Testing for heterogeneity among phenotypic correlations: a comparison of methods using Monte Carlo simulations

Heterogeneous phenotypic correlations may be suggestive of underlying changes in genetic covariance among life-history, morphology, and behavioural traits, and their detection is therefore relevant to many biological studies. Two new statistical tests are proposed and their performances compared with existing methods. Of all tests considered, the existing approximate test of homogeneity of product-moment correlations provides the greatest power to detect heterogeneous correlations, when based on Hotelling's z*-transformation. The use of this transformation and test is recommended under conditions of bivariate normality. A new distribution-free randomisation test of homogeneity of Spearman's rank correlations is described and recommended for use when the bivariate samples are taken from populations with non-normal or unknown distributions. An alternative randomisation test of homogeneity of product-moment correlations is shown to be a useful compromise between the approximate tests and the randomisation tests on Spearman's rank correlations: it is not as sensitive to departures from normality as the approximate tests, but has greater power than the rank correlation test. An example is provided that shows how choice of test will have a considerable influence on the conclusions of a particular study. This revised version was published online in July 2006 with corrections to the Cover Date.     

Does whole‐organism performance constrain resource use? A community test with desert lizards

Discovering the mechanisms by which communities of co‐existing species exist has proven to be one of the greatest challenges for evolutionary ecologists. A recent perspective emphasizes the role of functional traits, such as whole‐organism performance, as key limiting factors in the evolution of communities, yet few studies have examined this possibility. We examine how bite force and morphology influence the ability of ten lizard species in a single community to access insect prey, as defined by prey type and prey hardness. We gathered over 3 years of data from a desert lizard community comprised of ten species and found significant variation among species for bite force and prey hardness, as well as significant differences in performance and niche breadth for each species. In general, higher levels of absolute bite force broadens resource accessibility (sizes of prey), and does not generally result in a reduced ability to access smaller prey. For example, large lizard species that are hard biters can still consume soft prey. On the other hand, small lizard species that are weak biters are more limited in their ability to access hard prey, although the overall decline in resource accessibility is modest. Our findings highlight how functional traits can influence which species can access key resources within a community of similar species. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.     

Genetic variation and climatic selection in the lizard Agama stellio in Israel and Sinai

Summary Allozymic variation in proteins encoded by 25 loci was analyzed electrophoretically in 242 adult specimens representing nine populations of the Levantine lizard, Agama stellio, comprising two subspecies: the Mediterranean A. stellio subsp., and the desert-inhabiting A. stellio brachydactyla from the Negev and Sinai. Likewise, four body traits were measured in the same populations. The nine populations were sampled along a general southward transect of increasing aridity. Agama stellio is above average in both polymorphism, P, and heterozygosity, H, as compared to other reptiles and vertebrates in general, displaying levels of genetic variation characterizing habitat generalist vertebrates. In the populations studied no fixation of alternative alleles was found in any of the 25 loci: rather the commonest allele was either fixed or predominated in 23 of 25 loci examined. Eleven loci (44%) were monomorphic in all nine populations. However, of the remaining 14 polymorphic loci, eight were strongly polymorphic displaying distinct genetic differentiation between populations. Genetic diversity (indexed by P and H) displayed geographic variation and was slightly higher in A.s. brachydactyla than in A. stellio subsp. Nevertheless, genic similarity between populations was high. A statistically significant amount of morphological variation between localities was found for all body characters. In general, body size increased southwards and eastwards with aridity.Selection at some loci is suggested by significant deviation from Hardy-Weinberg expectations and possibly by excess heterogeneity of effective inbreeding coefficients, F_e. Furthermore, allozymic variation at seven loci (Ldh-1, Idh-1, 6-Pgd-1, Aat-1, Pgm-2, Pept-1, and Trf) and geographic variation in body size and weight were significantly correlated with, and predictable by, climatic variables, primarily by water availability and secondarily by temperature. Finally, allozymic and morphological variations were partly correlated.The spatial patterns and ecological correlates of genic and morphological variations in Agama stellio in Israel and Sinai suggest that at least some proteins and body size differentiate geographically and appear to be adaptive, presumably with respect to factors affecting the availability of water.     

Population structure and skeletal variation in the Late Woodland of west-central Illinois

This paper analyzes nonmetric trait variation in 11 late Late Woodland (ca. AD 700-1000) and one Mississippian (AD 1000-1300) skeletal samples from west-central Illinois from a population-structure perspective. Most of the sites are of the Bluff phase of Late Woodland in the lower Illinois River valley; others are from a nearby, contemporary archaeological phase. Late Woodland as a whole era (ca. AD 250-1000) was a period of marked population growth and expansion into new regional environments, trends that accompanied horticultural intensification in the area. Overall variation between sites was low, but males, females, and the total sample exhibited a significant geographic component to variation due to interregional morphological differences. The Bluff sites tended to group together relative to the non-Bluff sites. However, there was no significant geographic component to variation among the Bluff sites. The results are only partially consistent with archaeological data suggesting population growth and expansion through fissioning. Previous studies have demonstrated significant heterogeneity for nonmetric trait frequencies among Middle Woodland (ca. 100 BC to AD 250) sites, suggesting a Middle to Late Woodland change in population structure that lowered levels of morphological variation. This supports a model of increased intra- and interregional interaction from Middle to Late Woodland times developed from ceramic data by Braun and by Braun and Plog.     

Behavioral attributes influence annual mating success more than morphological traits in male collared lizards

Traits that potentially influence mating success (MS) may be"static" with low lability once they develop or "dynamic" withhighly modifiable expression. We used principal components (PCs)analyses of dynamic behavioral and morphological traits thatare static over the short term to determine their relative contributionsto the ability of territorial male collared lizards to acquireaccess to females and obtain high MS. We estimated annual MSof males as the relative frequency with which they engaged incourtship with reproductively active resident females. ThreePCs explained statistically significant phenotypic variationamong males. Morphological traits loaded significantly on 2PCs that explained 26.3% and 13.0% of the variance, respectively,whereas behavioral variables loaded significantly on a differentcomponent that explained 15.7% of the variance in male traits.The frequency with which males initiated aggressive encounterswith same-sex competitors did not load significantly on thesePC axes. Males having behavioral PC scores above the mean hadsignificantly higher MS than those with behavioral scores belowthe mean, whereas male MS was not related to component scoresfor either of the axes describing static morphological variables.Results indicate that in our population behavior patterns associatedwith advertisement, particularly to females, influence maleMS more strongly than morphological traits or the initiationof direct aggression with same-sex competitors.     

Heterochrony: The evolution of ontogeny. By Michael L. McKinney and Kenneth J. McNamara. New York: Plenum Press. 1991. XIX + 437 pp. ISBN 0-306-43638-8. $ 49.50 (cloth)

Macaca fascicularis is broadly distributed in Southeast Asia across 30° of latitude and 35° of longitude (Indochinese Peninsula, Isthmus of Kra, Malay Peninsula, Greater and Lesser Sunda Islands, Philippine Islands, and numerous small, neighboring islands). The range is divisible into 1) a core area comprised of mainland Southeast Asia, Borneo, Sumatra, and Java (large land masses interconnected during the last glacial maximum, 18,000 B. P.); 2) shallow-water fringing islands, which are smaller islands connected to the core area during the last glacial maximum; and 3) deep-water fringing islands, which are peripheral islands not connected to the core area during the last glacial maximum. Skull length was used to study effects of latitude and insularity on patterns of size variation. The data are from 802 adult M. fascicularis specimens from 140 core-area localities, 63 shallow-water islands, and 29 deep-water islands. Sex-specific polynomial regressions of skull length on latitude were used to describe skull length variation in the core area. These regressions served as standards for evaluating variation among samples from shallow-water and deep-water islands. The core area exhibits Bergmannian latitudinal size clines through most of the species range. Thus, skull length decreases from about 8°S (Java) to the equator (Sumatra and Borneo), then increases as far north as about 13°N (Isthmus of Kra). Farther north, to the northernmost Indochinese localities at about 17°N, skull length in M. fascicularis decreases with increasing latitude, contrary to Bergmann's rule. Latitudinal size variation in shallow-water fringing islands generally parallels that in the core area. However, skull length tends to be smaller than in the core area at similar latitudes. Deep-water fringing islands are markedly more variable, with relatively small specimens in the Lesser Sunda Islands and relatively large specimens in the Nicobar Islands. These analyses illustrate how a primate species may vary in response to latitudinal temperature variation and to isolation. © 1993 Wiley-Liss, Inc.     

Does foraging mode mould morphology in lacertid lizards?

Evolutionary changes in foraging style are often believed to require concurrent changes in a complex suite of morphological, physiological, behavioural and life-history traits. In lizards, species from families with a predominantly sit-and-wait foraging style tend to be more stocky and robust, with larger heads and mouths than species belonging to actively foraging families. Here, we test whether morphology and foraging behaviour show similar patterns of association within the family Lacertidae. We also examine the association of bite force abilities with morphology and foraging behaviour. Lacertid lizards exhibit considerable interspecific variation in foraging indices, and we found some evidence for a covariation between foraging style and body shape. However, the observed relationships are not always in line with the predictions. Also, the significance of the relationships varies with the evolutionary model used. Our results challenge the idea that foraging style is evolutionarily conservative and invariably associated with particular morphologies. It appears that the flexibility of foraging mode and its morphological correlates varies among lizard taxa.     

Geographic variation in nut size of<Emphasis Type="Italic"> Castanopsis</Emphasis> species in Japan

The environmental conditions affecting the geographic variation in nut size of the Castanopsis species in Japan were examined. The mother trees having a relatively large nut tended to dominate in the geographically marginal area of the distribution range in Japan, i.e. the Japan Sea, Kanto, and Ryukyu areas, whereas in the central area, i.e. the Pacific area, mother trees having a relatively small nut occurred. We attempted an adaptive explanation, proposing that mother trees with large nuts have higher inclusive fitness than those with small nuts in unfavorable habitats. The Japan Sea area features large amounts of snow fall and low temperatures. The Ryukyu area is insular and is characterized by high temperatures. Within the Pacific area, mother trees with relatively large nuts were abundant at both higher and lower parts of the altitudinal range. We infer that environmental conditions in marginal areas, in terms of both horizontal and vertical distribution, favor mother trees having large nuts. However, in the marginal Kanto area, the cause of the absence of mother trees having relatively small nuts was independent of the environmental conditions. The geographic variation in nut size of Castanopsis species is not always explained by environmental factors.     

中国生态学学会干旱半干旱区生态学学术讨论会

中国生态学学会于1982年10月6日至11日在新疆乌鲁木齐市召开了干旱、半干旱区生态学学术讨论会。参加这次学术讨论会的有来自西北五省区以及内蒙古、山西、河北、北京、沈阳、上海、南京、云南等十三个省(区)市的69个单位的85名代表,包括动物生态、植物生态、农、林、牧、水利、气候、环保等专业。中国生态学学会理事长马世骏、南京大学生物系教授仲崇信、中国科学院西北高原生物研究所所长夏武平等著名生态学家以及中国科协学会部副部长王定华同志     

Ecotypic differentiation in the grasshopper Chorthippus brunneus: life history varies in relation to climate

Life history variations among 27 populations of the grasshopper Chorthippus brunneus from around the British Isles were examined under laboratory conditions over three generations. Multiple-regression analysis was used to examine the relationship between grasshopper life histories and the climates of their ancestral sites. Grasshoppers from cooler sites were heavier at hatching. Grasshoppers from northern sites grew faster and developed through fewer instars, attaining adulthood earlier, at the expense of adult size. Depending on the measure of adult size used, adults were larger in warmer, sunnier or more southerly locations. Ecotypic differentiation is probably widespread among animals as it is among plants, though it is more rarely demonstrated by zoological studies, especially over the wide geographical scale covered here. Evidence from regression analysis supports the hypothesis that ecotypic differentiation in C. brunneus is an evolutionary response to climatic variation. The existence of intraspecific genetic diversity for climatic adaptations has implications for biodiversity conservation and the understanding of biotic responses to climatic change. It deserves wider recognition. Received: 5 October 1998 / Accepted: 30 June 1999     

The effect of variable environments on polymorphism at loci with several alleles II. Submultiplicative viabilities

Circumstances assuring a unique stable equilibrium are investigated for a subdivided population with several alleles segregating at a single locus. For a broad class of selection regimes entailing heterozygote viabilities greater than the geometric mean of the corresponding homozygote viabilities, a stable fixation state precludes any other stable equilibria if either total-panmixia or temporal variation is operating. This extends known results for two alleles at a single locus and partially delimits when some of the bizarre behaviour engendered by multiple alleles may occur.Supported in part by National Science Foundation (USA) grant MCS-8002227