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Obligate parthenogenesis is found in only 0.1% of the vertebrate species, is thought to be relatively short lived and is typically of hybrid origin. However, neither the evolutionary persistence of asexuality in vertebrates, nor the conditions that allow the generation of new parthenogenetic lineages are currently well understood. It has been proposed that vertebrate parthenogenetic lineages arise from hybridisation between two divergent taxa within a specific range of phylogenetic distances (the ‘Balance Hypothesis’). Moreover, parthenogenetic species often maintain a certain level of hybridisation with their closest sexual relatives, potentially generating new polyploid hybrid lineages. Here we address the role of hybridisation in the origin and evolutionary lifespan of vertebrate parthenogens. We use a set of microsatellite markers to characterise the origins of parthenogens in the lizard genus Darevskia, to study the distinctiveness of sexual and asexual taxa currently in sympatry, and to analyse the evolutionary consequences of interspecific hybridisation between asexual females and sexual males. We find that parthenogens result from multiple past hybridisation events between species from specific lineages over a range of phylogenetic distances. This suggests that the Balance Hypothesis needs to allow for lineage-specific effects, as envisaged in the Phylogenetic Constraint Hypothesis. Our results show recurrent backcrossing between sexual and parthenogenic Darevskiabut neither gene flow nor formation of new asexual lineages. We suggest that, along with their demographic advantage, parthenogens gain additional leverage to outcompete sexuals in nature when the retention of sexual reproductive machinery allows backcrossing with their sexual ancestors.

Genetic variability among males is a necessary precondition for the evolution of female choice based on indirect genetic benefits. In addition to mutations and host–parasite cycles, migration of locally adapted individuals offers an explanation for the maintenance of genetic variability. In a previous study, conducting a reciprocal transplant experiment on a grasshopper, Chorthippus biguttulus, we found that environmental conditions significantly influenced not only body condition but also an important trait of male calling song, the amplitude of song. Although not significant, all other analysed physical and courtship song traits and attractiveness were superior in native than in transferred males. Thus, we concluded that local adaptation has a slight but consistent influence on a range of traits in our study populations, including male acoustic attractiveness. In our present study, we scanned male grasshoppers from the same two populations for amplification fragment length polymorphism (AFLP) loci connected with acoustic attractiveness to conspecific females. We found greater differences in allele frequencies between the two populations, for some loci, than are expected from a balance between drift and gene flow. These loci are potentially connected with locally adapted traits. We examined whether these alleles show the proposed genotype environment interaction by having different associations with attractiveness in the two populations. One locus was significantly related to sexual attractiveness; however, this was independent of the males’ population affiliation. Future research on the evolution of female choice will benefit from knowledge of the underlying genetic architecture of male traits under intraspecific sexual selection, and the ‘population genomics’ approach can be a powerful tool for revealing this structure.

Population differences in anti-predator behaviour have been demonstrated in several species, although less is known about the genetic basis of these traits. To determine the extent of genetic differences in boldness (defined as exploration of a novel object) and shoaling within and between zebrafish ( Danio rerio) populations, and to examine the genetic basis of shoaling behaviour in general, we carried out a study that involved laboratory-raised fish derived from four wild-caught populations. Controlling for differences in rearing environment, significant inter-population differences were found in boldness but not shoaling. A larger shoaling experiment was also performed using one of the populations as the basis of a North Carolina type II breeding design (174 fish in total) to estimate heritability of shoaling tendency. A narrow-sense heritability estimate of 0.40 was obtained, with no apparent dominance effects.

The grasshopper species Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) form a hybrid zone in northern Spain. These species probably diverged while isolated in southern refugia during one of the recent ice ages, and are clearly distinguished by morphology and male calling song. However, in contrast to other Chorthippus taxa that form hybrid zones in Europe, these two species cannot be reliably distinguished on the basis of characteristics of the karyotype such as heterochromatin banding patterns and composition, as revealed by C-banding and fluorochrome staining. Silver staining also reveals the presence of two autosomal nucleolar organiser regions (NORs) in both species. However, differentiation between C. brunneus and C. jacobsi was revealed on the X chromosome using fluorescent in situ hybridisation (FISH). C. brunneus individuals showed additional rDNA sequences on the X chromosome that were not observed in any C. jacobsi individuals. These sequences are not transcribed, indicating either mutational silencing of an ancestral NOR on the X chromosome, or the transposition of non-functional sequences from the autosomes. The implications of these results for the evolution of NOR number in Chorthippus are discussed.

We investigate colour pattern and morphological variation in Chitauragrasshoppers on the Indonesian island of Sulawesi, and examine the relationship between divergence in these two sets of characters and population history, as reflected by variation in mitochondrial DNA. Analysis of colour pattern variation identifies a total of 21 distinct Operational Taxonomic Units in Sulawesi, the majority of which have parapatric distributions. Patterns of phenotypic variation at two contact zones in north Sulawesi suggest genetic independence between three of these colour forms, indicating that speciation has occurred. Despite this, colour pattern divergence is only coincident with morphological differentiation at one of these contact zones. In addition, neither type of phenotypic divergence is associated with geographical structuring in mitochondrial DNA, suggesting that historical isolation has had little influence on evolutionary diversification. Instead, divergence in colour pattern and morphology appears to have occurred rapidly or under conditions of continued gene flow, possibly in response to spatially variable natural selection. This result has implications for the identification of conservation units based solely on molecular markers.

Genetic variability of the non–marine ostracod speciesDarwinula stevensoniwas estimated by sequencing part of the nuclear and the mitochondrial genome. As Darwinulidae are believed to be ancient asexuals, accumulation of mutations should have occurred, both between alleles within lineages and between lineages, during the millions of years of parthenogenetic reproduction. However, our sequence data show the opposite: no variability in the nuclear ITS1 region was observed within or among individuals of D. stevensoni, despite sampling a geographical range from Finland to South Africa. Lack of allelic divergence might be explained by concerted evolution of rDNA repeats. Homogeneity among individuals may be caused either by slow molecular evolution in ITS1 or by a recent selective sweep. Variability of mitochondrial cytochrome oxidase (COI) was similar to intraspecific levels in other invertebrates, thus weakening the latter hypothesis. Calibrating interspecific, genetic divergences among D. stevensoniand other Darwinulidae using their fossil record enabled us to estimate rates of molecular evolution. Both COI and ITS1 evolve half as fast, at most, in darwinulids as in other invertebrates, and molecular evolution has significantly slowed down in ITS1 of D. stevensonirelative to other darwinulids. A reduced ITS1 mutation rate might explain this inconsistency between nuclear and mitochondrial evolution in D. stevensoni.

Courtship song is known to vary among several groups of closely related species ofDrosophila. The present study investigates differences in song among four members of thequinariagroup of fungal-breedingDrosophilawhich are known to coexist in Britain and the near-continent. Results show that the species can be distinguished by several song parameters including interpulse interval.D. phaleratais very different from the other three species, while there is considerable overlap betweenD. kuntzeiandD. limbatain several characters.D. transversaappears to be more similar to the latter species than it is toD. phalerata. The question of mate choice and the potential for reproductive character displacement are discussed.

Two subspecies of the grasshopper Chorthippus parallelusmeet and form a hybrid zone in the Pyrenees. Both strong hybrid dysfunction and a behavioural difference occur, which would seem to make the zone a suitable candidate for speciation by reinforcement. One of the classic ways of looking for this is to test for increased levels of assortative mating between populations from close to the region of contact. Here we show that, with virgin insects, such assortment decreases as one approaches the centre of the zone in C. parallelus. The pattern is different upon remating, with non-virgins showing a pattern more like that predicted by reinforcement. Overall there is little evidence for reinforcement. We argue that other tests of the model may be more appropriate for stable hybrid zones.

Two parapatric subspecies of the grasshopper Chorthippus parallelusform a hybrid zone in the Pyrenees. Partial assortative mating between subspecies must result from differences in elements of the sequence of behaviors that leads to mating. It was already known that the subspecies differ in the structure of the acoustic mating signal produced by males and in the amount of song produced under laboratory conditions. Here we investigate whether any differences exist in male mating strategies in the field, concentrating on the prediction that male C. p. erythropussing less and compensate for this by active searching (males divide their time between singing and moving in search of females). Results of field observations show that the two subspecies do in fact allocate their time differently. C. p. erythropusmales spend almost twice as much time moving around the habitat as C. p. parallelusmales. Furthermore, C. p. parallelusmales divide their time into long bouts of continuous singing alternating with periods of movement. C. p. erythropusmales, on the other hand, sing in short bursts interspersed with movement. The possible reasons for this divergence in male mating behavior and its consequences are discussed.

Two subspecies of the grasshopperChorthippus parallelus(Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.

Fisher's runaway process is an explanation for the origin of conspicuous features which make one sex more attractive to the other. It has been suggested that it could lead to the evolution of sexual characters that significantly impair viability. Runaway selection requires a genetic correlation between alleles affecting the sexual character and alleles affecting the preference. Correlations may be expected because of assortative mating when there is variation in both the sexual character and sexual preferences. We contend that such genetic correlations are unlikely to persist in finite populations. We present simulations which confirm our expectations. They suggest that assortative mating is inefficient at generating correlations, especially if sexual selection maintains characters away from their viability optimum. In finite populations, such weak correlations will be overwhelmed by drift.

Chromosomal rearrangements are often the only apparent difference between closely related species, although it is not clear whether they are a cause or a by-product of speciation. We suggest that changes in the pattern of recombination may provide a link between chromosomal rearrangements and speciation. In models of speciation by sexual selection and by reinforcement, recombination is a major barrier to the formation of new species, primarily because it opposes the establishment of linkage disequilibrium. Here we show that in both the Felsenstein (1981) and Kirkpatrick (1982) models, a recombination suppressor is able to enhance the processes leading to speciation and increase its own frequency in the population.Heredity (1994) 73, 339–345; doi:10.1038/hdy.1994.180

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The long-fingered bat Myotis capaccinii (Bonaparte, 1837) is considered rare and is listed as vulnerable on the IUCN Red List of Threatened Species (2007). It remains one of the least studied bats in Europe. Protection of roosts is fundamental to bat conservation but, for it to be effective, knowledge about roosting ecology is required. We evaluated roosting habits, colony structure, and colony composition of M. capaccinii in the National Park of Dadia-Lefkimi-Soufli in Greece during 2002–2004 at 6 underground sites. We report results from regular capture of marked individuals and measures of roost microclimate. Individuals formed large maternity colonies in spring. Parturition began in April and by the end of May all captured females had given birth. The 1st volant young appeared in late June and almost all were weaned by the end of July. Summer colonies were sexually segregated; few males were present in the nursery roosts. Adult females began to disperse in August and the proportion of males increased through September and October. Young born in the year remained in the roosts after the females had left. M. capaccinii selected summer roosts with a wide range of temperatures, tolerating temperatures as low as 11.2°C, probably because of the thermoregulatory benefits of aggregating in single- and multispecies clusters. Few individuals remained in these sites during the winter. The majority of females appeared to reach sexual maturity in their 1st autumn and most males did so in their 2nd year. Body mass of males increased steadily from spring through to autumn, whereas mass of females only increased in the autumn before hibernation, except for the additional weight of the fetus during pregnancy, implying that reproduction imposes energetic constraints on females.

The objective of this study was to test for associations between land cover data and the presence of mosquito larvae of the genera Aedes Meigen and Anopheles Meigen in northern Thailand at the landscape scale. These associations were compared with associations between larval habitat variables and the presence of mosquito larvae at a finer spatial scale. Collection data for the larvae of one Aedes species and three species-groups of Anopheles, all of which are involved in pathogen transmission, were used. A variety of northern Thai landscapes were included, such as upland villages, lowland villages and peri-urban areas. Logistic regression was used to evaluate associations. Generally, land cover and landscape variables explained the presence of larvae as well as did larval habitat variables. Results were best for species/species-groups with specific habitat requirements. Land cover variables act as proxies for the types of habitat available and their attributes. Good knowledge of the habitat requirements of the immature stages of mosquitoes is necessary for interpreting the effects of land cover.