Lack of mitochondrial genetic structure in hamlets (Hypoplectrus spp.): recent speciation or ongoing hybridization?

Species in the genus Hypoplectrus (hamlet fish) have been recognized primarily on the basis of colour morphology, which varies substantially. Limited differentiation in other morphological characters, however, has led to ongoing debate about their taxonomy. Our analysis of mtDNA sequences demonstrates neither reciprocal monophyly nor significant genetic differentiation among hamlet colour morphs. These data are potentially consistent with a model of recent speciation due to sexual selection on colour morphology. The presence within hamlets of two divergent mtDNA clades, however, suggests a longer history during which hybridization and gene flow have prevented the differentiation of hamlet colour morphs, at least in neutral genetic markers.     

Geographic patterns in fruit colour diversity: do leaves constrain the colour of fleshy fruits?

We tested for geographic patterns in fruit colour diversity. Fruit colours are thought to promote detection by seed dispersers. Because seed dispersers differ in their spectral sensitivities, we predicted that fruit colour diversity would be higher in regions with higher seed disperser diversity (i.e. the tropics). We collected reflectance data on 232 fruiting plant species and their natural backgrounds in seven localities in Europe, North and South America, and analysed fruit colour diversity according to the visual system of birds—the primary consumer types of these fruits. We found no evidence that fruit colours are either more conspicuous or more diverse in tropical areas characterised by higher seed disperser diversity. Instead, fruit colour diversity was lowest in central Brazil, suggesting that fruit colours may be more diverse in temperate regions. Although we found little evidence for geographic variation in fruit hues, the spectral properties of fruits were positively associated with the spectral properties of backgrounds. This result implies that fruit colours may be influenced by selection on the reflectance properties of leaves, thus constraining the evolution of fruit colour. Overall, the results suggest that fruit colours in the tropics are neither more diverse nor more conspicuous than temperate fruits, and that fruit colours may be influenced by correlated selection on leaf reflectance properties. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genomic islands of speciation or genomic islands and speciation?

Populations of the malaria mosquito, Anopheles gambiae, are comprised of at least two reproductively isolated, sympatric populations. In this issue, White et al. (2010) use extensive sampling, high‐density tiling microarrays, and an updated reference genome to clarify and expand our knowledge of genomic differentiation between these populations. It is now clear that DNA near the centromeres of all three chromosomes are in near‐perfect disequilibrium with each other. This is in stark contrast to the remaining 97% of the assembled genome, where fixed differences between populations have not been found, and many polymorphisms are shared. This pattern, coupled with direct evidence of hybridization in nature, supports models of “mosaic” speciation, where ongoing hybridization homogenizes variation in most of the genome while loci under strong selection remain in disequilibrium with each other. However, unambiguously demonstrating that selection maintains the association of these pericentric “speciation islands” in the face of gene flow is difficult. Low recombination at all three loci complicates the issue, and increases the probability that selection unrelated to the speciation process alters patterns of variation in these loci. Here, we discuss these different scenarios in light of this new data.     

Morphotypes,varieties, or subspecies?: genetic diversity and differentiation of four Saintpaulia (Gesneriaceae) morphotypes from the East Usambara Mountains,Tanzania

Saintpaulia (H. Wendl.) is a forest-dependent, endangered plant genus endemic to Tanzania and Kenya. The taxonomy of Saintpaulia from the Usambara Mountains and adjacent lowlands in north-eastern Tanzania is problematic because of the morphological similarity of the species and the presence of considerable intraspecific variation. Conventional molecular phylogenetic methods have failed to reveal the genetic structure of this Saintpaulia complex. In this study, we assessed the genetic composition of 12 Saintpaulia populations, representing four different morphotypes, from the East Usambara Mountains using inter-simple sequence repeat (ISSR) markers. Relatively high genetic diversities were observed within populations (mean h  = 0.320), indicating their adaptive potential. Little genetic differentiation amongst populations (mean F _st  = 0.063) and the genetic divergence of the rosulate and trailing morphotypes support the hypothesis of ongoing divergent evolution within the East Usambara metapopulation(s) of Saintpaulia .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 347–355.     

Distribution,origin and speciation,wing development,and host‐plant relationships of New Zealand Targaremini (Hemiptera: Lygaeidae)

Three faunal areas—northern (Three Kings Islands, Northland, Auckland, Coromandel Peninsula, and offshore islands), central (most of Nelson, north‐east Buller, Marlborough, Marlborough Sounds, Kaikoura, northern North Canterbury), and southern (Fiordland, southern Otago Lakes, southern Central Otago, southern Dunedin, Southland, Stewart Island) —are each characterised by the local endemicity of about 20% of the total targaremine species of New Zealand. They are separated by areas of no endemicity. Arbitrary subareas are delineated in the northern and southern areas. Species not endemic to a single faunal area have wider ranges covering more than one area. The targaremine faunal areas and subareas are compared with those recognised for other units of the New Zealand biota. Instances of allopatric and parapatric species are listed. All 30 targaremine species in New Zealand are endemic; the effects of Pleistocene cold climate on their distribution and speciation are discussed. Wing development is discussed in relation to its role in initial distribution and dispersal over geographical barriers, and in subsequent adaptations to ecological niches and/or post‐Pleistocene extensions of range. Analysis of host‐plant data reveals that the Targaremini have no marked host specificity; ecologically significant data are presented for several species.     

Adaptation and speciation: what can F(st) tell us?

A useful way of summarizing genetic variability among different populations is through estimates of the inbreeding coefficient, F(st). Several recent studies have tried to use the distribution of estimates of F(st) from individual genetic loci to detect the effects of natural selection. However, the promise of this approach has yet to be fully realized owing to the pervasive dogma that this distribution is highly dependent on demographic history. Here, I review recent theoretical results that indicate that the distribution of estimates of F(st) is generally expected to be robust to the vagaries of demographic history. I suggest that analyses based on it provide a useful first step for identifying candidate genes that might be under selection, and explore the ways in which this information can be used in ecological and evolutionary studies.     

Distribution and diversity of desmosomatid and nannoniscid isopods (Crustacea) on the Greenland–Iceland–Faeroe Ridge

The distribution and diversity of isopods (Crustacea, Isopoda; families Desmosomatidae Sars, 1897 and Nannoniscidae Hansen, 1916) was examined in Icelandic waters where a diversity of water masses (temperature range −0.9 to 12°C) occurs and the topography is characterized by the large and shallow Greenland–Iceland–Faeroe (GIF) Ridge extending across the North Atlantic in an east-west direction. Both families were species rich in the area, in total occurring with 34 species in 20 genera. Most of the species were restricted either to the north (10) or to the south (14) of the GIF Ridge, occurring either in cold (−0.8 to 2.8°C) or warm (>2°C) water masses. Five species were found on both sides of the Ridge, occurring at a wide range of temperatures (−0.9 to >4°C), while another five species extend across the GIF Ridge. Most species occurred in two and more water masses and the species north of the Ridge occurred usually within narrower temperature range than the species living south of the Ridge. The water masses in association with the Ridge seem to limit distribution of most species. Despite similar number of species occurring in the areas north and south of the Ridge, the areas differ considerably in diversity pattern with depth.     

Signatures of selection? Patterns of microsatellite diversity on a chromosome containing a selected locus

This paper explores patterns of genetic diversity near a locus known to have been under selection. The myostatin gene (GDF-8) has been shown to be associated with double muscling, a phenotype selected for in a number of cattle breeds. We examined population genetic parameters for microsatellite loci at varying distances from GDF-8 in double-muscled (DM) and non-double-muscled (non-DM) cattle breeds in order to assess patterns of diversity. A theoretical analysis was also performed to predict the patterns of diversity expected under different scenarios. We found differences in the patterns of heterozygosity, allele diversity and linkage disequilibrium between DM and non-DM breeds. However, there were some exceptions to the predicted patterns. These are discussed in light of the histories of the breeds and the potential for using microsatellite diversity for mapping trait genes in livestock populations.     

Are the oral teeth of combtooth bennies (Salariini: Teleostei) merely combs?

Careful analysis of gut contents has resulted in the reclassification of several species of grazing fish as detritivores, shifting the trophodynamic assignment of many prominent reef grazers. Combtoothed blennies, which are among the most numerous grazing fish of the Great Barrier Reef, have been shown to target the detrital component of the epilithic algal matrix (EAM). It has been suggested that blennies have specialized dental morphology that allows them to comb through fronds of algae, collecting detritus, while leaving the algal component intact. In this study, we analysed the capability of a common reef flat blenny, Salarias fasciatus, to remove algae by (i) examining oral morphology for evidence of wear and adaptations for abrasion, and (ii) a short-term EAM feeding experiment. Examination of S. fasciatus teeth with scanning electron microscopy (SEM) showed evidence of macrowear (changes in tooth height or shape), microwear (surface chips and striae), and tooth replacement that suggests abrasion on the substrate. Energy Dispersive X-ray Spectrometry (EDS) revealed that oral teeth incorporate mineral iron. When fed artificial substrata with a developed EAM layer S. fasciatus removed 57% of photosynthetic material and 38.5% of organic biomass. Although studies have found that blenny gut contents consist predominantly of detritus, blennies are still likely to contribute to the removal of algae on coral reefs.     

LDH isozymes in amazon fish—III. Distribution patterns and functional properties in Serrasalmidae (Teleostei: Ostariophysi)

• 1.1. The patterns of distribution of LDH isozymes in five tissues from 12 Serrasalmidae species have been studied through two-fold serial dilution (Klebe's test) as well as the pyruvate inhibition of LDH enzyme in skeletal and heart muscles (low/high ratios).
• 2.2. The species' electrophoretic patterns differ by orthologous A₄ isozyme mobilities since the orthologous B₄ isozymes present similar electrophoretic migration. These differences between Ldh-A and Ldh-B products reflect three-, four-, and five-banded patterns. Thus, different LDH isozyme numbers formed from A and B subunits should not be used as an evolutionary or phylogenetic characteristic from different taxonomic groups.
• 3.3. Out of 66 pairs of species only five pairs showed significant differences in the distribution patterns in all five analyzed tissues, while no pair of species showed the same distribution in these tissues. This variation was explained as differential regulation of structural genes among tissues and/or species.
• 4.4. Functional properties showed significant between the LDHs from heart and skeletal muscles, and are consistent with a preference for aerobic metabolism. We suppose that by selecting B-like subunits these fishes are able to maintain good control of aerobic/anaerobic transitions, maintaining predominantly oxidative metabolism even in hypoxic waters, with which they have to cope.

     

Species of Haliotrema Johnston & Tiegs, 1922 (Monogenea: Dactylogyridae) from Zanclus cornutus (L.) (Teleostei: Zanclidae) and Acanthurus nigrofuscus (Forssk?l) (Teleostei: Acanthuridae) in the South China Sea

Four species of Haliotrema Johnston & Tiegs, 1922, including three new taxa, are described from the gills of two species of coral reef fishes, Zanclus cornutus (Linnaeus) and Acanthurus nigrofuscus (Forssk?l), off the Dongsha Islands in the South China Sea. Haliotrema dongshaense n. sp., from Z. cornutus, is differentiated from other existing congeneric species by its peculiar male copulatory organ, comprising a harp-shaped copulatory tube and a cup-shaped base, and two groups of short longitudinal muscles lying on either side of the vaginal vestibule. Haliotrema zigmoidocirrus n. sp. from Z. cornutus and H. nigrofusci n. sp. from A. nigrofuscus are differentiated from other congeneric species by their male copulatory organ, which has a cup-shaped base, bell-shaped middle and Z-shaped distal part, and the latter can be readily differentiated from the former by its distinctively wider haptor and longer connecting bars. Haliotrema sicklocirrus Wang, 2007, from Z. cornutus, is redescribed with additional details, including the sinistral position of the accessory piece of the male copulatory organ, the absence of eyespots and the morphology of the connecting bars.     

Evolution of dark colour in toucans (Ramphastidae): a case of molecular adaptation?

In the last decades, researchers have been able to determine the molecular basis of some phenotypes, to test for evidence of natural selection upon them, and to demonstrate that the same genes or genetic pathways can be associated with convergent traits. Colour traits are often subject to natural selection because even small changes in these traits can have a large effect on fitness via camouflage, sexual selection or other mechanisms. The melanocortin‐1 receptor locus (MC1R) is frequently associated with intraspecific coat colour variation in vertebrates, but it has been far harder to demonstrate that this locus is involved in adaptive interspecific colour differences. Here, we investigate the contribution of the MC1R gene to the colour diversity found in toucans (Ramphastidae). We found divergent selection on MC1R in the clade represented by the genus Ramphastos and that this coincided with the evolution of darker plumage in members of this genus. Using phylogenetically corrected correlations, we show significant and specific relationships between the rate of nonsynonymous change in MC1R (dN) and plumage darkness across Ramphastidae, and also between the rate of functionally significant amino acid changes in MC1R and plumage darkness. Furthermore, three of the seven amino acid changes in MC1R that occurred in the ancestral Ramphastos branch are associated with melanism in other birds. Taken together, our results suggest that the dark colour of Ramphastos toucans was related to nonsynonymous substitutions in MC1R that may have been subject to positive selection or to a relaxation of selective pressure. These results also demonstrate a quantitative relationship between gene and phenotype evolution, representing an example of how MC1R molecular evolution may affect macroevolution of plumage phenotypes.     

Species diversity in Gymnogeophagus (Teleostei: Cichlidae) and comparative biogeography of cichlids in the Middle Paraná basin,an emerging hotspot of fish endemism

Hydrobiologia - We address the diversity of two species groups of the cichlid genus Gymnogeophagus in the Middle Paraná basin using molecular phylogeography and traditional morphological...     

Coevolution of post-Palaeozoic arthropod basibiont diversity and encrusting bryozoan epibiont diversity?

We hypothesize that the diversification of motile marine arthropods with hard carapaces resulted in a concurrent increase in the diversity of encrusting marine bryozoans whose larvae exploited those substrates through the Mesozoic and Cenozoic. To test this, family-level data were tabulated from the literature on the post-Palaeozoic diversity of motile marine arthropod basibionts and sessile marine bryozoan epibionts. We found strong temporal correlation from general to more specific basibiont-epibiont relationships (i.e. arthropods and bryozoans in general to decapods and encrusting gymnolaemates to robust decapods and encrusting cheilostomes in particular). We compared the diversification of bryozoans to another common group of basibionts (i.e. molluscs) and found weaker correlations. This suggests that the diversification of motile arthropods with hard carapaces (e.g. brachyuran crabs) may have played a role in the diversification of sessile bryozoans (e.g. encrusting cheilostomes) in the post-Palaeozoic.     

Does diversity beget diversity? A case study of crops and weeds

Abstract. The ecological literature is ambiguous as to whether the initial diversity of a plant community facilitates or deters the diversity of colonizing species. We experimentally planted annual crop species in monoculture and polyculture, and examined the resulting weed communities. The species composition of weeds was similar among treatments, but the species richness of weeds was significantly higher in the polycultures than in the monocultures. This supports the ‘diversity begets diversity’ hypothesis. Environmental microheterogeneity, diversity promoters, and ecological equivalency do not seem able to explain the observed patterns.     

Evolution of alternative male morphotypes in oxyurid nematodes: a case of convergence?

Male dimorphism has been reported across different taxa and is usually expressed as the coexistence of a larger morph with exaggerated male traits and a smaller one with reduced traits. The evolution and maintenance of male dimorphism are still poorly understood for several of the species in which it has been observed. Here, we analyse male dimorphism in several species of reptile parasitic nematodes of the genus Spauligodon, in which a major male morph (exaggerated morph), which presents the traditional male morphological traits reported for this taxon, coexists with a minor morph with reduced morphological traits (i.e. reduced genital papillae) resembling more closely the males of the sister genus Skrjabinodon than Spauligodon major males. Because of the level of uncertainty in the results of ancestral state reconstruction, it is unclear if the existence of male dimorphism in this group represents independent instances of convergent evolution or an ancestral trait lost multiple times. Also, although the number of major males per host was positively correlated with the number of females, the same did not hold true for minor males, whose presence was not associated with any other ecological factor. Nevertheless, the existence of male dimorphism in Spauligodon nematodes is tentatively interpreted as resulting from alternative reproductive tactics, with differences in presence and number of individuals as indicators of differences in fitness, with the lower numbers of minor males per host likely maintained by negative frequency‐dependent selection.     

Tuber aestivum and Tuber uncinatum: two morphotypes or two species?

Tuber spp. are ectomycorrhizal fungi that establish symbioses with shrubs and trees. Because of their different smell and taste, Tuber uncinatum and Tuber aestivum are two truffle morphotypes with a different market value, but whether or not T. uncinatum and T. aestivum are different taxa is still an open debate among mycologists. In order to identify molecular keys characterizing both T. aestivum and T. uncinatum morphotypes, ITS/RFLPs analyses were carried out on a large collection of samples from all over Italy and from other European countries, followed by a study of the phylogenesis of ITS, beta-tubulin and EF 1-alpha genes, on representative samples. The present study provides compelling evidence that: (i) T. uncinatum and T. aestivum belong to the same species, (ii) neither morphotype presents a specific molecular fingerprint, but they may even share identical alleles at any of the loci analysed; (iii) T. aestivum is most likely under a selfing reproductive mode. Our findings suggest that ecological, rather than genetic causes may account for differences in sporal morphology, taste and smell between T. aestivum and T. uncinatum truffles.     

Where and why? Bees,snail shells and climate: Distribution of Rhodanthidium (Hymenoptera: Megachilidae) in the Iberian Peninsula

Species distribution patterns are widely studied through species distribution models (SDMs), focusing mostly on climatic variables. Joint species distribution models (JSDMs) allow inferring if other factors (biotic interactions, shared phylogenetic history or other unmeasured variables) can also have an influence on species distribution. We identified current distributional areas and optimal suitability areas of three species of the solitary snail‐shell bee Rhodanthidium (Hymenoptera: Megachilidae), and their host gastropod species in the Iberian Peninsula. We undertook SDMs using Maxent software, based on presence points and climatic variables. We also undertook JSDMs for the bees and the snails to infer if co‐occurrence could be a result of biotic interactions. We found that the three bee species: (1) use at least five different species of Mediterranean snails; (2) use empty shells not only for nesting but also for sheltering when there is adverse weather and during the night; (3) have their most suitable areas in the eastern and southern Iberian Peninsula, mostly on limestone areas; and (4) have their optimal range under Mediterranean climatic values for the studied variables. There is positive co‐occurrence of Rhodanthidium with the gastropod species, especially with the snail Sphincterochila candidissima. The contribution of the environmental component to the co‐occurrence is less than that of the residual component in those cases, suggesting that: (i) the use of biotic resources (between Rhodanthidium and the gastropod species); (ii) shared phylogenetic history (between R. septemdentatum and R. sticticum); or (iii) unmeasured variables are largely responsible for co‐occurrence.     

Thermal habitat segregation among morphotypes of whitefish (Coregonus lavaretus: Salmonidae) and invasive vendace (C. albula): a mechanism for co‐existence?

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