Abdominal pigmentation in Drosophila melanogaster females from natural Indian populations

Females of Drosophila melanogaster collected from five geographically distant populations in India were analysed for the intensity of pigmentation in the 5th, 6th and 7th segments of the abdomen. In all three segments, this intensity was found to vary among individuals of any given population, and, furthermore, different populations differ with respect to this phenotypic trait. Statistical analysis revealed significant intra- and interpopulational variation. A clinical pattern was detected: females from populations closer to the equator tended to have lighter cuticle, in which case differences between the three segments could not be detected and all three segments responded both independently and jointly to latitudinal variation, as indicated by a statistically significant positive correlation between latitude and pigmentation score. This is the first report on abdominal pigmentation analysis in natural populations of D. melanogaster that provides evidence that phenotypic flexibility reflects temperature differences, as a result of which abdominal pigmentation shows geographic differentiation.     

Papyrus swamp development in the Upemba Basin, Zaïre: studies of population structure in Cyperus papyrus stands

The ecology and distribution of papyrus swamps are briefly reviewed together with the ecology, distribution structure and growth characteristics of Cyperus papyrus.
Three age-classes of culm are recognized and girth and density of each are recorded along transects through mree swamps in the Upemba Basin of Zaïre. A regression of culm-unit biomass on culm girth, developed for Ugandan swamps, is used to convert Upemba measurements into biomasses. It is shown that simple measurements, taken at only a single point in time, yield much information on both the structure and the dynamics of papyrus populations.
It is suggested that the standing-crops of such populations are determined by available light, and by local temperature regimes, and are therefore constant, irrespective of site quality (nutrient status), for any particular climatic zone. Culm-duration (life-time) is not significantly influenced by climate and the ratio culms/rhizomes provides a useful indicator of comparative productivity. Unlike community biomass, productivity can be limited by site quality.     

Analysis of cellular interactions in density-dependent inhibition of 3T3 Cell proliferation

Subpopulations of different proliferative status are determined during cell-density dependent proliferation of 3T3 cells. From these data the probability of conversion of proliferative to quiescent cells is derived and found to correlate well with published data on binding of growth-inhibiting factors secreted from growth-inhibited cells.Based on material presented at the Symposium Intercellular Communication Stuttgart, September 16–17, 1982     

A regression analysis of the summer population dynamics of Polyarthra vulgaris in a northern Michigan bog lake

The population dynamics of a planktonic rotifer (Polyarthra vulgaris) were examined in a brown water, acid lake in northern Michigan, U.S.A. Predation by Chaoborus punctipennis and low food (Navicula spp. and Cyclotella spp.) concentrations were the main factors limiting P. vulgaris populations of all factors examined. The data presented here support a hypothesis for zooplankton limitation by an invertebrate predator.     

Correlation of rotifer associations in a chain of lakes fed by reclaimed sewage

The quantitative composition of the rotifer fauna of seven interconnected lakes located in southern California was studied in a preliminary investigation. The lakes are fed by reclaimed sewage, and the water quality increases rapidly from the first lake, barely able to support life, to a series of lovely lakes stocked with fish and utilized for recreation. The Shannon index of rotifer population diversity showed an appropriate increase. Up to 24 – 28 different rotifer taxa in each lake provided a rich community dominated by Brachionids, Keratella and Trichocerca. The diversity and quantity of the rotifer association then declined again in the last lake. Comparison of the lakes using the Bray and Curtis index of similarity and cluster analysis supported the picture of a lake-chain evolution, a biotic development showing a maximum curve.     

Microevolution and taxonomy of European reptiles with particular reference to the grass snake Natrix natrix and the wall lizards Podarcis sicula and P. melisellensis

The grass snake Natrix natrix and the wall lizards Podarcis sicula and P. melisellensis are used as examples to compare the procedure and achievements of the conventional approach to naming subspecies with the use of multivariate morphometries to investigate racial differentiation.
The conventional procedure, which has changed little over the last 50 years, fails to take into account the appropriate evolutionary facts or refer to any abstracted levels of divergence necessary for subspecific recognition. Consequently, the patterns of population differentiation are obscured by the recognition of a large number of rather meaningless subspecies. There is a tendency to section clines into artificial categories and arbitrarily delimit subspecies by physiographic features.
On the other hand, the use of multivariate morphometries reveals the patterns of population differentiation which can be related to geological events and patterns of differentiation in other species and species groups. The nature of 'hybrid' zones and population differentiation enables the relative importance of evolutionary forces such as gene flow, selection and genetic drift to be discussed and provides evidence concerning speciation mechanisms. These techniques also contribute to the discussion regarding the nature of species and provide abstracted and operational criteria for taxonomic decisions.
The difference between the results of multivariate analysis and the conventional approach cannot be explained solely on the basis of choice of characters. Some of the advantages and disadvantages of using multivariate morphometries, as opposed to other modern techniques, for investigating racial affinities are discussed.     

Population dynamics of daphnia pulex and utilization by the rainbow trout (salmo gairdneri)

The effect of rainbow trout (Salmo gairdneri) predation on the population dynamics of the water flea,Daphnia pulex, was examined during 1976 and 1977 in Becker Lake, a small, shallow, productive reservoir in northeastern Arizona.Rainbow trout were size-biased feeders, utilizing daphnids which were 1.3 mm in size or larger. Trout predation uponDaphnia pulex occurred mainly during winter and early spring when their numbers were relatively low but their clutch size high, suggesting that trout selectedDaphnia on the basis of brood pigmentation. By far the greatest proportion ofDaphnia mortality was due to nonpredatory sources, since generally less than 6% could be attributed to trout predation.TheD. pulex population exhibited a bimodal seasonal abundance curve which was attributed to ephippial egg production and trout predation during the winter and poor food quality/quantity during the summer.This work was supported in part by the Arizona Department of Game and Fish. The authors wish to thank Jim Novy and Joe Stone of that department for their invaluable assistance in the field collecting segment of this study.     

Mortality differentials within large American cities in 1890

This article presents a multiple regression analysis of demographic and social data for 335 wards in 17 American cities in 1890. The most important findings are: (1) Density effects on mortality were uniformly positive and statistically significant; the magnitude of these effects was much greater for child mortality than for adult mortality; and child mortality was more sensitive to persons per dwelling than to persons per acre. (2) Unsanitary conditions, as measured by the city-specific typhoid fever death rate, significantly increased mortality and child mortality was much more sensitive in this respect than adult mortality. (3) Given the same age composition and population density, foreign-born whites, native-born whites, and the colored population had about the same adult death rate.     

Demographic responses to climate‐driven variation in habitat quality across the annual cycle of a migratory bird species

The demography and dynamics of migratory bird populations depend on patterns of movement and habitat quality across the annual cycle. We leveraged archival GPS‐tagging data, climate data, remote‐sensed vegetation data, and bird‐banding data to better understand the dynamics of black‐headed grosbeak (Pheucticus melanocephalus) populations in two breeding regions, the coast and Central Valley of California (Coastal California) and the Sierra Nevada mountain range (Sierra Nevada), over 28 years (1992–2019). Drought conditions across the annual cycle and rainfall timing on the molting grounds influenced seasonal habitat characteristics, including vegetation greenness and phenology (maturity dates). We developed a novel integrated population model with population state informed by adult capture data, recruitment rates informed by age‐specific capture data and climate covariates, and survival rates informed by adult capture–mark–recapture data and climate covariates. Population size was relatively variable among years for Coastal California, where numbers of recruits and survivors were positively correlated, and years of population increase were largely driven by recruitment. In the Sierra Nevada, population size was more consistent and showed stronger evidence of population regulation (numbers of recruits and survivors negatively correlated). Neither region showed evidence of long‐term population trend. We found only weak support for most climate–demographic rate relationships. However, recruitment rates for the Coastal California region were higher when rainfall was relatively early on the molting grounds and when wintering grounds were relatively cool and wet. We suggest that our approach of integrating movement, climate, and demographic data within a novel modeling framework can provide a useful method for better understanding the dynamics of broadly distributed migratory species.     

StructureSelector: A web‐based software to select and visualize the optimal number of clusters using multiple methods

Inferences of population genetic structure are of great importance to the fields of ecology and evolutionary biology. The program structure has been widely used to infer population genetic structure. However, previous studies demonstrated that uneven sampling often leads to wrong inferences on hierarchical structure. The most widely used ΔK method tends to identify the uppermost hierarchy of population structure. Recently, four alternative statistics (medmedk , medmeak , maxmedk and maxmeak ) were proposed, which appear to be more accurate than the previously used methods for both even and uneven sampling data. However, the lack of easy‐to‐use software limits the use of these appealing new estimators. Here, we developed a web‐based user‐friendly software structureselector to calculate the four appealing alternative statistics together with the commonly used Ln Pr(X|K) and ΔK statistics. structureselector accepts the result files of structure , admixture or faststructure as input files. It reports the “best” K for each estimator, and the results are available as HTML or tab separated tables. The program can also generate graphical representations for specific K, which can be easily downloaded from the server. The software is freely available at http://lmme.qdio.ac.cn/StructureSelector/ .