Dewlap and other variation in the lizards Anolis distichus and A. brevirostris (Reptilia: Iguanidae)

The dewlap of male anoline lizards is an important component of the mate recognition system. Much attention has focussed on the role dewlap colour plays in the interactions between species of Anolis but little has been paid to the effects of intraspecific variability in this feature. Patterns of intrasubspecific variability in this feature are described for several subspecies of Anolis distichus and A. brevirostris . In most cases variability in dewlap colour appears unrelated to the amount of electrophoretic variability and the level of population differentiation, although there is some evidence for large scale geographic subdivision within three of the taxa examined. Female choice and the implications for various species concepts are discussed.     

Mining online genomic resources in Anolis carolinensis facilitates rapid and inexpensive development of cross-species microsatellite markers for the Anolis lizard genus

Online sequence databases can provide valuable resources for the development of cross-species genetic markers. In particular, mining expressed tag sequences (EST) for microsatellites and developing conserved cross-species microsatellite markers can provide a rapid and relatively inexpensive method to develop new markers for a range of species. Here, we adopt this approach to develop cross-species microsatellite markers in Anolis lizards, which is a model genus in evolutionary biology and ecology. Using EST sequences from Anolis carolinensis, we identified 127 microsatellites that satisfied our criteria, and tested 49 of these in five species of Anolis (carolinensis, distichus, apletophallus, porcatus and sagrei). We identified between 8 and 25 new variable genetic markers for five Anolis species. These markers will be a valuable resource for studies of population genetics, comparative mapping, mating systems, behavioural ecology and adaptive radiations in this diverse lineage.     

The challenges of modelling antibody repertoire dynamics in HIV infection

Antibody affinity maturation by somatic hypermutation of B-cell immunoglobulin variable region genes has been studied for decades in various model systems using well-defined antigens. While much is known about the molecular details of the process, our understanding of the selective forces that generate affinity maturation are less well developed, particularly in the case of a co-evolving pathogen such as HIV. Despite this gap in understanding, high-throughput antibody sequence data are increasingly being collected to investigate the evolutionary trajectories of antibody lineages in HIV-infected individuals. Here, we review what is known in controlled experimental systems about the mechanisms underlying antibody selection and compare this to the observed temporal patterns of antibody evolution in HIV infection. We describe how our current understanding of antibody selection mechanisms leaves questions about antibody dynamics in HIV infection unanswered. Without a mechanistic understanding of antibody selection in the context of a co-evolving viral population, modelling and analysis of antibody sequences in HIV-infected individuals will be limited in their interpretation and predictive ability.     

Convergence and the multidimensional niche

Convergent evolution has played an important role in the development of the ecological niche concept. We investigated patterns of convergent and divergent evolution of Caribbean Anolis lizards. These lizards diversified independently on each of the islands of the Greater Antilles, producing the same set of habitat specialists on each island. Using a phylogenetic comparative framework, we examined patterns of morphological convergence in five functionally distinct sets of morphological characters: body size, body shape, head shape, lamella number, and sexual size dimorphism. We find evidence for convergence among members of the habitat specialist types for each of these five datasets. Furthermore, the patterns of convergence differ among at least four of the five datasets; habitat specialists that are similar for one set of characters are often greatly different for another. This suggests that the habitat specialist niches into which these anoles have evolved are multidimensional, involving several distinct and independent aspects of morphology.     

Chemosystematische Untersuchungen zur Phylogenese der Sammelgattung Lacerta (Reptilia: Sauria: Lacertidae)

Chemosystematic investigations concerning the phylogeny of the collective genus Lacerta (Reptilia: Sauria: Lacertidae) Investigated the albumins from 31 species and subspecies of the genus Lacerta s.1. by means of the immunoloical techniue Micro-Complement-fixation. Dendrograms were computed by means of the ktch-MargJiash algorithm. Moreover the taxa of the Lacerta saxicola and the Lacerta danfordi comlexes were analyzed by electrophoresis concerning 14 genetic loci. The results were discussel together with karyological and genitalmorphological data so far known yielding the following relationships: Lacerta graeca shows a closer relationshi to the subgenus Podarcis as does the quite closely related species air L. dugesii and L. perspicikata. Lacerta Iaevis probabl is connected closely to Podarcis, too. Lacerta parva shows a closer relationship to the “small izards” than to the sub-genus Lacerta s. str. A clear decision concerning the position of the Lacerta danfordi complex according to chemosystematical data was not possible. It is isolated from the other species probably about as long as L. puma. Biochemical differences between its “species” are too small to confirm their taxonomical revalorisation by Eiselt and Schmidtler Within the Lacerta saxicola complex the investigated taxa show a close relationship. Lacerta praticola and L. derjugini were definitly assigned to this group.     

Parasites—the new frontier: celebrating Darwin 200

To Darwin, parasites were fascinating examples of adaptation but their significance as selective factors for a wide range of phenomena has only been studied in depth over the last few decades. This work has had its roots in behavioural/evolutionary ecology on the one hand, and in population biology/ecology on the other, thus shaping a new comprehensive field of ‘evolutionary parasitology’. Taking parasites into account has been a success story and has shed new light on several old questions such as sexual selection, the evolution of sex and recombination, changes in behaviour, adaptive life histories, and so forth. In the process, the topic of ecological immunology has emerged, which analyses immune defences in a framework of costs and benefits. Throughout, a recurrent theme is how to appropriately integrate the underlying mechanisms as evolved boundary conditions into a framework of studying the adaptive value of traits. On the conceptual side, major questions remain and await further study.     

Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution

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Allozyme and morphology evolution in European Viviparidae (Mollusca: Gastropoda: Architaenioglossa)

The paper describes morphometric and allozymic differences among four European species of the family Viviparidae: Viviparus contectus (Millet, 1813), V. viviparus (Linnaeus, 1758), V. acerosus Bourguignat, 1862, and V. ater (Cristofori et Jan, 1832). Fourteen continuous biometrical characters were measured. Incremental discriminant-function analysis, principal-component analysis, and non-metric multidimensional scaling were applied to analysis of the morphometric differences. All the techniques confirmed a similar picture: a slight morphometric differentiation, with the variability ranges of the species overlapping. On the other hand, the allozymic differentiation, studied at 12 loci, eight of them intra and/or interspecific polymorphic, is much better marked, the intraspecific Nei's distances among the four V. contectus populations ranging from 0.0014 to 0.0397, mean 0.0166, and interspecific distances ranging from 0.2306 (V. ater–V. acerosus) to 0.9888 (V. contectus 2 and V. viviparus), mean 0.6871. The allele frequencies and genetic distances (Nei's distance and Cavalli-Sforza and Edwards’chord distance) were used to compute maximum likelihood, additive Fitch–Margoliash and ultrametric Fitch–Margoliash trees. All the trees presented a similar pattern, but the maximum-likelihood and additive trees, based on Cavalli-Sforza and Edwards’distance, seem to reflect the phylogeny best. The results are compared with the most parsimonious phylogenies inferred for radular, soft-part morphology and anatomy, and opercular data from other papers by us, and the inferred phylogenies are also compared. Although the inferred molecular and morphological phylogenies are little different in topology, the amount of evolution along the corresponding branches (measured as the number of changes averaged over all reconstructions) is very different, the value of correlation coefficient between the two phylogenies being statistically insignificant. The occurrence of interspecific hybrids is discussed, and the isolation-by-competition mechanism is postulated. The probable origin of V. viviparus from a founder population extremely restricted in number is stressed. The possible history of the group is briefly discussed. The species is suggested to have originated in an unusual habitat of melt water at a glacier foreland that could have promoted genotypic differentiation and sympatric speciation.     

Ancient islands and modern invasions: disparate phylogeographic histories among Hispaniola's endemic birds

With its large size, complex topography and high number of avian endemics, Hispaniola appears to be a likely candidate for the in situ speciation of its avifauna, despite the worldwide rarity of avian speciation within single islands. We used multilocus comparative phylogeography techniques to examine the pattern and history of divergence in 11 endemic birds representing potential within-island speciation events. Haplotype and allele networks from mitochondrial ND2 and nuclear intron loci reveal a consistent pattern: phylogeographic divergence within or between closely related species is correlated with the likely distribution of ancient sea barriers that once divided Hispaniola into several smaller paleo-islands. Coalescent and mitochondrial clock dating of divergences indicate species-specific response to different geological events over the wide span of the island's history. We found no evidence that ecological or topographical complexity generated diversity, either by creating open niches or by restricting long-term gene flow. Thus, no true within-island speciation appears to have occurred among the species sampled on Hispaniola. Divergence events predating the merging of Hispaniola's paleo-island blocks cannot be considered in situ divergence, and postmerging divergence in response to episodic island segmentation by marine flooding probably represents in situ vicariance or interarchipelago speciation by dispersal. Our work highlights the necessity of considering island geologic history while investigating the speciation-area relationship in birds and other taxa.     

Anoline Diversity in Three Differentially Altered Habitats in the Sierra de Baoruco,República Dominicana,Hispaniola1

We examined three disturbed, but distinctly different, sites on the historically forested eastern slope of the Sierra de Baoruco, Provincia de Barahona, República Dominicana, in order to evaluate the impact of habitat alteration on the composition of anoline lizard communities. Five species of Anolis (A. bahorucoensis, A. barahonae, A. coelestinus, A. sybotes, A. distichus) are known to occur in the immediate area of our study sites. Only three were found in the most substantially altered clear-cut site, whereas all five species occupied the most heterogeneous habitat, a coffee plantation characterized by a three-tiered canopy. Similarly, numbers of individuals of all but one species were greatest in the plot that most closely resembled the natural forests in this area. Calculated niche breadths, based on analysis of stomach contents, of the three species found in all sites increased with the degree of habitat alteration. The higher number of A. coelestinus in more heavily altered sites may be attributed to density compensation.     

SURVIVAL OF HYBRIDS IN A MOSAIC HYBRID ZONE

The ground crickets Allonemobius fasciatus and A. socius meet in a mosaic hybrid zone that stretches from New Jersey at least as far west as Illinois. Within mixed populations from the contact zone, “pure” species individuals predominate. To determine whether hybrids are less viable than pure-species individuals, and to assess whether the high proportion of pure-species individuals in mixed populations results from hybrid inviability, we performed a cohort analysis. In this study, five mixed populations from the hybrid zone were each sampled three to five times from the fall of 1986 to the spring of 1988. Individuals were assigned to one of three categories based on their genotypes: A. socius (individuals harboring only alleles unique to A. socius), hybrid (individuals with alleles unique to both species), and A. fasciatus (individuals harboring only alleles unique to A. fasciatus). This sampling and measurement scheme permitted monitoring of the proportion of hybrid individuals in a population over time. The results were fairly consistent. The relative survival of A. socius was greater than the relative survival of members of the other two groups in four of the five populations. The relative viability of A. fasciatus was greater than that of hybrids in one population, approximately equal to that of hybrids in two populations, and less than that of hybrids in two populations. These results not only shed light on an important component of fitness, viability from hatching to adulthood, but they demonstrate that loss of hybrid individuals during the course of the field season will not explain deviations from random mating expectations present in mixed populations in late summer. The deviations must be due to assortative mating or to a reproductive barrier operating prior to egg hatch.