Search

The hypothesis that destructive mass extinctions enable creative evolutionary radiations (creative destruction) is central to classic concepts of macroevolution.sup.1,2. However, the relative impacts of extinction and radiation on the co-occurrence of species have not been directly quantitatively compared across the Phanerozoic eon. Here we apply machine learning to generate a spatial embedding (multidimensional ordination) of the temporal co-occurrence structure of the Phanerozoic fossil record, covering 1,273,254 occurrences in the Paleobiology Database for 171,231 embedded species. This facilitates the simultaneous comparison of macroevolutionary disruptions, using measures independent of secular diversity trends. Among the 5% most significant periods of disruption, we identify the 'big five' mass extinction events.sup.2, seven additional mass extinctions, two combined mass extinction-radiation events and 15 mass radiations. In contrast to narratives that emphasize post-extinction radiations.sup.1,3, we find that the proportionally most comparable mass radiations and extinctions (such as the Cambrian explosion and the end-Permian mass extinction) are typically decoupled in time, refuting any direct causal relationship between them. Moreover, in addition to extinctions.sup.4, evolutionary radiations themselves cause evolutionary decay (modelled co-occurrence probability and shared fraction of species between times approaching zero), a concept that we describe as destructive creation. A direct test of the time to over-threshold macroevolutionary decay.sup.4 (shared fraction of species between two times [less than or equal to] 0.1), counted by the decay clock, reveals saw-toothed fluctuations around a Phanerozoic mean of 18.6 million years. As the Quaternary period began at a below-average decay-clock time of 11 million years, modern extinctions further increase life's decay-clock debt. Analysis of data on species co-occurrence in the Paleobiology Database using a new machine learning algorithm reveals that mass extinctions and mass radiations are not coupled in evolutionary history., Author(s): Jennifer F. Hoyal Cuthill [sup.1] [sup.2] [sup.3] [sup.4] , Nicholas Guttenberg [sup.3] [sup.5] [sup.6] , Graham E. Budd [sup.7] Author Affiliations: (1) Institute of Analytics and Data Science, University [...]

Gaidropsarus Rafinesque, 1810 is a genus of marine teleost characterized by a high ecological diversity and by species inhabiting from the intertidal zone to the deep-sea. Several taxonomic conundrums have been historically present in this taxon due to its conservative morphology and the lack of available specimens. Species delimitation analyses were carried out in multiple datasets combining both mitochondrial (COI, CytB, ND2) and nuclear (Rho, ZIC1) genetic markers. Despite some incongruence between mitochondrial and nuclear data, the analyses supported the synonymy between Gaidropsarus biscayensis and Gaidropsarus macrophthalmus and the molecular confirmation of a recently new described species Gaidropsarus gallaeciae, in the North Atlantic Ocean. Furthermore, recent speciation events can explain the close relationships among several Gaidropsarus species, including Gaidropsarus granti-Gaidropsarus vulgaris and Gaidropsarus argentatus-Gaidropsarus ensis. These results support previous findings highlighted through DNA Barcoding analyses. Incongruences between mtDNA and nDNA have arisen between Gaidropsarus guttatus and Gaidropsarus mediterraneus, therefore, further analyses will be necessary to unravel the phenomena related to them., Author(s): David Barros-García [sup.1] , Ángel Sebastián Comesaña [sup.2] , Rafael Bañón [sup.3] [sup.4] , Francisco Baldó [sup.5] , Juan Carlos Arronte [sup.6] , Elsa Froufe [sup.1] , Alejandro De [...]

The maintenance of species boundaries when opportunities for admixture are abundant, is a poorly understood phenomenon for many taxa. While many mechanisms for maintaining species boundaries have been described their relative importance depends largely on the particulars of the system in question. Aggregating social behavior can be a means to keep sympatric sister species distinct if it leads to segregation during reproduction. The widespread Caribbean reef gobies Coryphopterus personatus and C. hyalinus are sympatric sister species with nearly identical morphology that spend their entire adult lives in shoals in which reproduction occurs. To date no studies have investigated whether shoals are species-specific, which would be expected if aggregating behavior helps to maintain species boundaries. To address this, the species of individual fishes collected from 16 shoals were identified using morphology, mitochondrial sequence data, and microsatellite allele frequencies. Levels of admixture between the species were also assessed. Shoals were generally composed of both species in similar proportions to their relative abundances on the reef, where the shoals were found, indicating that the species are not behaviorally segregating. For most specimens, morphological, mitochondrial, and nuclear data were congruent with a single species, but 18 individuals showed disagreements with microsatellite genotypes of 16 suggesting some level of historic/contemporary admixture. Of these, two were identified as likely first- or second-generation hybrids or backcrosses. Despite co-occurrence and evidence of some gene flow, the two species show little admixture overall suggesting that microscale differences in breeding site selection, allochrony, and/or cryptic mate choice may play an important role in the maintenance of species boundaries despite cooccurrence well within the range typically thought of as sympatry., Author(s): Jason D. Selwyn [sup.1] , Elizabeth P. Hunt [sup.1] , David S. Portnoy [sup.1] , J. Derek Hogan [sup.1] Author Affiliations: (1) grid.264759.b, 0000 0000 9880 7531, Department of [...]

Field observations of morphologically intermediate water lilies in central Canada suggested a hybrid origin involving the parents Nymphaea odorata Aiton and Nymphaea leibergii Morong despite the fertile nature of these plants. Sequencing of the nrlTS and the plastid rps4-trnT-trnF regions further including all members of the north temperate Nymphaea subg. Nymphaea clade, and samples from other hybrids occurring in North America in the wild, allowed us to determine that individuals of N. leibergii and of N. odorata were the maternal and paternal parents, respectively. Hybrids of New England have all proven to be sterile, are genetically variable, and probably are F1. By comparison, the plants of east-central Saskatchewan and west-central Manitoba are fully fertile and genetically uniform based on ISSR and sequence data. On the basis of this evidence, the latter are here described as a new species, Nymphaea loriana sp. nov., which may have originated during the Holocene climatic optimum about 6000 years ago in a past contact zone of the parents. Further hybrids detected between N. odorata and Nymphaea tetragona Georgi, as well as between N. leibergii and N. tetragona, were always sterile. Gene trees of the temperate clade of Nymphaea converge onaclade of small-flowered water lilies (sect. Chamaenymphaea), including N. leibergii, N. tetragona, and Nymphaea pygmaea. Nuclear ITS further resolves an American clade (Nymphaea mexicana Zucc.--N. odorata) sister to all remaining species. This split into two major subclades also appears in the otherwise less resolved rps4-trnT-trnF tree. Thus the origin of N. loriana is a reticulation between long-separated parental lineages. Key words: Nymphaea subg. Nymphaea, phylogeny, divergent ITS copies, hybridization, post-glacial migration, species monophyly. Les observations de terrain des nenuphars du centre du Canada dont la morphologie est intermediaire ont suggere qu'ils emaneraient d'un hybride dont Nymphaea odorata Aiton et Nymphaea leibergii Morong seraient les parents, malgre la nature fertile de ces vegetaux. Le sequencage des regions de l'ETI-nr et du plastide rps4-trnT-trnF incluant tous les membres du clade tempere Nymphaea subg. Nymphaea, et des echantillons d'autres hybrides presents dans la nature en Amerique du Nord, ont permis aux auteurs de determiner que les individus N. leibergii et N. odorata constituaient les parents maternels et paternels, respectivement. Les hybrides de Nouvelle-Angleterre se sont tous reveles steriles et genetiquement variables, constituant probablement la F1. En comparaison, les plantes du centre-est de la Saskatchewan et du centre-ouest du Manitoba sont pleinement fertiles et genetiquement uniformes selon des donnees d'ISSR et de sequences. Sur le base de ces elements probants, ces dernieres sont decrites ici comme constituant une espece nouvelle, Nymphaea loriana sp. nov., qui pourrait avoir emerge durant l'optimum climatique holocene il y a environ 6000 ans, dans une zone de contact passee des parents. D'autres hybrides detectes entre N. odorata et Nymphaea tetragona Georgi ainsi qu'entre N. leibergii et N. tetragona etaient toujours steriles. Les arbres genetiques du clade tempere des Nymphaea convergent sur un clade de nenuphars a petites fleurs (sect. Chamaenymphaea), incluant N. leibergii, N. tetragona et Nymphaea pygmaea. L'ETI nucleaire resout davantage un clade Americain (Nymphaea mexicana Zucc.--N. odorata), sreur de toutes les especes restantes. Ce detachement en deux sous-clades majeurs apparait aussi dans l'arbre rps4-trnT-trnF par ailleurs moins resolu. L'origine de N. loriana constitue alors une reticulation entre des lignages parentaux eloignes. [Traduit par la Redaction] Mots-cles : Nymphaea subg. Nymphaea, phylogenie, copies d'ETI divergents, hybridation, migration post-glaciaire, monophylie d'une espece., Introduction The water-lily genus Nymphaea is the most speciose, phenotypically diverse, and geographically widespread member of the Nymphaeales (Schneider and Williamson 1993; Borsch et al. 2007), with 45-50 species recognized [...]

Many marine ecologists aspire to use genetic data to understand how selection and demographic history shape the evolution of diverging populations as they become reproductively isolated species. I propose combining two types of genetic analysis focused on this key early stage of the speciation process to identify the selective agents directly responsible for population divergence. Isolation-with-migration (IM) models can be used to characterize reproductive isolation between populations (low gene flow), while codon models can be used to characterize selection for population differences at the molecular level (especially positive selection for high rates of amino acid substitution). Accessible transcriptome sequencing methods can generate the large quantities of data needed for both types of analysis. I highlight recent examples (including our work on fertilization genes in sea stars) in which this confluence of interest, models, and data has led to taxonomically broad advances in understanding marine speciation at the molecular level. I also highlight new models that incorporate both demography and selection: simulations based on these theoretical advances suggest that polymorphisms shared among individuals (a key source of information in IM models) may lead to false-positive evidence of selection (in codon models), especially during the early stages of population divergence and speciation that are most in need of study. The false-positive problem may be resolved through a combination of model improvements plus experiments that document the phenotypic and fitness effects of specific polymorphisms for which codon models and IM models indicate selection and reproductive isolation (such as genes that mediate sperm-egg compatibility at fertilization)., Introduction An important problem in biodiversity research is to understand the ecological and evolutionary origins of reproductive isolation and the formation of biological species (Coyne and Orr, 2004; Hey et [...]

The formation of a new species can occur by an asexual mechanism by transfer of entire nuclear genomes between plant cells as shown by the creation of a new allopolyploid plant from parental herbaceous and woody plant species, this mechanism is a potential new tool for crop improvement. Speciation by growing together Grafting is a common occurrence in nature and is familiar as a means of manipulating plants and trees for use in agriculture and horticulture. Here Ralph Bock and colleagues demonstrate that entire nuclear genomes can be transferred across the graft junction from plant to plant. In grafting experiments between the tree tobacco Nicotiana glauca and the cigarette tobacco N. tabacum (woody and herbaceous species, respectively), horizontal transfer of nuclear genomes can result in the formation of a new polyploid species -- Nicotiana tabauca. This is an example of allopolyploidization, the combination of the genomes from two different species that has contributed to evolutionary innovation, adaptation, speciation and domestication. It is thought to occur through hybridization events between species, accompanied or followed by genome duplication, but this work shows that it can also occur through an asexual mechanism that is readily available as a potential tool for crop improvement. Allopolyploidization, the combination of the genomes from two different species, has been a major source of evolutionary innovation and a driver of speciation and environmental adaptation.sup.1,2,3,4. In plants, it has also contributed greatly to crop domestication, as the superior properties of many modern crop plants were conferred by ancient allopolyploidization events.sup.5,6. It is generally thought that allopolyploidization occurred through hybridization events between species, accompanied or followed by genome duplication.sup.6,7. Although many allopolyploids arose from closely related species (congeners), there are also allopolyploid species that were formed from more distantly related progenitor species belonging to different genera or even different tribes.sup.8. Here we have examined the possibility that allopolyploidization can also occur by asexual mechanisms. We show that upon grafting--a mechanism of plant-plant interaction that is widespread in nature--entire nuclear genomes can be transferred between plant cells. We provide direct evidence for this process resulting in speciation by creating a new allopolyploid plant species from a herbaceous species and a woody species in the nightshade family. The new species is fertile and produces fertile progeny. Our data highlight natural grafting as a potential asexual mechanism of speciation and also provide a method for the generation of novel allopolyploid crop species., Author(s): Ignacia Fuentes [sup.1] , Sandra Stegemann [sup.1] , Hieronim Golczyk [sup.2] , Daniel Karcher [sup.1] , Ralph Bock [sup.1] Author Affiliations: (1) Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, [...]

I analyzed larval polytene chromosomes to determine if the hypothesized remnants of an incipient speciation event in the Simulium arcticum complex of black flies previously discovered at the Coeur d'Alene River, Idaho existed elsewhere. This population not only had F chromosomes that defined two members of the S. arcticum complex: S. arcticum sensu stricto and S. saxosum, but also possessed combinations of sex chromosomes of the two that were in genetic equilibrium with respect to all sex chromosome types. The geographic overlap between S. saxosum to the west and S. arcticum s. s. to the east generally runs north and south of the Coeur d'Alene River. Accordingly, I made 37 additional collections in a north-south orientation during 2011-2013. Larvae from 10 of the 37 collections had sex chromosome types identical to those of the previously studied site at the Coeur d'Alene River, thus expanding the area of putative remnant populations. The St. Joe River not only had F chromosome combinations identical to those of larvae at the Coeur d Alene but also had a cytotype new to science based on distinct sex chromosomes ([X.sub.0][Y.sub.IIL-79]) in males. These observations: (1) increase the known geographic area of presumed remnant populations of S. arcticum s. s., of S. saxosum and their combinational types to about 3500 [km.sup.2]; (2) suggest that mating trials still occur; and (3) describe the structure and frequency of inversions in two new cytotypes of the S. arcticum complex., INTRODUCTION In their seminal publication, Speciation, Jerry Coyne and Allen Orr (2004) suggested that it is important to investigate and understand processes that occur prior to and during a speciation [...]

Speciation generally involves a three-step process--range expansion, range fragmentation and the development of reproductive isolation between spatially separated populations (1,2). Speciation relies on cycling through these three steps and each may limit the rate at which new species form (1,3). We estimate phylogenetic relationships among all Himalayan songbirds to ask whether the development of reproductive isolation and ecological competition, both factors that limit range expansions (4), set an ultimate limit on speciation. Based on a phylogeny for all 358 species distributed along the eastern elevational gradient, here we show that body size and shape differences evolved early in the radiation, with the elevational band occupied by a species evolving later. These results are consistent with competition for niche space limiting species accumulation (5). Even the elevation dimension seems to be approaching ecological saturation, because the closest relatives both inside the assemblage and elsewhere in the Himalayas are on average separated by more than five million years, which is longer than it generally takes for reproductive isolation to be completed (2,3,6); also, elevational distributions are well explained by resource availability, notably the abundance of arthropods, and not by differences in diversification rates in different elevational zones. Our results imply that speciation rate is ultimately set by niche filling (that is, ecological competition for resources), rather than by the rate of acquisition of reproductive isolation., Range expansions are a critical step in the speciation cycle: without them, allopatric and parapatric forms would have ranges of ever decreasing size, unlikely to be further fragmented by barriers [...]

The Yellow-spotted River Turtle (Podocnemis unifilis Troschel, 1848) and the South American River Turtle (Podocnemis expansa (Schweigger, 1812)) are two turtles species that are widely distributed and have ecological, economic, and cultural importance in the Amazon basin. Although sympatric regarding most of their distribution, few studies have addressed the coexistence of these two species. To examine this, we analyzed the trophic level and the primary carbon source from the diets of both species in Baixo Araguaia, Tocantins, Brazil, using stable isotope analyses of carbon (δ[sup.13]C) and nitrogen (δ[sup.15]C). We also verified possible intraspecific variations (related to sex and body mass) in the trophic levels and primary carbon sources of their diets. Podocnemis unifilis had higher values of δ[sup.15]C than P. expansa, averaging 7.59‰ and 5.06‰, respectively, a difference which may indicate a possible trophic change owing to exploiting different food resources. No differences were found between the two species in relation to δ[sup.13]C (mean values of -26.2‰ and -26.1‰, respectively). The similarity between δ[sup.13]C values suggests that the sources of their basal feeding are the same, consisting mainly of [C.sub.3] plants. There was no intraspecific variation in the values of δ[sup.13]C and δ[sup.15]C. Key words: Podocnemis unifilis, Yellow-Spotted River Turtle, Podocnemis expansa, South American River Turtle, coexistence, sympatric, intraspecific variations. La podocnemide de Cayenne (Podocnemis unifilis Troschel, 1848) et la podocnemide elargie (Podocnemis expansa (Schweigger, 1812)) sont deux especes de tortue de repartition vaste qui revetent une importance ecologique, economique et culturelle dans le bassin amazonien. Bien qu'elles soient sympatriques pour ce qui est de la majeure partie de leurs aires de repartition, peu d'etudes se sont penchees sur la coexistence des deux especes. A cette fin, nous avons analyse le niveau trophique et la principale source de carbone des regimes alimentaires de ces especes dans la region de Baixo Araguaia de l'Etat de Tocantins, au Bresil, en faisant appel a l'analyse des isotopes stables du carbone (δ[sup.13]C) et de l'azote (δ[sup.15]C). Nous avons egalement verifie la presence d'eventuelles variations intraspecifiques (associees au sexe et a la masse corporelle) sur le plan des niveaux trophiques et des principales sources de carbone dans leurs regimes alimentaires. Podocnemis unifilis presentait des valeurs de δ[sup.15]C plus elevees que P. expansa (valeurs moyennes de 7,59 ‰ et 5,06 ‰, respectivement), une difference qui pourrait refleter un possible changement trophique decoulant de l'exploitation de ressources alimentaires differentes. Aucune difference n'a ete observee entre les deux especes en ce qui concerne δ[sup.13]C (valeurs moyennes de -26,2 ‰ et -26,1 ‰, respectivement). Cette similitude des valeurs de δ[sup.13]C porte a croire que les sources de leur alimentation de base sont les memes, consistant principalement de plantes [C.sub.3]. Aucune variation intraspecifique des valeurs de δ[sup.13]Cetde δ[sup.15]C n'a ete observee. Mots-cles: Podocnemis unifilis, podocnemide de Cayenne, Podocnemis expansa, podocnemide elargie, coexistence, sympatrique, variations intraspecifiques. [Traduit par la Redaction], Introduction The Yellow-spotted River Turtle (Podocnemis unifilis Troschel, 1848) and the South American River Turtle (Podocnemis expansa (Schweigger, 1812)) are ecologically, economically, and culturally important neotropical chelonians in the Amazon [...]

Environmental change, including that caused directly or indirectly by invasive species, presents a major threat to the persistence of native freshwater biodiversity. The invasive American signal crayfish (Pacifastacus leniusculus (Dana, 1852)) has recently been implicated in the collapse of a pair of threespine stickleback (Gasterosteus aculeatus L., 1758) species in Enos Lake, British Columbia, through introgressive hybridization; yet there are few data describing potential interactions between crayfish and these recently evolved stickleback species. We conducted a behavioural study, using an intact sympatric G. aculeatus species pair from a nearby lake, to examine if and how interactions with P. leniusculus may influence the breeding behaviour of sticklebacks. We found that the reproductive behaviour of limnetic males was disrupted to a greater degree than that of benthic males, suggesting that crayfish may disproportionately impact limnetic male reproductive success and may have contributed to biased hybridization between the Enos Lake species pair. Our study illustrates how newly differentiated taxa may be especially susceptible to environmental perturbations, particularly those caused by invasive species. Key words: Gasterosteus aculeatus, threespine stickleback, Pacifastacus leniusculus, American signal crayfish, invasive species, conservation, hybridization, reverse speciation, reproduction, species at risk. Les changements environnementaux, dont ceux causes directement ou indirectement par des especes envahissantes, constituent une grande menace pour la persistance de la biodiversite d'eau douce indigene. L'ecrevisse de Californie (Pacifastacus leniusculus (Dana, 1852)), une espece envahissante, a recemment ete impliquee dans l'effondrement d'une paire d'especes d'epinoches a trois epines (Gasterosteus aculeatus L., 1758) dans le lac Enos, en Colombie-Britannique, decoulant d'une hybridation introgressive. Peu de donnees sont toutefois disponibles sur les interactions potentielles des ecrevisses et de ces especes d'epinoches recemment formees. Nous avons realise une etude comportementale dans laquelle nous avons utilise une paire d'especes sympatriques intacte de G. aculeatus provenant d'un lac a proximite pour verifier si des interactions avec P. leniusculus peuvent influencer le comportement reproducteur des epinoches et, le cas echeant, de quelle maniere. Nous avons observe que le comportement reproducteur des males limnetiques etait plus perturbe que celui des males benthiques, ce qui suggere que les ecrevisses pourraient avoir une incidence disproportionnee sur le succes de reproduction des males limnetiques et pourraient ainsi avoir contribue a une hybridation biaisee entre la paire d'especes du lac Enos. L'etude illustre comment des taxons nouvellement differencies pourraient etre particulierement sensibles aux perturbations du milieu, notamment celles causees par des especes envahissantes. Mots-cles : Gasterosteus aculeatus, epinoche a trois epines, Pacifastacus leniusculus, ecrevisse de Californie, espece envahissante, conservation, hybridization, speciation inversee, reproduction, especes en peril. [Traduit par la Redaction], Introduction Repeated glaciation of temperate regions is associated with lower alpha diversity in freshwater systems relative to those in lower latitudes (Lomolino et al. 2006), but is also associated with [...]

Colour polymorphism exemplifies extreme morphological diversity within populations (1,2). It is taxonomically widespread but generally rare. Theory suggests that where colour polymorphism does occur, processes generating and maintaining it can promote speciation but the generality of this claim is unclear (1). Here we confirm, using species-level molecular phylogenies for five families of non-passerine birds, that colour polymorphism is associated with accelerated speciation rates in the three groups in which polymorphism is most prevalent. In all five groups, colour polymorphism is lost at a significantly greater rate than it is gained. Thus, the general rarity and phylogenetic dispersion of colour polymorphism is accounted for by a combination of higher speciation rate and higher transition rate from polymorphism to monomorphism, consistent with theoretical models where speciation is driven by fixation of one or more morphs (3). This is corroborated by evidence from a species-level molecular phylogeny of passerines, incorporating 4,128 (66.5%) extant species, that polymorphic species tend to be younger than monomorphic species. Our results provide empirical support for the general proposition, dating from classical evolutionary theory (2,4-6), that colour polymorphism can increase speciation rates., The study of colour-polymorphic species has been crucial for the development of evolutionary theory (5-7). Polymorphic systems provide critical insights into processes generating and maintaining genetic and phenotypic diversity within [...]

The presence of aluminium in natural waters is of major concern at present because of the potential threat for the health of a number of species, including humans. In natural water, aluminium exists in different forms depending on the concentrations of various other species, organic matter, the types of minerals, the pH, etc. The aluminium species in the natural water--gibbsite system is considered in this work. The main approaches for estimating of the individual concentrations of the aluminium species involve the use of reliable thermodynamic data, together with experimental measurements of free or total concentrations of major components. The new type of diagrams based on graphical and computerized methods, which quantitatively describe the distribution of soluble and insoluble, inorganic, and organic, and monomeric and polymeric aluminium species in heterogeneous aquatic systems is presented. This approach utilizes thermodynamic relationships coupled with original mass balance constraints, where the mineral phases are explicitly expressed. The factors influencing the distribution of soluble and insoluble aluminium species in aquatic systems were analyzed. The new type of developed diagrams may be used to interpret data obtained within the framework of water-quality monitoring programs. Key words: gibbsite, diagram of distribution, heterogeneous system, thermodynamic stability. La presence d'aluminium dans les eaux naturelles est maintenant une preoccupation majeure en raison des dangers potentiels que ce metal presente pour la sante d'un certain nombre d'especes, dont les humains. Dans les eaux naturelles, l'aluminium existe sous diverses formes suivant, entre autres, les concentrations des diverses autres especes, des matieres organiques, des types de mineraux et du pH. Dans le present travail, on considere la gibbsite comme l'espece d'aluminium qui existe dans le systeme d'eau naturelle. Les principales approches utilisees pour evaluer les concentrations individuelles des especes d' aluminium impliquent l'utilisation de donnees thermodynamiques fiables en relation avec des mesures experimentales des concentrations libres ou totales des composants principaux. On a mis au point un nouveau type de diagrammes, bases sur des methodes graphiques et des ordinateurs, qui permet de decrire d'une facon quantitative la distribution des especes d' aluminium solubles et insolubles, inorganiques ou organiques, monomeres ou polymeres, dans des systemes aquatiques heterogenes. Cette approche utilise des relations thermodynamiques liees aux contraintes originales de balance des masses, dans lesquelles les phases minerales sont exprimees d'une facon explicite. On a analyse les facteurs qui influencent la distribution des especes aluminium solubles et insolubles dans les systemes aquatiques. Le nouveau type de diagramme qui a ete mis au point peut etre utilise pour interpreter des donnees obtenues dans le cadre de programmes de surveillance de la qualite de l'eau. Mots-cles : gibbsite, diagramme de distribution, systeme heterogene, stabilite thermodynamique. [Traduit par la Redaction], Introduction Chemical forms of aluminium occurrence in natural waters are quite various, as [Al.sup.3+] forms complexes with O[H.sup.-], S[O.sub.4.sup.2-], [F.sup.-], and organic compounds. It is known that different chemical forms [...]

Eleven weedy or wild species or subspecies of the genus Secale L. were compared with a set of cultivated rye accessions, based on inter-simple sequence repeat (ISSR) markers to analyze their phylogenetic relationships. A total of 846 bands were amplified from reactions using 12 screening primers, including 79 loci with a mean of 10.1 alleles per locus. The number of amplified bands for each primer ranged from 12 to 134, with a mean of 70.5 amplified bands per primer. The presence and distribution of amplified bands in different accessions demonstrate that a rapid evolutionary trend of microsatellite repeats occurred during the speciation process from the perennial wild form to annual cultivated rye. In addition, variation, amplification, and deletion of microsatellites in genomes revealed phylogenetic relationships in the genus Secale. Analysis of the presence, number, and distribution of amplified bands in genomes, as well as the comparison with genetic similarity (GS) indices based on ISSR, indicate that Secale strictum subsp. africanum (Stapf) Hammer, Secale strictum anatolicum (Boiss.) Hammer, Secale sylvestre Host, and Secale strictum subsp. strictum (C. Presl) Hammer emerged in succession from a common ancestor of Secale following geographic separation and genetic differentiation. The annual weedy rye evolved from S. strictum subsp. strictum, which was domesticated as present-day cultivated rye. Data from ISSR analyses separated all investigated accessions of the genus Secale into three distinct groups. These results support the division of the genus Secale into three species: the annual wild species S. sylvestre; the perennial wild species S. strictum, including several differential subspecies forms such as strictum, africanum, and anatolicum; and S. cereale, including cultivated and weedy rye as subspecies forms. Key words: Secale, inter-simple sequence repeat (ISSR), phylogenetic relationship, genetic diversity, evolution. Onze especes ou sous-especes sauvages du genre Secale ont ete comparees avec un jeu de cultivars de seigle a l'aide de marqueurs << inter-simple sequence repeat >> (ISSR) pour analyser leurs relations phylogenetiques. Au total, 846 bandes ont ete amplifiees suite a des amplifications realisees avec 12 amorces et de ce nombre 79 locus presentaient en moyenne 10,1 alleles. Le nombre de bandes amplifiees a l'aide de chaque amorce variait entre 12 et 134, pour une moyenne de 70,5 bandes par amorce. La presence et la distribution de bandes amplifiees au sein des differentes accessions suggerent une evolution rapide des microsatellites au cours du processus de speciation ayant mene des especes sauvages perennes au seigle annuel cultive. De plus, la variation, l'amplification et la deletion chez les microsatellites au sein de ces genomes nous renseignent sur les relations phylogenetiques au sein du genre Secale. L'analyse de la presence, du nombre et de la distribution des bandes amplifiees au sein des genomes de meme que la comparaison des indices de similarite genetique (GS) fondes sur les ISSR indiquent que le Secale strictum ssp. africanum, le Secale strictum ssp. anatolicum, le Secale sylvestre et le Secale strictum ssp. strictum seraient apparus successivement a partir d'un ancetre commun du seigle aux termes d'une separation geographique et d'une differenciation genetique. Les especes annuelles sauvages du seigle seraient derivees du S. strictum ssp. strictum, lequel a ete domestique pour donner le seigle cultive aujourd'hui. Les donnees ISSR ont permis de separer en trois groupes toutes les accessions examinees au sein du genre Secale. Ces resultats supportent la division du genre Secale en trois especes: l'espece sauvage annuelle S. sylvestre; l'espece e, incluant les formes cultivees et sauvages comme sous-especes. Mots-cles: Secale, << inter-simple sequence repeat >> (ISSR), relations phylogenetiques, diversite genetique, evolution. [Traduit par la Redaction], Introduction The genus Secale, which includes rye, is a small but economically important taxon. Cultivated rye (Secale cereale L.) is second only to wheat (Triticum spp. L.) among grains most [...]

Ecological speciation occurs when adaptation to different environments or resources causes the evolution of reproductive isolation. This process is now thought to be very important in the evolution of biological diversity. Indeed, support for ecological speciation is so often asserted in the literature that one can get the impression of ubiquity. Eager to ride on the coattails of this exciting work, my own research has investigated ecological speciation in guppies, sticklebacks, and Darwin's finches. Much to my initial dismay, I failed to find simple and strong signatures of ecological speciation in the first two of these systems. Setting aside the possibility of personal incompetence, my apparent deviation from ubiquity might simply reflect an existing literature bias. This bias seems obvious in retrospect given that essentially all published studies of ecological speciation purport to be confirmatory, whereas many cases of divergent selection and adaptive divergence are associated with only weak to modest levels of reproductive isolation. In short, different populations can be arrayed along a continuum from panmixia to complete reproductive isolation. Variation along this continuum might profitably be used for studying factors, outlined herein, that can promote or constrain 'progress' toward ecological speciation. La speciation ecologique se produit lorsqu'une adaptation a des ressources ou des milieux differents entraine l'evolution d'un isolement reproductif. On croit actuellement que ce processus est tres important dans l'evolution de la diversite biologique. En fait, la speciation ecologique est si souvent invoquee dans la litterature qu'on a l'impression qu'elle est ubiquiste. Dans la foulee de cette recherche interessante, mes travaux personnels ont examine la speciation ecologique chez les guppys, les epinoches et les pinsons de Darwin. Au depart, il m'a ete impossible, a mon desarroi, de trouver des signatures simples et prononcees de speciation ecologique dans les deux premiers de ces systemes. Excluant la possibilite de mon incompetence personnelle, mon incapacite a trouver l'ubiquite du phenomene peut etre due a une distorsion de la litterature actuelle. Retrospectivement, cette distorsion parait evidente parce qu'essentiellement toutes les etudes publiees sur la speciation ecologique pretendent avoir un caractere confirmatif, alors que plusieurs cas de selection divergente et de divergence adaptative sont associes avec seulement des niveaux faibles a modestes d'isolement reproductif. Bref, les diffe rentes populations peuvent etre placees sur un continuum qui va de la panmixie a l'isolement reproductif complet. La variation le long de ce gradient peut etre utilisee avec profit pour etudier facteurs, enumeres ici, qui peuvent favoriser ou restreindre la << progression >> vers la speciation ecologique., Introduction Ecological speciation can perhaps be best illustrated by reference to a clear example from nature. For this, I will use the threespine stickleback (Gasterosteus aculeatus) populations in a few [...]

In recent years, strikingly consistent patterns of biodiversity have been identified over space, time, organism type and geographical region (1,2). A neutral theory (assuming no environmental selection or organismal interactions) has been shown to predict many patterns of ecological biodiversity (2,3). This theory is based on a mechanism by which new species arise similarly to point mutations in a population without sexual reproduction. Here we report the simulation of populations with sexual reproduction, mutation and dispersal. We found simulated time dependence of speciation rates, species-area relationships and species abundance distributions consistent with the behaviours found in nature (1,13). From our results, we predict steady speciation rates, more species in one-dimensional environments than two-dimensional environments, three scaling regimes of species-area relationships and lognormal distributions of species abundance with an excess of rare species and a tail that may be approximated by Fisher's logarithmic series. These are consistent with dependences reported for, among others, global birds (4) and flowering plants (5) marine invertebrate fossils (6), ray-finned fishes (7), British birds (8,9) and moths (10), North American songbirds (11), mammal fossils from Kansas (12) and Panamanian shrubs (13). Quantitative comparisons of specific cases are remarkably successful. Our biodiversity results provide additional evidence that species diversity arises without specific physical barriers (6,11,14). This is similar to heavy traffic flows, where traffic jams can form even without accidents or barriers (15)., Speciation studies have identified conditions under which speciation events can occur. Allopatry is considered the dominant form of speciation. Studies of partial barriers (parapatric speciation) and debates about sympatric speciation [...]

Abstract: The life cycle of the Northeast Pacific sea nettle, Chrysaora fuscescens Brandt, 1835, is described from gametes to the juvenile medusa stage. In vitro techniques were used to fertilize [...]

Selection is widely accepted as the principal force shaping phenotypic variation within populations. Its importance in speciation and macroevolution has been questioned, however, because phenotypic differences between species or higher taxa sometimes appear to be nonadaptive. Here, we use the quantitative trait locus (QTL) sign test to evaluate the importance of directional selection in phenotypic divergence. If a trait has a history of directional selection, QTL effects should be mostly in the same direction; otherwise QTLs with antagonistic effects should be common. Analysis of QTL effects for 572 traits from 86 studies revealed significantly fewer antagonistic QTLs than expected under neutrality, a result that validates Darwin's claim that phenotypic diversification is caused mainly by selection. Moreover, interspecific trait differences were more strongly or consistently selected than intraspecific differences, strengthening a growing consensus among students of speciation that directional selection is the primary cause of speciation. Contrary to studies of selection in contemporary populations, life history traits appear to be selected more strongly than morphological traits, but traits related to the timing of development are weakly selected relative to most other traits.

Lotus japonicus is a model plant for the legume family. To facilitate map-based cloning approaches and genome analysis, we performed an extensive characterization of the chromosome complement of the species. A detailed karyotype of L. japonicus Gifu was built and plasmid and BAC clones, corresponding to genetically mapped markers (see the accompanying article by SANDAL et al. 2002, this issue), were used for FISH to correlate genetic and chromosomal maps. Hybridization of DNA clones from 32 different genomic regions enabled the assignment of linkage groups to chromosomes, the comparison between genetic and physical distances throughout the genome, and the partial characterization of different repetitive sequences, including telomeric and centromeric repeats. Additional analysis of L. filicaulis and its [F.sub.1] hybrid with L. japonicus demonstrated the occurrence of inversions between these closely related species, suggesting that these chromosome rearrangements are early events in speciation of this group.

Pitman and Jehl (1998) recently argued that Masked Boobies (formerly Sula dactylatra granti) breeding on the Nazca Plate in the eastern Pacific Ocean are morphologically and ecologically distinct from other Masked Boobies and may represent a full species. The American Ornithologists' Union subsequently elevated that subspecies to a full species: the Nazca Booby (S. granti). To evaluate that change in classification, we compared sequence variation in the mitochondrial cytochrome-b gene among 75 Nazca Boobies and 37 Masked Boobies representing three subspecies from the central and eastern Pacific and Atlantic oceans. Results indicated strong differentiation of cytochrome-b variation among taxa. Sequences constituted three distinct groups: Nazca Boobies, Masked Boobies from the central and eastern Pacific (S. d. personata and S. d. californica), and Masked Boobies (S. d. dactylatra) from the Caribbean and Atlantic. Those three groups probably diverged within a very short period, 400,000-500,000 years ago. Our results support the proposal that S. granti represents a distinct species.

Researchers strive to understand what makes species different, and what allows them to survive in the time and space that they do. Many models have been advanced which encompass an array of ecological, evolutionary, mathematical, and logical principles. The goal has been to develop ecological theories that can, among other things, make specific and robust predictions about how and where organisms should live and what organisms should utilize. The role of functional morphology is often an under-appreciated parameter of these models. A more complete understanding of how anatomical features work to allow the organism to accomplish certain tasks has allowed us to revisit some of these ideas with a new perspective. We illustrate our view of this role for functional morphology in ecology by considering the issue of specialization: we attempt to align several definitions of specialization based upon shared ecological and evolutionary principles, and we summarize theoretical predictions regarding why an organism might specialize. Kinematic studies of prey capture in several types of fishes are explored with regard to the potential ecological and evolutionary consequences of specialization, most notably in the area of trade-offs. We suggest that a functional morphological perspective can increase our understanding of the ecological concepts of specialization and it consequences. The kinds of data that functional morphologists collect can help us to quantify organismal performance associated with specialization and the union of functional morphology with ecology can help us to better understand not just how but why organisms interact in the manner that they do.

The population dynamics of Helicobacter pylori during colonization in an infected animal host provide a quantifiable experimental model of in vivo microbial phenotype evolution. Phenotype variability in H. pylori populations can be typed as polymorphic expression of Lewis antigens on their cell surfaces. The high mutational frequency of H. pylori for Lewis expression provides substrate for differential selection by the host. Experimental challenge and successful colonization of mice and gerbils allows tracking of H. pylori phenotype variability from the initial inoculation to the ultimate establishment of a quasispecies. Colonization data provide a quantitative experimental model of phenotype evolution in a relatively large population (> [10.sup.4] individuals) over a relatively long evolutionary time scale (> [10.sup.3] generations). A mathematical model is developed to interpret the data in terms of the dynamic processes occuring during colonization. The mathematical model distinguishes the roles of selection and mutation; quantifies the effects of initial phenotype diversity, mutational frequency, and selective advantage; and applies generally to phenotype evolution in biological populations.

An overview is presented on the evolution of gibbon songs, from duet songs to solo singing. The shift from duet to solo may be attributed to a separation into female-specific and male-specific song parts, which may have then led to a separation between duetting and non-duetting species.

The many types of infections that exist as they relate to evolution of hybrid incompatibility in segmented viruses are discussed. Mathematical and computer models of the processes that influence hybrid incompatibility between diverging strains are presented. Multiplicity of infection is seen to be the key factor.

Freshwater galaxiid fishes (Osmeriformes: Galaxiidae) have been studied relative to clade formation and marine life-history phase loss. Speciation of the fishes is partly an incidental phenomenon caused by switches from diadromous to nonmigratory strategies. Much of the later nonmigratory diversity is monophyletic. Divergence between Tasmanian and New Zealand G. brevipinis supports marine dispersal rather than vicariance as the main biogeographic mechanism intercontinentally.

Drosophila pseudoobscura and D. persimilis have been studied relative to backcross hybrid males and the genetics of reproductive isolation and potential for gene exchange in them. It appear gene flow between the two species via hybrid males may be possible at loci spread across much of the autosomes.

Genetics of species differences have been studied by looking at courtship songs of Drosophila pseudoobscura and D. persimilis. The genetic basis of the difference is examined in two courtship song elements, interpulse interval and intrpulse frequency using 15 molecular markers. Song differences were associated with at least two or three genomic regions. Interpulse interval is strongly associated with mating success to D. pseudoobscura females, but intrapulese frequency is associated with mating success to D. persimilis females. Implications are discussed.

Little evidence was found for sympatric speciation in island birds based on a search for endemic congeneric species on isolated ocean islands. Of 46 islands and small archipelagos where at least one species of endemic land bird was found, seven paris of endemic congeners, excluding flightless rails, were found. Four pairs of the seven are potentially sister species. Three of the four have always been thought to come from double invasion from a mainland source. The remaining pair may have speciated allopatrically on a small archipelago.

Evolution of abdominal pigmentation differences have been studied across species in Drosophila dunni. Existence of a cline was confirmed using discriminant analysis. Quantitative measure of pigmentation was found to distinguish each of the species with singular efficacy. Natural selection is shown to have caused overall intensity of pigmentation among the northernmost species of the cline to converge.

Global phylogeography of a cryptic copepod species complex is discussed with consideration of reproductive isolation between genetically populations that are genetically close. To find levels of genetic differentiation among populations of the species a phylogenetic approach has been used. Interpopulation crosses were carried out to evaluate reproductive compatibility. A polytomy of very divergent clades was seen using phylogenetic analysis.

Conspecific sperm precedence (CSP) and its mechanism in Drosophila are discussed. When a Drosophila simulans female mates with both a D. simulans male and D. mauritiana male, the vastly more progeny are by D. simulans, the order of mating notwithstanding. Neither inviability of eggs fertilized by heterospecific sperm nor relative inviability of heterospecific larvae is the cause. CSP is apparently the result of a prefertilization obstacle to heterospecific sperm. Two independent barriers to heterospecific fertilization have been found; action of both depends on order of mating. They are sperm displacement and incapacitation and both involve the same mechanisms seen in second-male sperm precedence within species. Curing the D. mauritiana males of infection with the Wolbachia had no effect. The hypothesis now is that CSP is an evolutionary by-product of adaptations affecting sperm competition within species.

Analyses of morphology, RAPDs, and chloroplast DNA together have found spontaneous hybridization in the genus Chaenomeles. Analysis of diagnostic RAPD markers and of chloroplast DNA haplotypes supports the idea that spontaneous hybridization has taken place. It appears that a symmetrical, not unidirectional, introgression occurred between C. cathayensis and C. speciosa. RAPDs and morphologic characters showed concordant patterns of genetic relatedness among the offspring families.

We sequenced mitochondrial DNA (mtDNA) from cytochrome b (cyt b) and the control region (CR) for all five extant species in the genus Tragopan. We incorporated information on comparative patterns and rates of molecular evolution into phylogenetic analyses, using both a single-gene and a combined data approach. Sequence variability was distributed heterogeneously among the three domains of CR and the three codon positions of cyt b, but the two genes evolved at comparable rates, on average, and produced concordant topologies independent of the method used for phylogenetic reconstructions. Phylogenetic trees suggest that Tragopan includes two main evolutionary lineages grouping caboti-temminckii (clade A), and blythii-satyra (clade B). A shorter CR sequence from one museum sample could not consistently resolve the position of T. melanocephalus. The mtDNA phylogeny is better supported than alternative topologies inferred from morphological and behavioral traits and is compatible with a mechanism of allopatric speciation of Tragopan in two different episodes about 4 and 2 million years ago. In those periods, the vicariant events that might have fostered allopatric speciation of Tragopan are represented by landscape changes that affected the Indohimalayan region after the sudden rising of the Himalayas less then 8 million years ago, and by climatic fluctuations during the Pleistocene less than 2 million years ago.

Tests of Pleistocene speciation have been carried out in montane grasshoppers (genus Melanoplus) from the Sky Islands of Western North American. The results suggest rapidity of evolution of reproductive isolation may determine whether species divergences occurred during Pleistocene glaciations.

Genetic evidence has been found for assortative mating between 13-year cicadas and sympatric '17-year cicadas with 13-year life cycles.' It supports allochronic speciation theories. A previously unsuspected broad zone of overlap was found. Recent derivation of all northern 13-year cicadas from the 17-year ones seems to have occurred via life-cycle switching.