Palaeohistology reveals a slow pace of life for the dwarfed Sicilian elephant

The 1-m-tall dwarf elephant Palaeoloxodon falconeri from the Pleistocene of Sicily (Italy) is an extreme example of insular dwarfism and epitomizes the Island Rule. Based on scaling of life-history (LH) traits with body mass, P. falconeri is widely considered to be ‘r-selected’ by truncation of the growth period, associated with an early onset of reproduction and an abbreviated lifespan. These conjectures are, however, at odds with predictions from LH models for adaptive shifts in body size on islands. To settle the LH strategy of P. falconeri, we used bone, molar, and tusk histology to infer growth rates, age at first reproduction, and longevity. Our results from all approaches are congruent and provide evidence that the insular dwarf elephant grew at very slow rates over an extended period; attained maturity at the age of 15 years; and had a minimum lifespan of 68 years. This surpasses not only the values predicted from body mass but even those of both its giant sister taxon (P. antiquus) and its large mainland cousin (L. africana). The suite of LH traits of P. falconeri is consistent with the LH data hitherto inferred for other dwarfed insular mammals. P. falconeri, thus, not only epitomizes the Island Rule but it can also be viewed as a paradigm of evolutionary change towards a slow LH that accompanies the process of dwarfing in insular mammals.

Age at first reproduction in wolves: different patterns of density dependence for females and males

Age at first reproduction constitutes a key life-history trait in animals and is evolutionarily shaped by fitness benefits and costs of delayed versus early reproduction. The understanding of how intrinsic and extrinsic changes affects age at first reproduction is crucial for conservation and management of threatened species because of its demographic effects on population growth and generation time. For a period of 40 years in the Scandinavian wolf ( Canis lupus ) population, including the recolonization phase, we estimated age at first successful reproduction (pup survival to at least three weeks of age) and examined how the variation among individuals was explained by sex, population size (from 1 to 74 packs), primiparous or multiparous origin, reproductive experience of the partner and inbreeding. Median age at first reproduction was 3 years for females ( n = 60) and 2 years for males ( n = 74), and ranged between 1 and 8–10 years of age ( n = 297). Female age at first reproduction decreased with increasing population size, and increased with higher levels of inbreeding. The probability for males to reproduce later first decreased, reaching its minimum when the number of territories approached 40–60, and then increased with increasing population size. Inbreeding for males and reproductive experience of parents and partners for both sexes had overall weak effects on age at first reproduction. These results allow for more accurate parameter estimates when modelling population dynamics for management and conservation of small and vulnerable wolf populations, and show how humans through legal harvest and illegal hunting influence an important life-history trait like age at first reproduction.

Reproductive biology of Penaeus kerathurus (Forskål, 1775) (Decapoda: Penaeidae) in the Sea of Marmara, Turkey

One of the economically important species is Penaeus kerathurus (Forskål, 1755), which is widespread in the Mediterranean ecosystem. This paper presents results of research on reproductive biology of Penaeus kerathurus in the Sea of Marmara. A total of 1404 specimens were dissected to determine the maturity stages, reproduction time, and length at first reproduction. The female-to-male ratio was 1:0.9. A high percentage of mature females was determined in April, May and July. Moreover, the value of the gonadosomatic index (GSI) decreased after July. The spawning period was observed between April and July, and its intensity increased in July. The carapace length at first sexual maturity was determined to be 39 mm.

Breeding transients in capture–recapture modeling and their consequences for local population dynamics

Standard procedures for capture–mark–recapture modelling (CMR) for the study of animal demography include running goodness-of-fit tests on a general starting model. A frequent reason for poor model fit is heterogeneity in local survival among individuals captured for the first time and those already captured or seen on previous occasions. This deviation is technically termed a transience effect. In specific cases, simple, uni-state CMR modeling showing transients may allow researchers to assess the role of these transients on population dynamics. Transient individuals nearly always have a lower local survival probability, which may appear for a number of reasons. In most cases, transients arise due to permanent dispersal, higher mortality, or a combination of both. In the case of higher mortality, transients may be symptomatic of a cost of first reproduction. A few studies working at large spatial scales actually show that transients more often correspond to survival costs of first reproduction rather than to permanent dispersal, bolstering the interpretation of transience as a measure of costs of reproduction, since initial detections are often associated with first breeding attempts. Regardless of their cause, the loss of transients from a local population should lower population growth rate. We review almost 1000 papers using CMR modeling and find that almost 40% of studies fitting the searching criteria (N = 115) detected transients. Nevertheless, few researchers have considered the ecological or evolutionary meaning of the transient phenomenon. Only three studies from the reviewed papers considered transients to be a cost of first reproduction. We also analyze a long-term individual monitoring dataset (1988–2012) on a long-lived bird to quantify transients, and we use a life table response experiment (LTRE) to measure the consequences of transients at a population level. As expected, population growth rate decreased when the environment became harsher while the proportion of transients increased. LTRE analysis showed that population growth can be substantially affected by changes in traits that are variable under environmental stochasticity and deterministic perturbations, such as recruitment, fecundity of experienced individuals, and transient probabilities. This occurred even though sensitivities and elasticities of these parameters were much lower than those for adult survival. The proportion of transients also increased with the strength of density-dependence. These results have implications for ecological and evolutionary studies and may stimulate other researchers to explore the ecological processes behind the occurrence of transients in capture–recapture studies. In population models, the inclusion of a specific state for transients may help to make more reliable predictions for endangered and harvested species.

Asynchrony of actuarial and reproductive senescence: a lesson from an indeterminate grower

Evolutionary theories relating to aging predict that patterns of actuarial and reproductive senescence should be aligned, with a common onset of senescence set at the age of first reproduction. However, a few empirical studies reported asynchrony between actuarial and reproductive senescence. This asynchrony is expected to be particularly pronounced in organisms with indeterminate growth. Yet, this process is still poorly documented due to the lack of long-term demographic data on known-aged individuals. We investigated the asynchrony of actuarial and reproductive senescence in the European whip snake, Hierophis viridiflavus, an oviparous colubrid with indeterminate growth. Using demographic data collected over a 29-year period, we showed that females did not experience any fecundity loss late in life. In contrast, they suffered from an early, severe actuarial senescence. Our findings thus revealed a pronounced asynchrony in actuarial and reproductive senescence processes, a phenomenon that could be widespread across the tree of life.

Effects of non-toxic filamentous cyanobacteria isolated from tri an reservoir on Daphnia

This study is aimed to examine whether the presence of non-toxic filamentous cyanobacteria can cause toxic effects on Daphnia magna. Six strains of Oscillatoria perornata were isolated from the Tri An Reservoir and cultured in our laboratory for investigation. The results revealed that all strains were negative with the mcyA moleculer marker. The high performance liquid chromatography (HPLC) results showed that toxin was not detected in their culture products, indicating that these strains corresponded to non-toxin producing strains. However, the results of chronic assay indicated that these non-toxin producing O. perornata conferred toxic effects on the tested animals. The age at first reproduction of D. magna was delayed and the survival of D. manga decreased in proportional with the increase of the density of cells of O. perornata exposed. Significant differences in the life history responses were observed for D. mangna exposed to O. perornata. These results suggested that bioactive secondary metabolites other than microcystins produced by the filamentous cyanobacteria O. perornata may contribute to the toxic effects on Daphnia. Besides cyanotoxins, other secondary metabolites must be taken into account when investigating the toxic effects of cyanobacteria.