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Sister Species (sister + species)
Kinds of Sister Species Selected AbstractsCONSPECIFIC SPERM PRECEDENCE IN SISTER SPECIES OF DROSOPHILA WITH OVERLAPPING RANGESEVOLUTION, Issue 4 2004Audrey S. Chang Abstract Barriers to gene flow that act after mating but before fertilization are often overlooked in studies of reproductive isolation. Where species are sympatric, such "cryptic' isolating barriers may be important in maintaining species as distinct entities. Drosophilayakuba and its sister species D. santomea have overlapping ranges on the island of Sao Tome, off the coast of West Africa. Previous studies have shown that the two species are strongly sexually isolated. However, the degree of sexual isolation observed in the laboratory cannot explain the low frequency (,1%) of hybrids observed in nature. This study identifies two "cryptic" isolating barriers that may further reduce gene flow betweenD. yakuba andD. santomea where they are sympatric. First, noncompetitive gametic isolation has evolved between D. yakuba and D. santomea: heterospecific matings between the two species produce significantly fewer offspring than do conspecific matings. Second, conspecific sperm precedence (CSP) occurs when D. yakuba females mate with conspecific and heterospecific males. However, CSP is asymmetrical: D. santomea females do not show patterns of sperm usage consistent with CSP. Drosophila yakuba and D. santomea females also differ with respect to remating propensity after first mating with conspecific males. These results suggest that noncompetitive and competitive gametic isolating barriers may contribute to reproductive isolation between D. yakuba and D. santomea. [source] Speciation in fig pollinators and parasitesMOLECULAR ECOLOGY, Issue 8 2002George D. Weiblen Abstract Here we draw on phylogenies of figs and fig wasps to suggest how modes of speciation may be affected by interspecific interactions. Mutualists appear to have cospeciated with their hosts to a greater extent than parasites, which showed evidence of host shifting. However, we also repeatedly encountered a pattern not explained by either cospeciation or host switching. Sister species of fig parasites often attack the same host in sympatry, and differences in ovipositor length suggest that parasite speciation could result from divergence in the timing of oviposition with respect to fig development. These observations on fig parasites are consistent with a neglected model of sympatric speciation. [source] Dynamics of genome evolution in facultative symbionts of aphidsENVIRONMENTAL MICROBIOLOGY, Issue 8 2010Patrick H. Degnan Summary Aphids are sap-feeding insects that host a range of bacterial endosymbionts including the obligate, nutritional mutualist Buchnera plus several bacteria that are not required for host survival. Among the latter, ,Candidatus Regiella insecticola' and ,Candidatus Hamiltonella defensa' are found in pea aphids and other hosts and have been shown to protect aphids from natural enemies. We have sequenced almost the entire genome of R. insecticola (2.07 Mbp) and compared it with the recently published genome of H. defensa (2.11 Mbp). Despite being sister species the two genomes are highly rearranged and the genomes only have ,55% of genes in common. The functions encoded by the shared genes imply that the bacteria have similar metabolic capabilities, including only two essential amino acid biosynthetic pathways and active uptake mechanisms for the remaining eight, and similar capacities for host cell toxicity and invasion (type 3 secretion systems and RTX toxins). These observations, combined with high sequence divergence of orthologues, strongly suggest an ancient divergence after establishment of a symbiotic lifestyle. The divergence in gene sets and in genome architecture implies a history of rampant recombination and gene inactivation and the ongoing integration of mobile DNA (insertion sequence elements, prophage and plasmids). [source] Field Cricket Species Differences in the Temporal Patterns of Long-Distance Mate Attraction SignalsETHOLOGY, Issue 9 2006Susan M. Bertram We quantify variation in the temporal components of long-distance mate attraction signals produced by a North American field cricket, Gryllus rubens Scudder. Total signaling time, trilling bout duration, and hourly bout number exhibit high repeatability within individuals. Extensive variation exists across individuals: some males never signal while others signal for several hours each night; of the signalers, average trilling bout duration ranges from <1 min to well over an hour; some males produce only one trilling bout in an evening while others produce three bouts every 2 h. Body size, weight, wing morphology, and condition do not appear to explain the variation. We compare the temporal signaling components of G. rubens with its sister species, G. texensis. Although G. rubens produce slightly more trills per hour with slightly shorter trilling bout durations, the temporal components of these long-distance mate attraction signals are surprisingly similar across species. [source] Divergence between the Courtship Songs of the Field Crickets Gryllus texensis and Gryllus rubens (Orthoptera, Gryllidae)ETHOLOGY, Issue 12 2001Mark J. Fitzpatrick Acoustic mating signals are often important as both interspecific prezygotic isolating mechanisms and as sexually selected traits in intraspecific mate choice. Here, we investigate the potential for cricket courtship song to act as an isolating mechanism by assessing divergence between the courtship songs of Gryllus texensis and Gryllus rubens, two broadly sympatric cryptic sister species of field crickets with strong prezygotic isolation via the calling song and little or no postzygotic isolation. We found significant species-level differences in the courtship song, but the song has not diverged to the same extent as the calling song, and considerable overlap remains between these two species. Only two related courtship song characters are sufficiently distinct to play a possible role in prezygotic species isolation. [source] LATITUDINAL VARIATION IN SPECIATION MECHANISMS IN FROGSEVOLUTION, Issue 2 2010Xia Hua Speciation often has a strong geographical and environmental component, but the ecological factors that potentially underlie allopatric and parapatric speciation remain understudied. Two ecological mechanisms by which speciation may occur on geographic scales are allopatric speciation through niche conservatism and parapatric or allopatric speciation through niche divergence. A previous study on salamanders found a strong latitudinal pattern in the prevalence of these mechanisms, with niche conservatism dominating in temperate regions and niche divergence dominating in the tropics, and related this pattern to Janzen's hypothesis of greater climatic zonation between different elevations in the tropics. Here, we test for latitudinal patterns in speciation in a related but more diverse group of amphibians, the anurans. Using data from up to 79 sister-species pairs, we test for latitudinal variation in elevational and climatic overlap between sister species, and evaluate the frequency of speciation via niche conservatism versus niche divergence in relation to latitude. In contrast to salamanders, we find no tendency for greater niche divergence in the tropics or for greater niche conservatism in temperate regions. Although our results support the idea of greater climatic zonation in tropical regions, they show that this climatic pattern does not lead to straightforward relationships between speciation, latitude, and niche evolution. [source] COMPARATIVE GENOMIC AND POPULATION GENETIC ANALYSES INDICATE HIGHLY POROUS GENOMES AND HIGH LEVELS OF GENE FLOW BETWEEN DIVERGENT HELIANTHUS SPECIESEVOLUTION, Issue 8 2009Nolan C. Kane While speciation can be found in the presence of gene flow, it is not clear what impact this gene flow has on genome- and range-wide patterns of differentiation. Here we examine gene flow across the entire range of the common sunflower, H. annuus, its historically allopatric sister species H. argophyllus and a more distantly related, sympatric relative H. petiolaris. Analysis of genotypes at 26 microsatellite loci in 1015 individuals from across the range of the three species showed substantial introgression between geographically proximal populations of H. annuus and H. petiolaris, limited introgression between H. annuus and H. argophyllus, and essentially no gene flow between the allopatric pair, H. argophyllus and H. petiolaris. Analysis of sequence divergence levels among the three species in 1420 orthologs identified from EST databases identified a subset of loci showing extremely low divergence between H. annuus and H. petiolaris and extremely high divergence between the sister species H. annuus and H. argophyllus, consistent with introgression between H. annuus and H. petiolaris at these loci. Thus, at many loci, the allopatric sister species are more genetically divergent than the more distantly related sympatric species, which have exchanged genes across much of the genome while remaining morphologically and ecologically distinct. [source] ENVIRONMENTAL NICHE EQUIVALENCY VERSUS CONSERVATISM: QUANTITATIVE APPROACHES TO NICHE EVOLUTIONEVOLUTION, Issue 11 2008Dan L. Warren Environmental niche models, which are generated by combining species occurrence data with environmental GIS data layers, are increasingly used to answer fundamental questions about niche evolution, speciation, and the accumulation of ecological diversity within clades. The question of whether environmental niches are conserved over evolutionary time scales has attracted considerable attention, but often produced conflicting conclusions. This conflict, however, may result from differences in how niche similarity is measured and the specific null hypothesis being tested. We develop new methods for quantifying niche overlap that rely on a traditional ecological measure and a metric from mathematical statistics. We reexamine a classic study of niche conservatism between sister species in several groups of Mexican animals, and, for the first time, address alternative definitions of "niche conservatism" within a single framework using consistent methods. As expected, we find that environmental niches of sister species are more similar than expected under three distinct null hypotheses, but that they are rarely identical. We demonstrate how our measures can be used in phylogenetic comparative analyses by reexamining niche divergence in an adaptive radiation of Cuban anoles. Our results show that environmental niche overlap is closely tied to geographic overlap, but not to phylogenetic distances, suggesting that niche conservatism has not constrained local communities in this group to consist of closely related species. We suggest various randomization tests that may prove useful in other areas of ecology and evolutionary biology. [source] THE GEOGRAPHICAL PATTERN OF SPECIATION AND FLORAL DIVERSIFICATION IN THE NEOTROPICS: THE TRIBE SINNINGIEAE (GESNERIACEAE) AS A CASE STUDYEVOLUTION, Issue 7 2007Mathieu Perret The geographical pattern of speciation and the relationship between floral variation and species ranges were investigated in the tribe Sinningieae (Gesneriaceae), which is found mainly in the Atlantic forests of Brazil. Geographical distribution data recorded on a grid system of 0.5 × 0.5 degree intervals and a near-complete species-level phylogenetic tree of Sinningieae inferred from a simultaneous analysis of seven DNA regions were used to address the role of geographical isolation in speciation. Geographical range overlaps between sister lineages were measured across all nodes in the phylogenetic tree and analyzed in relation to relative ages estimated from branch lengths. Although there are several cases of species sympatry in Sinningieae, patterns of sympatry between sister taxa support the predominance of allopatric speciation. The pattern of sympatry between sister taxa is consistent with range shifts following allopatric speciation, except in one clade, in which the overlapping distribution of recent sister species indicates speciation within a restricted geographical area and involving changes in pollinators and habitats. The relationship between floral divergence and regional sympatry was also examined by analyzing floral contrasts, phenological overlap, and the degree of sympatry between sister clades. Morphological contrast between flowers is not increased in sympatry and phenological divergence is more apparent between allopatric clades than between sympatric clades. Therefore, our results failed to indicate a tendency for sympatric taxa to minimize morphological and phenological overlap (geographic exclusion and/or character displacement hypotheses). Instead, they point toward adaptation in phenology to local conditions and buildup of sympatries at random with respect to flower morphology. Additional studies at a lower geographical scale are needed to identify truely coexisting species and the components of their reproductive isolation. [source] THE PHYLOGENETIC PATTERN OF SPECIATION AND WING PATTERN CHANGE IN NEOTROPICAL ITHOMIA BUTTERFLIES (LEPIDOPTERA: NYMPHALIDAE)EVOLUTION, Issue 7 2006Chris D. Jiggins Abstract Species level phylogenetic hypotheses can be used to explore patterns of divergence and speciation. In the tropics, speciation is commonly attributed to either vicariance, perhaps within climate-induced forest refugia, or ecological speciation caused by niche adaptation. Mimetic butterflies have been used to identify forest refugia as well as in studies of ecological speciation, so they are ideal for discriminating between these two models. The genus Ithomia contains 24 species of warningly colored mimetic butterflies found in South and Central America, and here we use a phylogenetic hypothesis based on seven genes for 23 species to investigate speciation in this group. The history of wing color pattern evolution in the genus was reconstructed using both parsimony and likelihood. The ancestral pattern for the group was almost certainly a transparent butterfly, and there is strong evidence for convergent evolution due to mimicry. A punctuationist model of pattern evolution was a significantly better fit to the data than a gradualist model, demonstrating that pattern changes above the species level were associated with cladogenesis and supporting a model of ecological speciation driven by mimicry adaptation. However, there was only one case of sister species unambiguously differing in pattern, suggesting that some recent speciation events have occurred without pattern shifts. The pattern of geographic overlap between clades over time shows that closely related species are mostly sympatric or, in one case, parapatric. This is consistent with modes of speciation with ongoing gene flow, although rapid range changes following allopatric speciation could give a similar pattern. Patterns of lineage accumulation through time differed significantly from that expected at random, and show that most of the extant species were present by the beginning of the Pleistocene at the latest. Hence Pleistocene refugia are unlikely to have played a major role in Ithomia diversification. [source] PHYLOGEOGRAPHY AND DEMOGRAPHY OF SYMPATRIC SISTER SURFPERCH SPECIES, EMBIOTOCA JACKSONI AND E. LATERALIS ALONG THE CALIFORNIA COAST: HISTORICAL VERSUS ECOLOGICAL FACTORSEVOLUTION, Issue 2 2005Glacomo Bernardi Abstract With 18 closely related endemic species that radiated in a diversity of ecological niches, the California surfperches (Embiotocidae) species flock is a good candidate for the study of sympatric speciation. Resource partitioninghas been suggested as an important driving force in the radiation of the surfperch family. Within the family, two congeneric sister species, Embiotoca jacksoni and E. lateralis, are known to compete strongly for a preferred singleood resource and may be used as a model of ecological interactions for the family. Along the California coast, the distribution of the two species differs. Embiotoca jacksoni has a continuous range, whereas E. lateralis shows a disjunction with a distribution gap in the Southern California Bight. Two hypotheses may explain this disjunct distribution. Ecological competition may have displaced E. lateralis in favor of E. jacksoni. Alternatively, a common vicariant event may have separated the species into northern and southern populations, followed by secondary contactin E. jacksoni but not in E. lateralis. The two hypotheses predict different phylogeographic and demographic signatures. Using a combined phylogeographic and coalescent approach based on mitochondrial control region data, we show that vicariance can only account for a portion of the observed divergences. Our results are compatible with a significant role played by ecological competition in the southern range of the species. [source] EVOLUTION OF SUBTERRANEAN DIVING BEETLES (COLEOPTERA: DYTISCIDAE HYDROPORINI, BIDESSINI) IN THE ARID ZONE OF AUSTRALIAEVOLUTION, Issue 12 2003Remko Leys Abstract Calcrete aquifers in arid inland Australia have recently been found to contain the world's most diverse assemblage of subterranean diving beetles (Coleoptera: Dytiscidae). In this study we test whether the adaptive shift hypothesis (ASH) or the climatic relict hypothesis (CRH) is the most likely mode of evolution for the Australian subterranean diving beetles by using a phylogeny based on two sequenced fragments of mitochondrial genes (CO1 and 16S-tRNA-ND1) and linearized using a relaxed molecular clock method. Most individual calcrete aquifers contain an assemblage of diving beetle species of distantly related lineages and/or a single pair of sister species that significantly differ in size and morphology. Evolutionary transitions from surface to subterranean life took place in a relatively small time frame between nine and four million years ago. Most of the variation in divergence times of the sympatric sister species is explained by the variation in latitude of the localities, which correlates with the onset of aridity from the north to the south and with an aridity maximum in the Early Pliocene (five mya). We conclude that individual calcrete aquifers were colonized by several distantly related diving beetle lineages. Several lines of evidence from molecular clock analyses support the CRH, indicating that all evolutionary transitions took place during the Late Miocene and Early Pliocene as a result of aridification. [source] THE SHAPES OF NEUTRAL GENE GENEALOGIES IN TWO SPECIES: PROBABILITIES OF MONOPHYLY, PARAPHYLY, AND POLYPHYLY IN A COALESCENT MODELEVOLUTION, Issue 7 2003Noah A. Rosenberg Abstract., The genealogies of samples of orthologous regions from multiple species can be classified by their shapes. Using a neutral coalescent model of two species, I give exact probabilities of each of four possible genealogical shapes: reciprocal monophyly, two types of paraphyly, and polyphyly. After the divergence that forms two species, each of which has population size N, polyphyly is the most likely genealogical shape for the lineages of the two species. At , 1.300N generations after divergence, paraphyly becomes most likely, and reciprocal monophyly becomes most likely at ,1.665N generations. For a given species, the time at which 99% of its loci acquire monophyletic genealogies is ,5.298N generations, assuming all loci in its sister species are monophyletic. The probability that all lineages of two species are reciprocally monophyletic given that a sample from the two species has a reciprocally monophyletic genealogy increases rapidly with sample size, as does the probability that the most recent common ancestor (MRCA) for a sample is also the MRCA for all lineages from the two species. The results have potential applications for the testing of evolutionary hypotheses. [source] GENETIC EVIDENCE ON THE DEMOGRAPHY OF SPECIATION IN ALLOPATRIC DOLPHIN SPECIESEVOLUTION, Issue 4 2002Matthew P. Hare Abstract Under a neutral model, the stochastic lineage sorting that leads to gene monophyly proceeds slowly in large populations. Therefore, in many recent species with large population size, the genome will have mixed support for monophyly unless historical bottlenecks have accelerated coalescence. We use genealogical patterns in mitochondrial DNA and in introns of four nuclear loci to test for historical bottlenecks during the speciation and divergence of two temperate Lagenorhynchus dolphin species isolated by tropical Pacific waters (an antitropical distribution). Despite distinct morphologies, foraging behaviors, and mitochondrial DNAs, these dolphin species are polyphyletic at all four nuclear loci. The abundance of shared polymorphisms between these sister taxa is most consistent with the maintenance of large effective population sizes (5.09 × 104 to 10.9 × 104) during 0.74,1.05 million years of divergence. A variety of population size histories are possible, however. We used gene tree coalescent probabilities to explore the rejection region for historical bottlenecks of different intensity given best estimates of effective population size under a strict isolation model of divergence. In L. obliquidens the data are incompatible with a colonization propagule of an effective size of 10 or fewer individuals. Although the ability to reject less extreme historical bottlenecks will require data from additional loci, the intermixed genealogical patterns observed between these dolphin sister species are highly probable only under an extended history of large population size. If similar demographic histories are inferred for other marine antitropical taxa, a parsimonious model for the Pleistocene origin of these distributions would not involve rare breaches of a constant dispersal barrier by small colonization propagules. Instead, a history of large population size in L. obliquidens and L. obscurus contributes to growing biological and environmental evidence that the equatorial barrier became permeable during glacial/interglacial cycles, leading to vicariant isolation of antitropical populations. [source] PERSPECTIVE: GENE DIVERGENCE, POPULATION DIVERGENCE, AND THE VARIANCE IN COALESCENCE TIME IN PHYLOGEOGRAPHIC STUDIESEVOLUTION, Issue 6 2000ScottV. Abstract Molecular methods as applied to the biogeography of single species (phylogeography) or multiple codistributed species (comparative phylogeography) have been productively and extensively used to elucidate common historical features in the diversification of the Earth's biota. However, only recently have methods for estimating population divergence times or their confidence limits while taking into account the critical effects of genetic polymorphism in ancestral species become available, and earlier methods for doing so are underutilized. We review models that address the crucial distinction between the gene divergence, the parameter that is typically recovered in molecular phylogeographic studies, and the population divergence, which is in most cases the parameter of interest and will almost always postdate the gene divergence. Assuming that population sizes of ancestral species are distributed similarly to those of extant species, we show that phylogeographic studies in vertebrates suggest that divergence of alleles in ancestral species can comprise from less than 10% to over 50% of the total divergence between sister species, suggesting that the problem of ancestral polymorphism in dating population divergence can be substantial. The variance in the number of substitutions (among loci for a given species or among species for a given gene) resulting from the stochastic nature of DNA change is generally smaller than the variance due to substitutions along allelic lines whose coalescence times vary due to genetic drift in the ancestral population. Whereas the former variance can be reduced by further DNA sequencing at a single locus, the latter cannot. Contrary to phylogeographic intuition, dating population divergence times when allelic lines have achieved reciprocal monophyly is in some ways more challenging than when allelic lines have not achieved monophyly, because in the former case critical data on ancestral population size provided by residual ancestral polymorphism is lost. In the former case differences in coalescence time between species pairs can in principle be explained entirely by differences in ancestral population size without resorting to explanations involving differences in divergence time. Furthermore, the confidence limits on population divergence times are severely underestimated when those for number of substitutions per site in the DNA sequences examined are used as a proxy. This uncertainty highlights the importance of multilocus data in estimating population divergence times; multilocus data can in principle distinguish differences in coalescence time (T) resulting from differences in population divergence time and differences in T due to differences in ancestral population sizes and will reduce the confidence limits on the estimates. We analyze the contribution of ancestral population size (,) to T and the effect of uncertainty in , on estimates of population divergence (,) for single loci under reciprocal monophyly using a simple Bayesian extension of Takahata and Satta's and Yang's recent coalescent methods. The confidence limits on , decrease when the range over which ancestral population size , is assumed to be distributed decreases and when increases; they generally exclude zero when /(4Ne) > 1. We also apply a maximum-likelihood method to several single and multilocus data sets. With multilocus data, the criterion for excluding = 0 is roughly that l/(4Ne)> 1, where l is the number of loci. Our analyses corroborate recent suggestions that increasing the number of loci is critical to decreasing the uncertainty in estimates of population divergence time. [source] Metschnikowia arizonensis and Metschnikowia dekortorum, two new large-spored yeast species associated with floricolous beetlesFEMS YEAST RESEARCH, Issue 2 2002Marc-André Lachance Abstract Two new haplontic heterothallic species of Metschnikowia were discovered in flowers and associated beetles. Metschnikowia arizonensis was recovered from flowers of cholla cactus (Opuntia echinocarpa) and a specimen of Carpophilus sp. (Coleoptera: Nitidulidae) found in these flowers, in Arizona. Metschnikowia dekortorum was isolated in specimens of the nitidulid beetle Conotelus sp. captured in flowers of two species of Ipomoea in northwestern Guanacaste Province, Costa Rica. The sexual cycle of these yeasts is typical of the large-spored Metschnikowia species, but the asci and spores are intermediate in size between these and other members of the genus. The physiology is consistent with that of most Metschnikowia species except that both species fail to utilize lysine as sole nitrogen source. Also, M. arizonensis utilizes fewer carbon compounds than most species and exhibits considerable variability among strains at this level. Partial ribosomal DNA large-subunit (D1/D2) sequences suggest that M. arizonensis and M. dekortorum are moderately related sister species whose positions are intermediate between the large-spored species Metschnikowia and Metschnikowia hibisci. The type cultures are: M. arizonensis, strains UWO(PS)99-103.3.1=CBS 9064=NRRL Y-27427 (h+, holotype) and UWO(PS)99-103.4=CBS 9065=NRRL Y-27428 (h,, isotype); and M. dekortorum, strains UWO(PS)01-142b3=CBS 9063=NRRL Y-27429 (h+, holotype) and UWO(PS)01-138a3=CBS 9062=NRRL Y-27430 (h,, isotype). [source] Adaptations of an insect to a novel host plant: a phylogenetic approachFUNCTIONAL ECOLOGY, Issue 3 2006A. J. GASSMANN Summary 1The importance of behavioural vs physiological adaptations in the evolution of host associations by herbivorous insects is largely unknown. 2We compared sister species of beetles, one of which, Ophraella slobodkini, feeds on the lineage's ancestral host, Ambrosia artemisiifolia, while O. notulata has shifted to a novel host, Iva frutescens. Assuming O. slobodkini represents the features of the Ambrosia -feeding ancestor, we asked if behavioural and physiological barriers to utilizing Iva existed and if adaptation to these barriers occurred. We also tested for trade-offs between use of novel and ancestral hosts by O. notulata. 3We found evidence that the ancestor of O. notulata would have been deterred from feeding on Iva and suffered lower conversion efficiency. 4Ophraella notulata appears to have adapted behaviourally by increasing consumption of Iva, but we did not detect a significant increase in its physiological capacity to use Iva. Additionally, the switch to Iva by O. notulata did not reduce its physiological capacity to use the ancestral host, Ambrosia. 5Our results suggest that novel host associations may arise from behavioural adaptations, with physiological adaptations a secondary result of behavioural changes. We discuss implications for hypotheses of host shifts and the evolution of specialization. [source] Geographical range size heritability: what do neutral models with different modes of speciation predict?GLOBAL ECOLOGY, Issue 3 2007David Mouillot ABSTRACT Aim, Phylogenetic conservatism or heritability of the geographical range sizes of species (i.e. the tendency for closely related species to share similar range sizes) has been predicted to occur because of the strong phylogenetic conservatism of niche traits. However, the extent of such heritability in range size is disputed and the role of biology in shaping this attribute remains unclear. Here, we investigate the level of heritability of geographical range sizes that is generated from neutral models assuming no biological differences between species. Methods, We used three different neutral models, which differ in their speciation mode, to simulate the life-history of 250,000 individuals in a square lattice of 50 × 50 cells. These individuals can speciate, reproduce, migrate and die in the metacommunity according to stochastic events. We ran each model for 3000 steps and recorded the range size of each species at each step. The heritability of geographical range size was assessed using an asymmetry coefficient between range sizes of sister species and using the coefficient of correlation between the range sizes of ancestors and their descendants. Results, Our results demonstrated the ability of neutral models to mimic some important observed patterns in the heritability of geographical range size. Consistently, sister species exhibited higher asymmetry in range sizes than expected by chance, and correlations between the range sizes of ancestor,descendant species pairs, although often weak, were almost invariably positive. Main conclusions, Our findings suggest that, even without any biological trait differences, statistically significant heritability in the geographical range sizes of species can be found. This heritability is weaker than that observed in some empirical studies, but suggests that even here a substantial component of heritability may not necessarily be associated with niche conservatism. We also conclude that both present-day and fossil data sets may provide similar information on the heritability of the geographical range sizes of species, while the omission of rare species will tend to overestimate this heritability. [source] Using presence signs to discriminate between similar speciesINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 3 2009Sara M. SANTOS Abstract The Lusitanian and the Mediterranean pine voles (Microtus lusitanicus Gerbe, 1879 and Microtus duodecimcostatus de Selys-Longchamps, 1839) are fossorial sister species and have an allopatric pattern of distribution in Portugal, which includes a potential sympatry area in the centre of the country. The present study aimed to determine the validity of using presence signs in the field for discrimination of the two species in an area of sympatry (Northern Alentejo) and the characteristics that achieve the best classification accuracy. A total of 175 trapping plots were sampled across the study area. Prior to the set up of traps, ten presence signs were randomly selected for measurements of four variables: proportion of soil mounds, mean diameter of mounds, proportion of burrow openings and mean diameter of burrow openings. On the basis of a classification tree analysis, results showed that presence signs can be used to discriminate plots inhabited by one or the other species in the studied sympatry area. The characteristic that most accurately enables species identification is the proportion of burrow openings: for every ten presence signs found in a plot, if more than eight have an opening, then it is inhabited by M. lusitanicus (i.e. mostly burrow openings with few or no mounds present); if eight or fewer have an opening, M. duodecimcostatus is present (i.e. mostly mounds with few or no burrow openings). [source] The role of competition in adaptive radiation: a field study on sequentially ovipositing host-specific seed predatorsJOURNAL OF ANIMAL ECOLOGY, Issue 1 2004Laurence Després Summary 1We propose an alternative model to the host-shifting model of sympatric speciation in plant,insect systems. The role of competition in driving ecological adaptive radiation was evaluated in a seed predator exploiting a single host-plant species. Sympatric speciation may occur through disruptive selection on oviposition timing if this shift decreases competition among larvae feeding on seeds. 2The globeflower fly Chiastocheta presents a unique case of adaptive radiation, with at least six sister species co-developing in fruits of Trollius europaeus. These species all feed on seeds, and differ in their oviposition timing, one species ovipositing in 1-day-old flowers (early species), while all the other species sequentially oviposit throughout the flower life span (late species). We evaluated the impact of conspecific and heterospecific larvae on larval installation success, and on larval fresh mass and area, for early and late species, in natural conditions. 3None of the three larval traits measured was correlated with fruit size, and no fruit lost all seeds to predation, suggesting that seed availability was not a limiting factor for larval development. 4Our results show strong intraspecific competition among early larvae for larval installation, and among late larvae for larval mass. By contrast, larval competition between species was weak. These results are consistent with the hypothesis that shifts in oviposition promoted rapid radiation in globeflower flies by lowering competition among larvae. [source] Eastern Beringian biogeography: historical and spatial genetic structure of singing voles in AlaskaJOURNAL OF BIOGEOGRAPHY, Issue 8 2010Marcelo Weksler Abstract Aim Pleistocene climatic cycles have left marked signatures in the spatial and historical genetic structure of high-latitude organisms. We examine the mitochondrial (cytochrome b) genetic structure of the singing vole, Microtus miurus (Rodentia: Cricetidae: Arvicolinae), a member of the Pleistocene Beringian fauna, and of the insular vole, Microtus abbreviatus, its putative sister species found only on the St Matthew Archipelago. We reconstruct the phylogenetic and phylogeographical structure of these taxa, characterize their geographical partitioning and date coalescent and cladogenetic events in these species. Finally, we compare the recovered results with the phylogenetic, coalescent and spatial genetic patterns of other eastern Beringian mammals and high-latitude arvicoline rodents. Location Continental Alaska (alpine and arctic tundra) and the St Matthew Archipelago (Bering Sea). Methods We generated and analysed cytochrome b sequences of 97 singing and insular voles (M. miurus and M. abbreviatus) from Alaska. Deep evolutionary structure was inferred by phylogenetic analysis using parsimony, maximum likelihood and Bayesian approaches; the geographical structure of genetic diversity was assessed using analysis of molecular variance and network analysis; ages of cladogenetic and coalescent events were estimated using a relaxed molecular clock model with Bayesian approximation. Results Regional nucleotide diversity in singing voles is higher than in other high-latitude arvicoline species, but intra-population diversity is within the observed range of values for arvicolines. Microtus abbreviatus specimens are phylogenetically nested within M. miurus. Molecular divergence date estimates indicate that current genetic diversity was formed in the last glacial (Wisconsinan) and previous interglacial (Sangamonian) periods, with the exception of a Middle Pleistocene split found between samples collected in the Wrangell Mountains region and all other singing vole samples. Main conclusions High levels of phylogenetic and spatial structure are observed among analysed populations. This pattern is consistent with that expected for a taxon with a long history in Beringia. The spatial genetic structure of continental singing voles differs in its northern and southern ranges, possibly reflecting differences in habitat distribution between arctic and alpine tundra. Our phylogenetic results support the taxonomic inclusion of M. miurus in its senior synonym, M. abbreviatus. [source] Contrasting phylogeographies inferred for the two alpine sister species Cardamine resedifolia and C. alpina (Brassicaceae)JOURNAL OF BIOGEOGRAPHY, Issue 1 2009Judita Lihová Abstract Aim, We use Cardamine alpina and C. resedifolia as models to address the detailed history of disjunctions in the European alpine system. These species grow on siliceous bedrock: C. alpina in the Alps and Pyrenees, and C. resedifolia in several mountain ranges from the Sierra Nevada to the Balkans. We explore differentiation among their disjunct populations as well as within the contiguous Alpine and Pyrenean ranges, and compare the phylogeographical histories of these diploid sister species. We also include samples of the closely related, arctic diploid C. bellidifolia in order to explore its origin and post-glacial establishment. Location, European alpine system, Norway and Iceland. Methods, We employed amplified fragment length polymorphisms (AFLPs). AFLP data were analysed using principal coordinates analysis, neighbour joining and Bayesian clustering, and measures of diversity and differentiation were computed. Results, For the snow-bed species C. alpina (27 populations, 203 plants) we resolved two strongly divergent lineages, corresponding to the Alps and the Pyrenees. Although multiple glacial refugia were invoked in the Pyrenees, we inferred only a single one in the Maritime Alps , from which rapid post-glacial colonization of the entire Alps occurred, accompanied by a strong founder effect. For C. resedifolia (33 populations, 247 plants), which has a broader ecological amplitude and a wider distribution, the genetic structuring was rather weak and did not correspond to the main geographical disjunctions. This species consists of two widespread and largely sympatric main genetic groups (one of them subdivided into four geographically more restricted groups), and frequent secondary contacts exist between them. Main conclusions, The conspicuously different histories of these two sister species are likely to be associated with their different ecologies. The more abundant habitats available for C. resedifolia may have increased the probability of its gradual migration during colder periods and also of successful establishment after long-distance dispersal, whereas C. alpina has been restricted by its dependence on snow-beds. Surprisingly, the arctic C. bellidifolia formed a very divergent lineage with little variation, contradicting a scenario of recent, post-glacial migration from the Alps or Pyrenees. [source] Atlantic reef fish biogeography and evolutionJOURNAL OF BIOGEOGRAPHY, Issue 1 2008S. R. Floeter Abstract Aim, To understand why and when areas of endemism (provinces) of the tropical Atlantic Ocean were formed, how they relate to each other, and what processes have contributed to faunal enrichment. Location, Atlantic Ocean. Methods, The distributions of 2605 species of reef fishes were compiled for 25 areas of the Atlantic and southern Africa. Maximum-parsimony and distance analyses were employed to investigate biogeographical relationships among those areas. A collection of 26 phylogenies of various Atlantic reef fish taxa was used to assess patterns of origin and diversification relative to evolutionary scenarios based on spatio-temporal sequences of species splitting produced by geological and palaeoceanographic events. We present data on faunal (species and genera) richness, endemism patterns, diversity buildup (i.e. speciation processes), and evaluate the operation of the main biogeographical barriers and/or filters. Results, Phylogenetic (proportion of sister species) and distributional (number of shared species) patterns are generally concordant with recognized biogeographical provinces in the Atlantic. The highly uneven distribution of species in certain genera appears to be related to their origin, with highest species richness in areas with the greatest phylogenetic depth. Diversity buildup in Atlantic reef fishes involved (1) diversification within each province, (2) isolation as a result of biogeographical barriers, and (3) stochastic accretion by means of dispersal between provinces. The timing of divergence events is not concordant among taxonomic groups. The three soft (non-terrestrial) inter-regional barriers (mid-Atlantic, Amazon, and Benguela) clearly act as ,filters' by restricting dispersal but at the same time allowing occasional crossings that apparently lead to the establishment of new populations and species. Fluctuations in the effectiveness of the filters, combined with ecological differences among provinces, apparently provide a mechanism for much of the recent diversification of reef fishes in the Atlantic. Main conclusions, Our data set indicates that both historical events (e.g. Tethys closure) and relatively recent dispersal (with or without further speciation) have had a strong influence on Atlantic tropical marine biodiversity and have contributed to the biogeographical patterns we observe today; however, examples of the latter process outnumber those of the former. [source] Historical biogeography and distribution of the freshwater cyclopine copepods (Copepoda, Cyclopoida, Cyclopinae) of the Yucatan Peninsula, MexicoJOURNAL OF BIOGEOGRAPHY, Issue 7 2004Eduardo Suárez-Morales Abstract Aim, To determine and analyse the distribution of the freshwater cyclopine copepod fauna of the Yucatan Peninsula (YP) and its relationship with the geological and climatic history of this Neotropical karstic zone. Location, The Yucatan Peninsula, Mexico. Methods, Plotting of georeferenced sites, analysis of local and regional geological and climatic history, analysis and comparison of regional and local faunistic records. Results, Distinct dispersal and/or vicariant processes seem to be linked to the current distributions of the seven genera known in the YP. In general, the endemic hypogean or benthic crevicular forms (i.e. Diacyclops chakan, D. puuc and Mesocyclops chaci), derived from epigean, tropical, widely distributed forms (some of them South American) may have been among the earliest colonizers of the subterranean habitats in the YP. The distribution of these and other endemic forms seem to be related to the Holocene dry periods that desiccated the largest bodies of water and isolated local populations of different species. These vicariant processes resulted in forms with restricted distributional areas; some of these formed sister species that speciated in geographically close localities but related to a common identifiable ancestor. Overall, the processes of cyclopine colonization of the YP show the influence of the South American fauna, as the closest relatives of some species endemic to the YP are South American forms; the Nearctic influence is low. The cyclopine fauna of the YP is formed by a mixture of Nearctic-derived (species of Acanthocyclops), Neotropical (i.e. M. edax, M. longisetus, A. panamensis, Thermocyclops inversus and T. tenuis), and epigean and hypogean endemic forms. The highly dynamic geomorphology of the YP and the recent climatic changes in the Holocene define the YP as a peculiar subregion that harbours a diverse fauna of cyclopine copepods with a high endemism. Main conclusion, The current distribution of cyclopine copepods reflects relatively recent, post-Pliocene biogeographical patterns; probably older patterns are involved as well. The eastern coast of the Yucatan is the most recently colonized by cyclopine copepods. Most of the genera are linked with South American forms, and the Nearctic influence is weakly represented. This group has no marine relatives, but there is evidence of vicariant events involving cave-dwelling forms. [source] Differentiation of morphology, genetics and electric signals in a region of sympatry between sister species of African electric fish (Mormyridae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2008S. LAVOUÉ Abstract Mormyrid fishes produce and sense weak electric organ discharges (EODs) for object detection and communication, and they have been increasingly recognized as useful model organisms for studying signal evolution and speciation. EOD waveform variation can provide important clues to sympatric species boundaries between otherwise similar or morphologically cryptic forms. Endemic to the watersheds of Gabon (Central Africa), Ivindomyrus marchei and Ivindomyrus opdenboschi are morphologically similar to one another. Using morphometric, electrophysiological and molecular characters [cytochrome b sequences and amplified fragment length polymorphism (AFLP) genotypes], we investigated to what extent these nominal mormyrid species have diverged into biological species. Our sampling covered the known distribution of each species with a focus on the Ivindo River, where the two taxa co-occur. An overall pattern of congruence among datasets suggests that I. opdenboschi and I. marchei are mostly distinct. Electric signal analysis showed that EODs of I. opdenboschi tend to have a smaller initial head-positive peak than those of I. marchei, and they often possess a small third waveform peak that is typically absent in EODs of I. marchei. Analysis of sympatric I. opdenboschi and I. marchei populations revealed slight, but significant, genetic partitioning between populations based on AFLP data (FST , 0.04). Taken separately, however, none of the characters we evaluated allowed us to discriminate two completely distinct or monophyletic groups. Lack of robust separation on the basis of any single character set may be a consequence of incomplete lineage sorting due to recent ancestry and/or introgressive hybridization. Incongruence between genetic datasets in one individual, which exhibited a mitochondrial haplotype characteristic of I. marchei but nevertheless fell within a genetic cluster of I. opdenboschi based on AFLP genotypes, suggests that a low level of recent hybridization may also be contributing to patterns of character variation in sympatry. Nevertheless, despite less than perfect separability based on any one dataset and inconclusive evidence for complete reproductive isolation between them in the Ivindo River, we find sufficient evidence to support the existence of two distinctive species, I. opdenboschi and I. marchei, even if not ,biological species' in the Mayrian sense. [source] Mimicry and the evolution of premating isolation in Heliconius melpomene LinnaeusJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2004C. D. Jiggins Abstract Ecological divergence can cause speciation if adaptive traits have pleiotropic effects on mate choice. In Heliconius butterflies, mimetic patterns play a role in mate detection between sister species, as well as signalling to predators. Here we show that male butterflies from four recently diverged parapatric populations of Heliconius melpomene are more likely to approach and court their own colour patterns as compared with those of other races. A few exceptions, where males were more attracted to patterns other than their own, suggest that some mimetic patterns are sub-optimal in mate choice. Genotype frequencies in hybrid zones between races of H. melpomene suggest that mating is random, so reinforcement is unlikely to have played a role in intra-specific divergence. In summary, co-evolved divergence of colour pattern and mate preference occurs rapidly and is likely the first step in Heliconius speciation. [source] Continental speciation in the tropics: contrasting biogeographic patterns of divergence in the Uroplatus leaf-tailed gecko radiation of MadagascarJOURNAL OF ZOOLOGY, Issue 4 2008C. J. Raxworthy Abstract A fundamental expectation of vicariance biogeography is for contemporary cladogenesis to produce spatial congruence between speciating sympatric clades. The Uroplatus leaf-tailed geckos represent one of most spectacular reptile radiations endemic to the continental island of Madagascar, and thus serve as an excellent group for examining patterns of continental speciation within this large and comparatively isolated tropical system. Here we present the first phylogeny that includes complete taxonomic sampling for the group, and is based on morphology and molecular (mitochondrial and nuclear DNA) data. This study includes all described species, and we also include data for eight new species. We find novel outgroup relationships for Uroplatus and find strongest support for Paroedura as its sister taxon. Uroplatus is estimated to have initially diverged during the mid-Tertiary in Madagascar, and includes two major speciose radiations exhibiting extensive spatial overlap and estimated contemporary periods of speciation. All sister species are either allopatric or parapatric. However, we found no evidence for biogeographic congruence between these sympatric clades, and dispersal events are prevalent in the dispersal,vicariance biogeographic analyses, which we estimate to date to the Miocene. One sister-species pair exhibits isolated distributions that we interpret as biogeographic relicts, and two sister-species pairs have parapatric distributions separated by elevation. Integrating ecological niche models with our phylogenetic results finds both conserved and divergent niches between sister species. We also found substantial intra-specific genetic variation, and for the three most widespread species, poor intra-specific predictive performance for ecological niche models across the latitudinal span of Madagascar. These latter results indicate the potential for intra-specific niche specialization along environmental gradients, and more generally, this study suggests a complex speciation history for this group in Madagascar, which appears to include multiple speciation processes. [source] GENETIC VARIATION OF KOGIA SPP.MARINE MAMMAL SCIENCE, Issue 4 2005WITH PRELIMINARY EVIDENCE FOR TWO SPECIES OF KOGIA SIMA Abstract Concordance between mitochondrial DNA (mtDNA) markers and morphologically based species identifications was examined for the two currently recognized Kogia species. We sequenced 406 base pairs of the control region and 398 base pairs of the cytochrome b gene from 108 Kogia breviceps and 47 K. sima samples. As expecred, the two sister species were reciprocally monophyletic to each other in phylogenetic reconstructions, but within K. sima, we unexpectedly observed another reciprocally monophyletic relationship. The two K. sima clades resolved were phylogeographically concordant with all of the haplotypes in one clade observed solely among specimens sampled from the Atlantic Ocean and with those in the other clade observed solely among specimens sampled from the Indo-Pacific Ocean. These apparently allopatric clades were observed in all phylogenetic reconstructions using the maximum parsimony, maximum likelihood, and neighborjoining algorithms, with the mtDNA gene sequences analyzed separately and combined. The nucleotide diversity for the combined gene sequence haplotypes of the two K. sima clades resolved in our analyses was 0.58% and 1.03% for the Atlantic and Indo-Pacific, respectively, whereas for the two recognized sister species, nucleotide diversity was 1.65% and 4.02% for K. breviceps and K. sima, respectively. The combined gene sequence haplotypes have accumulated 44 fixed base pair differences between the two K. sima clades compared to 20 fixed base pair differences between the two recognized sister species. Although our results are consistent with species-level differences between the two K. sima clades, recognition of a third Kogia species awaits supporting evidence that these two apparently allopatric clades represent reproductively isolated groups of animals. [source] Ficus racemosa is pollinated by a single population of a single agaonid wasp species in continental South-East AsiaMOLECULAR ECOLOGY, Issue 13 2010N. KOBMOO Abstract High specificity in the Ficus -agaonid wasp mutualism has lead to the assumption of a mostly ,one-to-one' relationship, albeit with some exceptions. This view has been challenged by new molecular data in recent years, but surprisingly little is known about local and spatial genetic structuring of agaonid wasp populations. Using microsatellite markers, we analysed genetic structuring of Ceratosolen fusciceps, the fig wasp pollinating Ficus racemosa, a fig tree species widely distributed from India to Australia. In sampling stretching from the south of China to the south of Thailand we found evidence for only a single pollinating wasp species in continental South-East Asian mainland. We found no evidence for the co-occurrence of cryptic species within our subcontinent sampling zone. We observed no spatial genetic structure within sites and only limited structuring over the whole sampling zone, suggesting that F. racemosa is pollinated by a single population of a single agaonid wasp species all over continental South-East Asia. An additional sample of wasps collected on F. racemosa in Australia showed clear-cut genetic differentiation from the Asian continent, suggesting allopatric divergence into subspecies or species. We propose that the frequent local co-occurrence of sister species found in the literature mainly stems from contact zones between biogeographic regions, and that a single pollinator species over wide areas might be the more common situation everywhere else. [source] Characterization of a hotspot for mimicry: assembly of a butterfly wing transcriptome to genomic sequence at the HmYb/Sb locusMOLECULAR ECOLOGY, Issue 2010LAURA FERGUSON Abstract The mimetic wing patterns of Heliconius butterflies are an excellent example of both adaptive radiation and convergent evolution. Alleles at the HmYb and HmSb loci control the presence/absence of hindwing bar and hindwing margin phenotypes respectively between divergent races of Heliconius melpomene, and also between sister species. Here, we used fine-scale linkage mapping to identify and sequence a BAC tilepath across the HmYb/Sb loci. We also generated transcriptome sequence data for two wing pattern forms of H. melpomene that differed in HmYb/Sb alleles using 454 sequencing technology. Custom scripts were used to process the sequence traces and generate transcriptome assemblies. Genomic sequence for the HmYb/Sb candidate region was annotated both using the MAKER pipeline and manually using transcriptome sequence reads. In total, 28 genes were identified in the HmYb/Sb candidate region, six of which have alternative splice forms. None of these are orthologues of genes previously identified as being expressed in butterfly wing pattern development, implying previously undescribed molecular mechanisms of pattern determination on Heliconius wings. The use of next-generation sequencing has therefore facilitated DNA annotation of a poorly characterized genome, and generated hypotheses regarding the identity of wing pattern at the HmYb/Sb loci. [source] | ||||||||||||||||||||||