Can Invasive Species Facilitate Native Species? Evidence of How, When, and Why These Impacts Occur

Although the predatory and competitive impacts of biological invasions are well documented, facilitation of native species by non-indigenous species is frequently overlooked. A search through recent ecological literature found that facilitative interactions between invasive and native species occur in a wide range of habitats, can have cascading effects across trophic levels, can re-structure communities, and can lead to evolutionary changes. These are critical findings that, until now, have been mostly absent from analyses of ecological impacts of biological invasions. Here I present evidence for several mechanisms that exemplify how exotic species can facilitate native species. These mechanisms include habitat modification, trophic subsidy, pollination, competitive release, and predatory release. Habitat modification is the most frequently documented mechanism, reflecting the drastic changes generated by the invasion of functionally novel habitat engineers. Further, I predict that facilitative impacts on native species will be most likely when invasive species provide a limiting resource, increase habitat complexity, functionally replace a native species, or ameliorate predation or competition. Finally, three types of facilitation (novel, substitutive, and indirect) define why exotic species can lead to facilitation of native species. It is evident that understanding biological invasions at the community and ecosystem levels will be more accurate if we integrate facilitative interactions into future ecological research. Since facilitative impacts of biological invasions can occur with native endangered species, and can have wide-ranging impacts, these results also have important implications for management, eradication, and restoration.Contribution Number 2293, Bodega Marine Laboratory, University of California at Davis.     

Species–area relationships in the Hantam-Tanqua-Roggeveld,Succulent Karoo,South Africa

The Hantam-Tanqua-Roggeveld subregion is part of the Succulent Karoo hotspot of biodiversity which stretches along the southwestern side of South Africa and Namibia. Forty Whittaker plots were surveyed in the spring of 2005, in eight vegetation associations, to gather diversity data for the Hantam, Tanqua Karoo and Roggeveld areas. Seven plot sizes were used to construct species–area curves using three different models namely: the untransformed linear function, the power function and the exponential function. In general, the power and exponential functions produced a more significant fit to the data than the untransformed linear function. Linear regressions using environmental parameters indicated that altitude, mean annual precipitation and mean annual temperature were significant predictors of species richness at the 1, 10, 100 and 1000 m² scales. To illustrate the variation in species–area curves and species richness across the landscape, a transect through the study area is discussed. The transect stretches eastwards from the Tanqua Karoo across the escarpment into the Roggeveld and crosses five different vegetation associations. Differences between associations were found in species richness in the 1000 m² plots. Each association also produced species–area curves with their own characteristics. Slope values for the samples within an association did not differ significantly, although the intercept value often did. Comparisons between associations along the transect revealed significant differences in the slope value between the associations, except for the Dicerothamnus rhinocerotis Mountain Renosterveld which did not differ significantly from the associations bordering it on either side.     

Cryptic Diversity in the Ubiquist Species Parisotoma notabilis (Collembola,Isotomidae): A Long-Used Chimeric Species?

Parisotoma notabilis is the most common species of Collembola in Europe and is currently designated as ubiquist. This species has been extensively used in numerous studies and is considered as well characterized on a morphological ground. Despite the homogeneity of its morphology, the sequencing of the barcoding fragment (5′ end of COI) for several populations throughout Europe and North America revealed four distinct genetic lineages. The divergence found between these lineages was similar to the genetic distance among other species of the genus Parisotoma included in the analysis. All four lineages have been confirmed by the nuclear gene 28S. This congruence between mitochondrial and nuclear signals, as well as the geographical distribution pattern of lineages observed in Europe, supports the potential specific status of these lineages. Based on specimens from the type locality (Hamburg), the species name was successfully assigned to one of these lineages. This finding raises several problems as Parisotoma notabilis has been widely used in many ecological studies. Accumulation of new data for the different lineages detected, especially ecological information and life history traits, is needed to help resolve this situation.     

Is Tree Species Diversity or Species Identity the More Important Driver of Soil Carbon Stocks,C/N Ratio,and pH?

We explored tree species diversity effects on soil C stock, C/N ratio, and pH as compared with effects of tree species identity. We sampled forest floors and mineral soil (0–40 cm) in a diversity gradient of 1–5 tree species composed of conifers and broadleaves in Bia?owie?a Forest, Poland. Diversity was a weaker driver than identity of soil C stocks, C/N ratio, and pH in the soil profile. However, there were significant non-additive effects of diversity and significant effects of identity on C stock and C/N ratio within different parts of the soil profile. More diverse forests had higher C stocks and C/N ratios in the 20–40 cm layer, whereas identity in terms of conifer proportion increased C stocks and C/N ratios only in forest floors. A positive relationship between C stocks and root biomass in the 30–40 cm layer suggested that belowground niche complementarity could be a driving mechanism for higher root carbon input and in turn a deeper distribution of C in diverse forests. Diversity and identity affected soil pH in topsoil with positive and negative impacts, respectively. More diverse forests would lead to higher soil nutrient status as reflected by higher topsoil pH, but there was a slight negative effect on N status as indicated by higher C/N ratios in the deeper layers. We conclude that tree species diversity increases soil C stocks and nutrient status to some extent, but tree species identity is a stronger driver of the studied soil properties, particularly in the topsoil.     

A New Deep-Sea Species of Chaetognaths,Eukrohnia geptneri,from the Northwestern Pacific—A Supposed Ancestor of the Antarctic Species Eukrohnia bathyantarctica

A new deep-sea species of chaetognaths, Eukrohnia geptneri, from the Northwestern Pacific is described; the young were registered in the epipelagic zone, while the adult specimens were found in deep depths of the Japanese Depression. Morphologically, this species is close to E. bathyantarctic; however, it differs from the latter in a series of characteristics. The diagnosis of the new species, drawings, and identification keys for the world fauna of the genus Eukrohniaare presented. A hypothesis is proposed on the origin of bathypelagic species inhabiting Antarctic waters, the chaetognath Eukrohnia bathyantarcticaDavid, 1958, from the species E. geptnerisp. nov.     

New Species of Meconopsis （Papaveraceae） from Mianning,Southwestern Sichuan,China

Two new species of Meconopsis, M.pulchella and M.heterandra are described and characterized. Differences with similar species are discussed and photos showing the diagnostic features are provided.     

An Inordinate Fondness? The Number,Distributions, and Origins of Diatom Species

The number of extant species of diatoms is estimated here to be at least 30,000 and probably ca. 100,000, by extrapolation from an eclectic sample of genera and species complexes. Available data, although few, indicate that the pseudocryptic species being discovered in many genera are not functionally equivalent. Molecular sequence data show that some diatom species are ubiquitously dispersed. A good case can be made that at least some diatom species and even a few genera are endemics, but many such claims are still weak. The combination of very large species numbers and relatively rapid dispersal in diatoms is inconsistent with some versions of the “ubiquity hypothesis” of protist biogeography, and appears paradoxical. However, population genetic data indicate geographical structure in all the (few) marine and freshwater species that have been examined in detail, sometimes over distances of a few tens of kilometres. The mode of speciation may often be parapatric, in the context of a constantly shifting mosaic of temporarily isolated (meta) populations, but if our “intermediate dispersal hypothesis” is true (that long‐distance dispersal is rare, but not extremely rare), allopatric speciation could also be maximized.     

Two new Species of Lasiohelea from Sichuan,China(Diptera,Ceratopogonidae)

1. Lasiohelea aeschrodenta, sp. nov Female Head with eyes bare, AR 2.09;maxillary palp with a sensory pore on segment 3. Buccal armature has about 10 teeth which separated irregulary in the cibarium;clypeus with about 16 setae. Wing about 0.86 mm. long, with bare areas along veins. TR 1.74 in hind leg, with narrow scales on each tarsus. Spermatheca round and small, with abroad basical pore. Holotype:♀ Dukou, Sichuan, 1979 X. 10-11; Paratypes: 2♀♀Sichuan,Xichang, 1979 X. 5.     

A New Species of the GenusThermophis （Serpentes：Colubridae） from Shangri-La,Northern Yunnan,China, with a Proposal for an Eclectic Rule for Species Delimitation

The hot-spring snakes,Thermophis, were previously known only from the Tibet Autonomous Region and Western Sichuan, China. During the past two years, three adult hot-spring snakes （2 females, 1 male） were sampled in Shangri-La, northern Yunnan, China, thus expanding their known distribution region towards the southeast. This site is the southeastern-most corner of the Tibetan Plateau and the southernmost tip of the Hengduan Mountains （Mts.）. Phylogenetic analysis of mitochondrial （mt） and nuclear （n） DNA segments suggested that the three specimens belong to the genus ofThermophis. Morphologically, the new species is more similar toT. zhaoermii. However, it is distinguished fromT.zhaoermiiin the number of maxillary teeth （15）, distance between the two eyes/head width, rostral width/height, mental width/height, in one character limited to female： head width/length, and in four characters restricted to male： occurrence of the reduction from 10 to 8 （8 to 6, 6 to 4） scales in each dorsal row on the tail. There are differences in morphology, genetics （mtDNA, nDNA）, and geography between the putative new species andT.zhaoermii,the new species meets our proposed eclectic and feasible ＂four-differences＂ rule.     

Predicting Species Numbers Using Species–Area and Endemics–Area Relations

Current ecological theory predicts an allometric relation between the number of species with restricted range size (endemics) and area (the endemics–area relation EAR), a pattern similar to the common species–area relation (SAR). Using SARs and EARs we can estimate species loss after habitat loss. A comparison of the predictive power of both approaches (using a patch occupancy model and data from European butterflies) revealed that the EAR approach is less reliable than the SAR. Contrary to current theory it appeared that EARs are relations in their own right that describe spatial distributions of endemic species. They do not simply follow from the underlying SAR. The implications of these results for the applicability of SARs and EARs in biodiversity forecasting are discussed.     

New Species of Meconopsis （Papaveraceae） from Balang Shan, Western Sichuan, China

A new species with two varieties,Meconopsis balangensis varieties balangensis and atrata (Papaveraceae),is described and characterized.Differences separating it from similar species are discussed and photos showing the diagnostic features are provided.     

Species–soil associations, disturbance, and nutrient cycling in an Australian tropical rainforest

Resource availability and disturbance are important factors that shape the composition, structure, and functioning of ecosystems. We investigated the effects of soil fertility and disturbance on plant–soil interactions and nutrient cycling in a diverse tropical rainforest. Our goal was to determine how common soil specialisation is among species and how plant–soil interactions affect ecosystem functioning in the presence of disturbance. Most species (59%) showed significant fidelity to either fertile (basalt) or infertile (schist) soils. Obligate schist specialists (six species) contributed 39 and 37% to total stand-level basal area and aboveground net primary productivity, respectively. High nutrient use efficiency of schist specialists reduced the rates of within-stand nutrient cycling through the production of nutrient-poor plant tissues and litter. Although forests on schist soils had higher basal area and similar rates of productivity to forests on basalt, uptake of Mg, K, P, and N were markedly less on schist than on basalt, particularly after a cyclone disturbance. Stands on schist soils were also less affected by the cyclone and, as a result, contributed less (ca. 50%) Mg, K, P, and N inputs to the forest floor (via litterfall) than stands on basalt soils. System “openness” (i.e. the risk of nutrient loss) from cyclone-affected basalt forests was minimised by high rates of uptake following disturbance and large effective cation exchange capacities of soils. Soil–plant-disturbance interactions are likely to engender different fitness-enhancing strategies on fertile and infertile soils, possibly leading to the development and/or maintenance of diversity in rainforests.     

Buffon, Darwin, and the Non-Individuality of Species – A Reply to Jean Gayon

Gayon's recent claim that Buffon developed a concept of species as physical individuals is critically examined and rejected. Also critically examined and rejected is Gayon's more central thesis that as a consequence of his analysis of Buffon's species concept, and also of Darwin's species concept, it is clear that modern evolutionary theory does not require species to be physical individuals. While I agree with Gayon's conclusion that modern evolutionary theory does not require species to be physical individuals, I disagree with his reasons and instead provide logical rather than historical reasons for the same conclusion.     

Three new Species of Tabanidae from Sichuan,China (Diptera)

This report discribes 2 new species of Haematopota, 1 new species of Tabanus and 2 males of T. omeishanensis Xu, and T. liangshanensis Xu. All the types are deposited in the Institute of Microbiology & Epidemiology, Academy of Military Medical Sciences, P.L.A., China. Haematopota erlangshanensis, sp. nov. (fig. 1; 2—2) This species is related to H. hakusanensis Togashi, but is easily     

Species richness in agamid lizards: chance,body size,sexual selection or ecology?

Why does species richness vary so greatly across lineages? Traditionally, variation in species richness has been attributed to deterministic processes, although it is equally plausible that it may result from purely stochastic processes. We show that, based on the best available phylogenetic hypothesis, the pattern of cladogenesis among agamid lizards is not consistent with a random model, with some lineages having more species, and others fewer species, than expected by chance. We then use phylogenetic comparative methods to test six types of deterministic explanation for variation in species richness: body size, life history, sexual selection, ecological generalism, range size and latitude. Of eight variables we tested, only sexual size dimorphism and sexual dichromatism predicted species richness. Increases in species richness are associated with increases in sexual dichromatism but reductions in sexual size dimorphism. Consistent with recent comparative studies, we find no evidence that species richness is associated with small body size or high fecundity. Equally, we find no evidence that species richness covaries with ecological generalism, latitude or range size.     

Selected Species of the Genus Phellinus – Chemical Composition,Biological Activity,and Medicinal Applications

This study presents the current knowledge on chemical composition, biological activity, and possible medicinal applications of Phellinus igniarius, Phellinus pini, Phellinus pomaceus, and Phellinus robustus. These inedible arboreal species are phytopathogens that cause the enzymatic decomposition of wood. These species belong to the medicinal mushrooms and have been known for centuries in the traditional medicine of the Far East. They have been used as an effective remedy for stomach and intestinal ailments, diarrhea, and hemorrhages. Mycochemical studies have proved the presence of polysaccharides, phenolic compounds, and terpenoids. These compounds show biological activities such as anticancer, antioxidant, antiangiogenic, and antiviral. Research studies conducted using modern analytical methods have advanced the knowledge on the potential therapeutic use of compounds isolated not only from the fruiting bodies but also from biomass obtained with in vitro biotechnological methods.     

Species richness among birds: body size,life history,sexual selection or ecology?

Why do some avian families contain so many more species than other families? We use comparisons between sister taxa to test predictions arising from six explanations to this puzzle: that differences between families are due to chance, body size, life history, sexual selection, intrinsic ecological factors or extrinsic abiotic factors, respectively. In agreement with previous analyses, we find no support for the idea that differences in species richness are simply due to chance. However, contrary to most previous work, we also find no support for the hypotheses that high species richness is correlated with small body size and fast life history. Rather, high species diversity is strongly associated with pronounced plumage dichromatism, generalist feeding habits and good dispersal capabilities as well as large and fragmented geographical ranges. In addition, all of these relationships are robust to the removal of the two most speciose avian lineages, the Ciconiiformes and the Passeriformes. The supposed relationships between species richness and both body size and life history are, however, due to phylogenetic non-independence. Together with previous work showing that differences between avian lineages in extinction risk are associated with variation in body size and life history, these results indicate that extinction rates and speciation rates are not necessarily determined by the same factors. Hence, high extinction rates are not inevitably associated with low speciation rates. Extinction-prone lineages may, in fact, have a high rate of speciation. In such lineages a high proportion of ''vulnerable'' species would be a natural, ongoing phenomenon.     

Are ectoparasite communities structured? Species co-occurrence, temporal variation and null models

1. We studied temporal variation in the structure of flea communities on small mammalian hosts from eastern Slovakia using null models. We asked (a) whether flea co-occurrences in infracommunities (in the individual hosts) in different hosts as well as in the component communities (in the host species) demonstrate a non-random pattern; (b) whether this pattern is indicative of either positive or negative flea species interactions; (c) whether this pattern varies temporally; and (d) whether the expression of this pattern is related to population size of either fleas or hosts or both. 2. We constructed a presence/absence matrix of flea species for each temporal sample of a host species and calculated four metrics of co-occurrence, namely the C-score, the number of checkerboard species pairs, the number of species combinations and the variance ratio (V-ratio). Then we compared these metrics with the respective indices calculated for 5000 null matrices that were assembled randomly using two algorithms, namely fixed-fixed (FF) and fixed-equiprobable (FE). 3. Most co-occurrence metrics calculated for real data did not differ significantly from the metrics calculated for simulated matrices using the FF algorithm. However, the indices observed for 42 of 75 presence/absence matrices differed significantly from the null expectations for the FE models. Non-randomness was detected mainly by the C-score and V-ratio metrics. In all cases, the direction of non-randomness was the same, namely the aggregation, not competition, of flea species in host individuals and host species. 4. The inclusion or exclusion of the uninfested hosts in the FE models did not affect the results for individual host species. However, exclusion of the uninfested host species led to the acceptance of the null hypothesis for only six of 13 temporal samples of the component flea communities for which non-randomness was detected when the uninfested hosts were included in the analysis. 5. In most host species, the absolute values of the standardized size effect of both the C-score and V-ratio increased with an increase in host density and a concomitant decrease in flea abundance and prevalence. 6. Results of this study demonstrated that (a) flea assemblages on small mammalian hosts were structured at some times, whereas they appeared to be randomly assembled at other times; (b) whenever non-randomness of flea co-occurrences was detected, it suggested aggregation but never segregation of flea species in host individuals or populations; and (c) the expression of structure in flea assemblages depended on the level of density of both fleas and hosts.