Biological Journal of the Linnean Society

THORPE, R. S.; BROWN, R. P.

doi: 10.1111/j.1095-8312.1989.tb01580.xpmid: N/A

This study of the microgeographic variation in the colour pattern of the lizard, Gallotia galloti, within Tenerife has three facets. One, an analysis of the population distribution and density in relation to physical conditions; two, univariate and multivariate descriptions of the pattern of geographic variation; and three, formal testing of a range of causal hypotheses for these geographic patterns. The range is not divided into separate allotheses high‐ and low‐altitude populations by a inaptitude ring of ground‐level cloud although there is a drop in population‐density in the middle altitudes. Multiple regression indicates that, or the factors measured, this is primarily due to a decrease in insolation. The pattern of geographic variation in the six independent colour pattern characters is portrayed by contouring the 67 locality means. There is generally good congruence among these patterns and a canonical analysis indicates that the generalized pattern of geographic variation is largely unidimensional and can therefore be represented adequately by (and portrayed by contouring) the first canonical variate. Seven causal hypotheses, from a range of possible and previously suggested causes, are considered. The procedure for testing these hypotheses should depend on their dimensionality and that of the observed pattern. Since all the observed and hypothesized patterns are basically unidimensional the seven hypothesized patterns were simultaneously tested against each observed pattern (individual characters and canonical variate) by partial correlation. All the previously suggested ‘phylogenetic’ hypotheses based on divergence in allopatry are rejected. The hypotheses that the geographic variation in the colour pattern is caused by the topographically determined climate cannot be rejected. The character state changes can be explained by a balance between sexual selection for ‘attractive’ colouration and natural selection, via predation, for cryptic colouration.

DENNIS, R. L. H.; SHREEVE, T. G.

doi: 10.1111/j.1095-8312.1989.tb01581.xpmid: N/A

Gradients (isophenes) in modifications of butterfly wing morphology (colour, pattern, size) to the north and west of Britain are shown to correlate closely with contemporary environmental gradients, whereas their alleged formation as infra‐specific units in Devensian refugia off western Britain is unsubstantiated. A model is described which explains the transformation in phenotypes in relationship to climate, especially ambient temperatures and radiation levels. In cooler, less predictable summer conditions to the north and west, selection has favoured modifications in adult phenotypes that maintain efficiency in thermoregulation, mate advertisement and predator escape. The form that wing modifications take depends mainly on basking posture (lateral, dorsal‐absorption and reflectance), which determines the allocation and interaction of functions on different wing surfaces. It is also dependent on hostplant‐habitat structure, which influences thermal stability and the milieu of predators and conspecifics, and other behavioural norms (mate‐locating behaviour) and biological attributes (size, robustness, speed and mode of flight, chemical defences) which affect their relationships with predators and conspecifics. The significance of Quaternary palaeoenvironments to phenetic transformations is discussed as is the relevance of the model to the development of phenotypes in arctic endemic butterflies. Differences in phenotypes of butterflies which occupy arctic and temperate montane environments are also predicted by the model.

RIDLEY, MARK

doi: 10.1111/j.1095-8312.1989.tb01582.xpmid: N/A

The paper tests, by the comparative method, four hypotheses to explain why the degree of sperm displacement differs in different insect species. It summarizes evidence for 57 species. Here are the four hypotheses: species with mating plugs should show low sperm displacement, and species without plugs high displacement (Boorman & Parker); species with spheroid spermathecas should show low displacement, species with elongate spermathecas high displacement (Walker); species with low paternal investment should show low sperm displacement, species with high paternal investment high displaycement (Gwynne); and species with low natural mating frequencies should show low displacement, species with high mating frequencies high displacement (this paper). The spermathecal shape hypothesis is of limited theoretical plausibility; but the other ideas are theoretically possible. The evidence, if numbers of species are counted, generally fits all four theories; but, in a statistically more rigorous cladistic test, it significantly supports only the mating frequency theory.

NODZENSKI, EDWARDINE; WASSERSUG, RICHARD J.; INGER, ROBERT F.

doi: 10.1111/j.1095-8312.1989.tb01583.xpmid: N/A

Tadpoles face severe packing constraints on viscera within the pleuro‐peritoneal cavity because of their extremely short torsos—a feature they share with adult anurans—and the concomitant need for relatively slender torsos for efficient locomotion. We examined the effects of differences in body form and habits on the size, shape and development of viscera in three kinds of sympatric, stream‐associated pelobatid tadpoles. Leptobrachium montanumlarvae are generalized, wide, deep‐bodied tadpoles. Larval Leptolalax gracilis are very slender and live in the crevices between rocks on the bottom of riffles. Larval Megophrys nasuta are intermediate between the other two in body form, and live with L. montanum in a variety of microhabitats but feed at the surface film. In all three species, liver, gall bladder, arid kidneys begin development early and grow isometrically throughout larval life. The gut and pancreas have a growth spurt shortly after hatching, then grow at a constant rate until near metamorphosis when both shrink drastically. The spleen grows at a slower rate than the body throughout the larval period. Lungs do not appear in L. gracilis until the tadpole approaches metamorphosis, which accords with its benthic habits, whereas they grow throughout the larval period in L. montanum and M. nasuta. In M. nasuta, however, the lungs are unusually wide anteriorly; this shifts buoyancy forward and facilitates the head‐up feeding posture characteristic of that species. Gonads appear early in L. montanum and L. gracilis, but not until near metamorphosis in M. nasuta. We suggest that accelerated gonadal development in tadpoles characterizes species that metamorphose close to their size at first reproduction. Leptobrachium montanum, with the bulkiest body and most generalized habits, has relatively and absolutely the largest gut, liver (x of combined gut and liver volume = 24%, of total volume), and kidneys. Leptolalax gracilis, the most slender tadpole, has relatively the smallest combined gut and liver volume (x = 10% of total volume). Other premetamorphic differences among the species were observed in gut coiling, liver, pancreas and kidney shape and left/right asymmetry of urogenital organs. The major interspecific differences we observed in the size, shape, and developmental patterns of viscera in tadpoles are clearly related to interspecific differences in torso shape, microhabitat distribution and mode of feeding.

BRAKER, H. ELIZABETH

doi: 10.1111/j.1095-8312.1989.tb01584.xpmid: N/A

Most members of the superfamily Acridoidea (Orthoptera) oviposit in the soil, but some species oviposit directly on or in tissue of host plants. Oviposition in association with host plants has been reported for only 6% of acridoid species for which oviposition behaviour is known, hut the behaviour is systematically and geographically widespread, including members of two families and seven acridid subfamilies on three continents. This distribution suggests that host plant oviposition by grasshoppers has evolved independently at least eleven times in the world's grasshoppers fauna. A comparative approach to investigating oviposition on host plants shows that it tends to occur in species of inundated habitats and tropical forests, in species with narrow diets, and is correlated with a reduction in clutch size.