Beyond classical theories: An integrative mathematical model of mating dynamics and parental care.

Classical theories, such as Bateman's principle and Trivers' parental investment theory, attempted to explain the coevolution of sexual selection and parental care through simple verbal arguments. Since then, quantitative models have demonstrated that it is rarely that simple because many non-intuitive structures and non-linear relationships are actually at play. In this study, we propose a new standard for models of mating dynamics and parental care, emphasizing the clarity and use of mathematical and probabilistic arguments, the meaning of consistency conditions, and the key role of spatial densities and the law of mass action. We used adaptive dynamics to calculate the evolutionary trajectory of the total care duration. Our results clearly show how the outcomes of parental care evolution can be diverse, depending on the quantitative balance between a set of dynamical forces arising from relevant differences and conditions in the male and female populations. The intensity of sexual selection, synergy of care, care quality, and relative mortality rates during mating interactions and caring activities act as forces driving evolutionary transitions between uniparental and biparental care. Sexual selection reduces the care duration of the selected sex, uniparental care evolves in the sex that offers the higher care quality, higher mortality during mating interactions of one sex leads to more care by that sex, and higher mortality during caring activities of one sex favours the evolution of uniparental care in the other sex. Both synergy and higher overall mortality during mating interactions can stabilize biparental care when sexual selection reduces the care duration of the selected sex. We discuss how the interaction between these forces influences the evolution of care patterns, and how sex ratios can vary and be interpreted in these contexts. We also propose new directions for future developments of our integrative model, creating new comparable analyses that share the same underlying assumptions and dynamical frameworks.

Individual specialization and generalization in predator-prey dynamics: The determinant role of predation efficiency and prey reproductive rates.

Individual specialization and generalization refer to the breadth of prey types consumed by predators among all available prey. The ecological factors mechanistically determining individual differences and the coexistence of foraging strategies remain to be clarified. Formal quantitative models can elucidate the complex nonlinear mechanisms underlying predator-prey interactions. In this study, we built a dynamical model with multiple prey, with different nutritional values and reproductive rates, which are consumed by specialist and generalist predators. We then analyzed the viability of individual foraging strategies in all possible scenarios. Relative prey fertility and relative efficiency of predation, rather than prey nutritional value, determined the success of specialists and generalists. Less reproducing prey and the specialists relying on them face the highest danger of extinction, while generalists cannot thrive where specialists are sufficiently efficient in relation to the number of available prey. Our study provides new perspectives for empirical studies on individual specialization.

Know your enemy: The dragonfly Erythrodiplax fusca (Libellulidae) uses eavesdropping to obtain information about potential rivals.

Animals can eavesdrop on other competitors during territorial defense disputes to better choose rivals weaker than themselves and increase the chances of monopolizing resources. In dragonflies, males often compete for access to water bodies, which attract sexually receptive females to mate and lay eggs. During the breeding season, satellite males can observe fights between territory owners and intruders and, therefore, obtain information about potential rivals through visual cues. Consequently, weaker competitors may face more intense competition than stronger ones when defending a territory. In this study, we conducted field experiments with the dragonfly Erythrodiplax fusca to investigate whether eavesdropping on territorial disputes, using visual cues, affects the intensity of competition that territory owners face. We recorded the number of intruders that engage in disputes against males that recently occupied territories in two groups: the "eavesdropping" group (i.e., individuals with access to rivals' prior information) and the control group (i.e., competitors with no access to prior information). The number of intruders was greater in the eavesdropping group compared to the control group. This effect depended on the interaction between the size of the territory owners and the presence of eavesdropping. The number of intruders decreased with increase in the size of the owners in the presence of eavesdropping, but this relationship did not occur in the control group. We discuss the implications of our findings for the male decision-making process to initiate agonistic disputes and how investigating eavesdropping behavior can improve current models of conflict resolution in animals.

A novel trophobiotic interaction between a Neotropical stink bug and an ant species: Insights into potential benefits to the host plant.

Trophobiotic interactions occur when phytophagous insects provide a sugary liquid, the honeydew, for ants and obtain defence against predators or parasitoids. The plants may indirectly benefit from an increased ant foraging activity by reducing the herbivorous abundance. These three trophic interactions have been previously studied for several species, but mainly involving plants with extrafloral nectaries, which is a plant structure that also produce attractive substances for ants. Previous studies have reported an ant preference for honeydew over extrafloral nectary content. Therefore, trophobiosis can be an important mediator of ant-plant interactions. In this study, we describe a trophobiotic interaction between Edessa contermina stink bugs and Camponotus blandus ants on the Byrsonima verbascifolia plants occurring in a conservation area of Brazilian savanna. Stink bugs excreted a sugary liquid which was consumed by the ants, and C. blandus ants were observed consuming potential parasitoids. Stink bugs were more abundant in plants containing high food supply and shelter availability. The occurrence of ants depended of the number of inflorescences and trunk circumference of B. verbascifolia. Ant abundance, however, was positively correlated with stink bug abundance and the number of inflorescences. Herbivory was not explained by neither plant architecture nor ant abundance. This high ant activity may benefit plants from a protection against herbivory, but we did not detect this effect during the study period. Hence, the interaction among ants and plants was apparently commensal. We concluded that plant traits were important in ant attraction, but stink bugs foraging also increased ant activity on the plant, but mainly on inflorescences. Therefore, the plant may benefit from an increased defence of inflorescences rather than leaves.

Araneophagy as an alternative foraging tactic to kleptoparasitism in two Argyrodinae (Araneae: Theridiidae) species.

Kleptoparasitism is assumed to be the main foraging strategy in some animal groups, such as the spiders of the subfamily Argyrodinae (Theridiidae). However, some species may also feed on silk threads, egg sacs, or even their hosts. The conditions determining these alternative foraging tactics remain unknown for most species. We performed field observations, stable isotope analysis and laboratory experiments to investigate kleptoparasitism and araneophagy of Argyrodes elevatus and Faiditus caudatus in webs of Manogea porracea (Araneidae). We evaluated the following hypotheses: (1) both species exhibit higher trophic positions than their hosts and closest to an araneophagic sympatric species; (2) host web selection is influenced by the presence of alternative resources (adult male and female, and egg sacs); and (3) they preferentially consume egg sacs instead of stored prey items. Both argyrodines showed higher trophic positions than their female hosts and closest to an araneophagic spider species. The invaders were found mainly on host webs with one adult and egg sacs and with egg sacs only. Finally, A. elevatus preferred to feed on prey captured by the host spider instead of egg sacs. We discussed the factors that can potentially determine the choices between foraging exclusively as kleptoparasites and consuming the hosts.

Influence of web traits, height, and daily periods of exposition on prey captured by orb-weaver spiders.

Orb-webs show diversity in several traits, including silk types, architecture, physical properties, locale, and period of exposition. The investigation of how they determine the identity of intercepted prey is important to functional ecology and to the evaluation of trophic niche partitioning within communities. However, the influence of several of these variables on the composition of intercepted insects remains to be determined. In this study, we evaluated the effects of web architectural traits, height, and daily periods of exposition on the interception of different insects in terms of sizes, masses, and taxa. We conducted observations of prey intercepted by the orb webs of 16 sympatric spider species and artificial webs. We found that all orb webs mainly intercepted small and light insects, sharing the most abundant insect families found in the study area. However, spiders that show nocturnal activity, more radii in their webs, large and high webs captured heavier insects. Other orb-web traits, such as the density of capture threads did not influence the kind of intercepted insects. We discuss why some variables affected prey interceptions in terms of mass. Finally, we discuss the implications of these influential variables to functional ecology, niche differentiation, and how behavioral assessments can complete this investigation in future studies.

Towards simplicity and accuracy: Assessing traditional and new estimators of orb-web capture thread length.

Before using estimators, it is essential to consider their efficiency in order to avoid bias in results. Due to the architectural and structural complexity of spider webs, some important variables involved in prey capture are usually estimated based on a few measurements obtained from photographs. One of these variables is the capture thread length (CTL), which can provide valuable information on foraging behaviours and the energetic investment in prey capture. However, many of the webs found in the field are damaged, and there is no automatic method to measure the CTL. Therefore, the determination of a simple and accurate estimator of this variable is important to several studies involving spider foraging strategies. In this study, we assessed the accuracy of traditional and new CTL estimators and their vulnerability to web shape and asymmetry. Our results validated the accuracy of the previous estimators. However, we also presented a simple new estimator that can be even more accurate, irrespective of whether the webs exhibit circular shapes or asymmetry in thread investment between superior and inferior web parts. Moreover, we presented an accurate CTL estimator for non-circular orb webs, for which the traditional ones are not applicable.