Showing papers in "Biological Journal of The Linnean Society in 1994"
TL;DR: Four trophic morphs of Arctic charr, Salvelinus alpinus, are supported by Lake Thingvallavatn; two of the morphs are benthic (small and large benthivorous charr) one exploits pelagic waters (planktivorous chr) and the fourth is found in both habitats (piscivorous Charr).
Abstract: Lake Thingvallavatn supports four trophic morphs of Arctic charr, Salvelinus alpinus (L.); two of the morphs are benthic (small and large benthivorous charr) one exploits pelagic waters (planktivorous charr) and the fourth is found in both habitats (piscivorous charr). The morphological variation among these morphs was analysed by use of principal component analysis and canonical discriminant analysis. The benthic morphs have a short lower jaw and long pectoral fins. The benthic fish also have fewer gillrakers than the other morphs. Small and large benthivorous charrs attain sexual maturity from 2 and 6 years of age, and at fork lengths from 7 and 22 cm, respectively. Small benthivorous charr retain their juvenile parr marks as adults, have beige ventral colours, and are frequently melanized under the lower jaw. Planktivorous and piscivorous charr attain sexual maturity from 4 and 6 years of age, from fork lengths of 15 and 23 cm, respectively. This phenotypic polymorphism is associated with habitat utilization and diet of the fish, and has probably arisen within the lake system through diversification and niche specialization. The pelagic morphs apparently stem from a single population, and are possibly diversified through conditional niche shifts which affect ontogeny. Juveniles reaching a body length of 23 cm may change from zooplankton to fish feeding. Asymptotic length increases thereby from 20.5 cm in planktivorous charr to 30.2 cm in piscivorous charr. The benthic morphs appear to represent separate populations, although both feed chiefly on the gastropod Lymnaea peregra . Their co-existence seems to be facilitated by size dependent constraints on habitat use. The small morph (asymptotic length 13.3 cm) exploit the interstitial crevices in the lava block substratum, whereas the large morph (asymptotic length 55.4 cm) live epibenthically.
261 citations
TL;DR: In constructing phylogenies from molecular data both the composition of the ingroup and the choice of outgroup can strongly affect the chances of obtaining the correct topology, so selection of sequence data, through omission or weighting, is also often necessary to reduce levels of homoplasy.
Abstract: In constructing phylogenies from molecular data both the composition of the ingroup and the choice of outgroup can strongly affect the chances of obtaining the correct topology. This is because tree topology and uneven rates of molecular evolution affect the ability of tree-building algorithms to find the correct tree. Outgroups can be added in one of two ways, either to a single sister clade (preferably the closest) or through addition of single taxa from different clades. On theoretical and empirical grounds the former strategy is shown to be much more beneficial, both in terms of redressing balance and reducing stemminess. For parsimony to perform well some selection of sequence data, through omission or weighting, is also often necessary to reduce levels of homoplasy.
245 citations
TL;DR: The striped and colour polymorphisms in T. cristinae appear to be an evolutionary consequence of differential predation on different backgrounds, and the implications of differentialpredation to food-plant utilization are discussed.
Abstract: Timema cristinae is a herbivorous insect that exhibits polymorphism for body coloration (green, red and grey morphs) and for pattern (striped, expressed only in the green morph, and unstriped). The striped green morph is associated with ceanothus (Ceanothus spinosus) and the unstriped green morph is associated with chamise (Adenostoma fasciculatum). This study examines the relative vulnerabilities to predation of the different pattern and colour morphs on their natural backgrounds. The vulnerabilities of the striped and unstriped morphs on their two food plants were tested using uncaged wild birds (Scrub Jays) and captive western fence lizards. Strong differential predation was observed suggesting that each morph is most cryptic on the food plant on which it is most common. Furthermore, in a mark-recapture experiment in a patch of ceanothus the unstriped and red morphs were recaptured in higher proportion than the other morphs. The vulnerabilities of the grey and green morphs on the ground and foliage were tested using lizards. The grey morph was more vulnerable on the plants than the green morph, but the inverse was observed on the ground (where they drop after a disturbance). This may be why the grey morph is not associated with specific food plants. The striped and colour polymorphisms in T. cristinae appear to be an evolutionary consequence of differential predation on different backgrounds. The implications of differential predation to food-plant utilization are discussed.
140 citations
TL;DR: Observations in the Cape Province, South Africa, showed that Disa ferruginea (Orchidaceae) is dependent on a single butterfly species—Meneris tulbaghia (Nymphalidae: Satyrinae)—for pollination, and compares favourably with a nectar-producing congener, Disa uniflora, which is also pollinated solely by M. tul baghia.
Abstract: Observations in the Cape Province, South Africa, showed that Disa ferruginea (Orchidaceae) is dependent on a single butterfly species—Meneris tulbaghia (Nymphalidae: Satyrinae)—for pollination. The flowers of D. ferruginea contain no food reward and, instead, appear to secure pollinator visits by imitating flowers which are nectar sources for the butterfly. A red-flowered form of D. ferruginea appears to mimic the red nectar-producing flowers of Tritoniopsis triticea (Iridaceae) in the south-western Cape, while an orange-flowered form of D. ferruginea appears to mimic the orange nectar-producing flowers of Kniphofia uvaria (Asphodelaceae) in the Langeberg Mountains. Reflectance spectra of the orchid's flowers closely match those of its putative models. Analysis of foraging movements of the butterfly in a mixed stand of D. ferruginea and T. triticea indicated that it does not discriminate between the nectarless orchid and the nectar-producing model. Populations of D. ferruginea which are sympatric with T. triticea have relatively high levels of pollination and fruit production, compared with populations where the orchid grows alone. Although other studies have reported relatively low fecundity in deceptive orchids, pollination and fruiting success in D. ferruginea compares favourably with a nectar-producing congener, Disa uniflora, which is also pollinated solely by M. tulbaghia.
119 citations
TL;DR: Much of the variation in chart size structure is suggested to be a consequence of increased seasonality in food supply in more northerly environments, coupled with feeding size thresholds, which result in larger members of a cohort being able to maintain growth rates on seasonally abundant prey while smaller individuals which cannot catch these items form a second mode of more slowly growing fish.
Abstract: The size structure of Arctic charr (Salvelinus alpinus) populations was analysed using published information; 44% of populations were bimodal, with both large (normal) and small (dwarf) morphs occurring within a cohort. The remaining populations were unimodal, consisting of normal-sized or of stunted adults. Bimodal populations increased in frequency with latitude and were characteristic of large, deep lakes with few fish species. The age and size at which bimodality developed, the size difference between the morphs, and the frequency of cannibalism in charr populations increased with latitude. A variety of genotypic and phenotypic explanations are examined. The evidence for specific differences between the morphs is unconvincing. Various competition and predation hypotheses fail to explain the occurrence of bimodality. Cannibalism does not cause bimodality despite being strongly associated with it since bimodality develops before charr become cannibalistic. Much of the variation in chart size structure is suggested to be a consequence of increased seasonality in food supply in more northerly environments, coupled with feeding size thresholds. The latter result in larger members of a cohort being able to maintain growth rates on seasonally abundant prey while smaller individuals which cannot catch these items form a second mode of more slowly growing fish. Bimodality is documented in a number of other, predominantly northern, fish species.
86 citations
TL;DR: Genetic variation for resistance to a high temperature stress under saturated humidity was examined within and among three Drosophila buzzatii populations from Australia, and significantly more males survived the heat stress than females, and, within each sex, larger flies were generally more heat resistant than smaller ones.
Abstract: Genetic variation for resistance to a high temperature stress under saturated humidity was examined within and among three Drosophila buzzatii populations from Australia. Further, the acclimation of this species to high temperatures was tested by pretreating flies for a shorter, sublethal, time period under conditions that lead to expression of heat shock proteins. Genetic variation for temperature resistance was present among lines for flies either pretreated to high temperature or not. Pretreating increased survival, with the benefit significantly higher if pretreating was performed 24 h rather than 96 h before exposure to the potentially lethal stress. For flies pretreated at both times, resistance to heat stress was even greater. The lack of a significant treatment by line interaction term suggested that all lines were similarly plastic for acclimation following previous exposure(s) to a high temperature. Significantly more males survived the heat stress than females, and, within each sex, larger flies were generally more heat resistant than smaller ones. Additionally, the lines from the population that naturally encounters the highest temperatures were generally more resistant to high temperature stress.
83 citations
TL;DR: It is proposed that marine animals utilize all these regions in a manner similar to the Bay of Fundy estuaries and properly designed surveys will reveal their presence and introduction of tidal turbines into open ocean current systems will cause widespread impact on marine populations resulting in significant declines in abundance.
Abstract: Macrotidal estuaries of the inner Bay of Fundy are utilized by large numbers of migratory fishes, particularly dogfish, sturgeon, herring, shad, Atlantic salmon and striped bass as well as by other migratory marine animals, many of which have large body sizes (squid, Lamnid sharks, seals and whales). Tagging experiments indicate the fishes originate from stocks derived over the entire North American Atlantic coast from Florida to Labrador. Population estimates suggest up to 2.0 times 106adult American shad (Alosa sapidissima) migrate through an individual embayment each year. These migrations are an integral part of the life history of the respective species and appear to be controlled in part by the near shore movements of ocean currents. In other regions of the world similar macrotidal estuaries exist (Cook Inlet, Alaska; Severn Estuary, U.K.) and they, like the Bay of Fundy, are linked in continuum to the local ocean currents. We propose that marine animals utilize all these regions in a manner similar to the Bay of Fundy estuaries and properly designed surveys will reveal their presence. Fish passage studies utilizing the Annapolis estuary low-head, tidal turbine on the Bay of Fundy have shown that turbine related mortality of 20–80% per passage occurs depending on fish species, fish size and the efficiency of turbine operation. We suggest that introduction of tidal turbines into open ocean current systems will cause widespread impact on marine populations resulting in significant declines in abundance.
82 citations
TL;DR: A comparative analysis of floral morphology showed that D. verticillatus is not unusual in terms of the precision and reciprocity of organ positioning compared with 13 other tristylous species.
Abstract: Heterostyly typically involves reciprocal polymorphism in stamen and style lengths, physiological self- and intramorph-incompatibility, and a set of associated polymorphisms of pollen and stigma characters. This study examined floral morphology and compatibility relationships in the monotypic, herbaceous perennial Decodon verticillatus (Lythraceae). There have been conflicting reports on the occurrence of tristyly in the species, probably because of frequent loss of style morphs from populations in parts of the species' range. Floral morphology was examined using material collected from natural populations throughout the range. Detailed floral measurements revealed discrete trimorphism in style length and anther positioning in three populations. Data from two dimorphic populations showed similar patterns of floral polymorphism, except that both were missing the mid-styled morph. In one dimorphic population, there was evidence for modification in the length of mid-level stamens. Measurements in three populations indicated pronounced floral variability, including high frequencies of modified phenotypes with reduced stigma anther separation. Pollen size was only weakly differentiated among anther levels, and there were no differences in pollen production among anther levels or morphs. In contrast, stigma size and papilla length showed a strong negative correlation with style length; a pattern opposite to most heterostylous species. Experimental crosses performed under glasshouse conditions on plants from two populations showed a high degree of both self- and intramorph-compatibility. A comparative analysis of floral morphology showed that D. verticillatus is not unusual in terms of the precision and reciprocity of organ positioning compared with 13 other tristylous species.
73 citations
TL;DR: Estimates of reproductive fitness based on only a single breeding season's data can be seriously inaccurate, and should temporal changes in paternity be shown to be common phenomena in other species, then such results would have major implications for the interpretation of parentage studies.
Abstract: Using DNA fingerprinting we estimated the reproductive success of 49 adult birds belonging to 16 breeding groups of the sexually monomorphic brown skua ( Catharacta lonnbergi ) from the Chatham Islands (New Zealand). This population has a variable mating system, breeding in both monogamous and polyandrous groups. The parentage of 45 chicks produced over three breeding seasons was unequivocally determined using the multilocus probes 33.15 and 33.6. We found no evidence of either extra-pair or extra-group fertilization and there was no evidence to suggest egg dumping by females in any breeding group. Consequently, in the case of pairs, parentage of all chicks was assigned to the resident adult birds. In addition, band sharing analysis indicated that members of communal groups were not close relatives. In the 10 communally breeding groups examined, multiple paternity within a clutch was recorded on two of the 12 occasions in which two chicks were reared. Analysis of the parentage of offspring belonging to different groups, from different years, demonstrated that the number of chicks produced by some adult males varied considerably between seasons. In contrast, the reproductive success of other individuals was constant; for example, one male produced two chicks in each of the three seasons it was studied, while other males in communal groups did not produce any chicks during the course of this study. Fitness is a lifetime parameter, and any assessment of it requires studies over at least the average lifetime of an individual. The findings presented in this study suggest that, for brown skuas, there are significant differences in the reproductive success of some adult males in different breeding seasons. These results indicate that estimates of reproductive fitness based on only a single breeding season's data can be seriously inaccurate. Should temporal changes in paternity (and/or maternity) be shown to be common phenomena in other species, then such results would have major implications for the interpretation of parentage studies.
65 citations
TL;DR: It is argued that the absence of a high degree of niche specialization could favour successful biological control, as the agent would be capable of inflicting damage over a wider range of resource gradients.
Abstract: Thistles of the genus Onopordum (Asteraceae: Cardueae) have become serious weed problems in parts of Australia and North America following introduction from their native Eurasian ranges, and are the target of a biological control programme in Australia. This paper analyses the results of three separate surveys of insects feeding and breeding on thistles of the genus Onopordum in the Mediterranean region. Of the 129 species found feeding, 74 species also bred on these thistles. Endophages comprised 54% of the breeding insects, with species that fed in the capitula and within the rosette crown/root area predominating. The Coleoptera and Hemiptera were the dominant endophage and ectophage taxa, respectively. Differences in the Onopordum fauna were noted between host species and between geographic regions, but this was largely due to the generalist component of the fauna. Onopordum specialists showed little variability across regions or between different species within the host genus. On comparing the fauna of Onopordum with that of other thistle genera, it was suggested that plant-herbivore interactions between Onopordum and its fauna are less highly evolved, in that there is less host specialization and a lesser degree of niche partitioning. This appears to be related to the low rate of speciation and habitat specialization within the host genus itself. The potential of certain genus-specific insects as biological control agents for Onopordum spp. is discussed. It is argued that the absence of a high degree of niche specialization could favour successful biological control, as the agent would be capable of inflicting damage over a wider range of resource gradients.
60 citations
TL;DR: The results of a comparison between two colour measurement techniques: Munsell colour standard matching and spectroradiometry provided a better estimate of the role of secondary sexual characters in male mating success.
Abstract: Objective and reliable assessment of animal colouration is of great value to workers in the biological sciences. We present the results of a comparison between two colour measurement techniques: Munsell colour standard matching and spectroradiometry. As part of ongoing research on sexual selection in red jungle fowl ( Gallus gallus ), feather and comb colour of 49 roosters was measured using both techniques. Previous research showed that hens use variation in feather and comb colour in mate choice, and we allowed hens to choose between paired roosters. Colour matching and spectroradiometry scores were generally correlated, but spectroradiometry was more sensitive in detecting variation and also provided a better estimate of the role of secondary sexual characters in male mating success.
TL;DR: Amphistomaty tends to occur in species where CO2 may be limiting photosynthesis (unshaded environments), or where there are structures to prevent water loss from the leaf (e.g. hairs).
Abstract: The distribution of stomata over both leaf surfaces may affect both the photosynthetic rate and water use efficiency of species, implying that species with different photosynthetic and water requirements may also have different stomatal distributions. A database containing data on the distribution of stomata on the leaves of 469 British plant species was used to look for relationships between stomatal distribution (including both location on the leaf and density) and both habitat and morphological variables. Statistical models were applied to the data that minimized any effects that phylogenetic constraints may have had on the data. Hypostomaty is common in woody species, species which typically occur in shaded habitats and species with large or glabrous leaves. Amphistomaty, however, predominates in species which occur in non-shaded habitats, species with small, dissected or hairy leaves, and in annual species. Amphistomaty, therefore, tends to occur in species where CO2 may be limiting photosynthesis (unshaded environments), or where there are structures to prevent water loss from the leaf (e.g. hairs). Hypostomaty, however, occurs in slow-growing species (e.g. trees), species with leaves which have large boundary layers (large or entire leaves) and in species where CO2 is unlikely to limit photosynthesis (shaded habitats).
TL;DR: A very distant relationship between T. elegans and T. errans, non-monophyly of the elegans group, and nesting of the form validus (previously considered a member of the genus Nerodia ) within Thamnophis are among the conclusions in conflict with previous views.
Abstract: We estimated phylogenetic relationships among 26 species of garter snakes (genus Thamnophis ) using allozyme and mitochondrial cytochrome b gene nucleotide sequence variation. Parsimony analyses of the two data sets give substantially different estimates of phylogeny. Several lines of evidence indicate that much of this conflict is due to error associated with the restricted number of characters in each data set. Such sampling error may be reduced by combining all the characters; we therefore present all estimate of phylogeny based on parsimony analysis of all the data combined. All our analyses support several conclusions in conflict with previous views: a very distant relationship between T. errans and T. elegans, non-monophyly of the elegans group (even excluding T. errans ), and nesting of the form validus (previously considered a member of the genus Nerodia ) within Thamnophis. The combined analysis gives an almost fully resolved tree. However, bootstrapping indicates only weak support for many clades in this tree. Furthermore, paraphyly of the assemblages of cytochrome b gene lineages within T. elegans and T. radix indicate the potential for discordance between the mitochondrial DNA (mtDNA) and species phylogenies through the sorting of ancestral mtDNA polymorphisms. These problems suggest the need for assaying additional characters, especially ones likely to be independent of those used in the present study.
TL;DR: Electrophoretic data and comparative species distributions suggest that Podarcis sicula recently colonized the Aeolian Islands, and it has competed successfully with P. raffonei in this area, greatly reducing the range of the latter and causing the extinction of most of its populations.
Abstract: The electrophoretic variation at 26 presumptive gene loci was investigated in populations of Podarcis wagleriana from Sicily, the Aegadian Islands, and the Aeolian Islands. For interspecific comparison, samples of the closely related lizard P. sicula from the same geographic area were also used. Population heterogeneity analyses carried out by the estimation of F -statistics and Nei's standard genetic distance, showed a high genetic homogeneity within P. sicula , but a noticeable genetic differentiation within P. wagleriana . In the latter species, Nei's D ranged from 0 to 0.212, and this is because the Aeolian populations were quite distinct from those inhabiting Sicily and the Aegadian Islands. Fixed differences identified at three loci ( Ck, Ada, Gp-4 ) contributed to a relatively high value of Nei's standard genetic distance between the two population groups ( D = 0.147). This value is very similar to those found comparing pairs of well-recognized biological species included in the genera Podarcis and Lacerta . Estimation of the time of evolutionary divergence shows that the Aeolian and Sicilian populations of P. wagleriana have been isolated geographically for a long time (0.7 Myr according to Nei's formula; 2 Myr according to Sarich's calibration), indicating evolutionary divergence at the species level. Based on genetic and biogeographic data, it is suggested the recognition of full specific status for the Aeolian populations, for which the name P. raffonei comb. nova (Aeolian wall lizard) is proposed. Electrophoretic data and comparative species distributions suggest that (1) Podarcis sicula recently colonized the Aeolian Islands, and (2) it has competed successfully with P. raffonei in this area, greatly reducing the range of the latter and causing the extinction of most of its populations. In fact, P. sicula is widespread in the Aeolian Archipelago, while P. raffonei is confined at present to one large island (Vulcano) and three tiny islands (Strombolicchio, Scoglio Faraglione, La Canna). This can be considered a classic example of competitive exclusion of a native form ( P. raffonei ) by a species accidentally introduced by man ( P. sicula ).
TL;DR: Lake Thingvallavatn supports four trophic morphs of Arctic charr, Salvelinus alpinus; two of the morphs are benthic (small and large benthivorous charr) one exploits pelagic waters (planktivorousCharr) and the fourth is found in both habitats (piscivorous Charr); the morphological variation was analysed by use of principal component analysis and canonical discriminant analysis.
Abstract: Lake Thingvallavatn supports four trophic morphs of Arctic charr, Salvelinus alpinus (L.); two of the morphs are benthic (small and large benthivorous charr) one exploits pelagic waters (planktivorous charr) and the fourth is found in both habitats (piscivorous charr). The morphological variation among these morphs was analysed by use of principal component analysis and canonical discriminant analysis. The benthic morphs have a short lower jaw and long pectoral fins. The benthic fish also have fewer gillrakers than the other morphs. Small and large benthivorous charrs attain sexual maturity from 2 and 6 years of age, and at fork lengths from 7 and 22 cm, respectively. Small benthivorous charr retain their juvenile parr marks as adults, have beige ventral colours, and are frequently melanized under the lower jaw. Planktivorous and piscivorous charr attain sexual maturity from 4 and 6 years of age, from fork lengths of 15 and 23 cm, respectively. This phenotypic polymorphism is associated with habitat utilization and diet of the fish, and has probably arisen within the lake system through diversification and niche specialization. The pelagic morphs apparently stem from a single population, and are possibly diversified through conditional niche shifts which affect ontogeny. Juveniles reaching a body length of 23 cm may change from zooplankton to fish feeding. Asymptotic length increases thereby from 20.5 cm in planktivorous charr to 30.2 cm in piscivorous charr. The benthic morphs appear to represent separate populations, although both feed chiefly on the gastropod Lymnaea peregra. Their co-existence seems to be facilitated by size dependent constraints on habitat use. The small morph (asymptotic length 13.3 cm) exploit the interstitial crevices in the lava block substratum, whereas the large morph (asymptotic length 55.4 cm) live epibenthically.
TL;DR: Despite large differences in the mass of the spermatophore, its main function seems to be to ensure sperm transfer, which can be concluded from the similarity between the duration of sperm transfer and the time period necessary for sperMatophore consumption in each of the subspecies.
Abstract: To analyse spcrmatophore function, various aspects of the mating behaviour (e.g. spermatophore mass, duration of sperm transfer, mating frequency) were compared in two subspecies of the bushcricket P. veluchianus. Body mass was significantly different in both subspecies and had a strong effect on spermatophore mass, resulting in a large difference in absolute and relative (percentage of male body mass) spermatophore mass in both subspecies. After copulation the small P. v. minor spermatophores were consumed much faster by the female than the larger ones of P. v. veluchianus. The time necessary for sperm transfer from the spermatophore to the female spermatheca was much shorter in the subspecies with small spermatophores than in that with large spermatophores, and in both subspecies similar to the time required to consume the spermatophores. Mating frequency varied also between the subspecies and was murh higher in P. v. minor than in P. v. veluchianus. Differences in body mass between the two subspecies therefore resulted in changes in several aspects of mating behaviour. However, despite large differences in the mass of the spermatophore, its main function seems to be to ensure sperm transfer. This can be concluded from the similarity between the duration of sperm transfer and the time period necessary for spermatophore consumption in each of the subspecies. The spermatophore is thus considered to be male mating effort.
TL;DR: The Ranee basin is the only site where a full-scale evaluation of the ecological impact of a tidal power scheme, after 20 years of operation, has been made and the new ecological equilibrium established remains fragile and depends to a large extent on the operating conditions of the power station.
Abstract: The Ranee basin, on the northern coast of Brittany, is the only site where a full-scale evaluation of the ecological impact of a tidal power scheme, after 20 years of operation, has been made. The isolation of the estuary, during the construction phase, was particularly damaging to the environment. Gradually, after the scheme was put into service, an increasingly diverse flora and fauna became established. The patterns of distribution of this flora and fauna, their groupings into ecological units and the nature of their interrelationships, indicate a variable degree of biological adjustment to the new environmental conditions. Migratory organisms are able to pass via sluice gates and turbines. However, the new ecological equilibrium, established in the space of 10 years, remains fragile and, being linked to the degree of stability of abiotic conditions, depends to a large extent on the operating conditions of the power station.
TL;DR: Experiments were carried out on garden lawns in England in which four types of green pastry prey were exposed to predation by wild birds, demonstrating the survival value of countershading.
Abstract: Experiments were carried out on garden lawns in England in which four types of green pastry prey were exposed to predation by wild birds. The prey were dark green, light green, countershaded (dark green above, light green below) and reverse shaded (i.e. identical to countershaded but laid out upside-down). Birds took significantly fewer countershaded prey than any of the other types thereby demonstrating the survival value of countershading.
TL;DR: The metapopulation of Littorina mariae that was studied was divided into semi-isolated populations, between which the average rate of migration was in the range of a few individuals per generation.
Abstract: The marine snail Littorina mariae Sacchi & Rastelli occurs in high numbers in the littoral zone on fucoid macro-algae. The eggs are laid on the seaweed and development to miniature snails takes place without any pelagic larval stage. We have mapped the genetic variation of 30 enzyme loci in populations from eight small islands within 15 km of each other on the Swedish west coast. The original intention was to investigate the magnitude of gene flow within and between islands. However, we soon realized that our basic assumption of neutral genetic variation was forcefully violated in at least one locus, arginine kinase (Ark). Allele frequencies of Ark were strongly associated with type of habitat. Therefore the main part of this study focused on allele frequency distribution in different habitats. Eight of the 30 loci screened were polymorphic but we mainly considered the four most polymorphic ones (total heterozygosity between 0.32 and 0.57). All four showed significant heterogeneity between subpopulations, Ark especially so; 42% of the total variation of Ark was explained by differentiation between samples, and 90% of this variation was attributed to differences between different types of habitats (more or less exposed to wave action). In contrast, peptidase (Pep-1) and phosphoglucomutase (Pgm-2) varied in a way predicted by neutral theory; between sample variation being mainly attributed to differentiation between islands. The variation in phosphoglucose isomerase (Pgi) was less consistent. In some islands there was an obvious difference between different habitats, but on other islands we found no significant difference. Not taking into account the extreme, presumably selected, variation in Ark, we concluded that the metapopulation of Littorina mariae that we studied was divided into semi-isolated populations, between which the average rate of migration was in the range of a few individuals per generation.
TL;DR: Analyses of Euphilotes populations using biochemical, morphological, and life history characters, do not support either coevolution or sequential evolution with Eriogonum but are more consistent with opportunistic adaptation to new hosts having different bloom periods.
Abstract: The lycaenid butterfly genus Euphilotes, consisting of five species and several dozen subspecies, is confined to western North America. Each subspecies utilizes one or a few species of Eriogonum (Polygonaceae) as larval hosts; larvae feed entirely on pollen and developing seeds. Euphilotes populations are (with few exceptions) univoltine and fly in synchrony with the initial (c. 2 weeks) annual flowering periods of their hosts. Euphilotes evolution coincides with shifts to new hosts, frequently with different bloom periods. Often both inter- and intraspecific populations occur in sympatry. Although interspecific populations may fly in synchrony and utilize the same hosts, sympatric intraspecific populations use different hosts and generally fly allochronically. Analyses of Euphilotes populations using biochemical, morphological, and life history characters, do not support either coevolution or sequential evolution with Eriogonum but are more consistent with opportunistic adaptation to new hosts having different bloom periods.
TL;DR: Congruent relationships among taxa were obtained from allozymes and male genital morphometries, suggesting that divergence in genital morphology is a fairly good marker of the overall genetic divergence.
Abstract: The difficult and controversial attribution of Hipparchia (Parahipparchia) populations to species or subspecies rank led us to use a comparative, quantitative approach to clarify evolutionary and taxonomic relationships among taxa Seventeen populations from the Mediterranean area belonging to nine presumptive species or subspecies were sampled, and multivariate analyses were employed to study three character sets: allozymes, morphometric profiles of male genitalia, and quantitative descriptors of wing pattern and shape Comparative analyses of distance matrices, trees and ordination patterns enabled us to outline evolutionary relationships among taxa and to assess the relative value of each character set Congruent relationships among taxa were obtained from allozymes and male genital morphometries, suggesting that divergence in genital morphology is a fairly good marker of the overall genetic divergence On the other hand, discordant results from wing pattern descriptors suggest these might be subjected to different evolutionary trajectories and rates because of their particular adaptive significance, and might not represent reliable tracers of phylogeny
TL;DR: Despite the high levels of homoplasy, the most-parsimonious trees require fewer changes than had been previously suggested for evolutionary trends in several characters; some cassiduloid families can not be separated, and support the reassignment of several genera.
Abstract: The Neognathostomata (comprising the orders Clypeasteroida, Oligopygoida, Neolampadoida, and the paraphyletic Cassiduloida) form one of the three major clades of irregular echinoids. Despite the group's apparent success since the Jurassic and impressive peak diversity in the mid-Cretaceous, most included clades are now severely reduced. A phylogeny is essential for reconstructing the taxonomic, environmental and biogeographic patterns of this decline, and understanding the causal processes responsible for them. I examined the distribution of qualitative morphological characters (including those defining genera) for 97 species from 77 non-clypeasteroid genera and the three clypeasteroid suborders. Following preliminary analyses, I reduced the data to 40 characters (having 60 apomorphic states) and 71 representative genera. Goloboff's data decisiveness, the skewness of tree length distributions, and permutation tests all reveal significant phylogenetic structure in the data. Heuristic searches conducted with PAUP found more than 72 500 trees of 217 steps (CI = 0.276), but only the first 30,000 were evaluated. These exhibit considerable instability in the relationships among taxa. Successive approximations weightings did not reduce the numbers of favoured trees. Analyses using only less homoplasious characters failed to improve the resolution. Fisher's stratigraphic debt provides an objective means of selecting a very few of the morphologically most-parsimonious trees. Most nodes are supported by only one to three character changes, and these are generally reversed or paralleled elsewhere. The results suggest some cassiduloid families can not be separated, and support the reassignment of several genera. Despite the high levels of homoplasy, the most-parsimonious trees require fewer changes than had been previously suggested for evolutionary trends in several characters. Whether the rampant homoplasy present in the data reflects incorrect character analysis, limited structural or developmental options, or the effects of parallel selection, its presence raises severe obstacles to phylogenetic analyses.
TL;DR: Using population age structures and sex ratios, the patterns of seasonal migration and recruitment are discussed and annual patterns of abundance at Hinkley Point Power Station are examined.
Abstract: Mysids and caridean decapods are a significant proportion of the biomass within the Bristol Channel and Severn Estuary and key members of the marine food web in this estuarine system. Annual patterns of abundance at Hinkley Point Power Station of the mysids Praunus flexuosus, Schistomysis spiritus, Noemysis integer, Mesopodopsis slabberi and Gastrosaccus spinifer and of the carideans Pasiphaea sivado, Palaemon serratus, Pandalus montagui, Crangon crangon and C. allmani are examined. Using population age structures and sex ratios, the patterns of seasonal migration and recruitment are discussed.
TL;DR: The authors' analyses show a concentration of transitions to polygamy and short bonds, respectively, in the two monophyletic groups of Struthionidae-Anatidae and Pteroclidae-Laridae, whereas non-passerines are extensively analysed, whereas a survey of the situation in passerines is given.
Abstract: A phylogenetic analysis of the evolution of mating systems in birds was made, based on the phylogeny of Sibley and Ahlquist. Both the mating behaviour and the social behaviour of species were classified for males and females, according to (1) the frequency of mated individuals in a species having several mates in a breeding season compared to those having one mate (the mating pattern), and (2) whether there is a bond between males and females, and in case of there being a bond, to the length of the bond. Non-passerines are extensively analysed, whereas we only give a survey of the situation in passerines. In non-passerine birds, the number of inferred transitions from monogamy to polygamy are 15 for females and 16–23 for males. Almost all transitions between different states of mating pattern are to higher states of polygamy. Our analyses also show a concentration of transitions to polygamy and short bonds, respectively, in the two monophyletic groups of Struthionidae-Anatidae and Pteroclidae-Laridae.
TL;DR: Gobies of a fluviatile morph with large eggs as well as three other amphidromous morphs with small eggs, inhabiting a single stream sympatrically in Okinawa, showed that each morph was separated by a fixed-allele difference for at least one locus, indicating that the four morphs which occurred symp atrically are reproductively isolated from each other.
Abstract: Many colour morphs have been recognized in the Rhinogobius brunneus complex. A recent electrophoretic study has revealed that some of the colour morphs are well differentiated from each other genetically. In Okinawa, egg-size and life-history variation has been found in addition to the colour variation in this species complex. To clarify the nature of this life-history variation, gobies of a fluviatile morph with large eggs as well as three other amphidromous morphs with small eggs, inhabiting a single stream sympatrically in Okinawa, were analysed by electrophoresis and the females were also used for comparison of egg and clutch sizes. Electrophoretic data for 34 loci showed that each morph was separated by a fixed-allele difference for at least one locus, indicating that the four morphs which occurred sympatrically are reproductively isolated from each other. However, Nei's genetic distance between the fluviatile morph and one of the ampbidromous morphs was much smaller (0.026) than distances among amphidromous gobies (0.323-0.480). Egg size of the former was by far the largest among the four. These results imply that speciation of the fluviatile morph accompanied by the egg-size increase has been completed rapidly without considerable genetic differentiation.
TL;DR: It is argued that reinforcement is more likely to occur in sympatrically diverging populations, like host races of phytophagous insects, where different populations come into contact after diverging in allopatry.
Abstract: Speciation by reinforcement, the process by which characters that increase assortative mating will be favoured because of selection against the production of less fit hybrids, is a much criticized evolutionary scenario, supported by little evidence. Previous studies have focused on hybrid zones, i.e. where different populations come into contact after diverging in allopatry, which might not be the optimal situation in which to look for reinforcement. We argue that reinforcement is more likely to occur in sympatrically diverging populations, like host races of phytophagous insects. In an attempt to demonstrate this we studied mate recognition of different life cycle forms, host races, sister species and more distantly related species of the aphid Cryptomyzus . All but one of these taxa mate on the same host plant, thus their mate recognition is subjected to similar ecological conditions, i.e. extrinsic selection pressures. The males of the life cycle forms and host races were not differentially attracted in an olfactometer by their respective females, which all released sex pheromones during the same period of the day. The females of the sister species, however, released sex pheromones at different times of the day, one 'calling' in the morning and the other in the afternoon. This difference is corroborated by a corresponding pattern of activity in the males, and a marked preference of the males for conspecific pheromone. It is argued that these sister species originated sympatrically following a shift in summer host plant utilization. As their hybrids are less viable than the Fl of intraspecific crosses reinforcement might have been a major force in the development of specific mate recognition, i.e. the specificity and difference in the daily cycle of release of the sex pheromones.
TL;DR: Geographical variation in allozyme frequencies among 24 populations of the butterfly Parnassius mnemosyne in southern France was studied by enzyme electrophoresis.
Abstract: Geographical variation in allozyme frequencies among 24 populations of the butterfly Parnassius mnemosyne in southern France was studied by enzyme electrophoresis. Clustering procedures were used to define the geographical organization of genetic variation and an analysis of genetic differentiation was performed to test the degree of potential gene flow between the colonies using the methodologies derived from F-statistics and the private alleles model. Further, an approach using reduced space ordinations (factorial analysis of correspondences and discriminant analysis), was used to allow the visualization of genetically intermediate populations and to determine the roles of individual alleles at various levels of geographical structure. In P. mnemosyne, the effect of both isolation by distance and geographical barriers upon gene flow is complex. Some barriers appear to be very efficient, but others, at least as strong geographically, do not act in such a way. Multivariate analyses underlined the progressive transition between some groups while in other instances, a sharp cut was observed without obvious topographical barriers. Ecogeographical data and historical events (such as colonization processes) should probably be taken into account in order to explain the geographical variation of genetic structure.
TL;DR: Three small, naturally isolated populations of Asplenium septentrionale were investigated in the Swiss lowlands north of the Alps and it is assumed that the extinction rate of the populations is very low.
Abstract: Three small, naturally isolated populations of Asplenium septentrionale were investigated. The plants grow on erratic boulders in the Swiss lowlands north of the Alps. The distance to the main distribution area is about 40 km. The three populations can be separated from each other by at least one different isozyme phenotype. Two populations do not show any variability among individuals. The third, however, contains four different phenotypes. Different hypotheses are discussed to explain the establishment of the habitat and the fate of the populations. Predictions from metapopulation theory are compared with our results. According to theory we assume that the extinction rate of the populations is very low. Our results from naturally small and isolated populations are considered to be important in the context of conservation biology.
TL;DR: This study provides direct evidence that evolutionary generalization must be rooted in the branching pattern of phylogeny and not the potentially arbitrary categorical ranks of traditional taxonomies, and supports recent calls for a truly phylogenetic taxonomy that has as its philosophical core the concept of descent.
Abstract: Evolutionary taxonomy has all but succumbed to cladistic methodology, but it continues to exert considerable influence in the realm of higher classification. Some systematists accept cladistic methods in phylogeny inference, but allow paraphyly in formal classifications. Most important, however, many traditional classifications based on paraphyletic groups (e.g. 'Reptilia') remain in force, deeply entrenched in the literature. Cladists have argued that such paraphyletic classifications can mislead comparative biologists into false evolutionary generalizations, but this assertion has rarely, if ever, been supported by example. This paper provides a case study, illustrating in detail the influence of a traditional paraphyletic classification of squamate reptiles on the historical development of ideas regarding the evolution of sensory modes (chemoreception vs. vision) in the group. The paraphyletic classification is shown to have led to false generalizations and incorrect conclusions stemming directly from the fact that the classification did not reflect accurately the phylogeny of Squamata, particularly the cladistic relationships of Gekkota. This study provides direct evidence that evolutionary generalization must be rooted in the branching pattern of phylogeny and not the potentially arbitrary categorical ranks of traditional taxonomies. It further supports recent calls for a truly phylogenetic taxonomy that has as its philosophical core the concept of descent.
TL;DR: Analysis of population variability suggests that the high levels of heterozygosity observed can be explained by the population structure, and are within the range of expected values if bottlenecks have occurred in the recent history of the Corrientes group.
Abstract: Genetic variability measured by allozymic electrophoresis has been studied in several species of the subterranean rodent genus Ctenomys (Octodontidae). The study was carried out with the main purpose of analysing a special group known as the 'Corrientes group' which inhabits the province of Corrientes in Argentina. The members of the group are, with high probability, isolated reproductively due to their karyotypic differences (diploid numbers are between 49 and 70). To evaluate whether the chromosomal differences were the causes of speciation or if they arose a posteriori, we compared the level of the genetic distance among taxa within the Corrientes group with all those measured between intraspecific populations in Ctenomys. The results indicate that the distances among the populations of the Corrientes group are at or below the level of those measured among intraspecific populations in Ctenomys. Thus, it is unlikely that genetic differentiation triggered speciation. It is shown that this low level of genetic differentiation is not in contradiction with the high levels expected for species originating from one of the possible mechanisms of chromosomal speciation named, chromosomal transilience. Although for geographical reasons it seems obvious that gene flow is precluded among the members of the Corrientes group, the Slatkin method for estimating Nm values was also used. Because high values of Nm exist but no isolation by distance could be detected, it is suggested that reproductive and geographical isolation are very recent. Finally, analysis of population variability suggests that the high levels of heterozygosity observed (a) can be explained by the population structure, and (b) are within the range of expected values if bottlenecks have occurred in the recent history of the Corrientes group. As a general conclusion, the results indicate that in the Corrientes group the genetic data support a putative causal role for chromosomes in speciation.