Potential Reproductive Lifespan Research Articles

Impacts of horticultural environments on Rhinella arenarum (Anura, Bufonidae) populations: exploring genocytotoxic damage and demographic life history traits.

Horticulture poses a significant ecological risk, as agrochemicals are applied more frequently and in larger quantities per unit of production compared to extensive crop fields. The native amphibian Rhinella arenarum serves as a reliable bioindicator of environmental health. This study aimed to assess genocytotoxic damage and demographic life history traits of R. arenarum inhabiting horticultural environments. Sampling was conducted in suburban sites in central Argentina: H1 and H2 (sites associated with horticultural activity) and a reference site, RS. Environmental parameters were recorded, and the frequency of micronuclei (Mn), nuclear abnormalities (ENA), and indicators of cytotoxic damage were determined in tadpoles and adults. Demographic variables (age at maturity, longevity, potential reproductive lifespan, size at maturity, modal lifespan) were calculated. The highest nitrate and phosphate values, along with low dissolved oxygen values, were recorded at sites H1 and H2. Organisms inhabiting horticultural environments exhibited higher frequencies of Mn and ENA, surpassing those recorded in previous studies on tadpoles from sites with extensive crop production. Size at maturity and age at maturity of females, as well as size at maturity, longevity, mean age, and mean adult SVL of males, were lower in horticultural sites. The results support the hypothesis that anuran populations inhabiting horticultural environments demonstrate a diminished health status attributed to subpar environmental quality. Monitoring endpoints at different biological levels provides information on the ecotoxicological risk for amphibians and human populations inhabiting nearby areas.

Age and growth in an anuran hybrid zone: Fitness-related traits of the diploid/polyploid ground frog complex (genus Odontophrynus) from central Argentina

Diploid Odontophrynus cordobae and tetraploid Odontophrynus americanus coexist in syntopy in central Argentina, and recently a hybrid zone between them with numerous triploid individuals has been reported. Furthermore, hybrid polyploids with odd numbers of chromosome sets often exhibit low viability and fertility. Our aim was to test differences in age-related life history aspects influencing fitness in hybrids and their parental species, by comparing demographic and growth-related parameters. The mean age and snout-vent length at sexual maturity and adulthood did not differ significantly among taxa. Longevity and potential reproductive lifespan were one year higher in O. cordobae than O. americanus and hybrids. We did not find significant differences in growth parameters among taxa. Our study shows similar patterns of size and demographics parameters. Triploid hybrids have a similar longevity and viability to parental species. The age structure of triploids indicates that the hybridization process has a temporal continuity. The lack of observed differences among taxa in age-related life-history aspects indicates that hybrid fitness does not seem to differ from that of the parental species, and reinforce the idea of a potential fertility of hybrids. Besides, our results suggests that hybrids do not direct their resources more to growth than to reproduction, as would be expected if they were infertile. However, further studies are necessary to determine the reproductive capacity of the hybrids.

Demographic life history traits in a population of a critically endangered species, Darevskia dryada (Darevsky & Tuniyev, 1997)

Abstract Knowing the age structure of endangered species is important in order to contribute to future conservation studies for such species. In this context, we investigated age structure, age at sexual maturity, potential reproductive lifespan and longevity in a population of the Charnali lizard, Darevskia dryada, an endangered species from Turkey. The results show that the Charnali lizard has a longer life span than other lizards of the genus Darevskia that live in the same region. We estimated that these lizards attain their sexual maturity at the age of one or two years and the potential reproductive life span for males and females is six and five years, respectively. As in many other lizards, the Charnali lizard exhibited a low-level male-biased sexual dimorphism in terms of increased size. We believe that this study, in which prior information related to the Charnali lizard is shared, will contribute to future conservation activities for this critically endangered species.

Sex- and cohort-specific life-history strategies in Mongolian gerbils (Meriones unguiculatus)

Information on life-history traits is crucial for understanding rodent evolution, ecology, and behavioral strategies. Here, we report on the results from a 4-year study that collected data on the sexual and seasonal cohort (winter C1, spring C2, and summer C3) life-history traits of Mongolian gerbils (Meriones unguiculatus) maintained in a natural enclosure, using monthly live trapping, in Inner Mongolia (China). We found no sexual differences in the observed longevity, age of maturity, potential reproductive life span, or dispersal in the year of their birth, apart from a male-biased dispersal after gerbils overwintered as adults. Nevertheless, we did find cohort-specific life-history patterns in the above traits; for example, the C1 females matured at a significantly earlier age than did the C2 and C3 females, while the C3 gerbils commonly delayed their reproduction to the following year. Moreover, 21.7% of C1 and 6.1% of C2 females bred more than one litter, yet none of the C3 females did so during their birth-year breeding season. The average number of litters per female of C1 was greater than that of either C2 or C3 in their birth-year breeding season. Our results suggest that sex-specific life history traits may align with the predictions of sexual selection and the monogamy system hypothesis in Mongolian gerbils. In addition, the seasonal cohort-specific life-history traits revealed here lend support to the hypothesis of an adaptive switching behavior—from fast to slow development in the later-born gerbils—as opposed to the hypothesis of direct environmental limitation, although the slight inter-annual variation detected is consistent with the precipitation constraints.

Geographical variations in adult body size and reproductive life history traits in an invasive anuran, Discoglossus pictus

Variability in life history traits positively affects the establishment and expansive potential of invasive species. In the present study, we analysed the variation of body size in seven populations − two native and five invasive − of the painted frog (Discoglossus pictus, Anura: Discoglossidae), native to North Africa and introduced in southern France and the north-east of the Iberian Peninsula. Other life history traits (age at maturity, size at maturity, longevity, median age and potential reproductive lifespan) were analysed in a native and an invasive population. We observed geographic variations in adult body size, related mainly to mean annual precipitation. Thus, populations had greater body size as mean annual precipitation increased, resulting in bigger specimens in the invasive populations. Adult body size and growth rates also varied between sexes in all studied populations, with males significantly larger than females. Age distribution varied between native (1–5 years) and invasive populations (2–4 years) and also between sexes. Our results suggest that higher precipitation promotes faster growth rates and larger adult body size that could facilitate the successful establishment of invasive populations.

Assessing reproductive resilience: an example with South Atlantic red snapper Lutjanus campechanus

We developed a conceptual model of reproductive resilience based on spatio-tempo- ral diversity in spawning activity and the 'big old fat fecund female fish' effect, i.e., trends in reproductive traits with size and age. We chose red snapper Lutjanus campechanus as our case study, as this species is highly fecund, currently overfished, and long-lived (50+ yr). The intrinsic reproductive resilience of red snapper was assessed in terms of spawning site distribution, vari- ability in time of spawning, and potential reproductive lifespan. To assess how age truncation might erode reproductive resilience, we evaluated the strength of the relationship between size and age and the following traits: spawning habitat, reproductive timing, batch fecundity, and egg quality. Few fish were older than 7 yr. Although younger fish occurred in a more restricted range of depths, there was no trend between size or age and depth. Spawning activity was well distrib- uted over space and time, with actively spawning females collected at 92 of 195 sampling sites over an extended spawning season. Larger, older females exhibited longer spawning periods and higher batch fecundities, but neither greater spawning frequency nor egg dry weight. The ratio of the effective to predicted reproductive lifespan at maximum sustainable yield was 31%. Many parameters estimated in this study are common to fish reproductive studies, but we hope that inte- grating them into a reproductive resilience framework will help focus the need for research on the underlying relationships between reproductive traits and stock productivity.

Large‐scale variation of size‐ and age‐related life‐history traits in the common frog: a sensitive test case for macroecological rules

AbstractThe potential causes underlying geographical variation of 12 age‐ and size‐related life‐history traits were studied in the common frog Rana temporaria. The meta‐analysis was based on own field data obtained in the Austrian Alps and additionally on published studies on 35 populations covering the whole range of latitudinal, longitudinal and altitudinal distribution. This extensive dataset allowed for co‐variance analyses evaluating the statistical support for five hypotheses on large‐scale trait variation derived from general macroecological rules. Contrary to Bergmann's rule, adult frogs' body size variation was unrelated to latitude (and altitude), but co‐varied with age as expected for a species that grows indeterminately. Unlike the prediction of Rensch's rule, the slight female‐biased sexual size dimorphism (SSD) did not differ significantly among populations with small and large average female size. SSD increased with altitude, but did not co‐vary with latitude, longitude and age, disagreeing with the predictions of the differential‐plasticity hypothesis. Common frogs at higher altitudes and latitudes reached reproductive maturity at significantly older ages and enjoyed an increased longevity as well. However, potential reproductive lifespan increased significantly only with altitude, compensating for the smaller clutches relative to body size in alpine populations. In conclusion, body size variation of common frogs does not actually mirror geographical gradients, but differences in age, a factor unconsidered in Bergmann's and Rensch's rules. Large‐scale environmental gradients are therefore good predictors of age‐related traits. Combining the local co‐variation of the single traits age, body size, clutch size and reproductive lifespan to calculate the resulting female lifetime fecundity (FLF), surprisingly little variation of the derived trait FLF is observed across the geographical range of the common frog. The ultimate cause of variation in age‐ and size‐related life‐history traits seems to be the selection for an optimal FLF.

Altitudinal variation of demographic life-history traits does not mimic latitudinal variation in natterjack toads (Bufo calamita)

In anuran amphibians, age- and size-related life-history traits vary along latitudinal and altiudinal gradients. In the present study, we tested the hypothesis that altitudinal and latitudinal effects cause similar responses by assessing demographic life-history traits in nine Bufo calamita populations inhabiting elevations from sea level to 2270m. Skeletochronologically determined age at maturity and longevity increased at elevations exceeding 2000m, but female potential reproductive lifespan (PRLS) did not increase with altitude, as it did with latitude. Integrating the available evidence, it was found that lifetime fecundity of natterjacks decreased at the upper altitudinal range because PRLS was about the same as in lowland populations but females were smaller. In contrast, small size of northern females was compensated for by increased PRLS which minimised latitudinal variation of lifetime fecundity. Thus, this study provides evidence that altitudinal effects on life-history traits do not mimic latitudinal effects. Life-history trait variation along the altitudinal gradient seems to respond directly to the shortening of the annual activity period. As there is no evidence for increasing mortality in highland populations, reduced lifetime fecundity may be the ultimate reason for the natterjacks’ inability to colonise elevations exceeding 2500m.

Proximate mechanisms determining size variability in natterjack toads

In the toad Bufo calamita, among-population variation of size follows roughly a converse Bergmann cline, but populations exist that do not fit this pattern. We propose that latitudinal body size variation is a byproduct of adaptive covariation among the life-history traits juvenile growth rate, longevity and lifetime fecundity. We choose five populations (two in Andalusia, two in Catalonia and one in Rhineland-Palatinate) representing a variation of adult size from 39 mm to 95 mm snout–vent length, a latitudinal gradient from 37 to 50° and an altitudinal gradient from sea level to 420 m. Skeletochronology was used to estimate the age-related life-history traits of 313 toads and their lifetime pattern of growth. At southern latitudes, toads matured and reproduced earlier than those at northern latitudes, but had a reduced potential reproductive lifespan due to lower longevity. Age-adjusted adult size depended mainly on the size achieved between metamorphosis and first hibernation or aestivation, which in turn was influenced by local factors. We propose that first-year size corresponds to the duration of the aboveground activity period, temperature during the activity period and the type of shelter sites and hibernacula available in the habitat. After attaining sexual maturity, the growth rates did not differ among populations. Interactions of multiple environmental factors during the first year of life determine age at maturity, adult size and size variation among populations. Local body size and potential reproductive lifespan covary to optimize lifetime fecundity throughout the geographical range. The presence of a small-sized population in southern Spain does not fit the pattern predicted by a converse Bergmann cline, but is compatible with the hypothesis that body size variation among B. calamita populations may be the evolutionary byproduct of optimized lifetime fecundity.

Life-history traits in green toad (Bufo viridis) populations: indicators of habitat quality

Five life-history traits (age and size at maturity, longevity, potential reproductive life span, age-dependent growth rate) were investigated in four Bufo viridis Laurenti, 1768 (= Pseudepidalea viridis (Laurenti, 1768)) populations that inhabited localities at similar altitude (60–100 m above sea level) and latitude (50°N–51°N, Germany), but that differed in habitat quality (i.e., human land use within a radius of 1 km around the breeding site). The age of 374 males and of 127 females collected during the breeding period was estimated using skeletochronology on phalange bones. We tested the hypothesis that sex and habitat quality account for detectable amounts of local variation in life-history traits. Significant sexual size dimorphism was present in all populations. Gender-specific variation in size was mainly accounted for by age, but also to a minor extent by habitat quality. In males, age at maturity varied between 1 and 3 years and was the only life-history trait that was significantly related to the intensity of human land use. In contrast, land-use indices covaried significantly with female longevity (6–15 years) and potential reproductive life span (5–12 years). Our pilot study suggests that, in B. viridis, life-history traits derived from the local age structure may be useful as indicators of habitat quality.

Demographic life history traits of reproductive natterjack toads (Bufo calamita) vary between northern and southern latitudes

AbstractDemographic life history traits were investigated in three Bufo calamita populations in Germany (Rhineland-Palatinate: Urmitz, 50°N; 1998-2000) and Spain (Catalonia: Balaguer, Mas de Melons, 41°N; 2004). We used skeletochronology to estimate the age as number of lines of arrested growth in breeding adults collected during the spring breeding period (all localities) and during the summer breeding period (only Urmitz). A data set including the variables sex, age and size of 185 males and of 87 females was analyzed with respect to seven life history traits (age and size at maturity of the youngest first breeders, age variation in first breeders, longevity, potential reproductive lifespan, median lifespan, age-size relationship). Spring and summer cohorts at the German locality differed with respect to longevity and potential reproductive lifespan by one year in favour of the early breeders. The potential consequences on fitness and stability of cohorts are discussed. Latitudinal variation of life history traits was mainly limited to female natterjacks in which along a south-north gradient longevity and potential reproductive lifespan increased while size decreased. These results and a review of published information on natterjack demography suggest that lifetime number of offspring seem to be optimized by locally different trade-offs: large female size at the cost of longevity in southern populations and increased longevity at the cost of size in northern ones.

ALTITUDINAL VARIATION IN THE AGE AT MATURITY, LONGEVITY, AND REPRODUCTIVE LIFESPAN OF ANURANS IN SUBTROPICAL QUEENSLAND

Skeletochronology has been widely and successfully used to age temperate amphibians, enabling geographic comparisons of longevity and the age at maturity. To date, however, there have been very few similar studies conducted using skeletochronology in tropical or sub-tropical amphibians. In this study, we examined the applicability of skeletochronology for aging four sub-tropical anuran species (Litoria chloris, L. lesueuri, L. pearsoniana, and Mixophyes fleayi) that occur across a range of altitudes in southeast Queensland, Australia. We then used reliable estimates to examine altitudinal variation in longevity, age at maturity (AM), and potential reproductive lifespan (PRLS) for each species. Skeletochronology was successful in three of the four species. The age of L. lesueuri individuals from low altitude sites could not be reliably estimated due to extended activity seasons. On average, females were older than males in L. chloris, L. pearsoniana, and M. fleayi and were also older when breeding for the first time. There was, however, no significant difference in the PRLS between males and females within any of the three species. There were trends towards greater longevity and older AM in high altitude populations of all three species; however, there was no significant altitudinal variation in PRLS in any of the species. Our results suggest little intraspecific variation in the number of years that individuals of the four species are capable of breeding, regardless of gender, geographic location, longevity, and AM.