Does plasticity drive speciation? Host‐plant shifts and diversification in nymphaline butterflies (Lepidoptera: Nymphalidae) during the tertiary

How and why the great diversity of phytophagous insects has evolved is not clear but, if the explanation is the diversity of plants as a resource, colonizations of novel plant taxa can be expected to be associated with higher net speciation rates. In the present study, we make use of recent advances in plant and butterfly systematics to trace the evolution of host-plant utilization in the butterfly subfamily Nymphalinae (tribes Nymphalini, Melitaeini, and the probably paraphyletic 'Kallimini'). A clear historical pattern emerges, with an ancestral host-plant theme of 'urticalean rosids' and two major colonizations of novel distantly-related plant clades. The asterid order Lamiales was colonized by an ancestor of 'Kallimini' + Melitaeini and the family Asteraceae in Asterales was later colonized by Melitaeini butterflies. These colonization events appear to have been followed by increases in the rate of net butterfly diversification. Two not mutually exclusive scenarios to explain such patterns have been suggested: (1) adaptive radiation due to release from competition following host-plant shifts or (2) higher rates of net speciation during a relatively long-lasting potentially polyphagous (plastic) state. In support of the 'plasticity scenario', phylogenetic traces of a long-lasting stage with some potential to feed on more than one host-plant clade can still be seen, despite the ancient age of the colonizations. When angiosperm communities changed after the K/T boundary due to extinctions and subsequent diversification, herbivore taxa that could occupy several alternative niches may have had the greatest opportunity to diversify in turn.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 115–130.     

Genetic instability and rapid speciation: are they coupled?

Models of rapid speciation by fixation of underdominant chromosomal rearrangements are constrained by multiple conditions on population structure and chromosomal performance. Realistic population conditions impose long periods of time to fixation or reproductive isolation, even under a model of accumulation of successive advantageous slightly underdominant rearrangements. However, when increased mutation rates are considered, fixation time is significantly reduced. Evidence is presented of high rates of chromosomal rearrangement production under genomic stress, such as in inbred and interspecific crosses. These episodes of high instability are most probably the result of mobile element transpositions, since transposition is also increased under genomic stress. Nonetheless, the evolutionary value of mobile elements to speed up speciation will be only significant if their mutagenic potential is activated in concert with population scenarios favorable to speciation events. Although this coupling needs to be demonstrated, many models of rapid speciation are carried out under population conditions favoring inbreeding and/or hybridization.     

Protected areas in the world’s ecoregions: How well connected are they?

Protected areas (PAs) are the main instrument for biodiversity conservation, which has triggered the development of numerous indicators and assessments on their coverage, performance and efficiency. The connectivity of the PA networks at a global scale has however been much less explored; previous studies have either focused on particular regions of the world or have only considered some types of PAs.Here we present, and globally assess, ProtConn, an indicator of PA connectivity that (i) quantifies the percentage of a study region covered by protected connected lands, (ii) can be partitioned in several components depicting different categories of land (unprotected, protected or transboundary) through which movement between protected locations may occur, (iii) is easy to communicate, to compare with PA coverage and to use in the assessment of global targets for PA systems.We apply ProtConn to evaluate the connectivity of the PA networks in all terrestrial ecoregions of the world as of June 2016, considering a range of median dispersal distances (1–100 km) encompassing the dispersal abilities of the large majority of terrestrial vertebrates.We found that 9.3% of the world is covered by protected connected lands (average for all the world’s ecoregions) for a reference dispersal distance of 10 km, increasing up to 11.7% for the largest dispersal distance considered of 100 km. These percentages are considerably smaller than the global PA coverage of 14.7%, indicating that the spatial arrangement of PAs is only partially successful in ensuring connectivity of protected lands. The connectivity of PAs largely differed across ecoregions. Only about a third of the world’s ecoregions currently meet the Aichi Target of having 17% of the terrestrial realm covered by well-connected systems of PAs. Finally, our findings suggest that PAs with less strict management objectives (allowing the sustainable use of resources) may play a fundamental role in upholding the connectivity of the PA systems.Our analyses and indicator make it possible to identify where on the globe additional efforts are most needed in expanding or reinforcing the connectivity of PA systems, and can be also used to assess whether newly designated sites provide effective connectivity gains in the PA system by acting as corridors or stepping stones between other PAs. The results of the ProtConn indicator are available, together with a suite of other global PA indicators, in the Digital Observatory for Protected Areas of the Joint Research Centre of the European Commission.     

Peptides in the Hydrozoa: are they transmitters?

A family of peptides with the carboxy-terminus Arg-Phe-amide has been localized to specific subpopulations of neurons in every cnidarian species examined. These neurons are typically sensory in character or are associated with smooth muscle. Although a transmitter role for these peptides has been suggested for anthozoans at neuromuscular synapses, no such evidence is available for hydrozoans. Instead there is evidence that RF-amides can be modulators of neuronal activity which takes the form of a biphasic (inhibitory then excitatory) response in vivo, while in vitro only the inhibitory response is seen. Voltage clamp studies of identified motor neurons showed large, transitory outward currents when Pol-RF-amide peptide was applied.     

Does the DNA barcoding gap exist? – a case study in blue butterflies (Lepidoptera: Lycaenidae)

Background

DNA barcoding, i.e. the use of a 648 bp section of the mitochondrial gene cytochrome c oxidase I, has recently been promoted as useful for the rapid identification and discovery of species. Its success is dependent either on the strength of the claim that interspecific variation exceeds intraspecific variation by one order of magnitude, thus establishing a "barcoding gap", or on the reciprocal monophyly of species.

Results

We present an analysis of intra- and interspecific variation in the butterfly family Lycaenidae which includes a well-sampled clade (genus Agrodiaetus) with a peculiar characteristic: most of its members are karyologically differentiated from each other which facilitates the recognition of species as reproductively isolated units even in allopatric populations. The analysis shows that there is an 18% overlap in the range of intra- and interspecific COI sequence divergence due to low interspecific divergence between many closely related species. In a Neighbour-Joining tree profile approach which does not depend on a barcoding gap, but on comprehensive sampling of taxa and the reciprocal monophyly of species, at least 16% of specimens with conspecific sequences in the profile were misidentified. This is due to paraphyly or polyphyly of conspecific DNA sequences probably caused by incomplete lineage sorting.

Conclusion

Our results indicate that the "barcoding gap" is an artifact of insufficient sampling across taxa. Although DNA barcodes can help to identify and distinguish species, we advocate using them in combination with other data, since otherwise there would be a high probability that sequences are misidentified. Although high differences in DNA sequences can help to identify cryptic species, a high percentage of well-differentiated species has similar or even identical COI sequences and would be overlooked in an isolated DNA barcoding approach.     

Organellar genes: why do they end up in the nucleus?

Many mitochondrial and plastid proteins are derived from their bacterial endosymbiotic ancestors, but their genes now reside on nuclear chromosomes instead of remaining within the organelle. To become an active nuclear gene and return to the organelle as a functional protein, an organellar gene must first be assimilated into the nuclear genome. The gene must then be transcribed and acquire a transit sequence for targeting the protein back to the organelle. On reaching the organelle, the protein must be properly folded and modified, and in many cases assembled in an orderly manner into a larger protein complex. Finally, the nuclear copy must be properly regulated to achieve a fitness level comparable with the organellar gene. Given the complexity in establishing a nuclear copy, why do organellar genes end up in the nucleus? Recent data suggest that these genes are worse off than their nuclear and free-living counterparts because of a reduction in the efficiency of natural selection, but do these population-genetic processes drive the movement of genes to the nucleus? We are now at a stage where we can begin to discriminate between competing hypotheses using a combination of experimental, natural population, bioinformatic and theoretical approaches.     

Non-ecological speciation, niche conservatism and thermal adaptation: how are they connected?

During the last decade, the ecological theory of adaptive radiation, and its corollary ??ecological speciation??, has been a major research theme in evolutionary biology. Briefly, this theory states that speciation is mainly or largely the result of divergent selection, arising from niche differences between populations or incipient species. Reproductive isolation evolves either as a result of direct selection on mate preferences (e.g. reinforcement), or as a correlated response to divergent selection (??by-product speciation??). Although there are now many tentative examples of ecological speciation, I argue that ecology??s role in speciation might have been overemphasised and that non-ecological and non-adaptive alternatives should be considered more seriously. Specifically, populations and species of many organisms often show strong evidence of niche conservatism, yet are often highly reproductively isolated from each other. This challenges niche-based ecological speciation and reveals partial decoupling between ecology and reproductive isolation. Furthermore, reproductive isolation might often evolve in allopatry before ecological differentiation between taxa or possibly through learning and antagonistic sexual interactions, either in allopatry or sympatry. Here I discuss recent theoretical and empirical work in this area, with some emphasis on odonates (dragonflies and damselflies) and suggest some future avenues of research. A main message from this paper is that the ecology of species differences is not the same as ecological speciation, just like the genetics of species differences does not equate to the genetics of speciation.     

Halocins: are they involved in the competition between halobacteria in saltern ponds?

Many representatives of the family Halobacteriaceae ("halobacteria") excrete halophilic bacteriocins (halocins) that inhibit the growth of other halobacteria. In spite of the fact that halocin production is widespread among the Halobacteriaceae, no information is available on their ecological significance. To test whether halocins may play a role in the interspecies competition between dif-ferent types of halobacteria in saltern crystallizer ponds inhabited by dense communities of these red halophiles, we assayed for halocins active against a variety of halobacteria in salterns from different locations worldwide. Detection of halocin activity was based on the inhibition of growth of indicator organisms on agar plates, the decreased incorporation of radiolabeled substrates, and microscopic examinations. No halocin activity was detected in any of the brines examined, in spite of the fact that halocin production was demonstrated in cultures of most microorganisms isolated from these brines. Thus, the contribution of halocins in the competition between different halobacteria in hypersaline aquatic environments is probably negligible. Received: July 29, 1999 / Accepted: October 18, 1999     

Spatial and temporal patterns of intertidal macrobenthic populations in the Oosterschelde: are they influenced by the construction of the storm-surge barrier?

The construction of a storm-surge barrier in the mouth of the Oosterschelde caused important hydrodynamical and morphological changes that could influence the macrobenthic populations. This paper is one in a series of five all dealing with the effects of the storm-surge barrier on macrozoobenthos and analyses the spatial and temporal distribution of macrozoobenthos in the Oosterschelde and its relationship with some environmental parameters, based on two large scale sampling campaigns, one before and one after the completion of the barrier.The sediment of the sampling stations was fine, well sorted sand, with an average mud content of about 2.5 %. Only in the Krabbenkreek the sediment was coarser in 1989. The tidal elevation of the sampling sites decreased significantly in 1989.The density of macrozoobenthos was significantly lower, the biomass higher in 1989. The density was dominated by deposit feeders, the biomass by filter feeders. The difference in biomass between both years was mainly due to a substantial increase of the biomass of filter feeders in 1989. The number of species per station was significantly smaller in 1989 than in 1985. Between 1985 and 1989, frequency of occurrence decreased in 34 versus 13 which increased, density increased in 13 species and decreased in 34 species, biomass increased in 18 species and decreased in 29 species.Based on TWINSPAN several clusters of stations, each with a different faunal composition, were identified. These clusters did not form distinct zones on the tidal flats but were dispersed widely.The relationship between density and biomass of different trophic groups and the mud content of the sediment and the depth was analysed. This relationship sometimes differed clearly between years. The correlation coefficient of a multiple regression between density and biomass of individual species and environmental factors, although significant in most cases, was very low, indicating that only a small proportion of the species variability was explained. The relationship between benthos and environmental factors was further analysed by canonical correlation analysis and multivariate discriminant analysis that gave different results for the 1985 and 1989 data. This is probably due to the broad tolerance of the species to the range of the environmental variables found in our study area. From a TWINSPAN of the density data of 1985 and 1989 together we could conclude that, although the environmental parameters in a group of stations, showing a large faunal similarity in one year, did not change, the faunal composition did. This indicates that faunal changes are not necessarily linked to changes in the measured environmental parameters.In the discussion the different factors affecting macrobenthic populations are situated and it is suggested that the macrobenthic populations are probably more towards the nonequilibrium end of the continuum between nonequilibrium and equilibrium communities as defined by Wiens (1984).Although the impact of the construction of the barrier on the macrobenthic community seems at present to be rather small this does not mean that on the long-term there will be no effect.     

Mitochondria: are they the seat of senescence?

The frequently quoted figure for the fractional univalent reduction of oxygen to superoxide in mitochondria is certainly too high by at least one order of magnitude. This is so because the higher number (2%) was derived from mitochondria whose cytochrome c oxidase was blocked with cyanide. Nevertheless, even the more correct number (0.1%) means that the production of O(2)(-) and H(2)O(2) in mitochondria is large and apt to result in damage to macromolecules in spite of such defensive enzymes as superoxide dismutases and glutathione peroxidase. The data available for nematodes and flies provide a compelling case for the view that the accumulation of oxidative damage to specific mitochondrial proteins leads to the progressive dysfunction that we see as senescence. The data available from work with mammals are much weaker and do not yet allow a strong position to be taken.     

Molecular evidence for hybridization in Colias (Lepidoptera: Pieridae): are Colias hybrids really hybrids?

Gene flow and hybridization among species dramatically affect our understanding of the species as a biological unit, species relationships, and species adaptations. In North American Colias eurytheme and Colias eriphyle, there has been historical debate over the extent of hybridization occurring and the identity of phenotypically intermediate individuals as genetic hybrids. This study assesses the population structure of these two species to measure the extent of hybridization and the genetic identity of phenotypic intermediates as hybrids. Amplified fragment length polymorphism (AFLP) marker analysis was performed on 378 specimens collected from northern California and Nevada. Population structure was inferred using a Bayesian/Markov chain Monte Carlo method, which probabilistically assigns individuals to genetic clusters. Three genetic clusters provided the best fit for the data. C. eurytheme individuals were primarily assigned to two closely related clusters, and C. eriphyle individuals were mostly assigned to a third, more distantly related cluster. There appeared to be significant hybridization between the two species. Individuals of intermediate phenotype (putative hybrids) were found to be genetically indistinguishable from C. eriphyle, indicating that previous work based on the assumption that these intermediate forms are hybrids may warrant reconsideration.     

Dispersal and egg shortfall in Monarch butterflies: what happens when the matrix is cleaned up?

1. We use an individual‐based model describing the life of a monarch butterfly, which utilises milkweeds both aggregated in patches and scattered across the wider landscape as a substrate for laying eggs. The model simplifies the metapopulation of milkweed habitat patches by representing them as a proportion of the overall landscape, with the rest of the landscape considered matrix, which may contain some low density of milkweed plants. 2. The model simulates the number of eggs laid daily by a butterfly as it searches for hosts. The likelihood of finding hosts is related to the density of plants and the search ability of the butterfly. For an empty matrix, remaining in a habitat patch results in more eggs laid. However individuals that are good searchers have almost equivalent success without remaining in a habitat patch. These individuals are most affected by the presence of hosts in the matrix. 3. Given realistic values of habitat patch availability, our model shows that the presence of plants at a low density in the matrix has a substantial impact on the number of eggs laid; removing these plants can reduce lifetime potential fecundity by ca. 20%. These results have implications for monarch butterflies inhabiting agricultural landscapes, in which genetically modified soybean that is resistant to herbicides has resulted in the decimation of milkweeds over large areas.     

Androgens in rheumatoid arthritis: when are they effectors?

Neither hormone receptor genes nor plasma androgens seem significantly altered in female subjects before they became affected by rheumatoid arthritis (RA) and, therefore, do not seem to play a role as risk factors for its development. However, serum testosterone levels are inversely correlated with RA activity and dehydro-epiandrosterone sulfate (DHEAS) plasma levels are inversely correlated with both disease duration and clinical severity in patients already affected by active RA. In particular, gonadal and adrenal androgens (that is, testosterone and DHEAS) are significantly decreased in inflamed synovial tissue/fluids during active disease as a consequence of the inflammatory reaction, which supports a pro-inflammatory milieu in RA joints. Recently, male gender has been found to be a major predictor of remission in early RA.     

Where are the cores in this thing? …and what are they computing? (with apologies to Larry Abbott)

Journal of Computational Neuroscience -     

Red & black or black & white? Phylogeny of the Araschnia butterflies (Lepidoptera: Nymphalidae) and evolution of seasonal polyphenism

Phylogeny of the butterfly genera Araschnia, Mynes, Symbrenthia and Brensymthia (Lepidoptera: Nymphalidae: Nymphalini) is reconstructed, based on 140 morphological and ecological characters. The resulting tree shows that Araschnia is a sister group of the clade including Symbrenthia, Mynes and Brensymthia (Symbrenthia is paraphyletic in the respect of remaining genera; Symbrenthia hippalus is a derived species of Mynes). The species-level relationships within Araschnia are robustly supported as follows: (A. davidis (prorsoides ((zhangi doris) (dohertyi (levana burejana))))). Analysis of the wing colour-pattern characters linked with the seasonal polyphenism in the Araschnia species suggests that the black and white coloration of the long-day (summer) generation is apomorphic. Biogeographically, the origin of polyphenism in Araschnia predates the dispersal of some Araschnia species towards the Palaearctic temperate zone, and the ecological cause of the polyphenism itself is then probably not linked with thermoregulation. The possible mimetic/cryptic scenarios for the origin of Araschnia polyphenism are discussed.     

Ectoparasites: are they the proximate cause of cleaning interactions?

We tested the importance of ectoparasites in cleaning symbioses by comparing the activity of Caribbean cleaning gobies ( Elacatinus evelynae ) and of their clients during three daily periods (early morning, midday and late afternoon) in which ectoparasite availability varied naturally. Emergence from the benthos of gnathiid isopod larvae, the main target of cleaning goby predation, was higher at night, when cleaners are inactive, than during the day. Overall ectoparasite loads also tended to be higher on clients in the morning. This coincided with higher rates of visits to cleaning stations by client fish in the morning than at midday, but high rates of client visits were also recorded in the late afternoon. Clients were more likely to adopt stereotypical incitation poses, which increase the likelihood of being cleaned, in the morning than later in the day. Inspection bouts by cleaning gobies were longest in the morning. Cleaner and client behaviours therefore change predictably in response to natural diurnal variation in ectoparasite availability. These results add to a growing number of studies supporting the idea that cleaning symbioses are mutualisms dependent on ectoparasite removal.     

Amyloids of multiple species: are they helpful in survival?

Amyloids are primarily known for their roles in neurodegenerative disorders, as well as in systemic diseases like diabetes. Evolutionary forces tend to maintain a healthy set of heritable characteristics, while eliminating toxic or unfavourable elements; but amyloids seem to represent an exception to this fundamental concept. In addition to their presence in mammals, amyloids also persist in the proteome of many lower organisms that may be linked with possible roles in survival, which are still unexplored. Herein, we address some unanswered questions regarding amyloids: are these well‐structured proteinaceous aggregates a by‐product of inefficient folding events, or have they been retained in our protein repertoire for as yet unknown functional roles; and how do protein misfolding and associated disorders originate, despite the presence of protein quality‐control systems inside the cells? This review aims to extend our current understanding about the multifaceted useful properties of amyloids and their functional interactions with other molecular pathways in various species; this may provide new insights to identify novel therapeutic strategies for ageing and neurodegenerative diseases.