Why do Luehdorfia butterflies lay eggs in clusters?

Luehdorfia butterflies lay eggs in clusters. Clones of their host plants (Asiasarum and Heterotropa) are distributed pacthily among the understory of deciduous forests. Groups of Luehdorfia larvae often exhaust the clones and may wander over the forest floor seeking new clones. The highest mortality observed is during this wandering period. To elucidate why Luehdorfia butterflies lay eggs in clusters, a simulation experiment was made for hypothetical populations which lay eggs in clusters or singly. Field data on larval mortality, consumption, density of host clones and leaf weight for Luehdorfia japonica were incorporated into the model. The predictions of the simulation were: (1) When the egg density is low, the single egg type could leave many more pupae than the egg clustering type, but when the egg density is high, the former might leave smaller number of pupae than the latter; and (2) There are optimal sizes of egg clusters for different egg densities and the optimal size becomes larger as the egg density increased.     

Why do older workers have problems with technology?

Why do older workers seem to have problems with technology? In this paper, I will review several possible reasons and illustrate them with evidence, often anecdotal, from our work as ergonomics practitioners. We find that older workers have more to "unlearn" from their accumulated experience. They may suffer from gradual or not so gradual ailing faculties of sight, hearing, dexterity, stamina, memory, and reaction time. They may exhibit a fear of making mistakes, and they may have strongly established preferences and pessimism about technological gimmicks. But the real problem is often that the designers have failed to anticipate the requirements of their users; they have failed to design for a range of abilities broader than their own; they have failed to test their designs with real people; and they have failed to learn from the experience of the market. Getting design right for older users is really only a continuation of getting design right for all.     

Why do Red-winged Blackbrids accept eggs of Brown-headed Cowbirds?

Summary Avian brood parasites usually severely depress the reproductive success of their hosts, yet many host species, including those presumably capable of ejecting parasitic eggs, accept them. Female, brood-parasitic, Brown-headed Cowbirds typically remove a host egg when they lay their own and damage some host eggs in the process of ejecting a host egg. Data from a field study of Red-winged Blackbirds show that these costs, which cannot be avoided by ejecting the parasitic egg, account for some of the reproductive losses attributable to parasitism, but part is due to the presence of the cowbird egg in the nest. To assess whether ejection would be favoured under current circumstances, the probable damage a female Redwing could cause to her own eggs by attempting to eject a cowbird egg needs to be determined.     

Why do female lizards lay their eggs in communal nests?

1. In many reptile species, females oviposit communally (i.e. many clutches are laid within the same nest). This behaviour might result from constraint (scarcity of nest-sites offering suitable incubation conditions) or adaptation (direct fitness benefits accruing from the proximity of other eggs). 2. To test between these alternatives, we gathered field and laboratory data on montane scincid lizards Bassiana duperreyi from south-eastern Australia. Our data support the adaptationist hypothesis. 3. In the field, communal vs. solitary clutches were laid in similar sites, and the relative frequency of communal nesting was not predictable from nest-site availability. Thermal regimes for incubation did not differ between communal vs. solitary nests, nor between eggs at the core vs. periphery of a communal nest. In the laboratory, females selectively oviposited beside existing eggs rather than in otherwise identical potential nesting sites. 4. From cycling-temperature incubation in the laboratory, eggs incubated within a cluster of other eggs took up less water, but produced hatchlings that were larger and faster-running than were hatchlings from eggs incubated alone. 5. Hydric modifications of incubation conditions within a cluster of tightly packed eggs thus may provide a direct fitness benefit to communal oviposition.     

Why don't birds lay more eggs?

Fifty years ago David Lack put forward a key hypothesis in life-history theory: that avian clutch is ultimately determined by the number of young that parents can provide with food. Since then, a plethora of brood manipulations has shown that birds can rear more young than the number of eggs they lay, and prompted a search for negative effects of increased effort on future reproduction. However, recent studies have shown that the demands of laying and incubating eggs generally omitted from experiments, could affect parental fitness. Lack's hypothesis, and the tests of its validity, need to be extended to encompass the full demands of producing and rearing the brood.     

Why do species exist? Insights from sexuals and asexuals

Why does life diversify into the more or less discrete entities we recognise as species? Two main explanations have been proposed: i) species are a consequence of adaptation to different ecological niches, ii) species are a consequence of sexual reproduction and reproductive isolation. Phylogenetic studies of case-study groups can provide insights into the relative importance of divergent selection and isolation for speciation, but it can be difficult to infer causes of speciation unambiguously. The example of North American tiger beetles from the genus Cicindela is discussed. An alternative approach is to compare diversification between related sexual and asexual taxa to infer the relative importance of the two explanations. We outline expected patterns of diversification in sexual and asexual lineages under different scenarios using coalescent theory. Whether sexuals or asexuals diversify to a greater extent depends on the balance among various stages of diversification, particularly on the effects of sexual reproduction on rates of adaptive evolution. Rotifers offer a unique system to test these ideas, allowing comparison of patterns of genetic and functional morphological diversification in sexual (bdelloid) and asexual (monogonont) clades.     

Why are birds’ eggs speckled?

Birds are unique in laying eggs with pigmented shells, but for most species (e.g. most passerines, which lay white eggs speckled with reddish spots of protoporphyrin) the pigments’ function is unknown. We studied a bird population at a geologically variable site, and considered a hitherto untested hypothesis: that protoporphyrin pigments might compensate for reduced eggshell‐thickness (caused partly by calcium deficiency), which is known to reduce eggshell‐strength and increase eggshell‐permeability. We found that pigment spots specifically demarcated thinner areas of shell, with darker spots marking yet thinner shell than paler spots. Variation in pigmentation was thus associated with variation in shell thickness both within and between clutches, so accounting for the eggshell's characteristic spot patterns. Geological variability at this site has resulted in a great range of calcium availability and, as predicted by the hypothesis, variation in calcium availability was found to affect between‐clutch variation in both eggshell‐mass (+) and pigmentation characteristics (?). We suggest a physiological mechanism and some important implications of these findings.     

Why do animals hybridize?

Animal hybridization is increasingly recognized as common and evolutionarily important, but the role of behavior in promoting hybridization events is not well understood. Understanding the behavioral causes of hybridization requires understanding the ecological, demographic, and phenotypic influences on mate choice in hybridizing taxa. Here, I review how these influences on mate choice can contribute to hybridization by (1) circumventing (female) choice, (2) bringing formerly isolated species into sympatry, (3) masking cues important for mate recognition, (4) altering the traits or preferences involved in mate recognition, or (5) altering the costs and benefits of mate choice. In particular, hybridization in response to either high direct costs of mate choice or high direct benefits of heterospecific mating may be widespread, a possibility that awaits further testing. Adopting a mate choice perspective to the study of hybridization challenges the assumption of hybrids as reproductive “mistakes” and allows for functional explanations regarding the occurrence and maintenance of hybridization. As evidence of the prevalence and evolutionary importance of animal hybridization accumulates, investigations into the role of behavior will be increasingly important for our understanding of diversification and for conservation applications.     

Why do plants silicify?

Despite seminal papers that stress the significance of silicon (Si) in plant biology and ecology, most studies focus on manipulations of Si supply and mitigation of stresses. The ecological significance of Si varies with different levels of biological organization, and remains hard to capture. We show that the costs of Si accumulation are greater than is currently acknowledged, and discuss potential links between Si and fitness components (growth, survival, reproduction), environment, and ecosystem functioning. We suggest that Si is more important in trait-based ecology than is currently recognized. Si potentially plays a significant role in many aspects of plant ecology, but knowledge gaps prevent us from understanding its possible contribution to the success of some clades and the expansion of specific biomes.     

Why do neonates of aphidophagous ladybird beetles preferentially consume conspecific eggs in presence of aphids?

The neonates of aphidophagous ladybird beetles, Propylea dissecta, Coccinella transversalis and Coelophora saucia preferentially consumed conspecific eggs in presence of essential aphid prey, Aphis gossypii. This preference was strongest in P. dissecta and recorded in all density combinations of conspecific eggs and aphids. The neonates of all three species developed faster resulting in heavier second instars with lower mortality when fed on conspecific eggs as compared to mobile or defenceless aphids. In addition, they required less dry biomass of conspecific eggs than that of aphids. These results reveal that neonates are benefitted intrinsically when they feed on conspecific eggs. The neonates of P. dissecta exhibited discrimination for more nutritious food, as they contacted and ate conspecific eggs more frequently than aphids as their first meal. This discrimination was not found in Coccinella transversalis and Coelophora saucia possibly due to their bigger sizes and possible higher energy requirements. Although, the major effect of chemical cues was only noticed in P. dissecta, it could be concluded that chemicals (surface and within) of conspecific eggs possibly attract neonates for egg-cannibalism, as both eggs and aphids were consumed in greater numbers when coated with egg extracts. The reverse occurred when eggs and aphids were coated with aphid extracts.     

Why do RNA viruses recombine?

Recombination occurs in many RNA viruses and can be of major evolutionary significance. However, rates of recombination vary dramatically among RNA viruses, which can range from clonal to highly recombinogenic. Here, we review the factors that might explain this variation in recombination frequency and show that there is little evidence that recombination is favoured by natural selection to create advantageous genotypes or purge deleterious mutations, as predicted if recombination functions as a form of sexual reproduction. Rather, recombination rates seemingly reflect larger-scale patterns of viral genome organization, such that recombination may be a mechanistic by-product of the evolutionary pressures acting on other aspects of virus biology.     

Why do microorganisms produce rhamnolipids?

We review the environmental role of rhamnolipids in terms of microbial life and activity. A large number of previous research supports the idea that these glycolipids mediate the uptake of hydrophobic substrates by bacterial cells. This feature might be of highest priority for bioremediation of spilled hydrocarbons. However, current evidence confirms that rhamnolipids primarily play a role in surface-associated modes of bacterial motility and are involved in biofilm development. This might be an explanation why no direct pattern of hydrocarbon degradation was often observed after rhamnolipids supplementation. This review gives insight into the current state of knowledge on how rhamnolipids operate in the microbial world.     

Why do worms need cholesterol?

Cholesterol is a structural component of animal membranes that influences fluidity, permeability and formation of lipid microdomains. It is also a precursor to signalling molecules, including mammalian steroid hormones and insect ecdysones. The nematode Caenorhabditis elegans requires too little cholesterol for it to have a major role in membrane structure. Instead, its most probable signalling functions are to control molting and induce a specialized non-feeding larval stage, although no cholesterol-derived signalling molecule has yet been identified for these or any other functions.     

Why do proteins divide into domains? Insights from lattice model simulations

It is known that larger globular proteins are built from domains, relatively independent structural units. A domain size seems to be limited, and a single domain consists of from few tens to a couple of hundred amino acids. Based on Monte Carlo simulations of a reduced protein model restricted to the face centered simple cubic lattice, with a minimal set of short-range and long-range interactions, we have shown that some model sequences upon the folding transition spontaneously divide into separate domains. The observed domain sizes closely correspond to the sizes of real protein domains. Short chains with a proper sequence pattern of the hydrophobic and polar residues undergo a two-state folding transition to the structurally ordered globular state, while similar longer sequences follow a multistate transition. Homopolymeric (uniformly hydrophobic) chains and random heteropolymers undergo a continuous collapse transition into a single globule, and the globular state is much less ordered. Thus, the factors responsible for the multidomain structure of proteins are sufficiently long polypeptide chain and characteristic, protein-like, sequence patterns. These findings provide some hints for the analysis of real sequences aimed at prediction of the domain structure of large proteins.     

Why do symbiotic copepods matter?

Currently, less than 10% of the members of the World Association of Copepodologists are working actively on symbiotic copepods. This surprisingly small guild of workers is thought to result from a general lack of understanding of the importance of symbiotic copepods. Symbiotic copepods as a whole comprise more than one-third (4224/11956 or 35.33%) of known copepods. They are found not only in the five major orders of Copepoda (Calanoida, Harpacticoida, Cyclopoida, Poecilostomatoida and Siphonostomatoida), but also in association with all major phyla of marine animals, ranging from sponges up to mammals (cetaceans). Discussion on these subjects is augmented with information on the impact of symbiotic copepods on aquaculture, and their exhibition of unusual biological phenomena. It is concluded that copepodologists today need to pay more attention to the symbiotic copepods, if copepodology is to become a major subject of modern biological sciences.