PHENOLOGY OF PORPHYRA PENDULA (BANGIALES; RHODOPHYTA) IN THE SOUTHWESTERN GULF OF CALIFORNIA,MEXICO

Porphyra pendula Dawson is an endemic species of the mid‐intertidial zone in the Gulf of California. Based on surveys from the Phycological Herbarium of UABCS since 1994, we found an extensive population of this species in Punta Coyote, south of La Paz. Here, we assess the phenology of the gametophyte phase from December of 1998 to June of 1999 with visits every 2 weeks. Our results show significant temporal and spatial changes in length and width of the plant, with some quadrants displaying two peaks in development ( January and March) and other quadrants with a peak only in January. A significant correlation existed between length and width of the blade and is linked with plant maturation, observations which strongly support the isometric growth rate of the species. No differences between exposed and protected areas were observed suggesting stronger differences between quadrants. Differences plants in length and in color existed between male and female plants; the males were smaller and yellow and females/carposporophyte were larger and red‐purple. Most of the thalli were reproducing during the study, with a greater proportion of females than males (ca. 2:1). Our results suggest that the morphological changes in this species may be related with temperature and day length.     

Lumbar ontogenetic allometry and dimorphism in humans. A case for comparison between interspecific and intraspecific scaling

The ontogenetic allometry of the lumbar region of 1913 humans (1228 females and 685 males), ranging from newborn to 21-year-old individuals, was studied by means of length, width, projected surface area and bone mineral density of the segment L2 - L4, obtained by dual X-ray absorptiometry (DXA). All these parameters were regressed to body mass and height of the individuals, considered alternatively as the independent variable. Firstly, we addressed the comparison between the results obtained on both sexes in order to elucidate whether ontogenetic differences existed. Length of the segments increased significantly faster in females than in males, independently whether the regression was made against body mass or height, while in both types of regression width scaled in males faster than in females. Regarding bone mineral density, although males increased bone mineral density faster than females, slope differences were not significant. However, y-interception was significantly higher in females than in males when bone mineral density was regressed to body mass. Results on length and width are compared with others from previous research on allometry. Finally, global results are discussed as regards the slope predictions for interspecific scaling.     

Sexual size dimorphism and allometric growth of Morelet's crocodiles in captivity

Few studies have conducted morphological analyses of crocodilians, and little information exists on differences between size-classes and sexes in Neotropical crocodilians. In this study, we measured nine morphological traits in 121 captive Morelet's crocodiles Crocodylus moreletii (81 females and 40 males). Our results revealed that individuals < 2 m total length do not exhibit sexual dimorphism in morphometric characteristics. However, for crocodiles over 2 m in length, males were significantly larger than females in terms of dorsal-cranial length, cranial width, snout width and snout-ventral length. In general, morphological traits demonstrated a strongly significant relationship with total length at the smaller size class of 150-200 cm length. However, in the highest size class of 250-300 cm length (large adult males), morphological traits were no longer significantly related with total length. Male crocodiles demonstrated allometric growth of cranial morphology with significantly greater increase in cranial width, snout width, and mid-snout width relative to total length at higher size classes. Morphological dimorphism and allometric growth may be associated with adaptive strategies for reproductive success.     

Dioecy,hermaphrodites and pathogen load in plants

Sex‐specific investment in pathogen resistance and immunity has been widely reported in animals and to a much lesser degree in plants. Here, we investigated the incidence of fungal pathogens in dioecious versus hermaphroditic plant species. We found that direct studies on differences between males and females in disease resistance or pathogen incidence were rare or non‐existent in plants, but if we made the prediction that if such differences exist (e.g. if males are less resistant than females), dioecious species should have a higher variation in pathogen diversity than hermaphrodites. Comparative studies on paired dioecious and hermaphrodite species from multiple plant families showed that hermaphrodites had a higher average pathogen load than dioecious species, consistent with the idea that higher outcrossing is beneficial to resistance to a greater diversity of pathogens. There was however no support for dioecious species also having a greater variance in pathogen diversity. Our results are consistent with dioecy providing a benefit in terms of pathogen resistance, but the data were insufficient to resolve if the male and female plants showed sex‐specific investment in resistance.     

Sex Ratio and Sexual Size Dimorphism in a Toad-headed Lizard,Phrynocephalus guinanensis

Phrynocephalus guinanensis has sexual dimorphism in abdominal coloration, but its ontogenetic development of sexual size dimorphism(SSD) is unknown. Using mark-recapture data during four days each year from August from 2014 to 2016, we investigated the development of sex ratios, SSD, sex-specific survivorship and growth rates in a population of P. guinanensis. Our results indicated that the sex ratio of males to females was 1:2.8. Males had a lower survival rate(6%) than females(14%) across the age range from hatchling to adult, which supported the discovered female-biased sex ratio potentially associated with the low survival rate of males between hatchlings and juveniles. Male-biased SSD in tail length and head width existed in adults rather than in hatchling or juvenile lizards. The growth rates in body dimensions were undistinguishable between the sexes during the age from hatchling to juvenile, but the growth rate in head length from juvenile to adult was significantly larger in males than females. Average growth rate of all morphological measurements from hatchling to juvenile were larger compared with corresponding measurements from juvenile to adult, but only being significant in tail length, head width, abdomen length in females and snout-vent length in males. We provided a case study to strengthen our understanding of the important life history traits on how a viviparous lizard population can survive and develop their morphology in cold climates.     

黄颡鱼的两性异形和雌性繁殖特征

测定了黄颡鱼成体的体长、头长、头宽、头高、吻长、眼径、眼间距、眼后头长、体高、尾柄高、背鳍基前距、背鳍基长、尾柄长、腹鳍基前距、背鳍脂鳍间距、腹鳍臀鳍间距、尾鳍长、体重、去内脏体重等形态指标以及雌体的怀卵数量。雌性成体的体长显著小于雄性成体。其它局部特征皆与体长呈正相关,回归剩余值的t—检验表明,雌性成体的眼径、头高、体高、腹鳍基前距、体重显著大于雄性成体,其它局部形态特征不存在显著的两性差异。黄颡鱼雌体通过个体大小的增加和腹部形态的改变增加腹腔容量,增加繁殖输出。     

Functional traits of grasses growing in open and shaded habitats

The amount of light available for photosynthesis is a key environmental factor that shapes the form and function of plants. Several plant traits affect the manner in which different species fix carbon during vegetative growth. Under the hypothesis that grasses respond to environmental selective pressures, we analyzed the differences in certain leaf, culm, and regenerative traits of 283 native Uruguayan grasses growing in open (grassland) and shaded (forest) habitats. In order to differentiate the phylogenetic effects from the adaptive changes to current local conditions, we used phylogenetically controlled comparative analysis. We found that the divergence of grass species between grasslands and forests was accompanied by changes in leaf traits. Narrow and filiform blades (higher length/width ratio) were favored in species growing in grasslands, while wider and oval blades were favored in species growing in forests. The response of the leaf blades in forests was probably directed towards maximizing light interception, while in grasslands could be linked to the loss of water and heat. In contrast, we found that neither the culm nor the caryopsis length exhibited significant evolutionary changes associated with open or shaded habitats. Our results highlight the functional significance and adaptive value of the width and shape of the grass blades to the current environment.     

The adaptive value of grass traits in response to grazing

Aims Grazing is associated with several plant traits that may confer resistance to herbivores. However, cross-species analyses do not allow for the differentiation between adaptive evolution and common ancestry. In this study, we evaluated the effect of grazing on 5 morphological traits in 41 native grasses growing in natural grasslands of Uruguay and investigated whether such effects are independent of phylogeny.Methods We used data of grass species from 17 paired, grazed and ungrazed plots located in different regions of natural grasslands of Uruguay. For each species, we calculated the Grazing Response Index (GRI) and estimated the culm length, blade length, blade width, blade length/width ratio and caryopsis length. Trait values were calculated as the mean of the maximum and minimum values reported in a public database. We assessed the relationship between the GRI and the morphological traits using cross-species correlations, and we re-examined the correlations using phylogenetically controlled comparative analysis.Important findings Culm length and blade length were significantly correlated with the GRI. Species with higher culms and longer blades diminished their cover under grazing. This association remained significant after statistical control of phylogenetic relatedness among species. By contrast, blade width, blade length/width ratio and caryopsis length did not show any significant relationship with the GRI. Many studies in temperate grasslands recognized that several plant traits respond to grazing but were rarely evaluated in a phylogenetic context. Our results are consistent with the idea that grazing is a selective force with a clear effect on the evolution of grass stature, selecting smaller plants with shorter blades.     

Effects of endophyte fungal species and host plant genotype on the leaf shape and leaf area of endophyte-grass symbionts

Epichloë内生真菌感染能够影响宿主植物的生长发育, 但关于内生真菌感染对宿主植物叶形状和叶面积的研究很少。该研究以羽茅(Achnatherum sibiricum)为实验材料, 采用长宽系数计算和扫描测定叶面积相结合的方法探究内生真菌种类和羽茅母本基因型对羽茅-内生真菌共生体叶形状和叶面积的影响。结果表明: 内生真菌感染与否、内生真菌种类和宿主母本基因型对反映叶形状的叶校正系数、叶片长度、宽度和长宽比均无显著影响, 经计算与验证, 确定了羽茅叶片的校正系数为0.594 9。采用该校正系数及叶长宽计算的叶面积与实测叶面积无显著差异, 且二者均未受到内生真菌感染与否、内生真菌种类或宿主植物母本基因型的显著影响。     

内生真菌种类和母本基因型对内生真菌-禾草共生体叶形状和叶面积的影响

Epichloë内生真菌感染能够影响宿主植物的生长发育, 但关于内生真菌感染对宿主植物叶形状和叶面积的研究很少。该研究以羽茅(Achnatherum sibiricum)为实验材料, 采用长宽系数计算和扫描测定叶面积相结合的方法探究内生真菌种类和羽茅母本基因型对羽茅-内生真菌共生体叶形状和叶面积的影响。结果表明: 内生真菌感染与否、内生真菌种类和宿主母本基因型对反映叶形状的叶校正系数、叶片长度、宽度和长宽比均无显著影响, 经计算与验证, 确定了羽茅叶片的校正系数为0.594 9。采用该校正系数及叶长宽计算的叶面积与实测叶面积无显著差异, 且二者均未受到内生真菌感染与否、内生真菌种类或宿主植物母本基因型的显著影响。     

Sex-specific variation in the interaction between Distichlis spicata (Poaceae) and mycorrhizal fungi

Associations between mycorrhizal fungi and plants can influence intraspecific competition and shape plant population structure. While variation in plant genotypes is known to affect mycorrhizal colonization in crop systems, little is known about how genotypes affect colonization in natural plant populations or how plant sex might influence colonization with mycorrhizal fungi in plant species with dimorphic sexual systems. In this study, we analyzed mycorrhizal colonization in males and females of the wetland dioecious grass Distichlis spicata, which has spatially segregated sexes. Our results suggest that D. spicata males and females interact with mycorrhizal fungi differently. We discuss the implications for the role of this sex-specific symbiotic interaction in the maintenance of the within-population sex ratio bias of D. spicata.     

Endemics and their common congener plant species on an East Mediterranean island: a comparative functional trait approach

Understanding evolution and ecology of endemic plants is of great importance for conservation of those rare and endangered species. Pairwise comparisons of plant functional traits could be an adequate method to get insights in evolutionary and ecological processes. We examined whether morphological traits representing competitive ability and habitat specificity differ between endemics and common plants. Therefore, we performed pairwise comparison analyses of 9 plant functional traits in 36 congeneric pairs of endemics and their common congeners on the East Mediterranean island of Cyprus, i.e., the first such study conducted on a Mediterranean island. We found that endemic species prefer higher elevations and more extreme habitats. Endemics were smaller and they had smaller flowers than their common congeners. Common species had higher chromosome numbers than endemic ones. Endemic and common species showed no significant differences in canopy height, inflorescence height, leaf length and width, and flowering period. Our study showed that the situation on a large oceanic island does not differ from results in mainland research areas.     

INTRAPOPULATIONAL VARIATION IN LEAFLET MORPHOLOGY OF ZAMIA PUMILA L. IN RELATION TO MICROENVIRONMENT AND SEX

The cycad Zamia pumila L. was examined for differences in leaflet morphology between sun and shade plants and between males and females within a single population in northern Puerto Rico. Sun leaflets are significantly smaller than shade leaflets in length, width, and surface area; and sun leaflets have a higher length: width ratio than shade leaflets. Also, average densitythickness is greater for sun leaflets than for shade leaflets. Males and females are similar in leaflet size; but the females had a larger number of leaflets per leaf than males.     

Sexual dimorphism inSebastes

Synopsis Sexual dimorphism and factors that may cause it were investigated in 34 species of the genusSebastes. Sexual dimorphism in standard length and morphometric characters are fairly common in rockfish. In many species males are shorter than females. However in males head length, width of orbit, interorbital width, length of upper jaw, longest pectoral fin ray and longest dorsal spine tend to be larger at a specified size than in females. Water-column species tend to be more dimorphic than demersal species. We suggest that the observed differences in dimorphism in standard length may be related to differences in mating and territorial behavior. Dimorphisms in morphometric measurements may be related to compensation in feeding ability for reduced standard length of males, mating and territorial behavior.     

Function‐related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent,Plateau Zokor (Eospalax baileyi)

Sexual dimorphism is prevalent in most living organisms. The difference in size between sexes of a given species is generally known as sexual size dimorphism (SSD). The magnitude of the SSD is determined by Rensch's rule where size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. The unique underground environment that zokors (Eospalax baileyi) live under in the severe habitat of the Qinghai‐Tibetan Plateau (QTP) could create SSD selection pressures that may or may not be supported by Rensch's rule, making this scientific question worthy of investigation. In this study, we investigated the individual variation between sexes in body size and SSD of plateau zokors using measurements of 19 morphological traits. We also investigated the evolutionary mechanisms underlying SSD in plateau zokors. Moreover, we applied Rensch's rule to all extant zokor species. Our results showed male‐biased SSD in plateau zokors: The body‐ and head‐related measurements were greater in males than in females. Linear regression analysis between body length, body weight, and carcass weight showed significant relationships with some traits such as skull length, lower incisor length, and tympanic bulla width, which might support our prediction that males have faster growth rates than females. Further, the SSD pattern corroborated the assumption of Rensch's rule in plateau zokors but not in the other zokor species. Our findings suggest that the natural underground habitat and behavioral differences between sexes can generate selection pressures on male traits and contribute to the evolution of SSD in plateau zokors.     

Sexual and male horn dimorphism in Copris ochus (Coleoptera: Scarabaeidae)

Copris ochus (Coleoptera: Scarabaeidae), an endangered species, is the largest dung beetle in Japan. In C. ochus, males have a long head horn, while females lack this long horn (sexual dimorphism). Very large males of C. ochus have disproportionately longer head horns than small males, suggesting male horn dimorphism, although the dimorphism has not been investigated quantitatively. To clarify sexual and male horn dimorphism in C. ochus quantitatively, we examined the scaling relationship between body size (prothorax width) and head horn length in 94 females and 76 males. These beetles were captured during July 1978 from a natural population on Mt. Aso in southwestern Japan using a light trap. Although the horn length of the females and males scaled with prothorax width, the scaling relationship differed between the sexes, i.e., the relationship was linear in females and nonlinear in males. Statistical tests for dimorphism in male horn length showed a significant discontinuous relationship, thus indicating distinct sexual and male dimorphism in head horns. Long- and short-horned C. ochus males may have different reproductive behaviors, as described in other horned dung beetles.     

草原蜥两性的咬合力及头部形态特征比较

咬合力作为衡量动物生存能力的重要指标,可以在一定程度上反映动物捕食、反捕食和争夺配偶的能力。对于蜥蜴类动物而言,头部形态和咬合力大小之间常呈现显著线性关系。通过测量2018年7月采集于新疆霍城县图开沙漠的24号草原蜥(Trapelussanguinolenta)(雌13,雄11)的头部形态指标,并使用薄膜压力测试仪测定咬合力,采用单因素方差分析(ANOVA)、主成分分析、模型拟合及逐步回归4种方法探究草原蜥咬合力的两性差异及其与头部形态指标的关系。结果表明,草原蜥头体长、头长、头宽、头高、口宽和下颌长在两性个体间均无显著差异,草原蜥两性个体之间咬合力也没有显著差异。主成分分析及赤池信息模型拟合结果均显示,头长、头宽和下颌长是影响草原蜥咬合力的重要因素,逐步回归分析揭示草原蜥的咬合力主要受头宽影响。上述研究结果表明,草原蜥的咬合力受头部形态大小的影响,但两性个体之间咬合力却不存在显著差异,这与头部形态特征未表现出两性差异一致,这可能是草原蜥对灌丛生活的适应,具体而言,是头部大小与运动权衡的结果。     

The impact of Bt maize as a natal host on adult head capsule width in field populations of western corn rootworm

The success of the current resistance management plan for transgenic maize, Zea mays L. (Poaceae), targeting the rootworm complex hinges upon high rates of mating between resistant and susceptible beetles. However, differences in the fitness of adult beetles could result in assortative mating, which could, in turn, change the rate of resistance evolution. Adult head capsule widths of naturally occurring populations of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), were examined in a variety of refuge configurations. Beetles were classified into treatments based on the hybrid – non‐Bt refuge or Bt maize targeting larval rootworms (hereafter Bt‐RW maize) – and location – proximity to other Bt‐RW or refuge plants – of the natal host plant. Treatments included the following: a refuge plant surrounded by other refuge plants, a refuge plant located near a Bt‐RW plant, a Bt‐RW plant surrounded by Bt‐RW plants, and a Bt‐RW plant located near a refuge plant. The mean head capsule width of males emerging from Bt‐RW plants was significantly smaller than the mean head capsule width of males emerging from refuge plants. These results indicate that males emerging from Bt‐RW maize plants may be exposed to sublethal doses of the Bt toxin as larvae. No differences were detected between females emerging from refuge plants compared with Bt‐RW plants. Overall mean head capsule width decreased as the season progressed, regardless of treatment. The diminished head capsule width of western corn rootworm males emerging from Bt‐RW maize may act to enhance resistance management, particularly in a seed mix refuge system.     

Allometric variation among juvenile, adult male and female eastern bearded dragons Pogona barbata (Cuvier, 1829), with comments on the behavioural implications

The functional significance of allometric change in reptiles has received limited attention and the reason for such changes has been regarded as ‘obscure’. In this paper we report data on the Australian Pogona barbata, the eastern bearded dragon, from across their range and review changes in allometric growth among juveniles, and adult males and females and consider the functional relevance of these changes. There were significant differences in the population for mass, tail length, tail width, rear leg length and jaw length. These differences were consistent with differences required in locomotor performance and thus habitat use, together with access to different preferred dietary components.