Phenotypic consequences of genetic variation in a gynogenetic complex of Phoxinus eos-neogaeus clonal fish (Pisces: Cyprinidae) inhabiting a heterogeneous environment

We examined the genetic composition, habitat use, and morphological variation of a Phoxinus eos-neogaeus unisexual hybrid complex and its sexually reproducing progenitor species inhabiting beaver-modified drainages of Voyageurs National Park, Minnesota. In addition to the single diploid P. eos-neogaeus gynogenetic clone, triploid and diploid-triploid mosaic biotypes were present at our study sites. Both P. eos and P. neogaeus, and all three hybrid biotypes were ubiquitous throughout one intensively surveyed drainage, but abundances and relative frequencies of the parental species and hybrids varied considerably within and among successional environments. Data from a large number of additional sites indicated that the proportion of polyploid hybrids within an environment was negatively related to hybrid relative frequency, implying that the genomic constitution of hybrids is an important determinant of clonal fitness among successional environments. Statistical comparisons of variation along size-free multivariate body shape axes indicated that despite its genetic uniformity, the P. eos-neogaeus clone is no less variable than its sexual progenitors, suggesting that a single genotype may actually respond to environmental variation with as much phenotypic variation as a genetically variable sexual population. The incorporation and expression of a third genome in triploid and diploid-triploid mosaic biotypes derived from the gynogenetic clone significantly expanded phenotypic variation of the clone. This additional variation results in greater similarities in habitat use and morphological overlap with the parental species, primarily P. eos, the predominant sperm donor for gynogenetic hybrid females in this complex. Polyploid augmentation of a diploid gynogenetic clone appears to be typical in the P. eos-neogaeus complex, and the additional genetic and phenotypic variation that it generates has potentially significant ecological and evolutionary consequences for the success and persistence of a single genotype in highly variable environments.     

Helminth parasite richness among vertebrates

The numbers of intestinal helminth species (parasite richnesS) recorded from each of 488 vertebrate host species are compared using data compiled from the published literature. Associations between parasite richness, sampling effort, host size and host habitat (aquatic versus terrestrial) are assessed using a method designed to control for phylogenetic association. Parasite richness increases with the number of surveys on which each estimate of parasite richness is based (sampling effort). When the effects of sampling effort are controlled for, there remains a strong positive relationship between parasite richness and host body size. There is no tendency for aquatic hosts to harbour more parasite species than terrestrial hosts independently of differences in sampling effort and body size. The results are interpreted in the context of hosts representing habitats for parasite colonization, resource allocation between parasite species, and the age of the major mammalian radiations.     

Variability in diet and foraging behaviour between sexes and ploidy forms of the hybridogenetic Squalius alburnoides complex (Cyprinidae) in the Guadiana River basin, Portugal

Samples of the Squalius alburnoides complex, a hybridogenetic Iberian minnow composed of diploid, triploid and, less commonly, tetraploid forms, were collected from a tributary of the Ardila River (Guadiana River basin) between February 1999 and January 2001. Seasonal variation in diet was evident, and was probably linked to prey availability. Distinct foraging behaviours between ploidy forms were found towards several prey items, suggesting that diploid adult males fed mostly near the surface, whereas diploid adult females tended to feed near the bottom and submerged vegetation. Triploid females exhibited an intermediate foraging behaviour, although there was greater affinity towards diploid male feeding behaviour. Diploid males which, in contrast to diploid and triploid females, have non‐hybrid genomes in the Guadiana drainage, exhibited a higher specialization for food. Despite considerable dietary overlap, there appeared to be spatial segregation of feeding niches between the three forms, especially during dry periods when prey availability was lower, which may be a strategy for diminishing competition for food. Therefore, considering asexual generalist and specialist hypotheses, it appears that the different ploidy levels are generalist, opportunistic feeders that partition the resources when limited.     

The pineal organ as a folded retina: immunocytochemical localization of opsins

The most simple pineal complex (the pineal and parapineal organs of lampreys), consists of saccular evaginations of the diencephalic roof, and has a retina-like structure containing photoreceptor cells and secondary neurons. In more differentiated vertebrates, the successive folding of the pineal wall multiplies the cells and reduces the lumen of the organ, but the pattern of the histological organization remains similar to that of lampreys; therefore, we consider the histological structure of the pineal organ of higher vertebrates as a 'folded retina'. The cell membrane of several pineal photoreceptor outer-segments of vertebrates immunoreact with anti-retinal opsin antibodies supporting the view of retina-like organization of the pineal. Some other pineal outer segments do not react with retinal anti-opsin antibodies, a result suggesting the presence of special pineal photopigments in different types of pinealocytes that obviously developed during evolution. The chicken pinopsin, detected in the last years, may represent one of these unknown photopigments. Using antibodies against chicken pinopsin, we compared the immunoreactivity of different photoreceptors of the pineal organs from cyclostomes to birds at the light and electron microscopic levels. We found pinopsin immunoreaction on all pinealocytes of birds and on the rhodopsin-negative large reptilian pinealocytes. As the pinopsin has an absorption maximum at 470 nm, these avian and reptilian immunoreactive pinealocytes can be regarded as green-blue light-sensitive photoreceptors. Only a weak immunoreaction was observed on the frog and fish pinealocytes and no reaction was seen in cyclostomes and in the frontal organ of reptiles. Some photoreceptors of the retina of various species also reacted the pinopsin antibodies, therefore, pinopsin must have certain sequential similarity to individual retinal opsins of some vertebrates.     

Evidence of reduced individual heterogeneity in adult survival of long‐lived species

The canalization hypothesis postulates that the rate at which trait variation generates variation in the average individual fitness in a population determines how buffered traits are against environmental and genetic factors. The ranking of a species on the slow‐fast continuum – the covariation among life‐history traits describing species‐specific life cycles along a gradient going from a long life, slow maturity, and low annual reproductive output, to a short life, fast maturity, and high annual reproductive output – strongly correlates with the relative fitness impact of a given amount of variation in adult survival. Under the canalization hypothesis, long‐lived species are thus expected to display less individual heterogeneity in survival at the onset of adulthood, when reproductive values peak, than short‐lived species. We tested this life‐history prediction by analysing long‐term time series of individual‐based data in nine species of birds and mammals using capture‐recapture models. We found that individual heterogeneity in survival was higher in species with short‐generation time (< 3 years) than in species with long generation time (> 4 years). Our findings provide the first piece of empirical evidence for the canalization hypothesis at the individual level from the wild.     

The myosepta in Branchiostoma lanceolatum (Cephalochordata): 3D reconstruction and microanatomy

Zoomorphology - Myosepta have been subject to comparative and evolutionary studies in aquatic groups of the Craniata, because they are likely to play a role in transmission of muscular forces to...     

Dispersal and the transition to sympatry in vertebrates

Under allopatric speciation models, a key step in the build-up of species richness is population dispersal leading to the co-occurrence of previously geographically isolated forms. Despite its central importance for community assembly, the extent to which the transition from spatial segregation (allopatry or parapatry) to coexistence (sympatry) is a predictable process, or alternatively one governed by chance and the vagaries of biogeographic history, remains poorly understood. Here, we use estimated divergence times and current patterns of geographical range overlap among sister species to explore the evolution of sympatry in vertebrates. We show that rates of transition to sympatry vary predictably according to ecology, being faster in marine or strongly dispersive terrestrial clades. This association with organism vagility is robust to the relative frequency of geographical speciation modes and consistent across taxonomic scales and metrics of dispersal ability. These findings reject neutral models of dispersal assembly based simply on evolutionary age and are not predicted by the main alternative view that range overlap is primarily constrained by biotic interactions. We conclude that species differences in dispersal limitation are fundamental in organizing the assembly of ecological communities and shaping broad-scale patterns of biodiversity over space and time.     

dbCNS: A New Database for Conserved Noncoding Sequences

We developed dbCNS (http://yamasati.nig.ac.jp/dbcns), a new database for conserved noncoding sequences (CNSs). CNSs exist in many eukaryotes and are assumed to be involved in protein expression control. Version 1 of dbCNS, introduced here, includes a powerful and precise CNS identification pipeline for multiple vertebrate genomes. Mutations in CNSs may induce morphological changes and cause genetic diseases. For this reason, many vertebrate CNSs have been identified, with special reference to primate genomes. We integrated ∼6.9 million CNSs from many vertebrate genomes into dbCNS, which allows users to extract CNSs near genes of interest using keyword searches. In addition to CNSs, dbCNS contains published genome sequences of 161 species. With purposeful taxonomic sampling of genomes, users can employ CNSs as queries to reconstruct CNS alignments and phylogenetic trees, to evaluate CNS modifications, acquisitions, and losses, and to roughly identify species with CNSs having accelerated substitution rates. dbCNS also produces links to dbSNP for searching pathogenic single-nucleotide polymorphisms in human CNSs. Thus, dbCNS connects morphological changes with genetic diseases. A test analysis using 38 gnathostome genomes was accomplished within 30 s. dbCNS results can evaluate CNSs identified by other stand-alone programs using genome-scale data.     

Non-indigenous terrestrial vertebrates in Israel and adjacent areas

We investigated characteristics of established non-indigenous (ENI) terrestrial vertebrates in Israel and adjacent areas, as well as attributes of areas they occupy. Eighteen non-indigenous birds have established populations in this region since 1850. A database of their attributes was compiled, analyzed, and compared to works from elsewhere. Most ENI bird species are established locally; a few are spreading or widespread. There has been a recent large increase in establishment. All ENI birds are of tropical origin, mostly from the Ethiopian and Oriental regions; the main families are Sturnidae, Psittacidae, Anatidae, and Columbidae. Most species have been deliberately brought to Israel in captivity and subsequently released or escaped. Most of these birds are commensal with humans to some degree, are not typically migratory, and have mean body mass larger than that of the entire order. ENI birds are not distributed randomly. There are centers in the Tel-Aviv area and along the Rift Valley, which is also a corridor of spread. Positive correlations were found between ENI bird richness and mean annual temperature and urbanization. Mediterranean forests and desert regions have fewer ENI species than expected. Apart from birds we report on non-indigenous species of reptiles (2) and mammals (2) in this region.