ASYMMETRIC VIABILITY OF RECIPROCAL-CROSS HYBRIDS BETWEEN CRESTED AND MARBLED NEWTS (TRITURUS CRISTATUS AND T. MARMORATUS)

Hybridization between divergent lineages often results in reduced hybrid viability. Here we report findings from a series of independent molecular analyses over several seasons on four life stages of F₁ hybrids between the newts Triturus cristatus and T. marmoratus . These two species form a bimodal hybrid zone of broad overlap in France, with F₁ hybrids making up about 4% of the adult population. We demonstrate strong asymmetry in the direction of the cross, with one class ( cristatus -mothered) making up about 90% of F₁ hybrids. By analyzing embryos and hatchlings, we show that this asymmetry is not due to prezygotic effects, as both classes of hybrid embryos are present at similar frequencies, implicating differential selection on the two hybrid classes after hatching. Adult F₁ hybrids show a weak Haldane effect overall, with a 72% excess of females. The rarer marmoratus -mothered class, however, consists entirely of males. The absence of females from this class of adult F₁ hybrids is best explained by an incompatibility between the cristatus X chromosome and marmoratus cytoplasm. It is thus important to distinguish the two classes of reciprocal-cross hybrids before making general statements about whether Haldane's rule is observed.     

Cytology, embryology, and evolution of the developmental arrest syndrome in newts of the genus Triturus (Caudata: Salamandridae)

We have examined embryonic development in three species (T. carnifex, T. cristatus, and T. marmoratus) of European newts of the genus Triturus (subgenus Neotriton) in which developmental arrest occurs in embryos that are homomorphic for a chromosomal heteromorphism involving chromosome 1 (Horner and Macgregor: J. Herpetol., 19:261-270, 1985). Embryonic arrest occurred during tailbud stages in all three species, but at a slightly earlier stage in T. marmoratus. Two phenotypes were identified among the arrested embryos. One of these is indistinguishable in embryonic morphology from normal embryos at all stages up to the time of arrest, but the other is characterized by a protruding yolk plug, which persists from the late gastrula/early neurula stage to the tailbud arrest stage and apparently interferes with normal morphogenesis. Evidence is presented that the two arrested phenotypes, which occur in approximately equal numbers, represent embryos that carry the two alternative homomorphic chromosome pairs of chromosome 1 heteromorphism. We conclude that developmental arrest reflects a balanced lethal heterozygosity probably resulting from an unequal exchange of genic material between the homologues of chromosome 1 which occurred in a common ancestor of the Neotriton species.     

Differential effects of pH and temperature on embryonic development in the British newts (Triturus)

Changes in the water quality and temperature relationships of ponds may affect the structure of amphibian assemblages. The survival, time to hatching, hatching size and hatching stage of newt embryos were studied in the three British species ( Triturus cristatus, T. helveticus and T. vulgaris ), at two temperatures and two pHs. All T. cristatus embryos failed to hatch at pH 4.5, whereas over 80% of T. helveticus and T. vulgaris embryos hatched successfully at the same pH. At pH 7.5, T. cristatus survival was the same as the other two species, after the 50% mortality due to the homomorphism of chromosome 1 was taken into account. Temperature had no effect on survival of embryos. Time to hatching was two to four times longer at 12°C than at 17°C. Low pH shortened development time in T. vulgaris but not in T. helveticus . Low pH, but not temperature, affected size at hatching, with T. helveticus and T. vulgaris embryos emerging at a smaller size and earlier stage of development under acidic conditions. This reduction of size at low pH affected T. vulgaris more than T. helveticus . We predict that T. cristatus embryos will be the most vulnerable of the three species to acidification in nature. Warm ponds will result in rapid embryonic development, but T. helveticus and T. vulgaris larvae hatching in acid ponds will do so at a smaller size and earlier stage of development. The pattern of vulnerability to acidification within amphibian assemblages may change during ontogeny.     

Female size and age-specific fecundity in the small white butterfly,Pieris rapae crucivora Boisduval (Lepidoptera: Pieridae)

Individual differences in several reproductive parameters of female Pieris rapae were investigated in a controlled laboratory condition. Lifetime and age-specific fecundity showed considerable variability between individuals. Larger females began oviposition at an earlier age than smaller ones, and larger females were more fecund than smaller ones. Larger females laid a larger proportion of their eggs in the early stages of their reproductive lifetime, whilst smaller females laid the larger proportion of their eggs later in their reproductive lifetime. The significance of the variance in age-specific fecundity associated with female size is discussed with respect to the seasonal change in size and habitat utilization of this species.     

The annual number of breeding adults and the effective population size of syntopic newts (Triturus cristatus, T. marmoratus)

Pond-breeding amphibians are deme-structured organisms with a population genetic structure particularly susceptible to demographic threats. We estimated the effective number of breeding adults (Nb) and the effective population size (Ne) of the European urodele amphibians Triturus cristatus (the crested newt) and T. marmoratus (the marbled newt), using temporal shifts in microsatellite allele frequencies. Eight microsatellite loci isolated from a T. cristatus library were used, five of which proved polymorphic in T. marmoratus, albeit with high frequencies of null alleles at two loci. Three ponds in western France were sampled, situated 4-10 kilometers apart and inhabited by both species. Parent-offspring cohort comparisons were used to measure Nb; samples collected at time intervals of nine or 12 years, respectively, were used to measure Ne. The adult population census size (N) was determined by mark-recapture techniques. With one exception, genetic distances (FST) between temporal samples were lower than among populations. Nb ranged between 10.6 and 101.8 individuals, Ne ranged between 9.6 and 13.4 individuals. For the pond where both parameters were available, Nb/N (overall range: 0.10-0.19) was marginally larger than Ne/N (overall range: 0.09-0.16), which is reflected in the temporal stability of N. In line with the observed differences in reproductive life-histories between the species, Nb/N ratios for newts were about one order of magnitude higher than for the anuran amphibian Bufo bufo. Despite of the colonization of the study area by T. cristatus only some decades ago, no significant genetic bottleneck could be detected. Our findings give rise to concerns about the long-term demographic viability of amphibian populations in situations typical for European landscapes.     

A phylogeny for the Old World newts, genus Triturus: biochemical and behavioural data

A reconstruction is presented of the phylogenetic relationships withing Triturus . Two different data sets are used. Protein electrophoretic data were scored for 19 presumptive gene loci in nine species (Rafinski & Arntzen, 1987) and a set of 16 behaviour characters from the courtship of Triturus was scored for the same nine species. When these are analysed in concernt, a single, fully resolved and robust solution is found. Consequently, two subgenera are recognized: Triturus and Palaeotriton , the former including all te medium- and large-bodied species: T. alpestris, T. vittatus, T. marmoratus, T. cristatus and its three former subspecies ( T. carnifex, T. dobrogicus and T. Karelini ); the latter comprising the small-bodied species: T. bascai, T. italicus, T. helveticus, T. vulgaris and T. montandoni . Within the subgenus Triturus, T. alpestris and T. vittatus are sister taxa to the remaining members of the subgenus. Similarly, T. boscai and T. italicus are a monophyletic group, sister to T. vulgaris, T. helveticus and T. montandoni . Alternative solutions may be found on the basis of a quantitative analysis of the behavioural characters employed in this study. An alternative phylogenetic tree is included as an example.     

Influence of introduced fish Percottus glenii (Odontobutidae, Pisces)

Monitoring of 28 waterbodies has been carried out since 1994 in the region of reserve "Lake Glubokoe" (Moscow region, Russia). It was revealed that species diversity as well as abundance of larval amphibians correlate negatively with presence of introduced fish, rotan, Perccottus glenii (Odontobutidae). Newts (Triturus cristatus, T. vulgaris) and frogs (Rana temporaria, R. arvalis, R. lessonae) as a rule are not capable to breed in waterbodies colonised by rotan. In contrast, toads (Bufo bufo) breed successfully in such sites. Larvae of toads are comparatively less edible for rotan and pass their metamorphosis. Persistence of amphibians to predation of rotan decreases in the row: B. bufo (R. temporaria, R. arvalis and R. lessonae), T. vulgaris, T. cristatus. The Crested newt (T. cristatus) is the most endangered species and could extinct in next years.     

Female survival,lifetime reproductive success and mating status in a passerine bird

In facultatively polygynous birds, secondary females of polygynously mated males typically have reduced annual reproductive success, because polygynous males provide less paternal care than monogamous males. Life history theory predicts that, as a result of increased reproductive investment, secondary females should suffer from reduced survival and lifetime reproductive success, but previous studies provided only weak support for this hypothesis. We used 7 years of data to study the fitness of female collared flycatchers Ficedula albicollis in relation to mating status by estimating survival and lifetime reproductive success. Taking differences in recapture probability into account, a mark-recapture analysis revealed that females observed at least once to breed as secondary female had higher survival than other females. This relationship was not confounded by laying date, because when we assessed the impact of laying date on survival, we found similar survival patterns. Females of polygynous males had reduced breeding success in terms of number of young fledged during the current reproductive event. However, during their lifetime females found at least once in primary or secondary mating status produced significantly more eggs, and at least the same number of fledglings and recruits as monogamous females. Thus, in the collared flycatcher, females of polygynously mated males seem to suffer from mating status during the most recent reproductive event, but considering survival and lifetime reproductive success, the apparently disadvantageous mating event is not necessarily associated with reduced residual reproductive value.     

Newts under siege: range expansion of Triturus pygmaeus isolates populations of its sister species

The newt species Triturus marmoratus and Triturus pygmaeus are both present in central Portugal where they have parapatric distributions. We used four genetic markers to determine which species was present in 31 populations. In the centre of the study area we found a T. marmoratus enclave. Despite small interpopulation distances, hybridization is locally rare. We built several models to try to explain this distribution using environmental data. The best model, chosen by Akaike's Information Criterion, relates the presence of T. marmoratus with the temperature in July, the relief of the landscape, and a higher use of the land for orchards. The current distribution can best be explained by T. pygmaeus expanding north and replacing T. marmoratus , the latter only persisting where ecological conditions are relatively favourable.     

A survival cost to mating in a polyandrous butterfly, Colias eurytheme

Adaptations that enhance fitness in one sex may be harmful to members of the opposite sex and lead to antagonistic coevolution between the sexes. In fruit flies, for example, selection for fertilization success has rendered the male ejaculate slightly toxic to females. Here we investigated whether mating imposes a cost upon female fitness in a polyandrous pierid butterfly ( Colias eurytheme ) by comparing life history traits between once-mated females and virgins. Mated females laid relatively more eggs early in their adult life, but suffered a reduction in longevity relative to virgins held under identical experimental conditions. The effect of mating on female survivorship was statistically independent of lifetime and early life fecundity. Moreover, lifetime fecundity co-varied positively with longevity across all females, and across females within each treatment group, hence there was no phenotypic trade-off between survival and reproduction. These results suggest that the observed longevity difference between virgin and mated females represents a true cost of mating, possibly arising from a toxic side effect of the male ejaculate. However, irrespective of this cost, virgin and mated females laid an equivalent lifetime number of eggs. Female C. eurytheme are also known to use nutrients from the male ejaculate to supplement their reproductive output, hence it is presently unclear how the observed longevity cost may have influenced the evolution of lifetime mating schedules in this polyandrous species.     

Reproductive interference between Rana dalmatina and Rana temporaria affects reproductive success in natural populations

Experimental evidence suggests that reproductive interference between heterospecifics can seriously affect individual fitness; support from field studies for such an effect has, however, remained scarce. We studied reproductive interference in 25 natural breeding ponds in an area where two ranid frogs, Rana dalmatina and Rana temporaria, co-occur. The breeding seasons of the two species usually overlap and males of both species are often found in amplexus with heterospecific females, even though matings between heterospecifics produce no viable offspring. We estimated species abundance ratios based on the number of clutches laid and evaluated fertilization success. In ponds with low spatial complexity and a species abundance ratio biased towards R. temporaria, the average fertilization success of R. dalmatina eggs decreased, while this relationship was not detectable in spatially more complex ponds. Fertilization success of R. temporaria did not decrease with increasing relative numbers of heterospecifics. This asymmetry in fitness effects of reproductive interference may be attributed to R. temporaria males being more competitive in scramble competition for females than R. dalmatina males. Our study is among the first to demonstrate that in natural breeding populations of vertebrates interference among heterospecifics has the potential to substantially lower reproductive success at the population level, which may in turn affect population dynamics.     

Predation and competition within an assemblage of larval newts (Triturus)

The impact of crested newts (Triturus cristatus) on the smaller-bodied palmate and smooth newts (T helveticus and T vulgaris) was studied during the larval stages using a combination of field and laboratory experiments In pond enclosures T cristatus larvae had no effect on the two smaller species over the first four weeks of development By eight weeks, however. T cristatus had achieved a size advantage which enabled it to eliminate T helveticus and severely reduce T vulgaris by predation In laboratory trials under food-limited conditions, T helveticus and T vulgaris were slightly smaller when raised with T cristatus, suggesting that this predatory effect was complemented by interspecific competition during early development Predation of the smaller species started when T cristatus reached a threshold size of c 27 mm No reciprocal effects on T cristatus growth or survival were observed Although T cristatus may be a significant predator of congeneric species in natural ponds, other factors, such as differences in microhabitat selection, higher-order predator-prey interactions and the occasional desiccation of pond habitats may facilitate coexistence between the species     

Cascading costs of reproduction in female house wrens induced to lay larger clutches

In many species, females produce fewer offspring than they are capable of rearing, possibly because increases in current reproductive effort come at the expense of a female's own survival and future reproduction. To test this, we induced female house wrens (Troglodytes aedon) to lay more eggs than they normally would and assessed the potential costs of increasing cumulative investment in the three main components of the avian breeding cycle – egg laying, incubation and nestling provisioning. Females with increased clutch sizes reared more offspring in the first brood than controls, but fledged a lower proportion of nestlings. Moreover, nestlings of experimental females were lighter than those of control females as brood size and prefledging mass were negatively correlated. In second broods of the season, when females were not manipulated, experimental females laid the same number of eggs as controls, but experienced an intraseasonal cost through reduced hatchling survival and a lower number of young fledged. Offspring of control and experimental females were equally likely to recruit to the breeding population, although control females produced more recruits per egg laid. The reproductive success of recruits from broods of experimental and control females did not differ. The manipulation also induced interseasonal costs to future reproduction, as experimental females had lower fecundity than controls when breeding at least 2 years after having their reproductive effort experimentally increased. Finally, females producing the modal clutch size of seven eggs in their first broods had the highest lifetime number of fledglings.     

Influence of microbe-associated parthenogenesis on the fecundity ofTrichogramma deion andT. pretiosum

Microbe-associated parthenogenesis (thelytoky) has been discovered in nineTrichogramma species, parasitoids of mainly lepidopteran eggs. Parthenogenetic and bisexual conspecifics co-occur in many field populations. As an initial step to understand the dynamics of these two reproductive strategies we studied the effect of microbe-associated parthenogenesis on fecundity. The fecundity of two parthenogenetic isofemale lines ofT. pretiosum and one ofT. deion was compared with bisexual lines derived from them by antibiotic treatment. In all three cases parthenogenetic females were less fecund over their lifetime than bisexual females. Also, parthenogenetic females produced fewer daughters in two cases and in one case a similar number of daughters as their respective bisexual counterparts. The lack of mating and insemination was excluded as an explanation for the reduced fecundity of parthenogenetic females, because mated and virgin parthenogenetic females produce the same number of offspring. Antibiotic treatment can also be excluded because females of field-collected bisexual line treated with antibiotics produced the same number of offspring as untreated females. The reduced fecundity of parthenogenetic females was caused by a lower number of eggs being laid rather than by a greater developmental mortality. Parthenogenetic females produced less daughters than bisexual females when host availability was not limiting, but when host availability was severely limited, parthenogenetic females produced more daughters than the bisexual females.     

Population ecology of Trituras cristatus and T. vulgaris (Urodela) in SW Sweden

The population ecology of newts was investigated between 1969 and 1974 in two localities near Gothenburg, SW Sweden: the Gunnebo park pond (about 300 m²) where Triturus cristatus Laurenti and T. vulgaris L. are sympatric, and a rock-pool (6 m²) in Billdal with only T. vulgaris. At Gunnebo, a population of about 350 breeding T. cristatus was found with about as many males as females but males being more aquatic than females. An annual survival of 0.7–0.8 was estimated for the adults. The T. vulgaris population at the same locality was estimated to about 250–300 breeding adults with a sex ratio possibly in favour of males. The survival of adults was found to be extremely low and a very small percent of the adults seems to breed more than once. The Billdal T. vulgaris population was estimated to contain nearly 70 breeding adults with a sex ratio very near to 1:1. The annual survival of adults was found to be 0.5. The different survival of the two T. vulgaris populations are discussed with particular reference to predation. The age at which newts breed for the first time seems to vary; for T. vulgaris five years may well be the normal age. Factors that may limit the sizes of the populations, possible reasons for differences in frequency of occurrence in water, and possible predators are discussed.     

Flight and Oviposition Behavior of the Adult Maritime Ringlet (Coenonympha nipisiquit McDunnough) Females in Response to Microhabitat

Maritime ringlet butterflies (Coenonympha nipisiquit McDunnough), an endangered species in Canada, inhabit salt marshes, which consist of microhabitat mosaics with varied larval survival rate. These microhabitats may influence the movement and reproductive behaviors of females, which in turn may affect population dynamics. I recorded behaviors and locations of females every minute with a GPS rover and calculated their move lengths and turning angles. Move lengths did not change in response to microhabitats, although turning angles became larger near bodies of water with sparse vegetation. Females spent a longer time in one location and oviposited more often where the principal larval host, Spartina patens (Aiton) Muhl., is abundant, regardless of larval survival rate. Older females tended to initiate flight more readily than younger females and spent more time flying and nectaring. Younger females were more fecund and spent a longer time at one location. Because young females tend to be less mobile and more fecund, the majority of oviposition should take place near eclosion sites. However, some eggs will be laid away from microhabitats favorable to larval survival when older females become mobile and move out of their natal microhabitats. Because it seems to have little potential to colonize new habitat on its own, monitoring population dynamics and habitat quality will be crucial for the persistence and recovery of this rare species.     

Microhabitat selection and feeding relations of smooth and warty newts, Triturus vulgaris and T. cristatus, at an upland pond in mid-Wales

The utilization of microhabitat and food resources by Triturus vulgaris and T. cristatus was studied in an upland pond in mid-Wales. From April to June T. vulgaris was more evenly distributed across the pond than T. cristatus , which showed a preference for the middle of the pond and the bottom of the water column. From July to September however, when most T. vulgaris had left the pond, T cristatus was evenly distributed within the water column and a much higher proportion was captured around the shorelines. Both species appear to be generalist predators with diets limited by prey size. Zooplankton were the most important prey for T. vulgaris , while leeches formed the bulk of the diet of T. cristatus . However, T. cristatus did not select larger-sized zooplankton than T. vulgaris . Large body size therefore enables T. cristatus to consume a wider range of prey sizes than T. vulgaris . Microhabitat niche overlap was greater than feeding niche overlap between the species.     

The effects of dominance rank and group size on female lifetime reproductive success in wild long-tailed macaques,Macaca fascicularis

Demographic changes were recorded throughout a 12-year period for three social groups ofMacaca fascicularis in a natural population at Ketambe (Sumatra, Indonesia). We examined the prediction that females' lifetime reproductive success depended on dominance rank and group size. Average birth rate was 0.53 (184 infants born during 349 female years). For mature females (aged 8–20 yr) birth rate reflected physical condition, being higher in years with high food availability and lower in the year following the production of a surviving infant. High-ranking females were significantly more likely than low-ranking ones to give birth again when they did have a surviving offspring born the year before (0.50 vs 0.26), especially in years with relatively low food availability (0.37 vs 0.10). Controlled comparisons of groups at different sizes indicate a decline in birth rate with rroup size only once a group has exceeded a certain size. The dominance effect on birth rate tended to be strongest in large groups. Survival of infants was rank-dependent, but the survival of juveniles was not. There was a trend for offspring survival to be lower in large groups than in mid-sized or small groups. However, rank and group size interacted, in that rank effects on offspring survival were strongest in large groups. High-ranking females were less likely to die themselves during their top-reproductive years, and thus on average had longer reproductive careers. We estimated female lifetime reproductive success based on calculated age-specific birth rates and survival rates. The effects of rank and group size (contest and scramble) on birth rate, offspring survival, age of first reproduction for daughters, and length of reproductive career, while not each consistently statistically significant, added up to substantial effects on estimated lifetime reproductive success. The group size effects explain why large groups tend to split permanently. Since females are philopatric in this species, and daughters achieve dominance rank positions similar to their mother, a close correlation is suggested between the lifetime reproductive success of mothers and daughters. For sons, too, maternal dominance affected their reproductive success: high-born males were more likely to become top-dominant (in another group). These data support the idea that natural selection has favored the evolution of a nepotistic rank system in this species, even if the annual benefits of dominance are small.     

Male genotype affects female fitness in a paternally investing species

Male nutrient provisioning is widespread in insects. Females of some species use male-derived nutrients for increased longevity and reproductive output. Despite much research into the consequences of paternal nutrient investment for male and female fitness, the heritability, and therefore the potential of this trait to respond to selection, has rarely been examined. Males of several butterfly species provide the female with nutrients in the spermatophore at mating. Females of the green-veined white butterfly Pieris napi (Lepidoptera: Pieridae) use male donations both for developing eggs (resulting in higher lifetime fecundity of multiply mated females), but also for their somatic maintenance (increasing longevity). Using half-sib, father-son regression and full-sib analyses, I showed that paternal nutrient investment is heritable, both in terms of the absolute but also the relative size of the spermatophore (controlling for body size). Male size and spermatophore size were also genetically correlated. Furthermore, a separate study showed male genotype had a significant effect on female longevity and lifetime fecundity. In contrast, male genotype had no influence on the immediate egg-laying rate of females following mating, suggesting limited scope for male manipulation of immediate female oviposition. These results indicate that females may derive both direct (increased lifetime fecundity and longevity) and indirect (sons with greater reproductive success) fitness benefits from paternal nutrient donations in this species.