Ecological and phylogenetic constraints on body size in Indo-Pacific fishes

Synopsis Regional Indo-Pacific fish faunas were examined for broad patterns in species size composition. An analysis of the New Guinea fauna, based on data compiled by Munro (1967), revealed that (i) maximum body size for a species tended to be larger in the more advanced teleost families; (ii) intrafamilial size variation (expressed by the standard deviation of log-transformed maximum body size) was significantly lower in the suborder Percoidei than in families drawn from broader taxonomic groupings; and (iii) size variation was significantly positively correlated with mean maximum body size and, in the percoids only, with the number of species in a family. An analysis of Marshall Islands reef fish assemblages, based mainly on the data of Matt & Strasburg (1960), indicated, that (i) mean maximum body size varied significantly between habitats and feeding categories, and tended to increase with openness of habitat and with trophic level; (ii) size variation within feeding categories increased with the number of species, but not significantly so; and (iii) confamilial species generally exhibited close similarities in terms of preferred habitats, trophic levels and foraging modes. These findings indicate that interspecific body size variation is both phylogenetically and ecologically constrained. Size variation within ecological categories (especially habitats) was much greater than within families. Thus, confamilial species generally did not exhibit the range of body sizes theoretically open to members of their habitat feeding guilds. The results are also consistent with aspects of resource-partitioning theory, notably that resource-utilisation breadth should increase with the number of coexisting species.     

A comparative analysis of adult body size and its correlates in acanthocephalan parasites

Adult acanthocephalan body sizes vary interspecifically over more than two orders of magnitude; yet, despite its importance for our understanding of the coevolutionary links between hosts and parasites, this variation remains unexplained. Here, we used a comparative analysis to investigate how final adult sizes and relative increments in size following establishment in the definitive host are influenced by three potential determinants of acanthocephalan sizes: initial (cystacanth) size at infection, host body mass, and the thermal regime experienced during growth, i.e. whether the definitive host is an ectotherm or an endotherm. Relative growth from the cystacanth stage to the adult stage ranged from twofold to more than 10,000-fold across acanthocephalan species, averaging just over 100-fold. However, this relative increment in size did not correlate with host mass, and did not differ between acanthocephalan species using ectothermic hosts and those growing in endothermic hosts. In contrast, final acanthocephalan adult sizes correlated positively with host mass, and after correction for host mass, final adult sizes were higher in species parasitising endotherms than in those found in ectotherms. The relationship between host mass and acanthocephalan adult size practically disappears, however, once phylogenetic influences are taken into account. Positive relationships between adult acanthocephalan size, cystacanth size and egg size indicate that a given relative size is a feature of an acanthocephalan species at all stages of its life cycle. These relationships also suggest that adult size is to some extent determined by cystacanth size, and that the characteristics of the definitive host are not the sole determinants of parasite life history traits.     

Basic concepts relevant to heat transfer in fishes,and their use in measuring the physiological thermoregulatory abilities of tunas

Synopsis Aerobic heat production and heat loss via the gills are inexorably linked in all water breathing teleosts except tunas. These processes are decoupled in tunas by the presence of vascular counter-current heat exchangers, and sustained (i.e., steady state) muscle temperatures may exceed water temperature by 10° C or more in larger individuals. The presence of vascular counter-current heat exchangers is not clearly advantageous in all situations, however. Mathematical models predict that tunas could overheat during strenuous activity unless the efficacy of vascular heat exchangers can be reduced, and that they may be activity limited in warmer waters. Tunas may likewise be forced out of potentially usable habitats as they grow because they have to occupy cooler waters. Vascular counter-current heat exchangers also slow rates of heating and cooling. A reduced rate of muscle temperature decrease is clearly advantageous when diving into colder water to chase prey or avoid predators. A reduced rate of heat gain from the environment would be disadvantageous, however, when fish return to the warmer surface waters. When subjected to changes in ambient temperature, tunas cannot defend a specific body temperature and do not thermoregulate in the mammalian sense. Yet when appropriately analyzed, data taken under steady state and non-steady state conditions indicate that tunas are not strictly prisoners of their own thermoconserving mechanisms. They apparently can modify overall efficiency of their vascular counter-current heat exchangers and thus avoid overheating during bouts of strenuous activity, retard cooling after diving into colder water, and rapidly warm their muscles after voluntarily entering warmer water. The exact physiological mechanisms employed remain to be elucidated.Paper from the International Union of Biological Societies symposium The biology of tunas and billfishes: an examination of life on the knife edge, organized by Richard W. Brill and Kim N. Holland.     

Explaining marriage patterns in a globally representative sample through socio-ecology and population history: A Bayesian phylogenetic analysis using a new supertree

Comparative analyses have sought to explain variation in human marriage patterns, often using predictions derived from sexual selection theory. However, most previous studies have not controlled for non-independence of populations due to shared ancestry. Here we leverage a phylogenetic supertree of human populations that includes all 186 populations in the Standard Cross-Cultural Sample (SCCS), a globally representative and widely-used sample of human populations. This represents the most comprehensive human phylogeny to date, and allows us not only to control for non-independence, but also to quantify the role of population history in explaining behavioral variation, in addition to current socio-ecological conditions. We use multiple imputation to overcome missing data problems and build a comprehensive Bayesian phylogenetic model of marriage patterns with two correlated response variables and eleven minimally collinear predictors capturing various socio-ecological conditions. We show that ignoring phylogeny could lead to both false positives and false negatives, and that the phylogeny explained about twice as much variance as all the predictors combined. Pathogen stress and assault frequency emerged as the predictors most strongly associated with polygyny, which had been considered evidence for female choice of good genes and male intra-sexual competition or male coercion, respectively. Mixed support was found for a polygyny threshold based on variance in male wealth, which is discussed in light of recent theory. Barring caveats, these findings refine our understanding of the evolution of human marriage systems, and highlight the value of combining population history and current socio-ecology in explaining human behavioral variation. Future studies using the SCCS should do so using the present supertree.     

Within-species differences in primate social structure: evolution of plasticity and phylogenetic constraints

Primate socioecological studies have attempted to derive general frameworks using the average behavioural traits of species or genera to place them into categories. However, with the accumulation of primate studies, it is timely to place more emphasis on understanding within-species variation in social structure. In this review we have four objectives. First, we examine within-species variation in the potential determinants of social structure, including diet, demography, predation and infanticide, and document considerable variation. Second, we present case studies of within-species variation in social structure to illustrate the potential magnitude of this variation. For example, there are cases within a single interbreeding population where multi-male, uni-male, fission–fusion and monogamous groups are found. Third, by examining widespread primate lineages that occur in a variety of habitats, we note that there are differences in the magnitude of variation in social structures across different lineages and as a result we consider phylogenetic constraints on phenotypic variation in social structure. Finally, we reflect on the implications of extensive variation in social structure. We suggest that primate social structure will represent a combination of adaptation to present-day environment and phylogenetic inertia. To advance our understanding of the relative contribution of phylogeny versus ecology we propose two approaches. One approach is to compare groups in the same interbreeding population that inhabit different ecological conditions. Any differences that are found can be attributed to ecological differences, since phylogeny should not play a role within a single population. The second approach is to study distantly related species that have similar social structures to illustrate how similar ecological pressures might be operating to select for parallel social structures.     

Unique adaptations of the metabolic biochemistry of tunas and billfishes for life in the pelagic environment

Synopsis Virtually all characteristics of tunas and billfishes reflect their highly charged lifestyles as apex predators in the oceanic pelagic environment. The adaptations they possess for efficient and rapid swimming, efficient and rapid food processing, turnover of nutrients and storage and mobilization of internal fuel supplies, and for rapid recovery rates, are discussed. Overall, tunas and billfishes are designed for high performance, at both sustainable and burst swimming speeds, but there are several differences between tunas and billfishes. Tunas' aerobic metabolic capacities exceed those of ectothermic fishes, including billfishes and other scombrids, by virtue of their elevated red muscle temperatures, and because heart and white muscle aerobic capacities are significantly greater in tunas. The adaptations for high performance involve some costs, including the need for a constant high energy input to sustain high metabolic rates, high activity levels, and endothermy, Yet, tunas and billfishes have adopted successful lifestyles, as evidenced by their large numbers and biomass within the marine environment. Although our knowledge of these fishes has increased dramatically during the past 15 years, there are major gaps in our understanding of the metabolic biochemistry and physiology of these fishes, and these are highlighted so that additional research can be directed towards filling these gaps.Paper from the International Union of Biological Societies symposium The biology of tunas and billfishes: an examination of life on the knife edge, organized by Richard W. Brill and Kim N. Holland.     

葱属Amerallium亚属 (石蒜科) 的系统发生与性状进化

运用贝叶斯和简约法对葱属（Allium）Amerallium亚属的核糖体DNA内转录间隔区（ITS）进行了分析,对该亚属的系统发生进行了推测。系统分析证实 Amerallium是单系的,并表明该亚属由三个隔离的地理群组成：北美Ameralliums,地中海区Ameralliums和东亚Ameralliums。性状进化的重建表明鳞茎是原始或祖先状态,根状茎和肉质增粗的根是衍生状态且在Amerallium这个亚属的类群中独立进化发生了几次。重建也表明该亚属的原始染色体基数x=7,其它染色体基数（x=8, 9, 10, 11）是由它转化而来的。在北美类群中,异基数性相当罕见,而多倍性似乎是一个相对频繁的进化事件。在地中海区类群和东亚类群中,异基数性和多倍性是染色体进化的两个主要驱动力。     

Anatomical diversity and regressive evolution in trichomanoid filmy ferns (Hymenophyllaceae): a phylogenetic approach

To infer the anatomical evolution of the Hymenophyllaceae (filmy ferns) and to test previously suggested scenarios of regressive evolution, we performed an exhaustive investigation of stem anatomy in the most variable lineage of the family, the trichomanoids, using a representative sampling of 50 species. The evolution of qualitative and quantitative anatomical characters and possibly related growth-forms was analyzed using a maximum likelihood approach. Potential correlations between selected characters were then statistically tested using a phylogenetic comparative method. Our investigations support the anatomical homogeneity of this family at the generic and sub-generic levels. Reduced and sub-collateral/collateral steles likely derived from an ancestral massive protostele, and sub-collateral/collateral types appear to be related to stem thickness reduction and root apparatus regression. These results corroborate the hypothesis of regressive evolution in the lineage, in terms of morphology as well as anatomy. In addition, a heterogeneous cortex, which is derived in the lineage, appears to be related to a colonial strategy and likely to a climbing phenotype. The evolutionary hypotheses proposed in this study lay the ground for further evolutionary analyses that take into account trichomanoid habitats and accurate ecological preferences.     

The role of character loss in phylogenetic reconstruction as exemplified for the Annelida

Annelid relationships are controversial, and molecular and morphological analyses provide incongruent estimates. Character loss is identified as a major confounding factor for phylogenetic analyses based on morphological data. A direct approach and an indirect approach for the identification of character loss are discussed. Character loss can frequently be found within annelids and examples of the loss of typical annelid characters, like chaetae, nuchal organs, coelomic cavities and other features, are given. A loss of segmentation is suggested for Sipuncula and Echiura; both are supported as annelid ingroups in molecular phylogenetic analyses. Moreover, character loss can be caused by some modes of heterochronic evolution (paedomorphosis) and, as shown for orbiniid and arenicolid polychaetes, paedomorphic taxa might be misplaced in phylogenies derived from morphology. Different approaches for dealing with character loss in cladistic analyses are discussed. Application of asymmetrical character state transformation costs or usage of a dynamic homology framework represents promising approaches. Identifying character loss prior to a phylogenetic analysis will help to refine morphological data matrices and improve phylogenetic analyses of annelid relationships.     

Evolution of genome size in fishes: a phylogenetic test of the Hinegardner and Rosen hypothesis

Despite remarkable advances in genomic studies over the past few decades, surprisingly little is known about the processes governing genome evolution at macroevolutionary timescales. In a seminal paper, Hinegardner and Rosen (Am Nat 106:621–644, 1972) suggested that taxa characterized by larger genomes should also display disproportionately stronger fluctuations in genome size. Therefore, according to the Hinegardner and Rosen (HR) hypothesis, there should be a negative correlation between average within-family genome size and its corresponding coefficient of variation (CV), a prediction that was supported by their analysis of the genomes of 275 species of fish. In this study we reevaluate the HR hypothesis using an expanded dataset (2050 genome size records). Moreover, in addition to the use of standard linear regression techniques, we also conducted modern comparative analyses that take into account phylogenetic non-independence. Our analyses failed to confirm the negative relationship detected in the original study, suggesting that the evolution of genome size in fishes might be more complex than envisioned by the HR hypothesis. Interestingly, the frequency distribution of fish genome sizes was strongly skewed, even on a logarithmic scale, suggesting that the dynamics underlying genome size evolution are driven by multiplicative phenomena, which might include chromosomal rearrangements and the expansion of transposable elements.     

The evolution of a complex trait: cuticular hydrocarbons in ants evolve independent from phylogenetic constraints

Cuticular hydrocarbons (CHCs) are ubiquitous and highly diverse in insects, serving as communication signal and waterproofing agent. Despite their vital function, the causes, mechanisms and constraints on CHC diversification are still poorly understood. Here, we investigated phylogenetic constraints on the evolution of CHC profiles, using a global data set of the species‐rich and chemically diverse ant genus Crematogaster. We decomposed CHC profiles into quantitative (relative abundances, chain length) and qualitative traits (presence/absence of CHC classes). A species‐level phylogeny was estimated using newly generated and previously published sequences from five nuclear markers. Moreover, we reconstructed a phylogeny for the chemically diverse Crematogaster levior species group using cytochrome oxidase I. Phylogenetic signal was measured for these traits on genus and clade level and within the chemically diverse C. levior group. For most quantitative CHC traits, phylogenetic signal was low and did not differ from random expectation. This was true on the level of genus, clade and species group, indicating that CHC traits are evolutionary labile. In contrast, the presence or absence of alkenes and alkadienes was highly conserved within the C. levior group. Hence, the presence or absence of biosynthetic pathways may be phylogenetically constrained, especially at lower taxonomic levels. Our study shows that CHC composition can evolve rapidly, allowing insects to quickly adapt their chemical profiles to external selection pressures, whereas the presence of biosynthetic pathways appears more constrained. However, our results stress the importance to consider the taxonomic level when investigating phylogenetic constraints.     

The new Arctic side-gilled sea slug genus <Emphasis Type="Italic">Boreoberthella</Emphasis> (Gastropoda,Opisthobranchia): Pleurobranchoidean systematics and evolution revisited

Most of the ca. 100 known pleurobranchoid side gilled sea slug species are confined to temperate and warm coastal waters worldwide. Exceptions were five enigmatic Antarctic and southern deep sea species. Herein the first Arctic deep water pleurobranchid, Boreoberthella augusta gen. et spec. nov., is anatomically described. To reveal the origin, relationships and phylogeography of Boreoberthella, a cladistic analysis of 24 pleurobranchoid taxa representing all genera and traditional higher groups was prepared. The morphological data set includes 72 characters; many of them, such as details of the copulatory apparatus, were explored for the first time. The monophyly of both Pleurobranchoidea and Pleurobranchaeidae is confirmed. In contrast to an earlier study, the southern Ocean deep-water species Tomthompsonia antarctica results as basal offshoot of the monophyletic though poorly supported Pleurobranchidae which show a secondary, internal shell. The traditional genus Berthella with worldwide temperate and tropical members may represent an evolutionary grade rather than a clade. The monotypic genera Parabathyberthella and Polictenidia are synonymized with Bathyberthella according to taxonomic and phylogenetic evidence. The basal pleurobranchaeid genus Pleurobranchella, together with Tomthompsonia, Bathyberthella, and Boreoberthella are discussed as potential relics of a cold-water related early nudipleuran radiation in Antarctica, with subsequent dispersal through the depths of the world oceans. The ancestor of Pleurobranchus species, the closest relatives of Boreoberthella, colonized coastal and warmer waters and radiated there.     

Unintentional selection,unanticipated insights: introductions,stocking and the evolutionary ecology of fishes

Natural environmental change has produced countless opportunities for species to disperse into and persist in habitats where they previously did not exist. Introduction and stocking programmes have facilitated similar sorts of colonization opportunities across considerably greater geographical scales and often in much shorter periods of time. Even though the mechanism of colonization differs, the result can be the same: evolutionary change in the colonizing population in response to novel selection pressures. As a consequence, some human‐mediated fish transfers have unintentionally yielded novel research opportunities to study how phenotypes and genes interact with their environment and affect ecological and evolutionary change. The primary purpose here is to explore how work, directly or indirectly involved with human‐mediated transfers, has unintentionally yielded novel research and research opportunities in fish ecology and evolution. Insights have produced new knowledge or altered previously held perceptions on topics such as local adaptation, rate of evolutionary change, phenotypic plasticity, alternative reproductive strategies, population structure and colonization probability. Well‐documented stocking programmes, especially in terms of history, numbers and original population sources, can provide highly fertile ground for generating further insights on the ecology and evolution of fishes and of the factors likely to influence the success of conservation‐based, restoration programmes.     

Ecomorphological diversification and convergence in fluvial cichlid fishes

Synopsis We compared ecological and morphological patterns among cichlid faunas from three different biotic regions: the Río Tortuguero/Rio Sarapiquf in Costa Rica, the Río Apure drainage in Venezuela, and the Upper Zambezi drainage in Zambia. Cichlids comprise 19 percent of the fish fauna in the Tortuguero and Upper Zambezi drainages and 6.5 percent in the Apure drainage. Cichlid faunas exhibited similar patterns of habitat and food resource utilization, although vegetation-dwelling is more common and detritivory and herbivory are rarer in the Apure fauna. We hypothesize that South American ostariophysan fishes were more preadapted than cichlids to exploit detritivore and herbivore niches. The Zambezi cichlid fauna shows less ecomorphological diversification than the other two faunas, even though the degree of dietary diversification is similar among faunas. Chaetobranchus flavescens from the Venezuelan fauna is the only species that specializes on zooplankton as an adult, and algae grazing (Neetroplus nematopus) and specialized fruit feeding (Cichlasoma tuba) were represented only in the Costa Rican fauna. Based on the most recent hypothesized phylogeny for the family Cichlidae, we identified numerous interfaunal ecomorphological and feeding niche convergences. Patterns of ecomorphological divergence in relation to cladogenesis indicate a faster rate of evolutionary niche diversification in Central American cichlids compared with the two other faunas.     

Morphological and phylogenetic analysis of Raillietina spp. in indigenous chickens (Gallus gallus domesticus) in Bangladesh

Raillietina spp. (Cestoda: Davaineidae), the most common cestodes in indigenous chickens, cause a substantial production loss in poultry industry in Bangladesh. Here, we estimated the prevalence, confirmed the species and determined the genetic pattern of species of Raillietina using molecular tools. We collected and examined 375 chickens randomly from household of different villages of Mymensingh sadar and Gouripur upazila, Mymensingh district and adult parasites were isolated and identified. Genomic DNA was extracted from collected parasites, amplified ITS-2 and ND-1 genes, sequenced and analyzed. Out of 375 samples, 270 (72.0%) were found positive with Raillietina species and mean worm burden was 10.46 ± 0.56. Microscopically, three species of Raillietina, such as R. cesticillus (37.9%), R. echinobothrida (41.1%) and R. tetragona (52.8%) were detected on the basis of their morphological features. The total length, length and width of scolex, sucker and rostellum were also measured. Among different factors, age, farming nature and flock size of chickens were significantly (p < 0.05) influenced Raillietina infections. For further validation, the sequences of ITS-2 gene generated in this study were matched with reference sequences of R. cesticillus, R. echinobothrida and R. tetragona and found 99.63% − 100% similarity. The phylogenetic analyses of ITS-2 and ND-1 sequences were clustered together with the reference sequences of R. cesticillus, R. echinobothrida and R. tetragona confirming microscopic identification. This is the first confirmation of species of Raillietina along with the prevalence of the species, which will be helpful for the formulation of a control strategy and provide basic information for further molecular study.     

Evolution of climatic niche specialization: a phylogenetic analysis in amphibians

The evolution of climatic niche specialization has important implications for many topics in ecology, evolution and conservation. The climatic niche reflects the set of temperature and precipitation conditions where a species can occur. Thus, specialization to a limited set of climatic conditions can be important for understanding patterns of biogeography, species richness, community structure, allopatric speciation, spread of invasive species and responses to climate change. Nevertheless, the factors that determine climatic niche width (level of specialization) remain poorly explored. Here, we test whether species that occur in more extreme climates are more highly specialized for those conditions, and whether there are trade-offs between niche widths on different climatic niche axes (e.g. do species that tolerate a broad range of temperatures tolerate only a limited range of precipitation regimes?). We test these hypotheses in amphibians, using phylogenetic comparative methods and global-scale datasets, including 2712 species with both climatic and phylogenetic data. Our results do not support either hypothesis. Rather than finding narrower niches in more extreme environments, niches tend to be narrower on one end of a climatic gradient but wider on the other. We also find that temperature and precipitation niche breadths are positively related, rather than showing trade-offs. Finally, our results suggest that most amphibian species occur in relatively warm and dry environments and have relatively narrow climatic niche widths on both of these axes. Thus, they may be especially imperilled by anthropogenic climate change.     

Allometric constraints on stability and maximum size in flying fishes: implications for their evolution

Flying fish wing area and wing-loading both rise in strongly negative allometric fashion with increasing body length and mass. Evidence is presented to show that this occurs because: (1) the leading edge of the pectoral fin 'wing' is fixed at 24% of standard length (  L _S) from the snout, (2) the wing length cannot exceed 76% of L _S or the tips will interfere with propulsive tail beat and (3) increased mass demands faster flying and wings with better lift : drag ratios; this selects for tapered, higher aspect ratio wing shapes. A consequence of this situation is that larger flying fishes have centres of mass increasingly further behind the centre of wing pressure. Resultant longitudinal instability restricts the maximum size of the two-winged design and the pelvic fins of four-wingers act as a stabilizing tailplane. These data indicate that the accepted model of evolution of flight in flying fishes (by extension of ballistic leaps) is flawed; it is proposed that evolution of lift-supported surface taxiing in half-beaks with enlarged pectoral fins (enhanced by ground effect) was an essential preliminary; subsequent forward migration of the centre of mass to within the wing chord permitted effective gliding.