Female preference for nests with many eggs:A cost-benefit analysis of female choice in fish with paternal care

In several fish species with paternal care, females prefer males guarding many eggs in their nest. This preference might be advantageous because the presence of many other eggs dilutes the risk of newly laid eggs being eaten by the father. To evaluate this hypothesis quantitatively, we constructed a simulation model that mimics the breeding biology of the blenny Aidablennius sphynx. In contrast to earlier verbal models, the costs of choice are explicitly taken into account. We systematically varied factors such as the stringency of choosiness and the level and nature of the costs of choice. For realistic parameter values female choosiness mali result in a fitness advantage of more than 50%. The optimal choice strategy created a distribution of eggs over the nests which resembles that found in the field for A. sphynx. Our model shows that the relative fitness of a choice strategy is not constant but frequency dependent in a complicated way. If most females are choosy a bimodal distribution of eggs over the nests results, with many nests containing few and some nests containing many eggs. In such a situation choosiness is profitable, since randomly laying females will often lay their eggs in nests with few eggs, producing a high mortality per egg due to filial cannibalism. If, on the other hand, only few choosers are present, their influence on the egg distribution is limited. A unimodal distribution results which is profitable for nonchoosers, since the average egg mortality is low and nonchoosers do not bear the costs of choice. The positive relation between chooser frequency and chooser fitness makes it easy to understand why choosiness is evolutionarily stable. However, it is not obvious how the trait is established by selection in the first place

No evidence for UV-based nest-site selection in sticklebacks

BACKGROUND: Nests are built in various animal taxa including fish. In systems with exclusive male parental care, the choice of a nest site may be an important component of male fitness. The nest site may influence male attractiveness as a mate, and male, embryo, and juvenile survival probabilities. Reproductively active three-spined stickleback males establish and defend a territory in which they build a nest. Territories can differ remarkably in qualities that influence male and female reproductive success like predation risk or abiotic factors such as dissolved oxygen concentration or lighting conditions. The latter may be important because in sticklebacks the extended visual capability into the ultraviolet (UV) wave range plays a role in female mate choice. Males are thus expected to be choosy about the habitat in which they will build their nest. RESULTS: We tested nest-site choice in male three-spined sticklebacks with respect to different UV lighting conditions. Reproductively active males were given the simultaneous choice to build their nest either in an UV-rich (UV+) or an UV-lacking (UV-) environment. Males exhibited no significant nest-site preferences with respect to UV+ or UV-. However, larger males and also heavier ones completed their nests earlier. CONCLUSION: We found that UV radiation as well as differences in luminance had no influence on nest-site choice in three-spined sticklebacks. Males that built in the UV-rich environment were not different in any trait (body traits and UV reflection traits) from males that built in the UV-poor environment. There was a significant effect of standard length and body mass on the time elapsed until nest completion in the UV experiment. The larger and heavier a male, the faster he completed his nest. In the brightness control experiment there was a significant effect only of body mass on the duration of nest completion. Whether nest building preferences with respect to UV lighting conditions are context dependent needs to be tested for instance by nest-site choice experiment under increased predation risk

Interspecific Hybridization Increased in Congeneric Flatfishes after the Prestige Oil Spill

Marine species with relatively low migratory capacity are threatened by habitat alterations derived from human activities. In November 2002 the tanker Prestige sank off the Spanish northwest coast releasing 70,000 tons of fuel and damaging biota in the area. Despite efforts to clean the damaged areas, fuel remnants have affected marine species over the last nine years. This study is focused on two flatfish, Lepidorhombus boscii (four-spotted megrim) and L. whiffiagonis (megrim), whose spawning areas are located at the edge of the continental platform. We have analyzed megrim samples from North Spanish and French waters obtained before and after the oil spill. Genotypes at the nuclear marker 5S rDNA indicate a significant increase in interspecific hybridization after the Prestige accident, likely due to forced spawning overlap. The mitochondrial D-Loop region was employed for determining the direction of hybrid crosses, which were most frequently L. boscii female x L. whiffiagonis male. Reduced ability of L. boscii females to select conspecific mates would explain such asymmetric hybridization. To our knowledge this is the first time that increased hybridization between fish species can be associated to an oil spill. These results illustrate the potential long-term effect of petrol wastes on wild fish species

Emergence of unusual coexistence states in cyclic game systems

Evolutionary games of cyclic competitions have been extensively studied to gain insights into one of the most fundamental phenomena in nature: biodiversity that seems to be excluded by the principle of natural selection. The Rock-Paper-Scissors (RPS) game of three species and its extensions [e.g., the Rock-Paper-Scissors-Lizard-Spock (RPSLS) game] are paradigmatic models in this field. In all previous studies, the intrinsic symmetry associated with cyclic competitions imposes a limitation on the resulting coexistence states, leading to only selective types of such states. We investigate the effect of nonuniform intraspecific competitions on coexistence and find that a wider spectrum of coexistence states can emerge and persist. This surprising finding is substantiated using three classes of cyclic game models through stability analysis, Monte Carlo simulations and continuous spatiotemporal dynamical evolution from partial differential equations. Our finding indicates that intraspecific competitions or alternative symmetry-breaking mechanisms can promote biodiversity to a broader extent than previously thought

Female preference and filial cannibalism in Aidablennius sphynx (Teleostei, Blenniidae); A combined field and laboratory study

In the fish Aidablennius sphynx, in which males continuously care for up to 7000 eggs throughout the breeding season, females prefer to mate with males that already guard eggs, The present study shows that this preference appears to be adaptive because the probability of eggs being cannibalized decreased with brood size. In the field, on average 36 eggs disappeared from nests per day, where the main egg predator seemed to be the guarding male. Experiments showed that males selectively consumed dead eggs, probably to prevent the spread of infections. However, only with large broods did the numbers of eggs cannibalized in the field correspond to the egg mortality rate, that was determined to be 0.8%. When guarding small broods, males have probably also eaten healthy eggs. Breeding males suffered an average weight loss of 19.4%, This suggests that breeding males are restricted in foraging opportunities. When a male was experimentally fed, he cannibalized fewer eggs only when guarding small broods, not when guarding large broods, Therefore, it seems that caring males daily harvest eggs to remain in sufficient condition, In large broods they use eggs that recently died. When the male is guarding small broods the low numbers of dead eggs do not suffice, and healthy eggs are also eaten