Differential movement and activity patterns of sexes in a biparental beetle during the reproductive season

1. Biparental care is stabilised if parents perform different tasks during care. Specialised parental roles may require different time and energy budgets that in turn are expected to influence the activity and space use of sexes. 2. Here we investigate movement patterns of the biparental Lethrus apterus beetle using a grid of pitfall traps in their natural habitat. 3. Sexes of the burrow building L. apterus perform different roles during caregiving, as females collect most of the leaves, which serve as food for the offspring while paired males stay mostly in the burrow. We hypothesised that sex differences in mate search and parental activities are reflected in movement patterns. 4. We found that females frequently travelled short distances, whereas males were detected less often but when detected, they travelled significantly longer distances than females. 5. Our results are consistent with the notion that efficient parental food provisioning requires more localised movement and activity patterns. Furthermore, the long distance movements of some males may indicate active mate searching behaviour.     

Evidence for reticulate palaeogeography: beetle diversity linked to connection-disjunction cycles of the Gibraltar strait

Aim Dispersal barriers between areas within some regions have appeared and disappeared throughout evolutionary time. Here we describe the distributional patterns displayed by three taxa living in such kind of regions. These patterns can be better explained considering a reticulated rather than a hierarchically branched palaeogeography. Location Western Mediterranean. Methods The taxa studied are Misolampus (Coleoptera, Tenebrionidae), Tentyria (Coleoptera, Tenebrionidae) and Thorectes (Coleoptera, Geotrupidae). All them are flightless and show a high degree of endemicity. The individual pattern of area relationships was determined separately for each genus by Brooks Parsimony Analysis (BPA). A theoretical general area cladogram was constructed based on the palaeogeographical history of the region. Finally, the general area cladogram is reconciled with the individual ones. Results The ancestor of Misolampus probably was North African. Land dispersal toward the Iberian Peninsula is proposed. Speciation within Iberia is related to specific vicariance events, and the presence of insular (Balearic Islands) populations is explained by sea‐surface or, more probably, human‐mediated dispersal. The ancestor of Tentyria was Iberic. The proposed hypothesis to explain the current species distribution mainly relies on the occurrence of specific vicariance events. However, the occurrence of some sea‐surface dispersal event is not discarded. Almost all possible vicariance events can be recognized in the first clade of the Thorectes genus. There is evidence for dispersal between Africa and Europe at different dates and in both directions. In spite of some uncertainties, the appearance of the second Thorectes clade can also be explained by the occurrence of specific historical events. An ancient dispersal toward the eastern Mediterranean and several dispersal events during the Messinian seem likely. Main conclusions The same historical events have specific outcomes in every tree (even in every branch within a tree) depending on the ability for dispersal and speciation of each taxon. Connection‐disjunction cycles of dispersal barriers have acted as diversity producers.     

Evolution of unstable and stable biparental care

Evolutionarily stable strategy models suggest that biparentalcare will be stable when parents partially compensate for changesin care by the other parent. Previous work has emphasized therelationship between parental expenditure and the current componentof fitness (e. g., offspring survival and fecundity) in causingpartial compensation. This study shows that partial compensationdepends critically on the effect of current parental expenditureon a parent's future fitness (e. g., survival to and fecundityin subsequent breeding seasons). Partial compensation is favoredand biparental care is stable when future fitness is a concave-downfunction of expenditure (i. e., each increment of expenditureis more costly than the previous). However, when future fitnessis a convex-down function of expenditure (i. e., each incrementof expenditure is less costly) biparental care is unstable.(BehavEcol 7: 490–493(1996)]     

Both sexes pay a cost of reproduction in a frog with biparental care

The assumption that reproduction is costly is central to life‐history theory. Good evidence supporting this premise comes from studies, mostly in short‐lived invertebrates, demonstrating a negative relationship between reproduction and longevity. Whether this trade‐off operates broadly, for example in males and females and in short‐ and long‐lived organisms, remains unresolved. We found a negative relationship between reproduction and days survived in captive, wild‐caught, individuals of a long‐lived poison frog with biparental care (Oophaga pumilio). The proportion of time that individuals spent paired and tadpole production rate were negatively associated with days survived in both sexes, and clutch production was negatively associated with days survived in females. These results broaden the taxonomic base upon which this tenet of life‐history theory is built, empirically confirm that females of this species should be choosy when selecting mates and caring for offspring, and suggest that the costs of ‘limited’ male care in this species deserve re‐evaluation. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 211–218.     

Behavioral dynamics between caring males and females in a beetle with facultative biparental care

In families in which both parents care for multiple offspring,the amount of care a parent provides can be simultaneously influencedby multiple social interactions (i.e., parent-parent and parent-offspring).In this study, we first tested for sex differences in the parents'contribution to care and then used path analysis to addressthe simultaneous impact of parent-parent and parent-offspringinteractions on male and female care in the burying beetle,Nicrophorus vespilloides. In this species, both parents provisiontheir offspring predigested carrion from a vertebrate carcass,and the larvae beg for food from their parents. We found thatfemales were more involved in direct care for the larvae andspent more time than did males provisioning the larvae withfood. By using path analysis, we found a negative relationshipbetween male and female provisioning, suggesting that parentsadjust their behavior to that of their mate. Furthermore, wefound that both social interactions (i.e., larval begging) andnonsocial factors (i.e., brood size) significantly influencedmale provisioning, but had no significant effect on female provisioning.We suggest that the difference in the relative contributionof the two sexes to the care of the offspring explains why onlymales seemed to adjust their care to variation in social andnonsocial factors. For example, females may be less able toadjust their care to variation in larval begging and brood sizebecause they were already working near their maximum capacity.     

The significance of biparental care in the brown bullhead,Ictalurus nebulosus

Synopsis Parental care in the brown bullhead is characterized by variation in the participation of each sex. Most broods are attended by both sexes, but some are attended by a male alone, or rarely, a female alone. Two care-givers were more successful than one alone in fostering offspring survival. However, there was no significant difference between two care-givers and one alone in the proportion of time that broods were unattended. Potential brood predators were chased less frequently by one adult alone than by adults aided by their mate. This difference may be unimportant since two adults simultaneously attended their brood only 19% of the time. Males alone attended their broods a significantly greater proportion of time than did either males or females aided by their mates. This difference suggests that males alone sustain a greater cost of care-giving (starvation and therefore reduced future reproduction) than do males aided by their mates. Thus, males alone may more often leave broods (and not return) than males that are aided in care-giving. The differential success observed may be due to a difference in the likelihood that the male (the principal care-giver) leaves the brood permanently, rather than differences in the quality of care one or two adults provide. I suggest that two care-givers are more successful than one because the net benefits of care-giving exceed the net benefits of leaving for males when aided by their mates.     

Behavioural dynamics of biparental care in the dung beetle Onthophagus taurus

In the dimorphic dung beetle Onthophagus taurus major males provide assistance during offspring provisioning. We examined the behavioural dynamics of biparental care to quantify directly how males and females allocate time to parental and nonparental behaviours and to determine whether parents adjust their level of investment relative to their partner's contribution. Females allocated more of their time budget to parental behaviours than males. The proportion of time females allocated to parental behaviours increased after oviposition while that of a male decreased. Male paternity assurance behaviours were negatively associated with male and female parental behaviours. Theoretical models predict that the investment provided by the members of a cooperative pair should be negatively correlated and that any shortfall of one parent should be partially compensated for by the other. In the absence of a male, unassisted females allocated more time to parental care, and performed more parental behaviours. However, compensation was incomplete as unassisted females performed fewer parental behaviours than pairs, resulting in significantly lighter brood masses (the egg and its associated dung supply). Males performed more parental behaviours when paired with small females, and small females more than large females. Contrary to prediction, the investments provided by males and females in a cooperative pair were positively correlated. Males coordinated their parental behaviours with the females rather than acting independently. Since parental behaviours were directly related to the weight of brood masses, the observed parental interactions will have important fitness consequences in this species. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Unbalanced biparental care during colony foundation in two subterranean termites

Parental care is a major component of reproduction in social organisms, particularly during the foundation steps. Because investment into parental care is often costly, each parent is predicted to maximize its fitness by providing less care than its partner. However, this sexual conflict is expected to be low in species with lifelong monogamy, because the fitness of each parent is typically tied to the other's input. Somewhat surprisingly, the outcomes of this tug‐of‐war between maternal and paternal investments have received important attention in vertebrate species, but remain less known in invertebrates. In this study, we investigated how queens and kings share their investment into parental care and other social interactions during colony foundation in two termites with lifelong monogamy: the invasive species Reticulitermes flavipes and the native species R. grassei. Behaviors of royal pairs were recorded during six months using a non‐invasive approach. Our results showed that queens and kings exhibit unbalanced investment in terms of grooming, antennation, trophallaxis, and vibration behavior. Moreover, both parents show behavioral differences toward their partner or their descendants. Our results also revealed differences among species, with R. flavipes exhibiting shorter periods of grooming and antennation toward eggs or partners. They also did more stomodeal trophallaxis and less vibration behavior. Overall, this study emphasizes that despite lifelong monogamy, the two parents are not equally involved in the measured forms of parental care and suggests that kings might be specialized in other tasks. It also indicates that males could play a central, yet poorly studied role in the evolution and maintenance of the eusocial organization.     

Anisogamy selects for male-biased care in self-consistent games with synchronous matings

We reexamine the influential parental investment hypothesis proposed by Trivers for the causal relationship between anisogamy and widespread female-biased parental care. We build self-consistent versions of Maynard Smith's simple evolutionary game between males and females over parental care, and incorporate consequences of anisogamy for gamete production and its trade-off with parental care, and for patterns of mate limitation. As male mating opportunities are limited by females, frequency-dependent selection acts on male strategies. Assuming synchrony of matings in the population, our analytical models find either symmetric sex roles or male-biased care as an evolutionarily stable strategy (ESS), in contrast to Trivers' hypothesis. We simulate evolution in asynchronously mating populations and find that diverse parental roles, including female care, can be ESS depending on the parameters. When caring males can also remate, or when females can increase the clutch size by deserting, there is stronger selection for male-biased care. Hence, we argue that the mating-caring trade-off for males is neither a necessary consequence of anisogamy nor sufficient to select for female-biased care. Instead, the factors excluded from our models—costly competitive traits, sexual selection, and partial parentage—may be necessary for the parental investment hypothesis to work.     

Parental effects on inbreeding depression in a beetle with obligate parental care

Inbreeding depression occurs when individuals who are closely related mate and produce offspring with reduced fitness. Although inbreeding depression is a genetic phenomenon, the magnitude of inbreeding depression can be influenced by environmental conditions and parental effects. In this study, we tested whether size-based parental effects influence the magnitude of inbreeding depression in an insect with elaborate and obligate parental care (the burying beetle, Nicrophorus orbicollis). We found that larger parents produced larger offspring. However, larval mass was also influenced by the interaction between parental body size and larval inbreeding status: when parents were small, inbred larvae were smaller than outbred larvae, but when parents were large this pattern was reversed. In contrast, survival from larval dispersal to adult emergence showed inbreeding depression that was unaffected by parental body size. Our results suggest that size-based parental effects can generate variation in the magnitude of inbreeding depression. Further work is needed to dissect the mechanisms through which this might occur and to better understand why parental size influences inbreeding depression in some traits but not others.     

Development and the effects of extended parenting in the cold‐breeding burying beetle Nicrophorus sayi

1. Burying beetles (Nicrophorus spp.) provide an excellent model system to test predictions about the relationships between environment, life‐history and behaviour. All species in the genus display similar natural histories, breeding on vertebrate carcasses and providing parental care to developing offspring. However, variations in other aspects of species' ecologies provide a rich framework to examine the evolution of parental behaviours and other traits. 2. One little‐studied species, N. sayi, breeds in substantially colder temperatures than its congeners, creating a potentially harsh environment for offspring. Here, we examined the timing of reproductive and developmental events in this species, and also investigated the effects of removing parents on offspring performance. 3. We find that development is not only extremely slow in this species, but it is also delayed even in comparison to other burying beetles reared at similar temperatures. However, the presence of parents reduces the time that offspring take to leave the carcass. This decrease in development time does not appear to result in a trade‐off with mortality or body size. 4. From these results, we suggest that very slow development may be advantageous when living in a particularly cold environment. Additionally, one role of extended parental care may be to assist offspring in dealing with these harsh conditions, and to mitigate the potentially negative consequences of adopting such a slow life‐history strategy.     

High rates of extra‐pair paternity in a socially monogamous beetle with biparental care

1. Nest construction and paternity assurance are predicted to favour biparental care in insects. The horned passalus (Odontotaenius disjunctus) is a socially monogamous beetle with biparental care that breeds in decaying logs. The genetic mating system of the horned passalus was investigated to determine if paternity assurance is likely to drive the evolution or maintenance of paternal care in this system. Parental time budgets were also examined to better understand the types and frequencies of behaviours performed by parents. 2. Genotyping‐by‐sequencing revealed high levels of extra‐pair paternity, with 54.8% of offspring sired by extra‐pair males and 70% of nests containing extra‐pair young. 3. More heterozygous social males were cuckolded less than more homozygous social males. Extra‐pair mating, however, seems unlikely to increase offspring genetic diversity as extra‐pair offspring were not more heterozygous than within‐pair offspring, and average brood heterozygosity did not increase with higher rates of extra‐pair paternity. 4. Behavioural observations demonstrated that parents spent on average 46.5% of their time processing the decaying wood resource for larval offspring. Because resource processing is a by‐product of feeding and provides shareable benefits for all larvae in the brood, this form of paternal care could be favoured despite low paternity.     

Model parents: is full compensation for reduced partner nest attendance compatible with stable biparental care?

Previous models have suggested that biparental care will beevolutionarily stable when each parent only partially compensatesfor decreases in effort by their partner. We investigated asystem where breeding success is an accelerating function ofparental effort. This could occur in species with a high predationlevel—for example, in a dense sea-bird colony or in specieswhere eggs or young are very prone to cooling. In these caseswe found that parents will fully compensate for decreased partnereffort, or else they will abandon the breeding attempt altogether.We use a second graphical model to show that biparental carecan exist under a situation of full compensation for reducedpartner effort if neither parent can do all the care alone.Each parent will abandon the breeding attempt if his or hercondition falls below a certain threshold. If the participationof both parents is necessary for the breeding attempt to besuccessful, then neither parent will want to force their partnerto abandon by making them work so hard that they fall belowthe condition threshold. Because abandonment by oen partnermeans the failure of the breeding attempt, each individualwill do at least enough work so that the partner will not abandon,resulting in biparental care. There will be a region of conflictbetween the parents, within which the conflict can be resolvedin various ways. Possible resolutions of this conflict, andthe consequences and applications of the model, are discussed.     

Effects of parental body condition and size on reproductive success in a tenebrionid beetle with biparental care

Abstract. 1. The beetle Parastizopus armaticeps (Coleoptera: Tenebrionidae) inhabits the Kalahari desert of southern Africa, constructs breeding burrows after rainfall, and shows extensive biparental care. Previous work has shown that it is predominantly male size, not female size, that determines breeding success; however, in the field these beetles show size assortative mating. This might obscure or override effects of female size on reproduction. Moreover, the inaccessibility of the breeding burrows makes it impossible to test effects of female and male size on offspring development and survival before adulthood. 2. To disentangle the effects of male and female length, body mass, and body condition on reproductive success, males and females were paired randomly in small breeding cages in the laboratory (n = 887 breeding pairs). The construction of the breeding cages allowed a clear view of the brood chamber contents at each stage in offspring development. Larva, pupa, and imago numbers and development were monitored daily, and imago mass at hatching from the pupa (hatchlings), offspring mass, and offspring body length at complete exoskeleton melanisation (juveniles) were determined. 3. There was a weak positive correlation between body condition and body length for females only. Breeding chronology was related to male body condition: males in better condition were fast to start and finish a breeding bout. Males in better condition produced heavier hatchlings and juveniles, and larger‐sized males produced larger‐sized juveniles. In contrast, numbers of larvae and juveniles produced were determined mainly by female length and body condition: larger females in better condition hatched more larvae and produced more offspring. 4. The results suggest that male size and condition will be the most important determinant of reproductive success under relatively dry conditions, when burrow length is critical for reproductive success. Female size might be more important for the pair's reproductive success under wet breeding conditions, when burrow length is less critical for successful reproduction.     

Parental care influences social immunity in burying beetle larvae

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Diapause incidence of progeny in relation to parental geographic origin,host plant and rearing density in the cabbage beetle,Colaphellus bowringi

The cabbage beetle, Colaphellus bowringi Baly (Coleoptera: Chrysomelidae), which is widely distributed in China, undergoes an imaginal diapause in the soil. In this study, we investigated the influences of parental geographic origin, host plant, and rearing density on the diapause incidence of progeny in this beetle. In studies conducted at 25 °C and L12:D12 photoperiod, the proportions of adults entering diapause were significantly different among latitudes from which the parents had been collected. The incidence of diapause increased with increasing latitude. Reciprocal cross tests between post‐diapause adults from different latitudes showed that there were significant differences in diapause incidence between pure‐bred and hybrid adults, suggesting that diapause incidence among progeny was determined by both the female and male, although the female appeared to have a stronger effect than the male. These results revealed that parental origin has an important influence on progeny diapause. Parental host plant species not only affected diapause incidence of the current generation, but also affected the incidence of diapause in the progeny produced by the non‐diapause parents; yet, the parental host plant had no influence on the incidence of diapause in the progeny produced by the post‐diapause parents. Rearing density of the parental generation had no significant effect on the incidence of diapause in the progeny.     

The cost of polygyny and the evolution of female care in poison frogs

Previous research on a variety of organisms indicates that polygyny can impose a cost on the reproductive success of females. Some authors have hypothesized that this cost may have caused the evolution of female parental care from paternal or biparental care in some lineages, particularly in poison frogs of the genus Dendrobates. In this paper, we evaluate the assumptions and theoretical implications of this hypothesis and present several game-theoretic models that clarify some of the issues. We conclude that a cost of polygyny is unlikely to drive a female care strategy to fixation on its own; however, if caring males suffer a cost of lost mating opportunities then a cost of polygyny may destabilize male care and result in the evolution of uniparental female care. A cost of polygyny on its own may be able to drive a transition from male care to biparental care. We also discuss other factors that may have influenced the evolution of parental care in the poison frogs, including results from recent field and laboratory research, and we evaluate the possibility that female care evolved from biparental, as opposed to male care.     

Plastic adjustments of biparental care behavior across embryonic development under elevated temperature in a marine ectotherm

Phenotypic plasticity in parental care investment allows organisms to promptly respond to rapid environmental changes by potentially benefiting offspring survival and thus parental fitness. To date, a knowledge gap exists on whether plasticity in parental care behaviors can mediate responses to climate change in marine ectotherms. Here, we assessed the plasticity of parental care investment under elevated temperatures in a gonochoric marine annelid with biparental care, Ophryotrocha labronica, and investigated its role in maintaining the reproductive success of this species in a warming ocean. We measured the time individuals spent carrying out parental care activities across three phases of embryonic development, as well as the hatching success of the offspring as a proxy for reproductive success, at control (24℃) and elevated (27℃) temperature conditions. Under elevated temperature, we observed: (a) a significant decrease in total parental care activity, underpinned by a decreased in male and simultaneous parental care activity, in the late stage of embryonic development; and (b) a reduction in hatching success that was however not significantly related to changes in parental care activity levels. These findings, along with the observed unaltered somatic growth of parents and decreased brood size, suggest that potential cost‐benefit trade‐offs between offspring survival (i.e., immediate fitness) and parents'' somatic condition (i.e., longer‐term fitness potential) may occur under ongoing ocean warming. Finally, our results suggest that plasticity in parental care behavior is a mechanism able to partially mitigate the negative effects of temperature‐dependent impacts.