Changes in morphological traits of the cabbage aphid (<Emphasis Type="Italic">Brevicoryne brassicae</Emphasis>) associated with the use of different host plants

The genetic and morphological differentiation of insect populations in relation to the use of different host plants is an important phenomenon that predates ecological specialisation and speciation in sympatric conditions. In this study, we describe the morphological variation of populations of Brevicoryne brassicae (Homoptera: Aphididae) associated with two host species, Brassica oleracea and Brassica campestris, which occur sympatrically in the highlands of Chiapas, Mexico. The study is aimed at obtaining evidence regarding phenotypic differentiation induced by, or associated with, the use of distinct but closely related host species. Seven morphological characters were measured in 696 wingless aphids collected from plants of the two host species at four localities. Morphological variation was summarised through principal components analysis (PCA). Sixty-two percent of morphological variation was explained by the first two PCs. The first component (PC1) was related to the general size of appendages, and PC2 was interpreted as the relationship between body size (body and leg size) and antenna length. Aphids growing on B. campestris were bigger than those collected from B. oleraceae. Significant differences between hosts were detected for PC1, whereas a significant effect of locality, host, and the interaction locality × host was detected for PC2. These results indicate that the average phenotype of B. brassicae individuals inhabiting different host-plant species differs as a consequence of the contrasting feeding environments the host species provide.     

Whistle variation in Mediterranean common bottlenose dolphin: The role of geographical,anthropogenic, social,and behavioral factors

The studies on the variation of acoustic communication in different species have provided insight that genetics, geographic isolation, and adaptation to ecological and social conditions play important roles in the variability of acoustic signals. The dolphin whistles are communication signals that can vary significantly among and within populations. Although it is known that they are influenced by different environmental and social variables, the factors influencing the variation between populations have received scant attention. In the present study, we investigated the factors associated with the acoustic variability in the whistles of common bottlenose dolphin (Tursiops truncatus), inhabiting two Mediterranean areas (Sardinia and Croatia). We explored which factors, among (a) geographical isolation of populations, (b) different environments in terms of noise and boat presence, and (c) social factors (including group size, behavior, and presence of calves), were associated with whistle characteristics. We first applied a principal component analysis to reduce the number of collinear whistle frequency and temporal characteristics and then generalized linear mixed models on the first two principal components. The study revealed that both geographic distance/isolation and local environment are associated with whistle variations between localities. The prominent differences in the acoustic environments between the two areas, which contributed to the acoustic variability in the first principal component (PC1), were found. The calf's presence and foraging and social behavior were also found to be associated with dolphin whistle variation. The second principal component (PC2) was associated only with locality and group size, showing that longer and more complex tonal sound may facilitate individual recognition and cohesion in social groups. Thus, both social and behavioral context influenced significantly the structure of whistles, and they should be considered when investigating acoustic variability among distant dolphin populations to avoid confounding factors.     

Ecogeographic variation of body size in the spectacled salamanders (Salamandrina): influence of genetic structure and local factors

Aim The patterns and causes of ecogeographical body size variation in ectotherms remain controversial. In amphibians, recent genetic studies are leading to the discovery of many cryptic species. We analysed the relationships between body size and climate for a salamander (Salamandrina) that was recently separated into two sibling species, to evaluate how ignoring interspecific and intraspecific genetic structure may affect the conclusions of ecogeographical studies. We also considered the potential effects of factors acting at a local scale. Location Thirty‐four populations covering the whole range of Salamandrina, which is endemic to peninsular Italy. Methods We pooled original data and data from the literature to obtain information on the snout–vent length (SVL) of 3850 Salamandrina females; we obtained high‐resolution climatic data from the sampled localities. We used an information‐theoretic approach to evaluate the roles of climate, genetic features (mitochondrial haplogroup identity) and characteristics of aquatic oviposition sites. We repeated our analyses three times: in the first analysis we ignored genetic data on intraspecific and interspecific variation; in the second one we considered the recently discovered differences between the two sibling species; in the third one we included information on intraspecific genetic structure within Salamandrina perspicillata (for Salamandrina terdigitata the sample size was too small to perform intraspecific analyses). Results If genetic information was ignored, our analysis suggested the existence of a relationship between SVL and climatic variables, with populations of large body size in areas with high precipitation and high thermal range. If species identity was included in the analysis, the role of climatic features was much weaker. When intraspecific genetic differences were also considered, no climatic feature had an effect. In all analyses, local factors were important and explained a large proportion of the variation; populations spawning in still water had a larger body size. Main conclusions An imperfect knowledge of species boundaries, or overlooking the intraspecific genetic variation can strongly affect the results of analyses of body size variation. Furthermore, local factors can be more important than the large‐scale parameters traditionally considered, particularly in species with a small range.     

Variation within isolates ofTyphula incarnata from localities differing in winter climate

Isolates ofTyphula incarnata, a snow mold fungus, were collected from four localities with different winter climates. Their ecological traits such as mycelial growth rate, sclerotium size, carpogenic germination of sclerotia, and aggressiveness were compared between populations in order to reveal infraspecific differentiation associated with climatic differences. Population variability was evident only in sclerotium germination: isolates from more snowy localities germinated faster than those from less snowy localities.T. incarnata is regarded as a versatile pathogen with no specialized forms in contrast withT. ishikariensis. The germination rate of sclerotia is considered very critical in the life history ofT. incarnata.     

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.     

Genetic diversity and ecological relationships of marsh frog populations in Israel

Summary Allozymic variation in proteins encoded by 28 loci was analyzed electrophoretically in 340 mostly adult specimens representing 11 populations, 8 central and 3 isolated, of aquatic marsh frogs, Rana ridibunda in Israel, along a north-south transect of generally increasing aridity. In addition, geographic variation in 3 morphological variables of 144 frogs and in vertebral stripe color polymorphism of 262 frogs were also studied. The results indicate that. (a) Of the 28 loci examined, 12 (= 43%) are largely monomorphic in all populations; out of the remaining loci, 6 were locally and weakly polymorphic and 10 regionally and strongly polymorphic. (b) No fixation of alternative alleles was found in any of the 28 loci and 11 populations studied. The commonest allele predominated across all populations, central as well as isolates, (c) Clinal patterns associated with increasing aridity southwards and eastwards occurred in polymorphism, P; heterozygosity, H; and in allele frequencies of Esterase-1, Xanthine dehydrogenase, Aldehyde oxidase and Albumin. (d) In the 3 estimates of genie variation, mean number of alleles per locus, A, mean proportion of polymorphic loci per population, P, and heterozygous loci per individual, H, marsh frogs displayed average estimates of genetic variation. The 3 estimates were: A =1.14 (range, 1.18–1.57); P = 0.33 (range, 0.14–0.54): H = 0.069 (range, 0.032–0.094). (e) Central populations harbored distinctly more genic variation than isolated populations. (f) Genic similarity between populations was high. (g) Significant deviations from Hardy-Weinberg equilibrium were found in 8 out of 11 populations involving 8 loci, (h) P, H, and allozymic variation in several gene loci were significantly correlated and predictable by environmental variables, primarily those related to water and temperature. (i) A significant amount of morphological variation was found between localities for body length, foot length, and weight in both sexes. Body weight in females was negatively correlated with temperature; and all three morphological variables in females were predicted significantly by a combination of temperature and humidity. (j) The three vertebral stripe color phenotypes, gray, green and red occurred in the following frequencies: 0.59, 0.24, 0.17, respectively. The red morph increased clinally southwards and was significantly correlated with most temperature and water variables. The geographic variation in both the green and red morphs was predicted significantly by climatic variables, both colors blending with local substrates.The spatial patterns and environmental correlates of genetic and morphological variation in Rana ridibunda in Israel suggest that (i) protein polymorphisms are at least partly adaptive and that part is moulded by natural selection rather than by stochastic processes or neutrality; (ii) the environmental variation model seems to be a good predictor of genetic variation in marsh frogs; (iii) body size varies adaptively, presumably determined primarily through thermoregulation; (iv) the spatial pattern of the color polymorphism seems to be adaptively selected by at least two factors: visual predation and climatic determinants.     

Microalgal biotechnology: Carotenoid and glycerol production by the green algae <Emphasis Type="Italic">Dunaliella</Emphasis> isolated from the Gave-Khooni salt marsh,Iran

In this study, carotenoid and glycerol production in two unicellular green algae (Dunaliella salina and D. viridis) isolated from the Gave-Khooni salt marsh grown in media containing five different salt concentrations (0.17, 1, 2, 3, and 4 M NaCl) were evaluated under sterile conditions. Algae growth decreased as the medium salinity increased. Optimum growth of D. salina and D. viridis were obtained at 2 and 1 M NaCl, respectively. As salinity increased, glycerol and carotenoid production were increased in D. salina, whereas lower values for these products were produced in D. viridis under the same conditions. Furthermore, the cell color of D. salina changed from green to orange-red following accumulation of carotenoid, but the color of D. viridis was not changed. Thereby, it seems that the Iranian D. salina may be suitable for carotenoid production (betacarotene) on a large scale. In addition, since carotenoid compounds enhance the efficiency of photosynthesis and glycerol synthesis, it appears that the pathway for glycerol production and mechanisms of salt tolerance in D. viridis are unique from those of D. salina.     

Phenotypic plasticity of life history traits in relation to reproductive strategies in <Emphasis Type="Italic">Boa constrictor occidentalis</Emphasis>

The close connection between reproductive ecology and life history in snakes leads to trade-offs between reproductive and other life-history traits. Optimal energy allocation to growth and reproduction is a key factor to determine life history structure. Therefore, elucidating the relationship between body size variations and reproductive characters is essential for a better understanding of life-history plasticity. The aim of this work was to determine to what extent life-history differs among populations of Boa constrictor occidentalis and to identify possible life-history trade-offs between morphological and reproductive traits. We compared two populations from areas that are separated latitudinally, with different climatic conditions and vegetation landscape structure. Reproductive and morphological data of specimens were recorded. Although populations had a similar mean length of mature snakes, the frequency of some size classes tended to be different. Size at sexual maturity differed between populations for females, generating variations in the proportion of mature individuals. Reproductive threshold and follicular size also varied, but female reproductive frequency was similar between populations. Reproductive frequency of males varied between populations although their body condition was similar. We discussed two major issues: (1) implications of size at sexual maturity for body size and fecundity; (2) trade-offs in reproductive characters.     

Evidence of incipient speciation in the Neotropical mangrove Pelliciera rhizophorae (Tetrameristaceae) as revealed by molecular,morphological, physiological and climatic characteristics

Two variants of the Neotropical mangrove species Pelliciera rhizophorae distributed along both sides of the Isthmus of Panama were detected by different colouration of the floral bracts and the size of the floral and vegetative structures. These findings raised questions concerning a possible speciation event in P. rhizophorae, for which a series of macro‐ and microscopic morphological traits (reproductive and vegetative structures), molecular markers from plastid DNA and climatic profiles were analyzed. Samples of P. rhizophorae were collected in three localities from the Panamanian Caribbean and Pacific coasts. The data obtained from molecular markers and morphological traits showed significant differences between the variants. The climatic profiles showed contrasting characteristics of rainfall and temperature in their habitats: variant A is found in wetter zones and variant B occupies drier zones. Evidence suggesting that a process of incipient speciation has occurred in P. rhizophorae in response to ecogeographical isolation due to climatic factors is presented. The presence of two geographically separate genetic‐morphological groups, adapted to contrasting climatic conditions, will be the basis for suggesting the existence of incipient lineages in Pelliciera. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 499–510.     

Environmentally induced morphological variation in the Barnacle Goose,Branta leucopsis

The environmental conditions to which juvenile barnacle geese (Branta leucopsis) were exposed during growth were found to affect their body size at fledging as well as their final adult body size. Small juveniles showed compensatory growth from the time of fledging up to one year of age, but this did not fully compensate the differences in body size that were established before fledging. The variation in protein content in plants eaten during growth could probably explain the observed body size differences, sometimes of more than 10%, between different categories of adult geese. Our results imply that one cannot infer selection on morphological characters from differences between samples of adult birds from different localities or from different cohorts within a population, without first showing that environmental conditions during growth do not affect the development of the characters under study.     

A genetic perspective on the taxonomy and evolution of the medically important flea,Dinopsyllus ellobius (Siphonaptera: Dinopsyllinae), and the resurrection of Dinopsyllus abaris

Dinopsyllus ellobius is considered a common and widespread flea in southern Africa and can act as a vector for plague. Due to differences in the interpretation of geographical variation in male sternite VIII, the taxonomy of the species is characterized by uncertainty. In an attempt to provide a better understanding of the systematics of D. ellobius, and also to provide new insights into the mechanisms that play a role in the diversification of the taxon, we sampled 830 small mammals at 31 localities throughout the distribution range of the parasite. Mitochondrial cytochrome c oxidase subunit II (COII) sequence data were generated for 151 D. ellobius specimens from 19 positive localities and this data set was supplemented with partial data derived from an elongation factor 1 alpha (EF1‐α) intron. A parsimony haplotype network of the mtDNA and a Splitstree analyses revealed the existence of two genetic clades that were separated by 5.53% (± 1.78) sequence divergence. Although the nuclear DNA data were unresolved, significant size differences were detected between head, coxa, femur and tibia lengths of male individuals belonging to the two mtDNA lineages. The exact mechanisms that could have caused the diversification among lineages are not clear but the two lineages seem to be geographically separated and may have different ecological requirements. The present study strongly supports the notion that the two lineages are representative of D. ellobius (probably more associated with the host body and better adapted to mesic conditions) and Dinopsyllus abaris (probably more associated with the host nest and diverse climatic conditions) as originally proposed based on the single morphological character confined to male sternite VIII.     

Altitudinal variation in the morphometric characteristics of Aedes vexans Meigen from northeastern Turkey

Body size is one of the most significant features of organisms and is correlated with a large number of ecological and physiological variables. Similar to size, biological shape is one of the most conspicuous aspects of an organism's phenotype and provides a link between the genotype and the environment. Body size may change with altitude and also habitat differences associated with altitude may affect the biological shape and some morphological characteristics. Four populations of Aedes vexans Meigen occurring in different ecological subregions at altitudes between 808–1,620 m in the Aras Valley from northeastern Turkey were compared using traditional and geometric morphometrics. When the wing shape differences of populations were analyzed by UPGM, the cluster analyses recognized two main groups of populations. Gödekli (808 m) comprised the first group while Zülfikar (848 m), Sürmeli (944 m), and Cilehane (1,620 m) populations comprised the second group. In the second group, Zülfikar and Cilehane populations showed a similar grouping pattern while Sürmeli appeared as a different group. Centroid sizes were used as measures of overall wing size differences among different regions. Aedes vexans from the Sürmeli region had relatively larger wings.     

Leaf morphological responses to variation in water availability for plants in the <Emphasis Type="Italic">Piriqueta caroliniana</Emphasis> complex

Distribution of plants and the expression of traits associated with environmental variation can be affected by both average conditions and the variance in conditions including extreme climatic events. We expect that these same factors should affect the distribution of plants in hybrid zones between ecologically distinct species where the hybrids should occupy ecotones or intermediate habitats. We evaluated water availability and leaf morphological differences among parental and hybrid populations of herbaceous perennial plants in the Piriqueta caroliniana complex along environmental gradients in Southeastern North America. We focus on two taxa in this group; the viridis morphotype, which occurs in southern Florida, and the caroliniana morphotype, which is distributed from northern Florida to southern Georgia. Advanced-generation hybrid derivatives of these morphotypes occupy a broad geographic region that extends across much of central Florida. Overall, we found that hybrid populations occurred in significantly drier locations, indicating that their habitat requirements are transgressive (i.e., exceeding parental values) rather than intermediate to the parental morphotypes. Water availability differed between the two sampling years, and plants displayed morphological changes in response to these changes in moisture. During the drier year, leaves were narrower and more hirsute, corroborating experimental results that these leaf traits are plastic, and confirming that plasticity occurs in natural habitats. Hybrids exhibited intermediate leaf traits (shape and size) across both years, and displayed transgressive (hair density) leaf traits during the drier year. The apparent canalization of the hybrids’ leaf morphological traits may contribute to their tolerance of variable environmental conditions and may partially explain why they have displaced the caroliniana morphotype in central Florida.     

Early reproduction and increased reproductive allocation in metal-adapted populations of the terrestrial isopod Porcellio scaber

Organisms inhabiting metal-contaminated areas can be stressed by metal exposure and are possibly subject to selection, resulting in increased metal tolerance and changes in growth and/or reproduction characteristics. In a previous study it was found that in the terrestrial isopod Porcellio scaber, sampled from the vicinity of a zine smelter, the body size was small and the brood size was large compared to isopods from a reference area. To assess whether these differences were due to genetic differentiation between strains, isopods collected from a reference wood, a zinc smelter area and a lead mine were cultured on non-polluted food, while growth, reproduction and metal concentrations were studied in first and second laboratory generations. The isopods from the three populations differed in age and weight at first reproduction, although there were hardly any differences in growth. The females of the mine and the smelter population started to reproduce earlier, at a lower weight, which resulted in fewer young per female. However, reproductive allocation (=wight of young relative to the weight of the mother) was higher in mine and smelter isopods. We conclude that the isopods at the metal-contaminated sites have been selected for early reproduction and increased reproductive allocation. The results indicate that populations inhabiting metal-polluted sites have probably undergone evolutionary changes. This study showed that growth and reproduction characteristics of different populations under laboratory conditions may provide information on selection processes in the field.     

Climate change,boundary increase and elongation of a pre‐existing cline: A case study in Drosophila ananassae

During the past two to three decades, Drosophila ananassae, a warm adapted tropical species, has invaded low to mid altitude localities in the western Himalayas. Due to its cold sensitivity, this species had never been recorded from higher latitudes as well as altitudes in India to the 1960s. A latitudinal cline in this desiccation‐sensitive species corresponds with southern humid tropical localities rather than northern drier subtropical localities. An extension of its cline into lowland to midland montane localities has resulted due to global climatic change as well as local thermal effects through anthropogenic impact. However, D. ananassae populations at species borders are characterized by lower genetic variability for body melanization as well as for desiccation resistance. There is a lack of thermal plastic effects for body melanization, and the observed extended cline might represent evolutionary (genetic) response due to selection pressure imposed by drier habitats. A comparison of fecundity, hatchability and viability at three growth temperatures (17, 20 and 25°C) showed significant reduction in trait values at 17°C in D. ananassae. Thus, its recent range expansion into northern montane localities might involve genetic effects on stress‐related traits and plastic effects on life history traits. We suggest that D. ananassae could serve as an indicator species for analyzing range expansion under changing climatic conditions.     

Relationships between environmental gradients and geographic variation in the intraspecific body size of three species of frogs (Anura)

The relationship between environmental gradients and patterns of geographic variation in body size has been a controversial topic for ectothermic organisms globally. To examine whether the patterns that generally hold in more temperate species also hold for tropical ones, we examined the intraspecific body size variation in three species of Neotropical frogs, Dendropsophus minutus, Hypsiboas faber and Physalaemus cuvieri, along different environmental gradients (e.g. temperature, precipitation and topography). We analysed four competing hypotheses: (i) the water availability hypothesis that predicts a negative relationship between body size and precipitation; (ii) the heat balance hypothesis that predicts a negative relationship between body size and temperature; (iii) the topography hypothesis that predicts a negative relationship between body size and altitude; and (iv) the mixed‐effect hypothesis that predicts that individuals occurring in wet and cold sites would be larger than individuals occurring in dry and warm sites. The spatial pattern of geographic variation in body size among populations of H. faber was associated with the mixed‐effect hypothesis. In localities with low precipitation seasonality and cold conditions, H. faber individuals were larger than in localities with high precipitation seasonality and warm conditions. Variation in the body size of D. minutus was the opposite of that predicted by the heat balance hypothesis. Individuals in localities with high temperatures were larger than in localities with low temperatures. On the other hand, variation in the body size of P. cuvieri was not associated with the variables used in this study. Our results suggest that intraspecific variation in anuran body size is more dependent on species‐specific response than on the region (i.e. temperate or tropical) where they occur.     

Greening of the coasts: a review of the Perna viridis success story

The green mussel Perna viridis has been receiving a lot of attention from workers working in the research areas of intertidal ecology, aquaculture, pollution monitoring, biofouling, zoogeography and invasion biology. P. viridis is a remarkable species in terms of its ability to reach very high biomass levels, to withstand environmental fluctuations, to concentrate a variety of organic and inorganic environmental pollutants, to colonise artificial marine habitats and to invade new geographic territories. This review collates data available on salient aspects of the distribution, biology and ecology of P. viridis. It is argued that the remarkable success of P. viridis as an invasive species basically stems from its long larval duration, fast growth rate, high fecundity, early maturity, high productivity and ability to withstand fluctuating environmental conditions (temperature, salinity, water turbidity and pollutants). Relevant aspects of the data are compared with the data available for a similar species Perna perna, which too is an invasive species, but to a more limited extent.     

Examining the phylogeny of the Australasian Lymnaeidae (Heterobranchia: Pulmonata: Gastropoda) using mitochondrial, nuclear and morphological markers

We examined the species groups relationships of the freshwater snail genus Austropeplea using mitochondrial, nuclear and morphological markers in addition to traditional methods of shell shape analysis. Based primarily on the results of a combined molecular and morphological analysis, samples of the nominal species A. tomentosa form distinct lineages. The New Zealand populations of A. tomentosa are a very distinct lineage from any of the Australian populations attributed to A. tomentosa. Furthermore, within the Australian group, three lineages, south Australia, Tasmania and eastern Australia, appear to have undergone recent and/or rapid speciation events. Samples assigned to A. lessoni were resolved as two distinct lineages, representing the eastern and northern Australian populations. Kutikina hispida was resolved within the Australian A. tomentosa clade. Molecular results for A. viridis suggests that it is also composed of at least two distinct lineages that could be treated as species. Incongruence observed between the single mitochondrial, nuclear and morphological topologies highlight the importance of using a number of different datasets in the delimitation of species-group taxa.     

Geographic differentiation among populations ofArabis serrata Fr. & Sav. (Brassicaceae)

Geographic variation in morphological traits of thirteen populations ofArabis serrata was analyzed to characterize the life history of each particular population in the field. These localities varied in altitude, topography, soil type, humidity, vegetation structure and degree of disturbance. Twelve morphological characters were measured in each plant, and populations were compared using both univariate and multivariate analyses. Populations showed significant differences for most of the traits measured. Principal component analyses revealed a significant differentiation among populations although a continuous variation for some traits was noted. Length of capsules and leaf length of inflorescence's stalks were correlated with the number of frost free days and with temperature, precipitation and number of days of the growing season. The number of rosettes was also correlated with the same variables but negatively. Seed weight was correlated positively with altitude but negatively with temperature and length of the growing season. Populations were also differentiated according to soil conditions and disturbance regimes distinguishing different types of populations: I) populations with many small rosettes, and few heavy seeds per capsule in volcanic soils with low disturbance; ii) plants with many small seeds and few rosettes in very disturbed localities along asphalt roadways and mountain trails; and iii) large plants with intermediate seed size and intermediate number of seeds per plant in limestone and serpentine soils under different conditions of disturbance. Populations ofA. serrata displayed a complex pattern of differentiation in morphological and life history traits in relation to several biotic and abiotic factors. The quantitative nature of the differences among populations ofA. serrata observed in the field deserves further studies (e.g., quantitative genetics and phenotypic plasticity) under controlled conditions in order to assess the extent of differentiation within this species complex.     

Environmental influences on the sexual dimorphism in body size of western bobcats

Sexual size dimorphism might be influenced by environmental constraints on sexual selection or by intraspecific competition between males and females. We studied bobcats (Lynx rufus) in collections of museum specimens from western North America to examine these hypotheses. Structural body size was estimated from several measurements of the skull, ln-transformed and indexed through principal components analysis. Sexual dimorphism in body size was estimated from the difference in size index of males and females, and compared to geographic and climatic variables associated with biotic provinces (ecoregions). Of several climatic variables that were associated with bobcat body size, only seasonality of climate was associated with sexual dimorphism. Sexual size dimorphism, longitude, elevation, and seasonality were intercorrelated. As longitude decreased (moving inland from west-coastal ecoregions), sexual dimorphism decreased with the increased elevation and seasonality of continental climates of the Rocky Mountains. We suggest that increased seasonality and the need for fasting endurance by females may place constraints on the degree of sexual dimorphism in bobcats. Sexual dimorphism of body size and sexual size dimorphism of trophic structures (teeth) exhibited a strong positive association over geography, thus indirectly supporting the hypothesis that intrasexual competition for prey could account for the geographic variation in sexual size dimorphism. Thus, both environmental constraints on sexual selection of body size and intersexual competition were supported as possible explanations of the degree of sexual size dimorphism that occurs in populations of bobcats.