. brevis growth–irradiance curves. Therefore, a model was developed to contextualize how these new growth–irradiance curves might affect bottom growth rates. This model was subsequently applied to a case study comparing seasonal light forcing offshore of Pinellas County, FL, USA, with a single empirical value for light attenuation, and seasonal bottom water temperatures. Predictions suggested that light may limit bottom growth as close as 1 km from shore in winter, but would only begin limiting growth 20 km from shore in summer. Population maintenance (no net growth) was possible as far offshore as 90 km in summer and 68 km in winter. These ranges intercept areas thought to be important for bloom initiation.