Gillespie eco‐evolutionary models (GEMs) reveal the role of heritable trait variation in eco‐evolutionary dynamics

Heritable trait variation is a central and necessary ingredient of evolution. Trait variation also directly affects ecological processes, generating a clear link between evolutionary and ecological dynamics. Despite the changes in variation that occur through selection, drift, mutation, and recombination, current eco‐evolutionary models usually fail to track how variation changes through time. Moreover, eco‐evolutionary models assume fitness functions for each trait and each ecological context, which often do not have empirical validation. We introduce a new type of model, Gillespie eco‐evolutionary models (GEMs), that resolves these concerns by tracking distributions of traits through time as eco‐evolutionary dynamics progress. This is done by allowing change to be driven by the direct fitness consequences of model parameters within the context of the underlying ecological model, without having to assume a particular fitness function. GEMs work by adding a trait distribution component to the standard Gillespie algorithm – an approach that models stochastic systems in nature that are typically approximated through ordinary differential equations. We illustrate GEMs with the Rosenzweig–MacArthur consumer–resource model. We show not only how heritable trait variation fuels trait evolution and influences eco‐evolutionary dynamics, but also how the erosion of variation through time may hinder eco‐evolutionary dynamics in the long run. GEMs can be developed for any parameter in any ordinary differential equation model and, furthermore, can enable modeling of multiple interacting traits at the same time. We expect GEMs will open the door to a new direction in eco‐evolutionary and evolutionary modeling by removing long‐standing modeling barriers, simplifying the link between traits, fitness, and dynamics, and expanding eco‐evolutionary treatment of a greater diversity of ecological interactions. These factors make GEMs much more than a modeling advance, but an important conceptual advance that bridges ecology and evolution through the central concept of heritable trait variation.     

The influence of cadmium,copper, lead,and zinc on the distribution and evolution of metallophytes in the British Isles

Mine spoils and other soils contaminated with cadmium, copper, lead and zinc show natural colonization by species which have strategies of avoidance or tolerance of metal toxicities. The distribution of plants on such substrata in the British Isles is examined in the light of present knowledge of such strategies. Evolutionary processes mediating the selection of tolerant individuals and ecotypic differentiation of adapted populations on metalliferous soils are considered. Other factors determining which species can and which cannot evolve tolerance include constitutional differences in species sensitivity to toxic metals, and phenotypic (environmentally-induced) tolerances. The importance of constitutional properties and phenotypic responses in providing explanations for plant distribution on metalliferous soils is assessed.     

Dynamics of Concomitant Field Populations of Hoplolaimus columbus and Meloidogyne incognita

From the fall of 1968 through the summer of 1973, a Georgia cotton field with a lengthy history of the Cotton Stunt Disease Complex was sampled for the presence of plant parasitic nematodes. Although Meloidogyne incognita was recovered on all sampling dates, concomitant populations of Hoplolaimus columbus were not recovered until the spring of 1970. During the succeeding four growing seasons, the population density and horizontal distribution of H. columbus increased, and H. columbus replaced M. incognita as the predominant phytopathogenie species. A second Georgia cotton field containing concomitant populations of H. columbus and M. incognita was observed from the fall of 1971 through the summer of 1973. In this case the horizontal distribution of both species remained relatively constant and the population density of H. columbus increased steadily. In both locations, the presence of either H. columbus or M. incognita significantly inhibited the presence of the concomitant species. In general, however, the initial spring or final fall population densities of H. columbus or M. incognita had no significant influence on the population density of the concomitant species, The data are also discussed in relation to the biological significance of H. columbus in the southeastern coastal plain.     

Globin evolution was apparently very rapid in early vertebrates: A reasonable case against the rate-constancy hypothesis

Kimura mistook ambiguous maximum parsimony codons for wrong codons. The maximum parsimony method performed well as judged by the two classes of serine codons (which can not be connected by silent mutations) on comparing the parsimony codons for serines in human, rabbit, and mouse hemoglobin chains to actual codons determined by nucleotide sequencing. In genealogical reconstructions involving 247 eucaryotic globins, the maximum parsimony distances separating the contemporary sequences show that Kimura's Poisson and Dayhoff's PAM estimates of rate of globin evolution miss most of the superimposed replacements and are therefore seriously in error. Nor is Kimura's constant rate assumption and his belief in a single origin of myoglobin supported. Lamprey myoglobin appears to be most like lamprey hemoglobin, while gnathostome myoglobin seems closest to gnathostome hemoglobin. It was found that the three types of gnathostome globins (Mb, Hb, Hb) evolved between the shark-boney vertebrate and bird-mammal ancestors at a much faster rate than from the latter ancestor to the present. The data indicate that rates were exceedingly fast during the origin of these globin chains because a high proportion of substitutions were adaptive. It was concluded that wherever strong stabilizing selection acts on a protein, somewhere in the past positive Darwinian selection must have spread the amino acid substitutions now being preserved.     

人线粒体DNA的信息结构

本文报道了运用FORTRAN-77语言,在SIRIUS-1微机上计算遗传信息的冗余结构D_1、D_2、D_3的程序。计算出人线粒体DNA(16569个核苷酸残基)的H_1=1.930554,H_2=3.849254,H_3=5.760944,D_1=0.069446,D_2=0.011853,D_3=0.007011。 D_1、D_2的结果表明,人线粒体DNA的信息结构远比脊椎动物DNA的低级,这支持线粒体的共生起源学说。并对D_3的结果进行了分析,对其意义作了初步探讨。     

The spatial precision of the honey bees' dance communication

Many social insect species that employ directional recruitment to food finds communicate the location of their targets with seemingly needless imprecision. Here we present evidence that the spatial precision of the honey bees' dance communication has been tuned by selection so that recruits are neither so accurate that they usually find areas which have already been depleted nor so inaccurate that they usually fail to find the advertised resources altogether. First, the bees' distance errors are similar in magnitude to their directional errors, and their angular errors decrease greatly with increasing distance to the target (decreasing more than fourfold between 100 and 700 m). As a result, the absolute scatter of recruits remains relatively constant with changing distance to the target (increasing by less than 50% between 100 and 700 m). This is to be expected if the optimal level of imprecision is the same for distance and direction and does not change with the distance of the target from the nest. Second, comparative studies involving three tropical- and one temperate-zone species (all Apis)suggest that the precision of the bees' languages may have been tuned in accordance with the spatial characteristics of the resources each species uses. We suggest that both the round dance, which conveys no directional information for nearby targets, and the high angular divergence in waggle dances indicating targets within several hundred meters of the colony are both understandable in this context.     

Evolutionary relationships between mono- and polystiliferous hoplonemerteans: Nipponnemertes (Cratenemertidae), a “missing link” genus?

Histological studies on several species of the monostiliferous hoplonemertean genus Nipponnemertes show that they share certain significant features with reptantic Polystilifera. A brief survey of these features provides a basis for an analysis of possible evolutionary relationships between mono- and polystiliferous Hoplonemertea. It is suggested that ancestral enoplans possessed a rhynchocoel wall containing two muscle layers and a simple protopolystiliferous type of proboscis armature, and that this ancestral pool gave rise to two distinct evolutionary lineages, one leading to cratenemertid, group 2 terrestrial and freshwater, and polystiliferous hoplonemerteans, the other to the typical modern monostiliferous forms. A reclassification of the Enopla is proposed.     

A gating mechanism for sound pattern recognition is correlated with the temporal structure of echolocation sounds in the rufous horseshoe bat

Summary The rufous horseshoe bat, Rhinolophus rouxi, was trained to discriminate differences in target distance. Loud free running artificial pulses, simulating the bat's natural long-CF/FM echolocation sounds, interfered with the ability of the bat to discriminate target distance. Interference occurred when the duration of the CF component of the CF/FM artificial pulse was between 2 and 70 ms. A brief (2.0 ms) CF signal 2–68 ms before an isolated FM signal was as effective as a continuous CF component of the same duration. When coupled with the bat's own emissions, a 2 ms FM sweep alone was effective in interfering when it came 42 to 69 ms after the onset of the bat's pulse. The coupled FM artificial pulses did not interfere when they began during the bat's own emissions.It appears that the onset of the CF component activates a gating mechanism that establishes a time window during which FM component signals must occur for proper neural processing. A comparison with a similar gating mechanism in Noctillo albiventris, which emits short-CF/FM echolocation sounds, reveals that the temporal parameters of the time window of the gating mechanism are species specific and specified by the temporal structure of the echolocation sound pattern of each species.Abbreviations FM frequency modulated - CF constant frequency     

Components of positional information in the developing wing margin of the Lyra mutant of Drosophila

Summary A number of parameters characteristic of the wing margin precursor in imaginal discs of Drosophila are known: the zone of non-proliferating cells or ZNC (O'Brochta and Bryant 1985), aldehyde oxidase (AO) and other enzyme staining patterns (Sprey et al. 1982), E1C antigen localization in a narrow band along the margin (Piovant and Lena 1988). To test our hypothesis that such parameters, and others, act in concert to determine margin identity and the positional information that specifies the bristles and hairs appropriate to the anterior, posterior and distal margins, we have examined these parameters in the dominant mutant Lyra, in which much of the anterior and posterior margins is missing. After establishing that Lyra phenotype is already evident in the early pupal wing, we tested the known imaginal disc parameters and found that only Mab E1C (Piovant and Lena 1988) distribution differs from wild type, suggesting that E1C antigen may be a component of positional information. Sibatani's (1983) model for specification of positional information (PI) applied to wing discs predicts the Lyra adult wing shape as well as the reduced distribution of E1C antigen in Lyra wing discs. The model is based on the assumption that specification of positional information depends on interactions of multiple, independent factors. Clonal analysis with shaggy (Simpson et al. 1988 and Ripoll et al. 1988) indicates that factors in addition to E1C antigen contribute to margin PI in Lyra wings and should allow us to test the multi-component hypothesis further.