Phytoplankton response to light and internal phosphorus loading from sediment release

1. A 2 × 2 factorial design was employed to look at the influence of two levels of phosphorus (P; high and low) and two levels of light (high and low) and their interactions, on phytoplankton abundance, elemental tissue composition and community structure in two seasons (April and June) of 2005. 2. A novel feature of the experiment was the creation of high and low P levels by manipulating sediment core conditions in the laboratory. Sediment cores were incubated with their associated overlaying water column from four different sites in Mona Lake, Michigan, under anaerobic or aerobic conditions, respectively. 3. After 24 days, the water overlaying the sediment cores was collected and used as growth media for phytoplankton collected from Mona Lake. Phytoplankton communities were grown in the laboratory in the high or low P water, and subjected to high (250 μmol m^?2 s^?1) or low (10 μmol m^?2 s^?1) light for 9 (April) or 14 (June) days. 4. In the April experiment, high P treatments resulted in significantly higher chlorophyll‐a concentrations, significantly lower C : P ratios from two of the four sites, and greater dominance by Scenedesmus at all sites relative to low P treatments. High light generally led to higher chlorophyll‐a concentrations, higher C : P ratios and greater Scenedesmus and Fragilaria biovolume at all sites. A significant interaction was measured between P and light for chlorophyll‐a and Scenedesmus biovolume, suggesting the influence of P was more apparent at high light than at low light levels. 5. In the June experiment, high P increased ash‐free dry mass (AFDM), lowered C : P ratios and resulted in increased Pediastrum biovolume. High light levels led to greater chlorophyll‐a concentrations, AFDM and C : P ratios, as well as increased biovolumes of Scendesmus, Pediastrum and Fragilaria. A significant interaction was found between P and light for all three taxa, as the positive influence of P was more pronounced at high light levels. 6. The results of our study demonstrate that sediment‐derived P stimulates phytoplankton growth, but that its effect on phytoplankton dynamics is modulated by other factors, such as light.     

Morphological differences between larvae and in vitro-cultured adults of Anisakis simplex (sensu stricto) and Anisakis pegreffii (Nematoda: Anisakidae)

Proper identification of Anisakis species infecting host fishes is very important to both human health and fish disease diagnosis. The foremost problem in the identification of Anisakis larvae in fishes is that L3 larvae cannot be easily differentiated morphologically, especially between A. simplex (sensu stricto) (s.s.) (Rudolphi, 1809) and A. pegreffii Campana-Rouget et Biocca, 1955. Instead, molecular means such as allozyme, mitochondrial DNA (mtDNA) cox2 region and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses had been successfully used. In this study, morphological differences of L3 larvae collected from fishes and in vitro-cultured L4 larvae and adult A. simplex (s.s.) and A. pegreffii were evaluated. Anisakis larvae were collected from 7 different host fishes within Japan. Undamaged A. simplex (s.s.) and A. pegreffii collected from Oncorhynchus keta (Walbaum) and Scomber japonicus Houttuyn, respectively, were used for in vitro-culture in order to obtain L4 and adult stages. Species identification was confirmed by PCR-RFLP analysis of the ITS region (ITS1-5.8S-ITS2) of ribosomal DNA and by mtDNA cox2 gene sequencing. Results revealed that L3, L4 and adult stages of A. simplex (s.s.) and A. pegreffii are morphologically distinguishable based on ventriculus length, wherein the former has longer ventriculus (0.90–1.50 mm) than the latter (0.50–0.78 mm). For oesophagus/ventriculus ratio, these two species are distinguishable only during L4 and adult stages. Also, adult male A. simplex (s.s.) and A. pegreffii were found to be distinguishable by differences in the distribution pattern of the caudal papillae, particularly the 3rd pair of distal papillae.     

Sex allocation according to multiple sexually dimorphic traits of both parents in the barn swallow (Hirundo rustica)

Parents should differentially invest in sons or daughters depending on the sex‐specific fitness returns from male and female offspring. In species with sexually selected heritable male characters, highly ornamented fathers should overproduce sons, which will be more sexually attractive than sons of less ornamented fathers. Because of genetic correlations between the sexes, females that express traits which are under selection in males should also overproduce sons. However, sex allocation strategies may consist in reaction norms leading to spatiotemporal variation in the association between offspring sex ratio (SR) and parental phenotype. We analysed offspring SR in barn swallows (Hirundo rustica) over 8 years in relation to two sexually dimorphic traits: tail length and melanin‐based ventral plumage coloration. The proportion of sons increased with maternal plumage darkness and paternal tail length, consistently with sexual dimorphism in these traits. The size of the effect of these parental traits on SR was large compared to other studies of offspring SR in birds. Barn swallows thus manipulate offspring SR to overproduce ‘sexy sons’ and potentially to mitigate the costs of intralocus sexually antagonistic selection. Interannual variation in the relationships between offspring SR and parental traits was observed which may suggest phenotypic plasticity in sex allocation and provides a proximate explanation for inconsistent results of studies of sex allocation in relation to sexual ornamentation in birds.     

On the systematic position of the family Gyrinidae (Coleoptera: Adephaga)

Various characters of adult and larval members of Adephaga and Cupedidae were analyzed, and suggest that Gyrinidae are the sister-group of the remaining Adephaga, and are not closely related to the remaining aquatic Adephaga. The aquatic families Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae seem to form a well founded monophyletic unit. The following characters are considered as synapomorphies of Adephaga excluding Gyrinidae: bifurcate condition of the muscle (= M.) tentoriopraementalis inferior, reduction of hypopharynx, strongly developed prosternal process, reduction in size and specialized modification of the ventral sclerite of the mesothorax, strongly developed mesofurcal arms, a high mesopleural ridge, globular mesocoxae restricted to rotatory movements, invaginated sternum VIII (coxostemum), the strongly curved base of the median lobe of the aedeagus, which articulates with the parameres, the rotated position of the aedeagus in repose, fusion of the larval clypeolabrum with the frons and reduction of the larval lacinia. Mesal shifting of M. episterno-coxalis prothoracis, and the fusion of the apical portions of the malpighian tubules of either side are considered as synapomorphies of Adephaga excluding Rhysodidae and Gyrinidae. Lateral reduction of the meta “sternal” transverse ridge and the presence of the subcubital setal binding patch of the hind wing are considered as synapomorphic characters of Trachypachidae, Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae. We postulate that the metacoxal fusion occurred independently in gyrmids and the common ancestor of Trachypachidae, Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae. Consequently we consider this character state as another synapomorphy of Trachypachidae and Hydradephaga excluding Haliplidae and Gyrinidae. The following characters are considered as synapomorphies of Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae: Loss of tactile setae on the head capsule, metafurcal origin on the intercoxal wall, expansion of the intercoxal wall, elongation of the subcubital setal binding patch, loss of Mm. furca-coxale anterior and posterior, reduction of the larval abdominal segments IX and X, and the shifting of the uropmphi onto the ventral side of segment VIII. Presence of M. tentorio-mandibularis and M. stipitopalpalis intemus are certainly primitive features of adult gyrinids but the distribution of these character states among most members of Adephaga is yet unclear. Chemical defence gland constituents point towards a very isolated position of Gyrinidae. The old age of the group, documented by a larva found in upper Permian deposits, may support the hypothesis of a sister-group relation-ship between Gyrinidae and the remainder of Adephaga.     

长白山多孔菌物种多样性、区系组成及分布特征

多孔菌是木材腐朽真菌的一个重要类群,通过将木材中的纤维素、半纤维素和木质素分解成为可被自身和其他生物利用的营养物质,从而促进森林生态系统中的物质循环.经过十几年的考察和采集,发现长白山地区多孔菌物种多样性非常丰富,Shannon多样性指数达到5.06,共有246种,占中国多孔菌总数的40.7％,分别隶属于担子菌门6个目11个科80个属,其中优势科为多孔菌科.物种区系地理成分以北温带成分和世界广布成分为主,其他几种区系成分也有分布,具有明显的北温带成分区系特征.松属是长白山地区多孔菌最重要的寄主树木,该地区41.5％的多孔菌生长在松属上.该地区多孔菌主要营腐生生活,其数量与生长基质腐烂程度的相关系数达到了0.89,呈显著相关,对长白山森林生态系统的物质循环起着重要作用.长白山多孔菌物种保护程度比较高,其中稀有种和濒危种的数量均相对较多,濒危种18种,占到全国濒危种数量的37.5％.多孔菌除了在森林生态系统中发挥重要生态功能外,很多种类本身具有较高的经济价值.在保护好该生物类群的前提下,可以合理开发和利用这些宝贵的生物资源.     

Long-term temporal variation in the organization of an ant–plant network

Background and Aims

Functional groups of species interact and coevolve in space and time, forming complex networks of interacting species. A long-term study of temporal variation of an ant–plant network is presented with the aims of: (1) depicting its structural changes over a 20-year period; (2) detailing temporal variation in network topology, as revealed by nestedness and modularity analysis and other parameters (i.e. connectance, niche overlap); and (3) identifying long-term turnover in taxonomic structure (i.e. switches in ant resource use or plant visitor assemblages according to taxa).

Methods

Fieldwork was carried out at La Mancha, Mexico, and ant–plant interactions were observed between 1989 and 1991, between 1998 and 2000, and between May 2010 and 2011. Occurrences of ants on extrafloral nectaries (EFNs) were recorded. The resulting ant–plant networks were constructed from qualitative presence–absence data determined by a species–species matrix defined by the frequency of occurrence of each pairwise ant–plant interaction.

Key Results

Network variation across time was stable and a persistent nested structure may have contributed to the maintenance of resilient and species-rich communities. Modularity was lower than expected, especially in the most recent networks, indicating that the community exhibited high overlap among interacting species (e.g. few species were hubs in the more recent network, being partly responsible for the nested pattern). Structurally, the connections created among modules by super-generalists gave cohesion to subsets of species that otherwise would remain unconnected. This may have allowed an increasing cascade-effect of evolutionary events among modules. Mutualistic ant–plant interactions were structured 20 years ago mainly by the subdominant nectarivorous ant species Camponotus planatus and Crematogaster brevispinosa, which monopolized the best extrafloral nectar resources and out-competed other species with broader feeding habits. Through time, these ants, which are still present, lost their position as network hubs and diminished in their importance in structuring the network; simultaneously, plants gained in importance.

Conclusions

The long-term network analysis reveals a decrease in attended plant species richness, a notable increase in plant species participation from 1990 to 2010 (sustained by less plant taxonomic similarity in the older 1990 network), an increase in the number of ant species and a diminishing dominance of super-generalist ants. The structure of the community has remained highly nested and connected with low modularity, suggesting overall a more participative, homogeneous, cohesive interaction network. Although previous studies have suggested that interactions between ants and EFN-bearing plants are susceptible to seasonality, abiotic factors and perturbation, this cohesive structure appears to be the key for biodiversity and community maintenance.     

Taxonomic identification bias does not drive patterns of abundance and diversity in theropod dinosaurs

The ability of palaeontologists to correctly diagnose and classify new fossil species from incomplete morphological data is fundamental to our understanding of evolution. Different parts of the vertebrate skeleton have different likelihoods of fossil preservation and varying amounts of taxonomic information, which could bias our interpretations of fossil material. Substantial previous research has focused on the diversity and macroevolution of non-avian theropod dinosaurs. Theropods provide a rich dataset for analysis of the interactions between taxonomic diagnosability and fossil preservation. We use specimen data and formal taxonomic diagnoses to create a new metric, the Likelihood of Diagnosis, which quantifies the diagnostic likelihood of fossil species in relation to bone preservation potential. We use this to assess whether a taxonomic identification bias impacts the non-avian theropod fossil record. We find that the patterns of differential species abundance and clade diversity are not a consequence of their relative diagnosability. Although there are other factors that bias the theropod fossil record that are not investigated here, our results suggest that patterns of relative abundance and diversity for theropods might be more representative of Mesozoic ecology than often considered.     

Fruit type,life form and origin determine the success of woody plant invaders in an urban landscape

The spread of alien plant species is a critical ecological event worldwide, but the forces that control this spread are not well documented. Alien plant species are well known to disrupt ecological services of native ecosystems, change the composition of native habitats, and often lead to the extirpation of native flora and fauna. Here, we report on life history patterns of plant species with rapidly spreading and declining ranges in North America’s major urban region. We tested for differences in life history traits between the 466 native and alien woody flora of the New York metropolitan area. We also examined the relationship between life history traits and change in distribution in the New York metropolitan area between 1900 and 2000. Native and alien species of the New York metropolitan area differ with respect to pollination vector and breeding system. However, pollination vector and breeding system are not associated with success, defined here as increasing range spread in the urban environment; instead, fruit type (dispersal), life form and origin are important determinants of success. Alien species that are deciduous trees, shrubs or vines with fleshy fruit are the most successful in increasing their distribution in this urban landscape. Newly introduced species with these characteristics are expected to have a better chance at establishing in similar urban landscapes and should be targets for intensive management. The ability to predict which alien species will become invasive is also a valuable tool for the prevention of invasions by newly introduced plant species.     

应用因子分析法研究茎瘤芥(榨菜)性状间的关系

应用因子分析法可把23份茎瘤芥品种资源的15个数量性状集约在5个主因子上,采用正交因子和斜交因子模型分析了性状间的遗传作用关系,并探讨了各因子间的关系及其生物学意义。     

Maladaptive changes in multiple traits caused by fishing: impediments to population recovery

Some overharvested fish populations fail to recover even after considerable reductions in fishing pressure. The reasons are unclear but may involve genetic changes in life history traits that are detrimental to population growth when natural environmental factors prevail. We empirically modelled this process by subjecting populations of a harvested marine fish, the Atlantic silverside, to experimental size-biased fishing regimes over five generations and then measured correlated responses across multiple traits. Populations where large fish were selectively harvested (as in most fisheries) displayed substantial declines in fecundity, egg volume, larval size at hatch, larval viability, larval growth rates, food consumption rate and conversion efficiency, vertebral number, and willingness to forage. These genetically based changes in numerous traits generally reduce the capacity for population recovery.