The influence of life‐history strategy on genetic differentiation and lineage divergence in darters (Percidae: Etheostomatinae)

Recent studies determined that darters with specialized breeding strategies can exhibit deep lineage divergence over fine geographic scales without apparent physical barriers to gene flow. However, the extent to which intrinsic characteristics interact with extrinsic factors to influence population divergence and lineage diversification in darters is not well understood. This study employed comparative phylogeographic and population genetic methods to investigate the influence of life history on gene flow, dispersal ability, and lineage divergence in two sympatric sister darters with differing breeding strategies. Our results revealed highly disparate phylogeographic histories, patterns of genetic structure, and dispersal abilities between the two species suggesting that life history may contribute to lineage diversification in darters, especially by limiting dispersal among large river courses. Both species also showed striking differences in demographic history, indicating that extrinsic factors differentially affected each species during the Pleistocene. Collectively, our results indicate that intrinsic and extrinsic factors have influenced levels of gene flow among populations within both species examined. However, we suggest that life‐history strategy may play a more important role in lineage diversification in darters than previously appreciated, a finding that has potentially important implications for understanding diversification of the rich North American freshwater fish fauna.     

UNIFICATION OF METHODS FOR ESTIMATING THE STRENGTH OF REPRODUCTIVE ISOLATION

Understanding the evolution of reproductive isolation is tantamount to describing the origin of species. Therefore, a primary goal in evolutionary biology is to identify which reproductive barriers are most important to the process. To achieve this goal, the strength of multiple forms of isolation must be compared in an equivalent manner. However, a diversity of methods has been used to estimate barrier strength, falling into several mathematically distinct categories. This study provides a unified method for calculating isolation that relates the amount of gene flow experienced by taxa to random expectations in a simple linear framework. This approach has three distinct advantages over previous methods: (1) it is directly related to gene flow, (2) it is symmetrical, such that measures in both the positive and negative range are comparable, and (3) it is equivalent between broad categories of reproductive isolation, allowing for appropriate comparisons. This linear formulation can be adjusted for use in all forms of isolation, and can accommodate cases in which null expectations for con‐ and heterospecific gene flow differ. Additionally, this framework can be used to calculate total reproductive isolation and the relative contributions of individual barriers.     

Policy Strategies to Promote Eco‐Innovation

This article elaborates an integrated policy framework, including policy features and specific measures that can be implemented to mitigate the barriers to eco‐innovations. We claim that factors inhibiting the development and uptake of eco‐innovations are multifaceted and stem from different sources. This systems view, which highlights the multilayered conception of the obstacles to eco‐innovation, calls for a combination of environmental and technology policies adapted to the different barriers and characteristics of the technologies. Drawing on evolutionary economics, the article sheds light on the appropriate combinations of framework conditions and instruments that are most effective to promote eco‐innovation, considering different barriers and eco‐innovation types (process/product, mature/immature, and radical/incremental).     

Mating compatibility among populations of codling moth Cydia pomonella Linnaeus (Lepidoptera: Tortricidae) from different geographic origins

The codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is a serious pest of pome fruit worldwide and the sterile insect technique (SIT) provides an environmentally acceptable approach for its control. As the pest is present in both the southern and northern hemispheres it would be possible for a rearing facility in the northern hemisphere to supply sterile moths to an SIT programme in the southern hemisphere during the northern winter and vice versa. This could greatly improve the economics of moth production and the running costs of rearing facilities. However in order to develop this concept, it is important to assess if populations of codling moth from different geographical regions share mating compatibility. Twelve different laboratory and field populations from both hemispheres were sampled and field cage bisexual mating compatibility tests were carried out between selected combinations. The index of sexual isolation (ISI) and the female and male relative performance index (FRPI and MRPI, respectively) were calculated for each mating combination. In only two of the combinations was there a slight but significant deviation from random mating. There were also some significant differences in mating duration between the homotypic matings and the duration of a particular homotypic mating seemed to depend on the origin of the other population in the cage. It was concluded that there exist no barriers to mating between populations of codling moth from many parts of the world and that it would be feasible for sterile moths to be shipped from one rearing facility to SIT programmes in other parts of the world.     

Waves of dispersal in island-hopping Chondrina species (Gastropoda, Pulmonata, Chondrinidae)

The aim of this study was to unravel the historical biogeography of the speciose land snail genus Chondrina. To this end phylogenetic hypotheses were tested using mitochondrial DNA sequence data.Mitochondrial DNA sequences of the Cytochrome Oxidase subunit I region were obtained for 89 individuals, representing just over 70% of the extant Chondrina species. The extent of molecular genetic diversity and phylogeographical patterns were investigated by using neighbour joining, parsimony and bayesian methods for phylogeny reconstructions. The resulting data were used to infer historical biogeographical patterns for the genus Chondrina.The three phylogenetic methods yielded congruent topologies for the phylogeny reconstruction. Six clades were identified, each of which with at least one taxon that is known from the Iberian peninsula. The most parsimonious scenario indicates at least three waves of dispersal out of the Iberian peninsula into the North and East of Europe and Northern Africa.The phylogenetic relationships combined with the distributional patterns of the various species, indicate that only vicariance events cannot explain the actual situation. Apparently, separate waves of dispersal and subsequent speciation occurred, each time starting from the southwestern part of the present generic range. Until recently, this was obscured by repetitive cases of parallel or convergent evolution in shell characters, as became evident with the use of molecular methods.     

Prevalence and intensity of avian malaria in a quail hybrid zone

Hybrid zones have been described as natural laboratories by researchers who study speciation and the various mechanisms that may affect gene flow. The evolutionary consequences of hybridization depend not only on reproductive compatibility between sympatric species, but also on factors like vulnerability to each other''s predators and parasites. We examined infection patterns of the blood parasite Haemoproteus lophortyx, a causative agent of avian malaria, at a site in the contact zone between California quail (Callipepla californica) and Gambel''s quail (C. gambelii). Controlling for the potential influence of sex and year, we tested whether species identity predicted infection status and intensity. We found that infection prevalence was lower in California and hybrid quail compared with Gambel''s quail. However, infected California and hybrid quail had higher infection intensities than Gambel''s quail. California and hybrid quail exhibited no significant differences in prevalence or intensity of infection. These findings suggest that infection by H. lophortyx has the potential to influence species barrier dynamics in this system; however, more work is necessary to determine the exact evolutionary consequences of this blood parasite on hybridization.     

Dispersal patterns of an Australian gall-forming thrips and its host tree (Oncothrips tepperi and Acacia oswaldii )

Abstract. 1. Clark and Evans' nearest-neighbour method was used to evaluate the distribution pattern of Acacia oswaldii and Oncothrips tepperi populations.
2. A random distribution pattern was supported statistically for both the host trees and trees that were parasitised by O. tepperi .
3. It is therefore likely that dispersal distances of colonising thrips are large enough to be able to traverse the 1 km² study site.     

Genetic divergence in the superspecies Manacus

The bearded manakins in the genus Manacus are lekking, neotropical passerines. Male plumage colour varies with geographical location and classification is based solely on these plumage patterns. It has recently been suggested that in this group of birds, plumage patterns may be a misleading taxonomic character. In this study we used microsatellite variation in a collection of museum samples to establish the amount of genetic divergence between the previously described bearded manakin species/subspecies. We found substantial genetic substructuring between species/subspecies and that plumage patterns indeed may be a misleading taxonomic character because the presence of yellow in male nuptial plumage is found in most divergent forms. We did not detect a significant isolation by distance relationship although the P -value was close to significance. Physical barriers such as rivers and mountains may affect gene flow and play a role in shaping genetic structure of the genus Manacus . Accordingly, boundaries between species/subspecies often coincide with large rivers, mountains and seas.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 439–447.     

Effects of forest canopy on habitat selection in treefrogs and aquatic insects: implications for communities and metacommunities

The specific dispersal/colonization strategies used by species to locate and colonize habitat patches can strongly influence both community and metacommunity structure. Habitat selection theory predicts nonrandom dispersal to and colonization of habitat patches based on their quality. We tested whether habitat selection was capable of generating patterns of diversity and abundance across a transition of canopy coverage (open and closed canopy) and nutrient addition by investigating oviposition site choice in two treefrog species (Hyla) and an aquatic beetle (Tropisternus lateralis), and the colonization dynamics of a diverse assemblage of aquatic insects (primarily beetles). Canopy cover produced dramatic patterns of presence/absence, abundance, and species richness, as open canopy ponds received 99.5% of propagules and 94.6% of adult insect colonists. Nutrient addition affected only Tropisternus oviposition, as females oviposited more egg cases at higher nutrient levels, but only in open canopy ponds. The behavioral partitioning of aquatic landscapes into suitable and unsuitable habitats via habitat selection behavior fundamentally alters how communities within larger ecological landscapes (metacommunities) are linked by dispersal and colonization.     

Acorn dispersal estimated by radio-tracking

Bird-dispersed seeds are difficult to track, especially in the case of long-distance dispersal events. To estimate the oak dispersal distance and the seed shadow generated by the European jay (Garrulus glandarius), we inserted radio-transmitters in 239 acorns, placed them in bird-feeders and then located them by radio-tracking. Using this methodology we located the exact caching site of 94 Quercus ilex and 54 Q. suber acorns and determined the caching habitat characteristics (vegetation type, distance, spatial distribution). The results show that: (1) there is no differences in the dispersal distance distribution between the different acorn species or sizes, (2) dispersal distances range from approximately 3 m up to approximately 550 m (mean = 68.6 m; median = 49.2 m), (3) recently abandoned fields and forest tracks were the sites preferred by jays to cache acorns, whereas fields and shrublands were avoided and (4) seed shadows showed acorn aggregation zones (i.e. clusters of caches) close to the feeder as well as isolated caches at longer distances. The results also suggest that radio-transmitters are a cheap and reliable way to determine seed shadows and quantify both seed dispersal and post-dispersal seed predation for medium to large seeds.