High Reproductive Effort Research Articles

Growth-survival trade-offs and the restoration of non-forested open ecosystems

The growth-survival trade-off has been extensively documented for phanerophyte species, whereas there is little evidence for non-phanerophyte species. However, information on the growth-survival trade-offs in non-phanerophyte species could be of great use in non-forested open ecosystem restoration by providing insights for plant production and transplantation, thus impacting the planning of cost-effective restoration actions. In this study, we explored the relationship between growth and survival of individual plants of non-phanerophyte species used in a coastal dune restoration project, and we investigated whether plant functional traits explained patterns of trade-off between growth and survival. We monitored 355 individual plants of 13 perennial non-phanerophyte species belonging to foredune and transition dune communities every 30 days after planting and calculated relative growth and survival rates. In addition, we regressed the relationship between growth and survival on values of leaf and floral traits. We found that, besides being a widely recognised axis of life history variation in phanerophyte species, the growth-survival trade-off can also be observed in perennial non-phanerophyte species. Species of different coastal dune communities (i.e., foredune vs. transition dune communities) differed with respect to the growth-survival trade-off, with plant species of foredune communities exhibiting higher growth but lower survival rates than plant species of transition dune communities. Leaf dry matter content and mean number of floral displays explained species position on the growth-survival trade-off axis; species with relatively high growth and low survival rates exhibited an acquisitive strategy, with low values of leaf dry matter content, but also a low sexual reproductive effort, as revealed by low number of floral displays. In contrast, plant species with relatively low growth and high survival rates exhibited a conservative strategy but also high sexual reproductive effort, suggesting that trade-offs occur in resource allocation among vegetative and reproductive plant structures. The trade-off we found between growth and survival in perennial non-phanerophyte species provides useful insights for planning cost-effective ecosystem restoration actions of non-forested open ecosystems, especially when the actions are nature-based and involve planting individual plants. The results of this study suggest that individual plant production for coastal dune restoration should disproportionately target plant species of foredune communities because they have low survival rates associated with low sexual reproductive effort. Planning plant production based on ecological knowledge of plant species’ growth and survival after planting in the field could help achieve restoration goals while meeting project cost-effectiveness requirements.

Modelling differences in reproductive effort between iteroparous and semelparous reproductive strategies in Bromeliaceae

Abstract Quantifying reproductive effort (RE), the trade-off between devoting resources to reproduction versus individual growth, in plants presents a number of challenges. Of particular interest is comparing RE between reproductive strategies, such as those in Bromeliaceae: semelparous, where individuals undergo a one-time and subsequently lethal sexual reproductive event, versus iteroparous, where individuals reproduce sexually multiple times by producing clonal offshoots called pups. We introduce a dynamic model of vegetative and reproductive growth in long-lived Bromeliaceae rosettes accounting for the allocation of resources over developmental time. We compare multiple definitions of RE in semelparous and iteroparous Bromeliaceae at critical times during development and over the entire reproductive life of the individual. While others have posited that semelparous taxa exhibit higher RE than comparable iteroparous taxa, our results indicate that this will only occur in limited circumstances: when RE is calculated over the lifespan of a rosette started from seed, semelparous RE is greater when pup mass is accounted for as if it were purely vegetative; or when RE is calculated over the lifespan of the genetic individual, semelparous RE is greater when the ratio of vegetative to inflorescence mass in each pup is greater than that of the originating rosette started from seed.

When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility?

In birds with extrapair mating, older males usually have higher fertilization success than younger males. Two hypotheses can potentially explain this pattern: 1) females prefer older, and often more ornamented males, or 2) older males invest more in reproduction and fertility than younger males. Here we studied factors associated with age-related male fertilization success in a population of barn swallows Hirundo rustica in Canada. We document that male fertilization success increased gradually up to a minimum age of four-year old. The age effect was especially strong for the number of extrapair offspring obtained and the occurrence of a second brood. The higher fertilization success of older males was also associated with an early start of breeding in spring. The length of the elongated outermost tail feathers, a postulated male ornament preferred by females, also increased with age (in both sexes), but it was not a significant predictor of male fertilization success within age classes. Male fertility traits, especially testis size, but also sperm motility and sperm velocity, increased significantly across age groups. Our results suggest that the higher fertilization success by older males is due to their higher reproductive investments and that their longer tails are an adaptation to early arrival on the breeding grounds.Significance statementThe barn swallow is a socially monogamous passerine with extensive extrapair mating. We found that males become more successful in siring both withinpair and extrapair offspring as they become older. Their increased fertilization success was associated with a higher reproductive effort as indicated by larger testes, more motile sperm, and an earlier start of breeding in spring. The length of the outer tail feathers increased with age in both sexes, but long tails did not enhance male fertilization success among males of the same age. Long tails are probably an adaptation to rapid migration and earlier arrival on the breeding grounds. Our findings suggest that the commonly observed age-related increase in male fertilization success in passerine birds is better explained by life history theory than by sexual selection theory.

Life-history traits facilitate the population success of the sergeant major Abudefduf saxatilis (Linnaeus, 1758, Perciformes: Pomacentridae) in the Caribbean Sea

ABSTRACT Trade-offs among life-history traits (e.g. growth, reproduction, and survival) are fundamental to the population success of living beings in the wild. This study describes the life-history traits of the sergeant major, Abudefduf saxatilis, one of those fishes most abundant in the coral reefs of the Caribbean Sea. The reproductive biology, age, growth, and abundance of a particular population of A. saxatilis from Mexico was explored using 12 monthly samplings to collect 414 specimens, and abundance monitoring through visual censuses for age-based demographic analysis. Our results indicated that A. saxatilis would have an opportunistic strategy with a type II survivorship curve since the studied population was characterized by fast growth, maturation at intermediate sizes (≈11 cm L T or 2.5 yrs. old), with batch spawning and indeterminate fecundity, protracted spawning season (January to September), high abundance of recruits, low instantaneous natural mortality (M = 0.114 year −1), high life expectancy at birth (e 0 ≈ 4.7 yrs.) and maturity (e α ≈ 2.8 yrs.), and high annual survival of adults and high survival to maturity (). All these life-history traits facilitate the population success of A. saxatilis, showing a high reproductive effort and a rapid population turnover, making this species an efficient colonizer.

Biomass Allocation Responses to Root Interactions in Wheat Cultivars Support Predictions of Crop Evolutionary Ecology Theory.

The goal of agriculture is to optimize the population yield, but natural selection has produced active competition among plants, which decreases population performance. Therefore, cultivar breeding should be based on group selection, increasing yield by weakening individual competitive responses. We hypothesize that this has occurred inadvertently to some degree, so modern cultivars have weakened competitive traits and responses, such as reduced root proliferation in response to neighboring roots. We conducted a field experiment with eight cultivars of spring wheat that have been released over the last hundred years, which we grew at two densities. Two contrasting wheat cultivars, a landrace and a modern cultivar, were used in a second field experiment on competition within and between the two cultivars to quantify their competitiveness. Finally, a greenhouse experiment was conducted with these two cultivars gown (a) in mixture and monoculture, (b) at four densities, (c) two watering levels, and (d) with permeable vs. non-permeable soil dividers, to study root proliferation responses to competition. Results of field experiment 1 showed that the population aboveground biomass (AGB) had increased, while belowground biomass had decreased over the course of breeding, so that the root to shoot ratio (R/S) was negatively correlated with the release year of the cultivar. The landrace had stronger competitiveness than the modern cultivar in the field experiment 2. There was clear evidence of root proliferation and a resultant reduction in AGB in response to neighboring roots in the greenhouse experiment, and the modern variety showed less root proliferation in response to neighbors. We conclude that the newer cultivar was a weaker competitor but higher-yielding in two ways: (1) it had higher reproductive effort and therefore less allocation to structures that increase competitive ability, and (2) it had reduced root proliferation in response to the roots of neighboring plants. Our results show that wheat plants change their biomass allocation in response to resource levels and the presence of neighboring roots. The presence of root proliferation in the modern cultivar, albeit less than in the landrace, suggests that further increases in yield via group selection are possible.

High reproductive effort in a vulnerable lizard from high altitudes in Argentina: Reproductive biology and sexual dimorphism in Phymaturus extrilidus.

Reproductive biology is fundamental to understanding the ecology and evolution of lizards which, in turn, is essential for the definition of the species´ conservation status. We studied life-history traits related to the reproduction of the Phymaturus extrilidus lizard, including the male and female reproductive cycles, litter size, mean annual reproductive output, reproductive effort, sexual maturity size and sexual dimorphism, body condition, and fat body cycles. We found sexual dimorphism in size and shape, supporting the hypotheses of sexual and fecundity selection. Females exhibited biennial reproductive cycles synchronous with the annual prenuptial male cycle, adjusted for the maturation of the vitellogenic follicles of females. Females of P. extrilidus have the highest mean annual reproductive output (MARO=1.14) recorded in Phymaturus, and this is accompanied by the highest reproductive effort (C=0.28, C energetic =0.31). Births occur from late summer to early autumn. The female reproductive cycle, strictly biennial, like all species of the P. palluma group, and the vitellogenesis in particular, appear to be limited by body condition and the amount of fat body stored. This study presents the fundamental reproductive traits of P. extrilidus that can provide valuable information to be used in the evaluation of the conservation status of this species.

Study of the pattern of reproductive allocation and fruit development in young dioecious trees of Idesia polycarpa Maxim

Several studies have reported females of dioecious species often have higher reproductive effort than males because they produce fruits and seeds. We examined the relative reproductive allocation of the inflorescences at the shoot and whole plant levels of the sexes. The number of inflorescence clusters in the shoot following the tier of branches and reproductive parts (fruiting spurs, short branches, and lateral terminal buds) of females and males was compared. In addition, the reproductive allocation in the per shoot, fruit growth, weight variation, fruit diameter, and fruit numbers counted and the annual reproductive variations were examined. The study was found a female-biased annual reproductive allocation of this species. The inflorescence cluster production was 8.85% higher in females than males. Fruiting spurs produced the highest number of inflorescence clusters in both sexes. The highest 64% and 51% of inflorescence clusters allocation were in the second tier of branches (2Y) of females and males, respectively. Fruits were the highest in numbers from June to July and produced in the 2Y, besides, the highest fruit loss occurred by 56.92% from September to October in females. The results suggest that the architecture of females and males in Idesia polycarpa invests differently in their reproductive allocation and quantity depending on branch type.

Reproductive ecology of Zostera marina L. (eelgrass) across varying environmental conditions

Sexual reproduction is critical to the resilience of seagrass beds impacted by habitat degradation or environmental changes, as robust seed banks allow new shoots to establish each year. Reproductive strategies of seagrass beds range on a continuum from strictly annual to perennial, driven by local environmental conditions. We examined the reproductive dynamics of Zostera marina beds at six sites on the Atlantic coast of Canada to characterize how life history strategies are shaped by the surrounding environment. Sites were categorized as wave protected and wave exposed, where protected sites were warm, shallow, with little water movement and muddy sediments, and exposed sites were either shallow or deep, with cooler water and sandy sediments. While mixed life history strategies were evident at all sites, protected eelgrass beds exhibited both the highest and lowest sexual reproductive effort relative to exposed beds. These beds regularly experienced thermal stress, with higher temperature range and extended warm water events relative to exposed beds. The development of reproductive shoots were similar across sites with comparable Growing Degree-days at the beginning and end of anthesis, but the First Flowering Date was earlier at the protected warmer sites relative to exposed sites. With different reproductive shoot density among sites, seed production, seed retention, and seedling recruitment also varied strongly. Only one site, located in a warm, shallow and protected lagoon, contained a mixed life history population with a high reproductive effort (33.7%), strong seed bank, and high seedling establishment. However, a primarily perennial population with the lowest reproductive effort (0.5%) was identified at the warmest site, suggesting that conditions here could not support high sexual reproduction. Robustness of seed banks was strongly linked to reproductive shoot density, although the role of seed retention, germination and seedling survival require further investigation. Our study provides insights into one key aspect of seagrass resilience, and suggests that resilience assessments should include reproductive shoot density to inform their management and conservation.

Declining amphibians might be evolving increased reproductive effort in the face of devastating disease.

The devastating infectious disease chytridiomycosis has caused declines of amphibians across the globe, yet some populations are persisting and even recovering. One understudied effect of wildlife disease is changes in reproductive effort. Here, we aimed to understand if the disease has plastic effects on reproduction and if reproductive effort could evolve with disease endemism. We compared the effects of experimental pathogen exposure (trait plasticity) and population-level disease history (evolution in trait baseline) on reproductive effort using gametogenesis as a proxy in the declining and endangered frog Litoria verreauxii alpina. We found that unexposed males from disease-endemic populations had higher reproductive effort, which is consistent with an evolutionary response to chytridiomycosis. We also found evidence of trait plasticity, where males and females were affected differently by infection: pathogen exposed males had higher reproductive effort (larger testes), whereas females had reduced reproductive effort (smaller and fewer developed eggs) regardless of the population of origin. Infectious diseases can cause plastic changes in the reproductive effort at an individual level, and population-level disease exposure can result in changes to baseline reproductive effort; therefore, individual- and population-level effects of disease should be considered when designing management and conservation programs for threatened and declining species.

Clinal variation in phenological traits and fitness responses to drought across the native range of California poppy

Increased aridity, associated with climate change, is predicted worldwide in the coming decades. Species persistence in the face of climate change is thought to be influenced by plasticity, potential for adaptation, and dependence on non-climatic factors, but their relative importance has rarely been quantified. We investigated 13 populations of Eschscholzia californica (California poppy) distributed across a fourfold gradient in annual precipitation. In a greenhouse, plants received precipitation treatments approximating the wettest and driest sites, crossed with the presence and absence of soil inoculum from their collection location. We documented clinal variation across populations; plants from southern populations (arid sites) emerged later, flowered earlier, had shorter growing seasons, higher mean fitness, higher reproductive effort, and were more drought tolerant than plants from northern populations (mesic sites). A second experiment demonstrated clinal variation in biomass allocation, with higher root allocation in northern populations. We found no evidence of adaptive phenological plasticity to drought; instead, the drought treatment decreased fitness and growing season length (maladaptive phenological plasticity) more for plants from mesic than arid sites. Individuals grown with home soil inoculation produced 10% more biomass than when grown in common garden soil; however, the influence of soil was small relative to the 13-fold variation across populations in fitness responses to drought. Our results suggest that restoration efforts involving California poppy may benefit from assisted gene flow; sourcing seeds from arid parts of the species range may improve individual fitness and population persistence of this iconic species in the face of future climate change.

Nutrient History Affects the Response and Resilience of the Tropical Seagrass Halophila stipulacea to Further Enrichment in Its Native Habitat.

Eutrophication is one of the main threats to seagrass meadows, but there is limited knowledge on the interactive effects of nutrients under a changing climate, particularly for tropical seagrass species. This study aimed to detect the onset of stress in the tropical seagrass, Halophila stipulacea, by investigating the effect of in situ nutrient addition during an unusually warm summer over a 6-month period. We measured a suite of different morphological and biochemical community metrics and individual plant traits from two different sites with contrasting levels of eutrophication history before and after in situ fertilization in the Gulf of Aqaba. Nutrient stress combined with summer temperatures that surpassed the threshold for optimal growth negatively affected seagrass plants from South Beach (SB), an oligotrophic marine protected area, while H. stipulacea populations from North Beach (NB), a eutrophic and anthropogenically impacted area, benefited from the additional nutrient input. Lower aboveground (AG) and belowground (BG) biomass, reduced Leaf Area Index (LAI), smaller internodal distances, high sexual reproductive effort and the increasing occurrence of apical shoots in seagrasses from SB sites indicated that the plants were under stress and not growing under optimal conditions. Moreover, AG and BG biomass and internodal distances decreased further with the addition of fertilizer in SB sites. Results presented here highlight the fact that H. stipulacea is one of the most tolerant and plastic seagrass species. Our study further demonstrates that the effects of fertilization differ significantly between meadows that are growing exposed to different levels of anthropogenic pressures. Thus, the meadow’s “history” affects it resilience and response to further stress. Our results suggest that monitoring efforts on H. stipulacea populations in its native range should focus especially on carbohydrate reserves in leaves and rhizomes, LAI, internodal length and percentage of apical shoots as suitable warning indicators for nutrient stress in this seagrass species to minimize future impacts on these valuable ecosystems.

Costs of reproduction under experimental climate change across elevations in the perennial forb Boechera stricta.

Investment in current reproduction can reduce future fitness by depleting resources needed for maintenance, particularly under environmental stress. These trade-offs influence life-history evolution. We tested whether climate change alters the future-fitness costs of current reproduction in a large-scale field experiment of Boechera stricta (Brassicaceae). Over 6 years, we simulated climate change along an elevational gradient in the Rocky Mountains through snow removal, which accelerates snowmelt and reduces soil water availability. Costs of reproduction were greatest in arid, lower elevations, where high initial reproductive effort depressed future fitness. At mid-elevations, initial reproduction augmented subsequent fitness in benign conditions, but pronounced costs emerged under snow removal. At high elevation, snow removal dampened costs of reproduction by prolonging the growing season. In most scenarios, failed reproduction in response to resource limitation depressed lifetime fecundity. Indeed, fruit abortion only benefited high-fitness individuals under benign conditions. We propose that climate change could shift life-history trade-offs in an environment-dependent fashion, possibly favouring early reproduction and short lifespans in stressful conditions.

Evaluating costs of heavy metal tolerance in a widely distributed, invasive butterfly.

Organismal tolerance to environmental pollution is thought to be constrained by fitness costs, where variants with higher survival in polluted environments have lower performance in nonpolluted environments. Yet, costs are not always detected in empirical studies. One hypothesis suggests that whether tolerance costs emerge depends on the degree of heterogeneity populations experience with respect to pollution exposure. For instance, in populations confined to local environments where pollution is persistent, selection may favour alleles that enhance pollution tolerance but reduce performance in nonpolluted environments (costs). However, in broadly distributed populations that undergo selection in both polluted and nonpolluted patches, costs should be eroded. Understanding tolerance costs in broadly distributed populations is relevant to management of invasive species, which are highly dispersive, wide ranging, and often colonize disturbed or polluted patches such as agricultural monocultures. Therefore, we conducted a case study quantifying costs of tolerance to zinc pollution (a common heavy metal pollutant) in wild cabbage white butterflies (Pieris rapae). This wide ranging, highly dispersive and invasive pest periodically encounters metal pollution by consuming plants in urban and agricultural settings. In contrast to expected costs of tolerance, we found that cabbage white families with greater zinc tolerance also produced more eggs and had higher reproductive effort under nonpolluted conditions. These results contribute to a more general hypothesis of why costs of pollution tolerance vary across studies: patchy selection with pollutants should erode costs and may favour genotypes that perform well under both polluted and nonpolluted conditions. This might partly explain why widely distributed invasive species are able to thrive in diverse, polluted and nonpolluted habitats.

Leaf-litter consumption slows crab growth but transforms mangrove food chains

Leaf litter consumption has implications for growth and nutrient balances of mangrove crabs and mangrove trophic pathways. This study (1) addressed the impact of leaf litter quality and quantity on crab life history and growth, and (2) proposed keystone roles of crabs in mangrove material fluxes. Estimates of crab standing stocks, growth, and carbon and nitrogen mass balances were obtained for a field population of Parasesarma messa, a primary consumer of leaf litter in Queensland mangroves. P. messa exhibited slow growth and individuals took >>4 yr to reach maximum size. Females appeared to breed once per year with high reproductive effort relative to other crabs. An apparent trade-off between growth and reproduction in the dry-wet transition season was caused by a shortage of available leaf litter. A nitrogen mass balance indicated that the population ingested twice the amount of nitrogen that could be supplied by leaf litter. Assuming mortality was mainly due to predation, the estimated loss to predators (28 kg ha-1 yr-1) supported a hypothesis that crab consumption by fish short-circuits mangrove food chains. Faecal production by crabs (0.48 Mg C ha-1 yr-1 and 0.03 Mg N ha-1 yr-1) represents a substantial contribution to deposit-feeding food chains. P. messa is a keystone species whose impact on ecosystem processes is large relative to its abundance and biomass.

Fighting on the edge: reproductive effort and population structure of the invasive coral Tubastraea coccinea in its southern Atlantic limit of distribution following control activities

The detection and control of invasive alien species in marine ecosystems is especially challenging because it is difficult to visualize the full extension of an invasion, while control options are often limited. The invasive scleractinian coral Tubastraea coccinea have spread over 8000 km of the Atlantic coastline, from Florida in the USA to southern Brazil, mainly in association with oil and gas platforms. This invasive coral threatens endemic species, reduces native coral recruitment, and modifies communities and trophic interactions, posing a relevant threat to shallow Atlantic reefs. The main aim of our study was to assess the effectiveness of an ongoing T. coccinea control program by analyzing the results of control interventions on population structure and cover of the target species in its southern Atlantic limit of distribution. We also describe the reproductive effort of T. coccinea in a 12-month time span. Between 2012 and 2019, almost 14,000 colonies were removed, most of them of small size (< 5 polyps). The highest reproductive effort was observed in September. Changes in T. coccinea cover, population structure and potential local propagule supply were observed. Control activities led to a reduction in up to half the cover of the invaded area, maintained the majority of the population in non-reproductive sizes, and consequently lowered the potential local propagule supply. Our paper highlights the fundamental role of control in preventing the local spread of T. coccinea. Recommendations on management frequency and timing are also discussed in order to contribute to the improvement of management efficiency.

Accelerated senescence as a cost of reproduction: Testing associations between oxidative stress and reproductive effort in rural and urban women.

Oxidative stress is hypothesized to contribute to age-related somatic deterioration. Both reproductive and ecological context may necessitate tradeoffs that influence this outcome. We examined whether measures of lifetime reproductive effort were related to levels of oxidative stress biomarkers in peri- and post-menopausal women and whether associations were moderated by rural or urban residence. We surveyed 263 healthy women (age 62.1 ± 10.0 SD) from rural (N=161) and urban Poland (N=102), collecting sociodemographic data and urine samples to analyze biomarkers of oxidative stress (8-oxo-2'-deoxyguanosine, 8-OHdG) and antioxidative defense (copper-zinc superoxide dismutase, Cu-Zn SOD). Linear regression models, adjusted for residence, were used to test for associations between reproductive effort and 8-OHdG and Cu-Zn SOD. Univariate models demonstrated significant associations between gravidity and the biomarkers of oxidative stress (8-OHdG: R2 =0.042, P ≤ .001; Cu-Zn SOD: R2 =0.123, P ≤ .001). Multivariate models incorporating potential confounding variables, as well as cross-product interaction terms, indicated that gravidity was associated with 8-OHdG (P < .01, R2 adj =0.067) and Cu-Zn SOD (P=.01, R2 adj =0.159). Residence (ie, urban vs rural) did not significantly moderate the associations between the biomarkers and reproductive effort. Higher lifetime reproductive effort contributes to increases in oxidative stress and antioxidative defenses. Our results provide evidence of potential mechanisms underlying the physiological tradeoffs influencing senescence for women with high reproductive effort. We illustrate the value of applying an evolutionary perspective to elucidate variation in human health and senescence.

Costs of reproduction and ageing in the human female.

Evolutionary theories of ageing point to reproduction as a significant factor to consider when asking why ageing occurs and why there is inter-individual variation in its progression. Reproduction in human females is costly, in terms of energy, nutrients and metabolic adjustments. Thus, it is expected that women who experienced high reproductive effort resulting from multiple reproductive events will age faster. However, the evidence for long-term negative effects of reproduction is not conclusive. The lack of understanding of whether there are trade-offs between reproduction and ageing in women is partly due to methodological challenges. The costs of reproduction are often calculated based only on parity, while other elements contributing to these costs (e.g. breastfeeding, timing of reproduction) are neglected, which may significantly underestimate the total costs and obscure the all-important inter-individual variation in such costs. Costs must be evaluated in relation to individual characteristics, including developmental conditions, nutritional status and social support that a mother receives during reproduction. Furthermore, ageing and health must be assessed based on comprehensive markers rather than arbitrarily assembled variables. Finally, longitudinal rather than cross-sectional studies and new statistical approaches are needed to reveal how much of a decline in health and progressing ageing can actually be attributed to past reproductive processes. This article is part of the theme issue 'Evolution of the primate ageing process'.

Heat and drought determine flower female allocation in a hermaphroditic Mediterranean plant family.

In animal-pollinated hermaphroditic species, larger and xenogamous flowers increase male-biased resource allocation, whereas smaller and selfing flowers invest disproportionally more resources to female function. In Cistaceae, an entomophilous and hermaphroditic Mediterranean family, this pattern generally follows a phylogenetic signal. However, resource allocation to carpels is independent of phylogeny, which suggests trait divergences among closely related species during the diversification into different environmental conditions. We tested this hypothesis across 37 species of Cistaceae along a temperature and precipitation gradient, including semiarid, dry, subhumid and humid sites. We quantified the proportions of dry mass and nutrient investment to carpels and tested the influence of the climatic gradient and site-specific precipitation on the interspecific variation in carpel resource allocation. Lowest and highest percentages of resource allocation to carpels ranged from 1.5-4.2% to 24.2-36.6%, respectively. The proportion of resources comprised in carpels significantly decreased with increasing precipitation/decreasing temperature. Thus, carpels comprised proportionally more resources under drier and hotter conditions, especially in semiarid sites. Our results demonstrate how the extent of climatic constraints is more important than phylogenetic relationships in determining stress-induced differences in carpel resource allocation across species of Cistaceae in a Mediterranean environment. We suggest that allocation of proportionally more resources to carpels in drier and hotter sites lies within a strategy to deal with the most stressful conditions by means of a high reproductive effort.

Environmentally relevant concentrations of methamphetamine and sertraline modify the behavior and life history traits of an aquatic invertebrate

Pharmaceutically active compounds are major contaminants of aquatic environments that show direct and indirect effects on aquatic organisms even at low concentrations. The aim of this study was to assess the effects of the illicit drug methamphetamine and the antidepressant sertraline on clonal marbled crayfish Procambarus virginalis. Crayfish exposed to the environmentally relevant concentrations of methamphetamine of ∼1 μg L−1 did not exhibit significant differences from unexposed controls in distance moved, velocity, and activity level with or without available shelter. Sertraline-exposed (∼1 μg L−1) crayfish were significantly more active, regardless of available shelter, and moved greater distances when shelter was available, compared to control crayfish. Crayfish exposed to methamphetamine and sertraline spent significantly more time outside the shelters compared to controls. Sertraline-exposed crayfish spawned more frequently and showed higher mortality than controls. The results suggest that the low environmental concentrations of the tested compounds could alter the behavior and life history traits of crayfish, resulting in higher reproductive effort and mortality.

Senescence and costs of reproduction in the life history of a small precocial species.

Species following a fast life history are expected to express fitness costs mainly as increased mortality, while slow‐lived species should suffer fertility costs. Because observational studies have limited power to disentangle intrinsic and extrinsic factors influencing senescence, we manipulated reproductive effort experimentally in the cavy (Cavia aperea) which produces extremely precocial young. We created two experimental groups: One was allowed continuous reproduction (CR) and the other intermittent reproduction (IR) by removing males at regular intervals. We predicted that the CR females should senesce (and die) earlier and produce either fewer and/or smaller, slower growing offspring per litter than those of the IR group. CR females had 16% more litters during three years than IR females. CR females increased mass and body condition more steeply and both remained higher until the experiment ended. Female survival showed no group difference. Reproductive senescence in litter size, litter mass, and reproductive effort (litter mass/maternal mass) began after about 600 days and was slightly stronger in CR than IR females. Litter size, litter mass, and offspring survival declined with maternal age and were influenced by seasonality. IR females decreased reproductive effort less during cold seasons and only at higher age than CR females. Nevertheless, offspring winter mortality was higher in IR females. Our results show small costs of reproduction despite high reproductive effort, suggesting that under ad libitum food conditions costs depend largely on internal regulation of allocation decisions.