Geographic variation in the G matrices of wild populations of the barn swallow

In this paper, we present an analysis of genetic variation in three wild populations of the barn swallow, Hirundo rustica. We estimated the P, E, and G matrices for six linear morphological measurements and tested for variation among populations using the Flury hierarchical method and the jackknife followed by MANOVA method. Because of nonpositive-definite matrices, we had to employ 'bending' to analyse the G and E matrices with the Flury method. Both statistical methods agree in finding that the P and G matrices are significantly different but comparison between the analysis of the P matrices and pairwise analyses of the P, E, and G matrices suggests caution in interpreting the Flury results concerning differences in matrix structure. The significant variation among the populations in the G matrices appears to be due in large measure to the most geographically distant population.     

Extra-nuclear effects on growth and development in the sand cricket Gryllus firmus

Although largely ignored until recently, parental effects on the phenotypes of their offspring are both ubiquitous in nature and of a potentially great importance to evolution. Our study examines the presence of extra-nuclear (maternal and paternal) effects in growth traits, development time and adult size in the sand cricket Gryllus firmus using a diallel cross of inbred lines. Sex linkage was shown to be nonsignificant for development time but the other traits could not be tested. We assume that they are nonsignificant but use the term 'reciprocal' effects to include this effect. We show that reciprocal effects are present in the growth traits and development time, where they account for 10-30% of the phenotypic variance. They are not present in adult size as indexed by head width. We demonstrate that reciprocal effects are due, at least in part, to maternal effects by an analysis of the positive correlation between egg size, a maternal trait, and the growth traits. The growth rate traits show no significant decline with age either with respect to extra-nuclear contributions to variance or difference between phenotypic means of reciprocal pairs. This study demonstrates that extra-nuclear effects are important contributors to the phenotypic variation in life history traits of G. firmus.     

The common quantitative genetic basis of wing morphology and diapause occurrence in the cricket Gryllus veletis

A covariation between wing morphology and diapause occurrence has been observed in many insect species, but the genetic basis of this covariation has never been established. This study measures the heritability of, and genetic correlation between, these two ecologically important threshold traits in the cricket Gryllus veletis. A total of 81 full-sib families were reared in the laboratory to estimate these parameters. A comparison of laboratory and field samples showed that these two traits are highly plastic. The heritability of wing morphology was 0.25 (0.09), the heritability of diapause occurrence was 0.77 (0.11) and the genetic correlation between them was 0.61 (0.19). These estimates did not differ between males and females. The significance of these quantitative genetic parameters is discussed with reference to the monomorphism of natural populations of G. veletis for diapause occurrence and with reference to the trade-off between the ability to disperse by flight and the ability to diapause found in at least one closely related species. A survey of the literature reveals that genetic correlations between diapause occurrence or wing morphology and various other traits are common in insects, suggesting that these two traits are often genetically integrated in insect life-histories.     

The Niemann-Pick C1 protein resides in a vesicular compartment linked to retrograde transport of multiple lysosomal cargo

Niemann-Pick C disease (NP-C) is a neurovisceral lysosomal storage disorder. A variety of studies have highlighted defective sterol trafficking from lysosomes in NP-C cells. However, the heterogeneous nature of additional accumulating metabolites suggests that the cellular lesion may involve a more generalized block in retrograde lysosomal trafficking. Immunocytochemical studies in fibroblasts reveal that the NPC1 gene product resides in a novel set of lysosome-associated membrane protein-2 (LAMP2)(+)/mannose 6-phosphate receptor(-) vesicles that can be distinguished from cholesterol-enriched LAMP2(+) lysosomes. Drugs that block sterol transport out of lysosomes also redistribute NPC1 to cholesterol-laden lysosomes. Sterol relocation from lysosomes in cultured human fibroblasts can be blocked at 21 degrees C, consistent with vesicle-mediated transfer. These findings suggest that NPC1(+) vesicles may transiently interact with lysosomes to facilitate sterol relocation. Independent of defective sterol trafficking, NP-C fibroblasts are also deficient in vesicle-mediated clearance of endocytosed [14C]sucrose. Compartmental modeling of the observed [14C]sucrose clearance data targets the trafficking defect caused by mutations in NPC1 to an endocytic compartment proximal to lysosomes. Low density lipoprotein uptake by normal cells retards retrograde transport of [14C]sucrose through this same kinetic compartment, further suggesting that it may contain the sterol-sensing NPC1 protein. We conclude that a distinctive organelle containing NPC1 mediates retrograde lysosomal transport of endocytosed cargo that is not restricted to sterol.     

VARIATION IN GENETIC ARCHITECTURE OF CALLING SONG AMONG POPULATIONS OF ALLONEMOBIUS SOCIUS,A. FASCIATUS,AND A HYBRID POPULATION: DRIFT OR SELECTION?

Predictions using quantitative genetic models generally assume that the variance-covariance matrices remain constant over time. This assumption is based on the supposition that selection is generally weak and hence variation lost through selection can be replaced by new mutations. Whether this is generally true can only be ascertained from empirical studies. Ideally for such a study we should be able to make a prediction concerning the relative strength of selection versus genetic drift. If the latter force is prevalent then the variance-covariances matrices should be proportional to each other. Previous studies have indicated that females in the two sibling cricket species Allonemobius socius and A. fasciatus do not discriminate between males of the two species by their calling song. Therefore, differences between the calling song of the two males most likely result from drift rather than sexual selection. We test this hypothesis by comparing the genetic architecture of calling song of three populations of A. fasciatus with two populations of A. socius. We found no differences among populations within species, but significant differences in the G (genetic) and P (phenotypic) matrices between species, with the matrices being proportional as predicted under the hypothesis of genetic drift. Because of the proportional change in the (co)variances no differences between species are evident in the heritabilities or genetic correlations. Comparison of the two species with a hybrid population from a zone of overlap showed highly significant nonproportional variation in genetic architecture. This variation is consistent with a general mixture of two separate genomes or selection. Qualitative conclusions reached using the phenotypic matrices are the same as those reached using the genetic matrices supporting the hypothesis that the former may be used as surrogate measures of the latter.     

The coadaptation of female morphology and offspring size: a comparative analysis in crickets

Few studies of invertebrates have considered combinations of morphological and life history traits in the context of the evolution of reproductive strategies. Cricket species that exploit habitats harsh with respect to egg survival have evolved a long ovipositor, presumably because laying deep in the soil reduces egg mortality. Yet hatchling mortality increases with laying depth, and the ability of hatchlings to climb through the soil increases with egg size. Thus a conflict may exist between survival of the egg and that of the hatchling, inducing a positive covariation between egg size and ovipositor length across species evolving under contrasting selective habitats. We used the phylogenetic autocorrelation method and a path analysis to assess whether egg size coevolved with ovipositor length across 40 species of crickets, and whether egg size was affected by body size or ecological factors that influence egg mortality. Body size and ovipositor length were affected by taxonomic association, whereas common ancestry had no significant effect on egg size, diapausing strategy, and oviposition preference for soil types. The path model indicated that 29.11% of the variance in egg size was explained by independent evolution. As expected, ovipositor length was positively correlated with egg size, and species diapausing in the egg stage produced larger eggs than crickets diapausing in the nymphal stage or with no diapause. Ovipositor length and diapausing strategy were the first and second most important traits, respectively, in term of the proportion of variance in egg size explained by specific values. These results support the hypothesis that the ability of hatchlings to climb through the soil, and variation in diapause strategies, are general selective factors affecting the evolution of egg size in crickets. Phylogeny explained 51.01% of the variance in egg size. Egg size in a current cricket species, however, was not directly determined by egg size in its ancestor. Instead, it was strongly related to the phylogenetic values of body size and ovipositor length. Such indirect phylogenetic effects of body size and ovipositor length may have arisen because clades originating from ancestors with different ovipositor lengths experienced different selective pressures on egg size. Recelived: 13 October 1995 / Accepted: 30 September 1996     

Reliability of map accuracy assessments: A comment on Hunter et al. (2016)

Map validation data that are ambiguously allocated to map units and collected via poorly designed sampling methods are not statistically reliable and will misrepresent map quality. A recent paper published in Ecological Management and Restoration (Ecological Management & Restoration, 17, 2016 and 40) reported that a map in south‐eastern Australia provided little or no predictive accuracy based on new field data, but the validation suffered from the aforementioned pitfalls. In this comment, we outline the basic guidelines for a robust, reliable and transparent accuracy assessment of thematic maps, pointing out where (Ecological Management & Restoration, 17, 2016 and 40) fails to meets these guidelines.     

The maintenance of phenotypic and genetic variation in threshold traits by frequency-dependent selection

Many traits are phenotypically dimorphic but determined by the action of many loci, the phenotype being a result of a threshold of sensitivity. Quantitative genetic analysis has shown that generally there is considerable additive genetic variation for the trait, the average heritability being 0.52. In numerous cases threshold traits have been shown, or are assumed, to be under frequency-dependent selection; examples include satellite-territorial behaviour, sex-determination, wing dimorphism and trophic dimorphism. In this paper I investigate the potential for frequency-dependent selection to maintain both phenotypic and additive genetic variation in threshold traits. The qualitative results are robust to the particular form of the frequency-dependent selection function. The equilibrium proportion is more or less independent of population size but the heritability increases with population size, typically approaching its maximal value at a population size of 5000, when the mutation rate is 10^?4. A tenfold decrease in the mutation rate requires an approximate doubling of the population size before an asymptotic value is approached. Thus frequency-dependent selection can account for both the existence of two morphs in a population and the observed levels of heritability. It is also shown, both via simulation and theory, that the quantitative genetic model and a simple phenotypic analysis predict the same equilibrium morph proportion.     

Zooplankton growth rates: the larvaceans Appendicularia, Fritillaria and Oikopleura in tropical waters

The growth rates of Appendicularia sicula, Fritillaria borealissargassi, Fritillaria haplostoma, Oikopleura dioica and Oikopleuralongicauda were determined from microcosms incubated in situat 23C in Jamaican waters. Experiments were conducted fromoligotrophic offshore waters, through mesotrophic Lime Cay andeutrophic Kingston Harbour in both natural and nutrient-enhancedphytoplankton communities. Length-weight relationships werecalculated for two of these species: O.longicauda log W=2.47log TL –6.10 and F.haplostoma log W=2.44 log TL –7.37,where weight (W) is in micrograms and trunk length (TL) is inmicrometres. Instantaneous growth rates averaged 1.7–2.5day^–1 for the five species and were observed as high as3.3 day^–1 These instantaneous rates are equivalent todaily specific growth rates averaging 4.6–11.4 and rangingup to 28. In larger genera, growth rates were related positivelyto picoplankton and nanoplankton concentration, and negativelyto the biomass of larvaceans, but in the smallest species growthwas unrelated to these factors. However, because the variabilityin these two factors within microcosms exceeded their naturalrange of variability, growth rates of larvaceans may normallybe unlimited by resources or population density effects. ¹Present address :Monterey Bay Aquarium Research Institute 7700Sandholdt Road, Moss Landing, CA 95039-0628, USA ²Present address :Bedford Institute of Oceanography PO Box 1006,Dartmouth, Nova Scotia B2Y 4A2, Canada